Controversies in the surgical treatment of combined hamartomas of the retina and retinal pigment epithelium

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Combined hamartomas of the retina and retinal pigment epithelium are rare benign tumors that may cause significant visual loss. Combined hamartomas are usually solitary, unilateral lesions located at the optic disc or posterior pole. They typically appear slightly elevated and have varying amounts of pigmentation, vascular tortuosity and epiretinal membrane formation. They are usually diagnosed in children or young adults with painless visual loss. Visual function varies with the location of the lesion. Direct involvement of the optic nerve, papillomacular bundle, or fovea may reduce visual acuity. If these structures are not directly involved, visual loss may result from macular distortion by retinal striae and epiretinal membrane. According to the Macula Society’s1 report of 60 patients with combined hamartomas, the tumor was located on the optic disc and adjacent retina in 18% of patients, adjacent to the disc in 28% of patients, extending from the disc to the fovea in 10% of patients, in the macula in 38% and in the mid-periphery in 5% of patients. Macular location of the tumor is a predictor of poor visual acuity, found in 69% of macular tumors and only 25% of extramacular tumors. Histopathologically, combined hamartomas show evidence of hamartomatous malformation involving hyperplasia of RPE, glial cells, and blood vessels. Epiretinal membranes are an important cause of progressive visual loss, especially in eyes with macular tumors. Indication for epiretinal membrane removal in these patients is not well stablished, and cases reported in literature show different visual results. McDonald et al2 indicated that vitrectomy was not beneficial in their 2 cases, whereas Mason3, Kleiner3 and Stallman4 found benefit in their cases. The surface glial membrane causing the retinal folding is an integral part of the tumor in some cases and accounts for the fact that surgical stripping of the membrane is difficult and has little chance of restoring central vision in such cases5. Surgical intervention should be selected carefully; full-thickness macular holes have occurred when the membrane is intrinsically woven into the lesion6. It has been speculated that OCT could provide useful information regarding potential visual benefit as the more intact retina on OCT might have better visual outcome than the completely disorganized, thickened retina7. Vitreous traction if present may also be detected, and thus help in selecting cases that may have a potential for visual improvement with vitrectomy and membrane peel to relieve traction.

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