PK patients show nerve morphology deficits postop

Patients who underwent penetrating keratoplasty showed no regenerated subbasal nerves up to 12 months postop, a study found.

"The apparent recovery of corneal sensitivity to normal levels 12 months postoperatively, in the absence of clinically observable subbasal nerves, may be a methodologic phenomenon related to the inability of current-generation confocal microscopes to image fine regenerating nerves that mediate corneal sensibility," the authors said.

Taym Darwish, MSc, PhD, and colleagues evaluated subbasal nerve regeneration, corneal sensitivity and tear film function in 20 PK patients before and 1, 3, 6 and 12 months postop using noncontact corneal esthesiometry, tear breakup time measurement, the phenol red thread test and confocal microscopy. They published their results in the September issue of Cornea.

The researchers used subbasal nerve images produced by customized software to evaluate nerve regeneration. However, they could image the subbasal nerve plexus in only 11 patients preoperatively because of existing pathology, the authors noted.

Additionally, the researchers compared the PK patients' results with assessments of 10 healthy control subjects on one occasion, according to the study.

The researchers observed significant deficits in nerve morphology in the PK patients compared with the control subjects. Specifically, no subbasal nerves were detected in the PK patients over the 12-month period postop, the authors reported.

In addition, central corneal sensitivity decreased significantly after surgery in the PK patients, but returned to near normal levels after 12 months postop. Tear breakup time was also significantly shorter at 3 and 12 months postop, they found.

"There were no significant differences in the phenol red thread test results before and after surgery," the authors noted.

"There is no direct association between subbasal nerve fiber regeneration, central corneal sensitivity, and tear film stability and volume," they said.