Britishlournal ofOphthalmology, 1991,75,425-429 425 Childhood blindness in the Republic of Ireland:

a national survey Br J Ophthalmol: first published as 10.1136/bjo.75.7.425 on 1 July 1991. Downloaded from

Michael Goggin, Michael O'Keefe

Abstract population of the Republic aged under 16 is We completed a national study of blindness in 1094932 (at the last census in 1986). These children under 16. Approximately 80% of the figures would suggest that there are about 220 blind children (that is, with vision of 3/60 or blind children under 16 in the Republic at less) in the Republic of Ireland (172 children) present. Information on childhood blindness were seen, 93 males and 79 females. The was not available in the Republic before this survey was carried out between July 1989 and survey. June 1990. It is the first such study to be carried We set out to identify and record all blind out. Ninety seven (56%) children had lesions children in the Republic of Ireland, and to due to factors acting before the perinatal institute a national live register ofblind children. period. Of these, 28 (16% of the total number surveyed) had lesions due to genetic causes; 69 (40%) had lesions due to factors operating in Materials and methods the prenatal period other than genetic factors. Forty six (27%) had lesions due to factors SOURCES OF REFERRAL acting in the perinatal period. Twenty two A national survey of blind children under 16 (13%) had lesions due to factors acting in years old on 1 July 1989 (that is, born on or after childhood. (4% could not be categorised in this 2 July 1973) whose best corrected vision was 3/60 way). The commonest single primary diag- or worse in their better eye was carried out. noses were birth asphyxia in 19 (11%) cases Patients were sought by several methods. All and of prematurity in 19 (11%) consultant ophthalmologists were circularised. cases. The schools for blind and physically handi- capped, the mental handicap institutions, the social service and educational bodies responsible This report outlines the major findings of a for care of the blind were contacted nationwide national survey ofblind children in the Republic to refer suitable patients and also asked for any of Ireland. A survey carried out in Northern records ofpatients known to them who fitted the

Ireland in 19761 found 142 patients under 21 criteria. They provided comprehensive lists of http://bjo.bmj.com/ years blind by World Health Organisation such cases. (WHO) standards - that is, of 3/60 or less.2 This represents about 0-02% of the under 21 population at that time. The current EXAMINATION OF PATIENTS We examined all the patients. A history was' taken when possible from a parent or a respon-

Table I Ophthalmic diagnoses by category sible adult. This included a family history, a on September 27, 2021 by guest. Protected copyright. history of the pregnancy, birth, and early post- Category: chromosomal/genetic: 28 cases natal period, and any relevant previous medical Leber's amaurosis 3 Anophthalmos 2 Cortical blindness 3 Optic atrophy 2 and ophthalmic history. Confirmatory medical hypoplasia 3 Rothmund-Thompson 2 data were sought when necessary from the Albinism 3 Microphthalmos/coloboma 2 3 Buphthalmos 1 relevant medical institutions. Leber's optic atrophy 2 Usher's syndrome I The best corrected visual acuity was measured pigmentosa 2 Stargardt's syndrome 1 Metabolic retinopathy 2 by the appropriate method for age, ability to co-operate, and level ofintelligence. When poss- Category: prenatal: 69 cases 25 Congenital toxoplasmosis ible this was by Snellen chart for distant vision. Optic atrophy 21 Peters's anomaly When the child was too young for the use of Cortical blindness 10 Buphthalmos Pigmentary retinopathy 6 subjective tests ofvisual acuity, an assessment of Microphthalmos/coloboma 5 Motor the ability to fixate was made. Patients with Department of Congenital rubella 5 Bilateral Ophthalmology, Cararact 5 (? cause) central unsteady, unmaintained fixation or worse Children's Hospital, Anophthalmos 4 were deemed eligible for registration. When Temple Street, Dublin 1, and UCD Department of Category: perinatal: 46 cases possible with the more co-operative patients and Ophthalmology, Mater Retinopathyofprematurity 19 Cortical blindness when the patients were able to attend the Misericordiae Hospital, Optic atrophy 14 Optic nerve hypoplasia Children's Hospital more accurate measure- Eccles Street, Dublin 7 Category: childhood: 22 cases .ments were made by Forced Choice Preferential M Goggin Optic atrophy 9 Uveitis (? cause) M O'Keeffe Retinoblastoma 8 Looking techniques. Ability to distinguish a Correspondence to: Cortical blindness 3 pattern of 1-5 cycles/degree or less at 38 cm (that Michael O'Keeffe, FRCS, Category: unassigned: 7 cases is, an approximate Snellen equivalent of 3/60 or Department of Paediatric Tractional retinal detachment 2 less) was taken as the criterion for inclusion in Ophthalmology, Children's Optic atrophy ?cause 2 Hospital, Temple Street, Optic nerve hypoplasia with hormone deficiencies 1 the study. Electrophysiological examinations Dublin 1. ? Viral retinal pigment epitheliitis 1 were carried out when necessary. Accepted for publication Isolated microphthalmos 1 20 December 1990 A full ophthalmic examination was under- 426 Goggin, O'Keeffe

taken in every case. A systemic examination was study) and were associated in the same patient. carried out by a paediatrician at the Children's Optic nerve hypoplasia was associated with

Hospital ifit was required to establish a diagnosis. absent corpus callosum, fetal alcohol syndrome, Br J Ophthalmol: first published as 10.1136/bjo.75.7.425 on 1 July 1991. Downloaded from Laboratory investigations were also carried out if twin-to-twin transfusion, spina bifida, and septo- necessary for a diagnosis. X rays, CT scanning, optic dysplasia. Rubella syndrome was diagnosed nuclear magnetic resonance (NMR) imaging, in five, the youngest being 11 years old. A further and ultrasound examination were undertaken for five each had colobomata or non-hereditary the same purpose. cataract. One child with colobomata was thought All the relevant data were collected on data to have Goltz syndrome, but because the evidence sheets and put in a computer database for future was inconclusive she was categorised as having a retrieval. coloboma of prenatal cause rather than heredi- tary (Goltz syndrome is thought to have an X-linked pattern of inheritance). Results A total of 172 blind children were seen. There were 93 males and 79 females, a ratio of 118:1. PERINATAL Seventy nine (46%) of the children registered A total of 46 (27%) cases were in this group. were aged under 5, 39 (23%) were aged 5 to 10 Nineteen cases of retinopathy of prematurity years inclusive, and 54 (31%) were 11 or over but were seen, 14 of optic atrophy, and 11 of cortical under 16 on 1 July 1989. blindness. The latter two diseases were fre- An ophthalmic diagnosis was recorded for all quently seen together in the same patient and the children seen. A systemic diagnosis was also caused by hypoxic ischaemia from birth trauma. recorded in 112 cases (65%). The diagnosis was Nineteen cases of hypoxic ischaemic damage assigned to a category, genetic or chromosomal, causing blindness were seen. In nine further prenatal, perinatal, or childhood depending on cases there was documented birth trauma, but the aetiology. A complete list of diagnoses by examination revealed optic nerve hypoplasia category is given in Table 1. Many children had associated with the primary cause of blindness several related diagnoses. (namely, cortical damage or optic atrophy usually), implying some underlying prenatal abnormality. CHROMOSOMAL OR GENETIC Twenty eight children (16%) had diagnoses that fell into this group. Leber's amaurosis, albinism, CHILDHOOD and cortical blindness associated with genetic or Twenty two patients (13%) had lesions occurring chromosomal disorders were the most frequent after the perinatal period. Eight of these had diagnoses, with three cases each. The lesions bilateral retinoblastoma, for which seven were causing cortical blindness were an extra chromo- treated by bilateral enucleation. The eighth some 15, Pelizaeus-Merzbacher disease, and a received radiotherapy to the second eye, which http://bjo.bmj.com/ peroxisomal disorder. Two cases of Rothmund- became blind subsequently. It is likely that some Thompson syndrome were discovered. Two of these bilateral cases have a genetic aetiology. cases of retinopathy associated with metabolic However, none had affected parents, siblings, or disorders were seen, one with Tay-Sachs disease more distant relatives. None were shown to have and the other with a peroxisomal disorder. One an abnormal karyotype. In the absence of firm case of Patau's syndrome with bilateral anoph- evidence to suggest a genetic background they thalmos was seen. A deletion of the short arm of have been put in this category. Nine showed on September 27, 2021 by guest. Protected copyright. chromosome 11 was associated with , optic atrophy, six following infective encephalo- , and cataract in one child. pathies (two of whom also had cortical vision Dicarboxylic aciduria was associated with optic defects) and three secondary to intracranial atrophy in another. tumours. One other child was cortically blind In three families a history of parental consan- secondarily to Reye's syndrome. One case of guinity was obtained (1 74%). In two ofthese the blindness due to self-injurious behaviour parents were first cousins and in the third family associated with mental handicap was seen. second cousins. The diagnoses were bilateral Finally, one child with Down's syndrome was anophthalmos and optic nerve hypoplasia in the seen with bilateral phthisis following bilateral first two cases, and optic atrophy in a back- retinal detachment. ground ofhydrocephalus from aqueduct stenosis in the third. CATEGORY NOT ASSIGNED Seven cases (4%) could not be assigned to the PRENATAL above categories owing to difficulties in arriving These were cases with lesions occurring before at specific diagnoses. Two had tractional detach- the perinatal period that could not be classified as ments ofunknown aetiology. One had a pigmen- chromosomal or genetic: 69 cases (40%) fell into tary retinopathy that may have been secondary to this category. The most frequent findings here a viral retinal pigment epitheliopathy. were optic nerve hypoplasia in 25 cases and optic atrophy in 21. Cortical blindness was diagnosed in 10 cases. Many of the latter two diseases were MENTAL HANDICAP secondary to systemic abnormalities such as Seventy seven of the 172 cases seen had mental hydrocephalus or metabolic disorders (many of handicap (44 5%). Of those, six had profound which were not fully elucidated at the time ofthe handicap, 23 severe, nine moderate, and four Childhood blindness in the Republic ofIreland: a national survey427

mild. The other 35 had not had formal measure- Table 2 Visualfunction by method ofassessment ment of the intelligence quotient at the time of Fixation assessment: 105 cases the survey since they were too young. Most ofthe pattern Asymmetrical vision Br J Ophthalmol: first published as 10.1136/bjo.75.7.425 on 1 July 1991. Downloaded from latter cases would have been functioning in the Symmetrical vision (vision in better eye) ucusum 72 2 range as 'severe' assessed by those caring for cusum 28 3 them. Seventy five children had developmental Snellen visual acuity (including NPL, PL, HM, CF): 64 cases delay, usually associated with either mental or Asymmetrical vision physical handicap or both. Twenty six of those Symmetrical vision (vision in better eye) NPL 23+ 0 with developmental delay, however, were too PL 14 (3 ?PL) 10 young to have had a full assessment of their HM 2 3 CF 1 0 intelligence. Twenty three ofthis 26 had systemic 1/60 2 2 diagnoses (such as profound ) that 3/60 2 2 made the confirmation of mental handicap at a Forced choicepreferential looking: 3 cases later date likely. This would then give a total of Asymmetrical vision Symmetrical vision (vision in better eye) about 59% with possible mental handicap. 1-5 cycles/degree 0 1-3 cycles/degree 0 0-32 cycle/degree 0 VISUAL FUNCTION ucusum=uncentral unsteady unmaintained. For the purposes of inclusion in the survey and cusum=central unsteady unmaintained. NPL=no perception oflight. the register of blind children visual function was PL=perception oflight. assessed in one of several ways by means of the HM=hand movements. CF=counting fingers. most suitable for the child being examined. In Where vision was asymmetrical, the vision in the better eye is 105 cases this was based on the fixation pattern. recorded in this table. Snellen acuity, or perception of light, hand movement, or finger counting were used in 64, people). The main causes of blindness found and three were assessed by forced choice pre- were cataract and uncorrected , non- ferential looking techniques. Visual function was trachomatous corneal opacity and , the same in both eyes in 150 children. In 72 cases and . Similar studies have been pub- this consisted of 'uncentral', unsteady, and un- lished from Malawi in the past6 and more maintained fixation (ucusum) (probably repre- recently from Kenya.7 Two articles in 1989 senting a Snellen vision of less than 6/60). A documented trends in blind registration in two further 28 had central, unsteady, and unmain- health authorities in the UK.89 Though these tained fixation (cusum) (roughly equivalent to a latter studies contain accurate and interesting Snellen acuity of 6/60.3 Twenty three had no information, it cannot be assumed that they perception of light (NPL), 14 had definite light reflect accurately the make-up of the blind perception (PL), and three had possible PL. population of either the relevant health authori- Two patients had a Snellen acuity of 1/60 in both ties or the UK as a whole, because the statistics eyes and two had 3/60. One child could count are not derived from a random sample of the http://bjo.bmj.com/ fingers and two had hand movement vision population but a highly selected one, namely, bilaterally. Three children had their vision those registered as visually impaired in specific assessed by preferential looking techniques, and areas. Our survey found 108 blind children not their resolving power was estimated at 1-5, 1-3, previously registered on the Blind Register main- and 0-32 cycles/degree testing at 38 cm respec- tained by the National Association for the Blind tively. Visual function was asymmetrical in 22 in Ireland out ofa total of 172 blind children seen children. Ten had PL in the better eye, three had (that is, 62-79% were not previously registered). on September 27, 2021 by guest. Protected copyright. HM, three had cusum, two had ucusum, two had Reliance on registered data is therefore suspect. 1/60, and two had 3/60, all in the better eye For the statistics from any register to be ofuse (Table 2). the register must actively seek out those visually impaired people in the population, document them accurately (this involves ontinued review SURGERY of those registered), and delete those who die or Eleven patients underwent cataract extraction or whose acuity improves to a level greater than that clear extraction as part ofanother procedure. at which they would qualify for registration - Nine had enucleations, seven bilateral, six for that is, a 'live' register. retinoblastoma, and one for buphthalmos. Five Our is an to had had corneal transplantations. Three had study attempt document vitrectomies and two conventional retinal detach- ment surgery. Thirty one patients had had Table 3 Surgery carriedout on children registered (number of surgery of some description (Table 3). procedures) Cataract extraction/clear lensectomy 11 Enucleation 9 (7 bilateral) Corneal transplant 5 Discussion Vitrectomy 3 It has been pointed out in the past that several Conventional retinal detachment surgery 2 Squint surgery 2 African and other third world countries have Trabeculectomy 2 more accurate statistics on the prevalence of Radiotherapy 2 Probing ofnasolacrimal duct 1 blinding disease than the developed nations.4 Peripheral iridectomy I Last year the results of the national survey of Correction ofentropion I YAG laser capsulotomy I blindness and low vision in The Gambia were Removal of I published.5 A large random stratified sample of Total patients 31 this country's population was examined (8174 428 Goggin, O'Keeffe

accurately the population of blind children (with genital abnormalities. In European studies in the vision less than or equal to 3/60 in the better eye) mid 1970s in Holland, Belgium, Norway, and ofIreland them all Denmark optic atrophy, cataract, congenital

in the Republic by examining Br J Ophthalmol: first published as 10.1136/bjo.75.7.425 on 1 July 1991. Downloaded from ourselves. This information is now incorporated abnormalities, and retinopathy of prematurity in the Blind Register as the start ofa live register. figured largely also, but many cases of tapeto- Since such measures ofvisual function as fixation retinal dystrophy were seen." Foster's review of pattern or even preferential looking do not worldwide statistics concluded that in the always correspond with eventual Snellen acuity, developed world childhood blindness was largely some children are registered who will turn out due to hereditary causes and factors operating at not to be 'blind' by the Snellen criteria set out the time of birth (such as hypoxia).'2 Of note is above. However, this is a live register, and when his comment that better care of preterm infants these children come for review they can be may have led to an increase in visual handicap. deleted. Because of this we recommend patients In countries where there are medical services should be registered as soon as it is established of intermediate quality intrauterine infections, that their level ofvisual function, as measured by in particular rubella, are an important prevent- the most appropriate test available in the in- able cause of blindness. In areas where the dividual case, meets the criteria set out. Reliance medical services are poor, such as many rural and on Snellen acuity testing as a criterion for blind urban slum areas in Asia, Africa, and parts of registration is inappropriate for the preverbal South America, , measles, child or for the mentally handicapped. and the lack of ophthalmic services are res- It is interesting to note that a similar study was ponsible for 50-75% of childhood blindness. carried out in Northern Ireland in the mid 1970s. Bryars's study in Northern Ireland of visually The ascertainment rate was estimated to be handicapped children' showed that 95% of his similar to ours, namely 80%. cases had pre- or perinatal causes, and 51% were In Britain several monographs have been genetic in origin. Of note is the fact that birth published by the Department of Health and injury caused only 2% of his cases. However, Social Security on blindness and partial sight. In 18% were attributed to optic atrophy, with no recent years these have been confined to the adult comment on the primary diagnosis, and presum- population; the most recent containing informa- ably some of these are as a result of birth tion on children was published in 197910 and asphyxia. He does note a high incidence of optic referred to the years 1969-76 in England. The atrophy among the mentally handicapped. information contained in this report is derived In this survey 28 out of 172 (16-28%) had from blind registers and not active ascertainment genetically determined disease. This figure is of all cases in the population. The statistics considerably less than those quoted by therefore must not be taken as an accurate Baraitser'3 and Jay.'4 Sixty nine cases, however, reflection of the actual incidence and prevalence had causes of their disease that were categorised of the conditions described, but merely as the as prenatal. Many ofthese had conditions which, best available. Our survey, however, has though not definitely genetic in origin, may have http://bjo.bmj.com/ attempted to assess the whole population so that some genetic background in a multifactorial the statistics produced are as accurate as is aetiology, such as optic nerve hypoplasia. It is possible. possible that our strict criteria for inclusion in The criteria in this study for 'blindness' are the genetic category, namely an accurate diag- stringent by most standards. Legal blindness in nosis with proved genetic aetiology, may have the Republic ofIreland is usually taken to be 6/60 decreased our total. An associated systemic diag- or worse in the better eye, or 200 field or worse in nosis was made in 112 cases (65%). Little on September 27, 2021 by guest. Protected copyright. the better eye. However, the WHO definition is reference is made in the DHSS reports (or any of 3/60 or less in the better eye.2 For many children the other large surveys) to this important aspect a vision of 6/60 does not preclude education by of the subject. Without this information the visual methods. Snellen acuity cannot be significance of a morphological diagnosis such as measured in preverbal infants or in the more optic atrophy cannot be assessed, since the severely mentally handicapped. Yet many blind aetiology is so diverse. children fall into these categories. For this reason The commonest morphological diagnoses we have set out different, but roughly equivalent, (which often coexisted in the same patient) were criteria for registration in these groups. An exact optic atrophy (48 cases), optic nerve hypoplasia correlation between Snellen acuity and fixation (39 cases), and cortical blindness (27 cases). The pattern or even preferential looking measure- commonest single causative factor in the first and ments cannot be made, but, as long as those last of these was birth asphyxia (19 cases). The registered are subject to continual review, those prominence of optic nerve hypoplasia in this list patients who with maturation can subsequently probably indicates increased recognition of this be measured by Snellen methods will have this sometimes subtle condition. A small number carried out and inappropriate registration have only this isolated abnormality (3 cases) but a altered. great many more are associated with other con- The major causes ofblindness in children have genital abnormalities, such as albinism, hydro- been estimated in several publications. The most cephalus, agenesis of the corpus callosum, and recent DHSS monographs shows that during septo-optic dysplasia. Retinopathy of pre- 1969-75 in England the commonest causes of maturity is still a major cause ofchildhood blind- new registration in children under 16 were optic ness, seen here in 19 children. However, none of atrophy and cataract (no comment is made on the the children so affected were born after Septem- primary systemic diagnoses in these groups, ber 1987, so perhaps the management of the which can vary considerably) followed by con- condition is improving. Recent experience in the Childhood blindness in theRepublic ofIreland: a national survey 429

field ofretinal cryotherapy in this condition gives One of the chief reasons for undertaking this reason for hope, suggesting a reduction by a half survey was to upgrade the quality of the oph- in the numbers of eyes with an unfavourable thalmic and background medical data on the outcome. " current blind register and to register as many Br J Ophthalmol: first published as 10.1136/bjo.75.7.425 on 1 July 1991. Downloaded from Eleven children were found to be blind owing new blind children as possible. The data col- to tumours. Eight had blinding bilateral retino- lected will now constitute the start of a live blastoma, and three more had intracranial register to be maintained by the National Council tumours causing damage to the anterior visual for the Blind in Ireland. A live register would pathways (a craniopharyngioma, a hypothalamic provide information on incidence and prevalence astrocytoma, and an optic chiasm glioma). and demographic risk factors, and give invalu- The two commonest single primary causative able aid to researchers and to those who provide agents are prematurity and birth asphyxia, both services to the target population. with 19 cases (11% of the total each). It is important to mention that we did not come across any cases of blindness from bilateral untreated or poorly treated amblyopia. Only 1 Bryars JH. An investigation of the visually handicapped three cases ofblindness fromchildhood children in Northern Ireland. (Thesis submitted for the were seen. Rubella seems to have degree ofdoctor ofmedicine ofQueen's University, Belfast). (1977). been almost eradicated, the youngest patient (of 2 International classification ofimpairments, disabilities and handi- only five) was 11 years old. The pattern of caps. Geneva: World Health Organisation, 1980: 79-85. 3 Costenbader F, Blair DR, McPhail A. Vision in . diagnoses fits roughly into that seen in other Arch Ophthalmol 1948; 40: 438-53. western nations."2 44% of the children seen were 4 Johnson GJ, Minassian DC. Prevalance of blindness and eye disease: discussion paper. J R Soc Med 1989; 82: 351-4. mentally handicapped. This is similar to other 5 Faal H, Minassian D, Sowa S, Foster A. National survey of European studies. But if those with develop- blindness and low vision in The Gambia: results. Br J Ophthalmol 1989; 73: 82-7. mental delay and diseases likely to lead to mental 6 Chirambo MC. Blindness and in southern handicap are included the total is nearer 60%. Malawi. Bull WHO 1986; 64: 567-72. 7 Whitfield R, Schwab L, Ross-Degnam D, Steinkuller P, This can be explained by our confining our study Swartwood J. Blindness and eye disease in Kenya: ocular to the severely visually impaired. These children status survey results from the Kenya Rural Blindness Prevention Project. BrJ Ophthalmol 1990; 74: 333-40. tend to have a higher prevalence of mental 8 Thompson A, Du L, Rosenthal AR. Recent trends in the handicap." registration of blindness and partial sight in Leicestershire. BrJ Ophthalmol 1989; 73: 95-9. A large proportion of our cases were under 5 9 Grey RHB, Burns-Cox CJ, Hughes A. Blind and partial sight years (46%). This may be attributable to our easy registration in Avon. BrJ Ophthalmol 1989; 73: 88-94. 10 Department of Health and Social Security. Blindness and access to the three largest maternity units in the partialsight in England 1969-1976. Reports on Public Health country, all located in Dublin and all referring and Medical Subjects, 129. London: HMSO, 1979. 11 Schappert-Kimmijser J, Hansen E, Haustrate-Gosset MF, cases directly to our own paediatric ophthal- Lindstedt E, Skysgaard H, Warberg M. Causes of severe mology service. visual impairment in children and their prevention by the committee for special study of severe visual impairment in This study shows that almost 30% of the children of the International Association for Prevention of

causes ofblindness in this country are potentially Blindness. Doc Ophthalmol 1975; 39: 213-341. http://bjo.bmj.com/ 12 Foster A. Childhood blindness. Eye 1988; 2 (suppl): S27-S36. remediable - genetic causes (16%) through 13 Baraitser M. The genetics of childhood blindness. Hosp genetic counselling, retinopathy of prematurity Update 1981: 516-27. 14 Jay B. Causes of blindness in schoolchildren. BMJ 1987; 294: (11%), and birth asphyxia (11%) - and 40% 1183-4. cannot be tackled with present knowledge, com- 15 Cryotherapy for Retinopathy of Prematurity Cooperative Group. Multicentre trial of cryotherapy for retinopathy of prising those prenatal causes that have not yet prematurity: preliminary results. Arch Ophthalmol 1988; become amenable to treatment. 106: 471-9. on September 27, 2021 by guest. Protected copyright.