Incidence, risk factors and impact of protocolised care on exposure keratopathy in critically ill adults: a two-phase prospective cohort study

Exposure keratopathy (EK) (Fig. 1) is a clinical syndrome characterised by incomplete eye closure and tear film defect leading to corneal damage of a spectrum of severity and extent [1]. A myriad of risk factors predisposes critically ill patients to EK, ranging from iatrogenic causes such as mechanical ventilation [2], sedation [3, 4] and muscle relaxants [5], to patient factors such as reduced consciousness [3], reduced tear production [6‐8], reduced blink rate [6, 9], impaired corneal reflex [8, 10], incomplete eye closure [2, 11] and vascular permeability [10]. The EK rate in critically ill patients has been reported as low as 10% to as high as 55–60% [2]. Although usually EK resolves once the patient recovers, it is a distressing condition and can cause corneal scarring and permanent visual loss [12]. At worst, EK precipitates microbial keratitis leading to acute perforation, endophthalmitis and permanent visual impairment [13].

In view of this, efforts have been made to prevent EK [14]. Many strategies such as moisture chamber, lubrication and artificial tears have been developed [15‐19]. Nevertheless, in an environment where the patient is suffering from acute life-threatening conditions, there is a lack of attention to issues such as EK, which may carry no immediate threat [20]. Therefore, a multidisciplinary focused approach is needed if EK is to be prevented, rather than simple prescriptions. Simply raising awareness of eye care through education of healthcare professionals working in an ICU reduces the rate of EK substantially without any changes to prescribed treatment [21]. Furthermore, formalised guidelines and protocols, when incorporated in patient care plans, can significantly reduce the rate of EK [22, 23].

Guidelines or protocols need to be simple to be effective. Significant adherence issues arise with detailed and complicated protocols [14]. The most pertinent risk factors need to be identified to develop a simplified eye assessment and management plan. However, to date, there is no widely accepted eye care protocol for prevention of EK in critically ill patients.

There were 371 patients included in this study, with 257 included in the first phase and 114 included in the second phase (Fig. 4). Patient characteristics in the control group and the intervention group were well-matched (Table 1).

In the largest study of its kind to date, we have shown that the introduction of protocolised eye care in critically ill patients, developed in conjunction with the multidisciplinary team, substantially reduced the incidence and duration of EK. It was the first study to date to assess the development of EK in patients admitted to the ICU pre and post implementation of protocolised eye care. Early detection, treatment and daily follow up of EK meant that the majority of patients developed only a mild form of EK, with quick resolution. However, if left untreated, mild EK is highly likely to progress to a more severe form.

In the first-phase, the overall rate of EK, its timing of development and its rate in patients with mechanically ventilated lungs were similar to the findings of others [2, 24, 25]. Studies reporting lower prevalence are either retrospective in nature [8] or carry out examination infrequently [23]. Consistent with our findings, the relationship between incomplete eye closure [2‐4, 11] or mechanical ventilation [2, 3, 26] and developing EK is widely documented. The SOFA score was associated with EK development; however, the APACHE II score on admission had little effect. The SOFA score is calculated daily and exclusively takes into account multiple organ dysfunction while the APACHE II score is calculated only once within 24 hours of admission and measures physiological derangement and co-morbidities. Therefore, it may be that organ dysfunction is more important in the development of EK than admission physiological derangement. Due to severe collinearity between sedation and mechanical ventilation, it was statistically impossible to calculate their individual effects independent of each other. Other factors such as P_mean and chemosis had no statistically significant effect on the development of EK. This may be because they can be considered as surrogate markers for incomplete eye closure and independently, with complete eye closure, they have little effect on the development of EK. Studies that report an association between chemosis and EK do so only in patients with concurrent eyelid malposition [3, 4].

Many different preventative techniques have been investigated in eye care [15‐19], principally moisture chamber techniques and lubrication. However, no one method is shown to be superior [17‐19]. Our adopted lubrication method (Lacri-Lube) was popular with the nursing staff due to familiarity and its effectiveness in treating EK in the first phase of the study. The frequency and intensity of intervention for different at-risk groups in the protocol is at the same level as was used for treating EK in those groups during the first phase of the study, thus selecting a very low threshold for preventing EK. Taping the eyelid is an effective method of preventing EK in incomplete eye closure [27]; however, as others [23] and we have found, it can increase the relative’s distress so in our protocol it is restricted to night-time as an option. We have kept the assessment simple and restricted it to the main risk factor identified in the first phase of the study i.e. incomplete eye closure and mechanical ventilation or sedation. A myriad of complex assessment methods have been suggested [22, 28, 29] but given adherence to a protocol is already a major issue [14], a complex assessment is likely to exacerbate the situation.

The strengths of this study are determining the rate of EK and its risk factors in a large sample size with patients having a wide range of severity of illness, daily ophthalmic assessment of all patients during their stay in the ICU using a portable slit lamp, development of a protocol and conducting further study to see the effect of protocolised eye care on developing EK. All of the eye assessments were carried out by one investigator who was fully trained in using a portable slit lamp and recognising eye signs, thus removing interobserver variability. We demonstrated that when a protocol is developed with the involvement of the nursing staff and incorporated into the patient electronic record, excellent adherence and prevention of EK can be achieved. However, the Hawthorne effect of awareness of the study being conducted by the health workers is likely to improve eye care in the first phase and the adherence to the protocol in the second phase of the study.

We did not investigate the long-term visual benefits of preventing EK in the ICU in this study. The study excluded paediatric patients and patients with specialist needs such as those with burns. We did not collect data on the indication for ICU admission or on factors such as use of neuromuscular blocking drugs, fluid balance or renal replacement therapy, so cannot comment on any potential influence of these factors in the development of EK. Although a power calculation was not performed to ascertain the sample size, the results demonstrate that type I or type II error is unlikely to have occurred.

We conclude that EK is common, but preventable, in critically ill patients. Mechanical ventilation and incomplete eye closure are the major risk factors for development of EK. A simple eye care protocol substantially reduces the incidence of EK, which can be easily achieved in clinical practice when a multidisciplinary focused approach is taken.