764 PERCY FRIDENBERG 



inflammatory/ processes in the light perceptive tissues of the choroid 

 and retina. A familial and hereditary grouping is always recognizable. 

 The symptom of hemeralopia which characterizes these affections as well 

 as many forms of vitamin privation or deficiency disease has a relation 

 to atypical pigment development, as well as to functional inferiority. 



Lack of Ocular Pigment. Albinism. In this markedly familial and 

 hereditary (Mendelian recessive) condition there is marked lack of pig- 

 ment in the iris and uveal tract, and in the complete cases non-develop- 

 ment of retinal pigment, as well. Nystagmus of the tremulous non-laby- 

 rinthine typo is common. In both, vision is markedly impaired by irri- 

 tation and dazzling, owing to the absence of a photostatic blind pro- 

 vided by the normal pigment layer at the back of the iris, intensified, in 

 complete albinism, by a developmental arrest in the light-perceptive 

 elements of the retina. According to Scherl, the first appearance of 

 ocular pigment is connected with the development of the blood-vessels, so 

 that defective pigmentation of the retina indicates an arrest at the 

 earliest stage of embryonic existence, while albinism limited to the iris 

 and choroid is explained by primary progress and a later standstill at the 

 stage normally found in the newly born. 



In albinism the lashes and brows are colorless or a very light blonde, 

 not white as in senility. The hair is also extremely light and the skin 

 thin and delicate. The visual disturbances range from rapid fatigability 

 of the retina and sensitiveness to bright light with slight defect of central 

 vision, to marked amblyopia, but always with a normal visual field and 

 good color perception. The iris appears pink, lilac, or whitish -yellow, 

 depending largely on the way in which light strikes the eye. The pupil 

 reacts very briskly, is generally contracted and slightly rigid. Blepharo- 

 spasm is a common symptom, as is the photophobia which it naturally fol- 

 lows. Hyperemia of the skin of the lids and of the ocular conjunctiva is 

 generally present. Albinism is commonly but not at all invariably asso- 

 ciated with psycho-neurotic inferiority and with developmental arrests. 



Ocular Melanosis. Unusually deep pigmentation, especially of the 

 sclera is found in the Negro race and in many individuals of dark complex- 

 ion in Caucasian races. We speak of melanosis, in distinction to this mark- 

 ed but even distribution, when pigment spots or patches are found on an 

 otherwise evenly and not excessively pigmented sclera, conjunctiva, or 

 iris and choroid, or as an extreme rarity, on the optic disc. In the iris 

 it appears as a distinct mass at the minor or major circle or at the sphincter 

 margin or scattered over the surface of the iris in spots or lines which are 

 generally irregular but often show a certain symmetrical arrangement 

 in the two eyes. 



Ileterochromia. Occasionally, one half of the iris is light gray or blue 

 while the other half is brown. Bilateral heterochromia (dikorus) is less 



