Prediction of postoperative IOL position from preoperative Swept Source OCT data
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First Author: P.Hoffmann GERMANY
Co Author(s): L. Dröghoff
Postoperative axial IOL position is the single most important factor for refractive precision in cataract surgery. The true IOL position should not be confused with “effective lens position” which is a “black box” containing a lot of assumptions and fudge factors. When raytracing is used to calculate IOL power, prediction of IOL position is crucial. We examined the role of Swept Source OCT imaging for this purpose.
Private eye clinic in Germany. Ongoing interventional cohort study.
We measured 255_eyes of consecutive cataract_patients with the Tomey CASIA2 OCT. Measurements were taken one week prior to and 4 weeks after phacoemulsification. Two different lens platforms were used: 1. Hoya Vivinex, 2. J&J Tecnis 1piece family. The position of the crystalline lens equator was calculated from the anterior and posterior lens curvature. IOL position was predicted using different regression equations (Preußner, Olsen, Hoffmann). The Olsen approach was modified as the average “C constant” was derived from aggregate OCT data and then applied to individual cases (“OCT-A”). The individual crystalline lens equator position was referred to as “OCT-B”.
For the published regressions, the standard deviation of predicted minus achieved postoperative anterior chamber depth (“Prediction error”, PE) was ≈ 0.20 mm for all approaches. The Preußner approach yielded a little bit of systematic error (≈ 0.1 mm too deep). When approaches “OCT A” and “OCT B” were combined, standard deviation of PE was improved to ≈ 0.14 mm (30% improvement) with no outliers. The results of J&J and Hoya lenses slightly differed systematically due to haptic design (cap C versus planar).
Preoperative Swept Source OCT measurements have the potential to improve on axial IOL position prediction. If a 30% gain in IOL position prediction can be utilized for raytracing IOL power calculation, a 10% overall gain in refractive precision is to be expected from error propagation calculations.