Third-order Root Mean Square Research Articles

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.

Comparative evaluation of dual Scheimpflug imaging parameters in keratoconus, early keratoconus, and normal eyes

To determine the efficacy of various parameters measured by dual Scheimpflug imaging technology in differentiating eyes with keratoconus or early keratoconus from normal eyes. Cornea Service, Wills Eye Institute, Philadelphia, Pennsylvania, USA. Comparative case series. A retrospective evaluation was performed of the parameters provided by the Galilei dual Scheimpflug analyzer in keratoconus, early keratoconus, and normal eyes. Logistic regression and receiver operating characteristic curve analysis were used to compare the mean values and to calculate the sensitivity and specificity of these parameters. Many parameters were statistically significantly different between keratoconus and normal eyes compared with early keratoconus eyes (P<.05). Total cornea power-steep and posterior curvature-steep keratometry had the highest area under the curve (AUC) score (0.99) for differentiating keratoconus eyes from normal eyes. All anterior curvature parameters were statistically significant in differentiating keratoconus eyes from normal eyes, whereas only the anterior curvature-steep was statistically significant in differentiating early keratoconus eyes from normal eyes. The central pachymetry and thinnest pachymetry were statistically significant in differentiating keratoconus and early keratoconus eyes from normal eyes. Third-order root mean square (RMS) and total RMS had the highest AUC scores (0.83 and 0.82, respectively) for differentiating early keratoconus eyes from normal eyes. Total corneal power, anterior curvature, posterior curvature, pachymetry, and corneal aberration data generated from the dual Scheimpflug analyzer showed promising results in differentiating keratoconus and early keratoconus eyes from normal eyes. No author has a financial or proprietary interest in any material or method mentioned.

Changes in Refraction, Ocular Aberrations, and Corneal Structure After Suspending Rigid Gas-Permeable Contact Lens Wear in Keratoconus

This study reports on changes in visual acuity, ocular higher-order aberrations, and refraction after suspending rigid gas-permeable lens wear for 1 week in 15 patients with moderate to severe keratoconus. Alterations in the anterior surface, central corneal powers and axes, and central corneal thickness were also explored. Scheimpflug photography and Hartmann-Shack aberrometry were performed at 2 visits, 7 days apart, after the patients had removed their habitual contact lenses. Subjective refraction and both high- and low-contrast logarithm of the minimum angle of resolution visual acuities were also recorded at both visits. Reductions in both high-contrast visual acuity (P = 0.001) and low-contrast visual acuity (P = 0.002), along with an increase in third-order root mean square aberrations (P = 0.008), occurred after rigid gas-permeable lens wear was suspended in these patients with keratoconus. However, no significant changes in subjective refraction were found over the 1-week period (P ≥ 0.10). Significant correlations were observed between third-order coma root mean square aberrations and the measured high-contrast (r(p) ≥ 0.59; P ≤ 0.02) and low-contrast visual acuities (r(P) ≥ 0.61; P ≤ 0.015). In addition to increases in the anterior surface central corneal powers (P ≤ 0.02), a reduction in central corneal thickness also was found between the 2 visits (P = 0.00016). Changes in the optical and structural parameters of the keratoconic cornea occur after suspending rigid gas-permeable contact lens wear. This information may be of interest to practitioners concerned with prescribing aberration-controlling soft contact lenses for such patients.

Time Course of Changes in Ocular Aberrations After Instillation of Carteolol Long-Acting Solution and Timolol Gel-Forming Solution

To investigate the influence of 2% carteolol long-acting solution (long-acting carteolol) and 0.5% timolol gel-forming solution (timolol gel) on ocular wavefront aberrations. Ocular aberrations were assessed in the right eye of 24 healthy volunteers at baseline and at 2, 5, 10, and 15 min after instillation of long-acting carteolol, timolol gel or physiological saline using the Hartmann-Shack aberrometer. Ten serial measurements were taken over 10 s at each time point, and the root mean square (RMS) of second-, third-, fourth-, and total higher-order aberrations were calculated. The stability index and fluctuation index were also determined. Second-order aberrations did not change significantly after instillation of study eye-drops. Higher-order aberrations increased significantly after instillation of long-acting carteolol and timolol gel. Timolol gel induced significantly larger changes than long-acting carteolol in third-order RMS at 2 min (P = 0.001), fourth-order RMS at 2 (P < 0.001) and 5 (P = 0.013) min, and total higher-order RMS at 2 (P < 0.001) and 5 (P = 0.016) min after instillation, but not at 10 and 15 min after administration. Fluctuation index increased significantly after instillation of each eye-drop (P < 0.001), with significantly larger increases after timolol gel than long-acting carteolol at 2 min (P = 0.005) and 5 min (P = 0.011). No significant changes were observed in stability index. Both topical β blockers with a once-daily dosing regimen temporarily deteriorate optical quality of the eye by increasing higher-order aberrations, and the increases are much larger after instillation of timolol gel than long-acting carteolol.

Visual Acuity and Ocular Aberrations With Different Rigid Gas Permeable Lens Fittings in Keratoconus

The aim of this case report is to investigate the effect of rigid gas permeable (RGP) lens fitting on visual acuity and ocular higher-order aberrations by systematically applying RGP lenses with different back optic zone radii (BOZR) to a keratoconic eye.Eight Menicon-EX RGP lenses (Menicon Co., Nagoya, Japan), which ranged from a BOZR of 7.40 to 8.10 mm in 0.10-mm steps, were fitted to a moderate keratoconic eye. All the trial lenses fitted had a total diameter of 9.60 mm, centre thickness of 0.15 mm, and a back vertex power of -3.00 diopter sphere. Measurements of the higher-order aberrations were made with the RGP lenses in place using a Shack-Hartmann aberrometer (IRX-3; Imagine Eyes, Paris, France). Visual acuities with the lenses were recorded using a high-contrast Early Treatment Diabetic Retinopathy Study letter chart at a distance of 4 m.As the lens BOZR value changed from 7.40 to 8.10 mm, the vertical coma component was found to reduce from +0.34 to +0.21 microm; third-order root mean square error also reduced from +0.34 to +0.23 microm and total higher-order root mean square aberrations decreased from +0.35 to +0.23 microm. More over, changes in the lens BOZR from 7.40 to 8.10 mm led to a substantial change in best-corrected LogMAR acuity from +0.58 to -0.30 log units.The results showed that a flatter RGP lens fit lead to a reduction in higher-order aberrations and improvement in visual acuity in this moderate keratoconic patient. Further investigations into the changes in aberrations with different RGP lens fittings and BOZR values in keratoconic eyes will help to improve our current understanding of how contact lens fitting impacts on optical performance.

OCULAR WAVEFRONT ABERRATIONS IN PATIENTS WITH MACULAR DISEASES

There have been reports that by compensating for ocular aberrations using adaptive optical systems it may be possible to improve the resolution of clinical retinal imaging systems beyond what is now possible. To develop such a system to observe eyes with retinal disease, understanding of ocular wavefront aberrations in individuals with retinal disease is required. Eighty-two eyes of 66 patients with macular disease (epiretinal membrane, macular edema, macular hole, etc.) and 85 eyes of 51 patients without retinal disease were studied. Using a ray-tracing wavefront device, each eye was scanned at both small and large pupil apertures, and Zernike coefficients up to the sixth order were acquired. In phakic eyes, third-order root mean square errors in the macular disease group were statistically greater than in the control group, an average of 12% for 5-mm and 31% for 3-mm scan diameters (P < 0.021). In pseudophakic eyes, there was also an elevation of third-order root mean square, on average 57% for 5-mm and 51% for 3-mm scan diameters (P < 0.031). Higher-order wavefront aberrations in eyes with macular disease were greater than in control eyes without disease. This study suggests that such aberrations may result from irregular or multiple reflecting retinal surfaces. Modifications in wavefront sensor technology will be needed to accurately determine wavefront aberration and allow correction using adaptive optics in eyes with macular irregularities.

Mesopic Contrast Sensitivity and Ocular Higher-Order Aberrations in Eyes With Conventional Spherical Intraocular Lenses

To investigate relationship between mesopic contrast sensitivity (CS) function and ocular higher-order aberrations in eyes implanted with conventional spherical intraocular lenses (IOL). Prospective, nonrandomized case series. Sixty-eight eyes of 48 patients who attained best spectacle-corrected visual acuity (BSCVA) of 20/20 or better after phacoemulsification and spherical IOL implantation were included in the study. At 2 months postoperatively, mesopic CS was measured with the Mesotest II (Oculus; Wetsler, Germany), and ocular higher-order aberrations for a 4-mm pupil were measured with the Hartmann-Shack aberrometer. CS and letter CS under photopic conditions were recorded with the CSV-1000 charts (Vector Vision Co, Greenville, Ohio, USA). There was significant correlation between mesopic CS and ocular fourth-order root mean square (RMS) of wavefront aberration (Spearman r(s) = -0.293; P = .017), but no correlation was found between mesopic CS and ocular third-order RMS (r(s) = 0.196; P = .189). Ocular third- and fourth-order RMS did not correlate with other parameters, including BSCVA, and CS and letter CS under photopic conditions. Mesopic CS is significantly associated with ocular fourth-order RMS of wavefront aberrations in eyes implanted with conventional spherical IOLs.

One-Year Prospective Intrapatient Comparison of Aspherical and Spherical Intraocular Lenses in Patients with Bilateral Cataract

To conduct longitudinal, intrapatient comparisons of aspherical and spherical silicone intraocular lenses (IOL) of the same material and platform in patients undergoing bilateral cataract surgery. Prospective, randomized study. Sixty-two eyes of 31 patients were randomized to receive a silicone aspherical IOL (Tecnis Z9000; AMO Inc, Santa Ana, California, USA) in 1 eye and a silicone spherical IOL (CeeOn 911A; AMO Inc) in the other eye. Best spectacle-corrected visual acuity (BSCVA); corneal and ocular wavefront aberrations; contrast sensitivity under photopic (180 lux), intermediate (75 lux), and scotopic (15 lux) illumination; amount of IOL decentration and tilt; and degree of posterior capsular opacification were measured at 1, 3, 6, and 12 months after surgery. All-distance visual acuity (VA) was measured 3 months after surgery. There were no significant differences between IOLs with regard to BSCVA, amount of IOL decentration and tilt, degree of posterior capsule opacification, and all-distance VA at any point after surgery. Regarding corneal wavefront aberrations, there was no difference in third- and fourth-order root mean square (RMS). In ocular wavefront aberrations, aspherical IOLs showed significantly lower fourth-order RMS (P < .001) than spherical IOLs throughout the study, but not in third-order RMS. Contrast sensitivity under photopic and mesopic conditions was not different between IOLs, but contrast sensitivity under scotopic conditions was significantly better with aspherical IOLs than with spherical IOLs (P < .01) at all measurement points. The silicone aspherical IOL (Tecnis Z9000; AMO Inc) significantly reduced ocular spherical aberration and improved scotopic contrast sensitivity, and these results were consistent through the 1-year follow-up.

Intraindividual comparative study of corneal and ocular wavefront aberrations after biaxial microincision versus coaxial small-incision cataract surgery

Aim:To compare the optical outcomes of biaxial microincision cataract surgery (B-MICS) versus coaxial small-incision cataract surgery (C-SICS).Methods:Thirty patients (sixty eyes) with bilateral age-related cataract underwent B-MICS through a 1.7 mm...

Changes in Higher-Order Aberrations after Scleral Buckling Surgery for Rhegmatogenous Retinal Detachment

To evaluate changes in higher-order aberrations (HOAs) after scleral buckling surgery for the treatment of rhegmatogenous retinal detachment (RD). Prospective observational comparative case series. The study included 67 eyes of 67 rhegmatogenous RD patients undergoing scleral buckling surgery, and the fellow normal eyes comprised the control group. Twenty-seven eyes were treated with the segmental buckling procedure and 40 eyes received the encircling buckling procedure alone. Hartmann-Shack wavefront analysis was performed at 2 weeks, 1 month, and 3 months postoperatively. Time course of changes in HOAs. Scleral buckling surgery significantly increased HOAs at 2 weeks (P<0.0001), 1 month (P<0.0005), and 3 months (P<0.05) postoperatively as compared with the control group. At 3 months postoperatively, the HOAs were significantly lower in the encircling group than in the segmental buckling group (P<0.05). The vertical coma (Zernike Z(3)(-1)) became negative (significantly lower than zero, P<0.01) in patients who received segmental buckling in the upper quadrant. The ocular HOAs and logarithm of the minimum angle of resolution best-corrected visual acuity significantly correlated at 3 months postoperatively (third-order root mean square [RMS]: r = 0.445, P<0.0005; fourth-order RMS: r = 0.489, P<0.0001). Scleral buckling surgery significantly increased HOAs. The segmental buckling procedure increased the HOAs to a greater extent and for a longer duration than the encircling procedure. The direction of coma aberration corresponded to the location of the segmental buckle. The increase in HOAs can be one of the factors responsible for visual disturbances after scleral buckling surgery.

Higher Order Ocular Aberrations in Eyes With Myopia in a Chinese Population

To describe the characteristics of higher order ocular aberrations of adult Chinese eyes with myopia. Higher order aberrations in consecutive right eyes of 166 Chinese patients with myopia who enrolled for preoperative assessment for LASIK were retrospectively reviewed. Wavefront aberrations were measured with the Bausch & Lomb Zywave over a 6-mm dilated pupil. The correlations between higher order aberrations and myopia, astigmatism, and age, respectively, were analyzed. Mean patient age was 32.1 +/- 6.2 years, the mean refractive error was sphere -5.23 +/- 1.79 diopters (D) and cylinder -1.29 +/- 0.98 D. The mean of the total higher order root-mean-square (RMS) (third to fifth order) was 0.49 +/- 0.16 microm. Third-order RMS was largest (mean 0.37 +/- 0.16 microm), followed by fourth-order RMS (mean 0.29 +/- 0.11 microm). For individual higher order Zernike coefficients, spherical aberration (C4(0)) predominated with a mean of 0.23 +/- 0.14 microm. No correlation was found between total higher order RMS and myopia or between total higher order RMS and age. Small but statistically significant relationships were found in the following groups: age and vertical primary coma (C3(-1))(r=-0.206, P=.008); age and spherical aberration (C4(0)) (r=0.196, P=.012); and myopia and horizontal trefoil (C3(3)) (r=-0.158, P=.042). Higher order aberrations varied among individuals with myopia. Third-order RMS was the predominant higher order aberration. Spherical aberration and vertical primary coma increased slightly with age. Our study helps establish ocular aberration standards for Chinese refractive surgery candidates.

Corneal higher-order aberrations induced by overnight orthokeratology

To evaluate corneal higher-order aberrations induced by overnight orthokeratology for myopia. Prospective, noncomparative, consecutive, interventional case series. A prospective study was conducted in 64 eyes of 39 patients with overnight orthokeratology for myopia, who were followed up for at least 3 months and attained uncorrected visual acuity of 20/20 or better. Corneal height data were obtained with computerized videokeratography (TMS-2N, Tomey), and wavefront aberration was derived using Zernike polynomials. Higher-order aberrations of the cornea were calculated for 3- and 6-mm pupils. Orthokeratology significantly reduced manifest refraction from -2.60 +/- 1.13 (mean +/- SD) diopters to -0.17 +/- 0.31 diopters (P < .0001, paired t test). Root-mean-square (RMS) of third-order (coma-like) aberrations significantly increased by orthokeratology for both 3-mm (P < .0001, paired t test) and 6-mm (P < .0001) pupils. Fourth-order RMS (spherical-like) aberrations increased significantly by the treatment for both 3-mm (P < .0001) and 6-mm (P < .0001) pupils. Vertical coma significantly changed from positive to negative for both 3-mm (P = .0323) and 6-mm (P < .0001) pupils. Horizontal coma significantly increased to the positive direction for both 3-mm (P < .0001) and 6-mm (P < .0001) pupils. Increases in the third- and fourth-order RMS showed significant positive correlations with the amount of myopic correction for 3-mm (Pearson correlation coefficient, r = .452, P = .0001 for third-order RMS, r = .381, P = .0017 for fourth-order RMS) and 6-mm (r = .499, P < .0001, r = .455, P = .0001) pupils. Corneal higher-order aberrations significantly increased, even in clinically successful orthokeratology cases. The increases in the higher-order aberrations correlated with the magnitude of myopic correction.