|Year : 1984 | Volume
| Issue : 1 | Page : 23-24
Total colour blindness
BK Baidya, DN Chattopadhyay, SN Bhattacharya
North Bengal Medical College, Sushrutanagar, India
B K Baidya
North Bengal Medical College, Shushratanagar, Distt. Darjeeling ,W.B..
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Baidya B K, Chattopadhyay D N, Bhattacharya S N. Total colour blindness. Indian J Ophthalmol 1984;32:23-4
Total colour blindness or monochromatism is a rare condition, its incidence being about 1 in 3,00,000 of the population. This is a hereditary disorder of colour vision being transmitted by an autosomal recessive gene. Two types of total colour blindness exist, cone-monochromatism, much the rarer one where the defect is confined to the colour sense only with normal visual acuity; and Rod-monochromatism which is associated with other defects like low visual acuity, photophobia and nystagmus.
Here we report the incidence of rod monochromatism in a family where 3 out of 7 siblings have been affected by it.
| Case report|| |
Two sisters and a brother form a Hindu family attended our O.P.D. with the complaints of poor vision and distress in sunlight since their early childhood. Their elder brother who was accompanying them stated that they could not recognise any colour since childhood.
The clinical picture was almost identical in all 3 cases. The sisters were aged 25 and 18 years and the brother 23 years. They were obviously disturbed in daylight as evidenced from the squeezing of the eyelids.
The visual acuity varied from 6/60 to 6/24. Moderate degrees of myopia were present in all cases but correction by glass did not improve the vision. There was medium horizontal jerky nystagmus which increased on, lateral gaze. Examination of anterior segment of the eyes did not reveal any abnormality. Other than the myopic present on the temporal side of the disc, the fundi did not show any abnormality.
The colour vision was tested with wool matching and Ischihara's chart. All these showed total colour blindness with ability to differentiate only different shades.
They were much more comfortable in the dark. The younger sister had a history of epileptiform fits. The other two did not have any neurological abnormalities. All of them were of them were of average intelligence and passed the school-leaving examinations.
Study of the family show that the affected siblings are the last 3 issues of the parents, the previous 4 being completely normal in all respects.
The pedigree analysis showed no involvement in previous two ad subsequent one generation.
There is no direct evidence of consanguinity among the parents. But they were married within the same `GOTRA'(families having common ancestors). This suggests 'a strong possibility of consanguinity.
| Discussion|| |
Rod-monochromatism is a rare condition affecting both sexes in nearly equal proportions. The Hereditary character of this condition is autosomal recessive consanguinity in the pedigrees occurs in some 20% of cases. In the present report though there is no direct evidence, there is a strong possibility of consanguinity among parents based on circumstantial evidences. Associated ocular defects like poor visual acuity, nystagmus and photophobia were present in all the affected siblings. Other associated abnormality was found in only one sibling in the form of epileptiform fits. It is well known that genetic defects manifest more commonly in the later issues of older parents. This is also evident here as the last 3 siblings out of 7 being affected
| Summary|| |
A family is reported where three out of, seven children were affected by total colour blindness (Rod-monochromatism). The pedigree showed an autosomal recessive heredity with possible consanguinity among the parents.
| References|| |
Sorsby. A., 1972, Modern Ophthalmology, Vol. 3, p. 194, London.
Duke-Elder, S., 1964, System of ophthalmology, Vol, III part 2 P. 665, Kimpton. London.
Weale, RA., 1953, Trans. Ophthalmol Soc. U.K., 73:241.