Biomedical subjects

Tomokazu Samejima

Publications and source records attributed to Tomokazu Samejima.

11 recordsLinked to original sources

PubMed2006

Contrast sensitivity function and ocular higher-order wavefront aberrations in normal human eyes.

PURPOSE: To investigate the relation between contrast sensitivity function and ocular higher-order wavefront aberrations in normal human eyes. STUDY DESIGN: Prospective observational case series. PARTICIPANTS: Three hundred seven eyes of 161 normal subjects, ranging in age from 15 to 60 years (30.9+/-8.0 [mean +/- standard deviation]). METHODS: Ocular higher-order aberrations were measured for a 4-mm pupil using the Hartmann-Shack wavefront analyzer. The root-mean-square of the third- and fourth-order Zernike coefficients was used to represent comalike and spherical-like aberrations, respectively. We measured contrast sensitivity, low-contrast visual acuity (VA), and letter contrast sensitivity. From the contrast sensitivity data, the area under the log contrast sensitivity function (AULCSF) was calculated. Pupil diameter in a photopic condition was recorded using a digital camera. RESULTS: Multiple linear regression analysis revealed that comalike aberration (P = 0.002) was significantly associated with AULCSF, but spherical-like aberration (P = 0.200), age (P = 0.185), and photopic pupil diameter (P=0.252) were not. Comalike aberration showed a significant correlation with low-contrast VA (P<0.001), but spherical-like aberration (P = 0.293), age (P = 0.266), and pupil diameter (P = 0.756) did not. Comalike aberration was found to be significantly associated with letter contrast sensitivity (P<0.001), but spherical-like aberration (P=0.082), age (P = 0.370), and pupil diameter (P = 0.160) were not. CONCLUSIONS: In normal human eyes, comalike aberration of the eye significantly influences contrast sensitivity function.

Accommodation, Ocular↗

PubMed2006

Comparison of central corneal thickness measurements by rotating Scheimpflug camera, ultrasonic pachymetry, and scanning-slit corneal topography.

PURPOSE: To compare central corneal thickness measurements and their reproducibility when taken by a rotating Scheimpflug camera, ultrasonic pachymetry, and scanning-slit corneal topography/pachymetry. DESIGN: Experimental study. PARTICIPANTS: Seventy-four eyes of 64 subjects without ocular abnormalities other than cataract. METHODS: Corneal thickness measurements were compared among the 3 methods in 54 eyes of 54 subjects. Two sets of measurements were repeated by a single examiner for each pachymetry in another 10 eyes of 5 subjects, and the intraexaminer repeatability was assessed as the absolute difference of the first and second measurements. Two experienced examiners took one measurement for each pachymetry in another 10 eyes of 5 subjects, and the interexaminer reproducibility was assessed as the absolute difference of the 2 measurements of the first and second examiners. MAIN OUTCOME MEASURES: Central corneal thickness measurements by the 3 methods, absolute difference of the first and second measurements by a single examiner, absolute difference of the 2 measurements by 2 examiners, and relative amount of variation. RESULTS: The average measurements of central corneal thickness by a rotating Scheimpflug camera, scanning-slit topography, and ultrasonic pachymetry were 538+/-31.3 microm, 541+/-40.7 microm, and 545+/-31.3 microm, respectively. There were no statistically significant differences in the measurement results among the 3 methods (P = 0.569, repeated-measures analysis of variance). There was a significant linear correlation between the rotating Scheimpflug camera and ultrasonic pachymetry (r = 0.908, P<0.0001), rotating Scheimpflug camera and scanning-slit topography (r = 0.930, P<0.0001), and ultrasonic pachymetry and scanning-slit topography (r = 0.887, P<0.0001). Ultrasonic pachymetry had the smallest intraexaminer variability, and scanning-slit topography had the largest intraexaminer variability among the 3 methods. There were similar variations in interexaminer reproducibility among the 3 methods. CONCLUSIONS: Mean corneal thicknesses were comparable among rotating Scheimpflug camera, ultrasonic pachymetry, and scanning-slit topography with the acoustic equivalent correction factor. The measurements of the 3 instruments had significant linear correlations with one another, and all methods had highly satisfactory measurement repeatability.

Adult↗

PubMed2006

Influence of pupil diameter on the relation between ocular higher-order aberration and contrast sensitivity after laser in situ keratomileusis.

PURPOSE: To investigate the influence of pupil diameter on the relation between induced changes in ocular higher-order wavefront aberrations and changes in contrast sensitivity by conventional laser in situ keratomileusis (LASIK) for myopia. METHODS: In 215 eyes of 117 patients (age, 33.2 +/- 8.3 years) undergoing LASIK for myopia of -1.25 to -13.5 D (-5.28 +/- 2.55 D), ocular wavefront aberrations and contrast sensitivity function were determined before and 1 month after surgery. Preoperative photopic pupil diameter was measured with a digital camera. Ocular higher-order aberrations were measured for a 4-mm pupil with a Hartmann-Shack wavefront analyzer. The root-mean-square (RMS) of the third- and fourth-order Zernike coefficients was used to represent coma- and spherical-like aberration, respectively. From the contrast-sensitivity data, the area under the log contrast sensitivity function (AULCSF) was calculated. RESULTS: One hundred five eyes had a photopic pupil diameter of 4 mm or larger, and the remaining 110 had a photopic pupil diameter smaller than 4 mm. There were no statistically significant differences in the background clinical data between these two groups. In the eyes with a photopic pupil diameter of 4 mm or larger, the changes in third-order comalike aberrations did not correlate with the changes in AULCSF (Pearson correlation coefficient, r = -0.037, P = 0.723) and 10% low-contrast visual acuity (r = 0.125, P = 0.224), but fourth-order spherical-like aberrations correlated significantly with the changes in AULCSF (r = -0.229, P = 0.024) and 10% low-contrast visual acuity (r = 0.221, P = 0.038). In the eyes with photopic pupil size smaller than 4 mm, there were significant correlations between the changes in comalike aberrations and the changes in AULCSF (r = -0.487, P < 0.001) and 10% low-contrast visual acuity (r = 0.310, P = 0.003), but spherical-like aberrations showed no correlation with the changes in AULCSF (r = -0.078, P = 0.485) and 10% low-contrast visual acuity (r = 0.208, P = 0.158). CONCLUSIONS: In eyes with larger photopic pupil diameter, increases in spherical-like aberration dominantly affect contrast sensitivity, whereas in eyes with smaller pupil size, changes in coma-like aberration exert greater influence on visual performance.

Adolescent↗

PubMed2005

Visual acuity measurements using Fourier series harmonic analysis of videokeratography data in eyes after penetrating keratoplasty.

PURPOSE: Fourier harmonic analysis can decompose videokeratography data into spherical power, regular astigmatism, and irregular astigmatism (asymmetry and higher-order irregularity). The aim of this study was to evaluate whether determination of cylinder power by Fourier analysis facilitates measurements of visual acuity and refraction in eyes after penetrating keratoplasty. DESIGN: Cross-sectional study. PARTICIPANTS: Sixty-six eyes of 56 subjects who had undergone penetrating keratoplasty. METHODS: Spectacle-corrected visual acuity was measured in 2 ways: by the conventional and the Fourier methods. In the conventional method, the refraction was determined subjectively by reference to the measurement results of the autokeratometer and autorefractometer. In the Fourier method, the magnitude and axis of regular astigmatism were calculated by Fourier analysis of the videokeratography data, and spherical lenses were adjusted until best spectacle-corrected visual acuity was attained. MAIN OUTCOME MEASURES: Logarithm of the minimum angle of resolution (logMAR) visual acuity and refraction used for correction. RESULTS: The spectacle-corrected visual acuity obtained with the Fourier method (logMAR, 0.23+/-0.32; Snellen equivalent, 20/34) was significantly better than that attained with the conventional method (logMAR, 0.31+/-0.29; Snellen equivalent, 20/41; P<0.001, paired t test). The cylinder power used for spectacle-corrected visual acuity measurements was significantly lower with the Fourier method (-2.41+/-1.26 diopters [D]) than with the conventional method (-3.53+/-1.64 D; P<0.001). The spherical equivalent at the final refraction was not different between groups (P = 0.207). CONCLUSIONS: Fourier analysis of videokeratography data significantly facilitates determination of refraction and measurement of best spectacle-corrected visual acuity in eyes with corneal irregular astigmatism, such as eyes that have undergone penetrating keratoplasty.

Adolescent↗

PubMed2004

Age-related changes in corneal and ocular higher-order wavefront aberrations.

PURPOSE: To investigate age-related changes in ocular and corneal higher-order wavefront aberrations and elucidate relative contributions of the cornea and the lens in the age-related changes. DESIGN: Observational case series. METHODS: Corneal and ocular higher-order wavefront aberrations in the central 6 mm diameter were measured with videokeratography and the Hartmann-Shack wavefront aberrometer in 75 normal eyes of 75 patients with a mean age of 43.5 +/- 11.7 years (range, 18-69 years). Higher-order wavefront aberrations were calculated with Zernike polynomials up to sixth order. From the Zernike coefficients, we calculated root mean square (RMS) of coma and spherical aberration. To examine age-related changes of the polarity of spherical aberration, the changes of the Zernike coefficient Z(4)(0) was also investigated. RESULTS: Both corneal (r =.307, P =.007) and ocular (r =.334, P =.0033) coma RMS showed positive correlations with age. There was a positive correlation between corneal and ocular coma RMS (r =.468, P <.0001). The RMS of corneal spherical aberration did not change with aging (r =.153, P =.1895), whereas the RMS of ocular spherical aberration had a positive correlation with aging (r =.308, P =.0068). CONCLUSIONS: These results suggest that the ocular coma increases with age, mainly because of the increase in the corneal coma, and the ocular spherical aberration increases with age, mainly because of the increase in the spherical aberration in the internal optics.

Adolescent↗

PubMed2004

Influence of wavefront aberration and corneal subepithelial haze on low-contrast visual acuity after photorefractive keratectomy.

PURPOSE: To assess low-contrast visual acuity (LCVA) after photorefractive keratectomy in relation to ocular higher-order wavefront aberration and corneal subepithelial haze. DESIGN: Prospective, cross-sectional analysis. METHODS: Photorefractive keratectomy was performed in 51 eyes of 27 subjects with myopic refractive error of -2.0 to -10.5 diopters. Ocular higher-order wavefront aberrations for a 4-mm pupil were measured using Topcon Hartmann-Shack wavefront aberrometer, and the extent of corneal subepithelial haze was quantified with Nidek TSPC-3 hazemeter before and 1 month after photorefractive keratectomy. Low-contrast visual acuity was recorded with Vector Vision CSV-1000LanC10% chart. Total higher-order, third-order (coma-like), and fourth-order (spherical-like) aberrations of the eye were determined. The influence of wavefront aberration and corneal subepithelial haze on LCVA was analyzed. RESULTS: Total higher-order, third-order, and fourth-order aberrations significantly increased by surgery (P < .001, Wilcoxon signed rank test). Photorefractive keratectomy induced a significant increase in corneal haze (P < .01), but no case presented severe corneal haze (grade 3 or greater by Fantes grading). By surgery, LCVA was reduced significantly (P < .001). The logarithm of the minimal angle of resolution LCVA showed a significant correlation with total higher-order aberration (Spearman rank correlation coefficient, r(s) = 0.642, P < .0001). Both third-order (r(s) = 0.618, P < .0001) and fourth-order aberrations (r(s) = 0.552, P < .0001) also significantly correlated with logarithm of the minimal angle of resolution LCVA. There was no correlation between the degree of corneal haze and logarithm of the minimal angle of resolution LCVA (r(s) = 0.094, P = .523). CONCLUSIONS: In eyes with mild to moderate corneal haze after photorefractive keratectomy, deterioration of LCVA is mainly attributable to increases in wavefront aberration, and not to corneal haze.

Adolescent↗

PubMed2004

Corneal regular and irregular astigmatism assessed by Fourier analysis of videokeratography data in normal and pathologic eyes.

PURPOSE: To assess corneal regular and irregular astigmatism using Fourier series harmonic analysis of videokeratography data in normal subjects, as well as in subjects with pathologic and postsurgical conditions. STUDY DESIGN: Retrospective, case-control study. PARTICIPANTS: Two hundred normal eyes, 58 eyes with keratoconus, 24 eyes with suspect keratoconus, 100 eyes that underwent LASIK, 101 eyes that underwent photorefractive keratectomy (PRK), and 79 eyes that underwent penetrating keratoplasty (PK). METHODS: Videokeratography data were decomposed, using Fourier analysis, into spherical power, regular astigmatism, asymmetry, and higher order irregularity. RESULTS: The normal range of the Fourier indices was defined as the mean +/-2xstandard deviation in the normal eyes, which were 40.81-47.13 diopters (D) for spherical power, 0-1.04 D for regular astigmatism, 0.02-0.68 D for asymmetry, and 0.05-0.17 for higher order irregularity. The keratoconus and suspect keratoconus groups showed significantly greater values in all indices than did the normal group (P<0.001 or 0.0001, Mann-Whitney test with Bonferroni correction). Eyes that had undergone LASIK and PRK had significantly smaller spherical power and regular astigmatism (P<0.0001) and significantly larger asymmetry (P<0.0001) than the normal eyes. All indices were significantly greater in the PK group than in the normal group (P<0.0001). Among the eyes tested in this study, eyes with keratoconus had the largest asymmetry, whereas eyes that had undergone PK had the most irregular corneas. CONCLUSIONS: The normal range was defined for the corneal irregular astigmatism index (asymmetry and higher order irregularity) to support future studies in this field. Eyes with ocular pathologic and postsurgical conditions were evaluated using the normal range.

Adolescent↗

PubMed2004

Ocular higher-order aberrations and contrast sensitivity after conventional laser in situ keratomileusis.

PURPOSE: To investigate prospectively the relation between induced changes in higher-order aberrations of the eye and changes in contrast sensitivity by conventional laser in situ keratomileusis (LASIK) for myopia. METHODS: In 200 eyes of 110 consecutive patients (mean age, 32.7 +/- 8.4 years) undergoing LASIK, ocular aberrations and contrast sensitivity function were determined before and 1 month after surgery. The amount of myopic correction was 5.2 +/- 2.8 D (range, 1.0-13.0). Ocular higher-order aberrations were measured for a 4-mm pupil using the Hartmann-Shack wavefront analyzer (KR-9000PW; Topcon, Tokyo, Japan). The root mean square (RMS) of the third- and fourth-order Zernike coefficients was used to represent coma- and spherical-like aberrations, respectively. Total higher-order aberrations were calculated as the RMS of the third- and fourth-order coefficients. Contrast sensitivity and low-contrast visual acuity were measured. From the contrast sensitivity data, the area under the log contrast sensitivity function (AULCSF) was calculated. RESULTS: LASIK significantly improved logMAR best corrected visual acuity (Wilcoxon signed-rank test, P <0.001), but significantly reduced AULCSF (P <0.001) and low-contrast visual acuity (P=0.007). Total higher-order (P <0.001), coma-like (P <0.001), and spherical-like (P <0.001) aberrations were significantly increased after LASIK. The greater the amount of achieved myopia correction was, the more the changes in contrast sensitivity function and ocular higher-order aberrations were. The induced changes in AULCSF by LASIK showed significant correlations with changes in total higher-order (Pearson r=-0.221, P=0.003), coma-like (r=-0.205, P=0.006), and spherical-like (r=-0.171, P=0.022) aberrations. The changes in logMAR low-contrast visual acuity by surgery significantly correlated with changes in total higher-order (r=0.222, P=0.003), coma-like (r=0.201, P=0.007), and spherical-like (r=0.207, P=0.005) aberrations. CONCLUSIONS: Conventional LASIK significantly increases ocular higher-order aberrations, which compromise the postoperative contrast sensitivity function.

Adolescent↗

PubMed2004

[Results of surgery on white cataract using trypan blue capsule staining to visualize capsulorrhexis].

PURPOSE: To evaluate surgery on white cataracts using trypan blue capsule staining. METHODS: A retrospective study comprised 64 eyes of 60 patients with white cataract that had surgery with trypan blue capsule staining. The average age was 62.4 years and progress observation periods were 5.6 months. The rate of successful continuous curvilinear capsulorrhexis(CCC), complications, visual acuity, intraocular pressure(IOP), flare value, and corneal endothelial cell loss were studied. RESULTS: The CCC was completed uneventfully in 93.8% eyes. Posterior capsule rupture occurred in 2 eyes, and early perforation in 1 eye. Accidental vitreous staining and endothelial staining with trypan blue were observed in 1 eye each. There were no postoperative complications associated with trypan blue. Forty-five eyes had a best corrected visual acuity of 0.8 or better at the last visit. Twelve eyes had some ocular pathology resulting in visual loss, and a reliable visual acuity test could not be performed in 6 eyes. The mean postoperative IOP was within the normal range. The mean postoperative flare returned to within normal range 1 month after surgery. The mean corneal endothelial loss was 13.7%, and that of eyes with nucleus of grade 2 or softer was only 2.9%. CONCLUSIONS: Cataract surgery using trypan blue was safe and effective in managing white cataracts.

Adolescent↗

PubMed2002

Higher order wavefront aberrations of cornea and magnitude of refractive correction in laser in situ keratomileusis.

OBJECTIVE: To assess the relation between magnitude of refractive correction and changes in higher order wavefront aberrations of the cornea after laser in situ keratomileusis. DESIGN: Prospective, consecutive, nonrandomized comparative trial (self-controlled). PARTICIPANTS: One hundred eyes of 53 patients with myopia (-2.0 to -13.0 diopters) were included. INTERVENTION: Laser in situ keratomileusis was performed. Videokeratography measurements were conducted before and 1 month after surgery. MAIN OUTCOME MEASURES: The videokeratography data were used to calculate the higher order wavefront aberrations of the cornea for both small (3 mm) and large (6 mm) pupils. RESULTS: For a 3-mm pupil, the surgery significantly increased coma-like (2.4 +/- 1.3-fold, P < 0.001, paired t test) and spherical-like (1.8 +/- 0.9-fold, P < 0.001) aberrations. For a 6-mm pupil, both coma-like (4.4 +/- 3.3-fold, P < 0.001) and spherical-like (9.4 +/- 5.2-fold, P < 0.001) aberrations were significantly increased by surgery. The amount of achieved correction showed significant correlations with the changes in coma-like (Pearson correlation coefficient r = 0.446, P < 0.001) and spherical-like (r = 0.348, P < 0.001) aberrations for a 3-mm pupil, and coma-like (r = 0.566, P < 0.001) and spherical-like (r = 0.693, P < 0.001) aberrations for a 6-mm pupil. The eyes that lost 2 or more lines of baseline spectacle-corrected visual acuity showed significantly larger induced increases in coma-like (P = 0.003, Mann-Whitney U test) and spherical-like (P = 0.009) aberrations for a 3-mm pupil than those that either improved or remained within 1 line of spectacle-corrected visual acuity CONCLUSIONS: Laser in situ keratomileusis, performed using the current algorithms, increases higher order wavefront aberrations of the cornea, dependent on the amount of refractive correction.

Adult↗

PubMed2002

Corneal endothelial cell protection during phacoemulsification: low- versus high-molecular-weight sodium hyaluronate.

PURPOSE: To compare the efficacy of low- and high-molecular-weight sodium hyaluronate in protecting corneal endothelial cells during phacoemulsification. SETTING: Miyata Eye Hospital, Miyakonojo, Miyazaki, Japan. METHODS: One hundred forty-nine eyes of 136 cataract patients were randomly assigned to have cataract surgery using sodium hyaluronate 1% with a low molecular weight (0.6 to 1.2 million d, Opegan) or sodium hyaluronate 1% with a high molecular weight (4 million d, Healon) during phacoemulsification. Each group was divided into 2 subgroups depending on the amount of ultrasound (% min) used during phacoemulsification, which was defined as the mean phacoemulsification energy (%) multiplied by phacoemulsification time (minutes). Corneal endothelial cell density was examined preoperatively and 3 months after surgery. The rate of cell loss was compared between the subgroups in the Opegan group and the Healon group. RESULTS: In the subgroups with ultrasound of 50% min or less, the mean rate of endothelial cell loss 3 months after surgery was 3.2% +/- 4.1% (SD) in the Opegan group and 5.9% +/- 5.3% in the Healon group (P =.0214). In the subgroups with ultrasound over 50% min, the mean rate of endothelial cell loss 3 months after surgery was 7.5% +/- 10.6% in the Opegan group and 14.8 +/- 9.0% in the Healon group (P =.0029). CONCLUSIONS: The results suggest that Opegan is more effective than Healon in protecting corneal endothelial cells during phacoemulsification regardless of the amount of ultrasound energy used.

Aged↗