Self-care activities of pregnancy induced hypertension and maternal outcome.
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Adolescent↗
Biomedical subjects
K Soya
Publications and source records attributed to K Soya.
Objective assessment of transient corneal haze and its relation to visual performance after photorefractive keratectomy.
PURPOSE: Photorefractive keratectomy has the potential to cause transient corneal haze. The purpose of this study was to evaluate the relationship between transient corneal haze as measured by an objective means and high and low contrast visual performance. METHODS: In a prospective study, 44 eyes of 28 patients were examined preoperatively and at 1, 3, 6, and 12 months after photorefractive keratectomy. Five laser in situ keratomileusis and two intrastromal corneal ring segments (Intacs [KeraVision, Fremont, CA]) were included for comparison, because these procedures are not expected to cause haze. Haze was measured using a prototype objective hazemeter, TSPC-3, a modification of the Nidek EAS-1000. Visual performance was measured using high-contrast visual acuity and the Rabin Small Letter Contrast Test. RESULTS: Corneal haze was greatest at the 1-month examination and was consistent with a decrease in visual performance on both tests. Corneal haze resolved in 82% of eyes by 10 +/- 4 months after photorefractive keratectomy. However, visual performance had not returned to preoperative levels in 65% and 81% of these eyes on the high-contrast visual acuity test and the Small Letter Contrast Test, respectively. Eyes that underwent laser in situ keratomileusis and Intacs did not develop corneal haze; however, visual decrements were measured. CONCLUSIONS: As a clinical tool, the TSPC-3 hazemeter objectively measures very subtle changes in haze levels. Corneal haze appears to account for only approximately 50% of visual performance changes in the early healing period after photorefractive keratectomy. Other factors, namely topographic abnormalities, are more likely to be an important cause of persistent visual disturbances.
Contrast Sensitivity↗
Corneal irregular astigmatism and contrast sensitivity after photorefractive keratectomy.
OBJECTIVE: To investigate the relation between contrast sensitivity and corneal irregular astigmatism in eyes after photorefractive keratectomy (PRK). DESIGN: Prospective observational case series. PARTICIPANTS AND CONTROLS: Seventy-nine eyes without corneal haze 6 months or more after PRK and 30 normal control eyes. METHODS: Videokeratography was taken with TMS-1 (Computed Anatomy Inc. New York, NY), and contrast sensitivity for day and night vision was measured using a Multivision Contrast Tester 8000 (Vistech Consultants, Inc., Dayton, OH). MAIN OUTCOME MEASURES: Regular and irregular astigmatism (asymmetry and higher order irregularity components) were computed using Fourier series harmonic analysis of the videokeratography data. Area under the log contrast sensitivity function (AULCSF) was calculated from the contrast sensitivity data taken at five spatial frequencies. RESULTS: After PRK, AULCSFs were significantly smaller for day vision (P = 0.007, unpaired t test) and night vision (P = 0.020) compared with normal controls. AULCSFs for day vision were significantly negatively correlated with asymmetry (Pearson's correlation coefficient, R = -0.23, P = 0.049) and higher order irregularity (R = -0.33, P = 0.004) components but not with the regular astigmatism component (P > 0.3). AULCSF for night vision correlated significantly with asymmetry (R = -0.31, P = 0.013) and higher order irregularity (R = -0.30, P = 0.016) components but not with the regular astigmatism component (P > 0.3). CONCLUSIONS: Corneal irregular astigmatism after PRK significantly influences contrast sensitivity.
Adult↗
Relation between corneal haze and transforming growth factor-beta1 after photorefractive keratectomy and laser in situ keratomileusis.
PURPOSE: To investigate the relation between corneal haze formation and transforming growth factor-beta (TGF-beta) after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). SETTING: Department of Ophthalmology, University of Tokyo Graduate School of Medicine, Tokyo, Japan. METHODS: White rabbits were divided into 4 groups, with each group receiving 1 of the following surgeries: manual epithelial abrasion, PRK, lamellar keratotomy, or LASIK. The degree of corneal haze was quantitatively analyzed by measuring the light scattering intensity of corneas before and 4 and 12 weeks after surgery. The expression of type IV collagen and TGF-beta1 in the corneas at baseline and at 4 weeks was examined immunohistochemically. RESULTS: The light scattering intensity was significantly greater 4 and 10 weeks after PRK. In contrast, epithelial abrasion, lamellar keratotomy, and LASIK did not influence the light scattering intensity of the corneas. Type IV collagen was detected in the basal lamina of the corneal epithelium and in Descement's membrane in the normal cornea. After epithelial abrasion, there was no change in the distribution of type IV collagen. Four weeks after PRK, the expression of type IV collagen was detected in the subepithelial layer of the laser-ablated area. Four weeks after lamellar keratotomy, type IV collagen was linearly and fragmentarily detected in the corneal stroma. Four weeks after LASIK, type IV collagen was linearly and continuously detected in the corneal stroma and was detected slightly in the subepithelial region of the laser-ablated area. In the normal corneas, the expression of TGF-beta1 was not detected in the keratocytes. Four weeks after PRK, the expression of TGF-beta1 increased in the keratocytes that proliferated in the subepithelial fibrous layer. In contrast, epithelial abrasion, lamellar keratotomy, and LASIK did not change the expression pattern of TGF-beta1 in the keratocytes. CONCLUSION: The multiplier effect of epithelial abrasion and excimer laser ablation in PRK may increase the expression of TGF-beta1 in keratocytes and induce corneal haze.
Animals↗
Effect of donor age on morphologic variation of cultured human corneal endothelial cells.
PURPOSE: To examine the effect of donor age on the morphologic variation of cultured human corneal endothelial cells (HCEC). METHODS: HCEC were obtained from the remaining corneoscleral rims of seven human corneas used for penetrating keratoplasty. The donor age ranged from 2 to 75 years. Primary cultures were established from explants of the endothelial cell layer, including the Descemet's membrane, and were propagated on culture dishes coated with bovine corneal endothelial extracellular matrix. At the fourth passage, frequency distribution of cell area in the confluent monolayer was calculated and the effect of donor age on cell area was analyzed. RESULTS: The percentage of HCEC with cell area over 2000 microm2 significantly increased with donor age (r = 0.935, p = 0.0007). CONCLUSION: Cultured HCEC established from older donor tissue display greater heterogeneity. The use of HCEC from younger donors may be preferable to maximize the benefits of HCEC transplantation.
Adolescent↗
Three-dimensional organization of collagen fibrils during corneal stromal wound healing after excimer laser keratectomy.
PURPOSE: To investigate the structural changes in corneal stromal collagen fibrils after excimer laser keratectomy in relation to the degree of corneal haze. SETTING: University of Tokyo Hospital, Tokyo, Japan. METHODS: Corneal haze was quantitatively measured by analyzing the light scattering in Scheimpflug images of the corneas of white rabbits after excimer laser keratectomy. Collagen fibril structure was examined using scanning electron microscopy after chemical digestion with sodium hydroxide solution; the same specimens were examined by transmission electron microscopy after re-embedding. RESULTS: Corneal haze reached a peak 4 weeks after excimer laser keratectomy and then gradually decreased. The collagen fibrils of the normal cornea were regularly arranged parallel to the surface of the cornea, with small interfibrillar distances. After excimer laser keratectomy, the arrangement was highly disordered, with increased interfibrillar distances. These structural changes were most prominent 4 weeks after excimer laser keratectomy. CONCLUSION: The structural changes in the collagen fibrils of the corneal stroma, especially the increase in interfibrillar distances and the disordered arrangement, were associated with corneal haze after excimer laser keratectomy.
Animals↗
Expression of transforming growth factor beta superfamily and their receptors in the corneal stromal wound healing process after excimer laser keratectomy.
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Animals↗
[Effects of topical corticosteroids on subepithelial haze after excimer laser corneal surgery--objective and quantitative method for evaluating haze].
To examine the effectiveness of topical corticosteroids in decreasing subepithelial haze induced by excimer laser keratectomy, we performed excimer laser keratectomy on 24 eyes of 12 albino rabbits using a scanning excimer laser system (EC-5000, NIDEK, Japan). Topical dexamethasone 0.1% was applied topically to 8 corneas after surgery (steroid group), but not to the others (control group). Slit-lamp biomicroscopic examination and objective measurement of scattered light from subepithelial haze were performed before and 2, 4, 8 and 12 weeks after surgery, the rabbits were killed after 2 or 12 weeks and the eyes were examined histologically. In both groups, densitometric values of scattered light intensity increased up to 4 weeks after surgery, and then decreased gradually. However, the values of the steroid group were larger than those of the control group at all stages, and the values of the steroid group at 12 weeks after surgery were similar to preoperative values. There was statistically significant difference in scattered light intensity between the two groups (p < 0.005). Two weeks after surgery, the corneas of the control group showed epithelial hyperplasia and a remarkable increase in activated keratocytes and subepithelial fibrous tissues. However, in the steroid group these light microscopic findings could not be observed. At 12 weeks after surgery, the corneas of the control group retained a small amount of activated keratocytes and fibrous tissues, and those of the steroid group were normal. This study suggests that a short course of topical corticosteroids may be very effective in decreasing subepithelial haze after excimer laser corneal surgery.
Administration, Topical↗
[Corneal distortion induced by speculum--studies with computer-assisted corneal topography].
The corneal distortion induced by the presence of an eyelid speculum was analysed by the Videokeratoscope-Eyesys Corneal Analysis System (EYESYS), with a Barraquer type speculum (B group) in 22 normal eyes and with a Kratz-Barraquer type speculum in 38 normal eyes (KB group). The following differences were evaluated in the 2 groups: intraocular pressure (IOP), refractive power, change in astigmatism of the Cravy method, and corneal refractive power before and after the specula were put in the interpalpebral fissure. Significant differences were found in the IOP in the KB group, in spherical equivalent in the B and KB groups, and in corneal refractive power in the B groups. Then the 38 eyes of the KB group were divided into two groups by the average level of proptosis and the average difference of IOP, and the corneal refractive power of the two groups was compared by statistical analysis. Significant difference was found in the direction of 0 degree/ 180 degrees in the group with higher than average proptosis and in the direction of 90 degrees/ 270 degrees in the group with higher than average difference in IOP. Multiple regression analysis suggested that higher grades of proptosis were related with steeper vertical meridians and that wider palpebral fissures were associated with steeper horizontal meridians. Multiple regression also showed that the speculum did not cause corneal distortion with the proper relation between level of proptosis and width of the palpebral fissure.
Adult↗
[Experimental studies on influence of alignment errors on measurement in a corneal topographic system--relationship between degree of measurement error and working distance].
To evaluate the influence of alignment errors in focusing on the results of measurements in corneal topography, we experimented using polymethyl-methacrylate balls with definite radii of curvature as test objects. We used 3 different corneal topographic systems with different working distances to clarify the relationship between the degree of errors and the working distance. We determined the refractive power of the test balls by the topographic systems and studied changes in the values as the balls were slightly displaced from the alignment position axially, or horizontally. The test balls were set on the stage with a micrometer so that the distance of displacement could be determined precisely. When the test balls were placed precisely in alignment, there was no significant relationship in the magnitude of measurement errors with working distance of the topographical systems. When the test balls were displaced axially, the measurement values decreased as the balls come near from the alignment position and increased as they moved away from the alignment position. The magnitude of the measurement errors caused by back and forth displacement of the object became larger as the working distance of the topographic system became shorter. There was no specific relationship between the degree of measurement errors and the working distance when the balls were displaced horizontally.
Cornea↗
[Effects of blowing or aspiration on ablation rate by excimer laser].
Accurate calibration of ablation rate by excimer laser prerequisite for precise photorefractive keratectomy (PRK). When a polymethylmethacrylate (PMMA) plate is ablated by excimer laser, debris is generated, which may affect homogeneity of the laser beam and energy density, and change the ablation rate. In order to clarify the effects of the debris on the ablation rate, we studied the changes in the ablation rate when the debris was removed by blowing or aspirating over the ablation area during PRK.PMMA plates were ablated using a scanning excimer laser system (EC-5000, NIDEK, Japan) in PRK mode under the following conditions: (1) with air blowing over the ablation area, (2) with aspiration of the debris, and (3) without treatment. The ablation rates were determined by measuring the refractive power of PMMA plates with a lens meter. The ablated surface was observed by scanning electron microscope (SEM). The ablation rate with blowing was the highest among the three conditions, that with aspiration was the second, and that without treatment was the lowest. The ablation rates with blowing showed no significant change when the ablation rates were changed. However, the ablation rates with aspiration or without treatment decreased as the pulse rate increased. The surface ablated during blowing was the smoothest in SEM photographs. We concluded that calibration of the ablation rate using PMMA plates must be done with appropriate air blowing.
Calibration↗
[Postgastrectomy hemorrhage].
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Age Factors↗
Quantification of simulated corneal haze by measuring back-scattered light.
The Scheimpflug anterior eye segment analysis system EAS-1000 was modified to specifically quantitate the degree of corneal haze. In order to confirm the basic measurement performance of the new system, TSPC-3 hazemeter, in vitro experiments were conducted. Using white latex microsphere solutions, tests were performed for the linearity of the measurements, the influence of slit lamp illuminance and the influence of the length of the light path through the latex solution. The validity of Beer's law was confirmed, indicating that a sufficiently wide range of latex concentrations (haze intensities) can be covered by the hazemeter. The scattering intensity measured with the hazemeter showed a significant linear correlation with the latex concentration. The obtained scattering intensity was directly proportional to the illuminance of the slit lamp. The ratio of integrated scattering values was proportional to that of the light path length. It was shown that the TSPC-3 hazemeter possesses sufficient capability for a quantitative evaluation of corneal haze.
Calibration↗