Oximetry in glaucoma: correlation of metabolic change with structural and functional damage.

PURPOSE: To determine whether retinal vessel oxygen saturation in patients with glaucoma is associated with structural optic disc and retinal nerve fibre layer (RNFL) changes and visual field (VF) defects. METHODS: Fifty-nine patients with confirmed glaucoma were recruited at University Hospitals Leuven. Retinal oxygen saturation in patients with glaucoma was measured with a noninvasive spectrophotometric retinal oximeter (Oxymap ehf, Reykjavik, Iceland). VF and Heidelberg retinal tomographies (HRTs) were performed on the same day. Statistical analysis was performed using Student's t-test and Pearson's or Spearman correlation coefficient. RESULTS: The mean oxygen saturation in venules was higher in patients with severe VF defects compared to those patients with mild VF defects (69 ± 3% versus 65 ± 6% respectively; p = 0.0003; n = 59). Accordingly, the arteriovenous (AV) difference in oxygen saturation was lower in patients with worse VF compared to those with better VF (29 ± 3% versus 33 ± 6% respectively; p = 0.002). The oxygen saturation in venules correlated with the VF mean defects (r = -0.42; p = 0.001; n = 59) as well as with the structural HRT parameters rim area and RNFL thickness (r = -0.39; p = 0.008 and r = -0.26; p = 0.05 respectively; n = 53). The AV difference decreased significantly as the VF defect worsened (r = 0.38; p = 0.003), as the rim area diminished (r = 0.29; p = 0.03) and as the RNFL thickness decreased (r = 0.27; p = 0.05). No correlation was found between the oxygen saturation in retinal arterioles and either of these parameters. CONCLUSION: Severe glaucomatous damage is associated with increased oxygen saturation in retinal venules and decreased AV difference in oxygen saturation. These data suggest that in eyes with severe glaucomatous damage, reduced retinal oxygen consumption is consistent with tissue loss.

Long term IOP lowering efficacy of bimatoprost/timolol fixed combination: a 12 month prospective study.

PURPOSE: To evaluate the long-term IOP-lowering effect of an initially successful switch from prostaglandine-analog (PGA) monotherapy to bimatoprosttimolol fixed combination (BTFC) METHODS: Prospective, monocentric, open-labeled clinical trial. 30 patients with insufficient intraocular pressure (lOP) control under PGA monotherapy were screened. Following a one month run-in period of BTFC, patients who presented an effective IOP-lowering response were prospectively studied for an additional 11-month period. IOP, tolerability and safety (adverse reactions, slit lamp biomicroscopy) were further assessed at month 6 and month 12 after initiating BTFC. RESULTS: BTFC therapy significantly decreased IOP when compared to PGA monotherapy (PGA monotherapy: 17.3+/-3.8 mmHg; BTFC 1 month 13.2+/-3.3mmHg; p<0.05). This decrease from PGA-monotherapy IOP was sustained throughout the time-frame (6-month: 13.5+/-3.6mmHg; 12-month: 13.9+/-2.4mmHg; p<0.05 in pairwise comparison). There was no statistical difference in IOP between BTFC study visits (p>0.05). Of the 27 patients who had a satisfactory lOP-lowering response to BTFC after one month, 18 (66.7%) still had sufficient IOP control at the 12 month study visit. Therapy was discontinued at 1 month in 3 patients (2 due to intolerance to medication and 1 failing to achieve IOP control). No intolerability was reported beyond the 1 month of BTFC therapy. CONCLUSION: In the majority of patients, the initial lOP lowering effect of replacing PGA monotherapy by BTFC seems to predict a long term response to the new treatment strategy.