Abstract
Purpose :
Microcirculatory changes at both the peripapillary and macular regions have been reported to occur in glaucoma patients. The temporal association between retinal ganglion cell (RGC) loss and vascular changes remains unknown. We hypothesize that acute elevation of intraocular pressure (IOP) using the minimally invasive circumlimbal suture model is associated with vascular changes in the murine retina.
Methods :
Single eyes of adult male C57/Bl6 mice (n = 15) were subjected to the circumlimbal suture method of inducing ocular hypertension (OHT eyes). Contralateral unoperated eyes were used as a control. Briefly, a single 10/0 nylon suture was threaded subconjunctivally and clamped with a needle-holder for 30 min before the suture was cut. IOP was recorded at the start of clamping and every 5 min thereafter until after the suture was cut. Fundus fluorescein angiography (FFA) was performed at baseline, day 1 and week 1 after acute IOP elevation. Color fundus photography (FP) was done at baseline, immediately after IOP elevation, day 1 and week 1 after IOP elevation. Optical coherence tomography (OCT) of the peripapillary retinal nerve fibre layer (RNFL) and ganglion cell complex (GCC) was performed. Flatmount staining of RGCs was done to quantify cell density using rbpms 4 weeks after IOP elevation.
Results :
Cumulative IOP over 30 min was 294.33 ± 56.48 mmHg in the operated eyes and 64.60 ± 11.68 mmHg in the fellow eyes (p < 0.01). Maximum IOP was 77.89 ± 14.03 mm Hg. FFA showed fluorescein leakage beneath the major blood vessels in the retina in 9/15 eyes, although there was no evidence of hemorrhage on FP. Comparison of FP at baseline, immediately after IOP elevation, 1 day and 1 week afterwards did not show any changes in vessel morphology or fundus color. OCT measurements of RNFL or GCC thickness, and RGC counts in flatmounts did not show any significant difference in OHT and control eyes.
Conclusions :
Our results show that acute experimental IOP elevation is associated with subclinical capillary leakage in the retina. It is possible that vascular dysfunction may exacerbate RGC injury from raised IOP. Further work will be carried out to determine if haemodynamic changes can influence the extent of capillary leakage or alter RGC function in this OHT model.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.