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Presented by: Sarah Wong Orthoptist II Orthoptic Unit QA 2011
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Contents: Introduction -Definition of v isual acuity -An overview of the two visual acuity test types -PVVAT system (new) -Snellen Linear (Traditional) Aim - To determine if PVVAT system is a compatible visual acuity examination as to Snellen Linear Methods - A comparison of visual acuity measured with PVVAT system VS Snellen Linear Results - Graphs illustration Conclusion
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Introduction: Visual acuity (VA) is defined as: The sharpness of vision; a measure of how well a person can see
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Introduction: An overview of PVVAT System PVVAT stands for (Precision vision visual acuity testing) PVVAT is a new visual acuity testing device that was incorporated in the orthoptic unit for routine visual acuity testing in 2010 PVVAT is a software program and uses a computer monitor screen for testing Testing distance 1m (min.) – 8m (max.)
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PVVAT
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Introduction: An overview of Snellen linear A traditional visual acuity test type A light box comprises of Snellen linear chart “E” Chart Numbers Chart Single Chart Testing distance at 6m
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Snellen Linear Chart
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Aim: To investigate whether the PVVAT system is a compatible visual acuity test VS standard Snellen Linear
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Methods: A sample of 100 eyes were randomly selected from patients attended orthoptic unit Sample age ranged from 5 years - 83 years old Each eye was first measured with Snellen linear Again, measured with PVVAT system Compare the visual acuity scores from the two test types in each eye
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Results Descriptive Table 1: Visual acuity (VA) scores in each eye of the sample population examined (n=100) measured using Snellen and PVVAT. Column 1: n=number of eye tested Column 2: VA scores with Snellen ( 6/ ) Column 3: VA scores with PVVAT (6/ ) Column 4: VA difference with Snellen-PVVAT
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Results: Figure 3. A comparison of visual acuity scores obtained in the number of eyes tested with Snellen VS PVVAT
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Results: Snellen better PVVAT better Figure 4. A plot of visual acuity variation with Snellen/PVVAT to 100 eyes examined.
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Conclusion: 92% of the eyes in this sample group achieved the same visual acuity scores with Snellen as with PVVAT 8% of the eyes scored one line difference 7% of the eyes scored reading Snellen better than PVVAT 1% of the eyes scored reading PVVAT better than Snellen linear PVVAT system is compatible to Snellen linear for measuring visual acuity.
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