Eyeworld

JULY 2023 | EYEWORLD | 41 C References 1. Alsetri H, et al. Diffractive optic intraocular lens exchange: indi- cations and outcomes. J Cataract Refract Surg. 2022;48:673–678. 2. Fram NR, et al. Comparison of intraoperative aberrometry, OCT-based IOL formula, Hai- gis-L, and Masket formulae for IOL power calculation after laser vision correction. Ophthalmolo- gy. 2015;122:1096–1101. 3. Abulafia A, et al. Accuracy of the Barrett True-K formula for intraocular lens power prediction after laser in situ keratomileusis or photorefractive keratectomy for myopia. J Cataract Refract Surg. 2016;42:363–369. 4. Haigis W. Intraocular lens calculation after refractive surgery for myopia: Haigis-L formula. J Cataract Refract Surg. 2008;34:1658–1663. 5. Lawless M, et al. Total keratometry in intraocular lens power calculations in eyes with previous laser refractive surgery. Clin Exp Ophthalmol. 2020;48:749–756. 6. Yeo TK, et al. Accuracy of intraocular lens formulas using total keratometry in eyes with previous myopic laser refractive surgery. Eye (Lond). 2021;35:1705– 1711. 7. Wang L, et al. Evaluation of total keratometry and its accu- racy for intraocular lens power calculation in eyes after corneal refractive surgery. J Cataract Refract Surg. 2019;45:1416–1421. 8. Lanza M, et al. Accuracy of formulas for intraocular lens power calculation after myopic refractive surgery. J Refract Surg. 2022;38:443–449. 9. Refractive prediction accuracy using intraoperative aberrome- try versus Barrett True-K formula in post-corneal refractive surgery eyes. Presentation at the 2021 American Academy of Ophthal- mology Meeting, New Orleans, Louisiana. For Dr. Hill, the most important part of IOL selection with patients who have had prior refractive surgery is their aberration profile. "Those patients with significantly elevated higher order aberrations, such as coma and spherical aberration, are generally not multifo- cal IOL candidates," Dr. Hill said. "This is rein- forced by the image simulation, which typically demonstrates a loss of contrast." IOL calculations Dr. Hill said the "go-to" IOL formula for those with prior refractive surgery is the Barrett True-K. If the patient is a toric candidate, and he said that this is uncommon, he'll use the Barrett True-K Toric with the measured posteri- or corneal power. "For those patients who abso- lutely have to have an exact refractive outcome, the LAL is used," he said. Dr. Fram said that many patients with prior refractive surgery expect to have similar refractive results after cataract surgery. How- ever, their modified anterior corneal curvature isn't accurate with traditional formulae that are based on assumptive keratometry principles. Dr. Fram cited research that has shown previous formulas developed for post-laser vision cor- rection eyes, relying on historical keratometry, were within ±0.50 D of target less than 60% of the time. These, she noted, were eliminated from the ASCRS calculator. When post-laser vision correction ablation data are available, the Masket Regression formula achieves 85% within ±0.5 D and 95% ±1 D of target. 2 Newer formulae that don't require histor- ical data and intraoperative tools have further improved outcomes for these patients, Dr. Fram said. "Abulafia et al. reviewed the Barret True-K formula outcomes and found the Barrett True-K was comparable to results of the ASCRS calcu- lator with a median absolute error of 0.33 D. 3 However, only 67.2% and 94.8% of eyes were within ±0.50 D and ±1.0 D from the target refraction, respectively," Dr. Fram said. "Haigis reviewed 187 eyes and found that using the Haigis-L formula, the percentages of correct outcome. If the patient was previously happy with this ablation pattern without cataracts, Dr. Fram said she'll often choose IOLs with zero spherical aberration. "The question often arises whether to choose an EDOF or diffractive multifocal/ trifocal technology in the post-corneal refrac- tive population," Dr. Fram continued. "There are many reports of excellent outcomes with this technology. In our experience, the abla- tion needs to be well centered with normal Placido imaging in order to have a satisfied patient. Some refer to the EDOF technology as 'more forgiving' than a multifocal or diffractive technology. However, if a surgeon is going to use this technology, they need to be prepared to remove the IOL because up to 19% of post- LASIK patients had to have an IOL exchange due to diffractive dysphotopsia, according to our research." 1 This is where Dr. Fram finds the Light Adjustable Lens (LAL, RxSight) beneficial. "The LAL has been a huge boost for our prac- tice in the post-LASIK/PRK patient population [because] the IOL targeting can be adjusted postoperatively and is less reliant on current IOL calculations," she said. "This has become my preferred technique due to the postoperative adjustability, and the silicone IOL lends itself to a lower dysphotopsia profile in these already aberrated corneas." While it's still necessary with the LAL for the patient to have a well-centered ablation, normal Placido imaging, and a pupil that can dilate to at least 6.5 mm, Dr. Fram said the tech- nology can achieve a customized mini-monovi- sion without the need to disassociate the eyes more than 1.5 D. "Patients need to understand this is still a monovision strategy and they will need glass- es for some tasks depending on the amount of anisometropia, such as driving at night and reading very small print. When we looked at the number of post-myopic LASIK ablation patients (n=35) achieving stable ±0.5 D at 1 year, it was 87%. Although this is a very small study group, the results are promising. Further, this has not been reported consistently in the literature in the post-laser vision correction population." continued on page 42

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