Dégénérescence givrée (snail-track, snowflake degeneration) de la périphérie rétinienne: Etude ultrastructurale

Abstract

The ultrastructural study of a case of snail track degeneration shows the presence of lipid inclusions in both the glial and the macrophage cells in every layer of the retina, and the existence of intraretinal fibers different from collagen fibers appearing to be glial filaments similar to those found in astrocytic gliomes and to the Rosenthal fibers observed in senile nervous cells. Other features were thinning of the retina and absence of blood vessels in the retina. There are no abnormalities of the vitreo-retinal juncture. All the lesions are in agreement with those observed by Daicker [Ophthalmologica, Basel 165: 360–365, 1972; Klin. Mbl. Augenheilk. 172: 581–583, 1978] with some differences, however. They are different from those found in lattice degeneration, they show that snail track degeneration is a specific from of peripheral retinal degeneration which is quite different from lattice degeneration and must not be considered similar.

Involvement of the Retinal Pigment Epithelium in the Development of Retinal Lattice Degeneration

“…As described above, the degenerated area of the lesion is often pigmented, and simultaneously, the RPE corresponding to the degenerated area is of uneven thickness and may be partially lost [4,7]. When the RPE cell layer is lost, the degenerated retina comes directly into contact with the Bruch's membrane.…”

“…When the RPE cell layer is lost, the degenerated retina comes directly into contact with the Bruch's membrane. However, no abnormalities, such as obstruction or loss, are seen on the choroidal capillary lamina [4][5][6][7]. These findings indicate that the RPE cells are involved in the pathogenesis of retinal lattice degeneration.…”

“…Moreover, the degenerative lesion is often pigmented, and the thickness of the retinal pigment epithelium (RPE) corresponding to the degenerated area is simultaneously uneven and may be partially lost [ 4 , 7 ]. Although previous studies have reported the migration of macrophages with melanin pigment, no changes in the choroid are usually observed [ 7 ]. These findings suggest that the migration and proliferation of RPE cells may be involved in the pathogenesis of retinal lattice degeneration.…”

“…Numerous reports have indicated that, histopathologically, the degenerated area of retinal lattice degeneration is thinned and devoid of photoreceptors, and is replaced by glial cells in all retinal layers [4,5]. Moreover, the degenerative lesion is often pigmented, and the thickness of the retinal pigment epithelium (RPE) corresponding to the degenerated area is simultaneously uneven and may be partially lost [4,7]. Although previous studies have reported the migration of macrophages with melanin pigment, no changes in the choroid are usually observed [7].…”