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Ray-tracing with anterior segment OCT yields accurate IOL power calculations
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Ray-tracing IOL power calculations using anterior segment optical coherence tomography in normal eyes with cataract were comparable to those derived from a conventional formula, according to a study.
The prospective case series included 102 eyes of 70 consecutive patients who underwent cataract surgery and attained corrected distance visual acuity of at least 0.15 logMAR at 1 month postop.
Placido topography and anterior segment OCT measurements were taken preoperatively. Three methods were used to obtain the predicted postop refractions: the SRK/T formula with autokeratometry, ray-tracing calculation with Placido topography data, and ray-tracing calculations with anterior segment OCT measurement of both corneal surfaces. The effects of corneal eccentricity and posterior corneal curvature were evaluated at 1 month postop.
No significant difference in refractive errors was observed at 1 month. Refractive error with the SRK/T formula demonstrated a significant correlation with corneal eccentricity (P = .0017), but the ray-tracing calculations were not affected.
A weak correlation with posterior corneal curvature was observed in the ray-tracing calculations performed with Placido topography in (P < .0002).
“In normal eyes with cataract, the use of ray-tracing IOL power calculations with AS-OCT measurements was compatible with the results using the SRK/T formula,” the study authors said. “Use of AS-OCT measurements in ray-tracing calculations minimized the effect of corneal eccentricity and posterior corneal curvature. This indicates that accuracy can be retained in cases with abnormal corneas.”
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