Anterior Corneal Higher-order Aberrations Research Articles

Rate of fractional change in corneal tomography parameters in keratoconus using a combination of predictive parameters

BackgroundTo compare the rate of fractional change for multiple corneal tomographic factors in progressive keratoconus (KC).MethodsIn this retrospective case series, 40 eyes (40 patients) with progressive KC (increase in central keratometry of 1.00 D or maximum keratometry of 1.50 D on two visits at least six months apart) were included. Cases with previous history of ocular surgery, poor scans, corneal scars, severe dry eyes, post-excimer ectasia, pellucid marginal degeneration were excluded. Medical records, corneal tomography and anterior corneal wavefront (8 mm) (Scheimpflug tomography, Pentacam, Oculus, Germany) were analyzed. Rate of fractional change (Rx = (x1 − x0)/(|x0|tm)); where, x1 = value at follow-up, x0 = value at initial visit and tm = time in months, was measured.ResultsThe mean age of the patients was 30.0 ± 8.4 years. The mean follow-up duration was 8.9 ± 4.2 months. Coma (0.076 ± 1.4) had the largest rate of fractional change (P = 1.7 × 10−14, Kruskal–Wallis test). The rate of fractional change was higher for aberrometric parameters (anterior corneal higher-order aberrations root mean square and anterior coma) compared to pachymetric and keratometric parameters (P values ranging from 1.4 × 10−4 to 7.4 × 10−10, Mann–Whitney test, effect size ranging from 0.4–0.7). The rate of fractional change was comparable between pachymetric and keratometric factors (P > 0.05 for all comparisons, Mann–Whitney test).ConclusionsAnterior corneal wavefront, especially anterior coma, were noted to have higher rate of fractional change compared to single point keratometric and pachymetric indices in progressive KC. This information can be used for decision-making when monitoring patients with KC.

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

PurposeTo compare the root mean square (RMS) of anterior corneal higher-order aberrations (HOAs) in ametropic and emmetropic eyes.MethodsThis 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.ResultsRMS 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).ConclusionThe 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.

Anterior Corneal High-order Aberrations in Fuchs' Endothelial Corneal Dystrophy Classified by Scheimpflug Tomography.

Visual acuity may be limited after endothelial keratoplasty in Fuchs' endothelial corneal dystrophy. This may be due to increased anterior high-order aberrations that persist after endothelial keratoplasty. It is not clear at what stage these aberrations begin. We aimed to evaluate how subclinical corneal edema affects anterior corneal high-order aberrations. We aimed to evaluate anterior corneal high-order aberrations according to the presence of subclinical corneal edema in Fuchs' endothelial corneal dystrophy using Scheimpflug topography. All the patients underwent corneal topography (Sirius Scheimpflug-Placido disc camera; CSO Ophthalmic, Scandicci, Italy). Fifty-two eyes of 31 patients with Fuchs' endothelial corneal dystrophy and 52 eyes of 35 patients without corneal problems were included. In addition, patients with Fuchs' endothelial corneal dystrophy were divided into two groups according to subclinical corneal edema as with Fuchs' endothelial corneal dystrophy-edema and Fuchs' endothelial corneal dystrophy-nonedema. Subclinical corneal edema was defined based on the presence of at least two of three findings of the loss of regular isopachs, displacement of the thinnest point of the cornea, and posterior depression. High-order aberrations were expressed as Zernike polynomials in the 4- and 6-mm optical zone. We found that subclinical corneal edema in Fuchs' endothelial corneal dystrophy caused a larger 4-mm trefoil II and a smaller 6-mm spherical aberration II measurements than the nonedema group. The 6-mm total high-order aberrations, 6-mm coma aberration, and 4- and 6-mm trefoil II aberration measurements were larger, and the 6-mm spherical aberration II was smaller in Fuchs' endothelial corneal dystrophy patients with edema compared with the healthy eyes. The presence of subclinical corneal edema in Fuchs' endothelial corneal dystrophy results in larger 4-mm trefoil II and smaller 6-mm spherical aberration II measurements. More patients with intermediate values are needed to evaluate the effect of these aberrations on visual acuity.

Corneal higher-order aberration changes after accelerated cross-linking for keratoconus

AimTo evaluate changes in corneal higher-order aberrations (HOAs) following epithelium-off accelerated corneal cross-linking (A-CXL) and to explore the impact on visual acuity.MethodsIn this retrospective case series, 32 eyes of 24 patients with keratoconus (KC) underwent A-CXL. Treatment was delivered at 10 mW/cm2 for 9 min with a total dose of 5.4 J/cm2. The following anterior corneal HOAs: total corneal HOAs, trefoil, secondary trefoil, coma, secondary coma, secondary astigmatism and spherical aberrations were analysed using the Scheimpflug-Placido Sirius (CSO, Italy) corneal topographer at baseline and 12 months following treatment. Multivariate analysis was used to evaluate the independent effect of HOA subtypes on changes in uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA).ResultsAt one year post CXL, UDVA and CDVA were significantly improved, -0.13 ± 0.19 LogMAR (P = 0.0005) and -0.08 ± .0.11 LogMAR (P = 0.0003), respectively. The mean preoperative trefoil, secondary trefoil, secondary coma and secondary astigmatism were 0.95 ± 0.46; µm, 0.20 ± 0.11; µm, 0.29 ± 0.19; µm and 0.42 ± 0.17 µm, respectively. At one year, the mean values decreased significantly to 0.77 ± 0.47 µm, 0.15 ± 0.11 µm, 0.25 ± 0.18 µm and 0.34 ± 0.18 µm, respectively (P < 0.05, for all). No independent relationship between any HOA changes and change in UDVA was observed. A reduction in secondary coma aberration was associated with a change in CDVA (95% CI 0.01–1.34, P = 0.048; β = 0.67).ConclusionA 9-min protocol of Accelerated corneal cross-linking is an effective treatment in improving corneal HOAs at 12 months follow up, in eyes with progressive keratoconus at one year follow-up. A change in secondary coma had a statistically significant and independent effect on CDVA.

Erratum for "The Relationship Between Preoperative Anterior Corneal Higher Order Aberrations and Topography-Guided Excimer Ablation Depth".

Erratum for "The Relationship Between Preoperative Anterior Corneal Higher Order Aberrations and Topography-Guided Excimer Ablation Depth".

Discrepancies between total and anterior corneal high-order aberrations at measured and theoretical pupil diameter

Discrepancies between total and anterior corneal high-order aberrations at measured and theoretical pupil diameter

Efficiency and Safety of Scleral Lenses in Rehabilitation of Refractive Errors and High Order Aberrations After Penetrating Keratoplasty.

Visual rehabilitation after penetrating keratoplasty (PK) has difficulties linked to the high spherical and/or cylindric refractive errors with high order aberrations (HOAs) based on the ocular surface irregularities. We aimed to present the scleral contact lens (SCL)-induced complications and improvements in refractive errors and HOA with SCL fitting in post-PK patients. In this prospective study, 38 eyes of 35 patients who underwent PK and using SCLs were included. Uncorrected visual acuity, best-corrected visual acuity (BCVA), spherical equivalence, manifest astigmatism (Cyl), keratometry, and wavefront analyses of HOAs with corneal topography of all patients were measured before SCL and after 8 hrs of SCL wearing-on. The endothelial cellular density (ECD) changes at 6 months were also recorded. Any complications related to SCL were noted. All patients showed an improvement in visual acuity with SCL. Uncorrected visual acuity before SCL fitting was 1.15±0.26 log of minimal angle of resolution (logMAR) and BCVA was 0.84±0.24 logMAR. The contact lens-corrected visual acuity decreased to 0.13±0.09 logMAR. Spherical equivalence, Cyl, and keratometry parameters decreased significantly with SCL. The anterior corneal HOAs, coma, and astigmatism coefficients decreased significantly. Conjunctival prolapse (in one eye) and graft rejection episode (in two eyes) were observed during follow-up time (14.25±1.3 months) and they restarted to use SCLs after treatment. The ECD decrease was similar with those who not using SCLs after PK in the literature. Our results indicate that scleral lenses may be a safe and effective option for the treatment of corneal astigmatism and HOAs associated with PK.

The Relationship Between Preoperative Anterior Corneal Higher Order Aberrations and Topography-Guided Excimer Ablation Depth.

To determine the correlation and relative contribution of preoperative anterior corneal Zernike coefficients to higher order aberration ablation depth (HOA-AD) with topography-guided excimer laser correction. Retrospective study of 46,271 consecutive preoperative virgin eyes. Anterior corneal Zernike coefficients (C6 to C27) and HOA-AD data on a 6.5-mm optical zone were analyzed from the Contoura (Alcon Laboratories, Inc) treatment software. Pearson correlations were performed to assess the relationship between Zernike coefficients and HOA-AD. A strong direct relationship was found between the total root mean square (RMS) anterior corneal HOA and HOA-AD (R = 0.84; P < .001). The 3rd order HOAs (C6 to C9) accounted for most of the HOA-AD (R = 0.83; P < .001). Zernike orders 4, 5, and 6 had significantly weaker correlations (4th order: R = 0.30; 5th order: R = 0.38; 6th order: R = 0.29). Vertical coma was the individual HOA with the highest correlation (R = 0.59; P < .001). Combining vertical and horizontal coma as total RMS coma increased the correlation significantly (R = 0.76; P < .001). The average HOA-AD increased by 1.5 µm for each additional 0.1-µm increment of total RMS coma. Anterior corneal Zernike coefficients directly and strongly correlate to the HOA-AD, with anterior corneal coma having the greatest contribution to HOA-AD. [J Refract Surg. 2020;36(8):506-510.].

Inter-Ocular Asymmetry in Anterior Corneal Aberrations Using Placido Disk-Based Topography.

ObjectiveInter-ocular asymmetry in anterior corneal high-order aberrations has previously not been investigated. This study aims to investigate the normal range of inter-ocular asymmetry in corneal high-order aberrations (HOAs) using a Placido disk-based corneal topographer to explore the relationship between the HOA parameters of the anterior corneal for each eye individually and the refractive error.Patients and MethodsA total of 257 subjects (98 males and 159 females) were participated, with an age range of 6 to 81 years (average of 40.2 ±17.53). Participants were divided into three groups: myopia (spherical equivalent (SEQ) of refraction ≥−0.50 D), hypermetropia (SEQ ≥+0.50 D), and emmetropia. For all patients, high-order aberrations were measured using a corneal topographer (CA.200TM; Topcon). Inter-ocular asymmetry was represented by RMS (root mean square) for three, five, and seven mm as pupil entry; aberrations for five mm pupil (vertical and oblique trefoil, vertical and horizontal comma, and primary spherical aberration) were recorded using the instrument’s built-in software.ResultsHypermetropes exhibit the highest inter-ocular asymmetry of all RMS values, mostly in spherical aberrations, and higher-order trefoil values. Oblique trefoil aberrations had the highest interocular asymmetry in the myopic groups. The interocular asymmetry in horizontal coma values was the highest in emmetropes and the lowest in hypermetropes.ConclusionTo our knowledge, this is the first observational study of inter-ocular differences in high-order aberrations of the anterior corneal surface of the human eye. This study’s results could be used to establish normal values of inter-ocular asymmetry of HOAs of the anterior cornea. The use of such normal values should be investigated further to serve as a guideline for clinicians when establishing the best management route for the patient’s refractive error.

Corneal higher-order aberrations after crosslinking and intrastromal corneal ring segments for keratoconus.

To assess anterior corneal higher-order aberrations (HOAs) after corneal crosslinking (CXL) and intrastromal corneal ring segments (Intacs) used adjunctively. Cornea and refractive surgery practice. Prospective, randomized clinical trial. One hundred fifty-eight eyes of 150 patients were randomized into 2 groups: concurrent, Intacs and CXL during the same session (n = 81), or sequential, Intacs followed by CXL 3 months later (n = 77). Outcomes included changes in total, coma, trefoil, and spherical anterior corneal HOA 6 months after Intacs/CXL. The change in anterior corneal HOAs was correlated with the change in uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and topography indices of maximum keratometry (Kmax), maximum flattening keratometry (Kmaxflat), and inferior-superior (I-S) ratio. A subjective visual function questionnaire was also analyzed. UDVA, CDVA, Kmax, I-S, and Kmaxflat all improved 6 months after treatment (UDVA = -0.22 ± 0.34, P < .001; CDVA = -0.13 ± 0.24, P < .001; Kmax = -3.1 ± 3.0D, P < .001; I-S = -4.2 ± 5.0 diopters [D], P < .001; Kmaxflat = -7.9 ± 4.0 D, P < .001). Total anterior corneal HOA, vertical coma, and horizontal coma anterior corneal HOAs significantly improved by -1.05 ± 0.93 μm (P < .001), -1.53 ± 1.18 μm (P < .001), and -0.35 ± 0.57 μm (P < .001), respectively. Spherical anterior corneal HOAs increased by 0.24 ± 0.70 μm (P < .001) at 6 months after Intacs/CXL. The change in trefoil was not statistically significant (Ptrefoil0 = .06, Ptrefoil30 = .2). There were no significant differences between the changes in anterior corneal HOAs in the sequential and same-day Intacs/CXL groups. The change in total anterior corneal HOAs was correlated with Kmax, Kmaxflat, and the I-S ratio. There was no correlation between the change in anterior corneal HOAs and the change in visual acuity or visual function survey responses. Total, horizontal coma, and vertical coma anterior corneal HOAs improved after Intacs/CXL. Spherical anterior corneal HOAs increased postoperatively, and there was no change in trefoil. Improvement of anterior corneal HOAs did not correlate with visual acuity improvement or subjective visual satisfaction outcomes.

Classification of Keratoconus Based on Anterior Corneal High-order Aberrations: A Cross-validation Study.

Placido disc-based videokeratography is one of the most extensively used methods for corneal topographic assessments in keratoconus. Anterior corneal wavefront analysis has been demonstrated to be an effective tool to manage keratoconus eyes. However, currently, there is no clinically adequate classification system for keratoconus. The aim of this study was to analyze the usefulness of anterior corneal high-order aberrations in keratoconus classification provided by Placido disc-based videokeratography conducting a cross-validation analysis. Corneal topography of 70 normal and 77 keratoconic eyes (divided according to the Amsler-Krumeich classification [n = 21, stage 1; n = 30, stage 2; and n = 26, stage 3]) was assessed using Placido disc-based videokeratography (Oculus Keratograph [Oculus Optikgeräte GmbH, Wetzlar, Germany]). Receiver operating characteristic curve analysis was used to compare the mean values of coma, trefoil, tetrafoil, secondary astigmatism, spherical aberration, and coma-like, third-, and fourth-order root mean square (RMS) to calculate cutoff values, sensitivity, and specificity to discriminate between normal and stage 1 keratoconus eyes and between each keratoconus stage after cross-validation analysis. All wavefront aberrations were significantly different between the normal and keratoconus groups (P ≤ .01). The coma and third-order RMS values (cutoff values, 0.367 and 0.359 μm, respectively) provide better sensitivity (99 and 100%, respectively) and specificity (100%) to discriminate keratoconus (stage 1) from healthy eyes compared with trefoil, tetrafoil, secondary astigmatism, spherical aberration, and coma-like and fourth-order RMS values (sensitivity >84% and specificity >57%). The coma and third-order RMS values showed the highest specificity (100%) and great sensitivity (90 and 87%, respectively) to differentiate between stages 1 and 2 and good sensitivity (97 and 100%) and specificity (81 and 88%) to differentiate between stages 2 and 3. Anterior corneal high-order aberrations, specifically coma and third-order RMS, could be useful in keratoconus diagnosis and topographical classification. These new cutoff values could improve different stages of keratoconus eyes discrimination.

Impact of different clear corneal incision sizes on anterior corneal aberration for cataract surgery.

To investigate the impact of different sizes of steep meridian clear corneal incisions for phacoemul sification on anterior corneal higher-order aberrations. Medical records of patients who underwent 2.2-mm coaxial micro-incision cataract surgery or 2.75-mm coaxial small-incision cataract surgery were retrospectively reviewed. Only patients with preexisting anterior corneal astigmatism <2.00 diopters (D) and ≥0.50 D who underwent a steep meridian clear corneal incision were included. Primary outcomes were 3rd- to 6th-order anterior corneal higher-order aberrations with an 8-mm pupil. Anterior corneal astigmatism and effective phaco time were evaluated as secondary outcomes. Preoperative and 3-month postoperative outcomes were evaluated. Anterior corneal astigmatism significantly decreased after both procedures; however, there was no significant difference found in surgically induced anterior corneal astigmatism between the two procedures (p=0.146). Although the total higher-order aberrations did not significantly change after both procedures, the group comparison showed a significant difference in surgically induced total higher-order aberrations (a decrease of 0.337 ± 1.156 mm in 2.2-mm coaxial micro-incision cataract surgery and an increase of 0.106 ± 0.521 mm in 2.75-mm coaxial small-incision cataract surgery, p=0.046). Spherical aberrations significantly decreased after 2.2-mm coaxial micro-incision cataract surgery (p=0.001), whereas they did not change significantly after 2.75-mm coaxial small-incision cataract surgery (p=0.564). Coma did not significantly change after either of the procedures. Trefoil did not significantly change after 2.2-mm coaxial micro-incision cataract surgery (p=0.361), whereas it significantly increased after 2.75-mm coaxial small-incision cataract surgery (p<0.001). There was no significant difference shown in effective phaco time between the procedures. A significantly positive correlation was shown between surgically induced anterior corneal astigmatism and coma in 2.75-mm coaxial small-incision cataract surgery (r=0.387, p=0.006). There was no significant correlation found between any surgically induced higher-order aberration changes and effective phaco time. The results showed that 2.2-mm coaxial micro-incision cataract surgery and 2.75-mm coaxial small-incision cataract surgery did not significantly degrade the total higher-order aberrations of the anterior cornea. However, the surgically induced changes in total higher-order aberration showed a significant difference between the two procedures, with a slight reduction after 2.2-mm coaxial micro-incision cataract surgery and a slight increase after 2.75-mm coaxial small-incision cataract surgery. Phaco time and power used during surgery had no impact on corneal aberrations.

Wavefront properties of the anterior and posterior corneal surface after transepithelial photorefractive keratectomy in myopia.

The present study aimed to evaluate the changes of corneal higher-order aberrations (HOAs) after transepithelial photorefractive keratectomy (TransPRK) in patients with myopia. A total of 80 eyes of 80 patients with myopia with or without astigmatism were evaluated. Prior to and 1 year after the surgery, uncorrected and corrected distance visual acuity in logMAR were assessed. Wavefront aberrations on the anterior surface of the cornea, as well as the posterior and total cornea, were measured via Pentacam. The HOA of the anterior surface and total values of spherical and coma aberrations increased significantly (P<0.001). However, HOAs of the anterior surface, and posterior and total values of the trefoil were not significantly changed (P=0.442, 0.805 and 0.936, respectively). A significant correlation of the pre-operative mean spherical equivalent refraction (MSER), astigmatism and central corneal ablation depth (CCAD) with the changes in coma aberration (r=0.268, P=0.016; r=0.260, P=0.020; r=0.323, P=0.004, respectively) and HOA (r=0.554, P<0.001; r=0.312, P=0.005; r=0.583, P<0.001, respectively) of the anterior surface of the cornea was determined. Furthermore, a significant correlation of the pre-operative MSER and CCAD with the changes in spherical aberration of the anterior corneal surface (r=0.462, P<0.001; r=0.510, P<0.001, respectively) was obtained. In conclusion, TransPRK offers an effective option for improving visual function in patients with myopia. The anterior corneal HOA, as well as spherical and coma aberrations, were significantly increased post-operatively. The HOA of the posterior cornea was not significantly changed. The change in the trefoil aberration was significantly correlated with pre-operative astigmatism, but the pre- and post-operative values were not significantly different.

Primary Topography-Guided LASIK: Refractive, Visual, and Subjective Quality of Vision Outcomes for Astigmatism ⩾2.00 Diopters.

To evaluate the outcomes of primary topography-guided laser in situ keratomileusis (LASIK) in eyes with subjective refractive astigmatism of 2.00 diopters (D) or greater. This was a prospective study in consecutive eyes with cylinder of 2.00 D or greater that had LASIK using the Alcon WaveLight EX500 excimer laser and T-CAT/Contoura software (Alcon Laboratories, Inc., Fort Worth, TX). The accuracy, efficacy, safety, cylinder vector analysis, higher order aberrations, and patients' subjective quality of vision were assessed. Eyes with naturally occurring topographic irregular astigmatism were not excluded. The mean cylinder was -2.55 D preoperatively and -0.34 D postoperatively; 81% and 95% of eyes were within ±0.50 and ±0.75 D of intended cylinder after LASIK, respectively. The correction index and index of success were 1.00 and 0.13, respectively. The efficacy and safety indexes were 0.98 and 1.04, respectively. The preoperative corneal topography irregularity index, anterior corneal higher order aberrations, and refractive astigmatism magnitude were mildly correlated to postoperative residual astigmatism. Mean ocular and corneal coma were not increased postoperatively. Patients had significant improvements after LASIK in both subjective uncorrected quality of vision and night vision disturbances compared to spectacle- and contact lens-corrected vision before LASIK. Topography-guided ablation using the Alcon WaveLight EX500 excimer laser and T-CAT/Contoura software results in excellent accuracy, efficacy, and safety, with improved postoperative subjective quality of vision and reduced night vision disturbances in virgin eyes with refractive astigmatism of 2.00 D or greater, including eyes with topographic naturally occurring irregular astigmatism. [J Refract Surg. 2019;35(2):78-86.].

Comparison of topographic indices and corneal higher order aberrations in eyes with an extreme asymmetry of keratoconus with control eyes

Purpose: To compare topographic indices and anterior corneal higher order aberrations (HOAs) of forme fruste keratoconus (KC) (fellow eyes) with clinical KC and control eyes. Setting: Tertiary Eye Hospital, India. Materials and Methods: This study retrospectively reviewed 298 patients with KC. Patients were evaluated with placido-based topographer. KC was diagnosed according to Rabinowitz and McDonnell criteria and clinical sign. Twenty-one patients with clinical KC in one eye (Group A), fellow eye (Group B) with normal topography with no clinical sign, and 21 control eyes (Group C) were included in the study. Topographic indices (keratometry, inferior superior ratio, irregularity, shape factor, and eccentricity) and HOAs (trefoil, coma, spherical aberration, total root mean square [RMS], HOAs RMS of third to seventh order for 6 mm diameter) were obtained. Group B was compared with Groups A and C. Results: The prevalence of an extreme asymmetry of KC in our study population is 7.04% with mean age of 21.98 ± 7.39 years. All topographic indices were higher in Group A compared to Group B (P

Evaluation of interface reflectivity and corneal aberrations following Descemet's stripping automated endothelial keratoplasty.

PURPOSE:This study aims to evaluate visual outcome after Descemet's membrane stripping automated endothelial keratoplasty (DSAEK) and relate to interface and corneal higher-order aberrations (HOAs).MATERIALS AND METHODS:We enrolled 16 eyes of 16 patients (eight males and eight females) in this interventional case series and followed DSAEK operation for about two to 20 months. OCULUS Pentacam, as well as other ophthalmic evaluations in follow-up visits, examined interface reflectivity and HOAs. Statistical relations were analyzed.RESULTS:There was statistically significant correlation between interface reflectivity and best corrected visual acuity (BCVA) (r = 0.56, P = 0.021). Pachymetry (central corneal thickness) and BCVA had a moderate correlation (r = 0.6, P = 0.013). There was no statistically significant correlation between pachymetry and follow-up time (r = −0.36, P = 0.16). Negative correlation between follow-up and interface reflectivity was also not statistically significant (r = −0.24, P = 0.35). Coma had a significant correlation with BCVA in cornea and cornea front maps (r = 0.74, P = 0.009 and r = 0.71, P = 0.013, respectively).CONCLUSION:Significant correlation between interface reflectivity and BSCVA was found, and anterior corneal HOAs are significantly higher than posterior HOAs.

Contralateral eye study of refractive, topographic and aberrometric outcomes after femtosecond assisted MyoRing implantation and DALK for management of keratoconus.

To evaluate the efficacy of femtosecond laser assisted MyoRing intrastromal corneal implant and deep anterior lamellar keratoplasty (DALK) for management of moderate to advanced keratoconus regarding the degree of changes in visual acuity, refraction, corneal asphericity and aberrations. A prospective non comparative interventional case study was conducted in Ophthalmology Department, Ain Shams University Hospital in the period from January 2015 to February 2017. The study included 30 eyes of moderate to advanced keratoconus. MyoRing was implanted in one eye (Group I) and DALK operation was performed in the contralateral eye of the same patient (Group II). Preoperative and 6mo post-operative uncorrected visual acuity (UCVA), corrected distance visual acuity (CDVA), spherical equivalent (SE), corneal and refractive astigmatisms, keratometry and Q-value using topography images were acquired. Quality of vision was assessed in all eyes including total corneal, anterior corneal high order aberrations analysis at 5 mm pupil size and the Strehl ratio of point spread function (PSF) as an objective measure of glare. Mean postoperative UCVA, CDVA, SE, refractive astigmatism, keratometry readings and asphericity were statistically improved compared to preoperative parameters in both groups (P<0.05). Significant reduction of all corneal aberrations following both techniques (P<0.05) was achieved except mean trefoil and mean PSF in Group I (P>0.05). Postoperative corneal aberrations were significantly lower in Group II compared to Group I. A statistically significant negative correlation was found in Group I between the mean change in CDVA (logMAR) and the mean preoperative and mean postoperative total corneal aberrations root mean square (RMS; r=-0.78, P=0.04). Also a statistically significant negative correlation was found between mean preoperative coma RMS and mean post PSF (r=-0.86, P=0.01). In Group II, there was a statistically significant positive correlation between mean change in CDVA (logMAR) and mean change in Kmax (r=0.87, P=0.01) and between mean change in refractive cylinder and mean postoperative PSF (r=0.76, P=0.05). Femtosecond laser assisted MyoRing and DALK are effective in improving visual acuities, refraction, corneal asphericity and aberrations. MyoRing reduced spherical error more than the corneal cylinder. Post operative homogenous corneal surface and good image quality were achieved following both techniques compared to the preoperative state. However, DALK results in better image quality and lower corneal aberrations.

Anterior corneal high-order aberrations in eyes with senile cataract in a Chinese population

Objective: To investigate the distribution of anterior corneal high-order aberrations (HOAs) in Chinese eyes with cataract and their correlations with age and axial length for the choice of aspheric intraocular lens. Methods: Retrospective study. Six hundred twenty-five Chinese patients with cataract[male: 260, female: 365, age: (71.2±8.0) years] were categorized into 4 groups in accordance with their axial lengths. Anterior corneal HOAs in the central 6- mm zone was measured with an iTrace wavefront analyzer. The correlations between axial length, age and total HOAs, spherical aberration, trefoil aberration, and coma aberration were analyzed using Spearman analysis. The differences in total HOAs, spherical aberration, trefoil aberration, and coma aberration among 4 groups were assessed using the Krusal-Wallis H test. Results: Anterior corneal HOAs showed the nonnormal distribution. The median of corneal total HOAs was 0.666 μm (range 0.246 to 4.115 μm). Medians of coma aberration, spherical aberration and trefoil aberration were 0.313 μm (range 0.015 to 1.879 μm), 0.275 μm (range 0.005 to 1.797 μm) and 0.341 μm (range 0.019 to 2.319 μm), respectively. A significant negative correlation was found between axial length and total HOAs, coma aberration, spherical aberration, trefoil aberration (r=-0.230, -0.235, -0.143, -0.153, P<0.05). But no correlation was found between age and them (r=0.056, 0.045, 0.065, 0.022, P>0.05). Differences in total HOAs, coma aberration, spherical aberration, trefoil aberration were found among various axial groups (H=21.953, 20.665, 15.368, 16.881, P<0.05). Conclusions: Anterior corneal HOAs varied greatly among the majority of the patients. A significant negative correlation was found between axial length and anterior corneal HOAs, but no correlation was found between age and them. (Chin J Ophthalmol, 2017, 53: 828-834).

SMILE and Wavefront-Guided LASIK Out-Compete Other Refractive Surgeries in Ameliorating the Induction of High-Order Aberrations in Anterior Corneal Surface.

Purpose. To compare the change of anterior corneal higher-order aberrations (HOAs) after laser in situ keratomileusis (LASIK), wavefront-guided LASIK with iris registration (WF-LASIK), femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK), and small incision lenticule extraction (SMILE). Methods. In a prospective study, 82 eyes underwent LASIK, 119 eyes underwent WF-LASIK, 88 eyes underwent FS-LASIK, and 170 eyes underwent SMILE surgery. HOAs were measured with Pentacam device preoperatively and 6 months after surgery. The aberrations were described as Zernike polynomials, and analysis focused on total HOAs, spherical aberration (SA), horizontal coma, and vertical coma over 6 mm diameter central corneal zone. Results. Six months postoperatively, all procedures result in increase of anterior corneal total HOAs and SA. There were no significant differences in the induced HOAs between LASIK and FS-LASIK, while SMILE induced fewer total HOAs and SA compared with LASIK and FS-LASIK. Similarly, WF-LASIK also induced less total HOAs than LASIK and FS-LASIK, but only fewer SA than FS-LASIK (P < 0.05). No significant difference could be detected in the induced total HOAs and SA between SMILE and WF-LASIK, whereas SMILE induced more horizontal coma and vertical coma compared with WF-LASIK (P < 0.05). Conclusion. FS-LASIK and LASIK induced comparable anterior corneal HOAs. Compared to LASIK and FS-LASIK, both SMILE and WF-LASIK showed advantages in inducing less total HOAs. In addition, SMILE also possesses better ability to reduce the induction of SA in comparison with LASIK and FS-LASIK. However, SMILE induced more horizontal coma and vertical coma compared with WF-LASIK, indicating that the centration of SMILE procedure is probably less precise than WF-LASIK.

Descemet Stripping Endothelial Keratoplasty for Fuchs' Endothelial Corneal Dystrophy: Five-Year Results of a Prospective Study

To determine 5-year outcomes of Descemet stripping endothelial keratoplasty (DSEK) for Fuchs' endothelial corneal dystrophy (FECD). Prospective cohort study. Fifty-two eyes of 45 subjects with FECD undergoing primary DSEK. Subjects were examined before and at fixed intervals through 60 months after DSEK. At each visit, graft survival was determined by slit-lamp examination; best spectacle-corrected visual acuity (BSCVA) was measured using the electronic Early Treatment Diabetic Retinopathy Study (ETDRS) protocol; total anterior corneal higher-order aberrations (HOAs) were derived from corneal topography; and corneal backscatter, corneal thickness, and endothelial cell density were measured from confocal microscopy images. Corneal thickness also was measured by ultrasonic pachymetry. Changes after DSEK were analyzed using generalized estimating equation models. Best-corrected visual acuity, HOAs, endothelial cell loss, corneal thickness, and corneal backscatter. Complete 60-month follow-up was possible in 34 eyes. Mean BSCVA±standard deviation improved from 0.45±0.19 logarithm of the minimum angle of resolution (logMAR) (Snellen equivalent, 20/56) before DSEK to0.09±0.13 logMAR (Snellen equivalent, 20/25) at 5 years (P < 0.001). Between 1 and 5 years, BSCVA improved by 0.06 logMAR (or 3 ETDRS letters; 95% confidence interval, 0.05-0.07 logMAR) per year (P < 0.001), and 56% of eyes were 0.1 logMAR (20/25) or better at 5 years. Graft thickness (approximately 155 μm) and corneal thickness (approximately 700 μm) did not change after surgery. Anterior corneal HOAs and backscatter decreased between 1 and 5 years (P ≤ 0.002). Six grafts failed, of which 4 were primary (iatrogenic); mean endothelial cell loss±standard deviation was 55±15% at 5 years. Between 1 and 5 years after DSEK, BSCVA continues to improve such that at 5 years, more than half of eyes see better than 20/25 with a mean total corneal thickness of 700 μm. Improvement in vision is accompanied by continued reduction in corneal haze and aberrations, suggesting ongoing remodeling of the cornea after restoration of endothelial function.