Total Higher Order Aberrations Root Mean Square Research Articles

Optical quality with ocular aberrations in young myopic eyes with machine learning

Objective: The objective of this retrospective study was to employ machine learning techniques to examine age-related traits of ocular aberrations in a substantial population with myopia and myopic astigmatism. Methods: This was a cross-sectional study. Data from a population of myopic and myopic astigmatism patients who underwent wavefront aberration examinations at the Refractive Surgery Center of Tianjin Eye Hospital in Tianjin, China, were collected continuously from January 2013 to July 2017. The data from the right eye of each individual were collected for analysis. Each eye had 32 outcome data points, including age, best-corrected visual acuity (BCVA), lower-order aberrations (spherical diopter, cylindrical diopter, and astigmatic axis), and higher-order aberrations [Zernike coefficients and root mean square (RMS) of the third to sixth order aberrations] were analyzed. Higher-order aberrations were measured by Hartmann-Shack aberrometer. Results: The study included 1 507 subjects (1 507 eyes), comprising of 694 males and 813 females, with a mean age of (23.28±5.45) years. The findings demonstrated a decrease followed by an increase in most of the higher-order aberrations with age between 15-40 years. The minimum value points were observed in the age group of 25-30 years for RMS of total higher-order aberrations, 3rd RMS (with a confidence of 47.74% for range 1), 4th RMS (with a confidence of 86.01% for range 1), and trefoil aberrations (with a confidence of 56.38% for C33 and 73.25% for C3-3). The minimum value points were also observed in the age group of 30-35 years for primary spherical aberration (with a confidence of 56.10% for C40) and vertical coma-like aberration (with a confidence of 56.91% for C3-1). In contrast, astigmatism with the rule tended to decrease with age, while astigmatism against the rule and oblique astigmatism tended to increase (with a confidence of 88.66%, 84.71%, 81.07%, 79.67%, and 66.35% for astigmatism with the rule in different age groups). Conclusions: As age increases, the population with with-the-rule astigmatism decreases while the population with against-the-rule astigmatism increases. The high-order aberrations are the lowest in the 25-35 age group.

Higher order aberrations and visual function in a young Asian population of high myopes

PurposeTo examine the associations between higher order aberrations (HOAs), visual performance, demographics, and ocular characteristics in a young Asian population with high myopia. MethodsThis was a retrospective review of military pre-enlistees conducted between March 2014 to September 2018. Visual acuity and contrast sensitivity were tested under photopic, mesopic and simulated night conditions. Ocular, corneal and internal HOAs were measured with a Hartmann–Shack wavefront aberrometer (KR-1W, Topcon Co., Tokyo, Japan). Results522 eyes of 263 consecutive subjects with severe high myopia (defined as spherical equivalent refraction [SER] ≤ −10.00D) in at least one eye, and high myopia (SER ≤ −6.00D) in the fellow eye, [mean (SD) SER −11.85 (2.03D)] were analysed. The mean (SD) age of subjects was 18.5 (1.6) years. Chinese eyes had significantly greater internal total HOA root-mean-square (RMS) compared to Malay eyes [mean difference (SD) 0.0246 (0.007) μm, p < 0.001). More negative SER was associated with greater ocular total HOA (p = 0.038), primary coma (p = 0.003) and tetrafoil (p = 0.025) RMS, as well as more positive ocular (p = 0.003) and internal primary spherical aberration (p = 0.009). Greater ocular total HOAs was associated with reduced visual acuity in simulated night conditions and low contrast, decreased contrast sensitivity under mesopic and simulated night conditions (all p < 0.05). ConclusionsGreater HOAs were associated with Chinese ethnicity and more negative SER in a young Asian population with high myopia. Greater HOAs were associated with poorer visual performance in low luminance and reduced contrast conditions.

Changes in higher order aberrations after central corneal regularization - a comparative two-year analysis of a semi-automated topography-guided photorefractive keratectomy combined with corneal cross-linking

BackgroundThe optical quality in progressive keratoconus deteriorates due to ectasia and distortion of the corneal shape and optics. While corneal cross-linking (CXL) aims at stopping disease progression, “CXL-Plus” combines CXL with excimer laser ablation to improve visual function. Central Corneal Regularization (CCR) represents a therapeutic excimer laser modality specifically designed to smoothen the ectatic corneal shape and to reduce higher order aberrations (HOA). We set out to compare CXL-Plus, consisting of CXL combined with CCR, with CXL by itself for patients with progressive keratoconus.MethodsRetrospective 2-year matched group analysis of patients who either underwent CXL-Plus (n = 28) or CXL as a sole procedure (n = 28) for progressive keratoconus. Main outcome parameters were HOA, visual function and tomographic results 12 and 24 months postoperatively.ResultsAfter 12 months, the total HOA root mean square wavefront error was reduced from 0.79 ± 0.30 to 0.40 ± 0.19 μm (CXL-Plus; p < 0.0001) and changed from 0.71 ± 0.28 to 0.73 ± 0.36 μm (CXL; p = 0.814). Uncorrected distance visual acuity improved from 0.70 ± 0.35 to 0.36 ± 0.29 logMAR (CXL-Plus; p = 0.0002) and from 0.65 ± 0.39 to 0.46 ± 0.37 logMAR (CXL; p = 0.067), translating to gains of three or more lines in 50% (CXL-Plus) and 36% (CXL) of patients. The steepest keratometry value (Kmax) regressed by 5.84 D (CXL-Plus; p < 0.0001) and 0.66 D (CXL; p = 0.752). For none of the investigated parameters a statistically significant change could be shown between 12 and 24 months.ConclusionsCXL-Plus in the form of a CCR reduces HOA and Kmax more effectively than CXL as a sole procedure.

Corneal higher order aberrations after intrastromal corneal ring segment implantation for keratoconus

Background Keratoconus is the most common primary corneal ectatic disease. It is a progressive, noninflammatory, and localized paraxial stromal thinning of the cornea, which often results in bilateral and asymmetrical corneal distortion and anterior corneal protrusion. Patients with corneal protrusion often develop high myopia and irregular astigmatism, resulting in significant impairment of visual acuity.Purpose The aim of this study was to assess changes of higher order aberrations (HOAs) induced by the implantation of intrastromal corneal ring segments (ICRS) in keratoconus.Patients and methods In the current study, a prospective analysis of HOAs, measured by using Pentacam, before and after ICRS implantation was done in a nonrandomized consecutive series of 20 eyes having progressive grade II/III keratoconus (Amsler-Krumeich classification).Results At 1 month postoperatively, a statistically highly significant reduction was found in keratometric readings. The flattest keratometric reading (K1) improved from 46.42±3.08 D preoperatively to 43.25±3.45 D postoperatively, which is highly significant (P<0.01). The steepest keratometric reading (K2) improved from 49.96±3.29 D preoperatively to 46.04±3.15 D postoperatively, which is highly significant (P>0.01). The total HOA root mean square improved from 1.55±0.54 preoperatively to 1.26±0.38 postoperatively, with a statistically significant difference (P<0.05). Primary coma improved from 1.27±0.54 preoperatively to 0.87±0.27 postoperatively, which is highly significant (P>0.01). In addition, astigmatism root mean square changed from 2.42±1.52 preoperatively to 1.98±1.31 postoperatively. Trifoil and quadrifoil showed nonsignificant changes (P>0.05).Conclusion ICRS (Keraring) implantation using femtosecond laser is an effective method for improvement and stabilization of optical, keratometric, and aberrometric measures in keratoconic eyes. Most of the improvement in HOAs was achieved after 1 month and nearly locked up or changed insignificantly till the third month.

Pattern of wavefront aberrations in Indian children with ametropia

Purpose: The aim of this study was to evaluate the distribution of wavefront aberrations in Indian children with refractive errors and to determine the correlation between the degree of refractive error and aberration. Materials and Methods: A prospective study was conducted on 216 eyes of 108 consecutive children attending the outpatient clinic. Based on refractive error, the children were allocated to five groups: “Emmetropic,” “hyperopic,” “simple astigmatism,” “compound astigmatism,” and “myopic” group. Lower order aberrations (LOAs) and higher order aberrations (HOAs) were analyzed within and between the groups. Results: Mean age of the children was 10.9 years. Of the total 216 eyes, 40 eyes had emmetropia, 52 had simple astigmatism, 54 had compound astigmatism, 43 had myopia, and 27 had hyperopia. In all the groups, increase in spherical equivalent was associated with increase in LOAs of defocus and astigmatism and the root mean square (RMS) of total HOAs. In comparison with the “emmetropic” group, all other groups showed a significant increase in LOAs (P < 0.001) and RMS of total HOAs (P < 0.001), with the “compound astigmatism” group showing higher values. Spherical aberrations were found to be associated with simple astigmatism, compound astigmatism (P = 0.008), and myopia (P = 0.041). Statistical analysis was done using analysis of variance applying Bonferroni correction factor and Pearson's correlation coefficient. Conclusions: Ametropic eyes are associated with HOAs. Indian children were found to have higher values of aberrations when compared to other races. Practitioners may need to factor this while treating children for refractive errors.

Effect of iris registration on outcomes of FEMTOLASIK for myopia and myopic astigmatism.

To compare the visual and refractive outcomes after FEMTOLASIK with and without iris registration. In this randomized, prospective, comparative, contralateral eye study, 118 eyes of 59 patients with myopia and myopic astigmatism underwent LASIK using the Femto LDV femtosecond laser (160µm) and the MEL80 with or without iris registration. For each patient, iris registration FEMTOLASIK was performed on one eye and non-iris registration FEMTOLASIK was performed on the other eye, assigned at random. Patients were evaluated before and 12months. Uncorrected visual acuity, best-corrected visual acuity, manifest refraction, contrast sensitivity, and higher-order aberrations (HOAs) were evaluated. At 12months, the mean UDVA was 0.002±0.07 logMAR (20/19) in iris registration eyes and 0.00±0.06 logMAR (20/24) in non-iris registration eyes (P=0.9). 61% of iris registration eyes and 71.2% of non-iris registration eyes achieved a UDVA of 20/20 or better (P=0.31); 98.3% of eyes with the iris registration FEMTOLASIK and 94.9% with the non-iris registration FEMTOLASIK were within ±0.50D from emmetropia (P=0.71). No statistically significant difference was found in postoperative contrast sensitivity between groups at 3, 6, 12, or 18 cycles/degree (P>0.05). There was significant increase in total HOA root mean square in two groups. The mean error magnitude of surgically induced astigmatism 12months postoperatively was -0.33 in iris registration eyes and -0.24 in the non-iris registration eyes (P=0.36). FEMTOLASIK with and without iris registration provides similar results in myopic and myopic astigmatism patients.

Comparison of Higher Order Aberrations after Wavefront-guided LASIK and PRK: One Year Follow-Up Results.

Purpose:To evaluate the changes and predictability of higher order aberrations (HOAs) after personalized laser in situ keratomileusis (LASIK) and personalized photorefractive keratectomy (PRK) for simple myopia and compound myopic astigmatism.Methods:In this prospective cross-sectional study, 100 eyes were included. A total of 50 eyes underwent personalized LASIK and 50 eyes underwent personalized PRK. Preoperative and postoperative wavefront data were compared between the two groups. The influential factors and predictability of HOAs were also assessed.Result:Total HOA increased in the amount of 0.01 ± 0.14 μm for the 5 mm pupil (P = 0.55) and 0.08 ± 0.22 μm for the 6 mm pupil (P = 0.02) after PRK; however after LASIK the corresponding values for the 5 and 6 mm pupil sizes were 0.05 ± 0.12 and 0.15 ± 0.18 μm, respectively (P < 0. 001). Mean changes were not significantly different between the PRK and LASIK groups for both 5 and 6 mm pupil sizes (P = 0.21 and P = 0.13, respectively). Spherical aberration increased following LASIK more than following PRK (P < 0.001). Changes in the root mean square (RMS) of total HOA had a statistically significant negative correlation (P < 0.001) with its preoperative value. HOA and spherical aberration reduced in majority of eyes when the preoperative spherical equivalent refraction was low.Conclusion:For the 6mm pupil size, the total HOA increased following both personalized PRK and LASIK with no significant difference between the two groups. Change of the total HOA RMS was influenced by the preoperative values. The known influencing factors could predict nearly 50% of the changes in total HOA.

Short-term corneal changes with gas-permeable contact lens wear in keratoconus subjects: A comparison of two fitting approaches

PurposeTo evaluate changes in anterior corneal topography and higher-order aberrations (HOA) after 14-days of rigid gas-permeable (RGP) contact lens (CL) wear in keratoconus subjects comparing two different fitting approaches. MethodsThirty-one keratoconus subjects (50 eyes) without previous history of CL wear were recruited for the study. Subjects were randomly fitted to either an apical-touch or three-point-touch fitting approach. The lens’ back optic zone radius (BOZR) was 0.4mm and 0.1mm flatter than the first definite apical clearance lens, respectively. Differences between the baseline and post-CL wear for steepest, flattest and average corneal power (ACP) readings, central corneal astigmatism (CCA), maximum tangential curvature (KTag), anterior corneal surface asphericity, anterior corneal surface HOA and thinnest corneal thickness measured with Pentacam were compared. ResultsA statistically significant flattening was found over time on the flattest and steepest simulated keratometry and ACP in apical-touch group (all p<0.01). A statistically significant reduction in KTag was found in both groups after contact lens wear (all p<0.05). Significant reduction was found over time in CCA (p=0.001) and anterior corneal asphericity in both groups (p<0.001). Thickness at the thinnest corneal point increased significantly after CL wear (p<0.0001). Coma-like and total HOA root mean square (RMS) error were significantly reduced following CL wearing in both fitting approaches (all p<0.05). ConclusionShort-term rigid gas-permeable CL wear flattens the anterior cornea, increases the thinnest corneal thickness and reduces anterior surface HOA in keratoconus subjects. Apical-touch was associated with greater corneal flattening in comparison to three-point-touch lens wear.

Corneal Reshaping and Wavefront Aberrations During Overnight Orthokeratology

To investigate changes of corneal thickness at the vertical and horizontal meridians and of wavefront aberrations (WA) over a 30-day period of overnight myopia orthokeratology (OK) lens wear. Sixteen subjects (11 women, 5 men, 26.3±3.2 years) were enrolled and fitted for OK lenses. Long scan depth optical coherence tomography was used to measure corneal thickness profiles at both horizontal and vertical meridians at baseline and on days 1, 7, and 30 days. Corneal and ocular WA of a 6-mm pupil were measured and the root-mean-square (RMS) of the astigmatism, coma, spherical aberration (SA), and total higher-order aberrations (HOAs) were determined. During the 30-day period, the central cornea thinned in the horizontal and vertical meridians, whereas corneal thickening occurred in the temporal, nasal, and inferior mid-peripheries. In contrast, the cornea thinned in the mid-peripheral superior. There were significant increases in RMS for astigmatism, SA, coma, and positive horizontal coma during the study period. After OK, there were significant positive correlations between the midperipheral-central thickness change difference and the changes in corneal and ocular RMS of total HOAs and SA (r range: 0.281 to 0.492, P<0.05). Only the change of corneal coma RMS was correlated with midperipheral-central thickness change difference (r=0.270, P<0.05). The change in corneal horizontal coma was correlated with the temporal-nasal thickness change difference (r=-0.289, P<0.05). Overnight OK caused unique changes in corneal thickness profiles at the vertical and horizontal meridians and increased corneal and ocular HOAs related to corneal reshaping.

Higher order aberrations of the corneal surface after laser subepithelial keratomileusis.

PurposeTo evaluate the changes of higher order aberrations (HOAs) before and after laser subepithelial keratomileusis (LASEK) and to analyze the influence of tear film instability on HOAs of the corneal surface after LASEK.MethodsIn this cross-sectional study, 31 patients who underwent LASEK were divided into dry eye (16 patients, 32 eyes) and non-dry eye groups (15 patients, 30 eyes). Uncorrected distance visual acuity, spherical equivalent refraction, ablation depth, tear film parameters and Ocular Surface Disease Index (OSDI) questionnaire scores were evaluated in both groups. Total HOA root mean square (RMS), third-order coma, third-order trefoil and fourth-order spherical aberration (SA) of the corneal surface immediately and at 10 seconds after blinking were measured before and after surgery.ResultsThe total HOA RMS, coma, trefoil and SA significantly increased after LASEK compared with preoperative values in both groups. In the dry eye group, total HOA RMS, coma and trefoil significantly increased except for SA at 10 seconds after blinking compared with those measured immediately after blinking. In addition, the changes of total HOA RMS, coma and trefoil were negatively correlated with tear film break-up time (R = -0.420, -0.473 and -0.439, respectively), but positively correlated with OSDI score (R = 0.433, 0.499 and 0.532, respectively). In the non-dry eye group, there were no significant differences between HOAs measured at 10 seconds after blinking and those measured immediately after blinking.ConclusionsThe HOAs including coma, trefoil and SA significantly increased after LASEK. The tear film instability in the dry eye can be associated with more deterioration of the optical quality after LASEK, due to more significant increase of total HOA RMS, coma and trefoil.

A clinical study between coneal wavefront aberration guided LASIK and LASEK on higher order aberration

Objective To analyze the effects of coneal wavefront aberration guided laser in situ keratomileusis (W-G-LASIK) and coneal wavefront aberration guided laser epithelial keratomileusis (W-G-LASEK) on higher order aberrations (HOAs) in patients with myopia.Methods 122 eyes of 61 cases underwent W-G-LASIK or W-G-LASEK for myopia,including 27 cases (54 eyes) in W-G-LASIK (group A)and 34 cases (68 eyes) in W-G-LASEK (group B).An examination of HOAs was performed on each eye preoperatively and 7 d,1 and 3 months postoperatively.Results The results of total HOAs root mean square (RMS) showed an increase in both the two groups compared with that of preoperative one.The 3rd and 4th high order aberration were dominantly increased.It was lower in group B than in group A in total,3rd、4th high order aberration(P ＜0.05).The vertical coma (C7),horizontal coma (C8) and spherical aberration (C12) were increased after operation in both of the two groups (P ＜ 0.05).And there was significant difference between the two groups in C7,which was higher in group A (P ＜ 0.05).Conclusion Both W-G-LASIK and W-G-LASEK could increase the HOAs,but the HOAs after W-G-LASEK was lower than that after W-G-LASIK. Key words: Laser in situ keratomileusis; Laser epithelial keratomileusis; Wavefront aberration,corneal

Wavefront-Guided and Aspheric Ablation for Myopia – One-Year Results of the Zyoptix Personalized Treatment Advanced Algorithm

To evaluate the visual outcome and change in higher-order aberrations (HOAs) 1 year post simultaneous wavefront-guided and aspheric photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Prospective interventional case series. Consecutive myopic patients undergoing PRK (38 eyes of 23 patients) and LASIK (42 eyes of 25 patients) using the Technolas 217z100 excimer laser (Technolas Perfect Vision) in a private laser clinic were included. Main outcome measures were uncorrected distance visual acuity (UDVA), manifest refraction (MRSE), HOAs, and spherical aberration (Z(4)(0)). At 1 year, 87% (32/37) of PRK eyes and 81% (30/37) of LASIK eyes had UDVA of 20/20 or better (P = .75). Mean ± SD MRSE was -0.26 ± 0.31 diopters (D) in the PRK and -0.16 ± 0.34 D in the LASIK group (P = .222). There was no significant increase in total HOA root mean square (RMS) in the PRK group. Mean ± SD total HOA RMS increased from 0.402 ± 0.14 μm to 0.496 ± 0.17 μm (P = .013) in the LASIK group at 1 year. Z(4)(0) increased from mean ± SD -0.045 ± 0.12 μm to -0.109 ± 0.15 μm (P = .006, factor 2.42) in the PRK group and did not significantly increase in the LASIK group (mean ± SD -0.16 ± 0.17 μm to -0.17 ± 0.15 μm (P = .469, factor 1.08) at 6 mm pupil. Visual outcome was excellent in both treatment groups. HOAs were still increased following LASIK by a factor of 1.23 but not PRK. Z(4)(0) was not induced by LASIK with the treatment algorithm but was negatively induced in PRK eyes.

A prospective, randomized, fellow eye comparison of WaveLight&amp;reg; Allegretto Wave&amp;reg; Eye-Q versus VISX CustomVue&amp;trade; STAR S4 IR&amp;trade; in laser in situ keratomileusis (LASIK): analysis of visual outcomes and higher order aberrations

PurposeTo compare outcomes in visual acuity, refractive error, higher-order aberrations (HOAs), contrast sensitivity, and dry eye in patients undergoing laser in situ keratomileusis (LASIK) using wavefront (WF) guided VISX CustomVue and WF optimized WaveLight Allegretto platforms.MethodsIn this randomized, prospective, single-masked, fellow eye study, LASIK was performed on 44 eyes (22 patients), with one eye randomized to WaveLight Allegretto, and the fellow eye receiving VISX CustomVue. Postoperative outcome measures at 3 months included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive error, root-mean-square (RMS) value of total and grouped HOAs, contrast sensitivity, and Schirmers testing.ResultsMean values for UDVA (logMAR) were −0.067 ± 0.087 and −0.073 ± 0.092 in the WF optimized and WF guided groups, respectively (P = 0.909). UDVA of 20/20 or better was achieved in 91% of eyes undergoing LASIK with both lasers while UDVA of 20/15 or better was achieved in 64% of eyes using the Allegretto platform, and 59% of eyes using VISX CustomVue (P = 1.000). In the WF optimized group, total HOA increased 4% (P = 0.012), coma increased 11% (P = 0.065), and spherical aberration increased 19% (P = 0.214), while trefoil decreased 5% (P = 0.490). In the WF guided group, total HOA RMS decreased 9% (P = 0.126), coma decreased 18% (P = 0.144), spherical aberration decreased 27% (P = 0.713) and trefoil decreased 19% (P = 0.660). One patient lost one line of CDVA secondary to residual irregular astigmatism.ConclusionBoth the WaveLight Allegretto and the VISX CustomVue platforms had equal visual and safety outcomes. Most wavefront optimized HOA values trended upward, with a statistically significant increase in total HOA RMS. Eyes treated with the WF guided platform showed a decreasing trend in HOA values.

Ocular wavefront analysis and contrast sensitivity in eyes implanted with AcrySof IQ or AcrySof Natural intraocular lenses

This study aimed to compare ocular wavefront aberrations for pupil diameters of 4 mm and 6 mm, and contrast sensitivity, in eyes with AcrySof IQ and AcrySof Natural intraocular lenses (IOLs). Sixty eyes of 60 patients were enrolled in this prospective randomized study. After phacoemulsification the eyes received either AcrySof IQ SN60WF or AcrySof Natural SN60AT IOLs. One month after surgery, all patients underwent complete ophthalmological examination including corneal topography, wavefront analysis for pupil diameters of 4 mm and 6 mm, and contrast sensitivity measurements with the CSV 1000E instrument under photopic and mesopic conditions with and without glare. There was no statistically significant difference between groups in age, sex or other preoperative ocular characteristics (p > 0.05). Patients with AcrySof IQ IOLs had higher contrast sensitivity at 6 c.p.d. under photopic conditions, at 6 c.p.d. and 18 c.p.d. under mesopic conditions, and at 6 c.p.d., 12 c.p.d. and 18 c.p.d. under mesopic conditions with glare (p < 0.05). Corneal spherical aberration was 0.273 ± 0.074 μm in the AcrySof Natural group and 0.294 ± 0.086 μm in the AcrySof IQ group (p = 0489). Ocular spherical aberration was 0.362 ± 0.141 μm and 0.069 ± 0.043 μm (p < 0.001) for 6-mm diameter pupils and 0.143 ± 0.091 μm and 0.017 ± 0.016 μm (p < 0.001) for 4-mm diameter pupils, with AcrySof Natural and AcrySof IQ IOLs, respectively. There were no significant differences in other higher-order aberrations between the groups (p > 0.05). Aspherical AcrySof IQ IOLs significantly reduced spherical aberration for pupil diameters of both 4 mm and 6 mm and also improved contrast sensitivity more than spherical AcrySof Natural IOLs, especially in mesopic conditions.

The effect of Nd:YAG laser posterior capsulotomy on ocular wave front aberrations

Objective: To assess the effect of Nd:YAG laser posterior capsulotomy on ocular wave front aberrations. Study Design: Retrospective comparative study. Participants: Twenty-four eyes of 24 consecutive pseudophakic patients with symptomatic PCO, who presented for Nd:YAG laser posterior capsulotomy at our clinic, were included in this study. Methods: The wave front aberrations of the entire optical path of 24 pseudophakic eyes of 24 patients before, and 1 month after, Nd:YAG laser posterior capsulotomy were measured using the Nidek Optical Path Difference (OPD) scan aberrometer. Total, tilt, and high-order aberrations, and total coma, total trefoil, total tetrafoil, total spherical, and total high astigmatism aberrations were analyzed statistically. Secondary measures included changes in visual acuity and refraction, and repeatability of wave front measurements in the fellow eye. Results: Before Nd:YAG laser posterior capsulotomy, the total higher-order aberrations root mean-square (RMS) wave front aberration was 2.08 (SD 2.20) μm, with total trefoil being a major contributor at 1.19 (SD 1.15) μm. One month after the procedure, significant decreases in total, tilt, and high-order aberrations, and total trefoil, total tetrafoil, total spherical, and total high astigmatism aberrations were noted ( p < 0.05). No significant changes in total coma aberrations were found ( p > 0.05). Additionally, significant improvement in visual acuity without significant change in refraction was observed. No statistically significant differences were detected in any of the RMS values of wave front measurements taken 1 month later in the fellow eye. Conclusions: Nd:YAG laser posterior capsulotomy causes significant decrease in ocular wave front aberrations measured using the Nidek-OPD scan aberrometer, which can account for a better optical quality after the procedure. Further research to examine the impact of wave front aberrations in visual function after Nd:YAG laser posterior capsulotomy is needed.

Variability of Higher Order Wavefront Aberrations After Blinks

To investigate the rapid alterations in value and fluctuation of ocular wavefront aberrations during the interblink interval. Forty-two volunteers were examined with a WASCA Wavefront Analyzer (Carl Zeiss Meditec AG) using modified software. For each subject, 150 images (about 6 frames/second) were registered during an interblink period. The outcome measures were spherical and cylindrical refraction and root-mean-square (RMS) values for spherical, coma, and total higher order aberrations. Fifth order polynomials were fitted to the data and the fluctuation trends of the parameters were determined. We calculated the prevalence of the trends with an early local minimum (type 1). The tear production status (Schirmer test) and tear film break-up time (BUT) were also measured. Fluctuation trends with an early minimum (type 1) were significantly more frequent than trends with an early local maximum (type 2) for total higher order aberrations RMS (P=.036). The incidence of type 1 fluctuation trends was significantly greater for coma and total higher order aberrations RMS (P=.041 and P=.003, respectively) in subjects with normal results in the BUT or Schirmer test than in those with abnormal results. In the normal subjects, the first minimum of type 1 RMS fluctuation trends occurred, on average, between 3.8 and 5.1 seconds after blink. We suggest that wavefront aberrations can be measured most accurately at the time after blink when they exhibit a decreased degree of dispersion. We recommend that a snapshot of wavefront measurements be made 3 to 5 seconds after blink.

Comparative Study of Higher-Order Aberrations After Conventional Laser In Situ Keratomileusis and Laser Epithelial Keratomileusis for Myopia Using the Technolas 217z Laser Platform

To examine changes in higher-order aberrations (HOAs) after PlanoScan laser in situ keratomileusis and (LASIK) and laser epithelial keratomileusis (LASEK). Prospective, comparative study. Myopic patients undergoing LASIK (65 eyes of 36 patients) and LASEK (50 eyes of 28 patients) at a private practice were selected randomly. Surgery was performed using the Technolas 217z laser (Bausch & Lomb, Surrey, United Kingdom). Main outcome measures included uncorrected visual acuity (UCVA), manifest refractive spherical equivalent (MRSE), and aberrometry (Zywave; Bausch & Lomb, Rochester, New York, USA) and were recorded before surgery and at three and 12 months after surgery. There was no statistical difference between both groups in terms of MRSE (P = .91), ablation depth (P = .47), scotopic pupil size (P = .38), or optical zone (P = .07). Before surgery, there was no statistical difference in root mean square (RMS) of total (P = .70), third- (P = .79), fourth- (P = .23), and fifth- (P = .33) order aberrations and individual terms. Three months after surgery, RMS of total HOA was raised significantly more (P = .03) after LASIK (1.46-factor increase) than LASEK (1.25-factor increase). One year after surgery, a reduction in total HOAs was observed in 13.8% of LASIK- and 48.5% of LASEK-treated eyes compared with preoperative levels. Postoperative increases in total HOA and vertical coma were significantly greater in LASIK- than in LASEK-treated eyes. Postoperative reduction in total HOAs was observed in a number of eyes with high preoperative levels and occurred more frequently in LASEK-treated eyes.

The Effect of Lubricant Eye Drops on Ocular Wavefront Aberrations

To study the effect of lubricant eye drop instillation on ocular wavefront aberrations. The wavefront aberrations of the entire optical path of 30 eyes of 15 patients before and following instillation of lubricant eye drops (Bion Tears; Alcon Laboratories Inc, Ft Worth, Tex) were obtained over a 6-mm pupil using a Hartmann-Shack wavefront sensor (WaveScan; VISX Inc, Santa Clara, Calif). Additional computation of root-mean-square (RMS) errors of higher order aberrations from third to sixth order were done using Zernike Tool Software (VISX Inc). Main outcome measures include the mean changes of total higher order aberrations RMS, higher order aberrations, and point spread function (PSF) of the higher order aberrations. The mean changes of total higher order aberrations following instillation of lubricant eye drops on the right eyes were -0.07 microm (95% confidence interval [CI], -0.11 to -0.03) and -0.03 microm on the left eyes (95% CI, -0.07 to 0.01). Significant mean changes were noted for coma and trefoil aberrations with a magnitude of -0.08 microm (95% CI, -0.12 to -0.03) and -0.09 (95% CI, -0.13 to -0.05), respectively, as well as a mean change of the PSF of the higher order aberrations (-0.05 diopters, 95% CI, -0.08 to -0.02) on the right eyes. Although no significant changes in these parameters were demonstrated on the left eyes, a similar trend of changes was observed. Ocular wavefront aberrations may change following eye drop instillation as measured objectively by the WaveScan system. This effect should be taken into consideration in the assessment of patients for wavefront-guided laser vision correction procedures.

Wavefront-guided LASIK with the Zyoptix 3.1 system for the correction of myopia and compound myopic astigmatism with 1-year follow-up: Clinical outcome and change in higher order aberrations

To assess safety, efficacy, predictability, stability, and change in aberrations after wavefront-guided LASIK for myopia and myopic astigmatism. Prospective, nonrandomized, self-controlled trial. Wavefront-guided LASIK was performed in 97 eyes in a 1-year trial. Treated eyes had a mean subjective manifest spherical equivalent (SE) of -5.22+/-2.07 diopters (D), with a range of -0.25 to -9.00 D of myopia and 0 to -3.25 D of astigmatism. After a microkeratome cut, a wavefront-based excimer ablation (Zyoptix 3.1) was performed. The full treatment to achieve emmetropia of an early nomogram provided by the system manufacturer was used in all procedures. Safety, efficacy, predictability, and stability were evaluated at 1, 3, and 12 months postoperatively. Wavefront changes of higher order aberrations (HOAs) at 1 year were determined for pupil sizes of 3.5 and 6 mm. At 1 year postoperatively, uncorrected visual acuity (VA) was 20/20 or better in 83% of the eyes, and 20/40 or better in 98%. The mean subjective manifest SE at 1 year was -0.25+/-0.43 D; it was within 0.50 D in 77% and within 1.0 D in 95%. No eye lost > or =2 lines of best spectacle-corrected VA (BSCVA) at 1 year postoperatively; 40 eyes gained 1 line of BSCVA, and 5 eyes gained 2 lines. The total HOA root mean square (RMS) increased on average by a factor of 1.23+/-0.57 with a 3.5-mm pupil; for the 6 mm pupil, the increase factor was 1.52+/-0.36. No change or reduction in the total HOA RMS was observed in 45.5% of the eyes for a 3.5-mm pupil and in 20.6% for a 6-mm pupil. There was a significant increase of primary spherical aberration (Z 4,0) by a factor of 4.11+/-10.17 for 3.5-mm pupils and 4.31+/-6.76 for 6-mm pupils. Wavefront-guided LASIK using Zyoptix 3.1 is an effective and safe procedure for the treatment of myopia and myopic astigmatism. Although in close to half of the eyes HOAs could be reduced, there was still undercorrection and induction of HOAs with the algorithm employed.

Comparison of higher order aberrations in patients with various refractive errors

Objective:To compare the mean root mean square (RMS) of total higher order aberrations (HOAs), coma and spherical aberrations in individuals with myopia, hypermetropia and myopic astigmatism.Methods:This prospective analytical study was conducted at Armed Forces Institute of Ophthalmology, Rawalpindi, Pakistan from Jan 2014 to Dec 2014. Two hundred eyes of 121 patients with age ranging from 18-40 years were included in the study. Patients were divided into 4 group namely Low myopia, High myopia, Astigmatism and Hypermetropia on the basis of refractive error. Included were the patients who had refractive error more than ± 0.5D and best corrected visual acuity (BCVA) of 0.00 or better. Patients who had history of surgery and / or eye disease were excluded from the study. Visual acuity (VA), Spherical equivalent (SE) of refractive error, RMS value of total HOAs, coma and spherical aberrations were evaluated. HOAs were measured with aberrometer (Wavelight analyzer version 1073) at 6 mm pupil size.Results:Age of the patients ranged from 18 years to 40 years with mean age of 29.10±10.6 years. Seventy one (35.5%) were males and 129 (64.5%) were female. Mean RMS value of HOAs, coma and spherical aberrations was calculated in all four groups. RMS of total HOAs and spherical aberrations in hypermetropia was 0.96±0.96 and 0.30±0.42 respectively and it was higher than other three groups.Conclusions:In overall comparison the mean RMS of total HOAs and spherical aberrations was significantly increased in hypermetropia group and there was a statistically significant negative correlation of SE of hypermetropia with RMS of total HOAs and spherical aberration.