VN April 2022

Vetnuus | April 2022 30 Regulars I Ophthalmology Column In this article, we will briefly discuss three frustrating ophthalmic problems encountered in rabbits. 1]Dacryocystitis and Epiphora The incidence of nasolacrimal duct (NLD) obstruction is considered to be 1:30 in normal domestic rabbits. This problem generally occurs in rabbits from 4 years of age. In rabbits, the lacrimal duct system starts with the single punctum located at the medial part of the lower eyelid and then courses across both the molar and incisor teeth. Dental problems probably related to dietary calcium deficiency may result in the obstruction of the duct. Any maxillofacial bone abnormality, [nutritional hyperparathyroidism], molar tooth root abscess, or overgrown incisor teeth may well lead to NLD pathology resulting in dacryocystitis or epiphora. Performing a dacryocystorhinography contrast study may assist with the diagnosis of obstruction. Taken from Veterinary Ophthalmology, 6 th Edition. A. The anatomy of the normal nasolacrimal duct in the rabbit. (Source: With kind permission from Burling, K., Murphy, C.J., Curiel, J.S., et al. (1991) Anatomy of the rabbit nasolacrimal duct and its clinical implications. Progress in Veterinary and Comparative Ophthalmology, 1, 33–40.) B. Dacryocystorhinogram shows dilation of the nasolacrimal duct through a blockage. Other causes that frequently result in a purulent ocular discharge and sometimes a swollen medial canthus region can include infections with Pasturella, Neisseria, Moraxella, Bordetella, Streptococcus, Oligogellla and Pseudomonas. Often secondary periocular dermatitis may be noted. In such cases, it is vital to take a swab, culture and antibiogram, and one can attempt to cannulate the lacrimal punctum. In order to cannulate the punctum, it is best to apply a small amount of pressure at the medial canthus, and the opening tends to “pout” outwards and can then be cannulated. The procedure is not easy to perform. In the case of a purulent situation, it may be necessary to performmultiple flushes and to use an antibiotic eye drop. Stay away from greasy ointments as one wants maximal drainage of the medication into the nasolacrimal duct system. 2] Corneal ulcers The rabbit eye is laterally placed in the head. It is very protuberant with a large exposed surface and thus is frequently damaged by external trauma resulting in a corneal ulcer. In most cases, rapid healing occurs in about seven days. The use of a good quality antibiotic and lubricant should be sufficient. If you are presented with a severely infected eye with extensive yellow coloured cellular infiltrate in the corneal ulcer and corneal stroma, it would be good to take a swab for culture and antibiogram. If a superficial erosion is not healing, it may be due to poor adhesion between epithelial cells and the basement membrane, such as indolent or epithelial dystrophy cases in dogs. The same phenomenon occurs in rabbits, and one could attempt to debride the lesion with a cotton bud. Still, a slightly more aggressive approach is Exotics – Rabbits Dr Antony Goodhead, Specialist Veterinary Ophthalmologist, Johannesburg and Cape Animal Eye Hospitals, www.animaleyehospital.co.za