Self-reported vision and reading measures: Young participants rated their near vision as significantly better than did older participants (t(22) = 3.07, p <.05). This self reported measure was not significantly correlated with near acuity (r(22) = 0.379, p >.05), however, it was correlated with near peak sensitivity (r(22) = -0.434, p <.05) and near mean sensitivity (r(22) = -0.423, p <.05). Elderly participants also reported more difficulty reading small print (t(22) = 3.77, p <.05). This rating was significantly related to near acuity (r(22) = 0.683, p <.05) as well as all near contrast sensitivity measures except near peak frequency and near high cutoff. No age group difference was reported in the amount of time spent reading (t(22) = 0.65 p >.05, see Table 3) nor on any other rating of near or far vision.
Table 3: Self-Reported Vision and Reading for Young and Elderly Participants
| Young |
Elderly |
||||
| Mean |
SD |
Mean |
SD |
Diff. | |
| Hours reading per day | 2.50 |
1.67 |
2.94 |
1.62 |
n.s. |
| Rating of near vision | 1.50 |
0.67 |
2.50 |
0.90 |
p<.05 |
| Difficulty of reading close | 1.25 |
0.45 |
2.33 |
0.89 |
p<.05 |
| |
1.83 |
1.19 |
1.25 |
0.45 |
n.s. |
| Importance of reading close | 3.17 |
1.11 |
3.58 |
0.51 |
n.s. |
| Problems with close work | 2.00 |
1.04 |
2.42 |
0.79 |
n.s. |
| Rating of far vision | 1.75 |
0.75 |
1.92 |
0.79 |
n.s. |
| Difficulty of distant reading | 1.67 |
0.65 |
1.83 |
0.58 |
n.s. |
| Frequency of distant reading | 1.33 |
0.65 |
2.08 |
1.44 |
n.s. |
| Importance of distant reading | 3.50 |
0.67 |
3.17 |
1.03 |
n.s. |
Acuity: The acuity of young participants was superior to that of the older participants (F(1,22) = 38.53, p <.05). Acuity did not differ significantly with test distance (F(1,22) = 2.00, p >.05), nor was there an interaction between age and test distance (F(1,22) = .05, p >.05). The latter finding suggested that the young and elderly participants were equivalently corrected for both distances (see Table 4).
Table 4: Spatial Vision Characteristics of Young and Elderly Participants (df = 22)
| Young |
Elderly |
||||
| Near Distance (36 cm) | Mean |
SD |
Mean |
SD |
T |
| Acuity | 0.68 |
0.08 |
1.22 |
0.28 |
|
| Peak Spatial Frequency | 4.17 |
0.58 |
3.37 |
1.67 |
0.98 |
| Mean Peak Contrast Sensitivity | 165.00 |
29.54 |
100.00 |
46.37 |
4.10 |
| Mean Contrast Sensitivity | 105.00 |
15.59 |
57.37 |
28.84 |
5.03 |
| |
8.88 |
1.48 |
8.10 |
2.16 |
1.04 |
| Far Distance (610 cm) | |||||
| Acuity | 0.59 |
0.10 |
1.15 |
0.42 |
|
| Peak Spatial Frequency | 7.00 |
2.34 |
7.25 |
2.99 |
0.23 |
| Mean Peak Contrast Sensitivity | 141.25 |
37.91 |
81.42 |
40.61 |
3.73 |
| Mean Contrast Sensitivity | 81.11 |
19.34 |
46.26 |
18.20 |
4.55 |
| |
16.63 |
4.57 |
13.99 |
3.38 |
1.61 |
Contrast sensitivity: An Age (2) by Spatial Frequency (5) mixed-model ANOVA on near contrast sensitivity (Geisser-Greenhouse corrected) was conducted. An overall difference was found in the CS function (F(4,19) = 48.46 p <.05). Younger participants demonstrated higher CS than elderly participants (F(1,22) = 25.33 p <.05). The CS function was not the same for both age groups (F(4,19) = 4.42 p <.05). Follow-up tests (with Bonferroni correction for 5 comparison, see Table 5) showed that the contrast sensitivity of the young participants was superior to that of the elderly participants at intermediate and higher spatial frequencies (i.e., 4, 8, and 12 c/deg). The age difference in near contrast sensitivity at the two lowest spatial frequencies (1 and 2 c/deg) was not significant. For the far contrast sensitivity measure, 50% of the observers were unable to correctly detect the grating orientation at 36 c/deg even at the highest contrast level, so data for this spatial frequency were not included in the analyses. An Age (2) by Spatial Frequency (4) mixed-model ANOVA was conducted. Younger participants demonstrated higher CS than elderly participants (F(1,22) = 18.01 p <.05) as well as differences in the CS function (F(4,19) = 36.68 p <.05). A significant interaction between stimulus frequency and observer age (F(4,19) = 3.55 p <.05) was found. Follow-up tests (with Bonferroni correction for 4 comparison, see Table 5) showed that young participants had superior contrast sensitivity at intermediate spatial frequencies (6 and 12 c/deg). The differences at the highest and lowest spatial frequencies (i.e., 3 and 24 c/deg), however, did not reach significance. The very high variability at the 24 c/deg for both the young (SD = 23.80) and older observers (SD = 14.58) precluded the large mean differences at this spatial frequency from reaching statistical significance. Near and far contrast sensitivity functions for younger and elderly observers are presented in Figure 3. Age differences in contrast sensitivity were also evaluated using several "composite" measures, including Peak Spatial Frequency, Mean Peak Contrast Sensitivity, Mean Contrast Sensitivity, and High Cut-off (i.e., the spatial frequency above the peak at which sensitivity fell to one-half its peak level). Mean Peak Contrast Sensitivity for young observers exceeded that of elderly observers for both near and far test distances. A similar age difference was observed in Mean Contrast Sensitivity for both near, and far test distances (see Table 4). Neither the spatial frequency at which peak sensitivity occurred nor the high cutoff differed by age for either test distance.
Table 5: Follow-up Analysis of Contrast Sensitivity Function for Near and Far Test Distances (df = 22)
| Near |
Far | ||||
| C/deg |
T Value |
Sig. |
C/deg |
T Value |
Sig. |
| 1 |
2.68 |
n.s. |
3 |
1.85 |
n.s. |
| 2 |
2.74 |
n.s. |
6 |
3.80 |
p<.0125 |
| 4 |
5.14 |
p<.01 |
12 |
3.37 |
p<.0125 |
| 8 |
4.35 |
p<.01 |
24* |
1.92 |
n.s. |
| 12 |
5.77 |
p<.01 |
|||
Figure 3 Near (36.0 cm) and far (610 cm) mean contrast sensitivity as a function of spatial frequency and age groups.