Abstract
Purpose: :
To evaluate the changes of the retinal nerve fiber layer (RNFL) in the chronic glaucoma rats using optic coherence tomography (OCT) and the histological examination.
Methods: :
Chronic elevation in intraocular pressure (IOP) was induced unilaterally by laser trabecular meshwork photocoagulation in 48 female Wister rats, the opposite eye served as a control. The IOP was measured before laser photocoagulation and weekly thereafter, with Tono–Pen Tonometer. OCT was performed in the 3rd, 6 th and 9 th week, at the same time, IOP was evaluated in both eyes. The OCT images were analyzed for retinal nerve fiber layer. Eyes were nucleated and retina was examined histologically at the 3rd, 6 th and 9 th weeks, respectively.
Results: :
IOP was elevated chronically and moderately in laser photocoagulation eyes. The mean IOP was 25.56 ± 4.32 mmHg, 26.64±4.64 mmHg and 27.64±4.28 mmHg in laser treated eyes and 12.75±3.78 mmHg, 13.12±3.64 mmHg and 12.98±3.59 mmHg in the control eyes at the 3rd, 6th and 9th week, respectively. The RNFL thickness, measured by OCT, was 67.39±5.91µm, 53.42±5.64µm and 44.35±5.76µ in laser treated eyes and 76.23±6.78µm, 78.64±6.15µm and 77.64±6.63µm in the control eye at the 3rd, 6th and 9th week respectively. Histological examination showed that the thickness of the retinal nerve fiber layer was 64.38±6.54µm, 51.47±6.41µm and 42.10±6.10µm in the glaucoma eyes and 80.32±5.87µm, 79.69±5.69µm and 80.78±5.84µm in the control eyes at the 3rd, 6th and 9th week respectively. There was a linear correlation between the RNFL thickness measured by OCT and by histological method in the chronic glaucomatous rat model (r=0.932, p<0.001).
Conclusions: :
An experimental rat glaucoma model was established successfully by laser trabecular photocoagulation. In the hypertensive eyes, the retinal nerve fiber layer thinned with the passage of time. OCT appeared to be a reliable method to evaluate the changes of the RNFL thickness in vivo.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • intraocular pressure • nerve fiber layer