Corneal Abrasion Clinical Trial
Official title:
Effect of Tetracaine on Pain Management and Corneal Healing in Patients With Acute Corneal Abrasion
Corneal abrasions are associated with significant discomfort during a 24-48 hrs healing
phase. Current practice guidelines discourage the use of topical anesthetics in treating
these patients due to concerns that these medications may prevent proper corneal epithelial
healing. These concerns are based primarily on decades old animal based research. However,
recent evidence suggests topical anaesthetics are a safe and effective way of managing
patient pain in the short term. This study will investigate the effect of topical 0.5%
tetracaine on corneal healing and pain management in patients with corneal abrasions in the
first 48 hours.
This will be a prospective, double blind, randomized, controlled study of 260 adults with
uncomplicated acute corneal injuries presenting to the tertiary acute care settings in
Kingston. Patients will be randomly assigned to receive either 0.5% tetracaine or saline in
addition to usual care as outpatients. They will be followed through the ophthalmology
emergency eye clinic to assess healing at 36-48hrs. after the acute care visit. The primary
outcome will be an assessment of pain as measured every 4 hours for 48 hrs. using a 10mm
Visual Analogue Scale (VAS). Secondary outcomes will include assessments of corneal healing,
use of adjunct pain medications, time lost from work/usual activities, quality of sleep,
ability to read and the SF12 quality of life questionnaire.
This study will better inform the safety and effectiveness of short-term tetracaine usage in
patients with simple corneal abrasions for optimal treatment of patients in the future.
Corneal abrasions are commonly encountered eye injuries presenting to acute care settings and
account for over 10% of new ophthalmological presentations at eye accident departments,
primary care offices, and emergency departments. Patients complain of severe eye pain,
foreign body sensation, pain with blinking, and photophobia. Corneal abrasions are defects in
the epithelial layer that occur secondary to mechanical ocular surface trauma. Common causes
of corneal abrasions include fingernail injuries, tree branches, and projectile pieces of
metal, wood, or glass that injure or become embedded in the cornea. . Though associated with
significant discomfort, the prognosis for simple corneal abrasions is usually excellent, with
full recovery within 24-48 hours. Untreated abrasions, particularly those associated with a
retained foreign body, can lead to complications such as corneal ulcers, prolonged pain, and
visual acuity loss.
Currently, the standard approach to treating corneal abrasions includes removal of the
foreign body if present, oral analgesics for pain control, and topical antibiotics.
Traditional guidelines by ophthalmologists have advocated against the use of topical
anesthetics due to concerns with corneal epithelial healing the potential for patients to
miss important clinical clues that indicate the rare development of secondary corneal
infection, as well as the potential for longer term misuse leading to severe corneal
ulceration and perforation. Previous studies, primarily using animal models, have found a
delay in corneal epithelial healing with topical anaesthetics, particularly with repeated and
prolonged usage. Several case studies have described impaired corneal epithelial healing and
ulceration with the prolonged use and abuse of topical anesthetic drops (0.05% proparacaine
HCl). There have been reports of topical anesthetic (TA) induced corneal damage including
punctate epitheliopathy, corneal lysis, perforation, persistent epithelial defects, and
ocular inflammation. It is thought that local anesthetics inhibit mitosis and cellular
migration, preventing proper re-epithelialization of the cornea.
However, in recent years a number of randomized clinical trials and case studies of human
subjects have shown that with appropriate application and restricted short term usage,
topical anesthetics did not delay wound healing or increase risks of corneal ulceration.
A recent prospective, randomized, double-blind trial looked at the effect of topical
anesthetics on epithelial healing and pain management for patients with uncomplicated corneal
abrasion. The study included 116 patients presenting to the emergency department who were
given either 1% tetracaine HCl or control artificial tears. The study found no change in
corneal healing rate or persistent symptoms but little benefit in pain relief as measured at
48 hrs. A previous prospective randomized study comparing 0.05% proparacaine and placebo has
shown a significant decrease in reported pain with topical anesthetic use compared to control
with no change in corneal healing. Another study evaluating the effect of 1% tetracaine for
pain management after photorefractive keratectomy also reported significant pain reduction
with topical anesthetic use with no delays in epithelial healing.
Controversy continues to exist over the utility of topical anesthetics in managing pain and
their safety in affecting corneal healing. Contemporary studies of short term topical
anesthetic use, noted above, have not shown adverse effects on healing. Differential effects
on pain management have been found. Yet the investigators believe the Waldman study measured
pain at a delayed time when the abrasion would be expected to have healed. Clinicians in
Queen's Department of Emergency Medicine do not generally prescribe topical anesthetics for
corneal abrasions and believe that evidence demonstrating their efficacy and safety would
change practice patterns for the benefit of patients with these injuries and those in other
centres. The investigators also hope that this study will better address problems of
inadequate participant enrollment and retention that previous studies have encountered.
1.3 - Research Question In adult emergency department patients with acute corneal abrasions,
is the application of 0.5% tetracaine effective in the short-term management of pain while
not being associated with adverse effects on healing?
1.4 - Hypothesis Based on the review of existing literature on the effects of topical
anesthetics, the investigators hypothesize that short-term and controlled usage of tetracaine
will be an effective way in managing patient pain and will not affect corneal healing.
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