Clinical Updates
Perioperative Corneal Abrasions: Etiology, Prevention, and Management
By Jonathan Anson, M.D., Instructor in Anesthesia, Penn State University College of Medicine
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Anatomy review
How corneal abrasions occur
Protection Strategies
Risk Factors
Confirming and treating corneal abrasion
Summary
References
Corneal abrasions are the most frequent ocular complications following general anesthesia, and are a painful burden to the recovering postoperative patient. The most recent (1992) ASA closed claim analysis showed that eye injury occurred in 3 percent of all claims in the database
(1). Of these claims, 35 percent represented corneal abrasions with a 16 percent incidence of permanent eye injury
(1).
Corneal abrasions can occur during general anesthesia, monitored anesthesia care, and regional anesthesia. Several strategies are widely used to try and prevent corneal abrasions, although there is a paucity of recent studies to support one method over another. This review will discuss common causes of peri-operative corneal abrasions and review the literature supporting various approaches to prevention. The basic management of this painful condition will also be discussed.
Anatomy review
In order to understand the causes of perioperative corneal abrasions some pertinent anatomy must first be reviewed. The cornea is an avascular structure composed of five histologically distinct layers. It is protected by a precorneal tear film composed of three layers: Lipid, aqueous, and mucin. The outermost lipid layer prevents evaporation of the aqueous layer and acts as a lubricant. The aqueous layer oxygenates the corneal epithelium, while the main function of the mucin layer is to create a hydrophilic surface on the corneal epithelium. The precorneal tear film is regenerated by blinking, thus the absence of blinking during general anesthesia renders the cornea vulnerable to injury.
The cornea is extremely sensitive to hypoxia and the partial pressure of oxygen in the cornea can decrease dramatically with as little as 30 seconds of hypoxia
(2). Corneal hypoxia leads to edema and potential for loss of the epithelial layer, causing an abrasion. Therefore, physiologic factors that alter corneal blood flow can predispose patients to corneal injury. This includes conditions that decrease arterial blood flow such as elevated intra-ocular pressure, head malpositioning, or pressure from an incorrectly applied face mask. Decreased venous return can similarly lead to corneal edema and subsequent abrasion.
(2). Normally lid closure while sleeping is maintained by the orbicularis muscles, but under anesthesia up to 59 percent of patients fail to have complete eye closure
(2). The risks of lagopthalmos are increased by the abolishment of both blinking and Bell’s phenomenon (normal upward turning of the eye while asleep) during general anesthesia.
General anesthesia reduces tear production which leads to corneal drying
(3). One small study demonstrated a significant decrease in basal tear production under general anesthesia. After one hour basal tear production decreased from a baseline of 13.6 ml per five minutes to just 0.9 ml per five minutes (P < 0.001)
(3). Corneal drying in the presence of lagophthalmos can lead to dry patches and corneal abrasion. The effect of anesthetic duration on tear production and risk of corneal abrasion was further demonstrated in a study utilizing fluorescein and a slit lamp to monitor the corneas of patients undergoing general anesthesia. The study concluded that corneal changes are evident after 100 minutes of anesthesia and eye erosions after two hours
(2). Other studies have similarly demonstrated that these changes peak around two hours and are not seen in anesthetics with less than a one hour duration.
While the majority of corneal abrasions are caused by lagophthalmos and changes in tear production induced by general anesthesia, traumatic injuries occur as well. These injuries are often caused by face-masks, dangling name badges, laryngoscopes, or “stethoscope necklaces” during airway management. Chemical injuries can occur from surgical prep cleaning solutions or application of benzoin without adequate eye protection. Post-operative eye injuries are most often attributable to patients rubbing their eyes, pulse oximeters, and bed linens. Applying the pulse oximeter probe to the 5th digit rather than the index finger may alleviate some of the corneal injuries that occur post-operatively.
(2). Parrafin based products can cause erythema and edema during halothane anesthetics as halothane is highly soluble in paraffin and high concentrations can result in inflammation, but this is not seen with newer volatile anesthetics.
Cucchiara, et al
(4) compared the effectiveness of eye ointment plus eye tape versus eye tape with no ointment. They looked at 4,652 neurosurgical patients, about half of which received ointment and eye tape while the rest had their eyes taped without ointment. Four patients in each group were found to have corneal abrasions post-operatively. Five of the eight patients were in the prone position. Thus, they were unable to show any protective effect of routine use of eye ointment in their neurosurgical patient population
(4).
(5). These were found to be more common in patients undergoing surgery in the prone or lateral position. Head and neck surgery, sustained hypotension, and anemia were also found to be risk factors
(5). The conclusions made by this group were supported in another retrospective study examining 60,965 at the University of Chicago. They similarly reported lateral position and head/neck procedures as risk factors for corneal injury. In addition, this study found that increased length of surgery was an independent risk factor
(6).
(7). Indications for referral to a specialist include: history of significant trauma, worsening of symptoms despite treatment, erosion, infiltrate around the edges of the abrasion (suggestive of infection)
(7). Corneal abrasions generally do not lead to long term complications, however, in rare instances the healed epithelium may be poorly adhered to underlying layers leading to recurrent corneal erosions.
Historically, eye patching has been utilized in the management of corneal abrasion. Recently, several studies have shown that patching is not helpful and may in fact delay healing (
7,
8). Small abrasions often do not need treatment and patients should be reassured that they heal within 24-72 hours. Topical non-steroidal anti-inflammatory drugs such as diclofenac or keterolac can be considered as they have been shown to reduce pain. The use of antibiotics is more controversial. The incidence of infection following corneal abrasion is <1 percent, however, some clinicians use prophylactic antibiotics because a concomitant infection will slow healing. A prospective cohort study of prophylactic topical antibiotics (chloramphenicol) did demonstrate a decrease in ulcer formation when started within 18 hours of injury
(9). Thus, antibiotic drops may be indicated to prevent ulcers. On the other hand, topical anesthetics should never be used as they can hinder healing, mask worsening symptoms, and lead to keratitis.
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