Humphrey and Tomey Biometry for Cataract Surgery: Is there a difference in visual outcome?

Barbara Haynes Grad Dip (Hlth Rsch Mth) DOBA
Suzanna Talevski BSc (Orth)(Hon) DOBA
Daniel J McCarty PhD

This retrospective study compares the refractive outcomes of cataract surgery when two diferent biometric techniques are used to calculate axial length. One, the slit lamp mounted Humphrey A-Scan and the other the hand held Tomey A-Scan. The medical histories of 344 patients who underwent cataract surgery during 1998-1999 at the Royal Victorian Eye & Ear Hospital were studied. In 179 cases the A-Scan measurement was done using the Tomey, while in 165 cases the Humphrey was used. Results show the refractive outcomes were within +/-1.00D of the expected refractive outcome in 87% of cases with the Tomey and 84% with the Humphrey (p=0.36), indicating no difference between these groups. Mean error, as defined as expected refraction minus achieved refraction, was less with the Humphrey (-0.08D) than with the Tomey (0.11D), (T=2.4, p=0.017). Despite this small statistically significant difference in mean error, a difference of 0.19D is not clinically significant. Refractive outcomes were similar between the groups showing both instruments give similar results.