Analysis of optical side-effects of fs-laser therapy in human presbyopic lens simulated with modified contact lenses.

BACKGROUND

In a single-blinded study, optical side-effects of a potential femtosecond (fs)-laser therapy in presbyopic human lenses were tested. Simulation of this therapy was carried out by applying fs-laser patterns into standard contact lenses (CL).

METHODS

In the first part of the study, the influence of the numerical aperture on optical side-effects was investigated by comparing a typical fs-LASIK configuration to a fs-presbyopia treatment (n = 11). The second part focused on a possible improvement of visual performance by comparing a regular grid pattern to a randomly chosen spacing of the laser spots (n = 16). Visual acuity was measured with ETDRS charts, contrast sensitivity with F.A.C.T. charts and mesopic vision with Mesotest II. Forward scattered light was measured with the C-Quant (both instruments: Oculus Optikgeräte GmbH, Germany). A questionnaire detected subjective quality of vision. Differences between laser-treated and untreated CL and among the modifications were analyzed.

RESULTS

The laser-treated and standard CL indicated no significant difference in visual acuity, contrast sensitivity and mesopic vision without glare. While wearing modified lenses with a regular grid, quality of vision decreased significantly by means of mesopic vision with glare and subjective straylight. These modifications also caused an impairment of subjective quality of vision. In contrast, there was no significant difference between the random pattern and standard CL.

CONCLUSION

The increase of optical side-effects was reproducibly dependent on the geometry of the laser-structure. A randomized grid induced the least limitation. The study results are useful for planning possible laser-patterns in fs-laser therapy of the presbyopic lens.