The capybara eye: clinical tests, anatomic and biometric features

Area of Science:

• Comparative Ophthalmology
• Veterinary Anatomy
• Rodent Biology

Background:

• Limited established reference values exist for capybara (Hydrochaeris hydrochaeris) ocular parameters.
• Understanding normal capybara eye physiology is essential for accurate veterinary diagnosis and care.
• The capybara's unique characteristics suggest potential as a model organism in ophthalmic research.

Purpose of the Study:

• To conduct a descriptive investigation of the capybara eye.
• To perform ophthalmic diagnostic tests to establish normal physiological reference values for capybaras.
• To identify unique anatomical features of the capybara eye for improved pathological diagnosis.

Main Methods:

• Examination of 22 healthy capybaras (ages 2-4 years).
• Ocular diagnostic tests included Schirmer tear test, tonometry (Tonopen), and ultrasonic pachymetry.
• Measurement of axial globe length and culture of conjunctival bacterial flora were also performed.

Main Results:

• Normal ocular features identified: dorsal/ventral puncta, vestigial third eyelid, upper eyelid cilia, pigmented bulbar conjunctiva, oval/vertical pupil, absence of tapetum lucidum.
• Reference values established: Intraocular pressure 18.4 ± 3.8 mmHg, Schirmer tear test 14.9 ± 5.1 mm/min, Central corneal thickness 0.46 ± 0.03 mm, Axial globe length 22.20 ± 1.71 mm.
• Common conjunctival flora included Corynebacterium sp., Micrococcus sp., Bacillus sp., and Staphylococcus sp. No significant age or gender differences were noted.

Conclusions:

• The study provides comprehensive normal ophthalmic values and anatomical descriptions for capybaras.
• These findings aid veterinary ophthalmologists in diagnosing ocular conditions in capybaras.
• Similar corneal thickness and axial length to humans suggest the capybara as a valuable model for ophthalmic research.