Present study aims to develop and validate a web-based digital distance visual acuity test (Democritus Distance Vision Test - DDVIT). DDVIT is an application, which will be easily accessed through a simple internet connection. This application will provide the possibility of a simple but reliable examination of patients, establishing a commonly accepted way of measuring the distance visual acuity among rural doctors, general practitioners and ophthalmologists.~Specifically, present study aims to develop a new online distance visual acuity test (DDVIT) according to the standards of the Early Treatment Diabetic Retinopathy Study (ETDRS) test and to evaluate the level of agreement between the two visual acuity tests, as well as the test-retest reliability of the online DDVIT visual acuity test.~The first part of the study is the development of the online visual acuity test (letters, numbers, symbols) including the following smart features:~Adjustment of the font size according to the size of the computer screen used for the examination~Real time calculation of the patient-screen distance through a face detection system~Automatic calculation of the reading time of each line (each logMAR)~Entering the number of patient's reading errors for each line~Automatic calculation of the visual acuity in the following score units:~Number of Letters (max 85)~Visual Acuity Score (max 100)~logMAR~Decimal~Snellen Fraction~The calculation of various reading parameters resulting from the aforementioned features (visual acuity score in different units, reading duration (in sec) and number of errors for each slide (line), patient-screen distance for each slide) will be performed after the end of the examination. Except for the html format, a file in the format of Microsoft Excel and Pdf are also generated.~The second part of this study is the clinical validation of the DDVIT visual acuity test. In this part, the reading acuity measured with the DDVIT and ETDRS test are compared.~All the comparisons will take place in two groups: a) a Normal Vision Group (NVG), and b) a Low Vision Group (LVG) in order to estimate the visual acuity in a population with a wide range of vision.
Primary objective of this study is the development and validation of a web-based application for the examination of the distance visual acuity of normal- and low-vision patients.