OBJECTIVE

This study examined the impact of trabeculectomy on the central visual field in patients in which field loss threatens fixation.

METHODS

Fifty eyes in 45 patients demonstrating a visual field loss threat to fixation underwent trabeculectomy. All patients underwent visual field assessment before and within two months of surgery, using both the 24-2 quantitative program on the Humphrey Field Analyser, and the macular program which measures the threshold sensitivity three times per 16 points distributed in the central 5 degrees centrally at 2 degrees intervals. For inclusion in the study, each eye had to show involvement of at least two contiguous points in the central macular program, with a decrease in sensitivity to 15 dB or less, in a quadrant corresponding to a well-defined visual field defect shown on program 24-2.

RESULTS

The average post-operative follow-up was 7.1 months (+/- 5.52). Overall intraocular pressure reduction was 40%. Visual acuity decreased on an average of half line. None of the eyes showed loss of fixation. The average number of points with decreased sensitivity in the central 5 degrees (15 dB sensitivity or less) was 6.06 points (+/- 3.36) pre-operatively and 5.78 points (+/- 3.85) post-operatively (p = NS). Mean Defect (MD) was noted to decrease by 1 dB (p = 0.0295) whereas Corrected Pattern Standard Deviation (CPSD) and Foveal Sensitivity (FS) was essentially stable.

CONCLUSIONS

Based on the study, it appears that trabeculectomy can be safely offered to patients for surgical reduction of intraocular pressure even in those cases where central fixation is threatened by loss of vision within the five degrees of fixation.