Naoyuki Maeda

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 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 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.

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.

Gender- and age-related differences in corneal topography.

Purpose. To investigate gender-and age-related differences in the corneal topography of a normal population. Methods. One hundred thirty-two topographic examinations were collected from 100 patients ranging in age from 23 to 83 years (average, 57.35 ± 17.38 years). Data were segregated by gender and further divided into younger (less than 50 years) and older (50 years or more) age groups. The topographic indices of Surface Regularity Index, Surface Asymmetry Index, Irregular Astigmatism Index, Standard Deviation of Corneal Power, Corneal Eccentricity Index, Coefficient of Variation of Corneal Power, Simulated Keratometry 1 and 2, and Average Corneal Power were examined. The astigmatism pattern and corneal irregularity were determined and compared with respect to gender and age. Results. The corneas of older men were flatter than those of older women (p < 0.001). The vertical corneal meridian, but not the horizontal meridian, showed statistically significant gender-related changes with aging (p < 0.001). Older men had a significantly higher potential for against-the-rule astigmatism than women (p < 0.001). Corneal irregularity (measured in terms of the Surface Regularity Index and Irregular Astigmatism Index) increased with age (p < 0.001 and p < 0.001, respectively), although there was no gender-related difference. In the younger group, no gender-related differences in corneal curvature or astigmatism pattern were found. Conclusion. Aging influences changes in patterns of astigmatism differently in men and women. Decreases in levels of sex hormones may play a role in gender-related changes in corneal structure with age.

Factors that influence the surgical effects of astigmatic keratotomy after cataract surgery

OBJECTIVE To determine the factors affecting the surgical effect of astigmatic keratotomy (AK) when against-the-rule astigmatism is present following cataract surgery. DESIGN Prospective interventional noncomparative case series. PARTICIPANTS Twenty eyes of 19 patients from four medical centers who had against-the-rule astigmatism following cataract surgery. INTERVENTION AK with a 6 mm optical zone, two linear 3-mm length incisions (T-cut) and a depth of 90% of the central thickness was performed on all subjects. MAIN OUTCOME MEASURES Vector analysis of astigmatic correction. Multiple regression analysis for seven covariates including age, spherical equivalent of the manifest refraction, preoperative astigmatism, corneal diameter, corneal thickness, mean radius of corneal curvature and axial misalignment. RESULTS Multiple regression analysis showed that the preoperative astigmatism (p = 0.014) and the axis deviation (p = 0.005) were significantly correlated with the surgical effects. CONCLUSIONS Even with a uniform surgical procedure, the surgical effects of AK in eyes with against-the-rule astigmatism can be affected by the amount of preoperative astigmatism and the intraoperative axis misalignment. Adding the amount of preoperative astigmatism to the nomogram and improvement of surgical procedures will be required to obtain better surgical predictability of AK following cataract surgery.

Wavefront technology in ophthalmology.

Wavefront sensing is an emerging technology that can measure irregular astigmatism as a higher-order wavefront aberration. The application of wavefront sensing in ophthalmology might enable the non-invasive observation of living retinal cone cells; the measurement of detailed visual function of the central nervous system by eliminating higher-order aberrations during examinations by adaptive optics; the correction of irregular astigmatism; and the prevention of iatrogenic irregular astigmatism induced by conventional refractive surgical procedures. In addition, it will be theoretically possible to obtain supernormal vision by wavefront-guided refractive surgery.

Prediction of letter contrast sensitivity using videokeratographic indices

PURPOSE To analyze the relationship between corneal topography and letter contrast sensitivity. METHOD Experiments were conducted on 59 eyes of 51 patients who had best spectacle-corrected visual acuity of 20/20 or better and no ocular pathology except for the corneal shape. Thirty-nine eyes had an abnormal topographic pattern resulting from keratoconus, and the other 20 eyes showed a normal topographic pattern. Videokeratography was performed with the TMS-2 videokeratoscope, and the surface regularity index, surface asymmetry index, and coefficient of variation of power were obtained for each subject. Letter contrast sensitivity was measured with the CSV-1000LV with spectacle correction. The correlation between the number of correct letters and topographic indices was calculated. RESULTS The abnormal topography group had a significantly greater loss of letter contrast sensitivity (median = 20 letters) than the normal control (median = 23 letters; P =.0001). There were statistically significant correlations between number of correct letters and the coefficient of variation of power (r = -.77; P =. 001), number of correct letters and surface regularity index (r = -. 76, P =.001), and the number of correct letters and surface asymmetry index (r = -.64; P =.001). The linear regression equation between number of correct letters and the coefficient of variation of power was the number of correct letters = -0.05 x the coefficient of variation of power + 23.2. CONCLUSIONS Our results suggest that subtle visual deteriorations, which are barely detected by contrast sensitivity testing, can be predicted objectively by the corneal topographic indices.

Comparison of topographic indices that correlate with visual acuity in videokeratography.

OBJECTIVE To evaluate the relationship between the best spectacle-corrected visual acuity (BSCVA) and two quantitative indices of the anterior corneal surface obtained by videokeratography. DESIGN Prospective, single center, comparative, observational study. PARTICIPANTS Eighty-nine normal eyes and 52 eyes with keratoconus with contact lens-corrected visual acuity of 20/20 or better. INTERVENTION Videokeratography was performed with the TMS-2 and the CAS system 2000. MAIN OUTCOME MEASURES The relationship between the BSCVA recorded in log minimal angle of resolution (logMAR) units, the surface regularity index (SRI), and the predicted corneal acuity (PCA) were assessed by linear regression analysis. RESULTS The BSCVAs for all eyes ranged from 0.82 to -0.30 logMAR units. BSCVA was highly correlated with the SRI (r = 0.70, P < 0.0001) and the PCA (r = -0.61, P < 0.0001). There was no statistical difference in the regression slopes and the intercepts for the estimated BSCVA using the SRI and measured BSCVA, and the estimated BSCVA using PCA and measured BSCVA. CONCLUSIONS Two quantitative topographic indices, SRI and PCA, are useful for estimating the effect of irregular astigmatism on visual acuity even though both indices quantify different aspects of the anterior surface of the cornea.