Bulging, Drooping, Distended Eyes in Reptiles
There is nothing more terrifying for a reptile keeper than to see their reptile's eye bulging out or drooping. Fortunately, not all such bulging or distensions are serious. Unfortunately, many are.
©2001 Melissa Kaplan
The reptile eye is similar in many ways to the mammalian eye. They have a lens, cornea, retina, sclera, vitreous humor. Snakes and some lizards have a spectacle instead of a moving eyelid. Like the skin on moveable eyelids, spectacles shed their top layer during each shed event. The reptile iris contains striated muscles, rather than the smooth muscle found in mammalian eyes; this makes it difficult to impossible to dilate the pupils for in-depth examination of the inner eye structures using drugs typically employed for this purpose. A topical application of a non-depolarizing relaxant can be used in reptiles with moveable eyelids, something your vet is probably already familiar with in examining birds eyes. In spectacled species, injections of curare will be needed.
Lizards and chelonians have a nictitating (third) eyelid, as do crocodiles. These can make examination difficult as this eyelid slides across automatically to protect the eye itself.
Most reptiles have tear ducts (lacrimal canaliculus). Lizards and crocodilians also have nasolacrimal ducts which drain out near the vomeronasal organ (Jacobson's organ). In snakes, the nasolacrimal ducts drain into the vomeronasal organ. The fluid then drains down into the mouth to be swallowed. It has been reported that chelonians do not have a nasolacrimal duct, but there is some evidence to the contrary.
Information on vision can be found in my Reptile Vision article.
There are veterinary ophthalmologists who specialize in diseases of the eye. Since reptiles are not covered extensively in general veterinary classes, it will not be a surprise to find that there are likely very few veterinary ophthalmologists who specialize in reptilian eyes. Thus, when you need need to see your reptile veterinarian for one of the conditions below, do start with your reptile vet. If he or she cannot figure out what is going on, check into seeing if there is a veterinary ophthalmologist in your area with whom you can consult.
Early on, there is some swelling of the eyelid, some mild welling around the iris, and some tearing of the eye in cases of hypovitaminosis A. In addition, there are changes in the orbital glands. As the condition progresses untreated, the swellings become more pronounced and the conjunctiva becomes visible, swollen and reddened. Reptiles that depend upon sight to feed can no longer see well enough to feed, and so slow starvation sets in, further weakening the reptile.
Along with the necessary correction of the diet and environment, and the administration of vitamin A, the cellular changes in the cells of the eye predispose the already stressed reptile to infection, so the application of a suitable topical antibiotic ointment is recommended. During recovery, artificial tears may also be useful.
Ciprofloxacin and similar opthalmic drops have been recommended over gentamicin drops because of a reported epitheliotoxic (kills epithelial cells) effect of the latter.
Ticks, commonly found on wild-caught reptiles or captive bred ones in direct or indirect contact with wild-caught reptiles, can often be found snugged up near the eye. Various nematodes find the conjunctival sac of lacertid lizards and chelonians compatible with their needs. If you have to ask how to remove them properly, completely, and safely, see your reptile vet.
Eyelids - Pre-Shed
Later, once the old skin is ready to break and start coming off, the lizards will often rub their closed eyes against something in their enclosure or area. This might be to soothe an itch associated with the coming shed, or might be done to help gently break the skin so that the final step in the shedding process can begin, that stage where you lizard looks like it has bits of cloth stuck to its eyelids, waving gently in the breeze.
In chelonians, swollen eyes may also be associated with infected eustachian tubes. Since chelonians fed a proper diet rarely get vitamin A deficiencies, such swellings are rarely resolved by increasing vitamin A orally or by injections. If your vet immediately diagnoses a vitamin A deficiency without doing anything to check for infection, or doesn't appear to be up on proper diet, it would be best to get a second opinion from another reptile vet.
The number of reports in the literature of periocular disease with infectious origin as compared with disease of which an agent could not be isolated may not necessarily reflect the actual incidence of infectious and noninfectious inflammatory disease. David L. Williams, M.A., VetMB
Because of the proximity and interaction of the ocular structures to the mouth and respiratory tract (through the nasolacrimal ducts draining into the mouth, near or through the vomeronasal organ; tearing and exudates from the eyes), early signs of a potentially serious problem may present with both mild swelling and tearing and early signs of respiratory infection.
Diseases of the Eye
Other Diseases of
In addition to retained spectacles, drainage problems in the ducts associated with the eye can occur, resulting in fluid buildup, swelling, cysts, and abscesses. Left untreated too long, and the eye may need to be removed. Abscesses in the eye structures may be caused by an infection in the mouth or surrounding areas of the head.
Note that in the case of eye infections caused by any of the above, the eye's involvement is secondary to a more serious underlying systemic infection. This is one of the most important reasons why it is important to not try to treat eye conditions at home: you may well end up wasting valuable time, seriously weakening your reptile, to the point that when veterinary intervention is finally sought, it is too late to save the reptile.
Primary source: Williams, David L. 1996. Ophthalmology. In Reptile Medicine and Surgery, Douglas R. Mader, editor. pp 175-185
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