Repeatability and validity of the PowerRefractor and the Nidek AR600-A in an adult population with healthy eyes

We assessed the repeatability and validity of the PowerRefractor and the Nidek AR-600A autorefractor. This is the first independent study conducted on adults to evaluate the performance of these instruments in a laboratory setting. Fifty subjects (23 males and 27 females) aged 16 to 61 years (mean, 37 ± 12) participated in the study. The validity of the PowerRefractor and the Nidek autorefractor readings were determined by comparing them to subjective refraction. Measurements of refractive error were obtained from the two instruments on two separate occasions to assess their repeatability. The measured refractive error was converted into a dioptric power matrix for data analysis. No significant difference was found between the measurements obtained with the two instruments and the subjective refraction. The estimate of refractive error given by the two instruments was also found to be repeatable. In addition to measuring the refractive error, the PowerRefractor also offers the facility to measure eye position, pupil size, and dynamics of accommodation. We suggest some improvements to the PowerRefractor measurement technique to standardize its clinical use and to improve accuracy

Changes in dynamics of accommodation after accommodative facility training in myopes and emmetropes

This study evaluates the effect of accommodative facility training in myopes and emmetropes. Monocular accommodative facility was measured in nine myopes and nine emmetropes for distance and near. Subjective facility was recorded with automated flippers and objective measurements were simultaneously taken with a PowerRefractor. Accommodative facility training (a sequence of 5 min monocular right eye, 5 min monocular left eye, 5 min binocular) was given on three consecutive days and facility was re-assessed on the fifth day. The results showed that training improved the facility rate in both groups. The improvement in facility rates were linked to the time constants and peak velocity of accommodation. Some changes in amplitude seen in emmetropes indicate an improvement in facility rate at the expense of an accurate accommodation response

Refractive changes associated with oblique viewing and reading in myopes and emmetropes

The effect of brief periods of monocular oblique viewing on axial refractive error in myopes and emmetropes was studied in 20 normal subjects. Refractive error and higher order aberrations were measured either with the subject's head positioned such that the subject looked straight into an aberrometer with the right eye or the subject's head rotated to the right or left by approximately 30-so that the subject had to make an eye rotation of the same angle to see the aberrometer's fixation target. In the first experiment, 10 measurements of wavefront aberration were taken over a period of 3 min at each head position. The refractive changes with oblique viewing showed high levels of intersubject variability. Some subjects showed evidence of systematic change in refraction with oblique viewing. All subjects showed pupil constriction. In the second experiment, after the initial measurement of central and oblique refraction, subjects were made to binocularly read a text placed at 25 cm for 20 min, and the refraction measurements were repeated. No systematic changes in refraction were noted during oblique viewing after 20 min of reading. The data from Experiment 1 give some support for the view that shortterm pressures from structures external to the eye may affect its axial refraction. However, the results from Experiment 2 suggest that any such pressures during short-term reading tasks have no significant impact on the axial refraction

Associations between Accommodative Facility, Age, and Refractive Errors in Early, Older Adolescent Myopes and Emmetropes

Background: Accommodative functions are known to differ between myopes and emmetropes. It is not known whether accommodative facility differs at near between younger adolescent and older adolescent myopes and emmetropes. Aim: To examine whether accommodative facility differs at near between younger and older adolescent myopes and emmetropes. Methods: 119 participants aged between 11–21 years were recruited. Refractive error was measured using cycloplegic retinoscopy. Near monocular accommodative facility was measured for 60 seconds, using a +2.00D/–2.00D handheld flipper and N6 print at 40 cm. Participants were classified into two age groups: (i) younger adolescents (range: 11–14 years) and (ii) older adolescents (range: 15–21 years). The criterion applied to define myopia was spherical equivalent refraction: ≥–0.50D) and spherical equivalent refraction: –0.25D to +0.75D) for emmetropia. Univariate Analysis of Variance was carried out to analyze the interaction of age groups and refractive groups on near accommodative facility. Results: Near monocular accommodative facility was significantly lower (p = 0.003) in younger adolescents (5.87 ± 3.72 cpm) compared to older adolescents (8.11 ± 4.11 cpm), indicating age as a significant main effect (F1,115 = 13.44; p = 0.0001). Younger adolescent emmetropes (4.77 ± 2.05 cpm, p = 0.005) and younger adolescent myopes (6.48 ± 4.12 cpm, p = 0.022) had significantly lower monocular near accommodative facility compared to older adolescent emmetropes (9.52 ± 3.27 cpm), but did not show any difference when compared to older adolescent myopes (p > 0.05). This indicates a significant association linking age and refractive error to near accommodative facility (F1,115 = 4.60; p = 0.03). Conclusion: Younger adolescent myopes and younger adolescent emmetropes had reduced monocular near accommodative facility than older adolescent emmetropes, but not when compared to older adolescent myopes

Effects of ageing on the anterior segment of the eye structure and function

[Excerpt] The world will soon have more aged people than children and more people at extreme old age than ever before [1]. Improving quality of life as well as reducing severe disability due to age-related problems has become key for the health systems worldwide. The ageing of the world population has both structural and functional consequences for the human visual system; changes due to ageing occur in all the structures of the eye causing a variety of effects. Over the last few years, great advances in ophthalmic instrumentation allow the determination of ocular parameters to a level of detail without precedent. Such advances allowresearcherstodevelopspecificdevicesforvisualcorrection and rehabilitation and at the same time guide the clinicians in their decision making and selection of treatment options to convey with the increasing demand of highquality outcomes of the ageing population. This special issue aimed at creating a multidisciplinary forum of discussion on recent advances in the knowledge of the effects of ageing in the anterior segment of the human eye’s structure and function, and improvements on early detection, treatment, and prognosis of age-related ocular conditions of the anterior segment. As a result, a remarkable compilation of ten articles cover many of these very different aspects of ocular ageing. [...]info:eu-repo/semantics/publishedVersio