|Title||PATTI PICS VS. SLOAN LETTERS: VISUAL ACUITY AND THE EFFECT OF CROWDING|
|Author, Co-Author||Diane Ah-Kine Ng Poon Hing, Elise Harb, Luisa Mayer, Li Deng|
Third Floor Foyer
|Abstract|| PURPOSE: Computerized visual acuity systems (CVAS) display pediatric optotypes in a variety of presentation modes. In addition to CVAS, newer pediatric optotypes have become commercially available. However little research has been done to see how these pediatric optotypes (e.g. Patti Pics (PP)) compare to a "gold standard" (e.g. Sloan letter (SL)) optotype. Moreover, there is little known about the effect of crowding on newer optotypes. The purpose of this study is to compare VA obtained with digital PP to SL in 3 different crowding conditions; (1) single optotype, (2) single optotype surrounded by contour interaction bars (CIB) and (3) single line surrounded by a rectangular outline (RO).
METHODS: 50 non-presbyopic adults with a best-corrected VA of 20/25 or better, with habitual correction, participated. All logMAR stimuli were presented on the Precision Vision CVAS (PVVAT). Stimulus presentation was randomized for both chart type and crowding type and all measurements were taken in one session.
RESULTS: Mean VA was significantly better with SL than PP (mean diff. single optotype= -0.036, single optotype with CIB = -0.014, single line with RO = -0.027; repeated measures ANOVA; p=0.01). Single optotypes with CIB yielded significantly worse acuities than the other 2 crowding conditions (repeated measures ANOVA; p<0.001). Mean VA for single optotypes with CIB was worse than the other 2 crowding conditions by approximately 0.06 logMAR for SL (paired t-tests; p<0.0005) and approximately 0.05 logMAR for PP (paired t-tests; p<0.005).
CONCLUSIONS: In adult subjects, logMAR VA for SL was better than for PP under all 3 crowding conditions. However, despite statistical significance, no difference was greater than 2 optotypes (0.036 logMAR). The crowding effect was generally the same for both SL and PP. Surprisingly, CIB surrounding a single optotype reduced mean acuity while a RO surrounding a single line did not, as compared to an isolated optotype. Further studies are necessary to evaluate crowding effects in pediatric and amblyopic populations.
|Affiliation of Co-Authors||New England College of Optometry, New England College of Optometry, New England College of Optometry|