Automated keratoconus detection using height data of anterior and posterior corneal surfaces.

PURPOSE: To develop a keratoconus detection algorithm using the corneal topographic data of the anterior and posterior corneal surfaces. METHODS: Topographic measurements of the cornea were made with a slit-scanning corneal topographer. We examined 120 subjects (165 eyes); keratoconus patients and keratoconus suspect patients comprised the keratoconus group, and post-photorefractive keratectomy patients, with-the-rule astigmatism patients, and controls without disease comprised the nonkeratoconus group. Two variables of the anterior corneal surface, two variables of the posterior corneal surface, and one corneal thickness variable were obtained by applying the Fourier harmonic decomposition formula. By performing a logistic regression analysis with a training set to differentiate the keratoconus group from the nonkeratoconus group, the Fourier-incorporated keratoconus detection Index (FKI) was created. The validity of the FKI was determined by using independent validation sets. RESULTS: The FKI distinguished the keratoconus group from the nonkeratoconus group with 96.9% sensitivity and 95.4% specificity in the validation set. CONCLUSIONS: A newly developed automated keratoconus classifier can be used to screen keratoconic patients. The index is based on information obtained by Fourier analysis from not only the anterior corneal surface but also from the posterior corneal surface and corneal thickness.

Age-related changes in ocular and corneal aberrations.

PURPOSE: To compare the ocular and corneal higher-order aberrations (HA) in eyes of different ages. DESIGN: Observational cross-sectional study. METHODS: Sixty-six eyes of 66 normal subjects (age range 4-69 years; average 37.4 +/- 15.4 years) were examined. Wavefront aberrations of the whole eye (ocular) and cornea were measured for the central 4 mm using a Hartmann-Shack aberrometer. RESULTS: Ocular Coma-like aberration (r = 0.270, P =.029), Spherical-like aberration (r = 0.531, P =.001), and total HA(r = 0.431, P =.001) were significantly correlated with age, whereas the corneal aberrations were not significantly correlated. The ocular total HA aberrations increased significantly after age 50 years. CONCLUSIONS: After 50 years of age, ocular aberrations increased abruptly due to the increase of lenticular HA. Customized ablation should be carefully considered, especially in eyes of presbyopic age.

Light scattering and optical aberrations as objective parameters to predict visual deterioration in eyes with cataracts.

PURPOSE: To predict the visual deterioration of eyes with cortical (CC) or nuclear (NC) cataract from objective data on ocular higher-order aberration (HOA) and forward (FLS) and backward light scattering (BLS). SETTING: Osaka University Medical School, Osaka, Japan. METHODS: Twenty-two eyes with mild NC, 41 eyes with mild CC, and 11 normal eyes were examined. Higher-order aberrations were calculated with the Zernike polynomials up to the fourth order from the values obtained by wavefront analysis using the Hartmann-Shack aberrometer. Forward light scattering was calculated from the size of the aberrometer spot images for the central 4 mm, and backward light scattering (BLS) was calculated from the optical density of the Scheimpflug images. The relationship between the area under the log contrast sensitivity function (AULCSF) curve and HOAs, FLS, and BLS was examined. RESULTS: Area under the log contrast sensitivity function was moderately correlated with the HOAs, FLS, and BLS. Multiple linear regression analysis revealed that the AULCSF was predicted by the linear combination of these variables (R(2)=.484, P<.001). Area under the log contrast sensitivity was predicted by BLS and HOA (R(2)=.555) in the NC group and by FLS and HOAs (R(2)=.540) in the CC group. CONCLUSIONS: Loss of contrast sensitivity was predominantly due to BLS and HOA in eyes with NC and FLS and HOA in eyes with CC. Higher-order aberrations, FLS, and BLS, variables that are obtained objectively, can be used to predict quantitatively the visual deterioration in cataractous eyes.

Wavefront analysis of an eye with monocular triplopia and nuclear cataract.

PURPOSE: To determine whether higher-order aberrations explain patient-reported monocular triplopia. DESIGN: Observational case report. METHOD: A patient complaining of monocular triplopia was examined with a Hartmann-Shack aberrometer to determine whether higher-order wavefront aberrations could account for the triplopia. The patient had a mild nuclear cataract; measurements were made before and after lensectomy. The retinal image was simulated using the Zernike polynomials. RESULT: Spherical aberration (-0.18 microm, 4 mm pupil) and trefoil aberration (-0.16 microm) were increased. The simulated retinal image had a triple configuration similar to the subjective image reported by the patient. After cataract surgery, the subjective triplopia disappeared; spherical, and trefoil aberrations were markedly decreased. CONCLUSION: The monocular triplopia probably stemmed from combined effects of spherical and trefoil aberrations caused by the nuclear cataract.

Wavefront analysis in eyes with accommodative spasm.

PURPOSE: To investigate changes of spherical aberration in eyes with accommodative spasm. DESIGN: Case reports. METHODS: Four eyes of two patients with accommodative spasm were studied. Ocular spherical aberration was measured with a Hartmann-Shack wavefront aberrometer for the central 4-mm zone. RESULTS: The root mean square values of spherical aberration were negative (-0.086 +/- 0.026 microm root mean square). However, when the spasm of accommodation was cured or treated with a cycloplegic agent, the value shifted toward positivity (0.025 +/- 0.004 microm root mean square). CONCLUSIONS: Excessive accommodative tone is manifested objectively by negative spherical aberration in eyes with accommodative spasm.

Comparison of ocular higher-order aberrations and visual performance between photorefractive keratectomy and laser in situ keratomileusis for myopia.

The purpose was to compare the ocular higher-order aberrations and the visual performance between photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Ocular aberrations and visual performance were measured after PRK in 26 eyes, after LASIK in 39 eyes, and in 29 normal myopic control eyes. Ocular aberrations were measured with a Hartmann-Shack aberrometer. Visual performance was evaluated with grating contrast sensitivity, high and low contrast visual acuity, and letter contrast sensitivity under full correction with spectacles. The results were that the root mean square (RMS) values of ocular higher-order aberrations after PRK or LASIK were significantly greater than that of normal controls for both 4-mm and 6-mm zones (PRK; 0.22 +/- 0.09 and 0.85 +/- 0.24 microm, LASIK; 0.20 +/- 0.06 and 0.82 +/- 0.24 microm, normal; 0.10 +/- 0.03 and 0.33 +/- 0.11 microm. P < 0.05 between PRK and normal, LASIK and normal, One Way ANOVA on Ranks). There were no significant differences between PRK and LASIK. The ocular higher-order aberrations increased in proportion with the attempted refractive correction by PRK and LASIK. The ocular higher-order aberrations correlated better with grating contrast sensitivity, low contrast visual acuity, and letter contrast sensitivity than with high contrast visual acuity. There was no difference among normal, PRK and LASIK in all the visual function tests, except between normal and PRK, or between normal and LASIK with letter contrast sensitivity. In conclusion, there was no difference in both ocular higher-order aberrations and visual performance between PRK and LASIK. The result suggests that surgeons can choose refractive procedures according to the corneal conditions or daily activities of patients.

Changes of ocular aberration with accommodation.

PURPOSE: To study the effect of accommodation on ocular aberrations. DESIGN: Observational case series. METHODS: The ocular aberrations in 33 eyes of 33 young adults were measured with a Hartmann-Shack wavefront aberrometer before and during 3 diopters of accommodation. RESULTS: The root mean square values of wavefront error did not change for a 4-mm and a 6-mm zone; however, spherical aberration changed significantly toward negativity for both the 4-mm zone (P <.001) and 6-mm zone (P =.022). CONCLUSIONS: During accommodation, the significant change in spherical aberration occurs without a change of image quality. Therefore, for customized aberration, it may not be advantageous to eliminate the physiologic spherical aberration for far vision.

Wavefront aberrations measured with Hartmann-Shack sensor in patients with keratoconus.

OBJECTIVE: To compare the ocular wavefront aberrations of normal and keratoconic eyes and to describe the characteristics of the higher-order aberrations in eyes with keratoconus. DESIGN: Prospective case control and observational study. PARTICIPANTS: Thirty-five keratoconic eyes and thirty-eight normal controls. METHODS: Higher-order aberrations in refraction were measured with a wavefront sensor, and those aberrations resulting from the cornea were evaluated by videokeratographic data. MAIN OUTCOME MEASURES: Coma-like (S(3 + 5)), spherical-like (S(4 + 6)), and total (S(3 + 4 + 5 + 6)) higher-order aberrations in both refraction and the cornea. RESULTS: The mean +/- standard deviation of S(3 + 5) (1.88 +/- 1.16), S(4 + 6) (0.70 +/- 0.55), and S(3 + 4 + 5 + 6) (2.03 +/- 1.23) in refraction (6-mm diameter, root mean square, micro m) were significantly higher in the keratoconic eyes than in normal controls (0.26 +/- 0.10, 0.19 +/- 0.10, 0.34 +/- 0.11, respectively; Mann-Whitney U test, P = 0.001). Coma-like aberrations were 2.32 times larger than spherical-like aberrations in keratoconic eyes. CONCLUSIONS: The increase of ocular higher-order aberrations in keratoconic eyes results from an increase of corneal higher-order aberrations. Coma-like aberrations were dominant compared with spherical-like aberrations in keratoconic eyes. Wavefront sensing will enable us not only to evaluate the quality of vision but also to differentiate keratoconic eyes from normal eyes by analyzing the characteristics of the higher-order aberrations.

Effect of aging on ocular light scatter and higher order aberrations.

PURPOSE: To study the effect of aging on ocular light scatter and higher order aberrations in humans. METHODS: Seventy-six eyes of 76 normal subjects who had refractive errors but no ocular disease were studied. Their age ranged from 4 to 69 years (mean 34.8 +/- 5.8 yr). Both light scatter and total higher order aberrations were simultaneously and quantitatively measured by a Hartmann-Shack sensor for the central 4-mm-diameter pupil. Higher order aberrations were calculated from the Zernike polynomials up to the 4th order. The amount of light scatter was estimated by using the diameter of the point spread functions (PSFs) of the Hartmann images. A correction was made for the effect of the aberrations on the width of the images. Linear regression analysis was performed to investigate the effect of aging on light scatter and total higher order aberrations. RESULTS: A significant correlation was found between scatter and age (Spearman rank correlation coefficient, r = 0.501, P = .001). Also, the total higher order aberrations increased significantly with age (r = 0.323, P = .005). The total higher order aberration and scatter index were not statistically significantly correlated (r = 0.184, P = .112). CONCLUSIONS: These results indicate that scatter was better correlated with age than higher order aberrations.

Standardized color-coded scales for anterior and posterior elevation maps of scanning slit corneal topography.

PURPOSE: To find the most appropriate color-coded scales for the anterior and posterior elevation maps of scanning slit topography in the screening of abnormal corneas such as keratoconus. DESIGN: Retrospective case-control study. PARTICIPANTS: Eighty eyes of 40 normal subjects and 175 eyes of 95 patients with keratoconus. INTERVENTION: Anterior and posterior corneal elevations were assessed using Orbscan 2. Best-fit sphere maps were drawn with several color-coded scales: 2-, 5-, 10-, and 20-microm height per each color interval. MAIN OUTCOME MEASURES: The maps were judged to be abnormal when more than three colors (discriminant number) were found within the central 3-mm area. For each color-coded scale, sensitivity, specificity, positive predictive value, negative predictive value, and sensitivity + specificity were calculated. After determining the most appropriate color-coded scales for the anterior and posterior elevation maps, validity of the discriminant number was assessed. By varying the discriminant number from two to eight, receiver operator characteristic (ROC) curves were created using the sensitivity and specificity for each threshold number. RESULTS: The highest sensitivity + specificity values and highly balanced predictive values were obtained with the 10- and 20-microm scales for the anterior and posterior elevation maps, respectively. The ROC curve analyses showed that the best discriminant color number is three, indicating that maps with four or more colors within the central 3-mm area are judged abnormal in screening. CONCLUSIONS: The 10- and 20-microm interval color scales are most appropriate for the anterior and posterior elevation maps of the scanning slit topography, respectively.

Wavefront analysis in eyes with nuclear or cortical cataract.

PURPOSE: To compare the higher-order aberrations of the oculus (whole eye) and cornea in eyes with mild cortical or nuclear cataract and to estimate the effect of ocular higher-order aberrations on the loss of contrast sensitivity using wavefront analysis. DESIGN: Observational case series. METHODS: Six eyes of four patients with mild nuclear cataract, 18 eyes of 14 patients with mild cortical cataract, and nine eyes of nine normal patients were examined. Wavefront aberrations of the oculus and cornea for central 6 mm diameter were measured using the Hartmann-Shack (HS) aberrometer. Higher-order aberrations were calculated with Zernike polynomials up to sixth order. The relationship between average lens density (ALD) measured by the Scheimpflug camera and the ocular total higher-order aberration (OTHA) was investigated. The relationship between contrast sensitivity (CS) and the OTHA or ALD was also examined. RESULTS: The OTHA was significantly larger in cataracts compared with normal subjects, while corneal total higher-order aberration did not differ between cataracts and normal subjects. The polarity of spherical aberration was negative in all eyes with nuclear cataract while positive in all eyes with cortical cataract. The correlation between ALD and OTHA was not significant in eyes with cataracts. The CS highly correlated with OTHA while it moderately correlated with ALD. CONCLUSIONS: The HS aberrometer is useful to objectively evaluate the deterioration of images in eyes with mild cataract and it revealed that the polarity of spherical aberration was different between nuclear and cortical cataract. It was also suggested that in mild nuclear or cortical cataract, not only light scattering, but also optical aberration of the lens contributes to the loss of contrast sensitivity.

Effect of tear film break-up on higher-order aberrations measured with wavefront sensor.

PURPOSE: To investigate whether optical wavefront aberrations vary with tear film break-up. DESIGN: Observational case series. METHODS: Higher-order aberrations were examined for 20 eyes of 20 normal subjects with a Hartmann-Shack wavefront sensor before and after tear film break-up. RESULTS: Higher-order aberrations for photopic vision (central 4 mm diameter) after tear film break-up increased 1.44 fold compared to higher-order aberrations before tear film break-up (P =.001, paired t-test). Higher-order aberrations after tear film break-up for scotopic vision (central 6 mm diameter) were also 1.23 times higher than those before break-up (P =.005, paired t-test). CONCLUSION: Wavefront sensing enabled us to evaluate the induced irregular astigmatism caused by tear film break-up quantitatively. Wavefront aberrations should be measured carefully to avoid the effects of tear film break-up, especially in wavefront-guided refractive surgery.

Wavefront analysis of higher-order aberrations in patients with cataract.

PURPOSE: To determine local refractive changes and higher-order aberrations in patients with nuclear or cortical cataract. SETTING: Osaka University Medical School, Osaka, Japan. METHODS: Wavefront analysis of both ocular and corneal aberrations was performed with the Hartmann-Shack aberrometer in 2 patients, a 22-year-old woman with bilateral developmental nuclear cataract and a 68-year-old woman with mild bilateral cortical cataract. RESULTS: Case 1 showed a delay in the wavefront that caused a myopic shift in the central pupillary area in both eyes, associated with the nuclear cataract. The spherical-like aberration (right eye, 36%; left eye, 21%) was greater than the coma-like aberration in both eyes. Case 2 showed an advancement of the wavefront that caused a hyperopic shift, especially in the lower temporal pupillary area, that was associated with the cortical cataract. The coma-like aberration (right eye, 63%; left eye, 52%) was greater than the spherical-like aberration in both eyes. The polarity of the third-order spherical aberration was negative in Case 1 and positive in Case 2. Corneal higher-order aberrations were small and had a different distribution than ocular higher-order aberrations in both patients. CONCLUSIONS: The Hartmann-Shack aberrometer was useful in detecting local refractive changes and higher-order aberrations in patients with mild cataract. The polarity and the absolute value of ocular higher-order aberrations may be useful parameters to characterize eyes with cataract.