AIM To explore why emmetropisation fails in children who have strabismus. METHODS 289 hypermetropic infants were randomly allocated spectacles and followed. Changes in spherical hypermetropia were compared in those who had strabismus and those who did not. The effect of wearing glasses on these changes was assessed using t tests and regression analysis. RESULTS Mean spherical hypermetropia decreased in both eyes of “normal” children (p<0.001). The consistent wearing of glasses impeded this process in both eyes (p<0.007). In the children with strabismus, there were no significant changes in either eye, irrespective of treatment (p>0.05). CONCLUSIONS In contrast with normal infants, neither eye of those who had strabismus emmetropised, irrespective of whether the incoming vision was clear or blurred. It is suggested that these eyes did not “recognise” the signal of blurred vision, and that they remained long sighted because they were destined to squint. Hence, the children did not squint because they were long sighted, and glasses did not prevent them squinting.

In a sample of children used to assess the value of optical correction of hypermetropia from the age of 6 months the refraction of the most hypermetropic meridian frequently became less than 3.5 D as the children grew. When this occurred, the incidence of squint was significantly less (p less than 0.001) and the last known acuity after treatment was significantly better (p less than 0.001) than when it did not. This process of emmetropisation appears to have been impeded by the consistent wearing of hypermetropic spectacle correction from the age of 6 months.

Children who were abnormally hypermetropic at the age of 6 months were randomly allocated treatment with spectacles or no treatment. The eventual incidence of squint was the same in both groups (approximately 24%). The last known visual acuity of the two groups was not significantly different either. Therefore there is no indication to screen infants with a view to preventing squint/amblyopia by optical correction of hypermetropia. If, however, the children allocated treatment are divided into two subgroups--those who wore glasses consistently and those who probably or certainly did not do so--the incidence of squint was the same, but the last known acuities of those who consistently wore glasses may be better than those who did not do so. This suggests that it may yet prove possible to prevent severe amblyopia.

Retrospective analysis of a selected sample of children who presented with convergent squint has shown that abnormal meridional hypermetropia (3.5 D or more) at age 1 was the principal factor associated with severe amblyopia (6/24 or less) remaining after conventional treatment. Neither the reported age of onset nor delay in presentation influenced the final visual outcome.

whowereabnormally hypermetropic attheageof6months wererandomly allocated treatment withspectacles ornotreatment. Theeventual incidence ofsquint wasthesame inbothgroups (approximately 24%). Thelast knownvisual acuity ofthetwogroups wasnot significantly different either. Therefore there isnoindication toscreen infants withaview topreventing squint/amblyopia byoptical correction ofhypermetropia. If, however, the children allocated treatment aredivided into twosubgroups -those whoworeglasses con- sistently andthose whoprobably orcertainly didnotdoso-theincidence ofsquint wasthe same,butthelast knownacuities ofthose who consistently woreglasses maybebetter than those whodidnotdoso.Thissuggests that it mayyetprovepossible toprevent severe amblyopia.

The progress of 108 children who were identified by the vision screening programme in school as having defective vision (excluding those with puberty onset myopia) was reviewed. Treatment of these children resulted in improvement in visual acuity of the worst eye (two lines or better) for 16 children. Eighteen children had severe amblyopia (6/24 or worse). Among these the vision of only five was improved by treatment. Two thirds of the children had refractive errors in the better eye which required correction. It seems sensible to identify and treat children with bilateral refractive errors, but the need to treat children with lesser degrees of amblyopia is questioned.

Spectacle prescribing among 10-year-old children SIR, Your editorial in the December issue of the BJO uses my paper' to draw inferences which the data published in it cannot support.The data do strongly suggest that over- prescribing of spectacles is common in children but provide no information on who was responsible for these pre- scriptions.

In this series amblyopia, uncorrectable by spectacles and occlusion, was highly likely (48%) if a child had +3.50 or more dioptres of meridional hypermetropia at age 1 year. 45% of children with this refraction also had a squint. All those who remained with severely defective acuity in spite of treatment had either +3.50 or more dioptres of meridional hypermetropia or 4 or more dioptres of meridional myopia at age 1 year. These children were identifiable in the 3.7% of the population at age 1 year who showed high refractive errors. Squint as such was not so accurately predictable. Of those children with squint 71% had less than +3.50 dioptres of meridional hypermetropia at age 1 year--an incidence of 4.4% of the population. Apart from two 'congenital myopes' only 16% of these had residual amblyopia after treatment, and their last known acuity was never less than 6/12. Astigmatism in infancy or later is not significantly associated with squint or amblyopia.

Spectacle correction of unusually hypermetropic refractions from age 1 year did not reduce the incidence of squint or amblyopia, nor did it lead to a reduction in the severity of residual amblyopia after subsequent occlusion.

The results of 501 day-case cataract extractions are presented. This is a safe way to manage an operation for which there will be an increased demand. Only 13% of these patients stated that they would have preferred to stay in hospital after surgery.

Medical treatment followed by bilateral simultaneous iridectomy appears to be an effective basis for managing a patient who presents with acute glaucoma. Admission to hospital is seldom necessary. There was minimal evidence that delay in starting treatment caused more sight to be lost, but as the patient's age increased the prognosis for recovery of sight in an affected eye decreased quite significantly. The long-term prognosis for the sight of an individual patient who has had prophylactic iridectomy in the unaffected eye is excellent.

Cycloplegic refraction of 1-year-old children is technically possible and is acceptable to mothers as a method for screening children for visual defects. The range of refractions found in a sample of 186 1-year-old children is reported. Prediction of which children are significantly at risk for squint and/or amblyopia is possible on the basis of refractions at age 1 year according to the criteria selected for an 'abnormal' refraction. Bilateral hypermetropia and/or astigmatism or anisometropia at age 1 year was significantly (P less than 1 in 10 000) associated with a child eventually being found to have squint or amblyopia. Both the age of screening and criteria of abnormality will probably need modification. +2.50 or more D hypermetropia in any one meridian of either eye at age 1 year was even more significantly (P = 0.000 000 05%) associated with squint and/or amblyopia. The possibility that meridional hypermetropia could be the basic defect in squint and amblyopia is discussed.

Follow-up of a series of 221 children identified by the present methods of screening, and presenting consecutively with squint and/or amblyopia, shows that there has been no demonstrable improvement in the overall incidence and severity of amblyopia 3 or more years later.A new approach to the problem is required, and this might be based on the identification and treatment of amblyopia during the 'sensitive period'.

The refractions of 1648 children aged 11 to 13 months are reported. Atropine 1% was used for cycloplegia. 11.83% of the children had bilateral hypermetropia of +2.00 or more D. 13.23% of them had +1.50 or more D astigmatism in one or both eyes, and 6.5% had anisometropia. Anisometropia was significantly (P=0.000 001%) associated with bilateral hypermetropia, but even more significantly (P=0.000 000 4%) associated with astigmatism of +1.50 or more D in one or both eyes.

Cyclopentolate 1% is significantly less effective than atropine 1% at producing cycloplegia in 1-year-old children. If cycloplegic refraction is to be used for investigation or screening children for visual defects during the sensitive period, the more prolonged and profound cycloplegia following atropine could potentially have a disastrous effect on the development of vision. Cyclopentolate 1% would have to be used, and allowance made for its inadequacy as a cycloplegic.

215 preschool siblings of children presenting with squint/amblyopia were screened by refraction after cycloplegia. The presence of +2.00 or more D of spherical hypermetropia in both eyes, or +1.00 or more D sphere or cylinder of anisometropia was significantly associated (P=0.0779%) with that child being identified 2+ years later as having either squint or amblyopia or both. Astigmatism of +1.50 or more D in either eye was significantly associated with anisometropia (P=0.000 0013%). If bilateral hypermetropia of +2.00 or more DS and/or +1.50 or more D of astigmatism in either eye had been taken as criteria for abnormality (ignoring anisometropia), there was a more significant association (P=0.0025%) between refraction and squint/amblyopia in these siblings. Such a child had 4 times more chance of having a visual defect than one who had no error of refraction when screened. These findings suggest that an environmental factor such as blurred vision may be relatively more important as a cause of squint/amblyopia than a genetically determined neurological abnormality.

+2-00 to +2-75 dioptres of spherical hypermetropia in the more emmetropic of a pair of eyes is significantly associated with esotropia (P less than 0-001) and the presence of amblyopia (P less than 0-01). Anisometropia is not significantly associated with esotropia (P = 0-31) unless there is spherical hypermetropia of +2-00 dioptres or more in the more emmetropic eye (P less than 0-001). Hypermetropic anisometropia of +1-00 DS or +1-00 D.Cyl. is associated with the presence of amblyopia (P less than 0-001). In the absence of esotropia there is also a significant association between the amount of anisometropia and the initial depth of amblyopia (P less than 0-01). The additional presence of esotropia increases the depth of amblyopia further (P less than 0-05) but not the incidence of amblyopia (P greater than 0-30). The level of significance of the association of refractive errors with squint/amblyopia was itself significantly higher (P less than 0-01) than that between a family history of squint or "lazy eye" on the one hand and squint and/or amblyopia on the other hand. 72 +/- 3% of all cases of esotropia and/or amblyopia in this sample of children had a refractive error of +2-00 DS or more spherical hypermetropia in the more emmetropic eye, or +1-00 D. or more spherical or cylindrical anisometropia. Since there is a close association between the refraction and how, when, and whether a child presents with squint and/or amblyopia, it would seem reasonable to reconsider refraction as a basis for screening young children for visual defects.

A consecutive series of 140 children was observed after strabismus surgery. All the postoperative problems are attributable to general anaesthesia, vomiting and drowsiness being the principal ones. Respiratory difficulties were unusual. There is no reason to keep a healthy child in hospital for longer than one night, and day case strabismus surgery appears to be safe if (1) an experienced doctor gives the anaesthetic, (2) there is adequate supervision for 3 to 4 hours after surgery, (3) the appropriate district nurse is forewarned that a child is returning home after general anaesthesia, and (4) facilities are available to retain a child in hospital if a problem arises before discharge. Signs of emotional trauma may be less in children treated as day cases than in those hospitalized for one or more nights.