Multifocal corneal topographic changes with excimer laser photorefractive keratectomy.
Excimer laser photorefractive keratectomy can flatten the central cornea, thereby eliminating myopic refractive errors; in older patients, however, presbyopia limits satisfaction. Computer-assisted topographic analysis of corneas after refractive surgery indicates that a minority of patients achieve a multifocal lens effect, such that they maintain reasonable acuity over a range of defocus. We have purposefully attempted to create a multifocal refractive effect and have analyzed the subsequent topographies quantitatively to determine if multifocality was achieved. In corneas not operated on and plastic hemispheres, a fairly small range of corneal powers is observed; the range of powers is increased after a monofocal ablation. After multifocal ablations, a greater spread of surface powers is observed, often with a bimodal distribution, indicative of an apparent multifocal effect. These observations suggest that in some patients undergoing photorefractive keratectomy for myopia, it may be possible to reduce symptoms of presbyopia, although a decrease in image contrast or monocular diplopia may complicate this approach.
Moreira
H
H
Doheny Eye Institute, Los Angeles, CA 90033.
Garbus
J J
JJ
Fasano
A
A
Lee
M
M
Clapham
T N
TN
McDonnell
P J
PJ
D000818:Animals; D003196:Computer Graphics; D003315:Cornea / Q000601:surgery*; D053685:Laser Therapy; D008768:Methylmethacrylates; D009216:Myopia / Q000601:surgery*; D011817:Rabbits
D008768:Methylmethacrylates