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Refractive outcomes of intraocular lens power calculation using different corneal power measurements with a new optical biometer.
PURPOSE: To evaluate the results of intraocular lens (IOL) power calculation using different corneal power measurements provided by an optical biometer combined with a dual Scheimpflug analyzer and a Placido disk topographer (Galilei G6).
SETTING: G.B. Bietti Foundation, Rome, Italy, and Keio University Hospital, Tokyo, Japan.
DESIGN: Evaluation of diagnostic technology.
METHODS: Consecutive patients having cataract surgery were enrolled. The IOL power was calculated with the Barrett Universal II, Haigis, Hoffer Q, Holladay 1, and SRK/T formulas. Different options were used to calculate the corneal power: simulated keratometry (K) based on anterior corneal surface measurements only and total corneal power (TCP) based on ray tracing through both corneal surfaces. Three TCP measurements (TCP1, TCP2, and TCP-IOL) were evaluated.
RESULTS: The study analyzed 118 eyes. The mean values of simulated K (43.74 diopters [D] ± 1.40 [SD]), TCP1 (43.13 ± 1.35 D), TCP2 (41.87 ± 1.30 D), and TCP-IOL (42.62 ± 1.35 D) were significantly different (P < .0001). The best results were obtained using simulated K: the median absolute error ranged between 0.22 D and 0.29 D and the percentage of eyes with a prediction error of ±0.50 D or less, between 76.2% and 84.7%, depending on the formula. After constant optimization, the results using any TCP value and simulated K were similar with no statistically significant differences.
CONCLUSIONS: Biometric measurements provided by the Scheimpflug-Placido optical biometer can be used to accurately calculate the IOL power. Simulated K and TCP led to similar outcomes after constant optimization.
SETTING: G.B. Bietti Foundation, Rome, Italy, and Keio University Hospital, Tokyo, Japan.
DESIGN: Evaluation of diagnostic technology.
METHODS: Consecutive patients having cataract surgery were enrolled. The IOL power was calculated with the Barrett Universal II, Haigis, Hoffer Q, Holladay 1, and SRK/T formulas. Different options were used to calculate the corneal power: simulated keratometry (K) based on anterior corneal surface measurements only and total corneal power (TCP) based on ray tracing through both corneal surfaces. Three TCP measurements (TCP1, TCP2, and TCP-IOL) were evaluated.
RESULTS: The study analyzed 118 eyes. The mean values of simulated K (43.74 diopters [D] ± 1.40 [SD]), TCP1 (43.13 ± 1.35 D), TCP2 (41.87 ± 1.30 D), and TCP-IOL (42.62 ± 1.35 D) were significantly different (P < .0001). The best results were obtained using simulated K: the median absolute error ranged between 0.22 D and 0.29 D and the percentage of eyes with a prediction error of ±0.50 D or less, between 76.2% and 84.7%, depending on the formula. After constant optimization, the results using any TCP value and simulated K were similar with no statistically significant differences.
CONCLUSIONS: Biometric measurements provided by the Scheimpflug-Placido optical biometer can be used to accurately calculate the IOL power. Simulated K and TCP led to similar outcomes after constant optimization.
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