Understanding the spectacle
Snakes do not have eyelids. Instead the eyelids are fused to form a clear scale that covers the cornea (Sivak 1977). This clear scale is commonly called the spectacle. The spectacle is also known as the brille, ocular scale, or “eye cap”.
As the snake prepares to shed, lymphatic fluid collects between the superficial, older layer of skin and a new layer of skin. Lymph causes the spectacle to turn a light, semi-opaque blue, which is often described as “in blue” (Fig 1).
Immediately before shedding, the spectacle becomes clear again (Mader 1996). When a snake undergoes a shed or dysecdysis, the spectacle is sloughed along with the rest of the superficial layer of skin (Figure 2).
Each shed skin should be examined to ensure the spectacles come off, although be sure to remind owners that shed skin can serve as a potential zoonotic risk (Fig 3).
Like other shedding problems, retained eye caps are a sign of an underlying problem related to patient health or husbandry. If retained spectacles are not removed, they can interfere with vision, damage the eye, and/or serve as a source of infection (Mader 1996).
Key points of urgent care
While retained eye caps are not an emergency, this potentially serious condition should always be addressed when recognized (de la Navarre 2006).
Primarily a disease of captive reptiles, retained eye caps are sometimes seen in snakes and some gecko species like the crested gecko (Rhacodactylus ciliatus) (Stahl 2013).
Note: Leopard geckos (Eublepharis macularius) possess an eyelid, and therefore lack a spectacle.
- Obtain detailed information on the patient’s medical history as well as husbandry, including including cage temperature and relative humidity.
- When did the last shed occur?
Retained spectacles appear dry and dull, and the skin surrounding the eyes can also be affected. Underlying ocular structures may not be visible. Retained spectacles can be a unilateral or bilateral problem.
Postpone physical examination if the reptile appears to be in the midst of a shedding cycle. Handling reptiles, particularly snakes and some geckos, during a shed can cause skin damage and subsequent dysecdysis (de la Navarre 2006).
Use magnification, when available, to evaluate the retained eye cap in detail. Magnification also helps in screening the patient for ectoparasites as retained eye caps are a common area for snake mites to be found.
- Normal anatomy: The spectacle of some species like the ball python (Python regius) normally have a wrinkled appearance that should not be confused with retained eye caps.
- Bacterial or fungal dermatitis
- Underlying ocular disease
- Mass lesion
Keratoacanthoma of the spectacle has been reported in a boa constrictor (Genus species) (Hardon 2007).
The decision to obtain a minimum database upon initial presentation will vary with the patient’s history and physical examination findings (Box 1). Simple or uncomplicated cases often respond to symptomatic treatment. Whenever possible, refer the patient that does not respond to treatment to an experienced reptile veterinarian for a complete medical workup and advanced therapeutic techniques.
Box 1. Minimum database for the patient with dysecdysis
Employ a gentle, conservative approach to the management of retained eye caps. Attempts to prematurely remove retained ocular scales can permanently damage and scar the new layer of skin, or even structures of the eye. The goal of conservative treatment is to allow the retained spectacles(s) to come off during the next shed cycle.
- Moisten and hydrate the eye capsRegular and frequent administration of sterile ophthalmic lubricant can be used to moisten the spectacle.Supplemental treatments can include warm water soaks, humidity boxes, and/or application of small amounts of 10% acetylcysteine solution (Mucomyst, American Regent Laboratories) to the affected spectacle.
- Correct husbandry deficienciesEducate the owner on the proper relatively humidity, cage temperature, and cage furniture that should be provided.Although additional techniques for retained eye cap removal are described in the literature, they will not be listed here. Instead refer the patient that does not respond to conservative treatment to an experienced reptile veterinarian. In chronic or complex cases, it can be difficult to remove only the retained eye caps and not underlying structures (de la Navarre 2006).
The prognosis for reptiles with retained eye caps is very good in simple or early cases as long as gentle, appropriate treatment is provided.
Hollingsworth SR. Comparison of ophthalmic measurements obtained via high-frequency ultrasound imaging in four species of snakes. Am J Vet Res 68(10):1111-1114, 2007.