Search PubMed⌕ Search

Biomedical subjects

Leo G Carney

Publications and source records attributed to Leo G Carney.

6 recordsLinked to original sources
PubMed2003

Relationship between goblet cell density and tear function tests.

AIM: The objective of this study was to find a relationship between goblet cell density (GCD) and other diagnostic tests of dry eye in a group of normal healthy Chinese subjects. The capability of using GCD as a tear function test was assessed. METHOD: A total of 42 optometry students with no contact lens wear history were recruited. Subjects were required to fill in a dry eye questionnaire. The non-invasive tear break-up time (NITBUT) of each subject was measured, followed by phenol red thread test (PRTT) and tear break-up time (TBUT) tests. Conjunctival epithelial cells from the inferior nasal bulbar conjunctiva were harvested by the impression cytology technique. The specimens collected were labelled and stained with PAS (Periodic Acid Schiff)-haematoxylin. The goblet cells and the conjunctival epithelial cells were counted under a light microscope of 100x magnification. Spearman's rho (rho) correlation test was used to analyse the relationship between GCD and the other tear function tests. RESULTS: With a probability level of 0.0051 (corrected for a cumulative familywise error rate of p = 0.05), GCD was found to have no correlation with NITBUT (rho = -0.193, p = 0.222), McMonnies Dry Eye Scores (MCDES) (rho = -0.052, p = 0.742), PRTT (rho = - 0.188, p = 0.234) and TBUT (rho = 0.246, p = 0.117). CONCLUSION: There was no correlation between GCD and MCDES, NITBUT, PRTT and TBUT. The GCD alone is not a useful diagnostic test for tear film instability in normal eyes although it is a good indicator in the diagnosis of ocular surface diseases.

Adult↗
PubMed2003

Experience and training as determinants of grading reliability when assessing the severity of contact lens complications.

PURPOSE: A study was conducted to investigate the influence of experience and training on grading reliability when assessing the severity of contact lens complications. METHODS: Twenty-three optometry students who were unfamiliar with the use of grading scales each used the Efron Grading Tutor computer program to ascertain grading reliability at an 'initial' experimental session and a 'final' session 3 weeks later. Twelve subjects (the 'trained' group) were given a tutorial on grading techniques and were asked to complete two grading exercises between the initial and final sessions. The other 11 subjects (the 'untrained' group) received no such training between the two sessions. Differences in grading reliability between the initial and final grading sessions were evaluated. RESULTS: Grading reliability was superior (lower) for the combined subject cohort at the final session (mean +/- standard deviation 0.33 +/- 0.12) compared with the initial session (0.46 +/- 0.25) (p = 0.004). However, there was no difference in the improvement in grading reliability between the two groups. CONCLUSIONS: Grading reliability improves statistically with some experience, although perhaps not to a clinically meaningful extent. No added benefit can be derived from supplemental training.

Clinical Competence↗
PubMed2003

Corneal topography and accommodation.

PURPOSE: To investigate whether there are significant changes in corneal topography during accommodation in normal corneas and corneas that are pathologically thinner due to keratoconus. METHODS: A videokeratoscope was modified to present an accommodation stimulus that was coaxial with the instrument's measurement axis. Six subjects with normal corneas and four subjects with keratoconus were studied. Eighteen videokeratoscope measurements of one eye of each subject were taken at 0 diopter (D) accommodation demand and six for both of 4 D and 9 D accommodation demand. The effects of ocular micromovements on multiple topography maps were minimized using software algorithms. Average maps for the 4 D and 9 D accommodation demands were calculated and subtracted from the average map of the 0-D accommodation demand. A t test was applied at each point location within the topography maps to analyze the statistical significance of change (p < 0.001) within the difference maps. RESULTS: In the initial analysis, we found that a number of the subjects showed significant changes in corneal topography as accommodation changed. However, further analysis showed a significant group mean excyclotorsion of the topography maps of 1.6 +/- 1.1 degrees (p < 0.03) for the 4-D stimulus and 2.0 +/- 1.3 degrees (p < 0.01) for the 9-D stimulus compared with the 0-D stimulus. When we accounted for the excyclotorsion, we did not find clear evidence of statistically significant changes in corneal topography as a result of accommodation, either for the normal corneas or the keratoconic corneas. CONCLUSIONS: It appears unlikely that changes occur in central corneal shape during accommodation up to a level of 9 D in normal or keratoconic corneas. A small ocular excyclotorsion typically accompanies accommodation, and this changes the relative orientation of the topography of the cornea. This has significant implications for the interpretation of the optical characteristics of eyes during near viewing conditions.

Accommodation, Ocular↗
PubMedDate not supplied

Corneal shape in hyperopia.

Background: A trend towards decreased peripheral corneal flattening with increasing myopia has recently been demonstrated. The present study was conducted to determine whether corneal asphericity also varies significantly with hyperopic refractive error. Methods: Thirty-five eyes with spherical equivalent refractive error ranging from -0.37 D to +6.00 D were examined. A conicoid equation was fitted to videokeratoscopic (Topographic Modeling System) data and corneal asphericity and apical radius of curvature values were calculated for each subject. Axial length measurements were made using a hand-held biometric ruler. Keratometry was also performed on each eye. Results: The relationship between corneal asphericity (Q) and spherical equivalent refractive error was not statistically significant (p = 0.7419). In addition, no association could be demonstrated between Q and corneal radius of curvature or between Q and axial length. Corneal radius of curvature was positively correlated with axial length (r = 0.367, p = 0.0298). Axial length was found to decrease as hyperopic refractive error increased (r = 0.753, p = 0.0001). Conclusions: For hyperopic eyes, corneal asphericity does not appear to be significantly correlated with refractive error, a finding that is at variance with previous data for myopic eyes showing an association between these two variables. The results suggest that there may be differences between hyperopic and myopic eyes with regard to the anterior segment changes that occur during refractive error development.

Journal Article↗
PubMedDate not supplied

Monochromatic aberrations and characteristics of retinal image quality.

BACKGROUND: Patients use a wide variety of terms to describe the characteristics of their vision. These descriptions encompass the effects of their eyes' monochromatic aberrations. METHODS: To illustrate the effect of monochromatic aberrations on the quality of the retinal image, we mathematically reconstructed the image falling on the retina. This has been achieved by combining the properties of various scenes with the optical characteristics of the eye. RESULTS: The effects of some common monochromatic aberrations are illustrated. We also show examples of the retinal image characteristics for two eyes, one with a decentred corneal apex and a second with a decentred refractive surgery ablation. CONCLUSIONS: The image reconstruction technique provides a powerful tool for investigating the quality of the retinal image. It provides the capacity for clinicians to better understand a patient's visual performance. The image reconstruction technique can also broaden our knowledge of the effects of various forms of aberrations on retinal image quality for complex real-world scenes.

Journal Article↗