Abstract
Abstract: :
Purpose:Assessment of the changes in bleb appearance in the four year period following trabeculectomy and identification of risk factors for loss of intraocular pressure (IOP) control. Methods:The Moorfields Bleb Grading System ratified by the Moorfields Reading Centre was used to objectively assess the change in photographic appearance of 200 blebs over a four–year period following trabeculectomy. The grading system divides the superior conjunctiva and bleb into a central (demarcated) zone, a peripheral bleb zone and a non–bleb zone. Patients were participating in a large RCT of intra–operative 5FU (MRC/Moorfields More Flow Study) and photographs had been taken at weeks 1, 2, 4, 6, 12, and 26 post–operatively, and at each annual visit. Comparisons of bleb appearance were made of patients who lost IOP control and those who did not. Results:The increased post operative vascularity of the three morphologically distinct trabeculectomy bleb zones reduces over time, being maximal at week 1. The central demarcated bleb normalises by 26 weeks post–op. Both peripheral bleb and surrounding bleb conjunctiva show a stepwise reduction in vascularity. For both these bleb zones mean vascularity scores, up to and including 52 weeks, remain significantly raised compared to three–year (156 weeks) values. There is no significant difference between the scores for two, three and four years. In addition the mean vascularity scores of these two bleb zones for the first 6, 12, 26 and 52 weeks is increased in patients who lost IOP control compared to patients with controlled IOP. Conclusions:The return to normalised conjunctival vascularity in the peripheral bleb and surrounding non–bleb conjunctiva, measured objectively by a masked reading centre, takes over one year. Trial survival data indicates that the first year carries the greatest risk of IOP failure and in those patients mean vascularity scores are higher than patients who do not fail. Treatment aimed at reducing postoperative bleb inflammation, and subsequent postoperative bleb failure and loss of IOP control may be required for one year.
Keywords: wound healing • inflammation • conjunctiva