Corneal higher order aberrations by Sirius topography and their relation to different refractive errors.

PURPOSE: To compare the root mean square (RMS) of anterior corneal higher-order aberrations (HOAs) in ametropic and emmetropic eyes. METHODS: This retrospective observational study was conducted at the Department of Ophthalmology, Tishreen University Hospital, Latakia, Syria. Study eyes were divided into four groups based on refractive error: mild-to-moderate myopia, hypermetropia, myopic astigmatism, and emmetropic eyes as controls. The following anterior corneal HOAs were evaluated using the Scheimpflug-Placido Sirius (CSO, Italy) tomographer over 6 mm pupil: Root mean square (RMS) total corneal HOAs, RMS trefoil, RMS coma and RMS spherical aberrations. RESULTS: RMS values of total HOAs, trefoil and coma showed statistically significant differences in all four groups (P < 0.05, all). HOAs were noted to be lowest in the control group (0.18 ± 0.09, 011 ± 0.08 and 0.09 ± 0.08 µm, respectively) and highest in the myopic astigmatism group (0.31 ± 0.16, 0.15 ± 0.12, 0.17 ± 0.14 µm, respectively). RMS spherical aberration was lowest in the astigmatism group (0.00 ± 0.16 µm) with a statistically significant difference from that in the control group (0.05 ± 0.07 µm, P = 0.049). CONCLUSION: The mean RMS values of total HOAs, trefoil and coma were highest in the astigmatism group and lowest in the control group. However, spherical aberration was minimal in the astigmatism group. A better understanding and targeted treatment of higher-order aberrations in ametropic human eyes, and in particular eyes with astigmatism, may enhance visual quality and performance in the treatment of refractive errors. Recognising atypical HOAs may also assist in the early detection of pathological conditions such as keratoconus.

Effect of preoperative pupil offset on corneal higher-order aberrations after femtosecond laser-assisted in situ keratomileusis.

BACKGROUND: This study aimed to investigate the relationship between multiple higher-order aberrations (HOAs) subgroups and pupil offset, as well as to analyze the factors affecting postoperative corneal HOAs in patients with different degrees of refractive errors. METHODS: We enrolled 160 patients (316 eyes) aged ≥ 18 years who had undergone femtosecond laser-assisted in situ keratomileusis (FS-LASIK) treatment. Based on the relationship between the preoperative pupil offset and the postoperative ΔHOAs, all patients were divided into two groups: group I (pupil offset ≤ 0.20 mm) and group II (pupil offset > 0.20 mm). All of the eyes had low to high myopia with or without astigmatism (manifest refraction spherical equivalent (MRSE) < -10.00 D). Uncorrected distance visual acuity, corrected distance visual acuity, MRSE, pupil offset, central corneal thickness, corneal HOAs, vertical coma (Z3-1), horizontal coma (Z31), spherical aberration (Z40), trefoil 0° (Z33), and trefoil 30° (Z3-3) over a 6 mm diameter central corneal zone diameter were evaluated preoperatively and at 1 and 3 months postoperatively. RESULTS: Our result revealed significant differences in postoperative corneal total root mean square (RMS) HOAs, RMS vertical coma, RMS horizontal coma, RMS spherical aberration, and RMS trefoil 30° between group I and group II. ΔMRSE was found to be an effective factor for ΔRMS HOAs (R2 = 0.383), ΔRMS horizontal coma (R2 = 0.205), and ΔRMS spherical aberration (R2 = 0.397). In group II, multiple linear regression analysis revealed a significant correlation between preoperative pupillary offset and Δtotal RMS HOAs (R2 = 0.461), ΔRMS horizontal coma (R2 = 0.040), and ΔRMS trefoil 30°(R2 = 0.089). The ΔRMS vertical coma effect factor is the Y-component, and the factor influencing ΔRMS spherical aberration was ΔMRSE (R2 = 0.256). CONCLUSION: A small pupil offset was associated with a lower induction of postoperative corneal HOAs. Efforts to optimize centration are critical for improving surgical outcomes in patients with FS-LASIK.

Matched comparison of corneal higher order aberrations induced by SMILE to femtosecond assisted LASIK and to PRK in correcting moderate and high myopia: 3.00mm vs. 6.00mm.

BACKGROUND: The refractive surgeries induce corneal higher order aberrations (C-HOAs). In this study, change of C-HOAs after small-incision lenticule extraction (SMILE) compared to femtosecond assisted laser in situ keratomileusis (femto-LASIK), and to photorefractive keratectomy with mitomycin-C (PRK) under photopic and mesopic conditions. METHODS: In this prospective study, age, gender, and apical corneal thickness (ACT) matched cases with moderate myopia [spherical equivalent (SE) 3.00 to 6.00D) to high myopia (SE > 6.00D)] were enrolled. In addition to visual acuity and refraction, total C-HOA, coma, spherical aberration (SA), and trefoil in the 3- and 6-mm zones were measured before and 3 and 6 months after surgery. RESULTS: Overall, 372 moderate myopia cases (124 eyes of 124 individuals in each surgical group) and 171 high myopia cases (57 eyes of 57 individuals in each surgical group) were enrolled. At baseline, the differences in age, gender, ACT, uncorrected and corrected visual acuity, and SE were not statistically significant between subgroups of surgical methods within each myopia group (all P > 0.05). At 12 months, in the moderate myopia group, there was less increase in 6-mm zone total C-HOA, coma, and SA with SMILE compared to the other groups (all P < 0.05). In the high myopia group, there was greater increase in photopic total C-HOA and trefoil and less increase in mesopic SA with SMILE (all P < 0.05). CONCLUSIONS: In correction of moderate myopia, SMILE has better results in mesopic condition. In high myopia correction, femto-LASIK and PRK have better results in photopic and SMILE in mesopic condition.

Comparison between aberration-free transepithelial photorefractive keratectomy and small incision lenticule extraction for correction of myopia and myopic astigmatism.

PURPOSE: To evaluate the clinical outcomes of small incision lenticule extraction (SMILE) and aberration-free transepithelial photorefractive keratectomy (AF t-PRK) in patients with low to moderate myopic astigmatism, including visual acuity, refractive outcomes, astigmatic vector analysis and corneal aberrometric changes. METHOD: This retrospective comparative case series study involved 110 right eyes of 110 patients who underwent either SMILE (55 eyes) or AF t-PRK (55 eyes). Visual acuity, manifest refractive error and corneal higher-order aberrations (HOAs) were measured and analyzed at baseline, 1 month and 3 months after operation. The safety and efficacy indices, and vector parameters were also compared. RESULT: 1 month postoperatively, the mean uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA) and spherical equivalent refraction (SE) were better after SMILE than AF t-PRK (logMAR UDVA, - 0.03 ± 0.07 and - 0.006 ± 0.07, P = 0.050; logMAR CDVA, - 0.06 ± 0.07 and - 0.03 ± 0.07, P = 0.043; SE, - 0.04 ± 0.25 and 0.15 ± 0.26, P < 0.001). However, these parameters were comparable between the groups at 3 months after surgery. Residual astigmatism ≤ 0.25 diopters was observed in 74.5% and 90.9% (P = 0.023) of the eyes at one month and in 87.3% and 85.5% (P = 0.781) of the eyes at 3 months after SMILE and AF t-PRK, respectively. There were no significant differences between the groups in any of the vector parameters at 1 month or 3 months after surgery. Coma and total HOAs after SMILE were significantly higher than AF t-PRK (1 month coma, 0.49 ± 0.23 and 0.29 ± 0.15, P < 0.001; 1 month total RMS HOAs, 0.65 ± 0.20 and 0.54 ± 0.14, P = 0.001; 3 months coma, 0.50 ± 0.22 and 0.30 ± 0.17, P < 0.001; 3 months total RMS HOAs, 0.68 ± 0.20 and 0.55 ± 0.17, P < 0.001). CONCLUSION: In this study, both SMILE and AF t-PRK were effective and comparable for correction of low to moderate myopic astigmatism. AF t-PRK group induced less coma and total HOAs than SMILE.

The impact of corneal higher-order aberrations on dynamic visual acuity post cataract surgery.

Purpose: To explore the influence of corneal higher-order aberrations (HOAs) on dynamic visual acuity (DVA) post cataract surgery. Methods: A total of 27 patients with 45 eyes following cataract surgery were included in this study. The postoperative monocular object-moving DVA at the velocity of 20, 40, and 80 degrees per second (dps) were examined at 1 month. The total corneal HOAs were measured with Scheimpflug-based corneal topography. The correlation between postoperative DVA and HOAs was analyzed. Results: Significant difference was shown among DVA at different velocities (P < 0.001). The 20 dps DVA was significantly better than 40 (P < 0.001) and 80 (P < 0.001) dps DVA. No significant difference was observed between 40 and 80 dps DVA (P = 0.420). The vertical coma and the root mean square (RMS) of coma (RMScoma) were statistically correlated with 80 dps DVA (P < 0.05). The vertical trefoil, RMStrefoil and total RMSHOA were statistically correlated with 40 and 80 dps DVA (P < 0.05). The spherical aberration was not significantly associated with postoperative DVA (P > 0.05 for all velocites). The multivariate linear regression model revealed that age was a significant influential factor for 20 dps DVA (P = 0.002), and RMStrefoil (4 mm) and age were significantly associated with 40 and 80 dps DVA (P ≤ 0.01). Conclusion: The research demonstrated that larger corneal HOAs, especially coma and trefoil aberrations were significantly associated with worse high-speed DVA, but not spherical aberration post cataract surgery.

Efficacy of small back optic zone design on myopia control for corneal refractive therapy (CRT): a one-year prospective cohort study.

BACKGROUND: To investigate the control effect on the axial length elongation using corneal refractive therapy (CRT) with different optical zone diameters (BOZDs). We also sought to compare the difference in higher-order aberrations (HOAs), treatment zone (TZ) size and Zernike defocus coefficient with different BOZDs and seek the optimal parameter for predicting axial elongation. METHODS: This prospective cohort study included 7- to 14-year-olds fitted with orthokeratology (ortho-K) lenses of 5-mm (5-mm group) or 6-mm BOZD (6-mm group). Axial length (AL), corneal topography, HOAs and Zernike defocus coefficient were obtained at baseline, and 1, 3, 6, 9 and 12 months follow-up visits. Multivariate regression analyses were used to explore the association between AL change and ocular biometric parameters. Receiver operating characteristic (ROC) curve analysis was used to determine the best diagnostic value for AL change in ocular biometric parameters. RESULTS: In total, 301 participants completed the one-year follow-up. The mean AL change in the 5-mm group (0.13 ± 0.18 mm) was less than that in the 6-mm group (0.27 ± 0.15 mm) at the 12 months visit. The TZ size and decentration were smaller, while the Zernike defocus coefficient and HOAs were higher in the 5-mm group (all P < 0.05). Older age and smaller TZ size were protective factors against AL elongation in multiple regression. In predicting AL elongation, TZ diameter yielded an area under the ROC curve of 0.684 with a cut-off value of 3.82 mm. CONCLUSION: The 5-mm group showed 0.14 mm (51.8%) less axial elongation than the 6-mm group. The 5-mm BOZD produced a smaller TZ size, higher Zernike defocus coefficient and higher HOA after reshaping of the cornea. TZ size was the best predictor of AL elongation. TZ diameter less than 3.82 mm may lead to AL elongation less than 0.2 mm in one year.

The effect of back optic zone diameter on relative corneal refractive power distribution and corneal higher-order aberrations in orthokeratology.

PURPOSE: To compare axial elongation, relative corneal refractive power (RCRP) distribution within the pupillary diameter, and corneal higher-order aberrations (HOAs) in myopic children wearing orthokeratology (ortho-k) lenses with different back optic zone diameters (BOZD). METHODS: Children aged 8-11 years were fitted with 5.0 or 6.2 mm-BOZD ortho-k lenses (groups A and B, respectively). Axial length (AL) and corneal topography were measured at baseline and during the annual visit. RCRP and corneal HOAs were compared between the two groups after one-year treatment. Multivariate linear regression analysis was performed to determine the association between AL elongation and RCRP parameters, corneal HOAs, and other variables between the groups. RESULTS: After one-year treatment, axial elongation was slower in group A than in group B, with a difference of 0.15 mm. Children in group A showed smaller treatment zone size, smaller 3/4X value (describing the distance from the apex RCRP profile rising to its three-quarter-peak level), greater RCRP sum value within the pupillary area, and higher increases in corneal total HOAs and horizontal coma (Z31). AL elongation was significantly correlated with baseline age, baseline spherical equivalent refraction (SER), treatment zone size, and 3/4X value. CONCLUSIONS: Ortho-k lenses designed with smaller BOZD increased myopia control efficacy, induced a steeper distribution of the RCRP profile within the pupillary diameter, and induced greater increases in corneal total HOAs and horizontal coma (Z31). Lens-induced RCRP profile within pupillary diameter, rising to its three-quarter-peak level at a smaller distance, may show a better myopia control effect.

Corneal aberrations andanisometropia in children.

CLINICAL RELEVANCE: Children with anisometropia have different refractive errors in each eye. Studies reported similar ocular higher-order aberrations (HOAs) in each eye within anisometropia. It is unclear whether binocular corneal HOAs within anisometropia are likewise similar. This study compared interocular differences in corneal HOAs among children with anisometropia, and explored correlations between corneal HOAs and anisometropia. BACKGROUND: This study aimed to compare interocular differences in corneal aberrations in children with low and high anisometropia and to determine correlations between the size of interocular differences in corneal HOAs and the degree of anisometropia. METHODS: This was a retrospective, self-controlled study: 69 children with myopic anisometropia were divided into a high anisometropia group (34 children, interocular difference in spherical equivalent refraction ≧2D) and a low anisometropia group (35 children, 2D >interocular difference in spherical equivalent refraction ≧1D). Binocular corneal aberrations were measured using Sirius combined corneal topographer and tomographer. Paired t-tests, Wilcoxon rank sum tests, and Spearman correlation analyses were used in the current study. RESULTS: For the low anisometropia group, there were no statistically significant interocular differences in corneal HOAs (P>0.05). For the high anisometropia group, higher myopic eyes had lower coma in 3mm diameter than those of the contralateral eyes (in the total cornea and the anterior corneal surface; P<0.05). No interocular difference was found in corneal total higher-order aberration and spherical aberration in the high anisometropia group (P>0.05). Among all 69 children with anisometropia, interocular differences in coma were not correlated with the degree of anisometropia (P>0.05). CONCLUSION: For children with high anisometropia, higher myopic eyes had lower coma than those of the contralateral eyes. However, no obvious correlation was found between interocular differences in coma and the degree of anisometropia.

Evaluation of corneal higher order aberrations in normal topographic patterns.

PURPOSE: This study reports the characteristics of corneal higher order aberrations (HOAs) in eyes with normal topographic pattern using the Pentacam scheimpflug system. METHODS: In this prospective, observational, comparative study, 165 eyes of 97 patients separated into five groups based on corneal topographic patterns were enrolled. All eyes received a comprehensive ophthalmologic examination including corneal tomographic analysis with the Pentacam system. Keratometry, corneal cylinder, and corneal aberrometric data were recorded and analyzed. Root mean square values (RMS) were calculated for corneal HOAs up to the 6th order, total coma, total trefoil, total spherical aberration, total tetrafoil, and higher order astigmatism. Evaluation of these data to discriminate between the five groups was assessed using the analysis of variance test by Generalized Estimation Equation Linear Model. RESULTS: Corneal HOAs were found to be significantly higher for Asymmetric Bow Tie and Irregular groups than other groups (p = <0.001). RMS of total coma aberration ([Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text]) were significantly greater in the Asymmetric Bow Tie pattern than others, and RMS of total Spherical aberration ([Formula: see text], [Formula: see text]) was significantly higher in the Irregular pattern than other groups (p = <0.001). The results of our study demonstrate that a tendency toward significant higher values of trefoil, tetrafoil, and higher order astigmatism in Irregular pattern (all p < 0.05). Significantly higher amounts of 3rd order RMS in Asymmetric Bow Tie group and 4th to 6th order RMS in Irregular pattern group were other outcomes of our study (p = <0.001). CONCLUSIONS: Based on results in this study, there were a good correlation between corneal topographic pattern and corneal HOAs in normal eyes. These results indicate that the corneal HOAs values are largely determined by the topographic patterns. A larger sample size would perhaps have been beneficial to yield in more accurate outcomes.

Effects of SMILE and FS-LASIK on early postoperative corneal higher order aberrations in patients with high myopia / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To study the effects of small-incision lenticule extraction(SMILE)and femtosecond laser-assisted excimer laser <i>in situ</i> keratomileusis(FS-LASIK)on early postoperative corneal higher order aberrations(HOAs)and visual quality in patients with high myopia. <p>METHODS:Totally 102 patients(204 eyes)with high myopia who underwent corneal refractive surgery between August 2018 and August 2020 in the hospital were selected as study subjects for the prospective study, and they were randomly divided into SMILE group(51 cases, 102 eyes)and FS-LASIK group(51 cases, 102 eyes). The postoperative visual acuity, corneal HOAs and objective visual quality were compared between the two groups, and the correlation between corneal HOAs and objective visual quality was analyzed. <p>RESULTS: At 1mo after surgery, the spherical equivalent degrees in SMILE group and FS-LASIK group were significantly reduced(<i>P</i><0.05), and there was no statistically significant difference in the proportion of patients with postoperative uncorrected visual acuity≥preoperative best corrected visual acuity between the two groups(95.1% <i>vs</i> 92.2%, <i>P</i>>0.05). The corneal HOAs in the two groups were significantly increased(<i>P</i><0.05), and the overall spherical aberration(SA), trefoil and higher HOAs in SMILE group were lower than those in FS-LASIK group(all <i>P</i><0.05). The objective scattering index(OSI)was significantly increased in the two groups while the MTF cutoff frequency(MTF_cutoff), Strehl Ratio(SR)and contrast visual acuity(VA100%, VA20%, VA9%)were significantly decreased(all <i>P</i><0.05). The OSI of SMILE group was lower than that of FS-LASIK group while MTF_cutoff and VA9% were higher than those of FS-LASIK group(all <i>P</i><0.05). The corneal HOAs in patients with high myopia were negatively correlated with MTF_cutoff and were positively correlated with OSI(<i>P</i><0.05).<p>CONCLUSION:Both SMILE and FS-LASIK can effectively correct high myopia, and SMILE has a smaller increase in early postoperative corneal HOAs, and it is of great significance to relieve visual quality impairment.

Effect of 2.8mm clear corneal incisions in phacoemulsification on surgically induced corneal higher-order aberrations / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To compare the changes of surgically induced corneal higher order aberrations after phacoemulsification with 2.8mm clear corneal incisions at different sites.METHODS:The clinical data of 100 cases (100 eyes) of patients with cataract treated by phacoemulsification with 2.8mm clear corneal incision in our hospital from March 2015 to April 2016 were analyzed retrospectively.According to the site of incision,they were divided into Group A (temporal clear corneal incision,n =55) and Group B (upper clear corneal incision,n=45).Changes of the best corrected visual acuity (BCVA),surgically induced astigmatism (SIA) and corneal topography were compared between the two groups before surgery,at 1d,1wk,1 and 3mo after surgery.The corneal wavefront aberrations were measured by wavefront aberration analyzer,and the changes of higher-order aberrations in corneal 6mm range were recorded.RESULTS:The BCVA of two groups decreased at 1d,1wk,1 and 3mo after surgery (P＜0.05),and the BCVA of Group A at 1d,1wk,and 1mo after surgery was lower than that of Group B (P＜0.05).SIA of the two groups decreased at 1wk,1 and 3mo after surgery (P＜0.05),and the SIA of Group A at different time points after surgery were lower than those of Group B (P＜0.05).The surface asymmetry index (SAI) and the surface rule index (SRI) of the two groups increased at 1 d after surgery,and were gradually decreased at 1wk,1 and 3mo after surgery.The SRI and SAI in Group A were lower than those in Group B at 1d and 1wk after surgery (P＜ 0.05).The total corneal higher-order aberrations (tHOAs) and four-order spherical aberration (SA)showed significant differences between the two groups at 3mo after surgery (P＜0.05).CONCLUSION:The application of 2.8mm temporal clear corneal incision in phacoemulsification can promote the recovery of visual acuity,reduce the effect of surgery on corneal shape,and reduce corneal higher-order aberrations.

Comparison of Corneal Higher-Order Aberrations Measured with Two Instruments Using Scheimpflug Camera System

PURPOSE: To compare the corneal higher-order aberrations (HOAs) of normal young subjects using Galilei(TM) G4 (Zeimer, Port, Switzerland) and Pentacam(R) (Oculus Inc., Wetzlar, Germany). METHODS: Corneal HOAs were measured using Galilei(TM) G4 and Pentacam(R) in 41 healthy individuals (41 eyes). Intraclass correlation coefficients (ICCs) were obtained to evaluate the repeatability of the 2 devices. Differences in HOAs between the 2 instruments were analyzed with a paired t-test and correlations evaluated. RESULTS: All ICCs measured using Galilei(TM) G4 and Pentacam(R) showed more than moderate repeatability (>0.81) except trefoil, tetrafoil, 4th and 5th HOAs. When comparing the measurements obtained with Galilei(TM) G4 and Pentacam(R), total HOAs, spherical aberration (SA), secondary astigmatism and 5th total HOAs were statistically significantly different between the 2 device (all p < or = 0.001). In addition, Galilei(TM) G4 and Pentacam(R) showed discrepancy among all corneal HOAs items. Although the total corneal HOAs and the SA were significantly correlated, other HOA measurements generally exhibited a low correlation. CONCLUSIONS: Corneal HOAs obtained by the 2 instruments cannot be used interchangeably due to their differences and discrepancy although corneal HOAs measured using Galilei(TM) G4 and Pentacam(R) showed relatively high repeatability.

Relationship between Dry Eye Parameters and Anterior Corneal Higher-Order Aberrations Measured by Two Different Instruments

PURPOSE: To compare the corneal first surface higher-order aberrations (HOAs) of normal subjects and patients with dry eye using KR-1W(R) (Topcon Corp., Tokyo, Japan) and Pentacam(R) HR (Oculus Inc., Dutenhofen, Germany). We analyzed the relationship between the aberrations and the diagnostic parameters of dry eye. METHODS: We evaluated anterior corneal HOAs in 71 normal eyes and 71 dry eyes using KR-1W(R) and Pentacam(R). Dry eye patients were examined for fluorescein staining, tear break-up time (TBUT), and Schirmer I test. Ocular Surface Disease Index (OSDI) was used for assessment of subjective symptoms in dry eye patients. RESULTS: HOAs measured by both instruments were greater in the dry eye group than in the control group, although HOAs using KR-1W(R) only achieved statistical significance. The anterior corneal HOAs measured by the 2 instruments were significantly correlated with superficial punctate keratitis. Moreover, TBUT and the Shirmer I test negatively correlated, and OSDI positively correlated, with anterior corneal HOAs. CONCLUSIONS: The HOAs in patients with dry eye were significantly different from controls and tended to increase with disease severity. KR-1W(R) might be more useful than Pentacam(R) to detect tear film instabilities.

Surgically Induced Astigmatism and Corneal Higher Order Aberrations in Microcoaxial and Conventional Cataract Surgery

PURPOSE: To compare surgically induced astigmatism (SIA) and some corneal higher order aberrations in patients who underwent microcoaxial cataract surgery (MCCS) or conventional cataract surgery. METHODS: A prospective randomized study included 60 eyes of 55 patients. Thirty eyes received MCCS using a 2.2mm clear corneal incision (group 1), and 30 eyes received conventional cataract surgery using a 2.8 mm clear corneal incision (group 2). SIA and corneal higher order aberrations were measured with a Keratometer (Humphrey, Zeiss) and i-Trace (Tracey Technologies) preoperatively, and at 1 and 3 months after cataract surgery. SIA was analyzed vectorially using the Alpins method. RESULTS: There was no significant difference in preoperative UCVA or BCVA between the two groups. At 1 month and 3 months after surgery, SIA in group 1 was less than that in group 2, but this difference was not significant. There was no statistically significant difference in postoperative change of corneal higher order aberrations in each group at 1 month or 3 months after surgery, and there was no statistically significant difference in corneal higher order aberrations between the two groups preoperatively, at 1 month, or 3 months after surgery. CONCLUSIONS: There was no significant difference in SIA and corneal higher order aberrations between the two groups.