This prospective, randomized, clinical study evaluated the efficacy and safety of transcutaneous electrical stimulation (TES) to accelerate corneal nerve regeneration and improved recovery from corneal hypesthasia after laser-assisted in situ keratomileusis (LASIK). At Khodadoust Eye Hospital in Shiraz, Fars, Iran, 40 eyes of 20 patients were scheduled to undergo bilateral LASIK.

One eye of each patient was randomly assigned to receive TES (20 Hz) for 60 minutes and the other eye was allocated as the control. Corneal sensitivity was measured using the Cochet-Bonnet esthesiometer in four areas outside and five areas inside the LASIK flap preoperatively, and at 1 day, 1 week, 1 month and 3 months postoperatively. Best-corrected visual acuity and the incidence of adverse events were noted at each visit.

Normal corneal sensitivity was maintained throughout the study for all four points outside the LASIK flap and no significant difference was found between the study eyes and the control eyes at these points (p>0.05). All points within the LASIK flap except the point closest to the hinge demonstrated profound corneal hypoesthesia at 1 day, 1 week and 1 month postoperatively, with no differences noted between the control and study eyes (p>0.05). After 3 months, points within the flap had statistically significantly better corneal sensitivity in the study group than in the control group (p<0.05).

It was determined that transcutaneous electrical stimulation significantly improves corneal sensitivity at 3 months after LASIK, which may be a result of accelerated corneal nerve regeneration by electrical stimulation.

Spanish researchers sought to determine the levels of proinflammatory cytokines and matrix metalloproteinase 0 (MMP-9) in tears from both eyes of unilateral keratoconus (KC) patients.

They studied 30 patients diagnosed as having asymmetrical KC (30 KC eyes and 30 subclinical KC eyes) as well as 20 normal control subjects (one eye) in this prospective, cross-sectional study. Additionally, they performed keratoconus screening programs on each participant and collected 10 microliters of tears from each eye. Using enzyme-linked immunosorbent assay (ELISA), the researchers measured the concentrations of cytokines (interleukin-6 [IL-6], tumor necrosis factor [TNF]) and MMP-9.

Mean values for IL-6 levels were similar in KC and subclinical KC samples (5.5 [4.9 to 6.9] vs. 5.7 [4.5 to 6.2] pg/ml, p=0.131), but were significantly higher in relation to the control group (2.2 [1.0 to 4.1] pg/ml, p<0.0001). The researchers found significant differences in TNF levels between KC and subclinical KC eyes (5.4 [4.1 to 6.8] vs. 4.8 [4.2 to 6.0] pg/ml, p=0.032) and the control group (1.8 [1.5 to 2.3] pg/ml, p<0.0001). Furthermore, they found increased values of MMP-9 in KC (59.4 [50.6 to 66.1] ng/ml vs. subclinical KC eye (7.0 [4.8 to 8.6] ng/ml) (p<0.0001). MMP-9 levels in the control group (6.1 [3.9 to 8.3] ng/ml) and subclinical KC were similar (p=0.203).

According to these researchers, IL-6 and TNF- are overexpressed in the tears of subclinical and KC eyes. They found increased MMP-9 levels only in the KC eye. They believe their findings indicate that the pathogenesis of KC may involve chronic inflammatory events.