We conducted a prospective, planned study of argon laser panretinal photocoagulation (PRP) in ischemic central retinal vein occlusion (CRVO) over a 10-year period in 123 eyes. On comparing the lasered eyes versus the nonlasered eyes, there was no statistically significant difference between the two groups in the incidence of development of angle neovascularization (NV), neovascular glaucoma (NVG), retinal and/or optic disc NV, or vitreous hemorrhage, or in visual acuity. Our study, however, did show a statistically significant (P = 0.04) difference in the incidence of iris NV between the two groups, with iris NV less prevalent in the laser group than in the nonlaser group, but only when the PRP was performed within 90 days after the onset of CRVO. The other parameter which showed a statistically significant difference between the two groups was the peripheral visual fields-the laser group suffered a significantly (P less than or equal to 0.03) greater loss than the non-laser group. We discuss the implications of these findings in light of the natural history of ischemic CRVO and of ocular NV. Since the original rationale for advocating PRP in ischemic CRVO was the proven beneficial effect of PRP on ocular NV in proliferative diabetic retinopathy, we also discuss the disparities in the disease process between ischemic CRVO and proliferative diabetic retinopathy and in their responses to PRP.

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A large amount of research has been done on toxoplasmosis in the last 30 years, and the world-wide incidence of the infection, and its clinical manifestations, are recognized and documented in an extensive literature. New discoveries concerning the life-cycle of the organism (Frenkel, I970; Hutchison, Dunachie, Siim, and Work, I970) promise to solve many of the problems of the transmission of infection and will give added stimulus to epidemiological studies. In the field of ophthalmology the importance of toxoplasmosis is now established, but some problems still remain.The ocular lesions in infants with congenital toxoplasmosis are well recognized as pathogenic, but whether similar chorioretinal lesions in adults, although now acknowledged to be due to toxoplasmosis, result from recurrences of congenital infection or follow a postnatally acquired infection is still controversial. Other types of uveitis have been attributed to toxoplasmosis, and if this is correct it is important to recognize such cases. The present study attempts to clarify these problems by a review of the relevant literature supported by clinical studies in patients with uveitis. A further problem which will be discussed is whether congenital toxoplasmosis results from a chronic maternal infection or from one acquired during pregnancy: although this is not strictly an ophthalmological problem, ophthalmologists are often asked to advise on the prognosis for future pregnancies. Review of the literatureNo attempt is made here to provide a comprehensive general review of the literature on toxoplasmosis, but a list of recent reviews is given in the Bibliography. Attention here will be concentrated on the incidence of ocular complications in acquired systemic infections with clinical manifestations, the evidence for acquired infection in cases of uveitis, and the type ofmaternal infection causing toxoplasmosis. INCIDENCE OF OCULAR COMPLICATIONS IN RECENTLY ACQUIRED TOXOPLASMOSISIn reviewing the literature on this subject, an immediate problem is that of deciding on the criteria which should be accepted as evidence ofinfection. Most authors have relied on one or a combination of three methods: the detection of high levels of antibody, particularly the demonstration of rising titres; the observation of organisms in biopsy specimens or tissue fluids; and the demonstration of infection in animals after the inoculation oftissue extracts.The demonstration in biopsy or post mortem specimens of organisms morphologically resembling Toxoplasma is not entirely reliable, as nuclear fragments (Duke-Elder, Ashton, and Brihaye-van Geertruyden, I953) and even pine pollen (Langer, I966) can cause confusion. Even if the organism

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SUMMARY Of the 745 available members of the population of Nain in Labrador 650 (87%) were screened for refractive errors and ocular disease. Refraction by retinoscopy was done in 553 and axial length measured by an optical method in 514. The results showed that the incidence of low degrees of myopia was higher in Inuit (Eskimos) and those of Mixed Inuit-Caucasian blood in the age groups 10 to 40 than in those over 40. 75% of the myopes came from 20 families in which myopia was present in 2 or more generations. Although there was no significant correlation between the refraction of parents and offspring, there were significant correlations between them for axial length. The axial lengths of the myopic eyes of the Inuit and Mixed populations were significantly longer than emmetropic and hypermetropic eyes. The younger members of the population were taller than their parents, and except in female Caucasians axial length showed a significant positive correlation with height. More myopes than emmetropes and hypermetropes achieved grade 8 or more in school. It is suggested that the increased incidence of myopia in the younger age groups might be due to environmental factors interfering with the process of emmetropisation in eyes with a genetic predisposition to myopia by virtue of inheriting a slightly longer eye. Better nutrition resulting in an increase in stature may also have had some influence.There are now a number of reports of an increased incidence of myopia in the younger generations of North American Indians and Inuit (Eskimos) in Canada and Alaska (Young et al., 1969;Cass, 1973;Boniuk, 1973;Morgan and Munro, 1973;Woodruff and Samek, 1977). Surveys of such populations have shown few cases of myopia in the older population but incidences of 30 to 80% have been found in the 15 to 35 age groups, suggesting that environmental rather than genetic factors are concerned.Data from routine eye clinics in Nain, Labrador, suggested that there was such an excess of myopia in this population, but as this apparent excess in the younger population might have been due to sampling errors it was decided to attempt a total population survey of refractive errors and other eye conditions in Nain during a regular 6-monthly eye clinic. The resident population of Nain, which lies at latitude 28 Inuit were away seal hunting and were not available for examination.Under the auspices of the International Grenfell Association and with the help and support of the Canadian National Institute for the Blind a team of ophthalmologists and a refracting optician visited Nain for 2 weeks in October 1977. The examinations were held in the Nursing Station, and in addition to the collection of data for the survey any necessary ophthalmic treatment was also provided. Patients and methodsThose willing to attend for examination were given appointments, usually on a family basis, and a data sheet was made out for each person. The name, age, sex, height, and weight were completed by the nurse, and the people were then seen by one of the ophthalmologis...

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THE comparatively few accounts of uveitis in children all agree that it is uncommon (Table I). This report concerns 150 cases of uveitis starting before the age of 16 years. Most of the children were below this age when first seen; although 5 were aged between 16 and 20 and 3 were over 20, there was good documentary evidence that the uveitis had started before the age of 16. The 150 cases represent 5 per cent. of the total of 2,890 referred to the Uveitis Clinic of the Institute of Ophthalmology in the period from 1956 to 1964. The proportion of children under 15 years of age in the population of England and Wales in 1951 was over 20 per cent., so that there are fewer cases of uveitis in children than would be expected from the age structure of the population. It is interesting that Davis (1953) found a similar proportion of cases of uveitis in children-21 out of a total of 400-and Kimura, Hogan, and Thygeson (1954) 5 8 per cent. of 810 cases of uveitis. TABLE I INCIDENCE OF UVEITIS IN CHILDREN Author~~~Total in No. of Age Group Percentage Author Series Children (years) of Total Blegvad (1941) 896 20 Under 15 2-2 Guyton and Woods (1941) 562 7 Under 10 1*3 59 10-19 8-8 Marchesani (1949) 451 17 Under 15 3-7 Davis (1953) 400 21 Under 16 5 0 Kimura, Hogan, and Thygeson (1954) 810 47 Under 16 5*8 Bennett (1955) 332 7 Under 15 2-1 Perkins (1961) 1,718 40 Under 1 1 2-3 169 11-20 9-8 The cases inevitably represent a selected group, as only those which were more severe and chronic are likely to have been referred for investigation. The methods of investigation used in the clinic have been described previously (Perkins, 1961).