BACKGROUND

Coronavirus disease 2019 (COVID-19) emerged in China at the end of 2019 and has since rapidly spread worldwide. It primarily impacts the respiratory system, which can lead to acute respiratory distress syndrome (ARDS) with subsequent multi-organ involvement and critical care support.¹ Current data reports that patients with co-morbidities (older age, chronic respiratory disease, cardiovascular disease, diabetes mellitus, obesity and immunocompromised states) are at higher risk of COVID-19-associated complications, Intensive Care Unit (ICU) admissions and fatalities. The strain on the healthcare system in the UK has led to drastic restructuring and reallocation of resources to help cope with the growing demand.

To better manage the pandemic, elective surgery and outpatient services were cancelled to help increase capacity. Doctors and nurses within sub-specialities like Ophthalmology have been supporting medical and critical care services while continuing to see and treat Ophthalmic emergencies. The demand for internal reviews has increased, in particular from ICU especially for proned patients. ARDS patients are regularly proned to aid their respiratory rehabilitation whilst they are ventilated, and this positional change helps reduce pleural pressure and restore oxygenation to lung segments.² Furthermore, patients are unable to communicate changes in their vision or new onset of pain that may suggest evolving pathologies. This poses additional difficulties for ICU staff who are already inundated to recognise and appropriately escalate for specialist input. This article highlights common ophthalmic conditions and their management during this challenging period.

LAGOPHTHALMOS AND EXPOSURE KERATOPATHY

A common ophthalmic complication from ventilated patients is lagophthalmos. Intubated patients are sedated and paralysed which prevents the orbicularis oculi muscle from closing the lid. This impairment of eye closure together with loss of the Bells reflex results in corneal surface exposure and subsequent drying can lead to corneal epithelium breakdown. Intervention for lagophthalmos can be determined by the extent of the exposed cornea and regular lubrication and horizontal taping of the eyelid would be the most appropriate initial course of action.³ This can be easily taught to ICU staff and in the event of more significant lagophthalmos, medical therapy to induce a ptosis with botulinum toxin injections or a surgical tarsorrhaphy can be considered.

CONJUNCTIVITIS AND MICROBIAL KERATITIS

ICU patients are exposed to numerous sources of infections, whether it is from commensal bacteria, respiratory aerosols or contact from suction catheters.³ Commonly grown bacteria in ICU patients have been Staphylococcus Epidermis and Pseudomonas Aeruginosa.⁴ Attending staff must be vigilant in noting conjunctival injection, mucopurulent discharge and corneal opacification. Conjunctivitis requires a swab for microbial culture, regular ocular cleaning and topical antibiotics as per local microbiology guidelines.³

Microbial keratitis will need to be reviewed by the Ophthalmologist and the size of the infiltrate along with the anterior chamber activity accurately recorded. Microbial keratitis will need to be treated with an intensive course of hourly fourth generation fluoroquinolone antibiotics, or in accordance to local microbiology guidelines, for 48 hours at which point the patient should be reassessed.

CHEMOSIS, PROPTOSIS AND ORBITAL CONGESTION

COVID-19 patients are at risk of orbital congestion due to hydrostatic pressure from the gravitational changes during proning, positive-pressure from the ventilators and the increased capillary leakage from their pro-inflammatory states.^1,3 The majority of patients will find their chemosis settles with conservative management once the patient is supine however, the Ophthalmologist will have to be aware of the rare orbital compartment syndrome. This irreversible sight loss complication has previously been reported in spinal surgery patients who are placed in the prone position for a prolonged period of time.⁵ Assessment of the eye is vital in determining the need for urgent intervention and this involves digital palpation of the globe to assess for a tense orbit and measuring intraocular pressure if possible. A relative afferent pupillary defect (RAPD) with a notable proptosis and tense orbit will be suggestive of compressive optic neuropathy where an urgent bedside cantholysis may be indicated.

PUPILLARY ABNORMALITIES

Relative afferent pupillary defects (RAPD) indicate a defect in the retinal ganglion nerve pathway to the optic nerve or the subsequent optic nerve pathway towards the midbrain. This can be assessed by the swinging light test, where the impacted eye fails to constrict upon exposure to the torchlight. The commonest cause of RAPD is due to optic nerve pathology from ischaemia, inflammation or compression. However, the Ophthalmologist should also examine the patient’s retina for ischaemia, infection (CMV) or haemorrhagic causes. Although ophthalmic intervention for some of these conditions will be difficult in the ICU department, the diagnostic confirmation could help with systemic treatment and visual prognosis.

COVID-19 patients are highly susceptible to coagulation disorders, with numerous cases of pulmonary emboli being reported.¹ Pupillary abnormalities can be a presenting sign for retinal vascular occlusions or cavernous sinus thrombosis and identifying this can indicate further investigations and treatment.

OPTIC NEUROPATHY

The anterior and posterior portions of the optic nerve are supplied by the ciliary and plial arteries, respectively. This network of short arteries can come under insult in critically unwell patients. ICU patients often have evidence of global hypoperfusion, or a systemic inflammatory response syndrome, are on high ventilatory support or required cardiopulmonary resuscitation and as a consequence have a higher incidence of anterior ischaemic optic neuropathy.⁶ Since most COVID-19 patients are transferred to ICU for ventilation and inotropic support, a combination of these factors along with regular proning increases the likelihood of optic nerve hypoperfusion and subsequent neuropathy.⁶ Referral to Ophthalmology should be considered for a dilated fundal exam in any patient who may show signs of RAPD.

ENDOPHTHALMITIS

Endogenous endophthalmitis remains a risk for COVID-19 patients due to intravascular catheters, parenteral nutrition, dialysis and the use of broad-spectrum antibiotics.⁷ Candida albicans and bacterium like Pseudomonas impose the biggest risk to endogenous endophthalmitis.⁷ ICU staff may find it difficult to recognise this in sedated patients unless there is a notable hypopyon; thus, a dilated fundal examination will be required once there are positive blood cultures and the patient will need to be initiated on systemic antifungals or antibacterial. Moreover, chorioretinal lesions with vitreous activity may warrant intravitreal antifungal or antibacterial treatment in accordance to local microbiology protocol. The lesions can be isolated or disseminated across the retina and the ophthalmologist will need to be aware that the view may not be clear due to an inflamed vitreous as well as poor ocular surface coupled with poor dilation of patients on opioids.

CONCLUSION

This article highlights the importance of a thorough ocular assessment in COVID-19 ICU patients. The majority of patients in ICU will be sedated and will be unable to communicate changes in vision. ICU staff will play an important role in maintaining good eye care while being vigilant in identifying patients with evolving signs for further assessment. The ophthalmologist will have to be alert and not miss an array of conditions that have been described due to the complex pathophysiology and developing understanding of COVID-19 as well as a demanding clinical environment. It is evident that the Ophthalmology team will play an important role in the management and rehabilitation of patients who have been in ICU due to COVID-19.