Confocal microscopy useful tool to evaluate corneal subbasal nerves after refractive surgery

May 4, 2005

Most corneal subbasal nerves disappear immediately following PRK and LASIK and take several years to return to near preoperative densities, according to William M. Bourne, MD, who presented the effects of refractive surgery and topical glaucoma therapy on corneal nerve morphology during the Association for Research in Vision and Ophthalmology annual meeting.

May 4

- Fort Lauderdale, FL - Most corneal subbasal nerves disappear immediately following PRK and LASIK and take several years to return to near preoperative densities, according to William M. Bourne, MD, who presented the effects of refractive surgery and topical glaucoma therapy on corneal nerve morphology during the Association for Research in Vision and Ophthalmology annual meeting.

Using confocal microscopy, researchers can accurately measure the density of subbasal nerves prior to and following refractive surgery. In a small study of 18 patients who underwent PRK and 16 who underwent LASIK, Dr. Bourne of the Mayo Clinic, Rochester, MN, reported that it took longer for corneal subbasal nerves to return to near preoperative densities in LASIK eyes than PRK eyes. It takes about 5 years for these nerves to recover after LASIK compared with 2 years following PRK, he said.

Researchers also found in a subset of patients from the Ocular Hypertension Treatment Study (OHTS) that topical glaucoma therapy can also affect corneal subbasal nerve density.

"Subbasal nerve density decreased by 40% in patients treated with long-term topical anti-glaucoma drug therapy," Dr. Bourne said.

In addition, researchers need to be aware of possible artifacts with confocal microscopy that can change visibility of nerves in longitudinal studies. These artifacts include changes in intensity of illumination, changes in camera and microscope parameters, and effect of increased scattered light, he said.