The neural retina occasionally detaches from the pigment epithelium. In some instances, the cause of such detachment is injury to the eyeball that allows fluid or blood to collect between the neural retina and the pigment epithelium. Detachment is occasionally caused by contracture of fine collagenous fibrils in the vitreous humor, which pull areas of the retina toward the interior of the globe. Night blindness: Night blindness occurs in any person with severe vitamin A deficiency. The reason for this is that without vitamin A, the amounts of retinal and rhodopsin that can be formed are severely depressed. This condition is called night blindness because the amount of light available at night is too little to permit adequate vision in vitamin A–deficient persons.In addition, the retina has been described as a "window" into the brain and body, given that abnormalities detected through an examination of the retina can discover both neurological and systemic diseases. Diagnosis
A number of different instruments are available for the diagnosis of diseases and disorders affecting the retina. Ophthalmoscopy and fundus photography have long been used to examine the retina. Recently, adaptive optics has been used to image individual rods and cones in the living human retina, and a company based in Scotland has engineered technology that allows physicians to observe the complete retina without any discomfort to patients.The electroretinogram is used to non-invasively measure the retinas electrical activity, which is affected by certain diseases. A relatively new technology, now becoming widely available, is optical coherence tomography (OCT).
Tuberculoid leprosy is a form of leprosy characterized by solitary skin lesions that are asymmetrically distributed with few lesions and well demarcated edges. There is also early and marked nerve damage. It tends to heal spontaneously. : 345  Tuberculoid leprosy is characterized by the formation of epithelioid cell granulomas with a large number of epithelioid cells. In this form of leprosy Mycobacterium leprae are either absent from the lesion or occur in very small numbers. This type of leprosy is the most benign and the least contagious. See also
Leprosy
Skin lesion

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