Functional in vivo assessment of retinal artery microirregularities in glaucoma

Influence of latanoprost on retinal microcirculation in glaucoma

Purpose :

To test whether latanoprost has an influence on ocular haemodynamics, considering the general reputation of prostaglandins which is frequently associated with vasoconstriction. The effect of latanoprost on the retinal blood supply of treatment-naïve glaucoma patients was tested.

Materials and Methodology :

13 patients (7 male, 6 female) who had just recently been diagnosed with primary open-angle glaucoma (POAG) were treated with latanoprost (0.005%). The average age of our study group was 63.8 years (+/- 2.9 years).

The drug’s effect on retinal autoregulation was assessed by flicker test using the Dynamic Vessel Analyzer (DVA). Examinations took place before initializing treatment, after 4 weeks and once again after 4 to 6 months.

Results :

In our group of POAG patients, the IOP under treatment was significantly reduced about 25%. No intraindividual differences in systemic blood pressure and heart rate were observed. In DVA measurements of glaucoma patients, the maximum flicker dilation of the arteries was significantly lower than reported for healthy volunteers. Beyond that, POAG patients did not show significant differences in vessel diameters, peak amplitudes as well as maximum dilations of retinal arteries and veins before and under treatment with latanoprost (0.005%).

Conclusion :

Latanoprost markedly lowered the IOP but it did not exert a significant effect on retinal haemodynamics. There was neither a tendency towards vasoconstriction nor towards vasodilation. Sustaining reperfusion damage after topical latanoprost therapy thus seems to be highly unlikely. Further studies must show if sole IOP lowering or a dual positive effect – IOP lowering and improvement of retinal vessel autoregulation – have a more positive impact on the long term follow-up of glaucoma patients.

Change in retinal blood flow and retinal arterial diameter after intraocular pressure reduction in glaucomatous eyes

PURPOSE

To study retinal blood flow and vessel diameter after intra-ocular pressure (IOP) reduction in high- and low-pressure glaucomas, that is, exfoliation glaucoma (ExG) and normal-tension glaucoma (NTG).

METHODS

The study included 17 eyes with ExG and 20 with NTG. A minimum of 25% IOP reduction was achieved by deep sclerectomy. Blood flow in the temporal peripapillary retina was measured with scanning laser Doppler flowmetry (Heidelberg Retina Flowmeter, HRF), and retinal vessel diameters were evaluated with the retinal vessel analyser (RVA). Examinations were carried out before and 3 months after the operation.

RESULTS

Pre-operative IOP was significantly higher in ExG than in NTG (median 26 mmHg, range 20-33 mmHg versus 15 mmHg, 12-20; p < 0.001). Surgery reduced IOP significantly both in ExG eyes (postoperative IOP 13 mmHg, 5-17; p < 0.001) and NTG eyes (9 mmHg, 3-13; p < 0.001). After the operation, systolic retinal flow was significantly reduced in ExG eyes, whereas in NTG, HRF parameters remained unchanged. Pre-operatively, the central retinal artery equivalent (CRAE) and arteriovenous ratio (AVR) were higher in ExG than in NTG eyes. After IOP reduction, both CRAE and AVR were reduced in ExG eyes, but remained unchanged in NTG.

CONCLUSION

The study showed that before IOP reduction, arterial diameter was larger in ExG eyes than in NTG eyes. IOP reduction resulted in vasoconstriction and reduction of flow in ExG, whereas in NTG, both vessel diameter and retinal flow remained unchanged.

Reduced endothelial progenitor cells and brachial artery flow-mediated dilation as evidence of endothelial dysfunction in ocular hypertension and primary open-angle glaucoma

PURPOSE

This study aimed to assess vascular endothelial function in patients with ocular hypertension (OHT) or primary open-angle glaucoma (POAG) by measuring: (a) endothelium-dependent flow-mediated vasodilation (FMD) of the brachial artery, and (b) circulating endothelial progenitor cells, which are believed to support the integrity of the vascular endothelium.

METHODS

We enrolled 25 patients with OHT, 23 with POAG and 26 control subjects, all of whom were aged < 65 years and had no medical history of cardiovascular disease or cardiovascular risk factors. All subjects underwent a complete ophthalmological examination, biochemistry study, assessment of cardiovascular parameters, brachial artery ultrasound assessment of endothelium-dependent FMD, generic circulating progenitor cell (CPC) and circulating endothelial progenitor cell (EPC) count with the use of flow cytometry.

RESULTS

Flow-mediated vasodilation values differed significantly in OHT (4.5 +/- 1.1%; p = 0.021) and POAG (4.0 +/- 0.9%; p = 0.003) patients compared with controls (7.7 +/- 0.8%). The CD34(+) KDR(+) EPC count was markedly lower in OHT (28.0 +/- 5.0; p < 0.001) and POAG (24.3 +/- 3.4; p < 0.001) patients compared with controls (73.1 +/- 8.1). Neither FMD not EPCs differed significantly between OHT and POAG patients. No significant differences in CPC count or cardiovascular parameters were found among OHT or POAG patients and controls. The levels of CD34(+) KDR(+) EPCs were directly correlated (p = 0.043) with FMD, and inversely correlated (p = 0.032) with baseline intraocular pressure in OHT and POAG patients.

CONCLUSIONS

Both OHT and POAG patients without cardiovascular risk factors have previously unreported severely reduced circulating EPCs and reduced FMD, both of which are indicators of endothelial dysfunction and increased risk of cardiovascular events.

Changes in optic nerve head blood flow induced by the combined therapy of latanoprost and beta blockers

PURPOSE

To assess the effects of combined therapy with latanoprost and beta blockers on optic nerve head (ONH) blood flow in normal-tension glaucoma (NTG) patients.

METHODS

Intraocular pressure (IOP), ONH blood flow (laser speckle flowgraphy) and blood pressure were measured in 15 eyes of 15 NTG patients (41-76 years old) before treatment or after a 1-month washout period. Similar measurements were performed at 2 months after the commencement of treatment with latanoprost and at 3 months after the start of combined therapy of latanoprost with 0.5% timolol or 2% carteolol in a crossover study using the envelope method. Measurement was carried out 2-3 hr after the morning application of eyedrops.

RESULTS

Latanoprost decreased IOP with no significant change in ONH blood flow. Concomitant use of timolol or carteolol further decreased IOP with no significant difference between these two drugs. Only the combined therapy of latanoprost with carteolol significantly (p < 0.01) increased ONH blood flow by approximately 10%, compared to initial levels. There was no significant change in mean blood pressure, ocular perfusion pressure or pulse rate as a result of these therapies.

CONCLUSION

Topical latanoprost-carteolol combined therapy increased ONH blood flow in NTG patients, unlike latanoprost-timolol therapy. Because ocular perfusion pressure was unchanged, direct vasodilative effects were suspected as the mechanism.