Corneal higher-order aberrations of the anterior surface, posterior surface, and total cornea after small incision lenticule extraction (SMILE): high myopia versus mild to moderate myopia

Abstract

BackgroundTo investigate corneal higher-order aberrations (HOAs) of the anterior surface, posterior surface, and total cornea after small incision lenticule extraction (SMILE) in high myopic and mild to moderate myopic patients.MethodsThis retrospective study included 197 eyes (101 patients) undergoing SMILE surgery. According to the preoperative spherical equivalent (SE), treated eyes were divided into two groups: a high myopic group (more than − 6.0 D, Group H) and a mild to moderate myopic group (less than − 6.0 D, Group M). Corneal HOAs of the anterior surface, posterior surface, and total cornea were measured using a Scheimpflug camera preoperatively and 3 months postoperatively. Pearson’s correlation analysis was conducted to determine relationships between corneal aberrations and the SE.ResultsThere were no significant differences in third-order to eight-order aberrations (RMS HOAs) of the anterior surface, posterior surface, and total corneal between the two groups before SMILE surgery. However, after SMILE, anterior and total corneal HOAs, especially vertical coma and spherical aberrations, significantly increased in both groups (p < 0.0167), whereas posterior corneal HOAs remained relatively stable (p > 0.0167). The induction of HOAs was significantly greater in Group H than Group M postoperatively (p < 0.0167). Changes in anterior surface and total corneal HOAs, especially vertical coma and spherical aberrations, were related to the SE (p < 0.05).ConclusionsAnterior and total corneal HOAs, particularly vertical coma and spherical aberrations, significantly increased after SMILE in both groups, whereas posterior corneal HOAs remained stable. Aberration changes were related to SE.Trial registrationRetrospectively registered. ChiCTR-ORC-17011040. Registered 1 April 2017. Name of registry: The observation of clinical results after corneal refractive surgery. Data of enrolment of the first participant to the trial: 15 December 2016.

Comparison of efficacy and visual quality after CWFG-FS-LASIK, AF-FS-LASIK and SMILE for correcting myopia with asymmetry mid-to-high astigmatism

“…Astigmatism is a type of refractive error in which the eye does not focus light evenly on the retina and is unable to form a clear image. Corneal astigmatism can be divided into a round shape, an oval shape, an asymmetric bow-tie shape, and an irregular shape according to the corneal shape; among these shapes, the most common is an asymmetrical bow-tie shape, accounting for approximately 50.9% of cases [3] . Traditional corneal refractive surgery has a better effect for correcting low-order aberrations (myopia, astigmatism), but additional HOAs often develop after surgery, or the original HOAs increase, which are considered a cause of decline in postoperative visual quality [3,5] .…”

“…Corneal astigmatism can be divided into a round shape, an oval shape, an asymmetric bow-tie shape, and an irregular shape according to the corneal shape; among these shapes, the most common is an asymmetrical bow-tie shape, accounting for approximately 50.9% of cases [3] . Traditional corneal refractive surgery has a better effect for correcting low-order aberrations (myopia, astigmatism), but additional HOAs often develop after surgery, or the original HOAs increase, which are considered a cause of decline in postoperative visual quality [3,5] . Postoperative HOAs are mainly derived from the following causes: corneal flap production and its ablation depth, namely, the deeper the ablation, the more HOAs that are introduced; cooperation from the patient and eye position during surgery; and corneal wound healing, corneal morphology and biomechanical changes after surgery.…”

“…Aberration-Free treatment is one of these new algorithms which provided by Amaris laser platforms. In that case, aberration-free LASIK (AF-FS-LASIK) treatment could be considered as a possible method to correct both lower order aberrations and corneal asymmetry in the same time [3] . However, the asymmetric of corneal which often been noticed in patients with moderate to high astigmatism can not be treated by abovementioned 2 types of procedures which been considered to be related to corneal coma that might cause vision quality problems like glare.…”

Risk Factors and Incidence of Suction Loss during Small Incision Lenticule Extraction (SMILE) in 8487 eyes

“…Small incision lenticule extraction (SMILE) is a apless, minimally invasive refractive surgery that is currently gaining acceptance and popularity worldwide as it has potentially fewer complications than laser-assisted in situ keratomileusis (LASIK) and femtosecond laser-assisted LASIK (FS-LASIK). The e cacy, safety, predictability, and stability of SMILE have been supported by many clinical studies [1][2][3]. However, intraoperative and postoperative complications can still be observed [4][5][6][7][8].…”

“…A VisuMax Femtosecond Laser System (Carl Zeiss Meditec AG, Jena, Germany) was used for surgical refractive correction in all patients, with a repetition rate of 500 kHz and a pulse energy of 155 nJ. The surgical procedure was detailed in our previous reports [1,2]. In brief, a small patient interface cone (size S) was used in all patients, and prior to suction initiation, the patients were instructed to xate on the green target light.…”