Anterior Segment Measurements in Normal Cats Using Ultrasound Biomicroscopy

Establishing baseline ultrasound biomicroscopy (UBM) measurements of the feline anterior segment is essential for accurate evaluation of ocular diseases. This study aimed to establish normative UBM parameters in clinically normal cats and to assess the influence of sex, body weight, and age on these measurements. Twenty eyes from twenty healthy adult cats were examined using a standardized UBM protocol under general anesthesia to ensure consistent positioning and optimal visualization. Quantitative measurements were obtained for corneal, anterior chamber, iris, ciliary cleft, and ciliary body parameters. The mean perilimbal corneal thickness was 0.59 mm, anterior chamber depth was 4.11 mm, and peripheral anterior chamber depth was 3.11 mm. The angle-opening distance and iridocorneal angle measured 1.73 mm and 28.89°, respectively. Ciliary cleft parameters included a width of 1.22 mm, length of 2.07 mm, and area of 1.10 mm². Longitudinal and combined longitudinal-radial ciliary body thicknesses were 0.52 mm and 0.78 mm, respectively, while ciliary body axial length and ciliary process scleral angle averaged 2.01 mm and 58.98°. Iris base width and iris middle width measured 0.35 mm and 0.54 mm, respectively. Sex-based analysis revealed significant differences in peripheral anterior chamber depth and ciliary cleft width, whereas body weight showed positive correlations with iris thickness parameters. No significant associations were identified between age and any anterior segment measurements. These findings establish comprehensive normative UBM reference values for the feline anterior segment and provide a quantitative anatomical framework for future clinical and disease-oriented studies in feline ophthalmology.