Development of a New Method for Calculating Intraocular Lens Power after Myopic Laser In Situ Keratomileusis by Combining the Anterior-Posterior Ratio of the Corneal Radius of the Curvature with the Double-K Method

Intraocular Lens Power Calculation in Eyes After Myopic Laser Refractive Surgery and Radial Keratotomy: Bayesian Network Meta-analysis

PURPOSE

To compare the accuracy of formulas for calculating intraocular lens power in eyes after myopic laser refractive surgery or radial keratotomy.

DESIGN

Bayesian network meta-analysis.

METHODS

PubMed, Embase, the Cochrane Data Base of Systematic Reviews, and the Cochrane Central Register of Controlled Trials databases were searched for retrospective and prospective clinical studies published from January 1, 2012, to August 24, 2022. The outcome measurement was the percentage of eyes with a predicted error within the target refractive range (±0.50 diopter [D] or ±1.00 D).

RESULTS

Our meta-analysis includes 24 studies of 1172 eyes after myopic refractive surgery that use 12 formulas for intraocular lens power calculation. (1) A network meta-analysis showed that Barrett true-K no history, the optical coherence tomography (OCT) formula, and the Masket formula had a significantly higher percent of eyes within ±0.50 D of the goal than the Haigis-L formula, whereas the Wang-Koch-Maloney formula showed the poor predictability. Using an error criterion of within ±1.00 D, the same 3 formulas performed slightly better than the Haigis-L formula. Based on performance using both prediction error criteria, the Barrett true-K no history formula, OCT formula, and Masket formula showed the highest probability of ranking as the top 3 among the 12 methods. (2) A direct meta-analysis with a subset of 4 studies and 5 formulas indicated that formulas did not differ in percent success for either the ±0.5 D or ±1.0 D error range in eyes that had undergone radial keratotomy.

CONCLUSIONS

The OCT, Masket, and Barrett true-K no history formulas are more accurate for eyes with previous myopic laser refractive surgery, whereas no significant difference was found among the formulas for eyes that had undergone radial keratotomy.

An update on intraocular lens power calculations in eyes with previous laser refractive surgery

PURPOSE OF REVIEW

There is an ever-growing body of research regarding intraocular lens (IOL) power calculations following photorefractive keratectomy (PRK), laser-assisted in-situ keratomileusis (LASIK), and small-incision lenticule extraction (SMILE). This review intends to summarize recent data and offer updated recommendations.

RECENT FINDINGS

Postmyopic LASIK/PRK eyes have the best refractive outcomes when multiple methods are averaged, or when Barrett True-K is used. Posthyperopic LASIK/PRK eyes also seem to do best when Barrett True-K is used, but with more variable results. With both aforementioned methods, using measured total corneal power incrementally improves results. For post-SMILE eyes, the first nontheoretical data favors raytracing.

SUMMARY

Refractive outcomes after cataract surgery in eyes with prior laser refractive surgery are less accurate and more variable compared to virgin eyes. Surgeons may simplify their approach to IOL power calculations in postmyopic and posthyperopic LASIK/PRK by using Barrett True-K, and employing measured total corneal power when available. For post-SMILE eyes, ray tracing seems to work well, but lack of accessibility may hamper its adoption.