Analysis of factors of variation in lens equatorial length and axial globe length measurements using ultrasonography in dogs with cataract

Abstract

Summary Purpose To evaluate biological variation of lens equatorial length (LEL) and axial globe length (AL) measurements on B-mode ultrasound and to calculate a formula to predict LEL using AL. Methods Ocular ultrasonography was performed in dogs with cataract, divided into study (n = 40) and control (n = 30) samples. LEL and AL were measured on images obtained at 10 MHz (AL, LEL10) and 35 MHz (LEL35). Breed, sex, weight, age and stage of the cataract were recorded. Dogs were categorized into groups depending on their breed. Effects of these variables on measurements were evaluated. Correlations of AL to LEL10 and LEL35 were assessed; linear regression formulas were calculated then validated. Results No significant effect of age and sex on measurements but significant effects of dogs’ group, weight and stage of the cataract were found. We found strong correlations between AL and LEL10 and between AL and LEL35. Regression formulas were LEL10 = 0.72 × AL − 1.09 and LEL35 = 0.49 × AL + 0.89. Means of the difference between measured and calculated LEL in control sample were 0.28 mm for LEL10 and −0.13 mm for LEL35. Conclusions Ocular measurements were higher in medium/large dogs than in small dogs and in intumescent and hypermature cataract than in mature. Regression formulas to predict LEL might be used with caution.