Influence of type 2 diabetes mellitus on functional progression of primary open-angle glaucoma

PURPOSE: To assess the effect of diabetes mellitus (DM) type 2 on the functional progression of primary open-angle glaucoma (POAG) by comparing the rate of progression (RoP) of POAG in eyes with and without diabetes. METHODS: In a retrospective observasional study from our practice were included 32 followed-up POAG patients with accompanying disease DM type 2 (60 eyes) (group I, POAG + DM) and 32 patients with POAG without DM (58 eyes) (group II, POAG-DM). The groups were matched by age and gender but not by stage of POAG iat the start of investigation. The mean period of disease tracking was 6.0 ± 3.4 years (from 2 to14 years) for POAG + DM group and 5.4 ± 2.3 years (from 2 to 10 years) for POAG -DM group. Visual field (VF) changes were determined by standard automatic perimetry, Humphrey analyzer, program 30 - 2. For each eye the slope of MD (Mean deviation) changes over time was calculated and the RoP was established. RESULTS: A significant difference was observed for initial MD values in eyes of both groups: -5.52dB in groupI vs. -10.66 dB in group II. The number and percentage of eyes with initially severe VF losses was three times higher in group II: 21 eyes (36.2%) vs. 7 eyes (11.7%). A real progression in one or both eyes was established in 21 patients of POAG + DM group and in 25 patients of POAG-DM group. During the follow-up period the progressing eyes were 34 eyes (56.7%) in POAG + DM group and in 38 eyes (65.5%) in POAG-DM group. The difference between both groups was not significant (P > 0.05) about progressing eyes. The mean value of RoP in the progressing eyes was - 0.98 ± 1.12/year in POAG + DM group and - 0.78 ± 0.66/year in POAG-DM group. Although RoP was larger in progressing POAG + DM, no significant difference was found in both groups (Z - 0.017, Sig 0.986, Mann-Whitney Test). CONCLUSIONS: The real influence of DM on functional progression of POAG was not established in this comparative study. The rate of progression in POAG eyes with DM type 2 was slightly higher but without statistical significance. It was due to the significantly greater percentage of eyes with severe visual field changes in POAG patients without DM. The severity of POAG influences the assessment of the functional progression in eyes with and without DM.