Intraocular scattering as a predictor of driving performance in older adults with cataracts.

Cataracts can limit a person's ability to perform vision-dependent tasks safely, affecting the quality of life of older people. This study examines the relationship between visual function and driving, by studying which visual parameters might be important for predicting driving performance in older drivers with and without cataracts, ascertaining whether the objective measurement of intraocular scattering should be considered in assessment procedures for older drivers. This cross-sectional study involved a total of 20 older drivers (10 patients with bilateral cataracts and 10 control subjects). All participants were examined for visual acuity, contrast sensitivity, visual discrimination capacity, and intraocular scattering. Driving performance was also tested using a driving simulator. To study the relationship between visual parameters and driving performance, a correlation analysis and regression model were used. Drivers with cataracts showed a significantly impaired (p<0.05) visual function, with an Objective Scattering Index (OSI) 3.5 times greater than the control group. Driving performance was also significantly worse (p<0.05) in drivers with cataracts, reflected by a notable deterioration in lane keeping. The correlation analysis showed significant associations between driving performance and all the visual parameters studied. Finally, the regression model revealed that the OSI was the best predictor of driving performance, accounting for 51.3% of its variance. Visual function and driving performance are markedly deteriorated when cataracts are present. Our results demonstrate that the objective scattering index (OSI) has a high predictive power when it comes to simulated driving performance in older drivers, both with and without cataracts, suggesting that scatter measurements could be important in helping better understand visual limitations in older drivers.

Binocular summation and visual function with induced anisocoria and monovision.

The advances in new techniques for correcting presbyopia, such as a small aperture combined with monovision, require an in-depth study of binocular aspects. In this work, we have studied binocular visual performance of 12 subjects after inducing different degrees of anisocoria combined with two different add powers in the non-dominant eye. We have analysed visual performance in terms of the visual-discrimination capacity (a function to evaluate the strength of bothersome halos) and the contrast-sensitivity. The results show a deterioration of the binocular vision when inducing anisocoria and with any add power, with a higher perception of halos, a lower contrast sensitivity and poorer binocular summation of these visual functions on increasing anisocoria. This deterioration is clinically acceptable in the case of low add power, since positive binocular summation is maintained in contrast sensitivity, and visual discrimination is not altered.

Prevalence of refractive errors in children in Equatorial Guinea.

PURPOSE: The aim of this work is to evaluate the epidemiological aspects of the refractive errors in school-aged children in Malabo (Island of Bioko), Equatorial Guinea (western-central Africa). METHODS: A total of 425 schoolchildren (209 male subjects and 216 female subjects, aged between 6 and 16 years) were examined to evaluate their refraction errors in Malabo, Equatorial Guinea (western-central Africa). The examination included autorefraction with cycloplegia, measurement of visual acuity (VA) for far vision, and the curvature radii of the main meridians of the anterior surface of the cornea. RESULTS: A low prevalence of myopia was found (≤-0.50 diopters [D] spherical equivalent), with unilateral and bilateral myopia being 10.4 and 5.2%, respectively. The prevalence of unilateral and bilateral hypermetropia (≥2.0 D spherical equivalent) was 3.1 and 1.6%, respectively. Astigmatism (≤-0.75 D) was found in unilateral form in 32.5% of these children, whereas bilateral astigmatism was found in 11.8%. After excluding children having any ocular pathology, the low prevalence of high refractive errors signified good VA in these children. Significant differences were found in the distribution of the refractive errors by age and type of schooling (public or private) but not by sex. In general, the radii of the anterior of the cornea did not vary significantly with age. CONCLUSIONS: The mean refractive errors found were low and therefore VA was high in these children. There was a low prevalence of myopia, with significantly higher values in those who attended private schools (educationally and socioeconomically more demanding). Astigmatism was the most frequent refractive error.

A visual test based on a freeware software for quantifying and displaying night-vision disturbances: study in subjects after alcohol consumption.

BACKGROUND: In this work, we propose the Halo test, a simple visual test based on a freeware software for quantifying and displaying night-vision disturbances perceived by subjects under different experimental conditions, more precisely studying the influence of the alcohol consumption on visual function. METHODS: In the Halo test, viewed on a monitor, the subject's task consists of detecting luminous peripheral stimuli around a central high-luminance stimulus over a dark background. The test, performed by subjects before and after consuming alcoholic drinks, which deteriorate visual performance, evaluates the influence that alcohol consumption exerts on the visual-discrimination capacity under low illumination conditions. Measurements were made monocularly and binocularly. Pupil size was also measured in both conditions (pre/post). Additionally, we used a double-pass device to measure objectively the optical-quality of the eye and corroborate the results from the Halo test. RESULTS: We found a significant deterioration of the discrimination capacity after alcohol consumption, indicating that the higher the breath-alcohol content, the greater the deterioration of the visual-discrimination capacity. After alcohol intake, the graphical results showed a greater area of undetected peripheral stimuli around the central high-luminance stimulus. An enlargement of the pupil was also observed and the optical quality of the eye was deteriorated after alcohol consumption. CONCLUSIONS: A greater influence of halos and other night-vision disturbances were reported with the Halo test after alcohol consumption. The Halo freeware software constitutes a positive contribution for evaluating nighttime visual performance in clinical applications, such as reported here, but also in patients after refractive surgery (where halos are present) or for monitoring (time course) some ocular pathologies under pharmacological treatment.

Quantifying age-related differences in visual-discrimination capacity: drivers with and without visual impairment.

The aim of this study is to examine the effects of aging as well as visual impairment on retinal-image quality and visual performance in drivers. We use a new visual test called Halo v1.0 software for quantifying the discrimination capacity, an important visual function for evaluating the visual disturbances perceived by the observer. The study included 55 subjects with normal vision and 15 older subjects with cataracts. All subjects were examined for visual acuity, contrast sensitivity, visual-discrimination capacity and optical quality. Subjects also completed a subjective Driving Habits Questionnaire (DHQ). Older drivers with and without visual impairment showed significantly (p < 0.05) worse visual performance and deteriorated retinal-image quality, even when their binocular visual acuity was ≥20/25. In conclusion, some visual functions are considerably diminished in older drivers, even when visual acuity is sufficient to get or renew a driver's license. Halo software enables easy quantification of night-vision disturbances such as halos, which could impede the detection of pedestrians, cyclists, or traffic signals, thereby making this system advisable in clinical practice, e.g. in the requirements for a driver's license, particularly for older drivers.

Ametropias in school-age children in Fada N'Gourma (Burkina Faso, Africa).

PURPOSE: To assess epidemiological aspects of refractive errors in school-age children in Burkina Faso (west-central Africa). METHODS: A total of 315 school children (ranging from 6 to 16 years of age and belonging to different ethnic groups) taken at random from two urban schools in eastern Burkina Faso were examined to assess their refractive error, which was determined by non-cycloplegic retinoscopy with optical fogging. The standard Refractive Error Study in Children (RESC) definitions of refractive errors were used: myopia ≤-0.5 D spherical equivalent (SE) in at least one eye, hyperopia ≥2 D SE in at least one eye, astigmatism ≤-0.75 D cylinder in at least one eye, and anisometropia ≥1 D SE difference between the two eyes. RESULTS: Unilateral myopia and bilateral myopia were found in 2.5 and 1%, respectively; unilateral hyperopia in 17.1%, bilateral hyperopia in 8.6%; astigmatism in at least one eye in 11.7%. The highest prevalence value (18.4%) of astigmatism (≤-0.75 D) in at least one eye was found in the Gourmantché ethnic group. The low prevalence of large refractive errors makes visual acuity in these children very good (visual acuity logarithm of the minimum angle of resolution -0.073 ± 0.123 SD). CONCLUSIONS: There was a low prevalence of myopia in these African school children. Clinically significant high hyperopia (≥+2 D SE) was also uncommon. There were no significant differences between the distributions of refractive errors according to gender or ethnicity. With respect to age groups, the prevalences of hyperopia and astigmatism were significantly higher in the younger age groups.

Visual evaluation of different multifocal corneal models for the correction of presbyopia by laser ablation.

PURPOSE: To evaluate the visual quality of two theoretical multifocal corneal models designed to correct presbyopia by corneal photoablation. METHODS: Two theoretical multifocal corneal surfaces were analyzed by ray tracing: a central model (with a central zone for near vision and a peripheral zone for distance vision), and a peripheral model (with a central zone for distance vision and a peripheral zone for near vision). For both models, the effect of the size of the central zone and transition zone as well as the size of the pupil was evaluated. RESULTS: Our results show that a smaller transition zone favors total visual quality in both models. The optimal size of the central zone depends both on the size of the transition zone used as well as the model. However, both models responded similarly with respect to the variations in pupil size, providing the same visual quality although in an opposite way. CONCLUSIONS: This work shows that the optimal diameter of the central zone is smaller for the central model than for the peripheral model. Also, pupil size plays a fundamental role in achieving multifocality, showing that patient's pupil size should be thoroughly evaluated prior to multifocal refractive surgery.

Prevalence of refractive errors in school-age children in Morocco.

BACKGROUND: The prevalence of refractive errors in school-age children in Morocco was assessed. METHODS: A total of 545 children (300 boys and 245 girls, between 6 and 16 years of age) attending school were examined to assess their refractive errors in a field study in Morocco (North Africa). The examination included autorefraction under cycloplegia and visual acuity, stereopsis and anterior corneal-radius measurements . RESULTS: We found a low prevalence of myopia (< or =-0.5 D SE [spherical equivalent] in at least one eye), i.e. only 6.1%. The prevalence of hyperopia (> or =2.0 D SE in at least one eye) was 18.3%. Astigmatism (< or =-0.75 D of cylinder in at least one eye) was found in 23.5% of these children. The low prevalence of large refractive errors makes visual acuity in these children very good. In general, the corneal radii did not significantly vary with age. There were no significant differences between the distribution of refractive errors in these children according to gender but there were with respect to age. CONCLUSIONS: There was a low prevalence of myopia in these African children, astigmatism being the most frequent refractive error. The mean refractive errors found were low, and therefore visual acuity was high in these children.