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Published on: September 20, 2024
Intraocular lens calculation adjustment after laser refractive surgery using Scheimpflug imaging
Alexander K Schuster1, David J Schanzlin1, Karin E Thomas1
1From Medical Physics (Schuster), Universitätsmedizin Mannheim, University of Heidelberg, Mannheim, and the Department of Ophthalmology (Schuster), Mainz University Medical Center, Mainz, Germany; private practice (Schanzlin), Gordon-Weiss-Schanzlin Vision Institute, and the Shiley Eye Center (Heichel, Purcell), University of California San Diego, La Jolla, California, and the Walter Reed National Military Medical Center (Thomas, Barker), Bethesda, Maryland, USA.
Purpose:
To test a new method of intraocular lens (IOL) calculation after corneal refractive surgery using Scheimpflug imaging (Pentacam HR) and partial coherence interferometry (PCI) (IOLMaster) that does not require historical data; that is, the Schuster/Schanzlin-Thomas-Purcell (SToP) IOL calculator.
Setting:
Shiley Eye Center, San Diego, California, and Walter Reed National Military Medical Center, Bethesda, Maryland, USA.
Design:
Retrospective data analysis and validation study.
Methods:
Data were retrospectively collected from patient charts including data from Scheimpflug imaging and refractive history. Target refraction was calculated using PCI and the Holladay 1 and SRK/T formulas. Regression analysis was performed to explain the deviation of the target refraction, taking into account the following influencing factors: ratio of posterior-to-anterior corneal radius, axial length (AL), and anterior corneal radius.
Results:
The regression analysis study included 61 eyes (39 patients) that had laser in situ keratomileusis (57 eyes) or photorefractive keratectomy (4 eyes) and subsequent cataract. Two factors were found that explained the deviation of the target refraction using the Holladay 1 formula; that is, the ratio of the corneal radii and the AL and the ratio of corneal radii for the SRK/T formula. A new IOL adjustment calculator was derived and validated at a second center using 14 eyes (10 patients).
Conclusions:
The error in IOL calculation for normal eyes after laser refractive treatment was related to the ratio of posterior-to-anterior corneal radius. A formula requiring Scheimpflug data and suggested IOL power only yielded an improved postoperative result for patients with previous corneal laser refractive surgery having cataract surgery.
Financial Disclosure:
No author has a financial or proprietary interest in any material or method mentioned.
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