Ultrastructural analysis of hydraulic and abrasive retinal pigment epithelial cell debridements

Differential changes in Bruch's membrane, choriocapillaris, retinal pigment epithelium, retina, and tapetum after hydraulic or abrasive debridement of the retinal pigment epithelium in the cat area centralis were documented by fluorescein angiography, histology, and transmission electron microscopy at 1-hour, 1-day, 3-day, 1-week, or 4-week time points. Abrasive debridement is associated with abnormal fluorescein angiography and incomplete ingrowth of retinal pigment epithelial cells. Transmission electron microscopy shows that abrasive debridement inflicts more long-lasting ultrastructural damage to Bruch's membrane, the choriocapillaris, tapetum, and retina than does hydraulic debridement. Because the retinal pigment epithelium can resurface abrasively debrided Bruch's membrane that is disorganized, split, reduplicated, or missing, we cannot correlate the ultrastructural appearance of Bruch's membrane with the likelihood of complete resurfacing of the debrided area. Primary choriocapillary or retinal damage in abrasive debridements may contribute to the poor outcome. Regions of retinal degeneration with no underlying retinal pigment epithelial cell monolayer were significantly larger in abrasive debridements at the 4-week than at the 1-week time point. Reduced resurfacing at the later time point suggests that not all cells resurfacing abrasively debrided areas survived over the longer term. This finding may mean that retinal pigment epithelial cells are not able to resurface completely and permanently areas showing geographic atrophy of the choriocapillaris.