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SUMMARY Clinical and histological studies of the outer eyes of newborn and adult female guineapigs were carried out together with histological studies of fetal eyes. Fine superficial corneal vessels, extending from the limbus, were seen in most newborn and adult eyes and were also present in histological preparations of fetal eyes. These vessels were therefore considered to be features of the normal guinea-pig eye. Masses of tissue composed of lymphoid cells, which were often organised into germinal centres, were found in the fornices of newborn and adult eyes. Smaller accumulations of lymphoid cells were found in fetal eyes, and this lymphoid tissue was therefore also considered to be a normal feature of the guinea-pig eye. In adult eyes mild but short-lived oedema or hyperaemia of the palpebral conjunctiva was quite common. There were no differences in the amounts of conjunctival cellular infiltration in these eyes compared with normal eyes, and these inflammatory changes were therefore not considered to be significant.

(Wang and Grayston, 1970;Treharne et al., 1971) has greatly facilitated the study of the TRIC agents responsible for hyperendemic trachoma of eye-to-eye transmission, and the TRIC agents of paratrachoma (both ocular and genital) of sexual transmission, with occasional transfer to the eye (Jones, 1975;Treharne et al., 1977).The microimmunofluorescence method has also been applied to the measurement of type-specific antichlamydial antibody in serum (Dwyer et al

(I967), has been used to recover laboratory-adapted isolates of TRIC agent from the infected eyes of simians (Gordon and others, I963) and of man (Magruder and others, I963).Studies recently completed in this laboratory on clinical specimens from genital or genitally-related ocular infections in London showed that isolation in irradiated McCoy cells is more sensitive for the detection and isolation of chlamydial agents than cultivation in the yolk sac of embryonated hen's eggs or inclusion-finding in Giemsa-stained scrapings (Gordon, Harper, Quan, Treharne, Dwyer, and Garland, I969; Dunlop, Hare, Darougar, Jones, and Rice, I969). It was also shown that TRIC agent could be isolated in the cell culture system from endemic trachoma in Iran, but the number of specimens tested was too small to give an assessment of the sensitivities of the two methods of isolation in relation to the finding of inclusions in conjunctival scrapings.Isolates of TRIC agent from endemic trachoma in the Middle East and the Far East have shown biological differences from TRIC isolates of genital origin in London, USA, and Taiwan (Alexander, Wang, and Grayston, I967; McComb and Bell, I967; Wang and Grayston, I970, 197!). It was, therefore, not clear whether the irradiated McCoy cell system could provide a satisfactory alternative to the yolk sac of embryonated hen's eggs for isolation of TRIC agent from endemic trachoma.This paper compares the results of isolation of TRIC agent in cell culture with those of isolation in the yolk sac of embryonated eggs from scrapings collected during a field study of trachoma in certain villages in Iran. It also relates these isolations to the findings of inclusions in conjunctival scrapings stained by iodine or Giemsa stain, and the results of microimmunofluorescence typing of the isolates.