Letters to the editor 127

Having been involved with the treatment of Cone dystrophies start either foveolar or accounted for more than half the blindness, a amblyopia for more than 30 years my views perifoveolar. The latter type is known as peri- finding in common with many countries. Br J Ophthalmol: first published as 10.1136/bjo.76.2.127 on 1 February 1992. Downloaded from have altered very little. pheral cone dysfunction and is characterised by Quite rightly Dr Potter suggests that one My work reported in 1964 still stands that a a disturbed full field cone ERG, a relatively solution to the problem of cataract blindness monitored period of total occlusion overcomes well preserved and normal colour would be to train eye workers to perform amblyopia quickest and best. As improvement vision or an acquired type III blue-yellow intracapsular cataract extractions (ICCE). One occurs one can modify the techniques to part colour vision defect.34 Static perimetry reveals argument made in support of the more expen- time, or partial, to achieve the final result. a perifoveolar dip.2 The blue-yellow defect, sive operation of extracapsular cataract extrac- However in the past 10 years or more I found often dichromatic, is an exaggerated small field tion (ECCE) with intraocular lens implantation the best answer was prevention of amblyopia tritanopia. Case VI.6 is a good illustration. has been the permanence of the correction of and this was achieved by early peripatetic This patient could not read the 8° plate tests but the surgically-induced aphakia. The aphakic orthoptic screening in postnatal, infant, and made a classic tritan response with the 20 Panel glasses used after intracapsular extraction can preschool clinics. D-15 test. become broken or lost and frequently are not This meant that squints and amblyopia were The dystrophic process affects the peri- replaced. detected very early and, with prompt referral, foveolar cones, including the blue cones which Few data are available on the proportion of required less specialist treatment; and ambly- have their maximum density at 1-50 eccentri- people who have had intracapsular and opia was only relative in depth and required city. The blue cone-free foveolar region who continue to wear their corrective glasses. I only minimal occlusion to obtain a cure. Indeed becomes enlarged resulting in a strong decrease was wondering whether Dr Potter had in- most children were detected before amblyopia in blue sensitivity. formation on the proportion of people who had time to occur. A PINCKERS were blind because of uncorrected surgical (as defined) had Department ofOphthalmology, I would urge the need to continue to strive St Radboud Ziekenhuis, aphakia, and also the proportion of aphakics for early screening and public education before Philips van Leydenlaan 15, who in fact remain blind after surgery either the age of 4 years contrary to the Hall report. 6500 HB Nijmegen, The Netherlands because of surgical complications or loss of their aphakic glasses. G V CATFORD 1 Van Schooneveld MJ, Went LN, Oosterhuis JA. HUGH R TAYLOR 1I Devonshire Place, Dominant cone dystrophy starting with blue cone University ofMelbourne, London WIN IPB involvement. BrJ7 Ophthalmol 1991; 75: 332-6. Department ofOphthalmology, 2 Pinckers A, Marre M. Basic phenomena in Australia 1 Hall DMB. Health for all children. Oxford: Oxford acquired colour vision deficiency. Docum Oph- Medical Publication, 1989. thalmol 1983; 55: 251-71. 1 Potter A. Causes of blindness and visual handicap 3 Pinckers A, Deutman AF. Peripheral cone disease. in the Central African Republic. BrJ Ophthalmol Ophthalmologica 1977; 174: 145-50. 1991; 75: 326-8. 4 Noble K, Siegel IM, Carr RE. Progressive peri- Cataract surgery pheral cone dysfunction. AmJ Ophthalmol 1988; 106:557-60. Reply SIR,-The problem ofthe enormous backlog of cataract surgery in the third world will not I SIR,-Those of us working in Africa are well fear be solved by the methods advocated by Mr Reply aware of the problem of uncorrected aphakia. Arthur Steele.' There are a number ofreasons for this problem. I was fortunate to get my surgical training in SIR,-In an effort to be concise we have Spectacles may not have been provided at the Pakistan where my colleagues routinely did apparently not been sufficiently clear. The time ofthe original cataract extraction. Patients 150 cataract operations single-handedly in a 6 h main conclusion of our article - concerning a may not have found the money for their session. Their technique was a Graefe knife progressive cone dystrophy and not a cone purchase. The glasses may well have been incision, peripheral iridectomy, intracapsular dysfunction - was that our family represents a broken or lost at a later date. Other patients are lens extraction with forceps, or cryosurgery distinct, as yet undescribed entity (last sentence unable to make the effort to adapt to the larger and one to three corneoscleral sutures with 8/0 of the abstract and last sentence of the last image and visual distortions. Still others were silk. The surgery was ofsuperb quality and the paragraph but one of the discussion). given a prescription for a pair of glasses which http://bjo.bmj.com/ results were excellent. It is now sufficiently well documented that when they presented it to a private optician Ifwe had performed the surgery with micro- genes coding for visual pigments may ifsubject found the cost prohibitive. A depressing litany scopes, three-stage incisions, IOLs, running to mutation, lead to ocular disease: X-linked ofexcuses that I regularly encounter. 10/0 sutures, etc, then I suspect the rate would cone dystrophy in the case of a deletion of the From my 4 years' work in the Central have fallen from 20-30 operations an hour to red cone pigment gene,' autosomal dominant African Republic I found that uncorrected two to three an hour. The resulting cost would in the case ofa mutation of aphakiaaccountedfor 8% ofbilateral blindness. be so high that only the wealthy could afford the rhodopsin gene.2' Sufficient reason for us This included a majority who had one eye blind treatment. to ask for an analysis ofthe tritan gene (thus not from unoperated cataract and the other aphakic on September 25, 2021 by guest. Protected copyright. No-one would try to ignore the brilliant as Dr Pinckers states: 'The authors ... looked eye without spectacle correction. Of26 patients advances in ophthalmic surgery developed in invain.. .). with bilateral aphakia without spectacle correc- the west. However I would urge my colleagues L N WENT tion eight had other problems that could not be M J VAN SCHOONEVELD improved with glasses (optic atrophy, maculo- there to accept that for huge numbers of J A OOSTERHUIS cataract blind in Africa and Asia such tech- pathy, pupillary membrane, retinal detach- niques may not be the most appropriate and 1 Reichel E, Bruce AM, Sandberg MA, Berson EL. ment, and phthisis.) that simple methods in expert hands can give An electroretinographic and molecular genetic Now the alluring prospect of extracapsular study of X-linked cone degeneration. Am excellent results at low cost. J cataract extraction (ECCE) with intraocular IAN THOMSON Ophthalmol 1989; 108: 540-7. lens implant is suggested for Africa. This could Agogo Hospital, 2 Drya TP, McGee TL, Reichel E, et al. A point PO Box 27, mutation of the rhodopsin gene in one form of solve the problem of uncorrected surgical Agogo, Ghana retinitis pigmentosa. Nature 1990; 343: 364-6. aphakia. But is it realistic for rural Africa at the 3 Drya TP, McGee TL, Hahn LB, et al. Mutations present time? J with the rhodopsin gene in patients with auto- 1 Steele A. Cataract surgery. (Editorial.) Br somal dominant retinitis pigmentosa. N Engl ECCE is a more complex surgical procedure Ophthalmol 1990; 74: 130-1. J Med 1990; 323: 1302-7. requiring sophisticated equipment (needing maintenance) and a longer training for the surgeon involved who would have to be a fully Dominant cone dystrophy starting with blue Cause ofblindness in the Central African trained medical doctor. Intraocular lenses are cone involvement Republic more expensive than aphakic spectacles. In the Central African Republic there is only one SIR,-The authors of the paper' in vain looked SIR,-It was with much interest I read the permanent centre for cataract surgery. It is in for a blue gene defect. The blue-yellow colour recent paper by Dr Andrew Potter.' the capital Bangui. The whole of the rest of the vision defect they observed however finds its One of the important early steps in the country and the majority of the population are origin in the physiology ofthe . development of a national prevention of blind- very infrequently served by visiting surgeons of the macular region, if fixation is preserved, ness programme is the assessment of the who may spend up to a week in any one place. gives rise to blue-yellow defectiveness regard- dimensions of the problem of blindness and a Such provincial hospitals and dispensaries may less of the cause: X-linked or dominant in- characterisation of the leading causes of blind- well not have mains electricity. herited conedystrophy, pigmentary dystrophy, ness in a particular country or region. The The patients who attend for surgery are intoxication by synthetocal antimalarial agents, findings in the Central African Republic show elderly and poor. Some may have travelled for and so on.' that cataract and uncorrected aphakia two or three days from their homes on foot.