Author: Howard D. Palte, M.B., Ch.B., FCA
ASA Monitor 02 2018, Vol.82, 22-25.
The Anesthesia Quality Institute (AQI) has included a new parameter in its 2017 Measure Specifications for the Merit-based Incentive Payment System (MIPS) Reporting.1 Item AQ128 measures the percentage of patients aged 18 years or older who undergo anesthesia care and do not have a new diagnosis of corneal injury prior to anesthesia end time. This measure is to be reported each time a patient undergoes a procedure with anesthesia not involving patients with pre-existing eye trauma or those patients undergoing ophthalmic surgery.
Anesthesiologists have an obligation to protect patients’ eyes, particularly during non-ocular surgery. As long ago as 1937, Guedel commented that there was “too much conjunctivitis and keratitis following anesthesia.” Today, the incidence of perioperative ocular injury is low (0.03-0.17 percent),primarily because there is heightened awareness of corneal abrasion with more attention paid to intraoperative eye care. However, postoperative eye complaints remain a source of patient distress and certainly contribute to lower patient satisfaction scores. Closed Claims Project analysis has affirmed that corneal abrasions are the most frequent ophthalmic complaint following non-ocular surgery.2
Anatomy
The cornea is an avascular structure protected by a pre-corneal tear film composed of three layers – lipid, aqueous and mucin. The outer lipid layer acts as a lubricant and prevents evaporation of the deeper aqueous layer that serves to oxygenate the corneal epithelium. The innermost mucin layer creates a hydrophilic coating that covers the surface of the cornea. The integrity of the tear film is maintained by involuntary blinking. Abolition of this reflex under general anesthesia renders the epithelial layer vulnerable to injury. Furthermore, the cornea is exquisitely sensitive to low tissue oxygenation, so hypoxic conditions rapidly result in swelling (edema) and a loss of epithelial integrity. This process can be initiated in as little as one minute.3 Finally, impedance of regional corneal perfusion from malposition of the head or conditions that elevate intraocular pressure (IOP) also predispose to corneal injury. A combination of these factors initiates a cycle resulting in abrasion of the cornea.
Pathogenesis
The majority of corneal abrasions occur secondary to incomplete closure of the eyelid (lagophthalmos). Under normal conditions, the orbicularis muscle keeps the eyelid closed when one falls asleep. There are a number of factors that contribute to genesis of corneal abrasions under general anesthesia (GA). First, GA reduces tonic contraction of the orbicularis muscle and incomplete closure of the eyelids that predisposes to exposure keratopathy. It is estimated that almost two-thirds of patients experience incomplete eyelid closure with induction of general anesthesia. Second, the hazard of lagophthalmos is potentiated by abolition of the blink reflex. Third, general anesthesia causes loss of Bell’s phenomenon, which is the natural upward turning of the eye during sleep. Finally, general anesthesia also reduces tear production resulting in drying of the cornea and increasing potential for development of a corneal abrasion. White et al.used fluorescein and slit lamp examinations to assess how rapidly general anesthesia produced corneal desiccation. They demonstrated epithelial changes within 100 minutes and eye erosions after 120 minutes of anesthesia.
Beside lagophthalmos and impaired tear production, the cornea is prone to injury from direct trauma. In this regard, harm may occur secondary to insults such as facemask pressure, dangling I.D. badges that scrape the eye during laryngoscopy or stethoscopes that are suspended around the neck. Chemical injury may occur from surgical prep solutions or benzoin applied to an unprotected eye. The only eye-friendly, non-toxic antiseptic skin preparation is preservative-free povidone-iodine in aqueous solution. An overlooked source of ocular insult is the iatrogenic injury that occurs secondary to the patient rubbing the eye during emergence or recovery with a digit that is attached to the pulse oximeter. Thus, it may be prudent to place the oximeter probe on the non-dominant hand.
“Postoperative eye complaints remain a source of patient distress and certainly contribute to lower patient satisfaction scores. Closed Claims Project analysis has affirmed that corneal abrasions are the most frequent ophthalmic complaint following non-ocular surgery.”
Risk Analysis
Several studies have addressed the question of patient profile and surgical procedures that increase risk for development of a corneal abrasion. Yu et al. found a higher incidence in patients having surgery in the prone and lateral position as well as those undergoing head and neck procedures.4 Roth et al. corroborated these findings, adding that prolonged surgery was an independent risk factor.5
It is important to identify patients with pre-existing dry eye syndromes and maintain them on their eye drop regimen. It is also useful to remember that anticholinergic agents reduce tear production and that routine administration of these agents may carry risk. Mechanically ventilated ICU patients are at high risk of developing a corneal abrasion, with an incidence as high as 60 percent. The factors promoting this phenomenon include administration of PEEP, increased venous pressure and resultant chemosis, and highflow rates of oxygen that desiccate the surface of the eye.
Prevention
Numerous protective strategies have been touted. Formerly, there was strong advocacy for use of ophthalmic lubricants that aim to maintain corneal integrity by counteracting the effects of decreased tear production. Two classes of ophthalmic lubricant are commercially available:
- 1. Paraffin-based: long duration (two hours)
- ■ May cause edema / blurred vision
- ■ Flammable – NOT for use in facial surgery
- 2. Methylcellulose-based: short duration (45 minutes)
- ■ No blurred vision
However, multiple studies have failed to establish that one class of lubricant has superior efficacy over the other. In fact, several studies comment that the effect is only sustained with repeated applications, especially during protracted surgery. Of note, the application of these lubricants onto the surface of the eye carries a remote risk of infection, so current recommendations favor use of single-dose lubricant aliquots.
In a neurosurgical population, Cucchiara et al. compared the efficacy of ocular lubricants in combination with eye taping versus eye tape alone, and failed to demonstrate that addition of a lubricant improved outcomes.6 Early taping of the eyelids is key and should be instituted on induction of anesthesia as soon as there is loss of the lid reflex, and prior to mask ventilation or laryngoscopy. In other words, early, correct taping of the eyelids in association with regular intraoperative lid closure checks provides effective protection against development of a corneal abrasion.
The pulse oximeter probe should be applied on either the ring or little finger of the non-dominant hand in order to avert ocular contact should patients rub their eyes on emergence. Also, eye tape should be removed carefully because the adhesive glue can abrade the eyelid, especially in elderly patients who may have fragile skin. The vertical placement of tape from the upper to the lower eyelid is not recommended because it carries risk for exposure keratopathy. Furthermore, it may result in direct mechanical injury to the cornea when tape is removed in the direction of lower to upper eyelid.
Presentation
- 1. Early postoperative period
- 2. Pain – mild
- 3. Scratchy, foreign body sensation
- 4. Blinking
- 5. Scleral injection and redness
- 6. Photophobia
Diagnosis
Definitive diagnosis is confirmed with a cobalt-blue filtered light and application of fluorescein. However, bedside application of a single drop of topical ophthalmic local anesthetic, such as proparacaine, relieves discomfort. An ophthalmology consultation is required when pain persists despite instillation of local anesthetic.
Management
Eye patching has been a cornerstone of management for many years. Several recent studies demonstrate that patching may delay healing. Current recommendations are that small abrasions require no specific intervention. Patients should be reassured that healing usually occurs in 24-72 hours. The use of LA drops is contraindicated because they impair corneal healing and may produce interstitial keratitis. Topical NSAIDS have been demonstrated to reduce pain, but the use of prophylactic antibiotic drops remains controversial.
Perioperative corneal abrasions are a source of morbidity in all surgical interventions, even those conducted under monitored anesthesia care. However, they are easily prevented when providers remain cognizant of eye care and take appropriate steps to protect against them. Effective preemptive measures include correct head positioning, avoidance of orbital pressure, early eyelid taping, frequent intraoperative checks for sustained closure and use of protective eyewear, especially for patients in the prone position.
References:
Anesthesia Quality Institute. 2017 AQI NACOR QCDR measure specifications for MIPS reporting. https://www.aqihq.org/files/2017%20MIPS/2017-06-19_FINAL_2017_QCDR_Measure_Booklet.pdf.
Gild WM, Posner KL, Caplan RA, Cheney FW . Eye injuries associated with anesthesia. A closed claims analysis. Anesthesiology. 1992;76(2):204–208.
White E, Crosse MM . The aetiology and prevention of peri-operative corneal abrasions. Anaesthesia. 1998;53(2):157–161.
Yu HD, Chou AH, Yang MW, Chang CJ . An analysis of perioperative eye injuries after nonocular surgery. Acta Anaesthesiol Taiwan. 2010;48(3):122–129.
Roth S, Thisted RA, Erickson JP, Black S, Schreider BD . Eye injuries after nonocular surgery. A study of 60,095 anesthetics from 1988 to 1992. Anesthesiology.1996;85(5):1020–1027.
Cucchiara RF, Black S . Corneal abrasions during anesthesia and surgery. Anesthesiology.1988;69(6):978–979.