Plasminogen Activator to Prevent Haze After Laser Eye Surgery
Some fraction of patients who have laser vision correction develop haze (cloudy vision) several months after the surgery: about 8% to 10% of photorefractive keratectomy (PRK) patients and a smaller fraction of laser in situ keratomileusis (LASIK) patients. At present there is no pre-surgical predictor for the potential formation of haze, nor a preventative to eliminate the haze. A Johns Hopkins University Applied Physics Laboratory researcher, in collaboration with researchers in the Department of Ophthalmology at the University Medical School of Debrecen, has proposed the use of plasminogen activator (uPA) in the form of eyedrops after PRK or LASIK surgery as a prophylactic for preventing corneal haze from forming after the laser vision correction surgery.
Preliminary experiments on humans and rabbits indicate that the haze is a manifestation of an irregularity in the corneal healing process as evidenced by an abnormal plasminogen activator activity measured in tears over the course of several days after surgery. Tear samples were collected from 77 eyes of 42 patients immediately before and immediately after PRK treatment, and on postoperative days 3 and 5. In 20 patients, the contralateral eye was similarly sampled to serve as a control. Plasminogen activator behaviors in the tear samples were measured by spectrophotometric methods using human plasminogen and chromogenic peptide substrate. In the tears of all eyes that underwent PRK, the plasminogen activator activities were lower immediately after surgery. For patients’ eyes with normal wound healing, plasminogen activator activities were elevated above the preoperative level on the third postoperative day, and then returned to normal by the fifth postoperative day. In contrast, plasminogen activator activity remained low through the third postoperative day in all eyes in which haze developed after 3 to 6 months. The control eyes showed no appreciable change in plasminogen activator levels over the 5-day period. Hence the APL research shows extended low levels of plasminogen activator activity through the third postoperative day correlate with the development of corneal healing abnormalities (haze). The technology concept being researched at APL has found that administering plasminogen activator in the form of eye drops during the post-operative period will prevent the occurrence of haze. The proof of concept is currently being conducted to show that the haze formation can be prevented through the administration of plasminogen activator after surgery as a therapeutic preventative. The APL concept will further prove that the plasminogen activator is benign for those patients who would otherwise not develop haze. Since haze formation cannot be predicted, it is expected that all patients would be treated on a prophylactic basis. The APL proof of concept will form the basis for human clinical trials and FDA involvement.
Patent Status: U.S. patent(s) 7179461 issued. International patents issued.
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