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Updated: Feb 4, 2026

Intravitreal Injections in the Ovine Eye
Published on: July 5, 2022
An experimental study to evaluate safety/toxicity of intravitreal natalizumab
Rohan Chawla1, Madhu Nath2, Laxmi Moksha2
1Department of Ophthalmology, Dr. Rajendra Prasad Centre for Ophthalmic Sciences, New Delhi, India.
Purpose:
The purpose of this prospective experimental study was to evaluate the safety/toxicity of α4β1 integrin blockade in rabbit retina using its monoclonal antibody (Natalizumab).
Methods:
Twelve New Zealand albino rabbits were divided into three groups (n = 4). Unilateral intravitreal injections of three different concentrations of natalizumab were performed in every rabbit of each group (Group A: 0.625 mg, Group B: 1.25 mg, and Group C: 2.5 mg). Baseline electroretinogram (ERG) and fundus photography were performed prior to injection. At days 1, 7, and 21 postinjection, ERG and fundus photography of each eye were performed. At last follow-up, Group C animals with highest drug concentration were sacrificed and the enucleated eyes were evaluated for retinal toxicity using transmission electron microscopy (TEM).
Results:
No difference in ERG responses was observed in eyes injected with low and intermediate concentration of natalizumab between day 0 and day 21. Furthermore, rabbits injected intravitreally with highest dose showed reduction in amplitude of "a" wave (P = 0.0017) and a reduction in amplitude of "b" wave of ERG at day 21 (P = 0.0117). TEM revealed changes in the outer plexiform layer and inner nuclear layer, suggestive of toxicity primarily to the photoreceptor synaptic terminals and bipolar cells.
Conclusion:
Low-dose (0.625 mg) and intermediate-dose (1.25 mg) intravitreal injection of natalizumab appears safe for rabbit retina. However, functional and anatomical changes were observed in rabbit retina following a high-dose (2.5 mg) intravitreal injection of a monoclonal antibody blocking α4β1 integrin.
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