Presented by: Sarah Wong Orthoptist II Orthoptic Unit QA 2011

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

Introduction: Visual acuity (VA) is defined as: The sharpness of vision; a measure of how well a person can see

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.)

PVVAT

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

Snellen Linear Chart

Aim: To investigate whether the PVVAT system is a compatible visual acuity test VS standard Snellen Linear

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

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

Results:  Figure 3. A comparison of visual acuity scores obtained in the number of eyes tested with Snellen VS PVVAT

Results: Snellen better PVVAT better  Figure 4. A plot of visual acuity variation with Snellen/PVVAT to 100 eyes examined.

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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