Detecting Conversion from Ocular Hypertension to Glaucoma; By Trend or by Event analysis?

Abstract

Purpose: : To explore and compare conversion from ocular hypertension to glaucoma on Standard Automated Perimetry (SAP) with other progression event and trend analyses.

Methods: : Four hundred sixteen subjects with ocular hypertension (intraocular pressure ≥22 and ≤32 mmHg and normal visual fields) were measured every 6 months with a Humphey Field Analyzer (24-2 program; Carl Zeiss Meditec, Dublin, USA). Conversion to glaucoma was defined as a reproducible glaucomatous visual field defect in SAP. This outcome was compared with progression on trend and event analyses of SAP (Guided Progression Analysis (GPA), HFA-II-i, Software Version 4.2, CZM). Progression was defined as 2 consecutive reports of possible or likely progression in event analysis, and as a rate of progression of > -1.0 dB/year in trend analysis.

Results: : Twenty-five of the 416 eyes converted to glaucoma. Of these eyes, 19 were fit for GPA. On event analysis, 13 eyes showed progression. On trend analysis, only 2 out of 19 eyes showed progression. Event analysis reported significantly more conversions than trend analysis (p-value = 0.028; Chi²-test).

Conclusions: : To measure conversion of ocular hypertension to glaucoma by means of visual field testing, an event analysis apparently is more sensitive than a trend analysis.

Keywords: visual fields • perimetry