Lacquer crack lesions in experimental chick myopia.

Abstract

Lacquer crack lesion (LCL) is a complication of human pathologic myopia, accompanied by loss of retinal pigment epithelium (RPE) and break of Bruch's membrane. The present paper describes comparable lesions occurring in prolonged experimental myopia in the chick. Form-deprivation myopia was induced by unilateral eyelid suturing on the 1st day after hatching. Bruch's membrane in NaOH hydrolyzed preparations and vascular corrosion casts of the choroidal vasculature were examined with scanning electron microscopy. Histological changes in the retina and choroid were also examined with light and transmission electron microscopy. Pale and linear lesions were found in the myopic chick eyes at the age of 8 weeks. In the lesion area, Bruch's membrane was totally broken up and the network of choriocapillaries was totally ruptured with highly atrophied marginal capillaries. The retina was continuous, but was depressed to form a groove in the lesion with the apparently intact inner retina and degenerated photoreceptor cells. Attenuated fibroblasts encompassed the outer circumference of the lesion. RPE cells were scattered in the tissue space inside the fibroblastic investment and also in the choroidal stroma without their polarity. The formation of LCL was suggested to be a result of passive stretch exerted upon Bruch's membrane and the capillary network due to abnormal enlargement of the myopic eyes. These results may promote further understanding of the mechanism regarding the development of human lacquer cracks.