Learning retinoscopy: A journey through problem space.

PURPOSE: Retinoscopy is a skill that requires the integration of procedural skill and declarative knowledge. Whilst the actual technique is simple, retinoscopy is a complex skill to acquire and is one that students often find challenging. This study compared the strategies that novices, third-year students and experts use when performing retinoscopy, with the aim of identifying the key stages of learning that may enlighten teaching practice. METHOD: This study employed a protocol-based approach in which the verbal protocols and cognitive strategies of novices, students and experts were recorded and then subjected to 'problem space' analysis. RESULTS: Clear differences existed when the retinoscopy of novices, students and experts was directly compared using a standardised simulated task. Experts were more accurate in performance and used defined strategies to reach the goal. The presence of these strategies significantly predicted the accuracy of the retinoscopy result. CONCLUSION: This study highlights the importance of meta-cognitive strategies and the need for an adequate theoretical foundation in skill acquisition. The underpinning knowledge provides a pedagogic tool that specifies activities which are beneficial to learning a clinical skill.

Intermediate, Wholistic Shape Representation in Object Recognition: A Pre-Attentive Stage of Processing?

Evidence is presented for intermediate, wholistic visual representations of objects and non-objects that are computed online and independent of visual attention. Short-term visual priming was examined between visually similar shapes, with targets either falling at the (valid) location cued by primes or at another (invalid) location. Object decision latencies were facilitated when the overall shapes of the stimuli were similar irrespective of whether the location of the prime was valid or invalid, with the effects being equally large for object and non-object targets. In addition, the effects were based on the overall outlines of the stimuli and low spatial frequency components, not on local parts. In conclusion, wholistic shape representations based on outline form, are rapidly computed online during object recognition. Moreover, activation of common wholistic shape representations prime the processing of subsequent objects and non-objects irrespective of whether they appear at attended or unattended locations. Rapid derivation of wholistic form provides a key intermediate stage of object recognition.

Use of visual search in the assessment of pattern-related visual stress (PRVS) and its alleviation by colored filters.

PURPOSE: Visual search measures have been used to evaluate the effects of pattern-related visual stress (PRVS), and its alleviation by colored filters, but tasks and results have varied between studies. Performance on a high-difficulty search task was measured in individuals having low- and high-PRVS susceptibility. METHODS: Two PRVS groups (low and high) were formed on the basis of participants' responses to a visual symptoms questionnaire and perceptions of a high-contrast grating pattern. Each participant searched for multiple instances of a single-digit number (target) within an array of similar numbers (distractors). Performance was measured by response time and error count. A three-factor, mixed-factorial ANOVA design was used to investigate the effects of PRVS group, a high-contrast background PATTERN, an overlay of an individually-selected COLOR. RESULTS: Individuals classified with high visual stress were found to experience significantly greater improvement in reading performance (F((1,26)) = 24.579, P < 0.001) and reduction in the number of errors (F((1,26)) = 9.502, P = 0.005) when performing the Wilkins Rate of Reading Test with a colored overlay than those with low visual stress. Error count was significantly higher in the high-PRVS group, when subjects were performing a visual search task, in the absence of either PATTERN or COLOR, but response time was not significantly different. Neither response time nor error count was significantly affected by background PATTERN and/or colored overlay. CONCLUSIONS: Results of this and previous studies confirm that visual search measures may be helpful in the assessment of PRVS, but several important methodological issues may limit their application in this context.

Screening for Meares-Irlen sensitivity in adults: can assessment methods predict changes in reading speed?

Two methods of assessing candidates for coloured overlays were compared with the aim of determining which method had the most practical utility. A total of 58 adults were assessed as potential candidates for coloured overlays, using two methods; a questionnaire, which identified self-reported previous symptoms, and a measure of perceptual distortions immediately prior to testing. Participants were classified as normal, Meares-Irlen sensitive, and borderline sensitive. Reading speed was measured with and without coloured overlays, using the Wilkins Rate of Reading Test and the change in speed was calculated. Participants classified as normal did not show any significant benefit from reading with an overlay. In contrast, a significant reading advantage was found for the borderline and Meares-Irlen participants. Current symptom rating was found to be a significant predictor of the change in reading speed, however the previous symptom rating was not found to be a reliable predictor. These data indicate that the assessment of perceptual distortions immediately prior to measuring colour preference and reading speed is the most meaningful method of assessing pattern glare and determining the utility of coloured overlays.