Significant Difference In Spherical Aberration Research Articles

Clinical Analysis of Central Islands after Small Incision Lenticule Extraction (SMILE)

ABSTRACT Purpose To evaluate the incidence of central islands after 6-month follow-up of Small Incision Lenticule Extraction (SMILE) and to assess their role in safety and accuracy. Methods Analysis of the preoperative and postoperative corneal tomography, best spectacle refraction and corrected distance visual acuity of 82 subjects that underwent SMILE. Incidence of central islands was assessed through total corneal spherical aberration (SA) over 4 mm of central diameter and the SA was compared between two groups with and without safety loss (CDVA difference ≥0.1 logMAR from preoperative). The cut-off value for detecting the risk of postoperative central island development was calculated. The influence in accuracy was calculated through magnitude of error of the spherical equivalent and astigmatism, both for spectacle refraction at corneal plane (SE-Rx and AST-Rx) and for total corneal refractive power at 3 mm (SE-TCRP3 and AST-TCRP3). Results Five from 82 eyes resulted in a loss of safety, obtaining significant differences in SA, both preoperatively (p = .01) and postoperatively (p = .007) after stratification by safety loss. A preoperatively cut-off value ≤0.012 μm of SA predicted the appearance of central islands with sensitivity of 100% and specificity of 75%. Despite postoperative SA being related to the preoperative spherical equivalent, for both SE-Rx and SE-TCRP3, this tendency disappeared after readjusting results according to a nomogram. Conclusions Central islands in SMILE, despite being a rare adverse event, can affect the safety of the procedure and are related to preoperative central steepness, not corrected by the spherical lenticule, which is clearly visible postoperatively.

Optical behavior of the eye implanted with extreme intraocular lens powers

To evaluate the induced ocular aberrations after cataract surgery with extreme low- powered and high-powered spherical monofocal intraocular lenses (IOLs) using a new pyramidal wavefront sensor aberrometer. Vissum Instituto Oftalmológico, Alicante, Spain. Prospective observational comparative study. This study included patients who had cataract surgery with implantation of a spherical monofocal IOL. The patients were divided into three groups according to the IOL power. Group 1: +20 diopters (D) to +23 D; Group 2: less than +10 D; and Group 3: +29 D or more. Assessment after 3months included: uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refraction, contrast sensitivity function test (Ginsburg), corneal aberrometry, and total ocular aberrometry with a pyramidal wavefront sensor aberrometer (Osiris) for 4.0mm, 4.5mm, and 5.0mm pupil diameters. The study comprised 88 eyes of 56 patients. There were no differences between all groups in terms of refractive error, corneal aberrometry, or total ocular higher-order aberrations at any analyzed pupil diameter. The ocular spherical aberration (SA) was not significantly different between groups with a 4.0mm pupil. The SA was significantly lower in Group 2 when compared with Group 1 and Group 3 for both 4.5mm(P=.01 and P=.001, respectively) and 5.0mm(P=.002 and P=.002, respectively). There was no significant difference in SA between Group 1 (+20 D to 23 D) and Group 3 (≥+29 D) at any analyzed pupil diameter. Higher SA did not correlate to lower contrast sensitivity. Despite the theoretical evidence, only a negligible amount of clinically insignificant aberrations were induced by high-powered positive IOLs. Low-powered IOLs did not induce significant levels of SAs.

Comparison of Higher-Order Aberrations and Visual Quality in Eyes Wearing Aspheric and Spherical Silicone Hydrogel Contact Lenses

Purpose: To investigate ocular higher-order aberrations (HOAs) and visual quality when wearing aspheric and spherical silicone hydrogel contact lenses. Methods: Fifty eyes of 25 myopic subjects (24.32±2.87 years; 13 females, 12 males) participated in this study. Each eye was fitted with two silicone hydrogel lenses of the following brands: Biofinity (aspheric design) and Acuvue Oasys (spherical design). Best-corrected visual acuity (VA) with high and low contrast and best-corrected contrast sensitivity (CS) at 3, 6, 12 and 18 cycles per degree (cpd) were measured under photopic and mesopic conditions. A wavefront analyzer was used to measure ocular HOAs for 4-mm and 6-mm pupils in each eye without and with the contact lenses. All measurements were conducted monocularly by having each subject to wear one lens design per one day during two days. Results: No statistically significant differences in high contrast or low contrast visual acuity (HCVA or LCVA) were found between the two lens designs under photopic and mesopic conditions. There were no significant differences in CS under photopic or mesopic conditions at other spatial frequencies, although CS under the mesopic conditions at 12 cpd was statistically significant difference between the two lens designs (p=0.012). For ocular HOAs, the level of all HOAs with 4-mm and 6-mm pupils was reduced by two lens designs compared to wearing no lens. Also, there was statistically significant difference in spherical aberration (SA) between the two lens designs within the brands with both pupil sizes (p=0.002, p=0.001, respectively); however, there were no significant differences in any other ocular HOAs between the two lens types with 4-mm or 6-mm pupils. Conclusion: Aspheric silicone hydrogel contact lenses are not clinically different in visual quality compared with spherical silicone hydrogel contact lenses.

굴절교정수술을 받은 근시안의 각막 비구면도와 광학적 특성 평가

목적: 엑시머 레이저 근시굴절교정수술을 받은 사람의 각막 비구면도, 시력, 고위수차를 정시안과 비교 평가하였다. 방법: 단안의 나안 시력이 1.0 이상인 근시 굴절교정수술을 받은 23명(나이: <TEX>$23.0{\pm}2.5$</TEX>세)과 20명(<TEX>$21.0{\pm}2.6$</TEX>세)의 정시안을 대상으로 밝은 조명(photopic)과 중등도(mesopic) 조명상태에서 대비도를 가지는 시력표(100% 및 10%)를 이용하여 시력검사를 하였고, wavefront 수차 분석기(KR-1W, Topcon, Japan)를 이용하여 각막의 비구면계수와 4mm와 6 mm의 동공크기에 따른 눈 전체의 고위수차와 각막의 고위수차를 측정하여 비교하였다. 결과: 굴절교정 수술안과 정시안에서 대비도에 따른 시력은 유의한 차이를 보이지 않았다. 안구 수차(ocular aberrations)에서 전체 고위수차, 4차수차, 구면수차는 동공크기 6 mm상태에서 굴절교정 수술안에서 높게 나타났고, 두 그룹 사이에 유의한 차이를 보였다(p=0.045, p<0.001, p<0.001). 각막의 구면 수차(corneal spherical aberrations)는 동공크기 4 mm와 6 mm상태에서 모두 굴절교정 수술 안에서 더 높게 측정되었고 유의한 차이를 보였다(p<0.01, p<0.001). 각막의 전체고위수차와 4차수차는 동공크기 6 mm 상태에서만 굴절교정 수술안에서 더 크게 나타났고 통계적으로 유의하였다(p<0.001, p<0.001). 정시안의 비구면계수와 구면수차는 동공크기 4 mm와 6 mm 상태에서 안구 수차(r=0.442, p=0.004, r=0.519, p<0.001) 와 각막수차(r=0.358, p=0.023, r=0.646, p<0.001) 모두에서 유의한 상관성을 나타내었으나, 굴절교정 수술안에서는 상관성이 없었다. 결론: 각막굴절교정 수술안의 경우 시력은 정상수준을 나타내고 있으나 동공크기가 커지면 수차가 증가하여 동공이 커지는 야간에는 시력의 질에 영향을 줄 수 있을 것으로 사료된다. Purpose: To compare corneal asphericity, visual acuity (VA), and ocular and corneal higher-order aberrations (HOAs) between myopic refractive surgery and emmetropia groups. Methods: Twenty three subjects (<TEX>$23.0{\pm}2.5$</TEX> years) who underwent myopic refractive surgery and twenty emmetropia (<TEX>$21.0{\pm}206$</TEX> years) were enrolled. The subjects'criteria were best unaided monocular VA of 20/20 or better in both two groups. High and low contrast log MAR visual acuities were measured under photopic and mesopic conditions. Corneal and ocular HOAs were measured using Wavefront Analyzer (KR-1W, Topcon) for 4 mm and 6 mm pupils. Corneal asphericity was taken by topography in KR-1W. Results: There was no significant difference in VA between two groups under either photopic or mesopic conditions. In ocular aberrations, there were significant differences in total HOAs, fourthorder and spherical aberration (SA) for a 6 mm between two groups (p=0.045, p<0.001, and p<0.001, respectively). In corneal aberrations, there was a significant difference in SA for 4 mm (p=0.001) and 6 mm (p<0.001) pupils between two groups and there were statistically significant differences in total HOAs (p<0.001) and fourth-order aberrations (p<0.001) between two groups for a 6 mm pupil. There was a significant correlation in emmetropia between Q-value and SA in ocular aberrations for 4 mm and 6 mm pupils (r=0.442, p=0.004, and r=0.519, p<0.001) and in corneal aberrations for 4 mm and 6 mm pupils (r=0.358, p=0.023, and r=0.646, p<0.001). No significant correlations were found between Q-value and SA in refractive surgery group. Conclusions: VA in myopic refractive surgery is better than or similar to emmetropia. Nevertheless, the more increasing pupil size is, the more increasing aberrations are. Thus, it could have an influence on the quality of vision at night.

A Prospective, Contralateral Eye Study Comparing Thin-Flap LASIK (Sub-Bowman Keratomileusis) with Photorefractive Keratectomy

To determine the differences in the visual results, pain response, biomechanical effect, quality of vision, and higher-order aberrations, among other parameters, in eyes undergoing either photorefractive keratectomy (PRK) or thin-flap LASIK/sub-Bowman keratomileusis (SBK; intended flap thickness of +/-100 microm and 8.5-mm diameter) at 1, 3, and 6 months after surgery. A contralateral eye pilot study. Fifty patients (100 eyes) were enrolled at 2 sites. The mean preoperative spherical refraction was -3.66 diopters (D) and the mean cylinder was -0.66 D for all eyes. Eyes in the PRK group underwent 8.5-mm ethanol-assisted PRK, whereas in eyes in the SBK group, an 8.5-mm, (intended) 100-microm flap was created with a 60-kHz IntraLase femtosecond laser (Advanced Medical Optics, Santa Ana, CA). All eyes underwent a customized laser ablation using an Alcon LADARVision 4000 CustomCornea excimer laser (Alcon Laboratories, Fort Worth, TX). Preoperative and postoperative tests included best spectacle-corrected visual acuity, uncorrected visual acuity (UCVA), corneal topography, wavefront aberrometry, retinal image quality, and contrast sensitivity. Patients completed subjective questionnaires at each visit. One- and 3-month UCVA results showed a statistically significant difference: SBK, 88% 20/20 or better vs. 48% 20/20 or better for PRK. At 6 months, UCVA was 94% 20/20 or better for PRK and 92% for SBK. At 1 and 3 months, the SBK group had lower higher-order aberrations (coma and spherical aberration; P<or=0.05); at 1, 3, and 6 months, there was no statistically significant difference in spherical aberration and vertical and horizontal coma between the 2 groups. At the 1-month follow-up, the thin-flap/SBK group demonstrated clinically and statistically significant better visual acuity than the PRK group. By 3 months, the vision in the 2 groups had begun to equalize, although the SBK eyes continued to have better vision. At 6 months, there were no statistical differences between the 2 groups. Proprietary or commercial disclosure may be found after the references.