A proprietary toric IOL (AcrySof Toric, Alcon Laboratories) was found to be rotationally stable and a reliable option for the correction of astigmatism in a prospective study of 50 patients. The results were arrived at by using an innovative digital imaging technique coupled with new software that uses a grid to determine rotational stability of IOLs to a sensitivity of 0.1Â°. The implications of the new digital imaging technology and its associated software extend well beyond the findings in these 50 patients.
This technique recently was used to demonstrate that the single-piece design and bio-adhesive acrylic material of a toric IOL (AcrySof Toric, Alcon Laboratories) is rotationally stable and is a reliable option for the correction of astigmatism.
They found that the median rotation of the toric IOL from baseline to 6 months was 1.5° ± 0.65° with a range of 0.3° to 3.0°.
Although this study demonstrated the rotational stability of the toric IOL, the implications of the new digital imaging technology and its associated software extend well beyond the findings in these 50 patients, they said.
"This technology allowed precise measurement of IOL rotation," Dr. Vasavada said. "It may also help us determine the factors that affect IOL rotation and allow for independent evaluation of many different types of IOLs."
Retro-illumination images then were captured on the first postoperative day and at 1 week , 1 month, 3 months, and 6 months using a Nikon digital zoom camera mounted on a Nikon slit lamp. A chin rest and fixed target ahead ensured repeatable head and ocular alignment, and the camera's settings were standardized for all images.
The geometric center of the eye was then determined using the new software in all the digital retro-illumination images. This determination was made by calculating the mid-point of the line joining the innermost toric axis marks. The geometric center of the eye was used as the marker on the IOL plane and helped to align the images accurately with the grid (Figure 1).