Exotis ISSN 2398-2985

Reptiles

Corneal / spectacle opacity

Contributor(s): Vetstream Ltd, David Vella

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Introduction

  • Cause: corneal ulceration, keratitis, ecdysis, retained spectacle, trauma, corneal lipidosis, post-hibernation lipidosis.
  • Signs: dull/opaque cornea/spectacle.
  • Diagnosis: clinical signs.
  • Treatment: depends on cause; assess individual’s diet. 
  • Prognosis: favorable if underlying causes addressed and appropriate therapy offered.
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Pathogenesis

Etiology

  • The normally clear spectacle may become opaque for several reasons.
  • Most commonly before ecdysis in snakes. The spectacle becomes opaque, as fluid increases to separate the old spectacle from the newly formed tissue underneath:
    • The whole skin becomes dull for the same reason and this is a normal appearance at the time of ecdysis.
    • Most commonly just before shedding occurs the spectacle clears, confirming that this is part of the snake’s normal growth.
    • Should retention of the spectacle occur some opacity may occur, but this is not the dense white of the shedding spectacle, rather a dull lustreless appearance Retained spectacle.
    • Retained spectacles most often result from a too dry environment or dehydration. They can also result from ectoparasitic mite infestation, eg Ophionyssus spp.
  • Infection:
    • Keratitis in tortoises may be the result  of bacterial infection (typically Pseudomonas spp, Moraxella spp or Aeromonas spp; this is considered infectious and contagious.
  • Trauma:
    • Cornea: corneal trauma may lead to ulceration and subsequent infection and/or scarring.
    • Spectacle: given that the whole point of the spectacle is to protect the underlying cornea, continued mild trauma can lead to scratches on the spectacle, indentation of the surface or more severe pigmentation. Such opacification is not of concern, however, since the new spectacle revealed after shedding will be clear and transparent.
    • Bullous spectaculopathy Bullous spectaculopathy (pseudobuphthalmos), where a fluid accumulation distends the subspectacular space, can also lead to opacification possibly from trauma, although in many cases the distended spectacle is clear.
  • Chelonia with a systemic circulating lipidemia, either through an inherited dyslipoproteinemia or a dietary hyperlipidemia, can develop corneal lipidosis which is not dissimilar from that seen in the dog. The lesions appear as diffuse milky white color, but at higher magnification individual lipid crystals may be evident.
  • A denser much more homogeneous white corneal lesion may be seen in reptiles, and particularly chelonia, after hibernation. It has been reported that these can be dissolved using Kymar ointment, a preparation of alpha chymotrypsin, suggesting that this lesion is proteinaceous in nature.

Predisposing factors

General

  • Hibernation (chelonia).
  • Nutritional.

Specific

  • Excessive dietary polysaturated fats may lead to corneal lipidosis.

Timecourse

  • Development during hibernation in some cases.

Epidemiology

  • Bacterial keratitis in tortoises is considered infectious and contagious.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

Other sources of information

  • Williams D (2012) The Reptile Eye. In: Ophthalmology of Exotic Pets. Wiley-Blackwell, UK. pp 174-175 & 184-185.

Reproduced with permission from David L Williams: Ophthalmology of Exotic Pets © 2012, published by John Wiley & Sons.


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