A New Parameter for the Assessment of Distance Visual Capacity: the Critical Visual Acuity (CVA)

Development and Validation of a New Parameter for the Assessment of Distance Visual Capacity: the Critical Visual Acuity (CVA)

The conventional examination of the visual acuity (VA) does not take into account the patient's reading speed. However, the consideration of the speed for the recognition of the VA charts' symbols leads to the more accurate and comprehensive assessment of the visual capacity.

Therefore, primary objective of this study is to develop and validate a new parameter for the more comprehensive evaluation of visual capacity: the critical visual acuity (CVA). CVA takes into account the speed of recognition of the symbols of the distance visual charts.

Study Overview

• Status: Active, not recruiting
• Conditions: Visual Acuity
• Intervention / Treatment: Diagnostic test: VA assessment; Diagnostic test: CVA assessment

Detailed Description

In clinical practice, the conventional examination of the VA does not take into account the patient's reading speed, and does not reflect the requirements of everyday life (e.g. driving, watching subtitles on TV), in which each individual has limited time to react. In addition, the VA measured with the conventional method differs significantly among the different examiners, since there is no standard time limit for the patient to read the chart symbols.

However, the consideration of the speed for the recognition of the VA charts' symbols leads to the more accurate and comprehensive assessment of the visual capacity. Therefore, primary objective of this study is to develop and validate a new parameter for the more comprehensive evaluation of visual capacity: the critical visual acuity (CVA), and to determine normal values of population according to age. CVA takes into account the speed of recognition of the symbols of the distance visual charts.

Participants are recruited from the outpatient service of the Department of Ophthalmology of the University Hospital of Alexandroupolis in a consecutive-if-eligible basis. At first, each participant performs the conventional VA test monocularly. Then, he/she performs the CVA test with the same eye. Two different printed Landolt ring charts are used, the first one for VA and the second one for CVA assessment for all participants to avoid memorization. The VA and CVA are evaluated for all participants under the same environmental lighting conditions.

Regarding the VA and CVA examination procedure, the investigator masks the chart lines using a blank piece of paper and reveals one line each time. The investigator instructs the patient to read aloud the 5 letters of the Landolt chart, as quickly and accurately as possible, after hearing the words "Ready!… Go!". At the same time, a second examiner starts a stopwatch to record the reading time (in seconds, to the nearest 0.01 s) when the examiner fully reveals the line and the patient starts to read it. The first examiner counts the number of errors for each line and the second one enters the reading time for each line in a data file. The reading time of each line is compared with the automatically calculated average reading time of the larger lines minus 1.96 (for CVA) or 2.58 (for VA) times the standard deviation (SD) of the reading time of these lines.

Testing stops when the letters are too small for the examinee to discriminate and/or they are read with a speed lower than the maximum reading speed (MRS) of each examinee.

• Study Type: Observational
• Enrollment (Estimated): 300

Contacts and Locations

Study Locations

• Greece
  • Evros
    • Alexandroupolis, Evros, Greece, 68100
      • Department of Ophthalmology, University Hospital of Alexandroupolis

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 75 years (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

• Sampling Method: Probability Sample

Study Population

300 patients who will come to the outpatient clinics of the Ophthalmology Department of the University Hospital of Alexandroupolis, aged 18-75 years, will be examined.

Description

Inclusion Criteria:

• People aged 18 - 75 years

Exclusion Criteria:

• neurological diseases
• mental diseases
• mental retardation,
• difficulty reading
• previous intraocular surgery

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Testing of Visual Acuity (VA) Group; The same participants will undergo VA and CVA test with two different Landolt C charts under the same lighting conditions.	Diagnostic test: VA assessment; The VA of all participants will be evaluated by counting the smallest line that can be read within a time duration greater than or equal to the average reading time of the larger lines minus 2.58 times the SD of the reading time of these lines. In clinical practice, the VA is the common parameter of VA adding a tolerant time limit to clearly determine the end of the test.
Testing of Critical Visual Acuity (CVA) Group; The same participants will undergo VA and CVA test with two different Landolt C charts under the same lighting conditions.	Diagnostic test: CVA assessment; The CVA of all participants will be evaluated by counting the smallest line that can be read within a time duration greater than or equal to the average reading time of the larger lines minus 1.96 times the SD of the reading time of these lines. In clinical practice, the CVA is the minimum VA that can be read in maximal speed.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Critical Visual Acuity (CVA)	The smallest line (measured in letters) that can be read with the maximum reading speed, i.e., with speed greater than or equal to the average reading speed of the larger lines minus 1.96 times the standard deviation (SD) of the reading speed of these lines. In clinical practice, the CVA is the minimum VA that can be read in maximal speed.	6 months
Visual Acuity (VA)	The smallest line (measured in letters) that can be read with speed greater than or equal to the average reading speed of the larger lines minus 2.58 times the standard deviation (SD) of the reading speed of these lines. In clinical practice, the VA is the common parameter of VA adding a tolerant time limit to clearly determine the end of the test.	6 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Intraclass Correlation Coefficients (ICCs) for study participants	Level of agreement between CVA and VA are evaluated by calculation of the ICCs for these 2 parameters.	through study completion, an average of 3 months

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Test-retest Intraclass Correlation Coefficients (ICCs)	Test-retest reliability of the CVA test is evaluated by ICCs for the CVA parameter within 15 days	through study completion, an average of 3 months

Collaborators and Investigators

• Sponsor: Democritus University of Thrace
• Investigators: Study Chair: Georgios Labiris, MD, PhD, Department of Ophthalmology, University Hospital of Alexandroupolis, Alexandroupolis, Greece

Study record dates

Study Major Dates

• Study Start (Actual): September 20, 2020
• Primary Completion (Estimated): July 20, 2025
• Study Completion (Estimated): December 20, 2025

Study Registration Dates

• First Submitted: November 12, 2020
• First Submitted That Met QC Criteria: November 12, 2020
• First Posted (Actual): November 17, 2020

Study Record Updates

• Last Update Posted (Actual): July 11, 2025
• Last Update Submitted That Met QC Criteria: July 8, 2025
• Last Verified: June 1, 2025

More Information

Terms related to this study

• Keywords: maximum reading speed; critical visual acuity; visual capacity
• Other Study ID Numbers: ES12/Th3/17-9-2020

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No