Eye care - background

Anatomy and Physiology

Ocular surface protective mechanisms

The ocular surface is protected from injury and infection by a number of structures (refer to Figure 1) including:

  1. retractable eyelids, which have a mucous membrane covering that is continuous with the eyeball, and epithelium of the sclera, cornea and conjunctiva. Eyelids mechanically protect the eyes from dehydration and injury (1).
  2. an opaque sclera, which ensures that light transmitted to the globe enters only through the transparent corneal covering of the pupil (1).
  3. an avascular cornea, which functions to admit and refract light. If injured, it may be slow to heal. Five layers of corneal tissue (superficially epithelium changing to deeper endothelial tissue) provide a protective barrier against abrasion and erosion, and also provide a permeability barrier against eye pathogens (2), and
  4. conjunctival epithelium, which extends from the eyelid margins anteriorly, sharply turning on itself to cover the sclera, creating a moist sac. This sac is continuous with the epithelium lining the ducts of tear producing glands, and plays a central role in the defence of ocular surface microbial injury (2). The conjunctiva has a rich blood supply. If damaged, redness and swelling may be present. Tissues may protrude between the eyelids, exacerbating the effects of lagopthalmos, and resulting in corneal opacity and vision loss (2).

Proper functioning of the above structures, and transparency of the cornea are therefore essential requirements for eye surface protection and vital for vision (2, 3).

Under normal physiology, closure of the eyelids occurs, and is protective of the ocular surface, blink reflex and tear production are present, and the sclera and cornea appear bright and clear (1).

 Horizontal section of a schematic eye
Figure 1 Horizontal section of a schematic eye. Image from Eye Emergency Manual (4).

Function of tears and blinking mechanism

Complex physiology underlies the action of eyelid closure and blinking. These two actions provide a mechanical barrier to ocular injury, and prevent drying out and desiccation of the corneal epithelium by distributing tear film across the exposed surface of the eye (3, 5, 6). Lacrimal gland production of tear film is inherent to healthy eye function (2). Tear film contains bactericidal enzymes (lysozyme, lactoferrin), and proteins (IgA). Tears help to provide a defence against microbial colonisation by providing a medium for transport of leucocytes in the event of eye injury or infection (1). Any increase in irritation from the cornea or conjunctiva will trigger a lacrimal reflex, resulting in an increased tear volume for the eye (2). Blinking and tear production also aids in smoothing out corneal irregularities, protects the air-corneal interface and refractive surface of the cornea. It also supports the clearance of metabolic waste via nasolacrimal drainage mechanisms and enables oxygen delivery to the cells of an avascular cornea (1).

Abnormal physiology

Any disruption to ocular epithelial tissue may compromise vision and predispose the cornea to infection and OSD (3, 7). Mechanisms underlying the development of conditions such as corneal abrasion, erosion, or pathogenic invasion primarily relate to lack of eyelid closure and interruption to blinking reflex and blinking frequency (2, 3, 5). In the ICU population the use of muscle relaxants and sedation have been identified as contributing to lagopthalmos and of placing patients at increased risk (5, 8, 9).

Epidemiology of ocular complications in the critically ill adult

Iatrogenic eye complications cover a range of OSD involving structures such as the cornea, sclera and conjunctiva. Pathologies may range from microepithelial corneal punctures (often associated with dry eye syndrome), to corneal abrasion, erosion, ulceration, infection and scarring (6). Superficial keratopathy, that is, any breach of the ocular surface (3, 8, 10) ), in the ICU population, has been found to predispose to infection of the corneal epithelium (keratitis) (1, 8, 11). This infection may present as microbial, bacterial or fungal in origin (3, 5, 12). Keratitis in the presence of corneal exposure has been found to be a key factor in the development of ocular surface disease (1, 8, 12-14) and has resulted in serious complications such as vision loss, corneal rupture, and the need for corneal transplantation (3, 8, 15-17).

A high incidence of OSD among ICU patients has been reported with a range from 23%-60% of patients affected. Of these, exposure keratopathy has been found in 23%-40% (11, 13). Superficial keratopathy has been found in 60% of patients sedated or on neuromuscular blockade (8). Microbial keratitis has been found to be more prevalent than the non-ulcerative sterile form of keratitis (77% vs. 10%) (9). (See Table 1)

Table 1: Opthalmology abnormalities

dry eye
Dry eye

dry eye
Dry eye


Corneal abrasion
Corneal abrasion

Allergic conjunctivitis
Allergic conjunctivitis

Marginal keratitis
Marginal keratitis

Viral conjunctivitis
Viral conjunctivitis

Bacterial ulcer
Bacterial ulcer

Bacterial conjunctivitis
Bacterial conjunctivitis

Red eye in septic patient
Red eye in septic patient

Why critically ill patients are at increased risk of ocular surface disorders

There are a number of causes of impaired ocular defence mechanisms in critically ill patients including:

  • an alteration in level of consciousness, impacting on the blink reflex and lagopthalmos
  • metabolic derangements
  • immunosuppression
  • mechanical ventilation
  • medications such as sedatives, muscle relaxants and paralysis
  • open suction technique, and
  • systemic disease (6, 13, 18, 19)

The ICU environment is also a pathogen-rich environment. This may contribute to the increased exposure of the ocular surface to microorganisms (15). Multi-resistant organisms associated with microbial keratitis include: pseudomonas aeruginosa, acinetobacter, staph epidermis, enterococcus, enterobacter, proteus mirabilis and klebsiella pneumonae (3, 15, 20). Regular eye care has been found to reduce the developmnet of corneal abnormalities and infections in ICU populations (12, 17, 21). Meticulous nursing care is therefore essential to prevent iatrogenic ophthalmological complications and potentially serious visual impairment (6, 22).

Eye care for the critically ill patient

Regular eye care for intubated and ventilated patients is considered routine nursing practice. Anecdotally however, it has been shown that practice varies greatly between intensive care units regarding the frequency and method of eye care undertaken. Historically, specific eye care practice has included regimens of cleaning the eyes with sterile water or normal saline every two to four hours (10, 17, 21, 23), twice daily (24) or daily (25). Installation of a lubricating liquid, such as methylcellulose eye drops, has also been commonly used (10, 17, 23, 24, 26). Eye ointment has been applied for high risk patients, or where evidence of eye injury may be apparent, such as when conjunctival oedema is present (13, 16, 19, 21, 23, 26-28). For conditions of conjunctival or corneal exposure, methods such as passive eye closure (27), eye taping (10, 13, 19, 23), padding with gel membranes (10, 13, 17, 28), and creation of moisture closed chambers using polyethylene film (13, 21, 23, 24, 26) or goggles (19) have been described (see Eye care methods identified in the literature). From the literature review it is unclear if any of three methods identified contributed to ocular surface protection, or to the maintenance of eyelid closure (27), as there has been a limited number of quality studies, and significant variability in the methods of eye care used in studies.

Eye care methods identified in the literature


Eye care method

Bates J et al. Clinical Intensive Care 2004 (13)

Routine eye care to all patients daily: cleaning lids with saline and sterile gauze daily, plus ocular lubricant at least twice daily. Corneal Care with adhesive to tape the eyelids closed. Geliperm/Polyacrylamide Gel Membrane Changed at regular intervals to prevent drying.

Cortese D et al. American Journal of Critical Care 1995 (17)

All patients eye toilet with n/s 2/24 Polyethylene Cover (PC) over the eyes to create a moisture chamber. Changed daily. Methylcellulose (hypromellose) lubricating drops 2/24.

Ezra D et al. Intensive Care Medicine 2009 (28)

Lacrilube applied to inferior conjunctival fornix 6/24.

Geliperm dressing cut to completely cover the top and lower lid and applied onto the closed eye 4/24 or sooner if signs of drying.

Staff trained in eye care, particularly in early recognition of drying Geliperm.

Guler E et al. Journal of Clinical Nursing 2010 (24)

For all subjects, standard eye care with sterile n/s soaked gauze conducted twice daily. Then Polyethylene cover applied to one eye every 12/24, and Carbomer Methylcellulose drops 6/24 to the other eye.

Joyce N Joanna Briggs Institute (Systematic Review) 2002 (26)

Polyethylene Cover used. Hypromellose eye drops two drops 2/24 combined with 1–1.27cm Duratears ointment 4/24.

Koroloff N et al. Intensive Care Medicine 2004 (23)

Standard care for both groups: 2/24 eye cleaning with n/s.

Lacri-lube ointment 2/24 plus 2/24 Hypromellose drops combination.

Polyethylene Cover/cling wrap placed over the eyes to create a moisture chamber. Micropore used to seal the edge. Changed every shift, or when necessary.

Laight S et al. Intensive and Critical Care Nursing 1996 (10)

Sterile water used for eye cleaning 2/24 for all patients. Hypromellose drops 1/24 – 6/24 with corneal dryness. Micropore used for mechanical eye closure. Gel membrane/Geliperm covers applied on clean eye only, and assessed 2/24 for dryness and change.

Lenart S, Garrity J American Journal of Critical Care 2000 (27)

1.27cm Duratears artificial tear ointment 4/24.passive eyelid closure.

Rosenberg J et al. Critical Care Medicine 2008 (29)

Moisture chamber (MC); lubricating ointment.

Sivasankar S et al. Indian Journal of Critical Care Medicine 2006 (19)

Closed moisture chamber created using swimming goggles and sterile water moistened gauze 12/24.

Open chamber method (ocular lubricant and mechanical eye closure using securing tape 12/24).

So H International Journal of Nursing Studies 2008 (30)

All subjects received standard eye care: cleansing of the eyelids and surrounding skin 4/24 with n/s.

Lanolin/Durotears ointment: 1cm applied into the “V” pocket between the eyeball and lower lid of each eye 4/24.

Polyethylene cover/Gladwrap, tailored to cover the eyes from the eyebrow to the cheekbone, snuggly adhering to form a closed moisture chamber. Micropore adhesive tape use to secure edges of the wrap if the seal was not adequate. PC wrap changed daily, or when visibly soiled.


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The information on this page is general in nature and cannot reflect individual patient variation. It reflects Australian intensive care practice, which may differ from that in other countries. It is intended as a supplement to the more specific information provided by the doctors and nurses caring for your loved one. ICNSW attests to the accuracy of the information contained here but takes no responsibility for how it may apply to an individual patient. Please refer to the full disclaimer.