Visual Ability Score -- a new method to analyze ability in visually impaired children.

PURPOSE: We analyzed the correlation between the Preferential Looking (PL) acuities and the Visual Ability Scores (VAS) of 600 patients (many with severe retinopathy of prematurity) to determine their ability to perform various activities within the daily environment. METHODS: Visual acuity was measured by PL. Sixteen visual activities within the environment were analyzed. The VAS (range, 1-16) were calculated from the results of each activity and correlated with PL acuity. RESULTS: The PL acuities of the 600 patients ranged from 20/20 (1.0) to <20/3200 (0.006) [mean, 20/337(006)]. The VAS ranged from 1 to 16 points (mean, 10.65; SD, +/-4.80) and showed a high correlation with the PL acuities (r=0.917, p=0.0001). CONCLUSIONS: In addition to PL vision testing, analyzing the environmental visual behavior of young, severely visually impaired patients is important to accurately evaluate visual abilities. We found the VAS to be an important aid for low-vision specialists, especially for those with no access to a vision evaluation system such as PL.

Correlating preferential looking visual acuity and visual behavior in severely visually handicapped children.

We developed a series of questions that reflects the functional abilities of severely visually handicapped children. The study population comprised 100 patients aged 30 to 60 months (mean 43.23), mostly afflicted with retinopathy of prematurity. Visual acuity was measured by preferential looking. Preferential looking acuities of the patients ranged from 20/25 (0.8) to 20/6400 (0.003) (mean 20/470 (0.04)). Ten activities were analyzed and correlated with preferential looking acuity. Among the selected visual activities, when children are not interested in television (p = 0.0001), toys (other than those that make sounds (p = 0.0001), and people (p = 0.001)), their preferential looking acuities were very low. For example, 73 out of 100 patients who were visually interested in television had preferential looking acuities (mean 20/245 (0.082)) that were significantly higher (p = 0.001) than 21 patients not interested in television (mean 20/2806 (0.007)). Patients with nystagmus (n = 79) had significantly lower preferential looking acuities (p = 0.0001) (mean 20/1114 (0.018)) than patients with no nystagmus (mean 20/57 (0.35)). When evaluating visual function in young, severely visually impaired patients, in addition to preferential looking testing, analyzing visual behavior within the environment is important to accurately evaluate their remaining visual abilities.

Measuring vision with temporally modulated stripes in infants and children with ROP.

PURPOSE: To determine differences in preferential looking (PL) acuities using stationary and temporally modulated stripe patterns in patients with various stages of retinopathy of prematurity (ROP). METHODS: We measured the PL acuities of 134 patients (ages 4 mo to 13 yr) with various stages of ROP. Patients were divided into six subgroups according to PL vision measured with stationary stripes: (1) equal to or better than 20/200 (n = 24); (2) worse than 20/200 to 20/400 (n = 10); (3) worse than 20/400 to 20/800 (n = 15); (4) worse than 20/800 to 20/1600 (n = 13); (5) worse than 20/1600 to 20/6400 (n = 26); and (6) worse than 20/6400 (n = 46; no stationary vision). RESULTS: In the group with PL acuity equal to or better than 20/200, no difference in vision was apparent between the two methods. In patients with acuities worse than 20/200 to 20/400, the temporally modulated PL acuities were 0.23 octave better than the PL acuities measured with the stationary stripes. The difference increased to 0.86 and 1.12 octaves in the groups with visual acuities worse than 20/400 to 20/800 and worse than 20/800 to 20/1600, respectively. The difference in the group with PL acuities worse than 20/1600 to 20/6400 was 1.69 octaves. The 46 patients with no stationary vision detected only the temporally modulated stripes. CONCLUSIONS: The results suggest that the PL acuity difference between the temporally modulated and stationary stripes increases with visual impairment. Measuring PL acuity with temporally modulated stripes is an important addition to the evaluation of severely visually impaired subjects.

Visual hand display (VHD) as an introductory procedure for measuring vision in infants and young children with visual impairment.

We developed the Visual Hand Display (VHD) to measure vision in visually impaired infants and young children. The VHD is a circular fabric mitten, which is held easily by inserting the hand between the two surfaces. Black-and-white stripes are attached to one surface, 25, 15, 10, 4, and 2 mm per stripe. The VHD acuity is determined by the shortest test distance and the smallest stripes that the patient can detect. The VHD acuities were compared with preferential looking (PL) staircase acuities in 130 patients (53 males, 77 females; age range, 2 to 13 years; median, 21.0 months). Of these, 107 (82.3%) had various degrees of retinopathy of prematurity. The correlation between the VHD and the PL acuities was high (R2 = 0.849). PL acuities were better than the VHD acuities in 98/130 patients (75.4%), with an average difference of 0.51 (SD = 0.70) octave. The visual acuity differences were more pronounced in subjects with slight visual impairment and much less in subjects with severe visual impairment. The VHD seems to be an effective introductory method to evaluate visual acuity in severely visually impaired infants and young children. This method also would be effective with severely mentally and physically disabled patients who cannot undergo PL testing.