Effect of Computer Tasks in Straight Gaze on Corneal Topographic Indices.

Purpose: To investigate the effect of the near visual task of movie-watching in the straight gaze position on corneal topographic parameters. Methods: Thirty myopic young adults with an average age of 25.10 ± 4.13 years were recruited for the study. The designed near visual task consisted of watching a movie in the straight gaze position at a distance of 40 cm for 30 minutes. Corneal topography was performed using Oculus Keratograph 4 (OCULUS, Wetzlar, Germany) before and immediately after watching the movie, as well as at 10, 20, and 30 minutes intervals after completing this near visual task. Zernike coefficients, asphericity indices, refractive parameters, and diagnostic indices of keratoconus were recorded for statistical analysis. Results: Movie-watching at a close distance solely using the straight gaze position had no effect on Zernike coefficients (P > 0.130). Also, watching the movie had no effect on other corneal topography parameters including irregularities (P = 0.208), spherical eccentricity (P = 0.270), maximum decentration (P = 0.553), axis of maximum decentration (P = 0.186), peripheral astigmatism (P = 0.179), and average asphericity of the quadrants at 10 to 30º (P > 0.163). Conclusion: The results of the present study showed that watching movies in the straight gaze position had no effect on corneal topographic parameters and did not cause errors in corneal topographic measurements.

The comparison of corneal higher-order aberration and surgically induced astigmatism between the clear corneal incision and the limbus tunnel incision of posterior chamber implantable collamer lens implantation.

BACKGROUND: This study aimed to compare the corneal high-order aberrations and surgically induced astigmatism between the clear corneal incision and limbus tunnel incision for posterior chamber implantable collamer lens (ICL/TICL) implantation. METHODS: A total of 127 eyes from 73 myopic patients underwent ICL V4c implantation, with 70 eyes receiving clear corneal incisions and 57 eyes receiving limbus tunnel incisions. The anterior and back corneal surfaces were measured and the Root Mean Square of all activated aberrations (TRMS) was calculated, including higher-order aberration (HOA RMS), spherical aberration Z40, coma coefficients (Coma RMS) Z3-1 Z31, and surgically induced astigmatism (SIA). The measurements were taken preoperatively and postoperatively at 1 day, 1 week, and 1, 3, and 6 months. In this study, the corneal higher-order aberration was estimated as the Zernike coefficient calculated up to 5th order. The measurements were taken at a maximum diameter of 6.5 mm using Pentacam. RESULTS: One week after the operation, the corneal back Z31 of the clear corneal incision group was 0.06 ± 0.06, while the limbus tunnel incision group showed a measurement of 0.05 ± 0.06 (p = 0.031). The corneal back Z40 of the clear corneal incision group was -0.02 ± 0.25, compared to -0.04 ± 0.21 in the limbus tunnel incision group (p = 0.01). One month after the operation, the corneal back SIA of the clear corneal incision group was 0.11 ± 0.11, compared to 0.08 ± 0.11of the limbus tunnel incision group (p = 0.013), the corneal total SIA of the clear corneal incision group was 0.33 ± 0.30, compared to 0.15 ± 0.16 in the limbus tunnel incision group (p = 0.004); the clear corneal incision group exhibited higher levels of back astigmatism and total SIA than the limbus tunnel incision in the post-operation one month period. During the 6- month post-operative follow-up period, no significant difference in Z31, Z40, and other HOA RMS data was observed between the two groups. The total SIA of the corneal incision group and the limbus tunnel incision group were 0.24 ± 0.14 and 0.33 ± 0.32, respectively (p = 0.393), showing no significant difference between the two groups 6 months after the operation. CONCLUSION: Our data showed no significant difference in the high-order aberration and SIA between clear corneal incision and limbus tunnel incision up to 6 months after ICL-V4c implantation.

Small incision lenticule extraction for the treatment of myopic anisometropia / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To explore the clinical effect of small incision lenticule extraction(SMILE)on the treatment of myopic anisometropia.METHODS: Clinical data of 76 patients(146 eyes)with myopic anisometropia who received SMILE or femtosecond assisted laser in situ keratomileusis(FS-LASIK)in our hospital from January 2021 to December 2022 were retrospectively analyzed. The patients were divided into SMILE group(39 cases, 77 eyes)and FS-LASIK group(37 cases, 69 eyes)according to surgical methods. Uncorrected visual acuity(UCVA), diopter, anisometropia, corneal aberration and occurrence of postoperative complications were compared between the two groups at 1 wk, 1 and 3 mo after surgery.RESULTS: The UCVA of the two groups was improved after surgery compared with that before surgery, and the coma, trefoil, spherical aberration and total higher-order aberration were significantly increased compared to those before surgery(P<0.05), and the coma, trefoil, spherical aberration and total higher-order aberration in the FS-LASIK group were significantly higher than those in the SMILE group(P<0.05). After follow-up to 3 mo after surgery, the incidence of postoperative complications was significantly lower in the SMILE group than that in the FS-LASIK group(5.2% vs 15.9%, P<0.05).CONCLUSION: Both SMILE and FS-LASIK can effectively enhance the UCVA and improve the visual quality in patients with myopic anisometropia, but SMILE has lower corneal higher order aberrations, lower incidence of postoperative complications and better overall effect.

One-year clinical efficacy evaluation of selective corneal wavefront aberration-guided FS-LASIK correction in patients with high myopia.

AIM: To evaluate the effectiveness, safety, predictability, precision and changes of higher-order aberrations (HOAs) on corneal front surface of selective corneal wavefront aberration-guided femtosecond laser-assisted in situ keratomileusis (CW-FS-LASIK) in patients with high myopia 1-year postoperatively. METHODS: Totally 74 eyes of 37 patients with high myopia or myopic astigmatism in both the eyes who underwent the CW-FS-LASIK procedure in Xi'an Gaoxin Hospital from January 2021 to June 2021 were included. The changes of uncorrected distance visual acuity (UDVA), best corrected visual acuity (BCVA), spherical equivalent refraction (SER), astigmatism, HOAs and Strehl ratio (SR) on the anterior surface of the cornea after 1y of the surgery were analyzed. RESULTS: At postoperative 1y, the UDVA (logMAR) of 74 eyes (100%) reached 0 or better, including 0 in 8 eyes (10.81%), -0.1 in 45 eyes (60.81%), and -0.2 in 21 eyes (28.38%). The effectiveness index was 1.29±0.134. There was no decrease in postoperative BCVA compared with preoperative BCVA in all patients. Postoperative BCVA was the same in 44 eyes (59.46%) as preoperative BCVA, increased by 1 line in 23 eyes (31.08%) and increased by 2 lines in 7 eyes (9.46%) compared with preoperative BCVA. The safety index was 1.11±0.159. The estimated corrected SER before surgery was (-7.76±1.21) D, and the actual corrected SER was (-7.83±1.25) D (Y=0.9811X+0.2156, R2=0.9084). There was a high correlation between the estimated corrected SER and the actual corrected SER. The postoperative SER in 74 eyes (100%) was within ±0.75 D. The postoperative astigmatism of all was within -0.75 D to 0. Root mean square (RMS) HOAs of spherical aberration and SR within 5 mm of the corneal front surface were all increased compared with those before operation (P<0.01). The total coma, horizontal coma and vertical coma were all decreased compared with those before operation (P<0.01). There was no statistically significant difference in horizontal trefoil and vertical trefoil compared with preoperative ones (P>0.05). CONCLUSION: Selective CW-FS-LASIK for correction of high myopia is effective, safe, predictive, and accurate. For patients with preoperative RMS HOAs over 0.25 defocus equivalent, postoperative coma aberration can be significantly reduced, and SR value can be increased, thus corneal imaging quality can be improved.

Evaluating the topographical measurements and tear function status in patients with hemifacial spasm: A comparative fellow eye study.

OBJECTIVE: To investigate the effect of eyelid spasm on corneal and tear film characteristics in patients with hemifacial spasm (HFS) and compare these data with those of the contralateral eyes of the same patients. METHODS: This prospective study is comprised of 64 eyes of 32 HFS patients, 32 eyes on the spasm side (Group 1) and 32 contralateral eyes (Group 2). Corneal tomographic analyses were performed; corneal power of flat axis (K1) and steep axis (K2), astigmatism and thinnest pachymetry; anterior, posterior and total corneal aberrometry [spherical aberration (SA), vertical coma (vcoma), horizontal coma (hcoma), total higher order aberration (THOA) and total RMS], and corneal densitometry values were evaluated and compared between groups. Tear meniscus height and depth (TMH, TMD) were measured using anterior segment optic coherence tomography. Tear function tests including TMH and TMD, the Schirmer I test, and tear break-up time (TBUT) were compared between the groups. RESULTS: K1, K2, astigmatism and corneal densitometry values were similar between groups (p > 0.05). Thinnest pachymetry values were significantly thinner on the spasm side (p = 0.040). Anterior and total corneal SA and RMS were significantly higher on the spasm side (p = 0.032, p = 0.005; p = 0.015, p = 0.006, respectively). TMH, TMD and TBUT were significantly lower in Group 1 (p = 0.01, p = 0.02 and p = 0.03, respectively). Schirmer I test values were similar between groups (p > 0.05). CONCLUSION: In HFS patients, there are changes in corneal parameters and tear film in the eye on the spasm side compared to unaffected eye.

Visual quality observation of transepithelial photorefractive keratectomy and femtosecond small incision lenticule extraction for the correction of low myopia / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To observe the changes in corneal aberrations and the characteristics of visual quality after transepithelial photorefractive keratectomy(T-PRK)and femtosecond small incision lenticule extraction(SMILE)in the correction of low myopia.METHODS: Prospective cohort study. A total of 32 cases(32 eyes)with low myopia who underwent T-PRK surgery and 45 cases(45 eyes)of SMILE surgery at Weifang Eye Hospital from April 2021 to April 2022 were selected. The uncorrected visual acuity(UCVA), best corrected visual acuity(BCVA), spherical equivalent(SE), corneal higher-order aberrations(HOAs)and objective visual quality were compared between the two groups.RESULTS:All patients completed the surgery successfully without complications such as infection. At 3mo postoperatively, the safety index was 1.13±0.16 and 1.16±0.17(P=0.48)and the efficacy index was 1.10±0.20 and 1.15±0.18(P=0.27)in the T-PRK and SMILE groups, respectively. The percentage of UCVA(LogMAR)≤0 in the T-PRK and SMILE groups was 94% and 98%, respectively. The percentage of the residual SE within ±0.5D was 88% and 87% in the two groups, respectively. The HOAs and spherical aberration in both groups were significantly increased(P≤0.01), and the increase was not statistically significant between the two groups(P=0.31, 0.89). There was no significant change in horizontal coma, horizontal trefoil and vertical trefoil in both groups(P&#x0026;#x003E;0.05). The vertical coma in SMILE group was significantly increased(P&#x0026;#x003C;0.001), while there was no significant change in T-PRK group(P&#x0026;#x003E;0.05), and the increase was significantly greater in SMILE group than in T-PRK group(P&#x0026;#x003C;0.001). There was no significant difference in objective scattering index(OSI), modulation transfer function cut off frequency(MTFcut off), Strehl ratio(SR), visual acuity(VA)100%, VA20% and VA9% between the two groups(P&#x0026;#x003E;0.05).CONCLUSION:Both T-PRK and SMILE showed good safety, efficacy, and visual quality in correcting low myopia, while SMILE induced more vertical coma than T-PRK.

Agreement of corneal high-order aberrations measured by three wavefront aberrometers in myopic adults / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To evaluate the agreement of corneal high-order aberrations from Topcon KR-1W, i.Profiler and OPD-Scan Ⅲ wavefront aberrometers in myopic adults.METHODS:A prospective clinical study. A total of 92 adult patients(92 eyes)with myopia in the department of optometry, the People's Hospital of Guangxi Zhuang Autonomous Region from June to August 2022 were enrolled. The third-order and fourth-order corneal aberrations at the pupil diameter of 4 and 6mm were measured by Topcon KR-1W, i.Profiler, and OPD-Scan Ⅲ, respectively. The difference and agreement of the three aberrometers were evaluated.RESULTS: The measurements at 6mm pupil diameter were all greater than those at 4mm pupil diameter. Although there were no statistical differences in the measurements of Z-44、Z-24 by the three aberrometers at 4 pupil diameter(P&#x003E;0.05), there were statistical differences in other measurements(P&#x003C;0.05). The aberration results measured by the three aberrometers were statistically different at the 6mm pupil diameter(P&#x003C;0.05). The 95% limit of agreement(95%LoA)of the measurements of higher-order aberration, including the third-order aberrations at 4mm pupil diameter and the third-order and fourth-order aberrations at 6mm pupil diameter(except for the Z-24)were greater than 0.1μm. The concordance correlation coefficient(Pc)was lower than 0.90, indicating a poor consistency. The correlation coefficients of corneal higher-order aberrations were significantly different among the three aberrometers at 4 and 6mm pupil diameter(r4mm=0.215～0.805, P4mm&#x003C;0.05; r6mm=0.561～0.916, P6mm&#x003C;0.001).CONCLUSION:There were significant differences in the measurements of the third- and fourth-order corneal aberrations at 4 and 6mm pupil diameter among Topcon KR-1W, i.Profiler, and OPD-Scan Ⅲ, and the agreements were poor, so they are not interchangeably in clinical applications.

Effects of rigid gas permeable contact lens on morphological parameters and vision-related quality of life in keratoconus patients.

AIM: To evaluate the effect of rigid gas permeable contact lens (RGP-CL) on corneal morphological parameters and vision-related quality of life in keratoconus (KC) patients. METHODS: Totally 57 eyes of 30 KC patients who were followed-up for more than two years, including 17 RGP wearers (32 eyes) and 13 non-wearers (25 eyes) were retrospectively analyzed. Initial medical history and corneal topography were collected at baseline. Corneal topography, corneal aberration, optical coherence tomography, and vision-related quality of life questionnaires were performed at the last follow-up. RESULTS: According to corneal topography, increase of the flattest keratometric values was higher in RGP wearers than in non-wearers (P=0.038). The morphological parameters, including symmetry index of front corneal curvature (P=0.004) and Baiocchi-Calossi-Versaci index front (P=0.047), were lower in RGP wearers than in non-wearers. Vertical coma was smaller in RGP wearers than non-wearers in 3.0, 5.0, 6.0, and 7.0 mm pupil diameters, respectively (P<0.05). The environmental triggering domain of ocular surface disease index was worse in RGP wearers as compared to non-wearers (P=0.003). At the last follow-up, there were no significant differences in constituent ratios of KC progression, corneal thickness topography, epithelial thickness topography, morphological parameters of corneal topography, and other questionnaire scores between the two groups (all P>0.05). CONCLUSION: Long-term use of RGP does not worsen KC but may cause corneal epithelial remodeling to increase symmetry of corneal anterior surface, reduce corneal vertical coma and improve visual quality. However, RGP wearing causes a slight decrease in vision-related quality of life. The occurrence of ocular surface symptoms is mainly associated with environmental triggering factors.

Repeatability of i.Profiler for measuring wavefront aberrations in healthy eyes.

PURPOSE: To evaluate the repeatability of wavefront aberration measurements and the correlation between corneal aberration and pupil size in normal eyes using a wavefront-based autorefractor (i.ProfilerPlus; Carl Zeiss Vision, Germany). METHODS: A prospective cross-sectional study. Wavefront aberrations, including spherical aberration (SA) (Z40), coma (Z3-1, Z31), trefoil (Z3-3, Z33) and total higher-order aberrations (tHOA), were measured at different pupil diameters. The repeatability was evaluated using one-way ANOVA method, and statistical indicators including within-subject standard deviation (Sw), test-retest repeatability (TRT), and intra-class correlation coefficient (ICC). The correlations between corneal aberrations and pupil sizes were evaluated by Pearson correlation analysis. RESULTS: A total of 96 healthy young volunteers were enrolled. Corneal and ocular higher-order aberrations (HOA) measured by i.Profiler showed Sw < 0.01 µm, TRT < 0.10 µm, ICC > 0.90. There was a linear positive correlation between the corneal HOA and pupil size. The correlation coefficient between SA and tHOA was the largest (r = 0.996, P < 0.001). CONCLUSIONS: The measurements of wavefront aberrations by i.Profiler are highly repeatable. Corneal HOA was significantly dependent on pupil size. SA was the most influential aberration for visual quality in this study.

Effects of long-term soft contact lens wear on corneal epithelial thickness after small incision lenticule extraction.

The present study investigated changes in corneal epithelial thickness after small incision lenticule extraction (SMILE) in patients with long-term preoperative soft contact lens (SCL) wear, the impact of SCL wear on the efficacy of surgical outcomes and the effects of long-term SCL wear on postoperative corneal aberrations. Patients were assigned to three groups according to the duration of SCL wear: Group A, the non-SCL-wearing group; group B, those with SCL wear ≤1 year; and group C, those with SCL wear >1 year. Epithelial thickness was recorded in nine zones by anterior segment optical coherence tomography across a 5-mm diameter before surgery and at 1 week, and 1, 3 and 6 months post-surgery. Corneal epithelial thickness and corneal aberrations among the three groups were compared, as well as the effects of changes in corneal epithelial thickness on postoperative visual acuity and manifest refraction. No significant differences were noted with regard to age or preoperative spherical equivalent among groups A (22 eyes), B (17 eyes) and C (18 eyes). Preoperative corneal epithelial thickness in the inferonasal, inferior and inferotemporal zones was thinner in group B compared with that in group A, and corneal epithelial thickness was thinner in all nine zones in group C compared with that in group A (P<0.05). At all follow-up time points, in the central, nasal, inferonasal, inferior, inferotemporal and temporal areas, the epithelial thickness was thinner in group C compared with that in group A (P<0.05). At 3 months postoperatively, the epithelial thickness was thinner in the inferonasal and inferior sectors in group C compared with that in group B (P<0.05), and at 6 months postoperatively, the epithelial thickness in the inferior region was thinner in group C compared with that in group B (P<0.05). There were no significant differences in visual acuity or manifest refraction among the three groups at all postoperative time points. The total higher-order aberrations were greater in group C compared with those in group A for all time points (P<0.05) and were greater in group C at 1 and 3 months postoperatively compared with those in group B (P<0.05). The spherical aberrations at 3 and 6 months postoperatively were greater in group C compared with those in group A (P<0.05). The coma aberrations were greater in group C compared with those in groups A and B for all time points (P<0.05). In conclusion, long-term SCL wear will result in corneal epithelial thinning, which does not impact visual acuity or manifest refraction after SMILE.

Corneal morphology and visual quality observation after Trans-PRK with smart pulse technology in the correction of myopia and astigmatism / 中华实验眼科杂志

Objective:To observe the corneal morphology and visual quality after transepithelial photorefractive keratectomy (Trans-PRK) with smart pulse technique (SPT) and 1 050 Hz cutting frequency in the correction of myopia and astigmatism.Methods:A self-controlled case series study was conducted.Sixty five eyes of 33 patients who underwent Trans-PRK surgery in Ineye Hospital of Chengdu University of TCM from July 2017 to June 2018 were followed up for 6 months.The uncorrected visual acuity (UCVA) converted to logarithm of the minimum angle of resolution (LogMAR) unit, best corrected visual acuity (BCVA) (LogMAR), and spherical equivalent (SE) of the subjects were recorded.The anterior corneal surface symmetry index (SI), the anterior corneal surface Q value in the range of 6, 7, 8, and 9 mm diameter, the spherical aberration, coma, trefoil and total higher-order aberration of the anterior corneal surface, the strehl ratio (SR), and the modulation transfer function (MTF) of 10, 20, 30, and 40 c/d in the horizontal and vertical meridian directions before and after surgery were measured with Sirius corneal topography analyzer.The differences of each index among different time points were compared, and the correlation between indexes was analyzed by Pearson correlation analysis.This study followed the Declaration of Helsinki.The study protocol was approved by the Medical Ethics Committee of Ineye Hospital of Chengdu University of TCM (No.2020yh-004). All patients signed the informed consent form before surgery.Results:The average preoperative BCVA and SE were -0.09±0.06 and (-4.24±1.24)D.The mean UCVA and SE at 7 days, 1, 3 and 6 months postoperatively were -0.10±0.08 and (0.03±0.63)D, -0.12±0.06 and (0.08±0.53)D, 1.16±0.06 and (0.02±0.79)D, -0.18±0.05 and (0.08±0.37)D, respectively.The SI at different time points after the surgery were significantly higher than that before operation (all at P<0.05). At 1, 3 and 6 months after surgery, the Q value of anterior corneal surface in different diameter ranges increased from negative to positive, showing statistically significant differences (all at P<0.05). At each time point after surgery, the trefoil and total higher-order aberrations of the anterior corneal surface increased to varying degrees.Coma at 7 days and 6 months after surgery were significantly higher than that before surgery, and spherical aberration at 3 and 6 months after surgery were significantly higher than that before surgery (all at P<0.05). The SR values at 3 and 6 months after operation were significantly higher than that before operation (all at P<0.05). At 6 months after operation, the MTF values at different spatial frequencies of the horizontal meridian and the MTF values at 30 and 40c/d spatial frequencies of the vertical meridian were lower than those before operation, and the differences were statistically significant (all at P<0.05). The correlation analysis showed that the Q value of different diameter ranges was positively correlated with spherical aberration ( r=0.798-0.925, P<0.05), total higher-order aberration ( r=0.596-0.630, P<0.05), SI ( r=0.235-0.303, P<0.05) and corneal ablation depth ( r=0.583-0.659, P<0.05) at 6 months after surgery.SI was positively correlated with spherical aberration ( r=0.307, P<0.05), coma ( r=0.424, P<0.05), total higher-order aberration ( r=0.300, P<0.05), corneal ablation depth ( r=0.227, P<0.05), and eccentric cutting amount ( r=0.281, P<0.05). There was no correlation between SR and aberration, corneal ablation depth, eccentric cutting amount, etc.(all at P≥0.05). Conclusions:Trans-PRK using SPT to correct myopic astigmatism can improve vision, stabilize diopter, enhance retinal imaging quality, increase the asymmetry of the anterior corneal surface, and introduce different degrees of higher-order aberrations.

The short term effect of trehalose and different doses of sodium hyaluronate on anterior corneal aberrations in dry eye patients.

AIM: To evaluate the short-term effect of 0.15% sodium hyaluronate (SH), 0.20% SH, and Trehalose + 0.15% SH on anterior corneal aberrations in dry eye patients. METHODS: 76 eyes of 76 dry eye patients were divided into three groups. Non-preserved 1.5 mg/mL SH was administered in group 1, non-preserved 2.0 mg/mL SH was administered in group 2, and non-preserved trehalose 30 mg/mL and 1.5 mg/mL SH was administered in group 3. Aberrometry measurements were performed before and 10 min after application of the artificial tear drop. Using the Pentacam Scheimpflug imaging system, total root mean square (RMS), lower-order aberration (LOA), higher-order aberrations (HOAs), spherical aberration (SA), trefoil, and coma aberrations were investigated. RESULTS: In each group; the RMS of total, LOA, HOAs, and spherical aberration were significantly decreased after the artificial drop instillation, compared with those of them at baseline; and in groups 1 and 2, vertical trefoil term was also significantly increased, compared with those of them at baseline. According to intergroup analyzes, there was no significant outcome. CONCLUSIONS: It was observed that three artificial tears reduced the anterior corneal aberrations, in a 10-min period. The short-term effect of three artificial tears on the anterior corneal aberration was similar.

Short and long term outcomes after small-incision lenticule extraction: A tertiary referral centre experience.

PURPOSE: The objective of this study is to evaluate the preoperative and short- and long-term postoperative results in terms of visual acuity, refractive error, and corneal wavefront aberrations in patients with myopia and myopic astigmatism undergoing small incision lenticule extraction (SMILE). METHODS: Seventy-nine eyes of 52 myopes with or without astigmatism (41 right and 38 left) were enrolled in this retrospective study. The measurements included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent (SE) and wavefront aberrations. All the measurements before and after SMILE surgery were systematically recorded. RESULTS: Mean preoperative UDVA was 1.19±0.24 logMAR and improved to 0.06±0.17 logMAR at the 3-year postoperative follow-up. At the conclusion of the 3-year follow-up, UDVA was better than or equal to 20/20 and 20/25 in 73% and 84% of eyes, respectively. At 1 month postoperatively, CDVA was 0.05±0.23 logMAR and significantly lower than the preoperative CDVA, 0.02±0.04 log MAR (P>0.05). However, at 1 year and 3 years after surgery, CDVA showed a significant increase compared to preoperative CDVA. At the conclusion of the 3-year follow-up, SE was -0.47 D, and 69.6% and 83.5% of the eyes were within±0.50 D and±1.00 D, respectively, of the intended correction. HOA's, coma, and spherical aberration increased significantly. No significant change in trefoil was detected. CONCLUSION: This study showed that SMILE produces a stable, safe outcome for surgical treatment of myopia and myopic astigmatism.

[Comparison of corneal epithelial remodeling after small incision lenticule extraction and femtosecond laser-assisted LASIK].

Objective: To investigate the corneal epithelial thickness changes between small incision lenticule extraction (SMILE) and femtosecond laser-assisted LASIK (FS-LASIK), study the related factors and analyze the relationship between the changes in corneal epithelial thickness and corneal aberration. Methods: This case control study included 59 patients (118 eyes), 27 males and 32 females, aged 25.64±5.57 years, who were scheduled for SMILE or FS-LASIK for treatment of myopia with or without myopic astigmatism at the First Affiliated Hospital of Soochow University between October 2016 and May 2017. All patients were divided into two groups according to the surgery. Epithelial thickness was obtained in nine zones with Fourier-domain optical coherence tomography across a 5-mm diameter centered by the pupil before surgery and at 1 week, 1 month, 3 months and 6 months postoperatively. The observed changes were analyzed by linear-regression analysis with the central corneal thickness decrement, ablation rate and corneal aberration. Comparison between two groups was analyzed by independent sample t-test, analysis of variance and Mann-Whitney U test. Results: There was no significant difference in corneal epithelial thickness of nine zones between SMILE and FS-LASIK for low to moderate myopia (manifest refraction sphere equivalent<-6.00 diopters) and high myopia (manifest refraction sphere equivalent ≥-6.00 to -10.00 diopters), respectively, before surgery (P>0.05). At 1 month, no significant difference existed in corneal epithelial thickness increment in nine zones between FS-LASIK and SMILE for low to moderate myopia (P>0.05), but a larger increase was observed in the superior (t=2.670, P=0.010), superonasal (t=2.506, P=0.015) and nasal (t=2.831, P=0.007) zones following FS-LASIK [(4.2±3.2), (3.4±2.7) and (3.7±2.5) µm] than SMILE [(2.2±2.2), (1.6±2.5) and (1.7±2.6) µm] for high myopia. At 3 months, a larger increase in corneal epithelial thickness was observed in the superior (t=2.703, P=0.009) zone following FS-LASIK than SMILE for low to moderate myopia, and the same increase was observed in the central (t=2.660, P=0.010), superior (t=3.229, P=0.002), nasal (t=2.420, P=0.019), inferonasal (t=2.651, P=0.011), inferotemporal (t=2.153, P=0.036) and superotemporal (t=2.281, P=0.027) zones after FS-LASIK [(6.7±2.6), (5.0±2.1), (3.9±1.9), (4.8±1.8), (7.5±2.5) and (6.4±2.7) µm] than SMILE [(4.7±2.9), (2.9±2.5), (2.4±2.4), (3.3±2.2), (6.0±2.4) and (4.8±2.4) µm] for high myopia. At 6 months, a larger increase in corneal epithelial thickness was observed in the superior (t=3.340, P=0.001) and nasal (t=1.952, P=0.055) zones following FS-LASIK than SMILE for low to moderate myopia, and the same increase was observed in the superior (t=2.332, P=0.024) and inferonasal (t=2.172, P=0.034) zones after FS-LASIK than SMILEfor high myopia. The central corneal thickness decrement after SMILE was much more than FS-LASIK both in the low to moderate myopia and high myopia groups (P<0.05). The average corneal epithelial thickness increment correlated positively with the central corneal thickness decrement and ablation rate at 1 month, 3 months and 6 months postoperatively (P<0.01). For SMILE, the total higher orders aberration (0.81±0.26, 0.79±0.28 and 0.81±0.31) and spherical aberration (0.50±0.21, 0.48±0.20 and 0.52±0.23) were less than FS-LASIK (0.97±0.34, 0.97±0.33 and 0.93±0.32; 0.72±0.25, 0.66±0.30 and 0.71±0.25) at 1 month, 3 months and 6 months postoperatively (P<0.05). Furthermore, the corneal aberration increment correlated positively with the average corneal epithelial thickness increment (P<0.05). Conclusions: The corneal epithelial thickness increment after SMILE was less than FS-LASIK. SMILE had better uniformity of the corneal epithelial thickness increment at the observed zones, which may explain the finding that the postoperative spherical aberration of SMILE was less than FS-LASIK. (Chin J Ophthalmol, 2020, 56:93-102).

Evaluation of Changes in Visual Acuity, Contrast Sensitivity and Aberrations in Patients with Keratoconus after Corneal Collagen Cross-linking.

PURPOSE: To assess and compare preoperative refractive, aberrometric, topographic, and contrast sensitivity (CS) measurements with postoperative values after corneal collagen cross-linking (CXL) in patients with progressive keratoconus. METHODS: Twenty-two eyes of 11 patients with keratoconus were enrolled in this prospective study. Uncorrected distance visual acuity (UDVA), best spectacle corrected visual acuity (BSCVA), CS, and higher order aberrations (HOAs) were evaluated at baseline and 1, 3, 6, and 8 months after surgery. RESULTS: The mean total HOAs of the included patients were 2.24, 2.34, 2.28, 2.17, and 2.03 µm before and 1, 3, 6, and 8 months after CXL, respectively. A significant reduction in corneal HOAs including vertical coma, vertical and horizontal trefoil and spherical aberration was observed 6 and 8 months after CXL. UDVA and BSCVA improved significantly in all patients who completed the follow-up period (P = 0.001). Although mean CS declined significantly 1 month postoperatively, it improved significantly after 3, 6, and 8 months (P<0.001). Maximum keratometry was significantly lower 8 months postoperatively compared to the preoperative value. (P = 0.006). CONCLUSIONS: CXL seems to improve UCVA, BSCVA, and CS and reduce most corneal HOAs in progressive forms of keratoconus.

Aberration-free intraocular lenses - What does this really mean?

BACKGROUND: So-called aberration-free intraocular lenses (IOLs) are well established in modern cataract surgery. Usually, they are designed to perfectly refract a collimated light beam onto the focal point. METHODS: We show how much aberration can be expected with such an IOL in a convergent light beam such as that found anterior to the human cornea. Additionally, the aberration in a collimated beam is estimated for an IOL that has no aberrations in the convergent beam. The convergent beam is modelled as the pencil of rays corresponding to the spherical wavefront resulting from a typical corneal power of 43m-1. The IOLs are modelled as infinitely thin phase plates with 20m-1 optical power placed 5mm behind the cornea. Their aberrations are reported in terms of optical path length difference and longitudinal spherical aberration (LSA) of the marginal rays, as well as nominal spherical aberration (SA) calculated based on a Zernike representation of the wavefront-error at the corneal plane within a 6mm aperture. RESULTS: The IOL designed to have no aberrations in a collimated light beam has an optical path length difference of -1.8µm, and LSA of 0.15m-1 in the convergent beam of a typical eye. The corresponding nominal SA is 0.065µm. The IOL designed to have no aberrations in a convergent light beam has an optical path length difference of 1.8µm, and LSA of -0.15m-1 in the collimated beam. CONCLUSIONS: An IOL designed to have no aberrations in a collimated light beam will increase the SA of a patient's eye after implantation.

Comparison of Corneal Higher-order Aberration before and after Excision of Pterygium

PURPOSE: To investigate the types of corneal higher-order aberration (HOA) induced by pterygium, residual corneal HOA after pterygium surgery, and correlations between corneal HOA and the length of the pterygium. METHODS: Fifty-three patients who underwent pterygium excision with conjunctival autograft were enrolled. Corneal HOA was measured by Pentacam® (Oculus Inc., Wetzlar, Germany) preoperatively and 3 months postoperatively in the 6-mm optical zone. Preoperative and postoperative HOAs of eyes with pterygium were compared with HOAs of the fellow eye to evaluate HOAs induced by pterygium and residual HOAs after pterygium surgery. Partial correlation analysis was performed to investigate the relationship between HOAs and the length of pterygium. A postoperative HOA less than 0.35 µm in size was defined as a favorable surgical outcome and the surgical indications were estimated using receiver operator characteristic (ROC) curve. RESULTS: Horizontal coma, root mean square (RMS) of coma, oblique trefoil, horizontal trefoil, RMS of trefoil, and total HOA were significantly greater in the eye with preoperative pterygium. Three months after pterygium excision, only RMS of coma and total HOA remained significantly greater in eyes with pterygium. Vertical coma, horizontal coma, RMS of coma, and oblique tetrafoil were correlated with pterygium length. Pterygium excision when pterygium length was less than 1.6 mm led to favorable surgical outcomes. CONCLUSION: Pterygium induced greater than third-order corneal HOAs and these HOAs were corrected via pterygium surgery. Longer pterygium length was associated with larger RMS of coma and larger coma RMS persisted after pterygium surgery. A pterygium length of 1.6 mm should be considered the cutoff for pterygium excision for reducing postoperative corneal HOA.

Effectiveness analysis for reconstruction algorithms of the corneal aberration applied in adaptive optics / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM:To investigate the accuracy, time-consuming and reliability of three Zernike algorithms in reconstruction of the corneal aberration in adaptive optics.<p>METHODS: Elevation data of corneal front surface collected on 20 normal eyes over a 6mm pupil were converted into the simulated original wave-front data by subtracting the best fitting sphere, which was then resampled at resolutions of 100, 300, and 500μm. Differences in elevation between adjacent pixels were used to generate simulated wave-front slope data, which were used to reconstruct wave-front by three algorithms: the regularized solution, the singular value decomposition, and Householder transform separately. The number of Zernike modes was from 1 to 130 separately in each reconstruction procedure. Each new wave-front map generated was directly compared to the originally sampled wave-front and the residual root-mean-square(RMS)error between the original and reconstructed map was recorded, also we investigate the time-consuming and reliability of the solution by calculating the condition numbers of the linear model and observing the mode coefficient matrix. <p>RESULTS: Householder transformation performed as well as the singular value decomposition by three sampling rates in reconstruction accuracy, while the regularized solution showed unacceptable results when the number Zernike modes used higher than 88 by the resolution was 500μm. With the modes number increased, the time that the singular value decomposition consumed increased more obviously than the time that the Householder transformation and the regularized solution consumed, and the difference between the latter two didn't show obviously. The higher the sampling rate was, also the lower the Zernike exponent number was, and the more reliable the result was, and the instability of regularized solution is more serious than the other two at the low sampling rate.<p>CONCLUSION:Householder transformation is superior the other two in accuracy as well as the highly effectiveness, and the reliability of three algorithms was almost identical at high sampling rate, while the Householder transformation still showed relatively stable performance at low sampling rate, which provides the reference and the theory basis of choice to the optimal algorithm which is applied in the adaptive optics system of real-time correction eyeball's aberration wave-front reconstruction.

Correlation between visual function and refractive, topographic, pachymetric and aberrometric data in eyes with keratoconus.

AIM: To analyze the relationship between two visual functions and refractive, topographic, pachymetric and aberrometric indicators in eyes with keratoconus. METHODS: Corrected distance visual acuity (CDVA), and letter contrast sensitivity (CS) were correlated with refraction, corneal topography, pachymetry, and total corneal wavefront data prospectively in 71 eyes with keratoconus. The topographic indices assessed were simulated keratometry for the flattest and steepest meridians (SimK1 and SimK2), posterior steeper K (Ks), elevation value in best-fit sphere (BFS) maps, squared eccentricity (Є(2)), aspheric asymmetric index (AAI), pachymetry, thickness progression index (TPI), the amount of pachymetric decentralization (APD), and GalileiTM-keratoconus indices. RESULTS: The mean CDVA (expressed as logMAR) were 0.25±0.21. The mean CS was 1.25±0.46. The spherical refraction correlated well with CDVA (r=-0.526, P<0.001). From topographic indices, SRI correlated with CS (r=-0.695), and IAI with CS (r=-0.672) (P<0.001 for all). Root mean square (RMS) was 4.3±1.81 µm, spherical aberration (SA) was -0.4±0.67 µm, vertical and horizontal coma were -2.1±1.47 and -0.4±0.72 µm. All wavefront data (except horizontal coma), AAI, Є(2) and maximum BFS correlated significantly with the visual function (P≤0.001 for all). CONCLUSION: In this study, CS is more affected than CDVA as a visual function. The quantity and quality of vision is significantly correlated with well-known and new topographic indices. There is not a significant correlation between visual function and pachymetric parameters. The significantly correlated indices can be used in staging keratoconus and to follow the outcome of a treatment.

Optimal incision sites to reduce corneal aberration variations after small incision phacoemulsification cataract surgery.

AIM: To analyze the effect of steep meridian small incision phacoemulsification cataract surgery on anterior, posterior and total corneal wavefront aberration. METHODS: Steep meridian small incision phacoemulsification cataract surgery was performed in age-related cataract patients which were divided into three groups according to the incision site: 12 o'clock, 9 o'clock and between 9 and 12 o'clock (BENT) incision groups. The preoperative and 3-month postoperative root mean square (RMS) values of anterior, posterior and total corneal wavefront aberration including coma, spherical aberration, and total higher-order aberrations (HOAs), were measured by Pentacam scheimpflug imaging. The mean preoperative and postoperative corneal wavefront aberrations were documented. RESULTS: Total corneal aberration and total lower-order aberrations decreased significantly in three groups after operation. RMS value of total HOAs decreased significantly postoperatively in the 12 o'clock incision group (P<0.001). Corneal spherical aberration was statistically significantly lower after steep meridian small incision phacoemulsification cataract surgery in BENT incision group (P<0.05) and Pearson correlation analysis indicated that spherical aberration changes had no significant relationship with total astigmatism changes in all three corneal incision location. CONCLUSION: Corneal incision of phacoemulsification cataract surgery can affect corneal wavefront aberration. The 12 o'clock corneal incision eliminated more HOAs and the spherical aberrations decreased in BENT incision group obviously when we selected steep meridian small incision. Cataract lens replacement using wavefront-corrected intraocular lens combined with optimized corneal incision site would improve ocular aberration results.