(From Dysopia 3098 difficulter, and

Difficult sight; parorasis. Dr. Cullen places this genus of disease in the class locales, and order dysesthesiae, which he defines, depraved vision, so that objects cannot be seen, except in a certain degree of light, at a given distance, or in a particular position. He distinguishes five species. 1. Dysopia tenebrarum, ambylopia cularis: when a great light is required for distinct vision.

2. Dysopia luminis, amblyopia meridiana, when sight is most distinct in an obscure light.

3. Dysopia, called also amblyopia dissitorum, when objects must be very near to be seen.

4. Dysopia amblyopia, D. proximorum, when objects cannot be seen distinctly, if very near.

5. Dysopia lateralis, also called amblyopia lusco-rum, when objects are best discerned by a side view.

In the first case, the disease depends on weakness of sight; in the second from too great irritability of the organ. In persons whose hair is white, and the edges of the eye lids red, the pigment, usually black, is of a lighter colour, as in cats and the white rabbits. The rays of light are therefore not lost, as when the pigment is black; and strong light occasions pain. Every one has experienced, in a strong sunshine, the effect of

"Tenebrae per tantum lumen obortae."

The third and fourth species are the presbytia and myopia; and the fifth depends on some partial obfusca-tion of the cornea, or humours, or a partial paralysis of the retina.