Consecutive or secondary displacement of the lens is a well-recognized condition caused by stretching, inflammation, or degeneration of the zonule. Degeneration occurs with long-standing glaucoma, high myopia, retinal detachment, and particularly with a mature or hypermature cataract (Duke-Elder, I969).Lens displacement associated with pseudocapsular exfoliation has not been well described. Irvine (I940) reported two cases with tremulous lenses and two in which the lens dislocated when grasped with forceps; these were all complicated by vitreous loss and were taken from a series of 42 cases of glaucoma capsularis. He drew attention to the possibility of a weak zonule, a fluid vitreous, and a friable capsule.Gradle and Sugar (I 940) described 43 eyes with pseudocapsular exfoliation and concluded that, because of zonular degeneration, spontaneous dislocation might occur in advanced cases. There were four attempted intracapsular extractions and in three of them there was vitreous loss. Sugar (I957) quoted two cases of spontaneous dislocation and several in which dislocation occurred during surgery in a series of I54 cases of pseudocapsular exfoliation and concluded that there was a tendency to spontaneous and operative dislocation.Gifford (I958) quoted three cases with spontaneous dislocation in a series of 62 cases. In 22 cataract extractions he noted that the lenses dislocated easily without rupture of the capsule, vitreous loss, or fluid vitreous, indicating that the zonule was more friable than normal.Tarkkanen (i962), in a review of 418 patients, noted nine eyes with displaced lenses out of a total of 635 eyes with pseudocapsular exfoliation. Present investigationsDuring a 2 year clinical study of lens displacement nineteen patients with 22 displaced lenses in association with pseudocapsular exfoliation have been seen. The clinical manifestations of these cases and the results of cataract surgery in eight of them are described below. MaterialDuring I968 and I969 all cases with displacement of the lens seen at the Eye Department of Baragwanath Hospital and the St. John's Eye Hospital, Johannesburg, were referred to the author for clinical assessment, treatment, and follow-up. Of these patients go per cent. are Southern Bantu, the remaining I0 per cent. being Asian or Coloured. 238 eyes with lens displacement have been seen to date, and 22 associated with pseudocapsular exfoliation were seen in nineteen Bantu patients.

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Pseudocapsular exfoliation occurs in most races and countries but appears to be particularly common in Norway and in the Eastern European and Mediterranean countries. It is rare in American Negroes, only two cases having been reported (Gradle and Sugar, 1947), and in Negroes in the West Indies (Connell, I970), and has not been reported in Negroes elsewhere outside South Africa (Bartholomew, I970; Luntz, I970). The geographical distribution of exfoliation was reviewed by Aasved (i969), who concluded that many of the differences in occurrence and prevalence are due to the nature of the samples and methods used. He found prevalence rates, in three groups of subjects over 60years old, of 6 3 per cent. in Norway, 4 0 per cent. in Germany, and 4.7 per cent. in England, using similar samples and identical methods of examination. The apparent rarity of exfoliation in Negroes throughout the world, apart from the South African Bantu, promoted these efforts to obtain more information about the occurrence and prevalence of exfoliation in the various Bantu tribes, who have different racial and genetic backgrounds, live under widely different climatic conditions, and are at different stages in development from a primitive rural to an urban way of life. Material and methods (A) From the Eye Department of Baragwanath Hospital and The St John Eye Hospital in Johannesburg: (i) ioo consecutive patients undergoing cataract extraction were examined for exfoliation with a slit lamp, the pupils being fully dilated. (2) During a 3-month period 625 consecutive new ophthalmic outpatients, over 30 years of age, were examined with a slit lamp. The pupils were dilated only if otherwise indicated, or to confirm suspected exfoliation. Some early cases will have been missed. (3) 192 patients were referred for assessment to the glaucoma clinic. All were examined on a slit lamp with dilated pupils. 63 of these were examined personally; in the remainder information was taken from case histories. All these patients were South African Bantu of various tribes, mainly living in the suburban districts ofJohannesburg. (B) Field tours were undertaken for the South African Bureau for the Prevention of Blindness among various rural Bantu tribes, between I968 and I97 I. The diagnosis of exfoliation was made under unfavourable conditions using a torch, loupe, and ophthalmoscope and was thus confined to those with obvious well-established disease. 4,1 56 persons were examined in this way.

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