Longitudinal and Cross-Sectional Analyses of Visual Field Progression in the Ocular Hypertension Treatment Study (OHTS)

Abstract

Purpose:: To compare longitudinal and cross-sectional analyses of visual field progression in participants of the OHTS.

Methods:: Visual field data from 3088 eyes of 1570 subjects (772 treated, 798 untreated, median follow-up 7 y, 15 tests) were analysed for change. Longitudinal analyses (change probability and linear regression) were compared to cross-sectional analyses (eg, OHTS criteria of Glaucoma Hemifield Test and/or Corrected Pattern Standard Deviation p<0.05 in 3 consecutive tests). Longitudinal analyses were performed with total and pattern deviation, using a wide range of criteria (1 to 20 locations). Diffuse progression was investigated using regression of Mean Deviation and General Height (GH) over time.

Results:: Progression rates varied between 1% and 11%, depending on the criteria. The agreement between longitudinal and cross-sectional analyses in detecting progression ranged from 50% to 61%; agreement on absence of progression ranged from 97% to 99.7%. In visual fields classified as having changed by both longitudinal and cross-sectional analyses there were no overall differences in time-to-progression (p>0.1), but either approach could show progression earlier in individual eyes (SD, 1.2 y). Differences between treated and untreated subjects were evident across a wide range of criteria. Analyses of total deviation were more sensitive than those of pattern deviation (incidence of progression between 3 and 5 times higher), and showed larger treatment effects (p<0.05), with both change probability and regression analyses. There was no evidence for accelerated diffuse progression in the treated compared to the untreated group (median GH slopes, -0.04 and -0.05 dB/y, p=0.14). Nearly all visual fields with evidence of progression showed diffuse as well as focal change.

Conclusions:: Longitudinal and cross-sectional analyses of progression had similar power in detecting differences between treated and untreated subjects. Because progressive visual field loss in patients with early glaucoma entails diffuse as well as focal components, analyses based solely on pattern deviation may underestimate visual field progression in these patients.

Clinical Trial:: OHTS

Keywords: visual fields • perimetry • clinical research methodology