Bullous spectaculopathy is not a frequently seen eye problem in snakes, however it is definitely a challenging one to cure successfully.
Some ophthalmic diseases have been well described in snakes for a few decades now. Bullous spectaculopathy was probably first published by Frye in 1991 (Biomedical and surgical aspects of captive reptile husbandry). Ever since then, only few authors discussed this eye problem.
Snake eyelids become fused during the embrionyc development, making a transparent skin structure covering the actual cornea. Produced tear is normally transparent, water-clear fluid, which makes a film between the spectacule (fused eyelids) and cornea. Glands of the eyes are producing tear constantly that is then drained through the nasolacrimal duct and ultimately enter into the oral cavity. As spectacules are covering the cornea tightly, tear can not expose to outworld, it can only leave towards the oral cavity.
Bullous spectaculopathy has been known in snakes for some time by US authors. The decisive step in pathogenesis is the blockage of nasolacrimal duct. Therefore, permanently excrating tear will accumulate in the subspectacular space. This will lead to bulging of the eye area, while the inner structures of the eye will be pushed towards the ipsilateral eye. Blockage of the nasolacrimal duct may due to several reasons, but stomatitis and gingivitis are the most frequently seen disorders associated with that particular eye problem. Millichamps also publised a case, where a blood python (Python curtus) had congenital agenesis of the duct. Fluid accumulated in the subspectacular space can rarely be pus or blood, as well.
The widely-accepted protocol for treatment of this eye disorder is the excision of an edge-shaped portion of the lower spectacule, making the tear (or other fluids) free to go from the subspectacular space. However, full recovery without reoccurence can only be expected by making sure that the nasolacrimal duct is passable. Accordingly, as long as stomatitis or gingivitis is suspected to be the cause, one should treat it vigorously. In case of congenital agenesia of the duct, an artifical drainage should be created to drain the tear from the subspectacular space into the oral cavity, which is a challenging procedure for even experienced veterinary surgeons.
Own case and its treatment
I consider this disorder rather rare, as I had not seen a single case in 20 years either in my collection, nor in praxis.
Few weeks ago, I noticed in one of our captive-born baby boas that one of the eyes looked darker from a certain perspective. I did not attach great importance to it at this point. However, the boa's eye disorder was showing slow, but sure progression. By time, the accumulation of transparent fluid (tear) in the subspectacular space became visible, which had changed the diffraction of eye making it look darker from distance. It was also noticable that the inner structures of the eye were pushed inside (towards the ipsilateral eye) by the fluid. Once examined the oral cavity and revealed the disorder there, it had become obvious that bullous spectaculopathy was secondary due to obstruction of nasolacrimal duct.
Those few publications that described this eye disorder to date were suggesting excision of 30 degree edge-shaped portion of the spectacule, however I had to make adjustments for the following reasons:
1. That particular specimen was as tiny as 45 cm in length and 56 gram in weight, making the classic edge-shaped excision without microsurgery instrumentals impossible.
2. By partial removal of the spectacule, constant supplementation of tear by artifical tear would have been necessary to avoid the cornea drying-up, that would have hardly been executed in practice.
3. By partial removal of the spectacule, even under the most hyginenic circumstances there would have been a higher risk for infection of the opened, partially spectacule-free eye.
After considering those mentioned above, the spectacule was disinfected and then perforated by a fine needle close to the lower end. The incision of 3mm was just sufficient to remove the majority of viscous, dense tear by gently pushing the eyeball. After that, antibiotic eye-drops (ciprofloxacin) were introduced into the subspectacular space to prevent infection, knowing that systemic-applied antibiotics hardly reach proper concentration in the eye.
The tiny foramen that had been made on the lower spectacle closed quickly by itself, therefore artificial tear was not needed and the risk of possible contamination was also lower as opposed to classic excision leaving the cornea "open" for longer period.
Treatment of the eye was followed by treatment of the oral cavity. After disinfection, cystic gingivia was opened, debridement of the necrotic tissue was made, locally antibiotic (ciprofloxacin) was applied. Nevertheless, due to the disorder of the oral cavity I also started a broad-spectrum systemic antibiotic treatment (ceftazidime, every two days, for 8 days).
During the following 3 days, reperforating the spectacule at the same site (!), tear removal, local antibiotic administration was reapeated. By day 4, the eye became practically sound. The local treatment of gingiva, as well as systemic antibiotic were continued for 8 days alltogether.
That particular specimen became completely sound regarding both the eye and gingiva in as short as 7 days.
Dr. Botond Ádám
CB 2016 Tumbes longtail boas
(Boa c. longicauda)details..