Comparison of Four Methods for Entering the Gap Position of Landolt Cs

Study Overview
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Brief Summary
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The aim of this study is to investigate and compare the validity of four different input methods for Landolt Cs, i.e. the proportion of correct gap positions in relation to the total number of performances. The four input methods are a numeric keypad, an eight-positions rocker switch, a remote control and voice feedback.

Detailed Description
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The measurement of visual acuity is the most frequent and one of the most important ophthalmological functional investigations. Therefore, it is particularly important to find a measuring procedure with as little input errors as possible. The 8-position Landolt C (LC) is the internationally accepted, well-standardised optotype for the determination of visual acuity. Usually, the subjects informs the examiner verbally about the perceived position of each LC. According to the current literature, about 20 to 30 % of the population suffers from a right/left weakness. Furthermore, language barriers are an additional considerable hurdle. Therefore, it is important to find an input method for the LC gap positions with minimal entry mistakes. In oder to avoid the thresholding procedure and its inherent difficulties, highly supra-threshold (10 times above the previously determined individual central visual acuity threshold) 8-position LCs are presented. The study compares four input methods for entering of the Landolt C gap positions: a modified numeric keypad, an 8-position rocker switch, a modified TV remote control and voice/verbal feedback. Each subject will perform all four input methods, with 2 test runs of 16 Landolt C presentations, each. A forced-choice method will be applied, i.e. the test is not continued until the test person has responded ot each single presentation. Regardless of whether the entry was correct or incorrect, the next Landolt C is displayed. The optotypes are presented using modified version of the Freiburg Visual Acuity and Contrast Test (FrACT), which allows to present the 8-position Landolt Cs in a standardized way on a video display unit (VDU). The sequence of the input methods is randomized. This study is carried out in a within-subject design, i.e. all test persons go through all test conditions and serve as their own controls.

Official Title
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Comparison of Four Methods for Entering the Gap Position of Landolt Cs With Respect to Validity, Retest Reliability, Examination Duration and Test Subject Satisfaction

Conditions
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Quality Control, Validation Study

Intervention / Treatment
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* Diagnostic Test: Landolt C entry method


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age: ≥ 18 years Informed consent (Distance) visual acuity with best correction: ≥ 0.8 (Distant) ametropia: ≤+8.0 Diopters (spherical equivalent) Anisometropia ≤ 3 dpt Astigmatism ≤ 2.5 dpt Exclusion Criteria: Prolonged reaction time caused by drugs (medications)/ drugs/alcohol Movement disorders (of hands) such as Parkinson's disease Indication of amblyopia (strabismus surgery, occlusion therapy etc.) Eye movement disorders/double vision Defective stereo vision (according to LANG [I] stereo test) Presence of a relative afferent pupil defect (swinging flashlight test) Any hint of visual pathway lesion or other chronic or progressive eye disease

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Intervention/Treatment |
| --- |
|Diagnostic Test: Landolt C entry method|Four different methods for entering the Landolt C gap position are compared|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| validity | Proportion of correct gap position entries in relation to the total number of LC presentations by the four different entry methods | Through study completion, an average of 3 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| retest reliability | Comparison of the correct gap position entry between first and second test run by the four different entry methods | Through study completion, an average of 3 months | 
| Examination duration | Comparison of the examination duration of the the four different entry methods and by the first and second run | Through study completion, an average of 3 months | 
| Subjects´ satisfaction | Subjects´ evaluation (using a questionnaire) for the four different entry methods | Through study completion, an average of 3 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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psychophysics, visual acuity, response, response entry, validity, retest reliability, reproducibility, evaluation, optotype, Landolt C