Abstract
Purpose:
To investigate the relationship between refractive error, ocular axial length and accommodation in middle-aged Norwegians.
Methods:
Forty-one male and female subjects aged 43-50 yrs were recruited among university educated employees in a high-tech company and an academic institution in Kongsberg, Norway. Subjects were healthy with no known ocular abnormalities. Subjects were corrected to best monocular logMAR letter acuity with natural pupils at 3 m, we report the spherical equivalent refraction (SER). Ocular axial length was measured by partial coherence laser interferometry (Zeiss IOL Master; Carl Zeiss AG, Oberkochen, Germany). Accommodation amplitude was measured with a RAF rule while the subject viewed the N5 line.
Results:
Average ±SD SER was -0.2 ±1.4 D with average axial length 23.5 ±0.9 mm. logMAR visual acuity ranged between 0.02 and -1.04. Accommodation amplitude ranged between 2.3 to 5.1 D. There was a significant correlation with age for both measures of accommodation (Person r = 0.3-0.4, p<0.05), and the estimated loss of accommodation amplitude was 0.1 D per year. There was no correlation between age and axial length, but there was a correlation between axial length and accommodation amplitude (Pearson r = 0.3, p <0.05).
Conclusions:
Average SER values were closer to emmetropia than reported previously for middle-aged adults from the north of Norway (-0.51 ±1.75D, Midelfart et al. AOS 2002: 80:501-505). The rate of loss of accommodation was lower than the estimate based on Duane’s curve (-0.1 versus -0.4 D/per year: Duane TAOS 1922), indicating a latitude difference as suggested previously (Miranda, TAOS 1979: 77: 603-621). Interestingly, it seems like those with longer ocular axial length preserve their accommodation for longer.
Keywords: 404 accommodation •
653 presbyopia