Some letters, because of serifs, are easier to identify than others.Large gaps between visual acuity levels (20/80 - 20/200).Unequal spacing between letters and rows.Irregular progression in letter size from one line to another - gain or loss of one line of vision does not have same value in different parts of chart.Unequal numbers of optotypes per line - if child/student is required to accurately identify the majority of letters on each line, the definition of "majority" is not the same for each line.Though considered a standard screening chart, a Snellen chart has 6 critical design flaws: Herman Snellen (Dutch ophthalmologist) introduced his block letters with SERIFS in 1862. What is the difference between Snellen and Sloan letters? Have questions? Have our Pediatric Vision Screening Consultant contact you! > I understand how to use the charts but at what results for acuity does a referral need to be made? We purchased the LEA vision screening charts to use for our preschool program ages 3 to 5.What type of charts and guidelines are there for this age group? I am new at screening 3 year olds in my school.Why are the recommendations regarding Snellen and Sloan eye charts different? Which should be followed?.Do you have suggestions for screening children that cannot talk or match? Or children who have autism or severely multiply disabled?. ![]()
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