Abstract
Purpose: :
To examine surgical outcomes of phacoemulsification (phaco) with intraocular lens following previous trabeculectomy (trab)
Methods: :
Retrospective analysis of glaucoma patients seen between January 1, 2002 and July 1, 2008 with previous trab at least 3 months prior to uncomplicated phaco by a single surgeon. Post-operative refractions were compared to the expected refractive error. The absolute value of the difference in final and expected refraction (absolute refractive difference), along with other findings were compared to the phaco results for a control group of glaucoma patients without previous trab.
Results: :
Patients undergoing phaco after prior trab had significantly greater refractive error than expected. Absolute refractive difference between trab and controls using a one-tailed t-test of 2 samples with equal variance yielded p=0.047. The refractive difference correlated to intraocular pressure (IOP) change (R2=0.25). Mean logMAR visual acuity improved in both trab (p=0.007) and control (p=0.00001), but not statistically different. Mean length of time until final refraction was longer in the trab group (124 days) versus controls (77 days) (p=0.013). Mean IOP increased in trab patients 3.3 mm Hg (8.3 to 11.6). Mean IOP decreased in controls 1.0 mm Hg (17.2 to 16.2) with a concurrent decrease in mean drops (0.84 to 0.36, p=0.001).
Conclusions: :
All patients had significant vision improvement after phaco, but trab patients took longer to stabilize and achieve their final refraction. Trab patients had a greater absolute refractive difference. The refractive difference correlated to IOP change, with 2 mm Hg of IOP rise resulting in a -0.25 diopter shift. Final visual acuity was not affected by the difference in refractive error. After phaco, IOP decreased in controls and fewer drops were required, but IOP increased in patients with prior trab. It was noted that 28% of trab patients had a pre-operative axial length difference of over 0.5 mm between the eyes compared to none of the control; this did not correlate to the refractive differences encountered. Factors affecting refractive difference in phaco after trab including IOP change and axial length will require further investigation.
Keywords: clinical (human) or epidemiologic studies: outcomes/complications • refractive error development • intraocular pressure