Biomedical subjects

Tatsuro Tanabe

Publications and source records attributed to Tatsuro Tanabe.

9 recordsLinked to original sources

PubMed2005

Corneal barrier function, tear film stability, and corneal sensation after photorefractive keratectomy and laser in situ keratomileusis.

PURPOSE: To compare corneal sensation, corneal barrier function, tear secretion, and tear film stability after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). DESIGN: Prospective, nonrandomized clinical trial. METHODS: In a prospective study, 28 eyes of 15 patients underwent PRK and 115 eyes of 59 patients underwent LASIK to correct myopia. Corneal sensation, corneal epithelial barrier function, tear secretion, and tear film stability were examined preoperatively and 1 week and 1, 3, 6, and 12 months postsurgery. RESULTS: Both PRK and LASIK significantly compromised corneal sensation, increased epithelial barrier function, reduced tear secretion, and deteriorated tear film stability (P < .05, Wilcoxon signed-rank test). Deterioration of corneal sensation was significantly greater after LASIK than after PRK by 3 months postoperatively (P < .05, Wilcoxon rank sum test). Increases in corneal epithelial permeability were more prolonged after LASIK than after PRK. A significant intergroup difference in permeability was observed 1 month after surgery (P < .01). Tear breakup time was significantly shorter in the LASIK group than in the PRK group up to 3 months after surgery (P < .045). CONCLUSIONS: LASIK induces greater and more prolonged damage to corneal sensation, corneal barrier function, and tear film stability than PRK.

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

Corneal epithelial barrier function in diabetic patients.

PURPOSE: To evaluate the corneal epithelial barrier function in diabetic patients. METHODS: In 29 eyes of 29 diabetic patients and 55 eyes of 55 nondiabetic controls, corneal epithelial permeability to fluorescein was measured using an anterior fluorophotometer. The average fluorescein concentration in the central cornea was compared between diabetic patients and controls. Multiple regression analysis was used to assess the factors that affect corneal epithelial barrier function in diabetic patients. RESULTS: The average fluorescein concentrations in diabetic patients and nondiabetic controls were 44.1 +/- 25.3 ng/mL and 29.9 +/- 19.8 ng/mL (mean +/- SD), respectively (P = 0.0057, unpaired t test). An explanatory variable relevant to the impaired corneal epithelial barrier function was the serum hemoglobin A1c (HbA1c) concentration (standardized partial regression coefficient = 0.466, P = 0.0163). CONCLUSIONS: The corneal epithelial barrier function is impaired in diabetic patients. Diabetic patients with higher serum HbA1c levels are more predisposed to impaired barrier function in the corneal epithelium.

Aged↗

PubMed2003

Difference map or single elevation map in the evaluation of corneal forward shift after LASIK.

PURPOSE: Forward shift of the cornea after excimer laser refractive surgery has been assessed on a difference map generated from two elevation maps of the scanning-slit corneal topography. The current study was conducted to test whether similar evaluation is possible on a postoperative color-coded elevation map alone. DESIGN: Prospective, noncomparative case series. PARTICIPANTS: One hundred sixty-three eyes of 86 patients with myopic refractive errors of -1 to -13.50 diopters. INTERVENTION: LASIK was performed. Corneal topography of the posterior corneal surface was obtained with the scanning-slit topography system before and 1 month after surgery. MAIN OUTCOME MEASURES: The amount of forward shift of the posterior corneal surface was determined at the center of the difference map generated from preoperative and postoperative elevation maps. For surface alignment in the difference map, the 3-mm wide peripheral annular fit-zone was used. The eyes were classified into two groups depending on the amount of forward shift, using 50 micro m as the threshold. Next, on the single postoperative color-coded elevation map, which is drawn relative to the individual best-fit sphere, the eye was judged to be abnormal (with significant forward shift) when more than three colors (discriminant number) were found within the central 3-mm area, and sensitivity and specificity were calculated. By varying the discriminant number from 3 to 9, receiver operator characteristic (ROC) curves were created. RESULTS: The ROC curve analyses demonstrated that sufficient true positive ratio (sensitivity) and false-positive ratio (100-specificity [%]) could not be obtained with any discriminant color number when judgments were made on a single color-coded map. There was a weak, but significant, correlation between the amount of corneal forward shift and the radius of curvature of the posterior best-fit sphere (Pearson r = -0.170; P = 0.030), indicating that a cornea with greater forward shift tended to be drawn on a steeper best-fit sphere, and thus the forward protrusion of the posterior surface failed to be depicted. CONCLUSIONS: Forward shift of the cornea after excimer laser surgery should be evaluated on the difference map generated from two elevation maps, such as preoperative and postoperative maps.

Adult↗

PubMed2002

Time course of changes in corneal forward shift after excimer laser photorefractive keratectomy.

BACKGROUND: Excimer laser refractive surgery has been reported to induce forward shift of the cornea, but its long-term sequelae remain unknown. OBJECTIVES: To prospectively investigate the time course of changes in corneal elevation after excimer laser photorefractive keratectomy (PRK). METHODS: We performed PRK on 65 eyes of 34 patients with refractive errors of -1.25 to -10.0 diopters. The anterior/posterior corneal elevation and corneal thickness were measured with a scanning-slit corneal topography system before and 1 week and 1, 3, 6, and 12 months after surgery. Twenty eyes of 10 healthy control subjects underwent similar measurements at 3-month intervals. RESULTS: The posterior corneal surface displayed a mean +/- SD forward shift of 36.6 +/- 25.3 microm 1 week after PRK, which gradually increased to 55.1 +/- 46.1 microm at 1 year. All postoperative values were significantly larger than those of healthy controls (2.4 +/- 8.9 microm; P<.001, Mann-Whitney test). The largest forward shift occurred within the first postoperative week. The progression thereafter was most pronounced from 1 to 6 months, and nearly stabilized at 6 months. The variance of postoperative data was statistically significant (P<.001, repeated-measures analysis of variance). Multiple postoperative comparisons demonstrated significant differences between measurements at 1 week and 6 months (P =.002, Tukey Honestly Significant Difference), at 1 week and 1 year (P<.001), at 1 and 6 months (P<.001), and at 1 month and 1 year (P<.001). Progression of forward shift was more prominent in eyes with less preoperative corneal thickness and greater myopia that required larger laser ablation. We observed no progressive thinning and expansion of the cornea during the 1-year follow-up, which refuted the occurrence of true ectasia. A statistically significant correlation was found between the amount of myopic regression and the forward shift of the cornea (Pearson correlation coefficient, r = -0.37; P =.005). CONCLUSIONS: Photorefreactive keratectomy induced forward shift of the cornea, which is not true corneal ectasia. The largest forward shift occurred within the first postoperative week. Changes were progressive up to 6 months postoperatively, but became almost stable thereafter. Eyes with thinner cornea and higher myopia, requiring greater photoablation, are more predisposed to progression. Forward shift of both corneal surfaces added to the tendency toward myopic regression after PRK.

Adult↗

PubMed2002

Intracameral air injection for acute hydrops in keratoconus.

PURPOSE: To evaluate the efficacy and safety of intracameral air injection in treating acute hydrops in keratoconus. DESIGN: Retrospective, nonrandomized, comparative trial. METHODS PATIENTS: Thirty eyes (30 patients) with acute hydrops secondary to keratoconus. INTERVENTION: Nine eyes (nine patients) with acute hydrops in keratoconus were treated with intracameral injection of 0.1 ml filtered air. Additional 0.1 ml filtered air was injected if corneal edema persisted when air disappeared from the anterior chamber. Twenty-one eyes (21 patients) with acute hydrops that received no therapy or conventional therapy not likely to shorten the duration of hydrops served as controls. MAIN OUTCOME MEASURES: The period of persistence of corneal edema, the interval between the onset of acute hydrops, and the time when the eye could begin to wear a hard-contact lens, and best spectacle-corrected and hard-contact lens-corrected visual acuity after corneal edema subsided were used as criteria to evaluate any differences between the two groups. RESULTS: The average period of persistence of corneal edema was 20.1 +/- 9.0 days (+/- SD) in the intracameral air injection group and 64.7 +/- 34.6 days in the control (P =.0008). The average interval between the onset of acute hydrops and the time when the eye could begin to wear a hard-contact lens, was 33.4 +/- 5.6 days in the air injection group and 128.9 +/- 85.8 days in the control group (P =.0058). The best-corrected visual acuity after corneal edema subsided was similar between the two groups. Intracameral air injection induced no complications. CONCLUSIONS: The results suggest that the intracameral air injection is a safe and useful therapy to shorten the period of corneal edema in acute hydrops secondary to keratoconus.

Acute Disease↗

PubMed2002

Progression of keratoconus assessed by fourier analysis of videokeratography data.

OBJECTIVE: To quantitatively document changes in corneal refractive parameters in relation to the progression of keratoconus over years. DESIGN: Retrospective observational case series. PARTICIPANTS: Eighty-five eyes of 64 patients with keratoconus who had undergone videokeratography examinations at least twice with an interval of 1 year or longer between each examination. METHODS: By means of Fourier series harmonic analysis, topography data were decomposed into spherical component, regular astigmatism, decentration component, and higher order irregularity. MAIN OUTCOME MEASURES: Change rate of each parameter per year was calculated by use of the least squares method. RESULTS: All four refractive parameters were significantly larger in the keratoconic eyes than in the age-matched normal controls (P < 0.001, Student's t test). The yearly rate of change was significantly positive for spherical component (P = 0.008) and higher order irregular astigmatism (P = 0.015) but not for the regular astigmatism and decentration component. In eyes that showed apparent progression on color-coded maps, spherical component showed a significantly positive change rate per year (P = 0.002), but other parameters did not. In eyes without apparent progression, the yearly change rate of higher order irregular astigmatism was significantly larger than zero (P = 0.049). CONCLUSIONS: Keratoconus progression over years was quantitatively described. It was indicated that spherical equivalent is a manifest indicator for the apparent progression of keratoconus, and irregular astigmatism increases along with the natural course of the disease.

Adolescent↗

PubMed2002

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.

Adolescent↗