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Geunyoung Yoon, Hyi Jin Kim, Choun-Ki Joo; Impact of corneal spherical aberration on errors in IOL power calculation in cataract surgery after myopic refractive surgery. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4021.
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It has long been known that traditional laser refractive surgery induces spherical aberration (SA) which affects subjective refraction. The goal of this study is to evaluate the correlation between postoperative errors in IOL power estimation (referred to IOL power error) and preoperative corneal SA after cataract surgery in myopic refractive surgery patients.
This retrospective study was performed in 20 eyes of 16 patients who underwent cataract surgery after myopic refractive surgery. The IOL power error was defined as a difference between target diopter and postoperative spherical equivalent. The negative sign of the IOL power error indicates a myopic shift in postoperative refraction and vice versa. The patients were divided into two groups based on IOL power errors, group 1 (8 eyes) with magnitude of IOL power errors ≤ 0.5D, and group 2 (12 eyes) > 0.5D. Pentacam Scheimpflug imaging system (Oculus Inc, Germany) was used to measure anterior chamber depth (ACD), corneal keratometry and thickness, and SA before and 2 months after cataract surgery. The IOL power was calculated using SRK/T and Hagis-L. Statistical analysis was performed and P value <0.05 was considered statistically significant.
The preoperative anterior corneal K value in group 2 was significantly lower than group 1. Mean values of SA in group 1 and 2 were different, 0.57±0.76 µm and 1.17±0.88 µm respectively although a statistical significance was not found due to a small sample size. Preoperative corneal SA and IOL power errors showed strong positive correlation in the group 2 (R2=0.405). Eyes with relatively large magnitude of preoperative positive corneal SA had a considerable hyperopic shift in postoperative spherical equivalent, suggesting that IOL power prediction from the formula is underestimated i.e. IOL power needs to be increased to improve refractive outcomes after cataract surgery.
This study found that corneal SA had the considerable impact on optimal IOL power prediction especially in laser refractive surgery patients. Therefore, a next generation IOL power calculation formula needs to take corneal SA into consideration.
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