Literature and Discussion:
Many injuries sustained during anaesthesia are due to human error and may be avoided through high standards of clinical practice. Ocular injury occurs during 0.1- 0.5 % of general anaesthetics when eyes are taped and is usually corneal in nature1,2. This incidence has been reported at 44% in one study of untaped eyes during general anaesthesia3.Eye injuries account for 2% of medico-legal claims against anaesthetists in Australia and United Kingdom1,3 and 3% in the USA4.
Affect of General Anaesthesia on Eyes
General anaesthesia reduces the tonic contraction of the orbicularis oculi muscle, causing lagophthalmos ie. the eyelids do not close fully in 60% of patients1.
In addition, general anaesthesia reduces tear production and tear-film stability, resulting in corneal epithelial drying and reduced lysosomal protection. The protection afforded by Bell’s phenomenon (in which the eyeball turns upwards during sleep, protecting the cornea) is also lost during general anaesthesia5.
Mechanism of Injury
Corneal abrasions are the most common injury; they are caused by direct trauma, exposure keratopathy3,6,7or chemical injury6,8.
An open eye increases the vulnerability of the cornea to direct trauma from objects such as face masks, laryngoscopes, identification badges, stethoscopes, surgical instruments, anaesthetic circuits, or drapes.
Exposure keratopathy refers to the drying of the cornea with subsequent epithelial breakdown9. When the cornea dries out it may stick to the eyelid and cause an abrasion when the eye reopens10.
Chemical injury can occur if cleaning solutions such as Betadine, chlorhexidine or alcohol are inadvertently spilt into the eye, such as when the face or mouth is being prepped for surgery2,3.
Therefore, the anaesthetist must ensure that the eyes are fully closed and remain closed throughout the procedure, in order to avoid exposure keratopathy. Seemingly trivial contact can result in corneal abrasion and the risk of this occurring is markedly increased if exposure keratopathy is already present3.
Corneal abrasions can be excruciatingly painful in the postoperative period, may hamper postoperative rehabilitation and may require ongoing ophthalmological review and after care. In extreme cases there may be partial or complete visual loss.
Methods to Prevent Eye Injuries
Methods to prevent perioperative corneal injuries include simple manual closure of the eyelids, taping the eyelids shut, use of eye ointment (although this is controversial, see below), bio-occlusive dressings and suture tarsorrhaphy. However, none of the protective strategies are completely effective; vigilance is always required ie. the eyes need to be inspected regularly throughout surgery to check they are closed1.
Problems with current methods
For many years, in most western countries, the eyes of patients undergoing general anaesthesia have been routinely taped or stuck down with adhesive dressings in an attempt to combat these problems.
Unfortunately many of the adhesives used on medical products today are temperature and time sensitive ie. their adhesive strength may increase or decrease when applied to a 37 degree Celsius body11 and the longer they are applied, the greater the variability in their adhesiveness. What may seem the perfect adhesive strength before application can change as the operation progresses; leading to failure of stick or “over stickiness”. In the former case, the eyelids may move apart and in the latter, may cause bruising, eyelid tears and eyelash removal.
Rolls of tapes are often “laying around” the operating theatre and may not be hygienically clean12. Most of these tapes are translucent and so it is not possible to see if the patient’s eyes are opened or closed throughout the case. It is not uncommon for the eyelids to move open as the case progresses, even with adhesive tapes stuck onto them.
In a practical sense, these medical tapes/dressings may be difficult to remove from a patient because their ends can become stuck flush with the skin.
As noted above, there have been several studies looking at the efficacy and safety of eye ointments/lubricants as adjuncts with tape or as a stand-alone management for intra-operative eye closure. Unfortunately many in common use have problems. Petroleum gel is flammable and is best avoided when electrocautery and open oxygen are to be used around the face. Preservative-free eye ointment is preferred, as preservative can cause corneal epithelial sloughing and conjunctival hyperemia8; they have been implicated in blurred vision in up to 75% of patients.
They do not protect from direct trauma5,13.
Adverse Outcomes Associated With Intra-operative Injuries
|Increased length of stay.||Due to ophthalmology consults required, associated infections and treatment13|
|Increased costs.||Due to increased length of stay, cost of treating the complications14|
|Pain and discomfort for patient.||Corneal abrasions are extremely painful for the patient and the treatment consists of drops and ointments applied in the eye which may cause discomfort for the patient13,14|