Purpose: To evaluate visual field (VF) changes in glaucomatous and nonglaucomatous eyes after transient elevation of intraocular pressure (IOP).
Design: Prospective experimental study.
Participants: One hundred subjects (38 with glaucoma, 62 glaucoma suspects and controls).
Methods: Intraocular pressure elevation was induced in the right eye of all subjects with a modified LASIK suction ring. Intraocular pressure was elevated to an average of 64 mmHg for <30 seconds. Humphrey Matrix perimetry 24-2 threshold tests were performed before and after the procedure. A cohort of patients who demonstrated significant deterioration in postprocedural perimetry was recalled for further testing.
Main outcome measures: Mean deviation (MD) and pattern standard deviation (PSD) from Humphrey Matrix perimetry.
Results: A significant decline in MD of the right eye could be observed on immediate postprocedural perimetry amongst glaucoma and control patients, whereas no significant changes in PSD were seen in either group. Forty-five of 47 patients, whose immediate postprocedural perimetry showed a loss of MD > 2 decibels, attended for repeat perimetric testing with a median follow-up of 6 days. Both eyes among 28 control patients and the left eye among 17 glaucoma patients showed statistically significant improvement in MD. Similar improvement was seen in the right eye of glaucoma patients, but this failed to reach statistical significance. Six patients from the glaucoma group demonstrated deterioration in MD upon recall, compared with 3 in the control group (P = 0.046). These 6 patients were significantly younger than the rest of the group, but no other defining characteristics were identified.
Conclusions: Transient elevation of IOP in adult eyes with and without glaucomatous optic neuropathy did not lead to functional optic nerve change, as measured by Matrix perimetry, in the short term for the majority of patients. It is possible that a small cohort of patients with preexisting glaucomatous optic neuropathy may be more susceptible to transient increase in IOP, although the result is inconclusive. Prominent learning effects may have masked subtle worsening of visual function in our subjects; corresponding structural analyses of the optic nerve and longer-term follow-up may provide further information.