Corrigendum: Using a Computerised Staircase and Incremental Optotype Sizes to Improve Visual Acuity Assessment Accuracy.

[This corrects the article DOI: 10.22599/bioj.271.].

Using a Computerised Staircase and Incremental Optotype Sizes to Improve Visual Acuity Assessment Accuracy.

Background: Given the impact of visual acuity results on diagnosis and management, it is essential that the test is accurate, determined by factors such as test-retest variability. Standardisation improves accuracy, which can be performed via a computerised staircase methodology. Standard clinical tests with scoring of 0.02 per optotype implies an incremental score per optotype despite optotype size remaining constant on each line. The aim of this study is to establish if near continuous incremental optotype display and scoring improves test-retest variability compared to current testing methods. Methods: A computerised three up, one down adaptive staircase was used to display Kay Picture optotypes on an LCD monitor. Three methods of visual acuity assessment were undertaken: ETDRS, Kay Pictures and computerised Kay Pictures. Tests were performed twice under standard clinical conditions. Results: One hundred nineteen adults were tested. Test-retest variability for computerised Kay pictures was 0.01 logMAR (±0.04, p = 0.001). Good levels of agreement were observed for computerised Kay pictures in terms of test-retest variability, where the test had the smallest mean bias (0.01 logMAR compared to 0.03 and 0.08 logMAR for Kay Pictures and ETDRS respectively) and narrowest limits of agreement. Participants performed better in computerised Kay pictures than Kay Pictures by 0.03 logMAR, and better in ETDRS than computerised Kay pictures by 0.1 logMAR. Conclusion: Computerised Kay pictures exhibited a low test-retest variability, demonstrating it is reliable and repeatable. This repeatability measure is lower than the test-retest variability of the ETDRS and Kay Pictures tests.

Initial evaluation of a virtual reality bomb-defusing simulator for development of undergraduate healthcare student communication and teamwork skills.

Communication and teamworking skills are essential healthcare professional skills, yet undergraduates exhibit reluctance to engage with group work, especially in interprofessional groups. The aim of the study was to investigate whether a virtual reality bomb-defusing simulator would enable students to gain these skills through an enjoyable and challenging scenario without profession-specific knowledge. Students took it in turns to play the role of the 'Defuser' immersed in a headset, while the rest of the group were 'Experts' with a printed manual, but no sight of the bomb. The task challenged students to relay obscure symbols and instructions to each other rapidly and effectively. A subsequent focus group explored the impact of the simulation on students' perceived learning, engagement and communication skills. The focus group of five multiprofessional healthcare students reported high levels of engagement and satisfaction while highlighting value in developing communication and teamwork. The simulator nurtured initial group dynamics and team bonding. Evaluation data indicated that the intervention facilitated cooperation, team bonding and the development of good communication skills. This method of encouraging communication would fit well into an interprofessional learning session as a useful tool ahead of more technical and clinically based group work. The focus group of five multiprofessional healthcare students reported high levels of engagement and satisfaction while highlighting value in developing communication and teamwork. The simulator nurtured initial group dynamics and team bonding.

The effect of induced fusional demand on static and dynamic stereoacuity thresholds: the digital Synoptophore.

BACKGROUND/AIMS: The ability to extract depth from disparity may be hindered under fusional stress, as alignment of the eyes may be more difficult to maintain consistently. Therefore we aim to determine the effect of fusional demand on stereoacuity in individuals with no known binocular vision impairments. METHODS: A novel static and dynamic binocular depth detection task, capable of assessing many discrete levels of stereoacuity, was presented on digital displays attached to each tube of the Synoptophore. Stereoacuity was measured with any latent deviation fully corrected and compared to that measured at the 'recovery' angle. This recovery angle is where single vision is restored after decompensation to diplopia, during vergence range assessment. RESULTS: Seventy-two subjects (50 Female, 22 Male; mean (SD) age 22 (6) years) were assessed. The amount of fusional demand was between 1 and 26 prism dioptres (PD), with a mean (SD) of 8(6)PD. Under zero fusion demand the mean (SD) static and dynamic depth detection thresholds were 322(53)" and 69(23)". Under fusional stress these were 224(40)" and 77(21)". There was no significant difference between thresholds in stressed and zero demand fusion (p = 0.08). Dynamic depth detection thresholds were significantly lower than static (P < 0.01). CONCLUSION: Fusional stress does not appear to impact on stereoacuity. The numerical value of the recovery point varied amongst individuals, but this represents a common point, where single vision is easily restored and binocularity well established. Due to individual differences in the ability to control a certain amount of fusional stress (e.g. vergences stress of 10PD, when recovery is 8PD, will perturb binocularity more than a person with a recovery of 20PD), previous reports may not accurately represent the effect of fusional stress. Whilst our findings are contrary to previous reports, we did not stress fusion beyond the recovery point and used a more accurate/repeatable method to measure stereoacuity.

Could Modifying the Bagolini Glasses Improve the Reliability of Responses?

AIMS: Bagolini striated lenses are a useful test of binocular vision, but the variations in the striations (frequency and thickness) can impact on the perceived image. Also, responses can be difficult to interpret in young children. Therefore, the aims of this project were to evaluate the impact of striation frequency and the addition of coloured filters on subjective responses. METHODS: Three sets of striated lenses were made (small, medium and large striations), each produced in two forms (both lenses clear, or with a red and blue lens). Also, Bagolini glasses (Optiker Ryser) were used, with and without the addition of red and blue filters. Subjects were asked to report what they perceived, with subsequent questions regarding the number and length of lines. RESULTS: Forty-two adult subjects were tested, with uniocular VA ranging from -0.18 to 1.10 logMAR (mean 0.08 ± 0.25). The number of lines seen when varying the line thickness did not vary between coloured and clear lenses (post-hoc analysis following ANOVA, p > 0.1 in all comparisons). Adding red/blue filters to the original Bagolini glasses did not alter the rates of subjects perceiving a cross (Chi-square, p = 0.8). However, the laser-cut lenses produced a significantly shorter light streak than the original lenses (One-way ANOVA, p < 0.001), but the colour of the filters made no difference to the length of streak perceived (Tukey's Test, p = 0.20). CONCLUSIONS: The addition of coloured filters did not impact on the responses given to the original or laser-cut lenses, suggesting this modification may aid responses in children. However, further evaluation is required with finer striations and thinner lenses to improve the visibility of the lines.

Stereopsis: are we assessing it in enough depth?

The assessment of stereoacuity is an integral part of the ophthalmic assessment, with the responses used to inform clinical management decisions. Stereoacuity impacts on many aspects of life, but there are discrepancies reported where people without measurable stereoacuity report appreciating 3-D vision. This could be due, in part, to the presentation of the stimuli. A literature review was undertaken to evaluate current assessment techniques, how they relate to patient outcomes, identify the limitations of current tests and discuss how they could be improved. Recent evidence has been collated on currently available tests, used commonly within vision clinics, with normative data provided allowing responses to the tests to be interpreted. The relevance of the results is evaluated in relation to a range of outcomes, where a reduced level of stereopsis has a negative impact on the ability of an individual to perform many tasks, and can lead to an increase in difficulty interacting in the world. Current tests are limited in the aspects of stereoacuity they assess and their ability to precisely measure stereopsis. The world is not static, yet clinical tests are limited to measuring static stereoacuity, even though higher grades of depth perception can be identified in the presence of changing depth. Presentation methods of stereoacuity tests have remained similar over time, with a limited number of disparity levels assessed. New assessment methods are becoming available that include automated staircase testing to present multiple levels of disparity using digital technology. Current clinical tests are limited in their presentation, and are poor at detecting/measuring stereoacuity in those with limited stereopsis. Given the relevance of the stereoacuity measurement to management choices and functional outcomes, new testing methods would be beneficial to fully assess stereoacuity, both static and dynamic.

Normative Values for Near and Distance Clinical Tests of Stereoacuity.

PURPOSE: Extensive literature exists on normative stereoacuity values for younger children, but there is less information about normative stereoacuity in older children/adults. Individual stereotests cannot be used interchangeably-knowing the upper limit of normality for each test is important. This report details normative stereoacuity values for 5 near/distance stereotests drawn from a large sample of participants aged 16-40 years, across 3 studies. METHODS: Participants (n=206, mean age 22.18±5.31 years) were administered the following stereotests: TNO, Preschool Randot, Frisby, Distance Randot, and Frisby-Davis 2. Medians and upper limits were calculated for each test. RESULTS: Upper limits for each stereotest were as follows: TNO (n=127, upper limit=120" arc), Preschool Randot (PSR, n=206, upper limit=70" arc), Frisby (n=206, upper limit=40" arc), Distance Randot (n=127, upper limit=160" arc), and Frisby-Davis 2 (n=109, upper limit=25" arc). CONCLUSIONS: Normative values for each stereotest are identified and discussed with respect to other studies. Potential sources of variation between tests, within testing distances, are also discussed.

A Systematic Comparison of Static and Dynamic Cues for Depth Perception.

PURPOSE: A clinical diagnosis of stereoblindness does not necessarily preclude compelling depth perception. Qualitative observations suggest that this may be due to the dynamic nature of the stimuli. The purpose of this study was to systematically investigate the effectiveness of static and dynamic stereoscopic stimuli. METHODS: Stereoscopic stimuli were presented on a passive polarized stereoscopic monitor and were manipulated as follows: static disparity (baseline condition), dynamic disparity (change in z-location), change in stimulus pattern, change in z-location with pattern change, change in x-location (horizontal shift), a control (nil-disparity signal). All depth-detection thresholds were measured simultaneously using an adaptive four-alternative-forced-choice (4AFC) paradigm with all six conditions randomly interleaved. RESULTS: A total of 127 participants (85 women, 42 men; mean [SD] age, 21 [5] years) with visual acuity better than 0.22 logMAR in both eyes were assessed. In comparison to the static disparity condition, depth-detection thresholds were up to 50% lower for the dynamic disparity conditions, with and without pattern change (P < 0.001). The presence of a changing pattern in isolation (P = 0.71) or a horizontal shift (P = 0.41) did not affect the thresholds. CONCLUSIONS: Dynamic disparity information facilitates the extraction of depth in comparison to static disparity signals. This finding may account for the compelling perception of depth reported in individuals with no measurable static stereoacuity. Our findings challenge the traditional definition of stereoblindness and suggest that current diagnostic tests using static stimuli may be suboptimal. We argue that both static and dynamic stimuli should be employed to fully assess the binocular potential of patients when considering management options.

Fiat Lux: the effect of illuminance on acuity testing.

PURPOSE: To determine the effect of changing illuminance on visual and stereo acuity. METHODS: Twenty-eight subjects aged 21 to 60 years were assessed. Monocular visual acuity (ETDRS) of emmetropic subjects was assessed under 15 different illuminance levels (50-8000 lux), provided by a computer controlled halogen lighting rig. Three levels of myopia (-0.50DS, -1.00DS & 1.50DS) were induced in each subject using lenses and visual acuity (VA) was retested under the same illuminance conditions. Stereoacuity (TNO) was assessed under the same levels of illuminance. RESULTS: A one log unit change in illuminance level (lx) results in a significant change of 0.060 LogMAR (p < 0.001), an effect that is exacerbated in the presence of induced myopic refractive error (p < 0.001). Stereoacuity scores demonstrate statistically significant overall differences between illuminance levels (p < 0.001). CONCLUSIONS: The findings of this study demonstrate that changes in illuminance have a statistically significant effect on VA that may contribute to test/retest variability. Increases in illuminance from 50 to 500 lx resulted in an improved VA score of 0.12 LogMAR. Differences like these have significant clinical implications, such as false negatives during vision screening and non-detection of VA deterioration, as the full magnitude of any change may be hidden. In research where VA is a primary outcome measure, differences of 0.12 LogMAR or even less could affect the statistical significance and conclusions of a study. It is recommended that VA assessment always be performed between 400 lx and 600 lx, as this limits any effect of illuminance change to 0.012 LogMAR.

Clinical Assessment of Stereoacuity and 3-D Stereoscopic Entertainment.

BACKGROUND/AIMS: The perception of compelling depth is often reported in individuals where no clinically measurable stereoacuity is apparent. We aim to investigate the potential cause of this finding by varying the amount of stereopsis available to the subject, and assessing their perception of depth viewing 3-D video clips and a Nintendo 3DS. METHODS: Monocular blur was used to vary interocular VA difference, consequently creating 4 levels of measurable binocular deficit from normal stereoacuity to suppression. Stereoacuity was assessed at each level using the TNO, Preschool Randot®, Frisby, the FD2, and Distance Randot®. Subjects also completed an object depth identification task using the Nintendo 3DS, a static 3DTV stereoacuity test, and a 3-D perception rating task of 6 video clips. RESULTS: As intraocular VA differences increased, stereoacuity of the 57 subjects (aged 16-62 years) decreased (eg, 110", 280", 340", and suppression). The ability to correctly identify depth on the Nintendo 3DS remained at 100% until suppression of one eye occurred. The perception of a compelling 3-D effect when viewing the video clips was rated high until suppression of one eye occurred, where the 3-D effect was still reported as fairly evident. CONCLUSION: If an individual has any level of measurable stereoacuity, the perception of 3-D when viewing stereoscopic entertainment is present. The presence of motion in stereoscopic video appears to provide cues to depth, where static cues are not sufficient. This suggests there is a need for a dynamic test of stereoacuity to be developed, to allow fully informed patient management decisions to be made.