The impact of ocular blood flow in glaucoma.

What Is the Present Pathogenetic Concept of Glaucomatous Optic Neuropathy

The vasculature of the eye and the heart share several common characteristics. The easily accessible vessels of the eye are therefore—to some extent—a window to the heart. There is interplay between cardiovascular functions and risk factors and the occurrence and progression of many eye diseases. In particular, arteriovenous nipping, narrowing of retinal arteries, and the dilatation of retinal veins are important signs of increased cardiovascular risk. The pressure in the dilated veins is often markedly increased due to a dysregulation of venous outflow from the eye. Besides such morphological criteria, functional alterations might be even more relevant and may play an important role in future diagnostics. Via neurovascular coupling, flickering light dilates capillaries and small arterioles, thus inducing endothelium-dependent, flow-mediated dilation of larger retinal vessels. Risk factors for arteriosclerosis, such as dyslipidaemia, diabetes, or systemic hypertension, are also risk factors for eye diseases such as retinal arterial or retinal vein occlusions, cataracts, age-related macular degeneration, and increases in intraocular pressure (IOP). Functional alterations of blood flow are particularly relevant to the eye. The primary vascular dysregulation syndrome (PVD), which often includes systemic hypotension, is associated with disturbed autoregulation of ocular blood flow (OBF). Fluctuation of IOP on a high level or blood pressure on a low level leads to instable OBF and oxygen supply and therefore to oxidative stress, which is particularly involved in the pathogenesis of glaucomatous neuropathy. Vascular dysregulation also leads to a barrier dysfunction and thereby to small retinal haemorrhages.

The eye and the heart

Background The risk of open-angle glaucoma (OAG) may be related to low blood pressure(BP) relative to intraocular pressure (IOP), ie, to low perfusion pressure(PP). Alternatively, systemic hypertension may increase OAG risk. Objective To clarify these possible relationships by evaluating hypertension and PP (where PP = BP − IOP) as risk factors for incident OAG in a black population. Design Population-based cohort study (85% participation); simple random sample of residents of Barbados, West Indies, aged 40 years and older. Participants Two thousand nine hundred eighty-nine black participants at risk; 67 developed OAG after 4 years (2.2% incidence). Main Outcome Measure Adjusted relative risk (RR) of OAG from logistic regression analyses. Results The 4-year risk increased markedly with baseline IOP. With an IOP less than or equal to 17 mm Hg, incidence was 0.7%, increasing to 18.3% with IOP greater than 25 mm Hg, for a 25-fold increase in RR. However, OAG developed throughout the IOP range and two thirds of incident cases had baseline IOP less than 25 mm Hg. Baseline hypertension was associated with a halving of the RR of OAG (RR, 0.49; 95% confidence interval [CI], 0.29-0.85); the RR also tended to decrease as systolic BP increased ( P = .07). Consistent with these findings, a lower baseline PP increased RR (systolic PP Conclusions As baseline IOP increased, the risk of OAG substantially increased. In contrast, persons with systemic hypertension at baseline had half the RR, suggesting that hypertension does not increase (and may decrease) the 4-year risk of OAG. Lower PP at baseline increased RR approximately 3-fold, a result consistent with the vascular hypothesis of OAG pathogenesis.

https://jamanetwork.com/journals/jamaophthalmology/articlepdf/271345/eeb10014.pdf

Incident open-angle glaucoma and blood pressure.

Ocular perfusion pressure and ocular blood flow in glaucoma.

Relationship between ocular perfusion pressure and retrobulbar blood flow in patients with glaucoma with progressive damage

Purpose. To test the interocular differences in optic disc topography in normal subjects by means of confocal scanning laser ophthalmoscopy. Methods. Topographic measurements of the optic disc were evaluated by means of confocal scanning laser ophthalmoscopy (Heidelberg Retina Tomograph) in 314 eyes of 157 healthy volunteers. The examination was started randomly either with the right eye or the left eye. Differences between right and left eyes in disc area, cup area, cup volume, cup/disc area ratio, rim area, rim volume, maximum cup depth, cup shape measure, retinal nerve fiber layer thickness, and retinal nerve fiber cross section area for 360° and for the temporal and nasal regions of the optic nerve head were evaluated by means of Student t-test. The same parameters were assessed in a subgroup of 80 elderly (age > 50 years) healthy subjects. Holm's sequentially rejective method was used for significance correction of multiple comparisons. Results. Significant interocular differences in the average r...

Interocular differences in optic disc topographic parameters in normal subjects

The Influence of Sex Difference in Measurements with the Langham Ocular Blood Flow System

PURPOSE To evaluate the effect of 0.5% timolol maleate on the capillary circulation of the anterior optic nerve head in patients with primary open-angle glaucoma and to compare the results with those obtained in a healthy control group. PATIENTS AND METHODS Twelve patients with nonprogressive glaucoma and 12 age- and sex-matched healthy volunteers were included in this prospective study. Optic nerve head perfusion was examined by the Heidelberg Retina Flowmeter (HRF) in both groups. A 3-week washout period preceded the baseline measurement in the glaucoma group, and ONH blood flow was assessed again after 3 weeks of bilateral topical timolol treatment and 2 hours after timolol application. RESULTS Intraocular pressure decreased significantly with timolol (P < 0.001). The HRF flow values for patients with glaucoma were comparable to those for a control group at baseline (P = 0.25), 3 weeks after timolol therapy (P = 0.09), and 2 hours after timolol instillation (P = 0.15). The glaucoma group showed no statistically significant change in the HRF parameter flow as compared with baseline, either after 3 weeks of timolol treatment or 2 hours after timolol instillation (P = 0.40). The heart rate and arterial systolic and diastolic blood pressure values showed no alteration after timolol therapy. CONCLUSIONS Patients with nonprogressive glaucoma seem not to have an altered optic nerve blood flow as assessed by the HRF, and timolol treatment does not seem to alter the latter blood flow parameter in such patients.

Margarita Gekkieva

Papers

Relationship between ocular perfusion pressure and retrobulbar blood flow in patients with glaucoma with progressive damage

Interocular differences in optic disc topographic parameters in normal subjects

The Influence of Sex Difference in Measurements with the Langham Ocular Blood Flow System

Effect of timolol on anterior optic nerve blood flow in patients with primary open-angle glaucoma as assessed by the Heidelberg retina flowmeter.

Relationship between ocular perfusion pressure and retrobulbar blood flow in patients with glaucoma with progressive damage: Author’s reply