Assessment of a model using ocular rigidity to predict the magnitude of IOP spikes following intravitreal injections

Abstract

Purpose : Therapeutic intravitreal injections (IVI) of anti-vascular endothelial growth factor (VEGF) agents for exudative retinal diseases are common and effective but are also known to lead to signification intraocular pressure (IOP) spikes, which could lead to glaucomatous optic nerve damage. In this study, we assess the accuracy of a model to predict the magnitude of acute IOP elevation following intravitreal injections using a non-invasive measurement of ocular rigidity.

Methods : This is a prospective, cross-sectional study involving subjects with pre-existing retinal conditions requiring treatment with IVI of anti-VEGF.
Ocular rigidity (OR) was assessed by the measurement of the pulsatile choroidal volume change using video-rate optical coherence tomography (OCT) imaging of the choroid and automated segmentation, as well as the pulsatile IOP change using dynamic contour tonometry. IOP was then measured using Tono-Pen XL before and immediately following the injection of Bevacizumab (1.25 mg, 50 microliters). A linear regression model was calculated to predict IOP spikes from the OR coefficient. A second group of subjects was used to test the predictive capability of the model. Those patients underwent non-invasive OR measurement by one observer. The magnitude of IOP spikes was predicted using the model by that same observer. IOP spike measurement using the Tono-Pen XL was carried out by a second, masked observer, and later compared with the predicted value.

Results : Sixteen participants, aged 67±10 years, were recruited in the first group. Baseline IOP was 17±5 mmHg. The average increase in IOP following IVI was 19±5 mmHg. The calculated regression line was IOP spike = 730.33 mmHg.microliter x OR + 2.95 mmHg. The Spearman correlation coefficient between OR and IOP elevation following IVI was 0.810 (p<0.001), showing higher IOP elevation in more rigid eyes.
In the first patient recruited for the second part of the study our model predicted an IOP spike of 9.9mmHg following IVI, while a spike of 10.0 mmHg was actually measured , a difference of only 0.1mmHg. Recruitment for the second part of this study is ongoing.

Conclusions : This study proposed a model to predict the magnitude of IOP spikes following IVI using the OR coefficient and assesses its predictive accuracy. Clinical applications of the measurement of ocular rigidity may be numerous.

This is a 2020 ARVO Annual Meeting abstract.