Vascular and morphological changes of the optic nerve head following therapeutic intraocular pressure reduction in open angle glaucoma and ocular hypertension

Purpose. To evaluate the vascular and morphologic changes of the optic nerve head (ONH) and peripapillary retina following therapeutic intraocular pressure (TOP) reduction in open angle glaucoma (OAG) and ocular hypertension (OHT). The presence and extent of blood flow changes and topographic changes were correlated with clinical parameters such as cup/disc ratio as well as peripheral vasospasm and central corneal thickness. A correlation between the ONH changes and long term visual field stability was also studied.;For baseline flow, OAG patients had significantly lower blood flow in the ONH compared with OHT patients and normal volunteers (P=0.001). Among patients with OHT, neuroretinal rim blood flow was inversely correlated to increased C/D ratio (P=0.039).;Following similar % IOP reduction (37% in OAG versus 33% in OHT), ONH neuroretinal rim blood flow improved by 67% in OAG (P=0.001) compared to 7.5% in OHT (P=0.41). In OHTs, improvement in neuroretinal rim blood flow was limited to vasospastic subjects (P=0.01). A significant negative correlation (P=0.003) was also found between rim blood flow change and maximum finger blood flow in OAG patients but not in OHTs.;Mean change in ONH topographical parameters following therapeutic TOP reduction did not differ between the two study groups (P≥0.439, ANOVA). Patients with thinner corneas had greater reductions in mean cup depth (P=0.003) and maximum cup depth (P=0.020) and smaller improvements in neuroretinal rim blood flow compared to those with thicker corneas (P=0.04).;Results. SLDF full-field perfusion analysis was found to be highly reproducible in glaucoma patients both within and between sessions with a reliability of ≥0.99 in the neuroretinal rim and ≥0.87 in the peripapillary retina.;Patients with progressive visual field changes were found to be vasospastic (P=0.006) and showed shallowing of maximum cup depth (P=0.005). They also had thinner corneas and smaller increases in neuroretinal rim blood flow (P≥0.31).;Conclusion. The study confirms previous reports as regards decreased baseline ONH blood flow in OAG patients compared to OHT patients and normal subjects. Ocular hypertensives with larger cup/disk ratios were also shown to have lower neuroretinal rim blood flow compared to those with smaller C/D ratios. The study demonstrates that following a similar percentage of therapeutic IOP reduction, blood flow improved in the neuroretinal rim of the ONH in glaucoma patients while it remained stable in ocular hypertensives.;Greater improvements in rim blood flow were observed in vasospastic than in non-vasospastic ocular hypertensives. None of the ONH topographic changes between the two study groups showed a statistically significant difference following therapeutic TOP reduction. However, OAG and OHT patients with thinner corneas showed greater forward displacement of the lamina cribrosa compared to those with thicker corneas.;Assessment of long-term visual stability in a pilot cohort of our subjects showed that at the time of initial IOP reduction, progressive glaucoma patients were more vasospastic and demonstrated a more compliant lamina cribrosa compared to stable glaucoma patients. (Abstract shortened by UMI.).