Validating the use of U-tool as a novel method for measuring the corneal diameter in infants screened for congenital glaucoma

PURPOSE: The Castroviejo caliper is routinely used for measuring the corneal diameter in patients with primary congenital glaucoma, but needs an examination under anesthesia (EUA) or sedation. A simple U-shaped tool was devised to aid in the estimation of the corneal diameters of patients in settings where an ophthalmic caliper is not available or EUA is not feasible. METHODS: Infants presenting to the congenital glaucoma clinic posted for EUA were recruited. The demographic details of the patients such as age, sex, and diagnosis were noted. A simple U-shaped tool was devised using three Schirmer strips or a printable ruler. Before the patient underwent a EUA, the corneal diameters were measured using the U-tool. During EUA, corneal diameters were measured using the Castroviejo caliper. RESULTS: The mean age of infants was 6.7 ± 3.39 months (R = 1–12). The mean corneal diameter measured using the U-tool was 13.29 ± 1.33 mm and with Castroviejo caliper was 13.18 ± 1.39 mm. The difference between the corneal diameters measured using the two techniques was −0.114 mm with the Bland–Altman plot 95% Limits of agreement (LoA) from −0.965 to 0.737 mm. Corneal diameters measured with both instruments had a good correlation (Pearson’s correlation coefficient = 0.95, P < 0.001). CONCLUSION: U-tool can be used for screening congenital glaucoma by first-contact physicians or optometrists. It can also be used by ophthalmologists when EUA is delayed.