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Painless Red Eye

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This article discusses possible underlying causes of a painless red eye, including subconjunctival haemorrhage, episcleritis, conjunctivitis and blepharitis.

The presence of significant ocular pain and/or changes in visual acuity are red flags for more serious diagnoses, which will be discussed in a separate article.

Check out our article discussing the causes of a painful red eye here.

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Subconjunctival Haemorrhage

History and Examination

Subconjunctival haemorrhage is a common presentation and patients are often concerned because of its striking appearance. Subconjunctival haemorrhage is usually asymptomatic, though it can be slightly irritating and produce a gritty feeling in some cases.Β  Conjunctival haemorrhages can be small and discrete or diffuse.


Subconjunctival haemorrhages can be precipitated by trauma, suddenly rising intrathoracic pressure (such as lifting heavy weights) or rubbing of the eye.

Risk factors include hypertension and anticoagulants/antiplatelets. The development of subconjunctival haemorrhage can, therefore, be an indicator of underlying issues such as uncontrolled hypertension or deranged coagulation (e.g. raised INR).


No management is typically required unless caused by another factor (e.g. Warfarin may need to be reversed if INR is dangerously raised). Lubricants can provide symptomatic relief if the eye feels gritty, however often they are not required.

Patients should be given advice that the subconjunctival haemorrhage will resolve over a few weeks (typically fading from a deep red to a faint yellow before fully resolving).

If the patient has developed a subconjunctival haemorrhage secondary to trauma, you should consider the possibility of a foreign body in the eye. Typically, foreign bodies in the eye cause pain, watering and reduced visual acuity. Subconjunctival haemorrhage in the context of trauma may be secondary to occult rupture of the globe.

Subconjunctival haemorrhages
Discrete subconjunctival haemorrhages – note the yellow resolving segment on lower image. 1


History and Examination

In contrast to subconjunctival haemorrhage, episcleritis is typically more uncomfortable, but not frankly painful. On examination, you’ll find a sectoral area of hyperaemia, with obvious red dilated superficial vessels (commonly referred to as subconjunctival injection).

The subconjunctival injection in episcleritis is superficial and, as a result, moveable with a swab (and topical anaesthesia) pressed gently on the conjunctiva. The subconjunctival injection of episcleritis also blanches with phenylephrine application (a vasoconstrictor).

The important differential diagnosis to rule out is scleritis, which does not obey the rules above (e.g. doesn’t move with a swab or blanch with adrenaline). It is usually frankly painful and features dull pink areas of underlying inflammation.


Usually, there are no obvious precipitants for episcleritis, though symptoms tend to recur and the disease is associated with some systemic autoimmune conditions (30% of cases) such as ulcerative colitis.


There is no specific treatment and the condition is self-limiting, with simple analgesia and topical lubricants used to manage symptoms. Occasionally, steroids or oral/topical NSAIDs may be required.

Episcleritis: Sectoral, angry looking superficial vessels. No deeper pinkish tinge (as seen in scleritis). These areas of redness would move with a swab, and blanch with topical vasoconstrictors. 2


Conjunctivitis involves inflammation of the conjunctiva over the sclera (bulbar) and inner eyelids (tarsal). It forms a syndrome with varying causes and slightly differing presentations. Most cases are bilateral to some extent, due either to symmetrical pathologies (allergy, eye drop toxicity and other chemical exposure) or cross-infection from one eye to the other.

Common features

  • General discomfort, watering, grittiness, with variable amounts of discharge
  • It is typical for the eyelids to be crusted shut in the morning – not aetiologically specific
  • Diffuse conjunctival injection, possibly with swollen conjunctiva (chemosis) and debris
  • The majority of cases can be diagnosed on clinical features however swabs are helpful for diagnosis if symptoms persist or chlamydial/gonococcal disease is suspected
Mild conjunctivitis
Viral conjunctivitis: Diffuse relatively mild injection, not clearly circumlimbal, with a clear cornea. 3

Features of different aetiologies

Viral Conjunctivitis

  • Adenovirus and other common viruses
  • Extremely contagious (wash your hands thoroughly)
  • Eye-watering, coryzal symptoms and pre-auricular lymphadenopathy
  • May result in corneal inflammation and build-up of debris
  • Management is conservative (lubricants and cool compresses can provide symptomatic relief)
  • Antibiotics are unhelpful
  • Advise that symptoms may take weeks to resolve and that the patient should wash their hands regularly and not share towels with others

Bacterial Conjunctivitis

  • Less common than viral conjunctivitis
  • Same pathogens as respiratory infections (Pneumococcus, Staphylococcus or Haemophilus most commonly)
  • Often has more extensive conjunctival injection and discharge compared to viral conjunctivitis
  • Management involves the application of topical chloramphenicol drops/ointment or fusidic acid

Chlamydial Conjunctivitis

  • Relatively difficult to differentiate – suspect in younger age groups with risk factors
  • Typically persistent one-eyed conjunctivitis with serous discharge
  • Diagnosed by rough swabbing (you need infected cells) and PCR
  • Requires systemic antibiotic treatment as for genital chlamydial infections
  • Refer to a genitourinary medicine service for evaluation of genital disease and contact tracing
  • May cause significant scarring if untreated and reinfection is common

Gonorrhoeal Conjunctivitis

  • Again, suspect in younger age groups with risk factors
  • Severe swelling and hyper-purulent discharge, which may look like pre-septal cellulitis
  • Refer to a genitourinary medicine service for evaluation of genital disease and contact tracing
  • Treat systemically with antibiotics
  • Sequelae can be very significant – gonorrhoea can cause corneal ulceration and scarring

Allergic Conjunctivitis

  • Common, especially in individuals with a history of atopy
  • Occurs when exposed to the allergen (e.g. worse when outside if pollen related)
  • Typical conjunctivitis symptoms including itchy eyes, swelling of the eyelids/conjunctiva (chemosis) and associated coryzal symptoms
  • There are variants which can occur year-round with unclear precipitants
  • Management includes cold compresses and oral antihistamines for mild cases
  • Face washing after exposure to allergens is also helpful (e.g. for those with hayfever who have been outside)
  • Topical antihistamines, steroids and mast-cell stabilisers are used for more severe cases
Allergic conjunctivitis with chemosis
Allergic conjunctivitis: Diffusely mild injection. Mild eye puffiness and considerable chemosis. 4

Dry Eye

Dry eye’ is a syndrome of bilateral ocular irritation that is worsened with exposure (e.g. being outside in the wind, wearing contact lenses, blepharitis extended screen time).


There are varied causes based on deficiencies in different aspects of the tear film:

  • Evaporative – most common cause is blepharitis (obstruction of meibomian glands)
  • Tear deficiency – Sjogren’s syndrome (involves damage to the aqueous secreting lacrimal glands)


Inflammation of the eyelid margins results in obstruction of grease glands (meibomian glands) which leads to ineffective tears that evaporate easily. This causes the eye to β€˜water’ as a response – hence the typical symptoms of excessive watering, irritation and grittiness.

Signs on clinical examination

Blepharitis can be seen as irritated margins with β€˜capping’ (little globules), crusting and matted eyelashes.

You may also see chalazions, which appear as lumps on the eyelid resulting from the accumulation of secretions in the tarsal glands. Chalazions often resolve spontaneously but in some cases, incision and drainage of the gland may be required. Chalazions can become infected, requiring antibiotic treatment.


Management options for blepharitis include:

  • Good lid hygiene and warm compresses with lid massage (to help clear debris build up)
  • Ocular lubricants (thin preparations through the day, and thicker ointments before bed)
  • In severe cases of blepharitis, occlusion of the puncta is used to reduce tear drainage and improve overall ocular lubrication.
Blepharitis, with lots of crusting. 5


  • A painless red eye, without visual disturbance, is unlikely to have a sinister underlying cause.
  • Concerning features of a red eye include pain and reduce visual acuity.
  • Common causes of a painless red eye include subconjunctival haemorrhage, episcleritis, conjunctivitis and blepharitis.
  • A thorough history and clinical assessment should enable you to rule out concerning features and narrow the differential diagnosis.


1. Therealbs2002 [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]

2. Asagan [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]

3. Marco Mayer [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]

4. James Heilman, MD [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]

5. Imrankabirhossain [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]


Fiona Kirkham


Reviewed by

Dr Ashley Simpson

Ophthalmology Registrar

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