ABSTRACT
Purpose: To derive a formula for accurate axial length (AL) assessment using routine ultrasound in silicone oil?filled eyes, where optical biometry is unavailable or not possible. Methods: This was a prospective, consecutive, nonrandomized study of 50 eyes of 50 patients conducted in a tertiary care hospital in North India. AL measurements were taken using both manual A?scan and IOL master, both in silicone oil?filled status and 3 weeks after silicone oil removal. A correction factor of 0.7 was used for AL adjustment in oil?filled eyes. The corrected AL (cAL) was compared with IOL master values in oil?filled eyes. Agreement analysis was carried out using Bland Altman plot. Linear regression analysis was done using uncorrected manual AL to find a new equation. Data was analyzed using Stata 14. A P value <0.05 was taken as significant. Results: The study included 40 males and 10 females, with an age range of 6–83 years (mean 41.9 years). The mean AL of the oil?filled eye as measured by manual A?scan was 31.76 mm ± 3.09 and by IOL master was 24.7 mm ± 1.74. Linear regression analysis was performed in randomly selected 35 eyes of the observed data to obtain a new equation: predicted AL (PAL) = 14 + 0.3 × manual AL. The mean difference between PAL and optically measured AL with silicone oil in situ was 0.98 ± 1.67. Conclusion: We propose a new formula for better prediction of the correct AL in silicone oil?filled eyes using ultrasound?based AL measurement.