Ophthalmological and ecobiometric parameters in pampas fox (Lycalopex gymnocercus) and crab-eating fox (Cerdocyon thous)

Abstract

Since ophthalmic data may differ between species, this study evaluated the ophthalmological and ecobiometric parameters in Lycalopex gymnocercus and Cerdocyon thous, and compare them with the values already described for wild and domestic canids. Twelve captive healthy wild canids were selected, including six L. gymnocercus (six females) and six C. thous (four males, two females), ages ranged from two to four years. The ophthalmic examination was performed under chemical restraint. Values of Schirmer tear test I (mm/min), intraocular pressure (mmHg) measured by rebound tonometry, and central corneal thickness (µm) determined with ultrasonic pachymetry were: 3.50 ± 0.84, 11.83 ± 2.06 and 548.83 ± 13.64 for L. gymnocercus, and 5.67 ± 3.08, 11.89 ± 3.17 and 531.83 ± 59.78 for C. thous. Anterior chamber depth, lens thickness, vitreous chamber depth, and axial globe length measured (mm) by B-mode ultrasound were: 3.32 ± 0.19, 6.58 ± 0.23, 6.82 ± 0.43 and 17.20 ± 0.73 for L. gymnocercus, and 3.45 ± 0.23, 6.40 ± 0.19, 6.63 ± 0.29 and 16.53 ± 0.30 for C. thous. L. gymnocercus had a yellowish-green tapetal fundus, while C. thous had a predominance of bluish-green coloration. In conclusion, the ophthalmological and ecobiometric parameters were similar in L. gymnocercus and C. thous, except for tapetal fundus color. The ecobiometric parameters compared to domestic dogs indicated that both wild canids presented a shallower anterior chamber, less lens thickness, and smaller ocular globe size.