Ocular hypo pressure treatment in rats with chronic glaucoma: Refractive, functional and structural neuroretinal study

Abstract

Purpose: To evaluate the effect of ocular hypo‐pressure treatment on refraction and neuroretina of rat eyes with chronic glaucoma by sex over 24 weeks, as compared to glaucomatous rats non‐treated and healthy controls. Methods: One hundred and fifty five Long‐Evans rat's eyes were analysed retrospectively. 25 glaucomatous (G) rat's eyes, 60 glaucomatous eyes treated with a hipo pressure formulation of Brimonidine ‐ LAPONITE® (G‐B) and 70 healthy (H) eyes. Intraocular pressure (IOP) was measured with rebound tonometer, retinal ganglion cells (RGC) functionality with electroretinography (ERG), and diopter power (D) and neuroretinal estructure with peripapilary retinal nerve fibre layer (pRNFL) and ganglion cell layer (GCL) protocols using non‐invasive technology of optic coherence tomography, over 6 months. Results: G‐B cohort presented lower IOP values during weeks 1, 4 and 8 (p < 0.001) compared to G cohort no treated, and even to H eyes during first week (10.36 ± 1.21 vs. 13.37 ± 2.58 mmHg; p < 0.001). All cohorts both sexes experienced a trend to emmetropia throughout the follow‐up, especially throughout the first 8 weeks of the study and in males (p < 0.033). G cohort showed the lowest diopter value (1.06 ± 3.94 D; p < 0.035), G‐B cohort showed the biggest value and no differences in refraction compared to H eyes (3.67 ± 0.00 vs 3.61 ± 1.90 D; p > 0.203) in week 24. pRNFL thickness differences were mainly found on the inferior sectors. G‐B cohort showed bigger thickness in pRNFL (p = 0.034) and GCL (p = 0.038) compared to G cohort at week 24. G‐B cohort registered higher ERG signal compared to G cohort (41.20 ± 8.75 vs. 18.68 ± 24.77 μV; p = 0.012) and even H eyes (41.2 ± 8.75 vs. 26.00 ± 22.50 μV; p = 0.001) at week 24. Conclusions: Ocular hypo pressure treatment slowed the trend of diopter power and neurorretinal thickness loss, and preserved better functionality of RGC compared to glaucomatous eyes non‐treated.