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L. A. Macfadden, L. S. Gray, N. C. Strang, D. Seidel; Monochromatic Higher Order Aberrations in Myopia and Hyperopia Before and After Cycloplegia. Invest. Ophthalmol. Vis. Sci. 2008;49(13):985. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To measure monochromatic higher order aberrations (MHOA) in myopic and hyperopic subjects, and determine the effect of cycloplegia upon these aberrations.
10 hyperopic (HYP: mean age 23.0±4.3 years; average MSE +5.69±0.83D) subjects and 10 myopic (MYO: mean age 23.4±2.76 years; average MSE -4.95±1.90D) participated with informed consent in the study. All subjects had VA of 0.0logMAR or better in both eyes and cylindrical correction of ≤1.00DC in each eye. 3 measurements of MHOA were obtained from both eyes using the Zywave aberrometer (Bausch & Lomb) and an average MHOA profile expressed as Zernike coefficients was calculated. Measurements were obtained pre- and post-cycloplegia, induced using 2 drops of 1.0% cyclopentolate hydrochloride separated by 5 minutes. Post cycloplegia measurements were obtained 40 mins after instillation of the cycloplegic. In all subjects, corneal asphericity was measured using the Orbscan (Bausch & Lomb) and axial length was measured using the IOLMaster (Zeiss).
Mean axial length in the HYP group (21.49±0.70mm) was significantly shorter (p<0.001) than the MYO group (25.77±1.37mm). The axial lengths of all subjects showed a significant (p<0.001) negative correlation with MSE (r=0.80). Mean corneal asphericity (-0.60±0.06) in the HYP group was significantly (p<0.001) greater than the MYO group (-0.31±0.08). Mean total 3rd order aberration post-cycloplegia (0.52±0.24) in the HYP group was significantly (p<0.001) greater than the mean pre-cycloplegia value (0.30±0.13). Mean spherical aberration post-cycloplegia (0.78±0.24) in the HYP group was significantly (p<0.0001) greater than found pre-cycloplegia (0.31±0.07). Also, the mean post-cycloplegia defocus term (9.63±2.53) in the HYP group was significantly (p<0.001) greater than pre-cycloplegia (6.21±2.84). By contrast, the MYO group showed no significant differences in any of these parameters pre- and post-cycloplegia. Pre-cycloplegia there were no significant differences between the MYO and HYP groups for any MHOA. Post-cycloplegia the mean spherical aberration in the HYP group was significantly (p<0.001) greater than that in the MYO group.
Spherical aberration is significantly greater in hyperopic eyes compared to myopic eyes when accommodation is paralysed. Compensation of corneal MHOA by crystalline lens MHOA is significantly greater in hyperopic eyes when accommodation is active. These results may have implications for our understanding of refractive error development.
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