Relationship of the iridocorneal angle, as measured using ultrasound biomicroscopy, with post‐operative increases in intraocular pressure post‐phacoemulsification in dogs

OBJECTIVE: To investigate the relationship of the iridocorneal angle as it appears on ultrasound biomicroscopy (UBM) to increases in IOP post-phacoemulsification in the canine eye. Animals studied 47 eyes of 28 dogs of various age, sex, and breed. METHODS: The ciliary process and limbus were used as a reference points to measure the angle opening distance (AOD), which was set by multiplying 0.45 by the distance between the ciliary process and limbus (when measured from the ciliary process). Pressure measurements were taken at five set points: Before, immediately post-, one day post-, 1 week post-, and 1 month post-phacoemulsification. RESULTS: A weak relationship between the AOD and the IOP one day post-phacoemulsification (Intercept: 2.83, Slope: -1.24, P-value: 0.0155) was observed. No relationship immediately post-operative (Intercept: 3.45, Slope: -1.34, P-value: 0.0651), 1 week post-phacoemulsification (Intercept: 2.31, Slope: -0.01, P-value: 0.9829), 1 month post-phacoemulsification (Intercept: 1.85, Slope: -0.49, P-value: 0.1533) was observed. The pre-operative measurements made with UBM were: Distance from limbus to ciliary process (DLCP): (Minimum: 1.152, Maximum: 2.992, Mean: 1.91, SD: 0.468); AOD (Minimum: 0.104, Maximum: 0.764, Mean: 0.40, SD: 0.172). CONCLUSIONS: The relationship between AOD as measured by UBM pre-operatively is weakly associated with IOP pressure elevations at day one post-phacoemulsification. Further study is required prospectively to establish the importance of this relationship. Initial measurements of the canine iridocorneal angle were created, suggesting a method to be used in the future to establish true canine normal measurements.