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Real-time refractive video data during cataract surgery provide surgical planning, guidance
A surgeon discusses his first experiences with a new intraoperative wavefront aberrometry prototype.
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At one time, IOL powers were calculated by subtracting the power of the refraction from the ideal 18 D average implant or simply putting a set lens power in everyone. Some of us likely started performing cataract surgery with only a manual keratometer and a contact ultrasound A-scan.
As optical biometers such as the IOLMaster (Carl Zeiss Meditec) and improved power calculation formulas such as Holladay and SRK/T have been developed, the predictive accuracy now possible is far removed from the days of 4 D post-surgical surprises. However, the opportunity still remains to further improve lens selection and placement, especially for the increasing number of post-refractive cataract patients.
Stephen G. Slade
We are now in the era of striving to refract the aphakic eye. WaveTec Vision advanced the idea of aphakic refractive measurements with the development of the first intraoperative wavefront aberrometer, ORA, which attaches directly to the surgical microscope and allows the surgeon to acquire readings intraoperatively, as well as confirm lens placement and residual astigmatism. Clarity Medical Systems has in turn developed Holos, a real-time intraoperative wavefront aberrometry for refractive cataract surgery.
Holos IntraOp employs a unique form of aberrometry that uses sequential scanning to acquire and stream a continuous refractive measurement throughout the patient surgery via a live video of the eye accompanied by an overlay of qualitative and quantitative refraction. The unit provides continuous refractive data throughout the phakic, aphakic and pseudophakic phases of surgery. In addition, during placement of a toric lens, the system provides continuous guidance to the surgeon to optimize refractive placement of the lens. If performing a limbal relaxing incision to manage astigmatic correction, Holos makes it possible to titrate the incision using real-time feedback. Among the most valuable features of Holos is the ability to capture data that can later be culled to determine the relationship between surgical maneuvers, intraoperative refraction and postoperative outcomes.
My experience testing a Holos prototype in the operating room showed it to be easily adapted to my surgical environment. The device attaches to a standard surgical microscope at most commonly used working distances. A monitor provides a continuous live image of the eye with associated refraction, with the data continuously available. Refractions are accurate throughout a 40 D range, according to Clarity.