Dilute topical proparacaine for pain relief after photorefractive keratectomy.
OBJECTIVE
The purpose of the study is to determine whether there is a nonanesthetic and nontoxic concentration of topical proparacaine that can be applied repeatedly to the cornea to reduce pain after photorefractive keratectomy (PRK).


METHODS
Part I: To determine a nonanesthetic concentration, the corneal sensitivity of 50 healthy volunteers was assessed using aesthesiometry before and after a drop of either 0.01%, 0.025%, 0.05%, 0.1%, or 0.2% topical proparacaine. Ten volunteers similarly were tested with multiple doses of 0.05% proparacaine. To evaluate toxicity, ten healthy volunteers self-administered 0.05% proparacaine to one eye and placebo to the other eye every 15 minutes for 12 hours on day 1 and every hour for 12 hours on days 2 through 7. Subjects were assessed throughout the week using visual acuity, slitlamp examination, aesthesiometry, and ultrasonic pachometry. Part II: In a prospective, double-masked study, 34 patients who underwent PRK (48 eyes) self-administered either topical 0.05% proparacaine or placebo for 1 week after PRK as needed to reduce pain. Patients recorded their pain score before and after drop use and answered a pain-relief questionnaire.


RESULTS
Part I: Proparacaine concentrations greater than or equal to 0.1% eliminated sensation from some corneas; concentrations of less than or equal to 0.05% were never fully anesthetic. No corneal toxicity was observed except for some minimal punctate staining in both treatment and placebo eyes. Part II: Patients in the treatment group had significantly more pain relief (P < 0.001) for a longer period (P < 0.001) than did patients in the control group. Average change in pain score was significantly greater in the treatment group (P < 0.002). No significant difference in the number of days needed to reach complete epithelial healing was found between the two groups (P < 0.18).


CONCLUSIONS
Dilute (0.05%) topical proparacaine is nonanesthetic and nontoxic, and can be used safely for at least 1 week to reduce pain after PRK.
Shahinian
L
L
Stanford University Department of Ophthalmology, Stanford, California, USA.
Jain
S
S
Jager
R D
RD
Lin
D T
DT
Sanislo
S S
SS
Miller
J F
JF
D000287:Administration, Topical; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000627:therapeutic use; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D006801:Humans; D054018:Lasers, Excimer; D009994:Osmolar Concentration; D010149:Postoperative Pain / Q000628:therapy*; D010166:Palliative Care; D018903:Photorefractive Keratectomy; D011430:Propoxycaine / Q000008:administration & dosage* / Q000627:therapeutic use; D011446:Prospective Studies; D016896:Treatment Outcome
D000779:Anesthetics, Local; C005717:proxymetacaine; D011430:Propoxycaine