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Hsin-Hua Liu, Liwei Zhang, Lu Chen, John G Flanagan; Comparison of Laser- and Circumlimbal Suture-Induced Ocular Hypertension in Albino CD-1 Mice. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1067.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the intraocular pressure (IOP) profile and retinal changes induced by i. laser cauterization of the episcleral veins and limbal vessels and ii. circumlimbal suture, in CD-1 mice.
CD-1 mice were randomized to receive unilateral laser photocoagulation of the episcleral veins combined with 270° limbal vessels (sparing nasal 90°, n=9) or circumlimbal suture (10/0 nylon, n=31). IOP was measured immediately, 3 hours and 24 hours after treatment, daily for the next 6 days, and, for a sub-group of the suture model, every 3 days for the next 21 days. The suture group was divided into 3 sub-groups depending on the level of the IOP-spike immediately following suture placement, and the time period of monitoring (acute, n=8; chronic 7 days, n=11; chronic 28 days, n=12). Retinal nerve fiber layer (RNFL) thickness was measured using optical coherence tomography (OCT). Retinal ganglion cell (RGC) count was assessed using Brn3a staining (whole-mount).
In the laser group, IOP was 15.7 ± 1.4 mmHg immediately after treatment and 43.2 ± 2.9 mmHg at 3 hours, and it returned to baseline (17.0 ± 1.7 mmHg) by day 7. In all suture groups, IOP remained elevated at day 7. In the acute suture group, the IOP spike was 62.0 ± 2.9 mmHg and 48.2 ± 3.2 mmHg at 3 hours. The IOP spike was 43.2 ± 3.7 mmHg for the chronic suture 7 day group (33.8 ± 3.8 mmHg at 3 hours) and 45.0 ± 3.8 mmHg for the chronic suture 28 day group (35.2 ± 2.3 mmHg at 3 hours). At day 28, IOP was 18.5 ± 1.2 mmHg in the sutured eyes and 15.8 ± 0.8 mmHg in the control eyes. At day 7, RNFL was reduced by -14% ± 4% in the laser group, -3% ± 1% in the chronic suture group (significantly less than the laser group; p<0.001), and -23% ± 3% in the acute suture group, (significantly higher than the laser group; p<0.001). A similar result was found for the RGC count at day 7 (laser group: -32% ± 3%; chronic suture group: -5% ± 2%; acute suture group: -47% ± 6%). In the chronic suture 28 day group, a progressive loss of RNFL was observed (-5% ± 2% at day 14; -9% ± 2% at day 28). The loss of RGCs was -19% ± 6% at day 28.
The laser and suture models were both able to induce inner retinal defect in CD-1 mice. The acute suture model generated rapid loss of RGCs when compared to the gradual loss caused by the chronic suture model. The laser model appeared to be more acute in nature, giving a rapid loss in RNFL thickness and RGCs.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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