PURPOSE: To compare White To White (WTW) measurements obtained using manual calipers and optical biometer MATERIALS AND METHODS: Preoperative horizontal WTW measurements in 10 eyes of 05 patients who opted for phakic IOL were recorded using both manual calipers and optical biometer (NIDEK AL SCAN). Phakic IOL were designed based on WTW readings taken by manual calipers. Postoperatively, AS OCT has been performed to measure the vault of the Phakic IOL. Independent T test was used to analyse the results. RESULTS: Mean WTW measurement using calipers and optical biometer was 11.70+0.15 and 12.13+0.25mm respectively. P value was significant (0.00) CONCLUSION: WTW measurements recorded by using manual calipers were reliable. Optical biometer overestimates the WTW measurements compared to calipers