Measurement of in vivo lens shapes using IOLMaster 700 B-scan images: Comparison with phakometry.

PURPOSE: This study compared in vivo crystalline lens shape measurements using B-scan images from the IOLMaster 700 with phakometry. METHODS: Twenty-four young adult participants underwent IOLMaster 700 and phakometry measurements under cycloplegia (1% cyclopentolate). The IOLMaster 700 generated B-scan images along six meridians in 30° increments, which were analysed using custom MATLAB software to determine lens surface radii of curvature. Phakometry measurements were obtained using Purkinje images reflected from the lens surfaces. RESULTS: The IOLMaster 700 image analysis method yielded a lower mean anterior lens surface spherical equivalent power (+6.20 D) than phakometry (+7.55 D); however, the two measurements were strongly correlated (R(21) = 0.97, p < 0.0001). The astigmatic power vectors (J0 and J45) for the anterior lens surface were significantly higher for the IOLMaster 700 measurements, with only J0 showing a significant moderate positive correlation (R(21) = 0.57, p = 0.005). For the posterior lens surface, the IOLMaster 700 measurements had a higher mean spherical power (+14.28 D) compared to phakometry (+13.70 D); however, a strong positive correlation (R(21) = 0.90, p < 0.0001) was observed. No significant correlations were noted for posterior lens surface astigmatic vectors (J0 and J45). The IOLMaster 700 estimates for the equivalent lens mean spherical power were slightly lower than those for phakometry, with a mean difference of -0.72 D, and both methods were positively correlated (R(21) = 0.94, p < 0.0001). CONCLUSIONS: The findings demonstrate that IOLMaster 700 B-scan image analysis technique provides similar estimates of lens surface powers to phakometry. These results highlight the potential of the IOLMaster 700 to provide measurements of lens shape, informing future research and clinical use.

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.

Daily morning light therapy is associated with an increase in choroidal thickness in healthy young adults.

Ambient light exposure is one environmental factor thought to play a role in the regulation of eye growth and refractive error development, and choroidal thickness changes have also been linked to longer term changes in eye growth. Therefore in this study we aimed to examine the influence of a 1-week period of morning light therapy upon choroidal thickness. Twenty two healthy young adult subjects had a series of macular choroidal thickness measurements collected with spectral domain optical coherence tomography before, and then following a 7-day period of increased daily light exposure. Increased light exposure was delivered through the use of commercially available light therapy glasses, worn for 30 minutes in the morning each day. A significant increase in subfoveal choroidal thickness (mean increase of +5.4 ± 10.3 µm) was found following 7-days of increased daily light exposure (p = 0.02). An increase in choroidal thickness was also observed associated with light therapy across the central 5 mm macular region. This study provides the first evidence in the human eye that daily morning light therapy results in small magnitude but statistically significant increases in choroidal thickness. These changes may have implications for our understanding of the impact of environmental factors upon eye growth.

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.