Optometry and Vision

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Uncorrected Refractive Error and Distance Visual Acuity in Children Aged 6 to 14 Years SIGNIFICANCE This study presents the relationship between distance visual acuity and a range of uncorrected refractive errors, a complex association that is fundamental to clinical eye care and the identification of children needing refractive correction. PURPOSE This study aimed to analyze data from the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error Study to describe the relationship between distance uncorrected refractive error and visual acuity in children. METHODS Subjects were 2212 children (51.2% female) 6 to 14 years of age (mean ± standard deviation, 10.2 ± 2.1 years) participating in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error Study between 2000 and 2010. Uncorrected distance visual acuity was measured using a high-contrast projected logMAR chart. Cycloplegic refractive error was measured using the Grand Seiko WR-5100K autorefractor. The ability of logMAR acuity to detect various categories of refractive error was examined using receiver operating characteristic curves. RESULTS Isoacuity curves show that increasing myopic spherical refractive errors, increasing astigmatic refractive errors, or a combination of both reduces distance visual acuity. Visual acuity was reduced by approximately 0.5 minutes of MAR per 0.30 to 0.40 D of spherical refractive error and by approximately 0.5 minutes of MAR per 0.60 to 0.90 D of astigmatism. Higher uncorrected hyperopic refractive error had little effect on distance visual acuity. Receiver operating characteristic curve analysis suggests that a logMAR distance acuity of 0.20 to 0.32 provides the best balance between sensitivity and specificity for detecting refractive errors other than hyperopia. Distance acuity alone was ineffective for detecting hyperopic refractive errors. CONCLUSIONS Higher myopic and/or astigmatic refractive errors were associated with predictable reductions in uncorrected distance visual acuity. The reduction in acuity per diopter of cylindrical error was about half that for spherical myopic error. Although distance acuity may be a useful adjunct to the detection of myopic spherocylindrical refractive errors, accommodation presumably prevents acuity from assisting in the detection of hyperopia. Alternate procedures need to be used to detect hyperopia.

Case Report: Successful Corneal Crosslinking in a Patient with Corneal Ectasia Associated with Stevens-Johnson Syndrome SIGNIFICANCE Corneal ectasia can be a complication of Stevens-Johnson syndrome. When detected in a timely manner, corneal crosslinking can be a safe treatment. This is an important association to highlight that early diagnosis and treatment can prevent the need for invasive surgical procedures such as keratoplasty. PURPOSE This study aimed to report a successful accelerated epithelium-off corneal crosslinking in a rare case of corneal ectasia secondary to Stevens-Johnson syndrome. CASE REPORT A 25-year-old Indian man presented with a progressive visual acuity decline 5 years after an acute episode of Stevens-Johnson syndrome secondary to penicillin ingestion. Serial tomography scans confirmed the diagnosis of corneal ectasia. After the preparation of the ocular surface, which was deemed to have a mild degree of limbal stem cell deficiency, with frequent preservative-free lubrication and steroid use, accelerated epithelium-off crosslinking was performed with 4 minutes of continuous ultraviolet-A exposure at 30 mW/cm2 and a total energy dose of 7.2 J/cm2. Complete re-epithelialization was observed at 72 hours after crosslinking with no complications. Corneal tomography 15 months after treatment showed stabilization of ectasia, with improvement in visual acuity. CONCLUSIONS Corneal ectasia is a rare but important complication of Stevens-Johnson syndrome. Accelerated epithelium-off crosslinking treatment can be considered in patients with a compromised ocular surface after Stevens-Johnson syndrome. Pre-operative optimization of the ocular surface and vigilant monitoring in the early post-operative period are recommended for the prevention of complications.

Technical Report: A New Device Attached to a Smartphone for Objective Vision Screening SIGNIFICANCE A new device attached to a smartphone was created for objective vision screening of young children including infants and newborns. The device is compact, lightweight, portable, cost-effective, and easy to operate. Therefore, it is suitable for screening large numbers of children in clinical settings, schools, and communities. PURPOSE This article introduces a new device attached to a smartphone for objective vision screening. It can detect and categorize significant refractive errors, anisometropia, strabismus, cloudy ocular media, and ptosis that may cause amblyopia. METHODS The new device applies the same principles as conventional streak retinoscopy but examines both eyes simultaneously and records the results electronically. The device comprises optical elements that produce a precise streak light beam and move it across a child's both eyes. The smartphone's video camera catches and records the motion of retinal reflex inside the child's pupils. By observing the direction of motion of the retinal reflex relative to the light beam motion, as well as its speed, width, and brightness, the examiner is able to assess the individual and comparative refractive status, ocular alignment, and other conditions. RESULTS Vision screening with this device does not require any subjective response from children. The examination can be performed and analyzed by nonprofessionals after a short learning period of time. Because the examination results are electronically recorded by the smartphone, they can be stored in the child's files and sent out for professional consultations. CONCLUSIONS The new device will provide the same functions as conventional streak retinoscopy but examines a child's both eyes simultaneously, so that, in addition to categorizing refractive errors and assessing clarity of refractive media of the eyes, it can also detect anisometropia, strabismus, and anisocoria. In addition to showing the examination results on the smartphone's screen, the device can also store the results electronically.

Indicators for Assessing the Quality of Refractive Error Care SIGNIFICANCE Quality refractive error care is essential for reducing vision impairment. Quality indicators and standardized approaches for assessing the quality of refractive error care need to be established. PURPOSE This study aimed to develop a set of indicators for assessing the quality of refractive error care and test their applicability in a real-world setting using unannounced standardized patients (USPs). METHODS Patient outcomes and three quality of refractive error care (Q.REC) indicators (1, optimally prescribed spectacles; 2, adequately prescribed spectacles; 3, vector dioptric distance) were developed using existing literature, refraction training standards, and consulting educators. Twenty-one USPs with various refractive errors were trained to visit optical stores across Vietnam to have a refraction, observe techniques, and order spectacles. Spectacles were assessed against each Q.REC indicator and tested for associations with vision and comfort. RESULTS Overall, 44.1% (184/417) of spectacles provided good vision and comfort. Of the spectacles that met Q.REC indicators 1 and 2, 62.5 and 54.9%, respectively, provided both good vision and comfort. Optimally prescribed spectacles (indicator 1) were significantly more likely to provide good vision and comfort independently compared with spectacles that did not meet any indicator (good vision: 94.6 vs. 85.0%, P = .01; comfortable: 66.1 vs. 36.3%, P < .01). Adequately prescribed spectacles (indicator 2) were more likely to provide good comfort compared with spectacles not meeting any indicator (57.7 vs. 36.3%, P < .01); however, vision outcomes were not significantly different (85.9 vs. 85.0%, P = .90). Good vision was associated with a lower mean vector dioptric distance (P < .01) but not with comfort (P = .52). CONCLUSIONS The optimally prescribed spectacles indicator is a promising approach for assessing the quality of refractive error care without additional assessments of vision and comfort. Using USPs is a practical approach and could be used as a standardized method for evaluating the quality of refractive error care.

Negative Fusional Vergence Is Abnormal in Children with Symptomatic Convergence Insufficiency SIGNIFICANCE Deficits of disparity divergence found with objective eye movement recordings may not be apparent with standard clinical measures of negative fusional vergence (NFV) in children with symptomatic convergence insufficiency. PURPOSE This study aimed to determine whether NFV is normal in untreated children with symptomatic convergence insufficiency and whether NFV improves after vergence/accommodative therapy. METHODS This secondary analysis of NFV measures before and after office-based vergence/accommodative therapy reports changes in (1) objective eye movement recording responses to 4° disparity divergence step stimuli from 12 children with symptomatic convergence insufficiency compared with 10 children with normal binocular vision (NBV) and (2) clinical NFV measures in 580 children successfully treated in three Convergence Insufficiency Treatment Trial studies. RESULTS At baseline, the Convergence Insufficiency Treatment Trial cohort's mean NFV break (14.6 ± 4.8Δ) and recovery (10.6 ± 4.2Δ) values were significantly greater (P < .001) than normative values. The post-therapy mean improvements for blur, break, and recovery of 5.2, 7.2, and 1.3Δ, respectively, were statistically significant (P < .0001). Mean pre-therapy responses to 4° disparity divergence step stimuli were worse in the convergence insufficiency group compared with the NBV group for peak velocity (P < .001), time to peak velocity (P = .01), and response amplitude (P < .001). After therapy, the convergence insufficiency group showed statistically significant improvements in mean peak velocity (11.63°/s; 95% confidence interval [CI], 6.6 to 16.62°/s), time to peak velocity (−0.12 seconds; 95% CI, −0.19 to −0.05 seconds), and response amplitude (1.47°; 95% CI, 0.83 to 2.11°), with measures no longer statistically different from the NBV cohort (P > .05). CONCLUSIONS Despite clinical NFV measurements that seem greater than normal, children with symptomatic convergence insufficiency may have deficient NFV when measured with objective eye movement recordings. Both objective and clinical measures of NFV can be improved with vergence/accommodative therapy.

A Comparison of Foveal and Peripheral Contour Interaction and Crowding SIGNIFICANCE Performance on clinical tests of visual acuity can be influenced by the presence of nearby targets. This study compared the influence of neighboring flanking bars and letters on foveal and peripheral letter identification. PURPOSE Contour interaction and crowding refer to an impairment of visual resolution or discrimination produced by different types of flanking stimuli. This study compared the impairment of percent correct letter identification that is produced in normal observers when a target letter is surrounded by an array of four flanking bars (contour interaction) or four flanking letters (crowding). METHODS Performance was measured at the fovea and at eccentricities of 1.25, 2.5, and 5° for photopic (200 cd/m2) and mesopic stimuli (0.5 cd/m2) and a range of target-to-flanker separations. RESULTS Consistent with previous reports, foveal contour interaction and crowding were more pronounced for photopic than mesopic targets. However, no statistically significant difference existed between foveal contour-interaction and crowding functions at either luminance level. On the other hand, flanking bars produced much less impairment of letter identification than letter flankers at all three peripheral locations, indicating that crowding is more severe than contour interaction in peripheral vision. In contrast to the fovea, peripheral crowding and contour-interaction functions did not differ systematically for targets of photopic and mesopic luminance. CONCLUSION The similarity between foveal contour interaction and crowding and the dissimilarity between peripheral contour interaction and crowding suggest the involvement of different mechanisms at different retinal locations.

High Rates of Uncorrected Vision Conditions among Schoolchildren in Rural Queensland, Australia SIGNIFICANCE This study is the first to report high rates of uncorrected vision conditions among Australian secondary schoolchildren living in a rural area and to comment on the rate of eye examinations undertaken on Australian Indigenous children. Uncorrected vision problems that continue throughout the school years have significant implications for children's quality of life and education. PURPOSE This study aimed to investigate the prevalence of uncorrected vision conditions among Australian schoolchildren. METHODS Participants included 280 students from rural primary and secondary schools (aged 4 to 18 years), of whom 40% identified as being of Aboriginal and/or Torres Strait Islander descent (Indigenous). All participants underwent an eye examination including measurements of monocular distance and near visual acuity, assessment of accommodative and vergence function, stereoacuity, color vision, and cycloplegic autorefraction. A parental questionnaire was used to determine whether the child had previously had his/her eyes examined. RESULTS The overall prevalence of uncorrected vision conditions in this population was 35%. The odds of previously having had an eye examination were 2.3× higher for non-Indigenous compared with Indigenous children despite both groups exhibiting high rates of uncorrected vision conditions (Indigenous, 31 [29%]; non-Indigenous, 66 [40%]; χ21 = 3.24, P = .07). Of the children who had significant refractive error (Indigenous, 23 [21%]; non-Indigenous, 49 [30%]; χ21 = 2.70, P = .10), 82% were uncorrected, and only 39% of Indigenous children and 54% of non-Indigenous children had previously had an eye examination. CONCLUSIONS These findings suggest that high rates of uncorrected vision conditions are present among Australian primary and secondary schoolchildren from a rural area and highlight that Indigenous children are much less likely to have had an eye examination. Understanding factors that affect the rate of eye examinations and compliance with spectacle correction must be addressed given the potential impact of these vision conditions.

In Vivo Human Corneal Shear-wave Optical Coherence Elastography SIGNIFICANCE A novel imaging technology, dynamic optical coherence elastography (OCE), was adapted for clinical noninvasive measurements of corneal biomechanics. PURPOSE Determining corneal biomechanical properties is a long-standing challenge. Elasticity imaging methods have recently been developed and applied for clinical evaluation of soft tissues in cancer detection, atherosclerotic plaque evaluation, surgical guidance, and more. Here, we describe the use of dynamic OCE to characterize mechanical wave propagation in the human cornea in vivo, thus providing a method for clinical determination of corneal biomechanical properties. METHODS High-resolution phase-sensitive optical coherence tomography imaging was combined with microliter air-pulse tissue stimulation to perform dynamic elasticity measurements in 18 eyes of nine participants. Low-pressure (0.1 mmHg), spatiotemporally discreet (150 μm, 800 μs) tissue stimulation produced submicron-scale tissue deformations that were measured at multiple positions over a 1-mm2 area. Surface wave velocity was measured and used to determine tissue stiffness. Elastic wave propagation velocity was measured and evaluated as a function of IOP and central corneal thickness. RESULTS Submicron corneal surface displacement amplitude (range, 0.005 to 0.5 μm) responses were measured with high sensitivity (0.24 nm). Corneal elastic wave velocity ranged from 2.4 to 4.2 m/s (mean, 3.5; 95% confidence interval, 3.2 to 3.8 m/s) and was correlated with central corneal thickness (r = 0.64, P < .001) and IOP (r = 0.52, P = .02). CONCLUSIONS Phase-sensitive optical coherence tomography imaging combined with microliter air-pulse mechanical tissue stimulation has sufficient detection sensitivity to observe submicron elastic wave propagation in corneal tissue. These measurements enable in vivo corneal stiffness determinations that will be further studied for use with disease detection and for monitoring clinical interventions.

Visual Function in Eyes with Intermediate AMD with and without Retinal Pigment Abnormalities SIGNIFICANCE In intermediate AMD, a simple, clinically feasible vision test of sensitivity to radial deformation is significantly more impaired in eyes with hyperpigmentation than in eyes with large drusen but normal retinal pigmentation, consistent with the former's increased risk of progression to advanced AMD. This ongoing longitudinal study will determine whether this vision measure is predictive of progression to advanced AMD. PURPOSE This study aimed to determine whether simple, clinically feasible psychophysical measures distinguish between two levels of intermediate AMD that differ in their risk of progression to advanced AMD: eyes with large macular drusen and retinal pigment abnormalities versus eyes with large macular drusen without pigment abnormalities. Abnormal pigmentation in the presence of large drusen is associated with a higher risk of development of advanced AMD. METHODS Each eye of 39 individuals with the same form of intermediate AMD in both eyes was tested monocularly on a battery of vision tests. The measures (photopic optotype contrast sensitivity, discrimination of desaturated colors, and sensitivity to radial deformation [shape discrimination hyperacuity]) were compared for both dominant and nondominant eyes. ANOVA with eye (dominant or nondominant) as a within-subject factor and retinal status (pigmentary abnormalities present or absent from the macula) as a between-subject factor was used to determine statistical significance. RESULTS Sensitivity to radial deformation was significantly reduced in eyes with large drusen and pigment changes compared with eyes with large drusen and normal retinal pigmentation (−0.40 ± 0.04 vs. −0.61 ± 0.02, respectively; F = 13.31, P = .001). CONCLUSIONS In the presence of large macular drusen, performance on a shape discrimination task is related to the presence versus absence of abnormal retinal pigmentation, being poorer in the higher-risk group, supportive of the measure's potential to predict progression to advanced AMD.

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Medicine by Alexandros G. Sfakianakis,Anapafseos 5 Agios Nikolaos 72100 Crete Greece,00302841026182,00306932607174,alsfakia@gmail.com,

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