Corneal Asphericity and Higher-Order Aberrations after FS-LASIK and Trans-PRK for Myopia

Abstract

Objective. To compare the corneal asphericity and higher-order aberrations (HOAs) of femtosecond laser-assisted in situ keratomileusis (FS-LASIK) with Smart Pulse Technology (SPT) assisted transepithelial photorefractive keratectomy (Trans-PRK) for myopia and myopic astigmatism correction. Methods. This prospective study analyzed 88 eyes of 44 patients treated with FS-LASIK and 64 eyes of 32 patients treated with Trans-PRK. All eyes had low to moderate myopia with or without astigmatism (spherical equivalent (SE) <−6.00 diopters). The uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), SE, asphericity (Q value) of the anterior corneal surface, index of surface variance (ISV), corneal higher-order aberrations (HOAs), vertical coma (Z3−1), horizontal coma (Z31), and spherical aberration (Z40) over a 6 mm diameter central corneal zone diameter were evaluated preoperatively and 1, 3, and 6 months postoperatively. Results. At 6 months, the UDVA and SE were −0.14 ± 0.06 and 0.33 ± 0.33D in FS-LASIK and −0.15 ± 0.06 and 0.35 ± 0.37D in Trans-PRK. There was no difference between the two groups in the postoperative UDVA and SE ( P > 0.05 ). After FS-LASIK and Trans-PRK, the Q values in the 6, 7, 8, and 9 mm zones and ISV of the anterior corneal surface significantly increased ( P < 0.001 ). At 1, 3, and 6 months after surgery, corneal HOA, Z3-1, Z31, and Z40 in both groups were significantly increased compared with those before surgery, with statistically significant differences ( P < 0.001 ). At 1, 3, and 6 months after surgery, the Z3−1 of the Trans-PRK group was significantly lower than that of the FS-LASIK group ( P < 0.001 ). ΔHOA and ΔZ40 were dramatically correlated with the ΔQ value for both FS-LASIK and Trans-PRK procedures. The ΔQ was significantly correlated with the preoperative SE, AD, and AD/CCT after both two procedures (all P < 0.001 ). Conclusions. Both FS-LASIK and Trans-PRK caused the anterior corneal surface to become flatter, and the morphology of the corneal surface was irregular. Corneal HOAs were significantly increased after the two procedures. Trans-PRK using SPT introduced less corneal vertical coma than FS-LASIK. Corneal asphericity changes contributed to the corneal aberrations changes following FS-LASIK and Trans-PRK.

Clinical outcomes of stromal lenticule rotation to correct mixed astigmatism

“…20 Studies report that increased anterior corneal surface HOAs after photorefractive keratectomy, LASIK, and laser-assisted subepithelial keratectomy are mainly from increased spherical and coma aberrations. [21][22][23] A notable finding in our study was unchanged spherical aberration. However, trefoil and coma increased much more than spherical aberration after surgery.…”

Effect of Sodium Fluorescein Strip Application on Cornea Parameters Commonly Used in Laser-assisted in-situ Keratomileusis

“…Corneal asphericity at the anterior corneal surface is negative and increases from the center to the periphery. [14] Esraa El-Mayah et al previously suggested that the spherical aberration at 6.0 mm is affected by the ablation pro le method, but the Q-value at 8.0 mm is a parameter that could predict ablation volume or ablation depth relatively independently of ablation pro le; [15] as such, the measurement of the Q-value in the 8 mm zone was investigated in our study. In LASIK, monovision is a method of presbyopic correction, in which one eye is corrected for distance vision and the other eye for near vision, and this procedure is based on Q factor modulation.…”

Refractive Management of Surgical-Induced Presbyopia in a Young Patient with Vision-Related Quality of Life Complaints: A Case Report

“…PRK was chosen as the corneal procedure given that the patient had occupational risk for trauma. Furthermore, some studies suggest that PRK induces fewer aberrations than laser in situ keratomileusis (LASIK), which is an important consideration in a patient who already has two IOLs [ 9 , 10 ].…”