Concomitant esotropia of late onset; pathological report of four cases in siblings.

CONCOMITANT convergent squint usually begins during childhood. Cosse (1899) states that in 90 2 per cent. the onset occurs between birth land the age .of 5 years; Priestley Smith (1898) states that 300 out of 347 cases began during the first 5 years; Worth (1939) found that 70 per cent. of uniocular convergent squints began before the age of 4 years and that 88 per cent. of alternating squints began before the fifth year. Lagleyze (1913) believed that the average age at onset of convergent squint was 4 years and 3 months. Malbran (1953) states that it is rare for a convergent squint to begin after 6 years of age; of 353 cases, 298 appeared between birth and the fifth year. Scobee (1951) found that 93 per cent. began before the fourth year; Keiner (1951) that 576 of 656 convergent squints had begun before the sixth year; Nordldw (1953) that 92 per cent. of 518 cases had begun before the fourth year. Thus, the percentage of concomitant convergent squints beginning after the fifth year is small, and we must subtract from them cases of esotropia of paralytic origin that may, in the course of time, have evolved towards concomitance; these belong to an already defined clinical entity and will not be considered here. We shall refer exclusively to non-paralytic concomitant esotropia of late onset, the pathogenesis of which has been variously interpreted by different authors. Three clinical forms have been described: