Abstract
Purpose: :
To measure wavefront aberrations centrally and peripherally before and after reading, and compare the changes between myopic and emmetropic subjects.
Methods: :
The Complete Ophthalmic Analysis System (COAS) was used to measure wavefront aberrations in the eyes of 25 young adult subjects (19 females, 6 males; mean age = 24.0 yrs). Fourteen were emmetropic (mean Rx = -0.15 D +/- 0.37) and 11 were myopic (mean Rx = -2.19 D +/- 0.73). Mean cylinder was -0.20 D. The COAS was aligned to the subject's right eye, while a mirror was aligned to the left eye in order to view a target 33 cm away with small fixation letters. Aberrations were measured centrally, at 10 and 30 deg nasally and 10, 20, and 30 deg temporally (n = 3 measurements at each position). After participants read a book for 1 hour, these measurements were repeated. Mean changes after reading at each retinal position were compared within and between refractive groups, using t-tests for total RMS, higher order (HO) RMS, and individual Zernike terms. Calculations were done for 4 mm pupils, with adjustment for elliptical pupils.
Results: :
Before reading, total RMS (mainly due to main axis astigmatism) and HO RMS were significantly higher for emmetropes than myopes in the far periphery, as previously reported (Beck et al, ARVO 2008). After reading, changes that were statistically significantly greater than zero were only found in myopes, and only at nasal 30 deg (total RMS p=0.017; HO RMS p=0.019). The changes in total RMS seen in myopes may be attributed to statistically significant increases in oblique and main axis astigmatism (p<0.05). Changes in total RMS and HO RMS after reading were not statistically significantly different between refractive groups at any retinal position.
Conclusions: :
To our knowledge, these are the first results suggesting that reading increases aberrations in the periphery of myopic young adults. In particular, reading induces more peripheral astigmatism in myopic eyes. The increase in whole eye aberrations can be attributed to changes in the cornea, as has been previously reported.
Keywords: aberrations • myopia