Swept source oct use leads to improved results

Professor Graham Barrett Professor Graham Barrett, Lions Eye Institute, Perth, Australia, presented the results of his research into the use of swept source OCT (ssOCT) for improved keratometry. “Whereas in the past, classical keratometry provided a single data point of the corneal radius, ssOCT now allows us to directly measure the radius of the posterior cornea, resulting in ‘true’ keratometry,” said Prof Barrett. True keratometry, or KTK, can then be used in the Barrett TK Universal II formula for IOL power calculation, which might deliver better refractive outcomes, both spherical and astigmatic, after cataract surgery. The method was evaluated by Professor Ekkehard Fabian, Augencentrum Rosenheim, Germany, who included 108 cases in the analysis. For the study, he implanted the aberration-neutral, aspheric CT Asphina 409M from Zeiss. Spherical equivalent refractive outcomes using the Barrett TK Universal II formula were as follows: 85.2% within 0.5D of target refraction, 94.4% within 0.75D and 97.2% within 1.00D. These outcomes were better than the Haigis, Holladay, SRK/T and the Hoffer Q, with which they were compared, with lower standard deviation. Prof Barrett said: “We seem to be reaching the ceiling of obtainable spherical power prediction.” Whereas Moore’s law can theoretically continue doubling computer processor speeds, there is an asymptotic curve for IOL power calculations that will continue to get us closer and closer to 100%.