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Biomedical subjects

Naoyuki Maeda

Publications and source records attributed to Naoyuki Maeda.

45 records · Page 3Linked to original sources
PubMed2002

Recurrence of corneal dystrophy resulting from an R124H Big-h3 mutation after phototherapeutic keratectomy.

PURPOSE: The purpose of the study was to investigate the recurrence-free interval after phototherapeutic keratectomy (PTK) in patients with corneal dystrophies resulting from an Arg124His (R124H) mutation of the Big-h3 gene. METHODS: Patients with corneal dystrophy resulting from a genetically confirmed Big-h3 R124H mutation were examined with a slit lamp. The patients were divided into two groups on the basis of the mutation genotype, and the recurrence-free interval was analyzed. RESULTS: In the 4 eyes of 3 homozygous patients, the mean (+/- standard deviation [SD]) recurrence-free interval was 9.5 +/- 3.1 months, whereas in the 7 eyes of 4 heterozygous patients it was 38.4 +/- 6.2 months. The former interval was statistically shorter than the latter (Kaplan-Meier survival analysis with log-rank test, p = 0.004). CONCLUSIONS: These results strongly suggest that the mutation genotype of Big-h3 gene determined the recurrence-free interval as well as the clinical picture after PTK. Therefore, PTK should be considered for patients with Big-h3 R124H corneal dystrophy, on the basis of the expected recurrence-free interval deduced from molecular analysis of the zygosity of the Big-h3 R124H mutation.

Adult↗
PubMed2002

Evaluation of optical quality of corneas using corneal topographers.

PURPOSE: To review the evaluation of the optical quality of the cornea by corneal topography. METHODS AND RESULTS: Color-coded maps show qualitatively the characteristics and severity of irregular astigmatism at the entrance pupil. Topographic indices such as the surface regularity index and predicted corneal acuity are derived from computation of the corneal power distribution, and they are highly correlated with high-contrast visual acuity. Fourier analysis can be used to represent the irregular and regular astigmatism components simultaneously. Zernike polynomials can be used to calculate higher-order wavefront aberrations due to the corneal surface. CONCLUSION: Evaluation of the optical properties of the cornea using a corneal topographer is useful for assessing quality of vision.

Astigmatism↗
PubMed2002

Apparent accommodation and corneal wavefront aberration in pseudophakic eyes.

PURPOSE: To assess the relationship between apparent accommodation in pseudophakic eyes, multifocal corneal effects, and wavefront aberrations of the cornea. METHODS: In 102 eyes of 86 patients who had undergone phacoemulsification and posterior chamber intraocular lens implantation, the amount of apparent accommodation was measured with an accommodometer. The degree of corneal multifocality was determined on the corneal topography by measuring the maximum and minimum corneal refractive powers within the pupillary area. Wavefront aberrations of the cornea were calculated by expanding the height data of the corneal topography into Zernike polynomials for individual pupil size. The influence of higher-order aberration on the retinal image quality was simulated by computing the point-spread function (PSF) and modulation-transfer function (MTF) from the aberration function. RESULTS: There was a significant positive correlation between the amount of apparent accommodation and corneal multifocality (Pearson correlation coefficient, r = 0.451, P < 0.001). The coma-like aberration showed a significant positive correlation with the amount of apparent accommodation (r = 0.440, P < 0.001), but the spherical-like aberration did not (r = 0.001, P = 0.993). Among the coma-like aberrations, the component representing vertically asymmetrical distribution of corneal refractive power with greater refraction located in the lower part of the eye was most relevant to apparent accommodation. Computer simulation of PSF and MTF indicated that a focus shift of 0.5 D deteriorated the retinal image significantly more in eyes without higher-order aberrations than in eyes with a moderate amount of coma-like aberrations. CONCLUSIONS: Coma-like aberration of the cornea, along with corneal multifocality, contributes to apparent accommodation in pseudophakic eyes.

Accommodation, Ocular↗
PubMedDate not supplied

Tear film break-up time evaluated by real-time Hartmann-Shack wavefront sensing.

PURPOSE: To develop a novel method for measuring tear break-up time (BUT) by continuously measuring higher order wavefront aberrations using a Hartmann-Shack (H-S) aberrometer. METHODS: Wavefront aberrations up to the sixth order for a 4-mm pupil were measured in six eyes of six normal subjects using an H-S aberrometer. The aberrometry was performed once every second for up to 50 s under topical anesthesia. The sequence of the points was divided into two stages, and the BUT was defined as the wavefront border of the stages (WFBUT). The WFBUT was compared with the BUT by the conventional fluorescein method (FLBUT) or by the disruption of placid-ring images (PLBUT). RESULTS: In three eyes, the WFBUT (average, 10.9 +/- 1.1 s) was shorter than the PLBUT (average, 17.5 +/- 2.5 s), while in the other three eyes the WFBUT (average, 21.5 +/- 2.2 s) was longer than PLBUT (average, 8.1 +/- 2.2 s). The FLBUT was shorter than WFBUT or PLBUT in most cases. CONCLUSIONS: The tear break-up time measured by H-S aberrometer may be used as a practical measure of tear break-up.

Adult↗
PubMedDate not supplied

Effects of reference axes used during measurements of ocular and corneal higher-order aberrations in patients following LASIK.

PURPOSE: To determine the effects of the reference axes used during the measurements of ocular and corneal higher-order aberrations (HOAs) in patients before and after laser in situ keratomileusis (LASIK). METHODS: Wavefront sensing and corneal topography were determined for 29 eyes of 15 patients before and after LASIK. Ocular and corneal HOAs were calculated for 4-mm- and 6-mm-diameter pupils with the instrument aligned with the line of sight (LOS) or with the vertex normal (VN). RESULTS: For ocular HOAs after surgery, the spherical-like aberration was significantly larger when the VN axis rather than the LOS axis was used for pupils of both diameters. For corneal HOAs before surgery, in addition to the larger spherical-like aberration for VN, coma-like aberrations were significantly larger with LOS than with VN for both pupil diameters. For corneal HOAs after surgery, the spherical-like aberrations and total HOAs for 4-mm-diameter pupils with VN were significantly larger than those with LOS. CONCLUSIONS: The HOAs were significantly different depending on the axes used and should be described on the basis of a common axis. These results suggest that the anterior surface of the normal or post-LASIK cornea is more rotationally symmetrical along the VN than along the LOS.

Adult↗
PubMedDate not supplied

Intensity analysis of Hartmann-Shack images in cataractous, keratoconic, and normal eyes to investigate light scattering.

PURPOSE: A clinical investigation of novel methods for evaluating light scattering using a Hartmann-Shack aberrometer. METHODS: Aberrometry was performed on normal eyes (n=7; patient age, 26.7+/-2.5 years, mean+/-SD), eyes with keratoconus (n=22; patient age, 26.1+/-8.1 years), and eyes with cataract (n=17; patient age, 56.5+/-16.9 years) using a Hartmann-Shack wavefront aberrometer. We introduced two methods: (1) a contrast method, in which we calculated the inverse of contrast of the local images around 12 spots in a Hartmann-Shack image, and (2) a difference of point spread function (PSF) method, in which we analyzed the difference between the width of the PSF computed with aberration information and the width of the measured PSF, which contains both aberration and light scattering information. RESULTS: The inverse contrast in cataractous eyes (5.04+/-3.06 inverse contrast units) was significantly larger than that in normal eyes (1.57+/-0.56) or keratoconic eyes (1.83+/-0.79). The difference of PSF in cataractous eyes (81.8+/-65.2 microm) was also significantly larger than that in normal eyes (9.3+/-4.3 microm) or keratoconic eyes (30.0+/-20.1 microm). The inverse contrast and the difference in the PSF were highly correlated (r=0.89, P<0.0001). CONCLUSIONS: The two methods introduced here successfully distinguished cataractous eyes from normal and keratoconic eyes. After the results were analyzed by a discriminant analysis, the separation of the three categories proved to be excellent.

Adolescent↗
PubMedDate not supplied

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.

Adult↗
PubMedDate not supplied

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.

Adolescent↗