Abstract
Purpose: :
Post-surgical intraocular pressure (IOP) less than 5 mm Hg is widely recognized as a criterion of surgical failure because associated disturbances such as hypotony maculopathy frequently result in poor vision. The purpose of this study is to challenge that criterion and present data demonstrating hypotony can be compatible with good visual acuity devoid of macular edema.
Methods: :
Patients with good preoperative vision and IOP ≤9 mm Hg at least 6 months post filtering surgery and with no surgical interventions for low IOP were enrolled. Spectral domain macular OCT, best corrected visual acuity, and a questionnaire based on hypotony symptoms were evaluated. Descriptive statistics were used to compare and characterize the sample distribution of two patient groups: patients with IOP 0-4mm Hg ("hypotony") and a comparison group with IOP 5-9 mm Hg ("low IOP").
Results: :
The hypotony group (n=15) and the low IOP group (n=30) did not diverge significantly on any of the studied parameters including postoperative visual acuity, change from preoperative acuity, hypotony symptoms, hyperopic shift and macular OCT thickness. However, more patients in the hypotony group exhibited choroidal folds than the low IOP group (40% vs 17%).
Conclusions: :
This study demonstrates that postoperative IOP less than 5 mm Hg should not always be considered a surgical failure. Nonetheless, our study has limitations including a small sample size. Because patients were not enrolled prospectively, we cannot reliably estimate the prevalence of hypotony patients who postoperatively retain good visual function.
Keywords: intraocular pressure • visual acuity • macula/fovea