Abstract
Purpose: :
During dynamic focusing, the shape, as well as the internal ultrastructure of the lens is changed. Our lab is investigating changes in the ultrastructure, specifically at the sutures, of the lens during accommodation. We have hypothesized that unique structural features and organization of fiber cells enables them to interface at the sutures resulting in a change in surface curvature of the lens, allowing near focus to occur. We are currently using slit lamp and sequential ray tracing analysis of the patterns associated with the sutures to provide additional insight into the importance of the ultrastructure of the lens in the accommodative process. To further support our hypothesis, we are investigating changes in higher order aberrations in various states of accommodation. Preliminary observations are being reported here.
Methods: :
Wavefront analysis and accommodative response using the iTrace (Tracey Technology, Houston, TX) was collected on normal subjects, between the ages of 20-35 (n=26). Data were collected from the right eye as the subject viewed a lighted distance, then near target (40 cm) with their normal correction using their left eye. Accommodation was stimulated using minus lenses in 2.5 D increments until the subject could no longer clearly view the target. Data were preliminarily analyzed using SPSS to measure correlations between zernike polynomials for the internal optics (mostly lens) of the eye and accommodative response. We focused mainly on those indicative of suture patterns (trefoil, tetrafoil, pentafoil, hexafoil, and heptafoil). Correlation coefficients and p values are presented.
Results: :
When analyzed as raw data (n=74), there was a correlation between accommodative response and trefoil (C6 : 0.234, p=0.045), tetrafoil (C10 : -0.234, p=0.045 and C22 : 0.232, p=.047) and pentafoil (C15 : -0.226, p=0.050). From these preliminary results, further analysis of combined Zernike polynomials is needed. In addition, higher level of accommodation are needed, so if using this type of system, the impact of convergence on the aberrations needs to be reduced.
Conclusions: :
There are changes in higher order aberrations that may be indicative of a role for the lens fiber interactions at the sutures during accommodation. Further research investigating these patterns during growth and aging, as well as during accommodation is needed. A potential use of these patterns in detecting early problems with vision may be useful in a clinical setting.
Keywords: accommodation • aberrations