Background: Ocular perfusion pressure (OPP) is defined as blood pressure (BP) minus intraocular pressure (IOP). Low OPP may result in decreased ocular blood flow (OBF) and oxygen to the optic nerve head (ONH) and retina.Aim: To review the role of systemic hypotension and similar conditions in OPP and its influence on retinal nerve fibre layer (RNFL) thickness and the ganglion cell complex (GCC).Method: A literature search was conducted using the following search terms: ‘systemic hypotension’; ‘glaucoma’; ‘retinal nerve fibre layer’; ‘optic nerve’; ‘ocular blood flow’ and ‘ocular perfusion pressure’.Results: The Los Angeles Eye Study and Barbados Eye Study found that decreased OPP and BP increased the risk of glaucoma development by up to six times. Reduced retinal perfusion with resultant thinning of the RNFL in conditions with a similar mechanism, such as obstructive sleep apnoea syndrome, has indicated the importance of reduced OPP in retinal thickness. In the absence of any study directly showing the effect of systemic hypotension on OPP and retinal thickness, a working hypothesis proposes that reduced BP with or without normal-to-raised IOP will reduce OPP. The reduced OPP and OBF in those with systemic hypotension may result in oxidative stress and hypoxia which may then cause retinal ganglion cell death and the resultant retinal thinning.Conclusion: The increased risk of glaucoma development and progression relating to decreased BP and OPP has been proven to be of importance. Monitoring patients with systemic hypotension and evaluating the macula, ONH RNFL and GCC thickness may alert clinicians to possible glaucomatous changes.
Low ocular perfusion pressure (OPP) may increase the risk of optic neuropathy. This study investigated the effects of OPP on the ganglion cell complex (GCC) and optic nerve head-retinal nerve fibre layer (ONH-RNFL) thickness in presumed systemic hypotensives (PSH). Fifteen participants with PSH and 14 controls underwent automated sphygmomanometry and Icare tonometry to calculate OPP: mean OPP (MOPP), systolic OPP (SOPP), and diastolic OPP (DOPP). ONH-RNFL and macula GCC thickness were evaluated using the Optovue iVue optical coherence tomographer. Statistical analysis comprised independent t-tests, the Mann–Whitney U test and binary logistic regression analysis. There was no significant difference when comparing ONH-RNFL and macula GCC thickness between both groups. Increased MOPP (OR = 0.51; 95% CI: 0.27–0.97; p = 0.039) and SOPP (OR = 0.79; 95% CI: 0.64–0.98; p = 0.035) were significantly associated with a decreased risk of reductions in GCC total thickness. Increased SOPP (OR = 0.11; 95% CI: 0.01–0.89; p = 0.027) was significantly associated with a decreased risk of reductions in the average ONH-RNFL thickness. The study found no significant retinal thickness changes in PSH’s, in comparison to the controls. The study established that, by increasing MOPP and SOPP, there was a decreased risk of reductions in the total GCC thickness and average ONH-RNFL thickness. Higher SOPP may decrease the possibility of retinal thinning of the GCC and ONH-RNFL. However, higher MOPP may decrease the odds of thinning of the GCC before ONH-RNFL changes.
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