Vol. 32, Nš 3

Effects of monocular deprivation on the thickness of neural retina

Mwachaka, P.; H. Saidi; P. Odula; Mandela, P.

KEYWORDS: neural retina, monocular deprivation, rabbit model.

ABSTRACT: Background: Monocular visual deprivation as a result of cataracts occurring in children who previously had normal vision may result in permanent visual deficits. However, if correction is done before the age of ten years, vision is usually restored to normal levels in the affected eye. This has been attributed to plastic changes that occur in the visual cortex, with no mention of the contribution of the retina to this plasticity. Objective: To describe the effect of monocular deprivation on the thickness of neural retina. Study design: Quasi-experimental study using a rabbit model. Materials and methods: 30 rabbits (18 experimental, 12 controls) were examined. Monocular deprivation was achieved through unilateral lid suture in the experimental animals. The rabbits were observed for three weeks. Each week, 6 experimental and 3 control animals were euthanized, their retina harvested and processed for light microscopy. In experimental animals, retina of both deprived (closed) and non-deprived (open) eyes were studied. Haematoxylin & Eosin stain was used to demonstrate the layers of the retina. Photomicrographs of the retina were taken using a digital camera then entered into FIJI software for analysis. Results: In the deprived eyes, the neural retina thickness reduced by 40.5% from the baseline (p = 0.001). Compared to controls, statistically significant reduction in thickness was noted in the ganglion (p < 0.001), inner nuclear (p < 0.001), rod and cones (p = 0.001), outer plexiform (p = 0.008), nerve fiber (p = 0.010), and inner plexiform (p = 0.024) layers. Among the non-deprived eyes, the neural retina thickness increased by 9.8% from baseline (p = 0.075). Compared to controls, statistically significant increase in thickness was seen in the inner plexiform (p < 0.001), inner nuclear (p = 0.002), and rods and cones (p = 0.007) layers. Conclusion: Monocular deprivation results in atrophy of the retina in the deprived eye. Thus, pre-retinal causes of blindness such as cataracts affects the retina and should be corrected early so as to minimize damage to the retina of the deprived eye.