Evaluation of the progression of visual field damage in patients suffering from early manifest glaucoma

Abstract

Background: This retrospective study aimed to determine how often a perimetric examination should be carried out in order to identify visual field (VF) changes in patients with relatively early manifestation glaucoma.

Materials and methods: Patients included had a relatively recent manifestation of primary open-angle glaucoma. Patients with a minimum follow-up of 5 years and a minimum of seven VF tests were included. Statistical analysis was performed to verify the trend of variations in mean defect (MD) over time (PeriData). The results were subjected to a t-test for a comparative analysis of progression of VF changes over time. The annual rate of progression provided by PeriData considering all the VFs analyzed was compared with that obtained on half of the VF examinations during the same follow-up period. An analysis of the MD trend over time was also carried out in relationship to the number of VF tests done and by dividing the sample into a high-frequency group (more than eight VFs) and a low-frequency group (fewer than eight VFs) in the follow-up period.

Results: A total of 96 eyes of 96 patients were included, and overall 846 VFs were examined. The paired t-test performed comparing the MD index of all the VFs against half of them did not show statistical significance (P=0.537). The high-frequency group comprised 39 eyes (average VF 11.05±1.91, average time interval 0.76 years) while the low-frequency group comprised 57 eyes (average VF 6.95±0.6, average time interval 1.21 years). The analysis of the MD trend in the high-frequency patients showed significance (P=0.017); the low-frequency group did not show statistical significance (P=0.08).

Conclusion: The number of VFs in a determined time interval was not significant. However, a greater frequency of tests provides a predictive evaluation of the rate of progression of early manifestation open-angle glaucoma.

Keywords: ocular hypertension; open-angle glaucoma; progression; visual field.

Figure 1

Progression rate of mean defect in all visual field over 1 year (year), in the same follow-up period considering one VF out of three (half) and in the first 3 and 6 months of follow-up (3 month; 6 month).

Figure 2

Scatterplot represents standardized residual plot (ZPRED on X axis and ZRESID on Y axis) of (A) low- frequency group and (B) high-frequency group. The dependent variable is mean defect for both groups. Abbreviations: ZPRED, regression standardized predicted; ZRESID, regression standardized residual.