By: Knut Nordby


Being myself a vision scientist who is also a complete achromat, I have, upon demand from friends and collaborators, taken on the task of trying to convey some of my visual experiences and to explain how I cope with my visual handicap. I rely on recollections, both my own and those of my family, and try to separate information that can be documented or is supported by other sources from the mere anecdotal. I also draw on information from interviews with other achromats, but only to supplement or comment on my personal experiences.

My recollections may have become distorted over time, they may not be precise and may also be biased - and they may not, in all cases, apply to other achromats. It is my hope, though, that my account will give both vision scientists and the general reader a glimpse, not only into the manifestations of achromatopsia and rod-vision - topics usually not covered by the learned papers - but also into the practical problems and obstacles encountered by a completely colour-blind person.



I was born on November the llth, 1942, in Oslo, Norway, as the first child of Kjell Nordby (28.11. 1914 - 30.3.1987) and Mary Camilla Nordby, nee Bredes,en, (born 21.12.1914). The pregnancy was normal and the birth went well. My birth-weight was 3845 g and my length 510 mm. There is some early written and photographic documentation showing that, on the whole, I was a healthy baby who seems to have developed normally and, except for a stenosis of the pylorus which was quickly cured, I gave my parents little cause for alarm during the first six months of my life.

Both my parents were born with normal vision and, indeed, excellent colour-vision. I tested both with the Ishihara and the ™sterberg pseudo-isochromatic plate tests, and I also tested my father with the Farnsworth 100 Hue test. They both performed normally. I have one sister (born 8.10.1943) and one brother (born 5.10.1945) who are both, hke myself, typical, complete achromats, confirmed by the anomaloscope.

There is no evidence of consanguinity between my parents, although the possibility cannot entirely be ruled out. My paternal and my maternal grandmother both came from the same small coastal town in southern Norway, but nothing is known with certainty about any relationship between the families. If there is any relationship, it must be at least four generations removed (see Fig. 1).

The prevailing view, then and now, is that typical, total achromatopsia with reduced visual acuity is a recessive, autosomal (i.e. not linked to the pair of X-Y- or sex-chromosomes) inherited condition. The statistical probability, according to Mendelian laws of inheritance, of all three siblings inheriting and displaying a recessive trait from parents who do not exhibit the phenotype is exceedingly small. On the average, and assuming that only one gene is responsible, only one child out of four from heterozygous parents will be homozygous for and display a recessively inherited trait.

No documented case of achromatopsia is known to have existed in either branch of my family. There are, however, rumours of an aunt of my materna grandmother who, reportedly, had "very weak eyes" and "rarely ventured out-of-doors in full daylight. Despite the suggestive symptoms, such „necdotal evidence cannot be accepted to infer a bona fide case of achromatopsia, since no ophthalmological report is known (it is most improbable that any medical assessment of her eyes was ever performed), and her symptoms can be attributed to several other causes (e.g. retinitis pigmentosa from diabetes).

According to my parents, I could control my eyes and direct my gaze even at the age of three weeks. Photographs taken of me only a few weeks after birth show me with fully open eyes and not a trace of squinting, or partial closing of the eyes, in bright light (see Fig. 2). Nothing unusual was recorded at the time about my visual behaviour (i.e. light aversion or "photophobia') or eye-movements (i.e. nystagmus) .

Due to enemy actions in Norway, my parents fled with me to Sweden in May 1943, when I was only 6 months old. One to two months later my parents began noticing that I had developed some strange symptoms. My eyes had started to quiver from side to side (i.e. horizontal, pendular nystagmus) and my eye-movements were irregul„r. I had begun to blink continuously and partially close my eyes, or squint (looking through the narrow slits between the eyelids), in bright light, and I habitually avo"ided bright light, something I had not done before. Earlier, according to my mother, I had sometimes even looked straight into the sun with no signs of distress, and she often had to turn me around, being worried that I would damage my eyes. This special behaviour has also been reported to me spontaneously by the mothers of several other achromats. One mother, in fact, believed that this habit of gazing into the sun had harmed her son's eyes and was the actual cause of his achromatopsia and low visual acuity.

After seeing several general practitioners and some ophthalmologists, who could offer no explanation for the symptoms, my parents finally consulted a prestigious professor in ophthalmology (no-one in the family can now recall his name). Hereditary achromatopsia totalis [i.e. total colour-blindnessl with concomitant horizontal pendular nystagmus, light aversion, and reduced visual acuity was diagnosed. He also found that I was hypermetropic with a slight astigmatism. At an age of only nine months I thus received my very first pair of spectacles. As far as can now be established these first lenses had a strength of about +3 diopters and had a 1 diopter vertical cylinder.

My parents were told that I was severely visually handicapped, that I was totally colour-blind and that my visual acuity was so low that I would never be able to read and write. They were also told that I would have to attend institutions for the blind and learn to read Braille, and, at best, could be trained for one of the traditional vocations for the blind (e.g. piano tuner, Telephone switch-board operator, etc.). As it happens, the authority was disproved in some of his predictions by the course of events, but I am getting ahead of myself

After hostilities ended my parents deeided to stay in Sweden. Because of my father's work we moved many times; living in Stockholm, in Gothenburg, in the small town T”reboda and again in Stockholm; until the summer of 1954, when his work took us to Caracas, Venezuela. There we stayed four years, until the summer of 1958, after which we returned to Norway and settled in Oslo.

Early childhood.

My first clear memories seem all to be connected with nights and evenings, or they occur indoors in subdued lighting. As far back as I can remember, I have always avoided bright light and dir'ect sunlight as much as possible. Photographs taken of me, and my siblings, during our childhood normally show us with nearly shut eyes, usually looking away from the sun, except when photographers demanded that we look towards the sun for the pictures (see Fig. 3). As a child I preferred playing indoors with the curtains drawn, in cellars, attics and barns or outdoors when it was overcast, in the evenings, or at night.

This, of course, was quite the opposite of what wellmeaning parents and grown-ups considered to be right for children. My whole childhood was, in fact, a continuous struggle against the prevailing views about what, is proper for children, i.e. being out in the sunshine as much as possible, not playing outdoors after it is dark, not drawing the curtains during the day, not playing in cellars and other dark places, and so on.

It soon became apparent to my parents that the learned ophthalmologist was correct insofar as I was completely colour-blind. My father told me that he had noticed that when sorting my coloured playing blocks in day-light I usually put the red and the black blocks together in one pile, the green and the blue ones in another pile, the yellow were usually, but not always, put in a pile by themgelves, and so were the white. Indoors in artificial lighting, on the other hand, I sometimes separaten the red and the black in different piles, but frequently confused the green and the blue blocks; the yellow and the white blocks, though, I still put in separate piles.

When using colouring pencils or crayons, I am told, I always confused the colours, breaking all the conventions and "rules" about what were the "correct" colours to use: I would happily colour the sky light green, yellow or pink; the grass and leaves orange or dark blue; the sun white or light blue, and so on. I was always corrected in my choice of colours by those who knew better, and, eventually, I gave up painting and colouring my drawings. Unfortunately no coloured drawings from my early childhood seem to have survived.

When I was five we were living in Gothenburg, and from then on my recollections are much clearer. At this time my circle of activity expanded beyond the limits of the house and the garden and into the near parts of the town. I then developed a system for finding my way back, which I still use. The city-block was the basic unit in my system. I always kept myself orientated where I was on the block. When going further away the system consisted of counting the streets I had crossed, keeping count of right and left turns, counting doors or shops along a block, thus forming a mental, topological map of my path. When returning I reversed direction, retracing my path, making turns in the opposite direction, and counting backwards the streets I had crossed.

I also learned to make use of various prominent landmarks, e.g. parks, squares, churches, towers, underpasses, bridges, etc., as important checkpoints along the route. Even today, I find it much easier to orientate myself in cities with rivers, canals, tramways, overground railway lines and other conspicu-ous and easily identifiable "boundaries" that divide the city into smaller parts. I cannot remember ever having lost my way returning from a place I had first located myself. On the other hand, it can be more difficult when going with others to keep track of the route, especially when travelling by car.

When five, I nearly fooled my parents into believing that I could read. My parents often read stories and fairy tales to us children, and I was very much intrigued by this activity. I had a children's picture book with a few lines of narrative on each page, all of which I had learned by heart. Sitting with the book at normal reading distance, where,'of course, I could not discern the individual letters i "read' the text out loud and clear, following the lines with my eyes, turning the pages at the right points. Eventually, I was found out when, by mistake, I turned two pages at a time and continued to read on before realizing my error. This desire to master the art of reading never left me.


When the time came for me to start school we lived in the small village of T”reboda, about halfway between Stockholm and Gothenburg. In Sweden it is compulsory to begin school in the year that children reach the age of seven. The nearest school for the blind and partially sighted was in Stockholm. My parents did not want to send me away to a boarding school at such a young age, and, in defiance of the professor's earlier advice, it was decided that I should try to attend an ordinary school and see if I could manage. Thus, in the autumn of 1948 I started out in the first form of the municipal, primary school in Töreboda.

At this time it became very obvious to me that my vision was different from that of other children. They could see things that I could not see; such as recognizing each other at a distance, spotting ripe berries on bushes and trees , reading cars' licence plates at a distance, etc. They could also take part in activities and sports, especially ball-games, that I could not. Hitting a ball with a bat, or catching a ball thrown towards me, was next to impossible for me, except under the most optimal light-conditions, such as in twilight; When teams were set up, I was always the last one to be taken on.

I must have been a difficult pupil, inquisitive about all that was going on, talkative, always avoiding doing things when my vision would prevent me from performing and thus give me away. I did learn the letters of the alphabet, but I did not really learn to read properly in the first and second form.

The school-books used had ordinary size print, and no-one had thought about getting me books with extra large print, if, indeed, such books existed then. Nor had anyone thought about providing me with a reading-glass. The lenses of my glasses, which by now had been increased in strength to about +6 diopters, did not have enough magnification power for me to read the small print easily.

Since I could actually not discern the inchvidual letters even in ordinary book-print, I again resorted to my old reading hoax; bringing it to new and un- precedented heights. I had developed a very keen memory, and it was usually enough if a class-mate or someone in the household read my home-assignment aloud to me once or twice, in order for me to remember and reproduce it, and to perform a rather convincing reading behaviour in class.

An important discovery that I made during my first school-year is worth noting. As an aid for teaching the letters of the alphabet, the teacher placed large cards, each holding a printed letter, in a row over the blackboard as the letters were introduced. To differentiale between the two categories of letters they had different colours; the vowels were red, while the consonants were black. I could not see any difference between them and could not understand what the teacher meant, until early one morning late in the autumn when the room-lights had been turned on, and, unexpectedly, I saw that some of the letters, i.e. the A E I O U Y Å Ä Ö, were now suddenly a darkish grey, while the others were still solid black. This experience taught me that colours may look different under different light-sources, and that the same colour can be matched to different grey-tones in different kinds of illum"ination. I have since often used this phenomenon of spectral differentiation as an aid to separate colours by their different grey-tones under various light-sources.

A constantly recurring harassment throughout my childhood, and later on too, was having to name colours on scarves, ties, plaid skirts, tartans and all kinds of multi-coloured pieces of clothing, for people who found my inability to do so rather amusing and quite entertaining. As a small child I could not easily escape these situations. As a pure defence measure, I always memorized the colours of my own clothes and of other things around me, and eventually I learned some of the "rules" for "correct' use of colours and the most probable colours of various things: As an example, I learned that glass that was very dark to me usually was a dark cobalt-blue, glass that looked a bit lighter was usually bottlegreen, and so on. In this way, I could fool some people into believing that I had colour-vision and stop them from pestering me. A friend of the family, though, actually believed that my inabihty to name colours came from my parents not having taken the trouble to teach me the colour-names. She often tried, but in vain, to train me in naming colours, but had to admit in the end that I could not, in fact, differentiate between the different colour h'ues.

When I was eight, my three year younger brother was given a small bicycle. This was quite irresistible to me and I soon learned to ride it. At first I only dared to go around the block, keeping to the left-hand side of the road and only making left turns (Sweden had left-hand drive at this time), but as I gained confidence my activity area expanded. Traffic in post-war Sweden was very light, in our village we scarcely saw more than a couple of cars a day, much Transport being carried out by horse and cart, and the conditions of the roads in the area did not allow speeding: Riding the bicycle in traffic did not, therefore, constitute too grave a danger to me, despite my visual handicap.

I often "borrowed' the bicycle, getting up early in the morning, and set out on long journeys visiting out-laying farms, clay-pits, brick-works, factories, railway stations and all kinds of interesting places. When not chased away at once, I would often stay for hours. My curiosity was unbounded, and I learned many wonderful things; how bricks are made, the working of farm machinery, railway operations, etc. When visiting the local railway station the engine driver found it was safest for me (and best for his peace of mind) to take me with hi'm in the cab of the locomotive, rather than have me nosing around the tracks - to which I did not object at all. This inquisitive self-education may have been the origins of my later interest in research.

In the summer of 1950 we moved to Stockholm and I started the third form in a large, municipal school in one of the newly built suburbs south of the city. This did not work out very well. With large classes, the teachers had little time to give me the special tuition and extra training I needed, and after only a month or two it was finally decided that I, and my sister, who had started school the previous year, should attend the state school for the blind and partially sighted at Tomteboda, just north of Stockholm (my brother was not due to start school until the following year). Because the trip each day between the home and the school took too long, my sister and I were forced to live in, seeing our family only in the week-ends and during vacations.

At this school my sister and 1 were, in all practical matters, treated as blind. Although the staff must have known that I actually could see quite well in some situations, a re'gime was set up to teach me to write and read Braille. Reading with the tips of my index-fingers I did not find easy and I qu'ickly developed the knack of reading Braille by eye, because the raised dimples of the Braille letters cast shadows on the paper, making them much easier to read by sight than by touch. For this I was punished; it was considered to be cheating, and for a week I was confined to my bed after classes, being denied to see the other pupils. And, for the next couple of months I had to wear a heavy, lined, black velvet mask covering my eyes in class when reading - to keep me from peeking. Eventually my Braille reading proficiency increased to such a level that the mask could be dispensed with.

Although I had in many ways become a leader at the school for the blind, having a definite visual advantage over the genuinely blind and the gravely partially sighted pupils, and thus gained much confidence in dealing with other children, I was quite unhappy there and strongly resented being treated as blind. So one day I ran away. Completely on my own I crossed Stockholm, from the north to the far south of the city where we lived. I reached my home by midnight, after more than ten hours of walking, retracing the exact route my father used to take us home by car on the week-ends. This caused a great scandal: Unbeknownst to me the bishop was to hold his visitation of the school on that very ctay, but the staff had to search for me and the police had to be called in to help them, thus ruining the whole event. This in no way improved my popularity with the staff; although, as was later somewhat reluctantly admitted, it was considered to be no mean feat, even for a child with normal vision, to find his way across the entire city of Stockholm.

Thus, after only two years at the school for the blind and visually disabled, it was decided that, as a trial, I should again try to attend an ordinary school for the sighted. I was transferred to a newly opened municipal, primary school very close to where we lived, although it meant being moved down one form to compensate for all I had lost during my two years at the school for the blind.

I have a strong suspicion that at the school for the blind and partially sighted they actually just wanted to get rid of me, since I had always created much turbulence and was considered to be rather detrimental for morale among the more seriously handicapped pupils. My sister and my brother (who had entered the school for the blind the previous year) both continued to attend the school, though, staying for two more years until we left Sweden in 1954.

Seen in retrospect, the curriculum at the school for the blind may appear to have been extremely oldfashioned, but it should be borne in mind that at the time this school was considered to be one of the world's leading institutions for the blind and partially sighted, and it was run according to the most modern poedagogical principles. Today, 35 years later, we can only be happy that some of these principles now seem to have been abandoned.

During the summer holidays of 1952, before joining my new school, a problem troubled me very much; although I told no-one about it: While at the school for the blind I had forgotten practically all of what little I had learnt before of reading ordinary print, and I did not cherish the prospect of facing my new fourth form class not being able to read and write.

My father, being at that time sales director with a large company, kept a stock of handouts and gifts for customers, which among other things contained lighters, pocket knives, and -pocket magnifters. One day I borrowed a magnifier and used it to look at pictures in a comic-book. I was frustrated at not remembering how to read the text in the speaking bubbles, since I could now clearly discern the individual letters with the help of the magnifier. I then remembered that my parents had been given a sample-sheet with the Braille alphabet embossed on it together with the ordinary printed alphabet. Using the sheet as a "cipher-key", I managed to "decipher" and read the text in the speaking bubbles.

This incident was truly a turning-point for me and, more than anything else, opened a whole new world to me, who had always so much wanted to be able to read. In just a few weeks' time I secretly taught myself to read properly and my reading skills very quickly improved. I became a voracious reader who devoured all I could lay my hands on, buying magazines and borrowing books in libraries on practically any imaginable topic.

In my new school I had the unforeseen fortune of having a teacher who had an understanding for my handicap and who really tried to help me overcome my problems in class. He was in many ways a very progressive teacher, ahead of his time. He did not adhere to the striet re'gime practiced in the schools in those days. As an example he let me move my desk up close to the blackboard so that I could actually see what was written, breaking the regular geometric order of the desks in the classroom, then so much cherished by the other teachers, an'd he let me move around in the classroom during lessons so that I could inspect at close quarters things that were demonstrated; something completely unthinkable with his colleagues who put their pride in having their pupils sitting quietly at their places. And he made a habit of always telling us what he wrote on the blackboard, which was of great help to me.

Even today, when attending lectures and talks, I always try to sit close to the screen when slides are shown, and I find it easier to follow the presentation when the speaker also tells the audience what is written on the transparencies. When lecturing or giving talks myself, I always do this, showing slides with large print and not crowding too much information into each transparency. In fact, I often treat my audience as visually disabled: If I can see well from a front row seat what I am presenting I know that my audience also will see it.

Because of this outstanding teacher I soon managed to catch up with my peers, regaining much that was lost in the years at the school for the blind. It was also very good for my self-esteem to be able, at least in some fields, to perform like other children of my age, and it also encouraged my parents to try sending my siblings to an ordinary school.

As it happened this was to take place in Caracas, Venezuela. For four years my siblings and I attended a private school run there by a Scotsman. It was a very small school, and we had no great problems in learning English and otherwise adapting to his somewhat unorthodox style of teaching.

After returning to Norway in 1958 we consulted the Department of Ophthalmology at the National Hospital in Oslo. Here Dr. Egill Hansen confirmed the earlier diagnosis of complete achromatopsia with reduced visual acuity, light aversion and nystagmus in all three of us using the anomaloscope and the standard battery of tests - and we were entered into the Archive of the Blind. In No-.rway, like in many other countries, people with visual acuities of 6/60 (l/10) or less are legally considered as blind. This entitled us to special education and to pensions for the disabled, which we have never made use of.

Instead we started to attend grammar school (gymnasium in Norway) where we each, in turn, sat for the General Certificate of Education, Advanced Level (which is required for going to the university). At exams we were given an extra hour for finishing our papers, but little else was done by th*e school authorities to facilitate us attending a school- for sighted pupils. By now, however, we had all become rather expert in coping with the practical problems of attending a school for the sighted. Upon getting our exams we all, in turn, went on to university.

At this time I started my musical education, taking lessons on the clarinet, the cello, and in theory of music at the Oslo Conservatory of Music. I did not have any special plans of becoming a musician, but acquired a professional education along with the Gymnasium. Reading printed music proved to be a real obstacle for me, especiallyprima vista, i.e. sight reading. Today I can easily make enlargements of sheet-music on an office copier, but in the early 60's this was not available to me. For soloists this may not be a great problem, since they often have to learn their parts by heart anyway, but in orchestra play it can be a great handicap.

At university I didn't do too bad. From early in my studies I was employed by the University as part-time lecturer, which meant that I could have my own office. There I had full control of the light level, drawing the curtains during the day if necessary to shut out sun-light, and I could thus work under the conditions that suited me best. N%en attending lectures and seminars I made a habit of arriving early, not out of courtesy to the lecturer, but to be able to get a good seat, sitting, if possible, with my back to the windows and close to the blackboard or projection screen.

After first having a go at law, which I gave up after one year, I eventually ended up studying psychology at the Institute of Psychology at the University of Oslo. In addition I studied philosophy of science, physiology and music science. My interests soon turned to sensory psychology and perception. As I wanted to work independently, I took up auditory research, partly out of interest for audition, but also beeause I believed that my visual handicap would not be a big obstacle to me in this field of research.

At this institute also worked Professor Ivar Lie, Svein Magnussen, Bjorn Stabell and Ulf Stabell, all very accomplished vision scientists. They realized that, being trained in psychophysics, I would be a unique subject in research on rod vision, and they tried to persuade me to leave audition for vision. I first wanted to get my Ph.D. (Mag. art. in Norway), and after my dissertation (on auditory localization and dichotie time/intensity-trading) I switched to vision research.

I have been in research ever since; first as assistant professor (stipendiat in Norway) at the Institute of Psychology, University of Oslo, working in vision research and lecturing in perception and neuro-science, and today as senior research scientist with the Norwegian Telecommunications Administration Research Department, where I am currently doing research and development work on human factors in telecommunications, on telecommunication equipment and services for disabled people and in telemedicine.

My vision research activities soon brought me into contact with vision researchers in laboratories outside Norway, some of which I have visited many times and where I have made many good friends. Beside work in Norway with Svein Magnussen and Bjorn and Ulf Stabell, I have also visited and collaborated with Dr. Robert E Hess at the Physiological Laboratory, University of Cambridge, England, with Dr. Lindsay T. Sharpe, in Dr. Lothar Spillmann's laboratory at the Minikum der Albert-Ludwigs Universit„t, Freiburg, the Federal Republic of Germany, and wfth Dr. L. Henk van der Tweel, at the Laboratorium voor Medische Fysica, Universiteit van Amsterdam, The Netherlands - collaborations that have continued after I joined the Telecommunications Administration. The results of these experiments are dealt with in other chapters of this book (for a full list of these works see the Bibliography below).

My siblings also entered university; my sister studied Latin, English and music science, and my brother qualified as a psychologist. My sister now works at the library of the Norwegian Association for the Blind in Oslo, translating and producing books in Braille; unlike me she has not forgotten her four-year training at the school for the blind. My brother is employed as a high-ranking civil servant with the Norwegian Directorate for Labour, working mainly in organizational development.

In 1965 I met Nina Marie Loberg (born 10.7.1944), who studied psychology, and we were married the following year. There are no known achromats in her family and there are no relations between our families. We have two sons, Cato (born 1.3.1967) and Alexander (born 19.1.1969). Both Nina and the boys have perfeetly normal colour-vision as tested with the Farnsworth 100 Hue Test. My brother is also married and has four children, two sons and two daughters; all with normal colour-v'ision. My sister has not married and has no children.

I have never, nor have my siblings, received any qualified vocational counselling or help in planning my education and my career. What advice I have had has usually been unfounded and ill-coneeived. The suggestions have included everything; from simple clerical and assembly-line work to the traditional work for the blind, usually involving simple, manual, low-paying jobs requiring little or no education, and showing complete disregard for what actual tasks the work demanded. Most so-called 44 simple'jobs, e.g. filling in forms, sorting mail, filing and retrieving files, assembling components, cleaning, tending machines etc., usually require good visual acuity and colour-vision. No one ever suggested theoretical or academic work requiring higher education. Luckily my parents had always wanted their children to have an academic educa- tion, and circumstances were highly favourable for this in Norway in the 60's and 70's.

In my research work I have had few problems related to my visual handieap. I work in areas where, to a large extent, I can plan my own work and choose my own tasks. In addition to the research activities my work also includes administrative diities, giving interviewe, going to meetings and giving talks, both in Norway and abroad, and I also lecture regularly at the University of Oslo. These activities pose few practical problems for an achromat. Typing used to be quite a bother, since I had to lean over the type-writer with my magnifier to be able to read what I had written, but now I use a PC and a word-processing program for all my typing, and this is a very useful tool to me. To overcome my low visual acuity I have to get close (150-200 mm) to the screen, and I have a large (19") screen installed. With modern printers I can have my documents printed in large type-face, making them easier to read.


Trying to explain to someone with normal, or nearly normal, colour-vision what it is like to be totally colour-blind, is probably a bit like trying to describe to a normally hearing person what it is like to be completely tone-deaf, i.e. not possessing the ability to perceive tonal pitch and music. My task, though, is probably a bit simpler than the case of the tone-deaf, since practically everyone has had experiences of achromatic (i.e. colourless , or black & white) or monochrom pictures and renderings, an*d certainly must have witnessed the gradual disappearance of colours when darkness sets in.

A first approximation, then, in explaining what my colour-less world is like, is to compare it to the visual experiences people with normal colour-vision have when viewing a black & white film in a cinema or when looking at good black & white photographic prints (good here meaning sharply focused, high contrast with a long grey-scale, as in crisp, high quality, glossy, technical prints).

This, however, is only part of the story because I have so far only dealt with the achromatic aspect of my perception. To get a fuller understanding of my visual world one must, in addition to my colour-blindness, also take into account my light aversion (i.e. hyper-sensitivity to light) and my reduced visual acuity. In the following I will deal in turn with each of these aspects of typical, total achromatopsia.

Total colour-blindness

As mentioned above, I only see the world in shades that colour-normals describe as black, white and grey. My subjective spectral sensitivity is not unlike that of orthochrornatic black & white film'. I experience the colour called red as a very dark grey, nearly black, even in very bright light. On a grey-scale the blue and green colours I see as mid-greys, somewhat darker greys if they are saturated, somewhat lighter greys when unsaturated, like pastel colours. Yellow is usually a rather light grey to me, but is usually not confused with white. Brown usually appears as a dark grey and so does a very saturated orange. When asking other total achromats to do such matches I get practically the same judgements from them. In the literature I have also found several descriptions of the colour-determinations made by other typical, total achromats, which all very closely match my ownjudgements (see e.g. Bjerrum, 1904; Larsen, 1918).

Although I have acquired a thorough theoretical knowledge of the physics of colours and the physiology of the colour receptor mechanisms, nothing of this can help me to understand the true nature of colours. From the history of art I have also learned about the meanings often attributed to colours and how colours have been used at different times, but this too does not give me an understanding of the essential character or quality of colours.

Coloured and B & W pictures are usually indistinguishable to me. But sometimes I can, often quite easily, tell coloured and noncoloured pictures apart. Coloured pictures may look less crisp, or slightly less in focus, and often have less contrast than comparable monochrom pictures. Under some conditions I am able to tell a polychrom picture from a monochrom one by noting the different surface textures of the coloured inks used to print the picture. I do this by tilting it so that the light reflects differently in the different inks: Coloured inks ”f various hues show up as duller or glossier patches. I am sometimes able to see the numbers on the Ishihara and ™sterberg pseudo-isochromatic plate tests by this technique. Given the time I might be able to fool an unwary tester. A few other achromats have also shown me this trick, not because they wanted to deceive me, but because they thought that they had a vestige of colour-vision. However, if I cover the test- plate with a glossy, transparent foil they are unable to do this trick: Varnishing or covering pictures with high-gloss films destroys the effect.

I have never experienced anything "dirty', "impure", 44 stained' or "washed out" about colours, as reported by the artist Jonathan I. who completely lost his colour-vision after a cerebral concussion (Sacks & Wasserman, 1987). When, occasionally, bolour-pictures do look less crisp to me than B & W pictures, it is usually because of bad printing, lower contrast or faded inks.

Once when Bjorn and Ulf Stabell were measuring my spectral equal-brightness function (using their Wright colorimeter) I felt that I could detect slight differences between colour hues by distance cues, which could be due to chromatic aberration in the optics. I informed the Stabell brothers about my suspicion and an ad hoc experiment was quickly set up to test my conjecture. I was to try any ploy that I could think of to guess the hue of the test field, and they were to counter my ploy, making mock changes or unexpected changes of hue. When the day was over I had not been able to guess any colour hue beyond the pure chance level.

When I know the colour of an object I may often refer to its colour name when describing it or referring to it to other people. Since colour names have meanings for most people, communication is made easier. This, in turn, leads to other people using colour names when addressing me, even those who know of my colour-blindness. Sometimes this can be of help to me, when e.g. they refer to a red book among other light-coloured books, but re'ferring to a red book among black and dark-coloured books is of little help to me.

Colours do not help me to distinguish objects from their backgrounds. Since the grey-tone that I can match to a particular colour changes with changing illumination, objects that are partly in bright light and partly in shadow, such as flowers in the mottled sunlight coming through the branches of a tree, can be very hard to see. The same applies to objects under glass, behind windows or under water, since shiny surfaces give off reflections and glare which makes it very difficult to see what is behind them. It is usually impossible for me to recognize people in cars or see if they are waving at me, sometimes even at close quarters, because of the destructive reflections from the windows. NMere the colour-normal can use the continuity of the colour-hues of an object to perceive the figure through disturbing reflections, 1 see the reflections and the objects behind them translated into different shades of grey, and only when the contrast between the object and its background is very high, or the movements are very distinct, can I see what is behind a strongly reflecting surface as an object. Wearing polarizing clip-on sun-glasses improves things to some extent, and I use them much, although I am sometime's distracted by seeing the mottled stress-patterns in glass that are normally invisible.

When I was about 14 I discovered, quite by accident, the use of coloured filters for analyzing and identifying different colour hues. We had a large salad bowl made of transparent, red-coloured plastic. One day, holding the bowl before my eyes, I noticed that the pattern of the table-cloth turned nearly white when seen through the bowl. By moving the bowl to and fro, I could make the red-coloured pattern change from light to dark. I was intrigued by my discovery and tried out several other transparent filters of various colours, thinking that I would be able to solve the problem of my colour-blindness by using a few differently coloured pieces of plastic to analyze and thus be able to name any colour. From a purely practical point of view I contemplated the great advantage of being able to determine for myself the name of a colour without having to ask other people. I even envisaged a solution of narrow strips of filters mounted at the upper edge behind the lenses of my glasses, thus dispensing with a set of hand-held filters, and making their use more discreet.

Nothing came out of these ideas of mine as I did not have the resources at my disposal for ear"rying them through. I have since learned that such filters for analyzing colours are actually made for "normal' (i.e. anomalous trichromat and dichromat) colour- blind electronic engineers to aid them in reading the colour-coded rings denoting the values of resistors. I have tried, but never succeeded in, obtaining a set of such filters, although the spectral transmission bands of these filters would probably not suit the spectral sensitivity of my rods very well.

Traffic-lights can sometimes pose a problem to me. I have long since learned that red is the top light, amber is the middle light and green is at the bottom. At night, in the evening or in the day if the trafficlights are in a shadow, I have no problem in detecting which aspect is shown: By noting its position I can be a law-abiding cyclist or pedestrian. In full sun-light, on the other hand, determining which aspect is shown can be quite impossible; if the traffic-lights are back-lit I am dazzled by the sun and cannot see the weak lights; if the sun is behind me, the reflections in the lenses of the light signals can be so strong that it is impossible to determine which one is showing. In such situations I have to watch the traffic, following the other pedestrians when they cross the street. This can lead to dangerous situations when encountering unsuspect'ed cars if I follow someone crossing a street against a red light, believing that the crossing is safe.

I often visit art galleries and I am very interested in the visual arts. Looking at paintings I can appreciate form, composition and technique, although of course, I cannot appreciate the coloristic aspects. Monochrome prints and graphic art I can normally enjoy in the same way as colour-normal people and the same goes for sculpture and architecture. When lecturing on vision and perception I frequently show transparencies with works of art to demonstrate my points.

When painting house or redecorating I must always make sure that I use the correct colours by carefully reading the labels on the paint tins. My wife normally selects the colours for the house. If the contrast between the new and old colour in terms of grey-tones is not too small, I have no problem painting the house. If I repaint with the same colour, I sometimes have a problem telling the freshly painted areas from the unpainted ones, especially after a break, when the fresh paint is not so "wet' anymore. If I repaint with a different colour that is very close to the old one in terms of grey-contrast, I have difflculties in seeing if the new coat covers the old colour properly. Sometimes the only way to resolve this problem is either to paint very systematically, or to look obliquely at the wall for the shiny "wet' freshly painted parts.

When buying clothes on my own I will only take advice from a sales-person in whom I have the highest confidence, otherwise I usually ask for "safe" or neutral colours; white shirts, grey trousers, black socks and shoes: I would e.g. never select a tie on my own. For the important colour-choices I have to rely completely on my wife or on close friends who I trust and who know my taste and preferences. To avoid embarrassment I often have to mark my socks in some way so that I will not mix up differently coloured pairs, it can be impossible for me to tell light blue, beige and light grey, or dark blue and black socks apart.

Picking berries has always been a big problem for me. I usually have to grope around among the leaves with my fingers, feeling for the berries by their shape, except in the shade or in the evenings when light levels are low. Then I can usually see the berries; the red ones as small "black' spheres among the "grey" leaves. The only berries I can easily see in bright sun-light are the white 'snow-ball" berries of the Guelder-rose bush.

Indoors most flowers are easy for me to discern, out-of-doors, though, I usually only recognize the white and the yellow ones: The oxeye-daisies, not to speak of the dandelions in my lawn, are most conspicuous to me; red roses on bushes I see best in the twilight when I can separate the "black' flowers from the icgrey" leaves.

Colours are frequently used to code or to highlight information. For me this usually makes matters worse because good colour contrast very often does not transform into good grey-contrast. Sometimes the contrast is so low that the information is next to lost. Black print on red price labels, yellow print on a light blue background, dark green on a bright red background are all extremely difficult for me to read. A teaching aid that has always failed with me is the use of colours in e.g. arithmetic; adding the red and the green objects, subtracting the blue ones from the yellow ones. Colourful Venn diagrams for teaching basic set theory only makes the task more difficult for me.

Hypersensitivity to light

As far as ean be determined, the retinae of my eyes do not contain any cone-receptors at all, only rod-receptors; or cones are present but in such reduced numbers that they do not in any measurable amount contribute to the visual process (see Sharpe and Nordby, THE PHOTO-RECEPTORS IN THE ACHROMAT, chapter X). Since the rods are much more sensitive to light but also saturate at lower light intensities than the cones, my visual system is well adapted for vision only under low-lighting conditions. In fact, my vision will not function at all in bright light (e.g. out-of-doors in full day-light), if I do not adopt specialized visual strategies and behaviour.

I am easily dazzled and, in effeet, blinded if I expose my eyes to bright light. If I open my eyes fully for more than one or two seconds under such conditions (about 1000 scotopic trolands and up), the scene I am gazing at is quickly washed out, turned into a bright haze and all structured vision is lost. It can be very distressing for me, and sometimes even painful, to perform demanding visual tasks in very bright light.

This hlypersensitivity to light, or light aversion, is usually referred to as photophobia, but ]las nothing to do with the irrational psychodynamic "phobias". In fact, I really like being out in the warm sun, provided I dont have to perform exacting visual tasks. I do not like to read or write in the sun; digging the garden or mowing the lawn, on the other hand, is no problem for me even in bright sun-light.

My main problem, then, is to restrict the intensity of the light entering my eyes. This, as I will show, can be achieved in several ways and I tend to use them all, alone or in combination, according to what the situation demands. In common with nearly all the other achromats I have interviewen, I have developed special visual strategies for restricting the amount of light entering my eyes.

The most obvious strategy is, of course, simply to avoid direct strong light. Staying indoors or in the shade is one way of achieving this if there is no special reason for being in intense sunshine (such as on a bright beach in the summer or in bright sun-lit snow in the winter). Indoors, whenever possible, I try to place myself with my back towards bright windows and strong light sources and avoid having direct sun-light falling on my work-place.

Shading my eyes from direct, intense light with my hand or a visor may be necessary. Ordinarily I wear sun-glasses, in casu, the lenses of my glasses are photo-chromatic (i.e. tinted lenses which darken in bright light). Out-of-doors I often wear an extra clip-on polarizing filter for cutting down on bright light and for dealing with visually destructive glare and reflections from shiny surfaces. The best sun filters I have tried, though, are the special coloured glasses which are made for the retinitis pigmentosa patients. They have a spectral cut-off at 550 nm, passing only the long wavelengths and they give a very pleasing light-attenuation, but they are socially less attractive because of their red appearance.

Actually, it is not only the brightness of what I am looking at that is most bothersome, but the brightness of the total visual field; the larger the part of the field that is illuminated, the more bothered I am. Blinkers or side-shields on the spectacle frame may help in shutting out unwanted light, but they also prevent motion detection in the peripheral visual field, which is important for moving safely about, and I don't use them. If I must see small detail in bright light, e.g. read printed information or look at a map in the bright sun, I turn away from the light, putting the material in my shadow.

The most typical visual strategies, though, that I resort to consists in squinting, i.e. partially closing the eyes and looking through the narrow slits formed by the eyelids, and in frequently blinking the eyes. This habit has been reported by nearly every author and seems to be universally resorted to by typical, complete achromats (see e.g. Bjerrum, 1904; Larsen, 1918; Krill, 1977). If light levels rise and my retinal illuminance approaches 1000 scotopic trolands, my fully constricted pupils cannot further contract and I have to squint to deal with the higher intensities and to avoid saturating the rods.

At higher light intensities even this is not enough, and I also have to start blinking my eyes to shut out excessive light. My blinking is triggered when saturation sets in. The blinking frequency is slow at first, only once every four-five seconds, but the periodicity increases with increasing light intensity, to three to four blinks a second.

At lower light levels, when the blinking rate is slow, the blinks themselves are also rather brief. As light levels go up, the blinking rate also goes up, but the blinks become longer, i.e. the duty-cycle increases. At the very highest light levels where my visual system will function (e.g. new snow in briglit sunlight) the blinks are so long that my eyes are, in fact, closed most of the time except for brief opening blinks once every two to three second. Whether blinking my eyes briefly at low light levels or extending the length of the blinks at high intensities, I still experience a visually stable world in which I can orientate myself and move about. It should be mentioned, though, that I am able to suppress the blin-king on some occasions. In laboratory investigations 1 have actually sustained luminances over 500,000 photopic trolands, blinking only occasionally to keep my corneas moist.

This squinting and blinking behaviour is a strain socially. In bright light people immediately notice that sometl-iing is wrong with mv eves. and show this by their reactions to me. As a child I was often approached by complete strangers who wanted to know what was wrong with my eyes. Wearing dark glasses or clip-on sun filters can alleviate this social burden to some extent.

At higher light levels the peripheral visual field is much more affected than the central part of the field, which results in a partial tunnel vision. I will still detect movement in the far periphery, but have much more difficulty in identifying wha-C is moving and reacting adequately to it. This makes me move in a rather hesitant and stiff way, sometimes bumping into people or things, and to be overcautious when moving about in agitated surroundings or in strange places. As soon I am in the shadow or indoors again I move in a more relaxed and confident manner.

It is very clear to me today that the most debilitating, handicapping and distressing consequence of my achromatopsia has been my hypersensitivity to light and the resulting light aversion, which is also reported by all other authors. This is also the unanimous verdict of all the achromats I have interviewed so far. Both the practical problems of being daz- zled, the narrowing of the visual fields, resulting in restricted mobility, and the social problems of light aversion and feeling clumsy in intense light is frequently reported by my informants as being more of a hindrance to them than not being able to experience colour hues or to discern small detail.

Reduced visual aeuity

In a retina where only rods function, visual acuity will be drastically reduced, since it is the densely packed foveal cones that are responsible*for the high acuity of central vision in the normal retina. My visual acuity is 6/60 Snellen (i.e. 0. 1 of normal acuity) which means that at a distance of 6 meters I can read those letters on the Snellen chart that people with normal acuity can read at 60 meters. This low acuity is typical for all typical, complete achromats repor-LLed in the literature and for those I have interviewen. Measured with an interferometer under optimal conditions my acuity improves to 6/50.

My visual acuity, though, may vary quite a bit depending on the illumination. At higher luminances my acuity very quickly deteriorates, but it may improve slightly at lower light intensities, such as at dusk after the sun has set, but before it gets really dark, or indoors with the curtains drawn during the day, or in the evening with not-too-strong incandescent, tungsten illumination. My best acuity seems to coincide with the illuminance levels at which I do not have to squint or blink my eyes.

I experience a visual world where things appear to me to be well-focused, have sharp and clearly defined boundaries and are not fuzzy or cloudy: I can easily tell the difference between what people with normal vision call a well-focused and a not so wellfocused photograph. When giving a talk"to the Kenneth Craik laboratory in Cambridge, one of my slides came up slightly out of focus because of a thinner slide-Mount. I quickly refocused the slide myself, but Professor Fergus W. Campbell, who attended the talk, commented aloud that to his astonishment I did this as well as any projectionist. Details that are too small for the low resolution of my coarse retinal matrix disappear, blending into the background, but when they are brought closer and become large enough for me to discern, they are just as sharp and well-defined as other objects.

I am hypermetropic, or far-sighted, and my ophthalmic correction today is +8 diopters. This is rather fortunate since my lenses thus magnify the retinal image by a factor of 0.7; it would have been worse had I been myopic, or near-sighted, thus requiring minus-lenses. With my glasses I can read small print by bringing the text close up to my eyes; about 250 mm away for 6 mm high letters, 150 mm away for 4.5 mm letters, 80 mm away for 3 mm letters.

Letters smaller than 2 mm, such as used in the telephone directories in most countries, I cannot read without additional optical magnification.

I use a small, folding, pocket magnifier for reading newspapers, magazines, books, typed documents, etc., even when the print is large enough to read with my glasses alone. My first pocket-magnifier (see above) had a +9 diopter, 50 mm o lens set in a transparent perspex frame, rivetted in one corner to a piece of leather. The lens could be folded up into the leather cover to protect it, when unfolded the leather cover served as a handle for holding the glass. Today I use a magnifier with a +16 diopter, 30 mm o, biconvex lens, which gives me the necessary magnification for reading large amounts of text wi@hout undue visual strain, and makes it possible for me to manage the very small print in Telephone directories etc. M%en reading I usually hold the glass in my right hand, the book in my left, and I always use my donnant left eye. Together with my spectacles, this magnifier is the most important tool I have, and I always carry it with me.

I have, of course, tried many other different loupes, reading glasses and magnifiers of various designs offered by opticians, but they are usually either too big, too heavy, too obtrusive, not pocketable, too weak or too strong for my needs. The best design is one that I can carry in my shirt breast pocket so that it is always at hand, one that is small and easy to hold, but with sufficient power for reading small print such as the print found in the Telephone directory.

I have considered other types of visual aids, such as video-systems etc., but they all seem to fail on one or several points. Usually they are too large and heavy to carry around, they are complicated in use or they are too powerful, giving a very small field of view which makes it rather hard to read continuous text. It is most important to me that I can always take the aid with me and use it wherever I go.

Reading things at a distance, such as street names, destination boards on buses and trains, time-tables in stations, flight-departure indicators in airports, signs and labels in museums, price labels in shop windows etc., is usually impossible or, at best, very difficult. To use my magnifier to make the letters legible to me I have to get close to the material, but this is not possible when signs are placed high up on walls or poles, behind windows, in glass cases or behind barriers. One special problem is reading the destination boards on approaching buses which only stop on signal. Occasionally, as a last resort, I have had to stop every approaching bus until the right one came along, invoking the drivers'wrath and being showered with abuse for my pains.

It can be difficult for me to find my way in unknown surroundings, a problem when travelling or visiting strange places. I solve this by carrying with me a small, monocular, 8 power, close-focusing telescope, which I can conceal in my hand, and which I use for reading street names, destination signs and other information that I cannot otherwise reach. I also procure information in advance by studying maps and plans, and by inquiring for detailed directions on how to find my way.

Much more serious, though, than the problem of finding my way in strange places, is my disability to identify people only from their facial features at a distance of more than a few metres. I may easily pass people I know well in the street without recognizing them, and those who do not know of my visual handicap may find me aloof or downright rude. Picking out people I know well in a crowd or in a large room, e.g. a restaurant or theater, is very difficult and socially embarrassing. I usually recognize people from their total appearance, i.e. their clothes, their way of moving, prominent or special features; but foremost, from their voices. @en expecting people I know well I can manage to identify them at 10-15 metres distance, and if I know what clothes they will be wearing I may even be able to identify them at distances of 20 metres and more. Often, though, I fail to recognize people I know, with embarrassing consequences. Sometimes even peo- ple who know about my visual handicap are offended by my seemingly disinterest and neglect of them. The reason may be that I often, apparently, behave visually rather normally, leading them to believe that my disregard is intentional.

A problem that seemed more serious to me earlier than it does now is that I cannot hold a driver's licence. My brother and I cycle and we have ridden mopeds in Oslo. Driving a car, though, is not possible for us, although my brother actually took some driving lessons. He had to give up, though, after attempting to drive down some stairs in a park. Today I only cycle where I have access to reserved cycle lanes or when traffic is light.

In other fields, however, low visual acuity has not been an insurmountable obstaele. My sister has since her early teens done all kinds of needlework, producing tatting, bobbin-lace and embroideries to very high standards. To keep her hands free, she uses a clip-on, jeweller's loupe with her working- glasses. This gives her a large magnification (10 times), but a very small field of view, and it is not very suitable for reading. She needs help in selecting the colours of the threads and yarns, but once they are selected and labelled she manages on her own.


From my account it can be seen that I often avoid showing my visual handicap and sometimes simu- late having normal vision. I often experience negative attitudes if I expose my visual disability before people get to know me. The stigma of being partially sighted can be very unpleasant. If I show my handicap early to people who do not know me I will be eategorized as a disabled person and will be treated in a patronizing way and often not taken seriously. If, on the other hand, I first expose my visual handicap to people after they get to know me, I get fewer reactions. With most vision scientists and ophthalmologists I feel at ease, they can even be overcautious about offending me, but some ophthalmologists have treated me in the condescending way they sometimes treat their patients.

In spite of this and all the other practical and social problems I encounter, I still feel that I live a very rich and interesting and useful life. It is my ambition that these very personal and rather private accounts given here will prove to be of some use to vision researchers and to people dealing with typical complete achromats.


I wish to thank my colleague and friend Dr. Lindsay Theodore Sharpe for his critical comments on the manuscript. I also want to thank my collaborators and friends Bjorn Stabell and Ulf Stabell for many helpful suggestions.


The pictures ar not implemented, because of their bad quality (copied).

Figure 1. My family pedigree. Solid, black symbols indicate the typical, total achromats, i.e. my siblings and I, light grey symbols indicate non-achromats.

Figure 2. Photograph taken of me 1-2 weeks after birth. I showed no obvious signs of squinting or light aversion at the time.

Figure 3. Photograph of me, my sister and my brother (from left to right) in bright sun-light. We all display squinting and light aversion behaviour typical of the complete achromat.

Figure 4. Spectrum with grey-matches in sun-light (upper) and in incandescent hght (lower row). The matches of the grey patches are made at the points indicated on the spectrum. The Spectrum was obtained from the Rochester Institute of Technology, the grey patches are from the KodakLyrev scale.


The following is a list of all the investigations of my visual system that have been published.

Zuletzt geändert am 15.2.1996.

© for text by K. Nordby
© for layout by Sebastian Bonhag