Of the 130 study subjects, there were 111 Chinese (85.4%), 12 Malays (9.2%), and 7 Indians (5.4%), and the average age was 21.2 ± 1.1 years (range, 19–24). The mean spherical equivalent was −5.9 ± 3.5 D (range, −0.25 to −14.25 D). Forty-six (55%) subjects ranged from −0.25 to −4.00 D, 49 (38%) from greater than −4.00 to −8.00 D and 35 (27%) greater than −8.00 D. The mean axial length was 26.0 ± 1.43 mm (range, 23.22–29.23). The longest axial length of 29.23 mm was within the focusing range of the machine. The axial length correlated significantly with the spherical equivalent (Pearson correlation coefficient = −0.84, P < 0.0001). Simple regression of RT-Min measurement variance as the dependent variable and axial length as the independent variable yielded P = 0.26.
The OCT macular thickness measurements are summarized in
Table 1 . The average macular thickness (overall) was 230.9 ± 10.5 μm. ANOVA showed no difference between myopia and mean macular thickness (
P = 0.73). Using simple linear regression, mean macular thickness did not relate to axial length (
P = 0.37) or to spherical equivalent (
P = 0.69). The mean RT-Max was 278.4 ± 13.0 μm. RT-Max showed a negative correlation with axial length (
P = 0.03) with a slope of −1.77 μm/mm
(Fig. 3) , but was not correlated with spherical equivalent (
P = 0.48). The mean RT-Max (sup), RT-Max (inf), RT-Max (temp), and RT-Max (nas) were 288.3 ± 18.0, 278.4 ± 15.1, 262.2 ± 14.6, and 284.2 ± 17.1 μm, respectively. RT-Max (sup) decreased with increasing axial length (
P = 0.003) at a rate of −3.27 μm/mm. RT-Max (inf) decreased with increasing axial length (
P = 0.008) at a rate of −2.47 μm/mm. RT-Max (temp) and RT-Max (nas) were not related to axial length. The mean RT-Min was 141.1 ± 19.1 μm. RT-Min increased with axial length (
P = 0.015;
Fig. 4 ) and increasing spherical equivalent (
P = 0.0002).
Figure 5shows the lack of relationship between the variance of RT-Min measurements and increasing axial length (
P = 0.26).