Retrospective analysis of changes in the anterior corneal surface after Q value guided LASIK and LASEK in high myopic astigmatism for 3 years

Abstract

BackgroundTo compare the corneal high-order aberrations (HOAs), asphericity and regularity after Q-value guided laser in situ keratomileusis (LASIK) and laser epithelial keratomileusis (LASEK) in high myopic astigmatism.MethodsIn this retrospectively comparative study, we measured the corneal HOAs, asphericity indices (Q values) and corneal regularity indices preoperatively and 36 months postoperatively in 70 eyes (35 patients) with Q-value guided surgeries. All the patients with high myopic astigmatism were divided into two groups which included 34 eyes underwent LASIK and 36 eyes underwent LASEK procedures. The main impact factors of the high-order aberrations were also analyzed.ResultsIn the two groups, the efficacy index was more than 1.00 and safety index approached 1.00 at year 3 postoperatively. Statistically significant (P < 0.05) increased in Q values and main corneal HOAs (spherical aberrations and coma) following Q-value guided LASIK and LASEK procedures. Spherical aberrations increased more in the LASEK group and there was statistically difference compared to the LASIK group (P < 0.05). LASEK had better effects in correcting corneal astigmatism (P < 0.05). All the corneal regularity indices after surgeries increased and there was no significant difference (P = 0.707, P = 0.8 and P = 0.224, respectively) between the two groups. The main impact factors of spherical aberration included the optic zone size, changes of Q value, surgical procedure and the corrected refraction.ConclusionsIn high myopic astigmatism, Q-value guided ablation showed good safety, efficacy and predictability. Q value, regularity indices, spherical aberration and coma increased in both LASIK and LASEK procedures. Astigmatism could be corrected more effectively by LASEK but greater spherical aberration could be created. The difference might be related to the different healing mechanisms. Optic zone size and the corrected refraction might be the main influence factors on the anterior corneal high order aberrations.

Retrospective Analysis Comparing the Preoperative and Postoperative “Q” Values for 2 Different Lasers in Refractive Surgery

“…Although patients post-photorefractive keratectomy (PRK) could potentially require little or no refractive correction to achieve best-corrected visual acuity (BCVA), halos and glare can impede the postsurgical quality of vision. 9 Therefore, it is important to minimize DQ when possible because it has been shown that the loss of prolate asphericity may be the predominant factor in any functional decrease in vision after refractive surgery. 10 Clearly, greater refractive correction requires greater corneal reshaping and therefore necessitates a greater net DQ.…”

Postoperative Corneal Asphericity in Low, Moderate, and High Myopic Eyes After Transepithelial PRK Using a New Pulse Allocation

“…Corneal asphericity, spherical aberrations, and coma have been shown to increase in long-term follow-up studies after LASIK and LASEK procedures, mainly due to the healing mechanism of the cornea. [7][8][9] Myopic and hyperopic corrections using wavefront-guided LASIK have been shown to induce changes in the Q-value and spherical aberrations in opposite directions (ie, positive and negative, respectively). These changes depend on the magnitude of the refractive correction.…”

Characteristics of corneal Q value and its related factors in cataract patients before operation

“…The Q value, being the crucial parameter of the mathematical cornea model, is re ective of the shape of the cornea and its optical properties [4,5], which includes the aberration distribution, the spherical aberration, the refractive power, and others. Today, the corneal Q value along with its distribution properties have garnered the focus of attention of the relevant studies, besides the manner in which the optical properties are impacted in the eye [6][7][8][9].…”