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Purpose: The aim of this study was to evaluate optical and visual functional performance of the osteo-odonto-keratoprosthesis (OOKP)., Methods: Optical design and analysis was performed with customized optical design software. Nine patients with implanted OOKP devices and 9 age-matched control patients were assessed. Contrast sensitivity was assessed and glare effect was measured with a brightness acuity test. All OOKP patients underwent kinetic Goldmann perimetry and wavefront aberrometry and completed the National Eye Institute Visual Function Questionnaire-25 (NEI VFQ-25)., Results: Optical analysis showed that the optical cylinder is near diffraction-limited. A reduction in median visual acuity (VA) with increasing glare settings was observed from 0.04 logMAR (without glare) to 0.20 logMAR (with glare at "high" setting) and significantly reduced statistically when compared with the control group at all levels of glare (P < 0.05). Contrast sensitivity was significantly reduced when compared with age-matched controls at medium and high spatial frequencies (P < 0.05). Median Goldmann perimetry was 65 degrees (interquartile range, 64-74 degrees; V-4e isopters) and 69 degrees excluding 2 glaucomatous subjects. Several vision-related NEI VFQ-25 subscales correlated significantly with VA at various brightness acuity test levels and contrast sensitivity at medium spatial frequencies, including dependency, general vision, near activities and distance activities., Conclusions: The OOKP optical cylinder provides patients with a good level of VA that is significantly reduced by glare. We have shown in vivo that updates to the optical cylinder design have improved the patient's field of view. Reduction of glare and refinement of cylinder alignment methods may further improve visual function and patient satisfaction.

Purpose: To explore the success of the application of a computerised videokeratography (CVK) software system for the fitting of rigid gas permeable (RGP) contact lenses (CLs) on irregular corneal surfaces and compare it to the standard diagnostic fitting procedure., Methods: This was a comparative prospective study, over a 1-year period (2004-2005). It included 41 RGP CL wearers (68 eyes) with irregular corneal surfaces. Of these, 51 (75%) had keratoconus, 7 (10%) corneal scarring (infectious or traumatic), 6 (6.82%) corneal transplants, 2 (2.9%) astigmatism, and 2 (2.9%) aphakia. Each eye was being re-fitted with a new RGP CL based on a topographical measurement in conjunction with a CL fitting software programme. The performance of the CLs was evaluated regarding visual outcome, fitting characteristics, and efficiency of the fitting procedure., Results: Of the 68 eyes, 53 (77.94%) chose the CL fitted using the CVK software system, 9 (13.24%) chose the CL fitted using the standard procedure, and 6 (8.82%) showed no preference for either CL. There was a statistically significant improvement regarding visual outcome [contrast sensitivity at the spatial frequencies of 0.66 (p=0.029), 3.40 (p=0.008), and 17 (p=0.032), subjective vision (p=0.009)], fitting characteristics [grading scale (p=0.00), lens comfort (p=0.00) and daily wearing time (p=0.002)], and efficiency [number of trial lenses required (p=0.00)] with the CL fitted using the CVK software system. Correlating factors for the likely preference for the CL fitted using the CVK software system were subjective vision (p=0.004), lens comfort (p=0.009), and convenience of the fitting procedure (p=0.023)., Conclusion: The application of a CVK software system for the fitting procedure of RGP CLs on irregular corneal surfaces was a safe procedure and shown to be more successful and efficient than the standard diagnostic fitting method.

Purpose: To compare tritan contrast threshold (TCT) with fundus photography in screening for sight-threatening diabetic retinopathy (STDR), before significant visual loss., Design: Prospective, comparative study., Methods: A total of 510 consenting diabetic patients attending a hospital-based photographic screening clinic were recruited over a 2-year period. Exclusion criteria included visual acuity of worse than 6/9, previous photocoagulation, and a history of previous eye disease known to affect color vision. The automated TCT test was performed using a computerized cathode ray tube-based technique. Retinal photography was performed using a Polaroid mydriatic fundus camera with a 45 degrees field. Grading of diabetic retinopathy was carried out by an ophthalmologist using slit-lamp biomicroscopy and a 78-diopters lens. Assessments of sensitivity, specificity, and predictive values for both fundus photography and the TCT test were made., Results: Both the fundus photography and TCT test correlated significantly with the presence of STDR (P <.0001, chi(2) test). The TCT test yielded a sensitivity of 94% (95% confidence interval [CI], 73%- 100%) and a specificity of 95% (95% CI, 92%- 96%) for detection of STDR compared with a sensitivity of 88% (95% CI, 66%-97%) and a specificity of 95% (95% CI, 93%-97%) with fundus photography. Combined modality improved overall screening performance., Conclusion: The TCT assessment is an effective and clinically viable technique, in comparison with fundus photography, to screen for STDR among a diabetic population. Additionally, our results also showed that combining the TCT test with fundus photography greatly increases the performance of screening for STDR.

Purpose: To investigate abnormalities of orientational contrast sensitivity (CS) and chromatic contrast threshold (CCT) in multiple sclerosis (MS)., Design: Case control study., Methods: Nine subjects (mean age, 42 +/- 11 years; range, 20-62 years) with MS, an expanded disability status scale of 3 or less, and normal visual acuity (VA) (logarithm of the minimum angle of resolution [logMAR] VA less than.1) in the tested eye were age-matched with 20 controls. Achromatic CS and CCT were measured using static, computer-generated sinusoidal gratings displayed on a high-resolution monitor. The CS and CCT of each subject were determined using a randomized double-staircase reversal algorithm; CS was measured at five spatial frequencies with horizontal orientation and three with vertical orientation; CCT was measured along the red-green and tritan confusion axes. The sensitivity thresholds of subjects were examined in relation to the mean sensitivity of controls for each spatial frequency., Results: Two subjects had loss of horizontal and vertical CS, and three had isolated vertical loss. When compared with the control mean, there were significant reductions in red-green (P =.016) and tritan (P =.016) discrimination thresholds., Conclusion: This study used a computerized psychophysical test designed to minimize many of the test errors associated with earlier studies. It provides confirmatory evidence that MS may be associated with a loss of orientational CS and color vision, in the absence of reduced VA.

Purpose: To study the effect of prematurity on monocular chromatic contrast thresholds (CCT) and achromatic contrast sensitivity (ACS)., Design: Case-control study., Methods: A prospective study of 59 children born at less than 33 weeks' gestation was undertaken. Subjects were identified during routine neonatal screening for retinopathy of prematurity and recalled for testing at age 7 to 13 years. Five had stage 1 retinopathy of prematurity, seven had stage 2, and three had stage 3. Sixty-eight full-term children were recruited as controls. Those with major cerebral or eye disease were excluded. The CCT and ACS were measured monocularly in the eye with better visual acuity using static, computer-generated, sinusoidal gratings, displayed on a high-resolution monitor. The CCT and ACS were determined using a randomized double-staircase reversal algorithm. The ACS was measured at five spatial frequencies (0.22, 0.44, 0.88, 1.75, and 3.50 cycles/degree), and the CCT was measured along red-green and tritan confusion axes., Results: Red-green (P =.326) and tritan (P =.910) contrast thresholds and ACS (P >.394 for all spatial frequencies) were similar to the control group., Conclusions: Previous research suggests that prematurity adversely affects color vision and ACS. This study used a computerized psychophysical test that minimized the test errors inherent in many previous studies. Unexpectedly, CCT and ACS were found to be similar to full-term children.