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Biomedical subjects

M B Datiles

Publications and source records attributed to M B Datiles.

18 recordsLinked to original sources
PubMed1992

Contrast sensitivity in patients with nuclear cataracts.

Spatial contrast sensitivity and lens density were measured in 30 subjects (18 patients with pure nuclear cataracts and 12 age-matched controls). Contrast sensitivity was assessed using two techniques: a conventional monitor method in which gratings were viewed through the cataract (overall spatial contrast sensitivity) and a laser interferometer method in which gratings were formed directly on the retina (interferometric spatial contrast sensitivity), thus reducing the effect of an opaque lens on grating contrast. The degree of lens nuclear opacity was measured by assessing the density of Zeiss Scheimpflug slit-lamp video camera images. A contrast sensitivity loss was found by using both methods; this reduction reached statistical significance only when monitor stimuli were used. There was a significant correlation between lens nuclear density and sensitivity loss at spatial frequencies from 4 to 16 cycles/degree (r = .56 to .79 and P less than .05 to less than .001). A correlation coefficient of .82 (P less than .001) characterized the relationship between visual acuity (log of the minimal angle of resolution) and lens density. Nuclear lens opacity significantly affects contrast sensitivity; pure nuclear cataracts produce spatial visual losses at intermediate and high spatial frequencies.

Aged↗
PubMed1992

Two-dimensional gel electrophoretic analysis of human lens proteins.

Human lens proteins from clear lenses were separated and identified using two-dimensional polyacrylamide electrophoresis. Isoelectric focusing, both equilibrium and non-equilibrium, was performed in the first dimension and SDS electrophoresis in the second dimension. Proteins were identified by Western blotting and sequencing techniques and by comparison with patterns obtained with purified crystallin fractions. Analyses were performed on total urea soluble proteins of lenses varying in age from fetal to 73 yr. Several hundred protein spots representing crystallins, cytoskeletal proteins and enzymes were resolved in the fetal lens. In the older lenses there was a dramatic increase in the number of protein species in the molecular weight range of the crystallins and a reduced number of discrete protein species visible at molecular weights greater than 50,000. Conversely, a number of proteins below approximately 15 kDa were visible even in the fetal lens. The number and amount of polypeptides in this molecular weight range were increased in the older lenses. Many of these low molecular weight species could be assigned to either the alpha-, beta- or gamma-crystallin fractions. An age dependent increase in the number of acidic species of both crystallins and other proteins, such as, glyceraldehyde 3-phosphate dehydrogenase was observed as well as the loss or mobility change of gamma-crystallin. Two-dimensional gel electrophoresis provides a sensitive and practical technique for characterizing all of the proteins of the human lens.

Adult↗
PubMed1992

Contrast and glare sensitivity. Association with the type and severity of the cataract.

PURPOSE: Contrast and glare sensitivity tests are now being used as adjuncts to visual acuity in the assessment of visual function. Limited data are available on the associations of the former tests with cataract type and severity. The aim of the study is to assess these associations using standardized techniques. METHODS: Contrast sensitivity tests (using the Pelli-Robson chart) and glare sensitivity tests (using the Vistech MCT 8000) were done on 128 patients with cataracts and no other ocular disease and on 29 control volunteers. The cataracts were graded using the Lens Opacities Classification System II (LOCS II). Data from the left eyes were analyzed using logistic regression models. RESULTS: Contrast sensitivity loss was associated with cataract severity for cortical (P less than 0.0001) and posterior subcapsular (P = 0.0001) cataracts and with decreased visual acuity (P = 0.0001). Night and day glare sensitivity were each associated only with increased severity of posterior subcapsular cataracts (P less than or equal to 0.003) and with decreased visual acuity (P less than 0.001). Additional analyses showed that contrast and glare sensitivity were similar in eyes with no cataracts and early cataracts. CONCLUSION: These results suggest that the Pelli-Robson Chart and the Vistech MCT 8000 are good techniques for evaluating visual function in moderate to advanced cataracts. However, for early cataracts, other techniques need to be explored to assess visual function loss.

Adult↗
PubMed1991

Specular microscopy studies on the corneal endothelium after cessation of contact lens wear.

We performed specular microscopy on the corneal endothelium of 22 long-term hard contact lens wearers (15-32 years duration) and 22 age- and sex-matched controls. We found polymegethism in users as shown by a significant difference in the coefficient of variation in cell area (p less than 0.01) and pleomorphism as shown by a significant decrease in the percent of 6-sided cells (hexagonality, p less than 0.01). There was no significant difference in cell density and mean cell area between the 2 groups. Contact lens wear was discontinued in five eyes of three patients after they were entered into the study and switched to eye-glasses. Specular micrographs were taken up to 60 months after discontinuation of use of the lenses. Comparison of the above parameters before and after discontinuation of the lenses did not show a significant change. However, there was a trend toward improvement in the coefficient of variation in the eyes that were followed the longest. This finding suggests that the morphological changes induced by long-term use of contact lenses may be slowly reversible after prolonged discontinuation of contact lens wear.

Adult↗
PubMed1990

A randomized placebo-controlled trial of cysteamine eye drops in nephropathic cystinosis.

Eighteen patients with nephropathic cystinosis who were younger than 42 months and 11 patients 4 to 31 years of age were entered into a double-masked, randomized, placebo-controlled trial of topical cysteamine eye drops between November 1985 and September 1989. Eight of the younger patients and 2 of the older patients showed marked clearing of corneal crystals in one eye compared with the fellow eye. When the code was broken, all 10 patients were found to have received cysteamine eye drops in the improved eye. Of the remaining 19 patients 4 were unavailable for follow-up. In 15 patients no marked difference was noted between the two eyes. Eight have presumably been in the protocol for too short a time and several have been poor compliers with the therapy. These results not only demonstrate the potential for primary prevention of corneal crystal deposition but also, for the first time, offer the possibility of reversing the corneal complications of cystinosis in older patients.

Adolescent↗
PubMed1990

Low myopia with low astigmatic correction gives cataract surgery patients good depth of focus.

Multifocal intraocular lenses (IOLs) are being developed to improve the depth of focus of pseudophakic patients. However, the authors noted good uncorrected distance and near acuity in 32 pseudophakic patients with post-operative refraction of myopic astigmatism and round reactive pupils where a plano convex monofocal posterior chamber IOL was used. They suggest that for appropriate clinical assessment of the effectiveness and safety of multifocal IOLs, a randomized, controlled, double-masked clinical trial be undertaken to compare monofocal with multifocal IOLs. In such a trial, they suggest aiming for myopic astigmatism in the monofocal IOL group.

Astigmatism↗
PubMed1990

Computerized cataract detection and classification.

156 eyes of patients and normal volunteers were classified at the slit lamp into the following pure groups: normal (n = 50), nuclear (n = 39), cortical (n = 33) and PSC (n = 34). The eyes were photographed with the Topcon SL-45 Scheimpflug camera and the images scanned and processed to obtain one dimensional profiles through a 40 x 440 micron axial window. Of the 156 profiles, 90 were used as reference samples and were processed to obtain average profiles. The remaining 66 "unknown" profiles and each of the reference profiles, were classified into the four groups based on their distance from the average profiles in Euclidean space. The system was found to be very sensitive (98%) in detecting the presence of cataracts and specific (100%) in identifying normal, i.e. cataract negative lenses. In classifying pure cataracts into the various classes 98% of answers were correct.

Adult↗
PubMed1990

The effects of sorbinil, an aldose reductase inhibitor, on the corneal endothelium in galactosemic dogs.

Wide-field specular microscopy was used to examine the central corneal endothelium of age- and sex-matched beagle dogs fed for up to 32 months either normal control diets containing 30% nonnutrient filler (13 dogs) or diets containing 30% galactose with (13 dogs) or without (12 dogs) concomitant treatment with the aldose reductase inhibitor, sorbinil. Computerized morphometric analysis of the endothelial cells indicated that a significant decrease in cell density and increase in mean cell area occurred in untreated galactose-fed dogs after 32 months of feeding compared with the normal controls. However, no significant difference could be observed in similar galactose-fed dogs treated with sorbinil. No significant difference in the coefficient of variation of the area, or percent hexagonality of the endothelial cells, or the corneal thickness could be observed in any group. These findings demonstrated that endothelial abnormalities were present in the cornea of the galactose-fed dogs which were similar to those reported for diabetic dogs, rats, and patients and that these changes can be prevented by the concomitant administration of an aldose reductase inhibitor. These findings suggest a role for aldose reductase in the abnormalities noted in the corneal endothelium in diabetes and galactosemia.

Aldehyde Reductase↗
PubMed1989

The association of posterior capsular lens opacities with bilateral acoustic neuromas in patients with neurofibromatosis type 2.

This study of 47 patients from 11 families with neurofibromatosis type 2 (NF 2) confirms our previously reported association between posterior capsular cataract and NF 2. A highly significant statistical association was found between the presence of posterior capsular lens opacities and the presence of NF 2 as determined by magnetic resonance imaging or pathologic diagnosis. This association was not present for other types of lens opacities that could be the result of age-related or nonspecific changes. When considering the diagnosis of NF 2, this finding now makes it essential to use a careful dilated biomicroscopic examination of the lens to evaluate known, suspected, or at-risk individuals for this potentially early associated manifestation.

Cataract↗
PubMed1989

Idiopathic presenile cataract formation and galactosaemia.

Five hundred patients undergoing cataract surgery were prospectively examined, and 46 Caucasian patients were found to have strictly idiopathic cataracts severe enough to warrant surgery on or before age 55. In a masked fashion we determined the activity of galactokinase (GK) and galactose-1-phosphate uridyl transferase (GPUT) in these patients as well as on 53 age matched controls. With respect to GK no cataract patient had an enzyme level of less than 2 standard deviations below the control mean. However, 3 of 45 (6.7%) patients in the cataract group had a GPUT level less than 2 standard deviations below the mean for controls, and were presumably heterozygotes for this enzyme. In comparison with the expected population rate of 0.8% this is highly significant (p = 0.006). Abnormalities in galactose pathway enzymes may therefore predispose to development of presenile cataracts. In affected people there is a possibility of treating these patients clinically by dietary restriction of dairy products or by using aldose reductase inhibitors to prevent or reverse cataract formation.

Adult↗
PubMed1989

Cataract prevention in diabetic Octodon degus with Pfizer's sorbinil.

The Octodon degus has been reported to have higher aldose reductase activity in the lens compared to the gerbil and rat. When made diabetic the degus develop cataracts within 4 weeks. We have been able to completely prevent cataract formation in diabetic degus using Pfizer's sorbinil for up to 6 months. This is further evidence of the role of aldose reductase in the formation of cataracts in diabetes.

Aldehyde Reductase↗
PubMed1989

Measurement error in assessing the size of posterior subcapsular cataracts from retroillumination photographs.

Twenty-six eyes with posterior subcapsular opacities of various sizes were photographed with the Neitz-Kawara Retroillumination camera. The outline of the opacity in a single photograph of each opacity was traced onto a transparent plastic overlay twice by two independent outliners. Two methods were used to estimate the area within the outlines of the opacities. In the first, a transparent overlay with a standard grid was used to count the number of boxes within the outlines. The second method used computer planimetry to estimate the area within the tracings. We estimated the measurement error associated with a single outlining of an opacity and the contribution of the measurement error to overall sample size requirements in studies comparing the mean areas of posterior subcapsular opacities. Variability in the measurement techniques contributed fewer than 20 additional subjects to overall sample size estimates, a small contribution to total sample size requirements in most studies. An outliner's inherent variability in outlining an opacity was a much larger contributor to the measurement error than was variability in assessing the area of the outline of the opacity. While within outliner variability was similar for the two persons outlining the opacities, there were systematic differences in the way the two traced the outlines. Variability from the use of separate photographs of the same opacity taken by different photographers was minimal.

Cataract↗
PubMed1988

Reproducibility study on the Scheimpflug Cataract Video Camera.

The Zeiss Scheimpflug Cataract Video Camera was designed to photograph, store and analyze cataracts in a semi-automated fashion for cross-sectional and longitudinal studies. We conducted a reproducibility study of this system. Twenty-four normal and 61 cataractous eyes were photographed twice by each of two of the authors in the 90 degree meridian and microdensitometry was performed on each of the stored images. Reproducibility was then determined using the intraclass correlation coefficient to determine whether or not the differences encountered were due to variability in the system or due to actual differences among the images. The intraclass correlation in the lens nucleus was 0.995 with 95% confidence limits of .992-.996. Therefore, reproducibility was 99.5%. In the anterior cortex, intraclass correlation was .941 with 95% confidence limits of .919-.959. In the posterior cortex intraclass correlation was .905 with 95% confidence limits of .870-.932. Reproducibility with this instrument was therefore excellent and with certain limitations, this may be a useful instrument in monitoring lens changes in certain diseases and the effects of anti-cataract agents.

Cataract↗
PubMed1987

A comparative study between the PAM and the laser interferometer in cataracts.

We conducted a prospective study on 35 consecutive eyes undergoing cataract extraction to compare the Guyton-Minkowski Potential Acuity Meter (PAM) and the Laser Interferometer (LI) in determining potential visual acuity. The eyes were divided into: group A, which had good visualization of optic disc details, and group B, whose media allowed only disc outline or less to be seen. We found that in group A eyes, both instruments were reliable (with accuracies of 94% for the PAM and 88% for the LI). However, in group B eyes (advanced cataracts), both instruments were unreliable (accuracies of 33% for the PAM and 53% for the LI). Interestingly, in a subgroup of high myopes (axial length greater than 29 mm) with moderate cataracts and poor visual acuties, both instruments were very reliable and helpful in determining how much of the vision loss was due to the cataracts. We therefore strongly recommend potential acuity testing in high myopes with moderate cataracts and poor visual acuity.

Aged↗
PubMed1987

Nephropathic cystinosis: immunohistochemical and histopathologic studies of cornea, conjunctiva and iris.

Specimens of a cornea, conjunctiva and iris were removed at the time of penetrating keratoplasty in a case of nephropathic cystinosis. Immunohistochemical studies revealed the presence of class II antigens on the stromal keratocytes of the cornea and the vascular endothelial cells, pericytes and fibroblasts of the conjunctiva. In addition, there were thinning and focal breaks in Bowman's membrane. Both of these findings may have contributed to the severe photophobia and blepharospasm seen in patients with longstanding cystinosis.

Child↗
PubMed1987

In vivo studies on cataracts using the Scheimpflug slit lamp camera.

We conducted reproducibility studies on an in vivo objective method of documenting cataracts: Scheimpflug photography using the Topcon SL 45 camera. Normal and cataractous lenses were photographed and the photographs digitized and analyzed using a Perkin Elmer microdensitometer attached to a PDP 11 and Vax 11/780 computer. Linear densitometry was performed through the center of the lens. We found very good reproducibility. The intraclass correlation for the mean densities in the nucleus was 0.95: that is, intra- and interobserver variability accounted for only 5% of the overall variability. For the anterior cortex, intraclass correlation was 0.88 and for posterior cortex it was 0.84. This method may be useful, within limits, in future clinical trials of anticataract medications.

Cataract↗