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CASE REPORT
Year : 1984  |  Volume : 32  |  Issue : 1  |  Page : 23-24

Total colour blindness


North Bengal Medical College, Sushrutanagar, India

Correspondence Address:
B K Baidya
North Bengal Medical College, Shushratanagar, Distt. Darjeeling ,W.B..
India
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Source of Support: None, Conflict of Interest: None


PMID: 6334028

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How to cite this article:
Baidya B K, Chattopadhyay D N, Bhattacharya S N. Total colour blindness. Indian J Ophthalmol 1984;32:23-4

How to cite this URL:
Baidya B K, Chattopadhyay D N, Bhattacharya S N. Total colour blindness. Indian J Ophthalmol [serial online] 1984 [cited 2020 May 27];32:23-4. Available from: http://www.ijo.in/text.asp?1984/32/1/23/27362

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 Top


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 Top


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 Top


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.[3]

 
  References Top

1.
Sorsby. A., 1972, Modern Ophthalmology, Vol. 3, p. 194, London.  Back to cited text no. 1
    
2.
Duke-Elder, S., 1964, System of ophthalmology, Vol, III part 2 P. 665, Kimpton. London.  Back to cited text no. 2
    
3.
Weale, RA., 1953, Trans. Ophthalmol Soc. U.K., 73:241.  Back to cited text no. 3
    




 

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