Effect of Acute Intraocular Pressure Reduction on Vascular Density and Perfusion of Optic Nerve and Macula as Measured by Optical Coherence Tomography Angiography.

Abstract

Purpose : Optical coherence tomography angiography (OCTA) qualitatively assesses the microcirculation within the optic nerve and macula. Vascular density quantification is also measured with this technique. Long-standing ocular hypertension can lead to a varied chronic structural change including the capillary bed. Although a decreased intraocular pressure (IOP) due to antiglaucoma therapy may improve perfusion of the optic nerve, it would be desirable to know if an abrupt reduction in IOP could have an effect on the microcirculation. The objective of this study is to investigate the effect of two clinical settings of abrupt IOP reduction on OCTA variables in the ON and the macula.

Methods : Eighteen eyes of 18 non-consecutive patients which underwent either a bleb needling (BN) procedure or post-trabeculectomy digital compression (DC) were evaluated by applanation tonometry, ON and macula OCT, and OCTA. Baseline measurements were followed by any one of the ocular hypotensive maneuvers. The studied variables were cup to disc (CD) ratio, thickness of retinal nerve fiber layer (RNFL), thickness of the ganglion cell complex (GCC), and perfusion (ONP) and flux index (ONFI) of the optic nerve, as well as perfusion (MP) and vessel density (MVD) of the macular area.

Results : Patients included in the study (10 males, 8 females) had a mean age of 61.9±17.7 years. A post-procedure IOP (9.4±4.7 mmHg) was significantly less (p=0.0001) than before the procedures were carried out (23.1±8.9 mmHg). No significant changes in the RNFL, GCC, and CD ratio were found before and after the procedures, neither in the intervened eyes nor in the control ones. Pre-procedure ONFI (0.3±0.65), MP (63.6±7.2) and MVD (16.0±3.6) were significantly different (p=0.01, p=0.03, and p=0.0001; respectively) as compared to post-procedure values (0.37±0.04, 62.7±8.0 and 17.3±2.6), but not with ONP (40.1±3.8 vs. 40.1±3.2; p=0.89). IOP reduction was inversely correlated with pre- (r=-0.62; p=0.005) and post-procedural ONFI (r=-0.56; p=0.01), as well as pre-MVD (r=-0.6; p=0.007).

Conclusions : Acute IOP decrease after either BN or DC, is associated with a modest but significant change in several OCTA variables (ONFI, MVD, MP). The clinical impact of such microvasculature changes is still a matter to be elucidated.

This is a 2021 ARVO Annual Meeting abstract.