Anterior scleral thickness changes with accommodation in myopes and emmetropes.

Although a range of changes in anterior segment structures have been documented to occur during accommodation, the quantification of changes in the structure of the anterior sclera during the accommodation process in human subjects has yet to be examined. This study therefore aimed to investigate the presence of short-term changes in anterior scleral thickness associated with accommodation in young adult myopic and emmetropic subjects. Anterior scleral thickness was measured in 20 myopes and 20 emmetropes (mean age 21 ±â€¯2 years) during various accommodation demands (0, 3 and 6 D) with anterior segment optical coherence tomography (AS-OCT). A Badal optometer was mounted in front of the objective lens of the AS-OCT to allow measurements of the anterior temporal sclera (1, 2 and 3 mm posterior to the scleral spur) to be obtained while fixating on an external accommodation stimulus. Anterior scleral thickness was not statistically different between refractive groups at baseline, but thinned significantly with the 6 D accommodation demand (-8 ±â€¯21 µm, p < 0.05), and approached a statistically significant change with the 3 D demand (-6 ±â€¯20 µm, p = 0.066). While both refractive groups thinned by a statistically significant amount at the 1 mm location with the 3 D demand; significant (p < 0.001) refractive group differences occurred at 3 mm, where the thinning found in the myopic group reached statistical significance with both the 3 D (-12 ±â€¯21 µm) and 6 D (-19 ±â€¯17 µm) demands, and the emmetropes showed no significant changes. This demonstrates the first evidence of a small but statistically significant thinning of the anterior sclera during accommodation. These changes were more prominent in myopes, particularly 3 mm posterior to the scleral spur. These regional differences may be associated with previously reported regional variations in ciliary body thickness between refractive groups, regional differences in the contraction of the ciliary muscle with accommodation, or differences in the response of the sclera to these biomechanical forces.

The influence of a novel simulated learning environment upon student clinical subjective refraction performance: A pilot study.

BACKGROUND: Optometry students are taught the process of subjective refraction through lectures and laboratory-based practicals before progressing to supervised clinical practice. Simulated leaning environments (SLEs) form part of an emerging technology used in a range of health disciplines; however, there is limited evidence regarding the effectiveness of clinical simulators as educational tools. METHODS: Forty optometry students (20 fourth year and 20 fifth year) were assessed twice by a qualified optometrist (two examinations separated by four to eight weeks), while completing a monocular non-cycloplegic subjective refraction on the same patient with an unknown refractive error, simulated using contact lenses. Half of the students were granted access to an online simulated learning environment, The Brien Holden Vision Institute (BHVI) Virtual Refractor, and the remaining students formed a control group. The primary outcome measures at each visit were; accuracy of the clinical refraction compared to a qualified optometrist and relative to the Optometry Council of Australia and New Zealand (OCANZ) subjective refraction examination criteria. Secondary measures of interest included descriptors of student SLE engagement, student self-reported confidence levels and correlations between performance in the simulated and real-world clinical environment. RESULTS: Eighty per cent of students in the intervention group interacted with the simulated learning environment (for an average of 100 minutes); however, there was no correlation between measures of student engagement with the BHVI Virtual Refractor and speed or accuracy of clinical subjective refractions. Fifth year students were typically more confident and refracted more accurately and more quickly than fourth year students. A year group by experimental group interaction (p = 0.03) was observed for accuracy of the spherical component of refraction and post hoc analysis revealed that less experienced students exhibited greater gains in clinical accuracy following exposure to the SLE intervention. CONCLUSIONS: Short-term exposure to a SLE can positively influence clinical subjective refraction outcomes for less experienced optometry students and may be of benefit in increasing the skills of novice refractionists to levels appropriate for commencing supervised clinical interactions.

Regional Changes in Choroidal Thickness Associated With Accommodation.

PURPOSE: To characterize the changes occurring in choroidal thickness (ChT) across the posterior pole during accommodation using enhanced-depth imaging optical coherence tomography (OCT). METHODS: Forty participants (mean age 21 ± 2 years) had measures of ChT and ocular biometry taken during accommodation to 0, 3, and 6 diopter (D) stimuli, with the Spectralis OCT and Lenstar biometer. A Badal optometer and cold mirror system was mounted on both instruments, allowing measurement collection while subjects viewed an external fixation target at varying accommodative demands. RESULTS: The choroid exhibited significant thinning during accommodation to the 6 D stimulus in both subfoveal (mean change, -5 ± 7 µm) and parafoveal regions (P < 0.001). The magnitude of these changes varied by parafoveal meridian, with the largest changes seen in the temporal (-9 ± 12 µm) and inferotemporal (-8 ± 8 µm) meridians (P < 0.001). Axial length increased with accommodation (mean change, +5 ± 11 µm at 3 D, +14 ± 13 µm at 6 D), and these changes were weakly negatively associated with the choroidal changes (r2 = 0.114, P < 0.05). CONCLUSIONS: A small, but significant thinning of the choroid was observed at the 6 D accommodation demand, which was greatest in the temporal and inferotemporal parafoveal choroid, and increased with increasing eccentricity from the fovea. The regional variation in the parafoveal thinning corresponds to the distribution of the nonvascular smooth muscle within the uvea, which may implicate these cells as the potential mechanism by which the choroid thins during accommodation.