Abstract
Purpose:
Tests of visual acuity, stereoacuity, and refractive error are common components of preschool vision screening programs. An increasing number of these tests are becoming commercially available. The purpose of the present study is to provide the first normative pediatric data for three such tests, namely, the Precision Vision Visual Acuity Testing (PVVAT) system, the Pass Test 3 Stereo Test, and the PlusoptiX S09 Vision Screener.
Methods:
The participants included 267 children between the ages of 3 and 5 years (Mean=4.2±0.8years) participating in a preschool vision screening study. The children completed monocular testing with the PVVAT system, a computerized test of visual acuity. The optotypes used were isolated Patti Pics symbols surrounded by crowding bars. Stereoacuity was assessed using the Pass Test 3 Stereo Test, a random-dot test similar to the Random Dot E Stereo Test. Refractive error was measured using the Plusoptix S09 Vision Screener, which provides automatic, noncycloplegic estimates of refractive error. The mean and 95% tolerance limits were determined for each test.
Results:
Visual acuity improved significantly from 0.32 logMAR at 3 years to 0.18 logMAR at 5 years (p<0.0001). The lower tolerance limit improved from 0.59 logMAR at 3 years to 0.38 logMAR at 5 years. Stereoacuity also improved, decreasing from 120 arcsec (lower tolerance limit = 294 arcsec) at 3 years to 87 arcsec (lower tolerance limit = 220 arcsec) at 5 years (p=0.0015). Spherical refractive error remained stable at 0.27D (lower tolerance limit at 3 years = 1.33D; lower tolerance limit at 5 years = 0.91D; p=0.81), while cylindrical refractive error was also relatively stable, measuring 0.39D (lower tolerance limit = 1.00D) at 3 years and 0.37D (lower tolerance limit = 0.93D) at 5 years (p=0.90).
Conclusions:
Both visual acuity and stereoacuity improved significantly from 3 to 5 years of age. Note however, the norms obtained using the PVVAT system were somewhat lower than those reported in previous studies using different tests. The stability of spherical refractive error is unusual to some extent in that these children are undergoing emmetropization, but it does agree with a previous study providing noncycloplegic estimates of refractive error in children.