Objective and subjective assessment of accommodative insufficiency.

SIGNIFICANCE: A variety of subjective and objective procedures are available to measure the amplitude of accommodation. However, it is unclear whether the standard criterion of Hofstetter's minimum minus 2 D can be used to diagnose accommodative insufficiency with each of these techniques. PURPOSE: The use of objective dynamic retinoscopy and three subjective techniques to diagnosis accommodative insufficiency was examined. METHODS: A total of 632 subjects between 8 and 19 years of age were enrolled. Accommodative lag, monocular accommodative facility, and subjective (push-up, modified push-down, and minus lens) and objective (dynamic retinoscopy) amplitude of accommodation were quantified. Accommodative insufficiency was diagnosed based on Hofstetter's minimum minus 2 D for each subjective method, as well as adding an additional subjective criterion (either accommodative lag exceeding 0.75 D or monocular accommodative facility falling below the age-expected norms). RESULTS: The prevalence of accommodative insufficiency was lowest and highest with the push-up (7.9 and 1%) and dynamic retinoscopy (94 and 12%) procedures when measured without and with the additional subjective criteria, respectively. Comparing the validity of dynamic retinoscopy against the traditional criterion, moderate to low sensitivity and high specificity were found. However, adding the additional subjective criteria improved the findings with moderate to high sensitivity and high specificity. Using a cutoff for dynamic retinoscopy of 7.50 D showed moderate diagnostic accuracy based on likelihood ratios. CONCLUSIONS: It is clear that a revised definition of accommodative insufficiency is required, which must include the method of assessing accommodation. The various objective and subjective methods for quantifying the amplitude of accommodation are not interchangeable, and subjective assessment does not provide a valid measure of the accommodative response.

Validation of the DYOP visual acuity test

Purpose: The dynamic optotype (DYOP) visual acuity (VA) test is based on motion detection rather than element resolution and has been proposed for routine clinical assessment. This investigation examined the validity, inter- and intra-session repeatability and subjective preference for the DYOP versus a static letter chart and examined its utility in detecting astigmatic defocus. Methods: VA of 103 participants was measured three times with the letter and DYOP charts and repeated within two weeks in 75 participants who also rated their subjective experience. The VA of 29 participants was measured using DYOP, letter, Landolt C, and Tumbling E charts, with habitual correction and astigmatism induced with +1.00, +2.00 or +3.00 cylinders at 45, 60, 90 and 180°. Results: The charts differed by a mean of 0.02 logMAR, with 81% of the measurements within one line of acuity. Inter-session, intraclass correlation coefficients, within-subject SD and repeatability were 0.03 logMAR, 0.95, 0.11 and 0.30 versus 0.01 logMAR, 0.92, 0.15 and 0.42 for the DYOP and letter charts, respectively. The DYOP was significantly more frustrating (1.79 vs.1.36), with 59% preferring the letter chart. The DYOP was least affected by induced astigmatism. Conclusions: The DYOP and letter charts differed significantly in their mean values with wide limits of agreement. DYOP had better within-subject SD and narrower limits of agreement between sessions, though clinically insignificant, and performed significantly worse for the detection of uncorrected astigmatism. Thus, it is difficult to recommend this test for the clinical determination of refractive error. (AU)

Blue-blocking filters do not alleviate signs and symptoms of digital eye strain.

CLINICAL RELEVANCE: There is some controversy about the utility of prescribing blue-blocking filters to mitigate digital eye strain. We found that using commercially available blue-blocking filters was ineffective in reducing orbicularis oculi muscle activity and visual symptomatology during a 30-min reading task from a computer screen. BACKGROUND: There are some claims that blue-blocking (B-B) filters may be effective in reducing symptoms and signs of digital eye strain. However, recent studies have suggested that there is no sufficient evidence to support their use. This study assessed the short-term effects of a commercially available, B-B filter on orbicularis oculi (OO) muscle activity and symptoms of digital eye strain during the execution of a 30-min reading tas. METHODS: Twenty-three healthy young adults (22.9 ± 3.2 years of age) performed two reading tasks from a computer screen with or without a B-B filter on two different days. OO muscle activity was recorded by surface electromyography 4-5, 9-10, 14-15, 19-20, 24-25 and 29-30 min into the trial. Participants reported their perceived levels of visual discomfort and activation before and after completing the reading task. RESULTS: A Bayesian analysis favoured the null hypothesis that there was no change in OO muscle activity with or without using the B-B filter (Bayes Factor01 [BF01] = 7.08). Regarding symptomatology, the analysis favoured the time model that reading increased visual fatigue and discomfort but reduced activation levels (BF01 < 0.33 in all cases). However, our data did not support the alternative model that using B-B filter affected these visual symptoms. CONCLUSIONS: The B-B filter did not alter OO muscle activity or visual symptomatology significantly during the execution of a 30-min reading task in asymptomatic subjects. These findings support the idea that B-B filters do not attenuate signs and symptoms of digital eye strain.

20-20-20 Rule: Are These Numbers Justified?

SIGNIFICANCE: The use of digital devices has increased substantially in recent years across all age groups for both vocational and avocational purposes. There are a wide range of proposed therapeutic and management options for this condition, including optical, medical, and ergonomic interventions. PURPOSE: Regular breaks are frequently recommended by clinicians to minimize digital eye strain. The so-called 20-20-20 rule, whereby individuals are advised to fixate on an object at least 20 feet (6 m) away for at least 20 seconds every 20 minutes is widely cited. Unfortunately, there is relatively little peer-reviewed evidence to support this rule. The aim of this investigation was to determine whether scheduled breaks are effective in reducing the adverse effects of digital device usage. METHODS: The study was carried out on 30 young subjects who performed a 40-minute, cognitively demanding reading task from a tablet computer. The task required them to read random words and to identify which ones began with a specific letter chosen by the experimenter. The task was undertaken on four separate occasions, with 20-second breaks being allowed every 5, 10, 20, or 40 minutes (i.e., no break), respectively. Both before and after each trial, subjects completed a questionnaire regarding ocular and visual symptoms experienced during the session. In addition, both reading speed and task accuracy were quantified during each trial. RESULTS: A significant increase in post-task symptoms (with respective to the pre-task value) was observed for all four trials ( P < .001). However, there was no significant effect of scheduled breaks on reported symptoms ( P = .70), reading speed ( P = .93), or task accuracy ( P = .55). CONCLUSIONS: Although widely cited as a treatment option, these results do not support the proposal of using 20-second scheduled breaks as a therapeutic intervention for digital eye strain.

Validation of the DYOP visual acuity test.

PURPOSE: The dynamic optotype (DYOP) visual acuity (VA) test is based on motion detection rather than element resolution and has been proposed for routine clinical assessment. This investigation examined the validity, inter- and intra-session repeatability and subjective preference for the DYOP versus a static letter chart and examined its utility in detecting astigmatic defocus. METHODS: VA of 103 participants was measured three times with the letter and DYOP charts and repeated within two weeks in 75 participants who also rated their subjective experience. The VA of 29 participants was measured using DYOP, letter, Landolt C, and Tumbling E charts, with habitual correction and astigmatism induced with +1.00, +2.00 or +3.00 cylinders at 45, 60, 90 and 180°. RESULTS: The charts differed by a mean of 0.02 logMAR, with 81% of the measurements within one line of acuity. Inter-session, intraclass correlation coefficients, within-subject SD and repeatability were 0.03 logMAR, 0.95, 0.11 and 0.30 versus 0.01 logMAR, 0.92, 0.15 and 0.42 for the DYOP and letter charts, respectively. The DYOP was significantly more frustrating (1.79 vs.1.36), with 59% preferring the letter chart. The DYOP was least affected by induced astigmatism. CONCLUSIONS: The DYOP and letter charts differed significantly in their mean values with wide limits of agreement. DYOP had better within-subject SD and narrower limits of agreement between sessions, though clinically insignificant, and performed significantly worse for the detection of uncorrected astigmatism. Thus, it is difficult to recommend this test for the clinical determination of refractive error.

Digital Eyestrain and the Critical Fusion Frequency.

SIGNIFICANCE: Although the high prevalence of digital eyestrain has been well established, to date, there is no objective measurement of this condition. Previous studies have suggested that digital eyestrain may be associated with decreased critical fusion frequency, but the published evidence to support this association is sparse. PURPOSE: This study sought to determine whether symptoms of digital eyestrain after a sustained computer task are indeed associated with changes in critical fusion frequency. METHODS: The experiment was performed on 30 young visual-normal subjects. They attended two sessions, during which they undertook a 20-minute reading task. This comprised either reading random words from a tablet computer or a story from a printed children's book. Critical fusion frequency was measured both before and immediately after each of the reading tasks. In addition, the level of digital eyestrain was assessed by subjects completing a questionnaire regarding ocular and visual symptoms experienced during each of the reading trials. RESULTS: The mean increase in digital eyestrain symptoms after the digital and printed conditions was 11.37 (standard error of the mean [SEM], 2.23) and 4.40 (SEM, 1.34), respectively. Both the post-task symptom change (P < .001) and the difference between the two reading conditions (P = .004) were significant. The mean change in critical fusion frequency after the digital and printed conditions was -0.42 (SEM, 0.25) and -0.72 (SEM, 0.26), respectively. Neither the post-task change nor the difference between the two reading conditions was significant. In addition, when considering the digital condition only, no significant correlation was observed between the changes in critical fusion frequency and reported symptoms. CONCLUSIONS: These results do not support the proposal that changes in critical fusion frequency can be used as an objective measure of eyestrain or other symptoms of digital eyestrain.