Intra-Retinal Cotton Wool Spots (CWS) Associated With Epiretinal Membrane(ERM) Contraction: Movements and Time Course of Disappearance Following Membrane Peeling

Abstract

Abstract: : Purpose: Epiretinal membrane contraction and resultant nerve fibre layer distortion may lead to blockage of axoplasmic flow and thus a cotton wool spot. This study observes the pre-operative location and documents postoperative movement and time course of disappearance of cotton wool spots after epiretinal membrane peeling. It also measures retinal distortion in the post-operative period. Methods: Four patients with epiretinal membranes associated with intraretinal cotton wool spots were evaluated before and after surgery. Scheduling was done on the basis of following inclusion criteria. (1)Patient's awareness of visual distortion and binocular interference. (2)Snellen's visual acuity of 6/18 or worse. (3) Absence of co-existing ocular morbidity affecting vision. None of these patients had evidence of systemic or ocular vascular disease. All patients underwent vitrectomy and membrane peeling. Postoperatively, the movement and time course of disappearance of CWS were documented by fundus photographs taken with the same camera and projected at the same magnification. Changes in retinal distortion were estimated by measuring the distance between reference retinal vascular branches in pre and post-operative photographs. Results: Intra-retinal CWS showed a centrifugal movement (away from the centre of fovea) in all four cases (100%). CWS disappeared completely in 3(75%) patients by the seventh postoperative day. In one patient all CWS disappeared by day 14 post-operatively. Retinal distortion was demonstrated and measured in all four patients. All patients reported an improvement in visual symptoms. Two(50%) patients showed an improvement in visual acuity of one Snellen's line. One patient(25%) improved by two Snellen line and in one patient(25%) the vision remained unchanged. Conclusion: In all cases the CWS disappeared within fourteen days of ERM removal. The time course of disappearance of these intraretinal white lesions are consistant with cotton wool spots caused by mechanical disruption of axonal flow. The limited improvement of visual acuity in all four patients raises the question as to whether some of the visual deficit in severe ERM's might be due to disruption of axonal flow affecting visual recovery due to axonal damage.

Keywords: 554 retina • 628 vitreoretinal surgery