(rĕt′ĭ-năl) 1. Pertaining to the retina. 2. The light-absorbing portion of a photopigment, a derivative of vitamin A.
A break in the continuity of the retina, usually caused by trauma to the eye. Detachment of the retina may follow the appearance of the break.
A condition in which simultaneous stimulation of points in the retina of each eye results in formation of a single visual sensation. These points, called corresponding points, lie in the foveae of the two retinas, or in the nasal half of one retina and the temporal half of the other. Abnormal correspondence results in double vision (diplopia) and usually is caused by imbalance of the ocular muscles. SEE: strabismus.
A treatment for a retinal tear in which the retina and choroid surrounding the tear are frozen. This scars the retina around the tear, sealing the defect. Cryopexy is typically used to treat lesions at the retinal periphery, which may be difficult to treat with a laser.
Separation of the inner sensory layer of the retina from the outer pigment epithelium.
INCIDENCE: About 1 person in 10,000 experiences retinal detachment annually. The disease is more likely to occur in people who have a family or previous personal history of detachment.
CAUSES: It is usually caused by a hole or break in the inner sensory layer that permits fluid from the vitreous to leak under the retina and lift off its innermost layer. This may occur after trauma to the eye or head, after cataract surgery, in people who are extremely myopic, and in any disease that causes retinopathy (such as diabetes or sickle cell disease).
SYMPTOMS AND SIGNS: Sudden onset of blurred vision, flashes of light, vitreous floaters, and painless loss of visual acuity are the most common symptoms.
DIAGNOSIS: It may be diagnosed with slit lamp examination of the retina, or with bedside ocular ultrasonography. The location of holes must be determined so that they can be repaired by laser therapy (photocoagulation).
TREATMENT: Scleral buckling techniques are used to treat retinal detachment in a large number of patients. Vitrectomy with laser and pneumatic retinopexy are occasionally employed as an alternative treatment.
The enzyme in rods and cones that converts trans-retinal to cis-retinal, which then combines with the opsin present to form a photopigment responsive to light.
(rĕt-ĭ-nī′tĭs) [L. retina, retina, + Gr. itis, inflammation] Inflammation of the retina. Symptoms include diminished vision, contractions of fields or scotomata, alteration in the apparent size of objects, and ...