Contributor: Gordon K. Klintworth
Lattice degeneration of the retina is a fairly common degenerative disease of the peripheral retina characterized by the presence of lattice lines created by fibrosed blood vessels. Usually ~2 oval lesions (~0,55 x 2.0 mm in diameter) are present in each eye and the inner limiting membrane of the retina is disrupted. Fibrosed or occluded retinal blood vessels appear clinically as white lines within an area of retinal thinning and may be associated with punched-out holes or focal hemorrhages. The condition may be familial and myopia seems to be a risk factor. The condition is least common in the second decade of life, but its fequency is evenly distributed during subsequent decades. In ~50% of cases the condition is bilateral and strikingly symmetrical in its location and appearance. Males and females are equally affected. Ischemia may initiates the process which is characterized in its fully developed state by focal vitreous liquefaction, vitreous detachment, vitreous condensation at the margins of the lesion, thinning and scarring of retina as well as retinal pigment epithelial depigmentation and pigment clumping. The primary cause may be ischemia from a retinal circulatory disturbance. The blood vessels around regions of retinal lattice degeneration are commonly abnormal (leak fluorescein, have delayed filling, arteriovenous shunts, capillary dilation, microaneurysms [aneurysm - micro]). The lesions are located parallel to the ora serrata in the pre-equatorial region of the retina. The lower temporal quadrant is most commonly involved, and most lesions are located close to the vertical meridian, both superiorly and inferiorly. The lesions are non-progressive or very slowly progressive, and rarely predispose to retinal detachment. A discrete zone of thin retina is associated with vitreous liquefaction, vitreous separation and vitreous condensation around the liquefied region. Abnormalities of the retinal pigment epithelium accompany most lattice lesions. In the affected retina the capillaries are reduced in number and associated with fibrosed larger blood vessels that often have occluded lumina. The abnormalities in the micovasculature are readily observed in trypsin-digested flat retinal preparations.