J Korean Ophthalmol Soc.  2021 Feb;62(2):201-206. 10.3341/jkos.2021.62.2.201.

Intraocular Lens Power Calculation Using Shammas-PL Formula after Laser In-situ Keratomileusis

• Park SY
• Kwag JY
• Choi JS
• Pak KH
• Chung SK

• KMID: 2512939
• DOI: http://doi.org/10.3341/jkos.2021.62.2.201

Abstract

Purpose
To calculate the intraocular lens (IOL) power using the Shammas-PL formula after laser in-situ keratomileusis (LASIK).
Methods
Forty-one eyes of 29 patients that had undergone cataract surgery from September 2018 to September 2019 after LASIK were enrolled in this study. A preoperative AL-Scan^® (Nidek Co., Gamagori, Japan) was used to measure the axial length, anterior chamber depth, and corneal curvature. An IOL power calculation was performed using the Shammas-PL (post LASIK) formula. Mean absolute error (MAE) and mean arithmetic error (MARE) were calculated using preoperative manifest refraction and postoperative manifest refraction.
Results
Of the 41 eyes, 15 eyes (36.6%) were relatively hyperopic-shifted after surgery compared to the predicted refractive error before surgery, 25 eyes (61%) showed a relative myopic shift, and one eye (2.4%) showed no change with respect to the previous refractive predicted error. Refractive errors before cataract surgery were not related to myopic, emmetropic, or hyperopic shifting after surgery (p > 0.05).
Conclusions
When cataract surgery using the Shammas-PL formula was performed after LASIK, myopic shifting was more common than hyperopic shifting. The MAE was greater in myopic-shifted cases than that of hyperopic-shifted cases. Thus, it is better to determine IOL power toward the hyperopic side than the target refractive prediction.

Keyword

Cataract, Intraocular lens power calculation, Laser in-situ keratomileusis, Shammas-PL