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

Validation Study Clinical Trial

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

Status Completed

Clinical Trial Summary

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.

Clinical Trial Description

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. ;

Related Conditions & MeSH terms

• Quality Control
• Validation Study

• NCT number: NCT04299659
• Study type: Observational
• Source: Aalen University
• Status: Completed
• Start date: July 22, 2022
• Completion date: June 30, 2023