Changes

March 2026 — reviewed. A literature search was conducted in February 2026 to identify evidence-based guidelines, UK policy, systematic reviews, and key randomized controlled trials published since the last revision of this topic. No change to clinical recommendations has been made.

Update

Goals

To support primary healthcare professionals to:

• Make a working diagnosis of the cause of red eye.
• Identify people with red eye who require referral for specialist assessment.
• Manage people whose cause of red eye can be safely treated in primary care.

Outcome measures

No outcome measures were found during the review of this topic.

Audit criteria

No audit criteria were found during the review of this topic.

QOF indicators

No QOF indicators were found during the review of this topic.

QIPP - options for local implementation

No QIPP indicators were found during the review of this topic.

NICE quality standards

No NICE quality standards were found during the review of this topic.

What can cause it?

• Red eye is a common ophthalmic presentation in primary care. Most cases are benign and self-limiting, but it may sometimes indicate a serious or sight-threatening condition, so careful assessment is essential.
• Serious and potentially sight-threatening causes of red eye include:
  • Acute glaucoma — for more information, see the CKS topic on Glaucoma.
  • Anterior uveitis — for more information, see the CKS topic on Uveitis.
  • Corneal causes — these include corneal ulcer (bacterial, viral, or fungal), contact lens-related red eye, and corneal foreign body. For more information, see the CKS topics on Corneal superficial injury and Herpes simplex - ocular.
  • Ophthalmia neonatorum (also known as neonatal conjunctivitis) — conjunctivitis occurring within the first 28 days of life. The infection can be bacterial (including chlamydial, which is the most common pathogen) or viral in origin, and is usually acquired during passage through an infected birth canal. For further information, see the CKS topic on Conjunctivitis - infective.
  • Trauma — such as penetrating eye injury or high-velocity foreign body. 
  • Chemical injuries — these can cause lasting problems with the ocular surface. Alkali solutions can be very harmful.
  • Scleritis — inflammation of the sclera (the white outer wall of the eye), which is characterized by severe pain. It can be associated with connective tissue disorders, such as rheumatoid arthritis and systemic lupus erythematosus.
  • Endophthalmitis — this is normally a post-operative infection that occurs within the first 2 weeks of surgery and can rapidly cause blindness. There is history of recent surgery with signs and symptoms including markedly reduced vision, significant pain/headache, and hypopyon.
• Other causes of red eye include:
  • Conjunctivitis — for more information, see the CKS topics on Conjunctivitis - allergic and Conjunctivitis - infective.
  • Sub-conjunctival haemorrhage — this is due to a bleed into the subconjunctival space. There may or may not be a history of a contributory factor, such as straining with coughing or constipation. It may be associated with hypertension.
  • Subtarsal or conjunctival foreign body — for more information, see the CKS topic on Corneal superficial injury.
  • Corneal abrasion — for more information, see the CKS topic on Corneal superficial injury.
  • Episcleritis — this presents with redness, lacrimation, and photophobia and is generally painless. On examination, there is segmental redness, with normal vision, pupil reactions, and no corneal staining. 
  • Adnexal causes, such as:
    • Dry eye — for more information, see the CKS topic on Dry eye syndrome.
    • Blepharitis — for more information, see the CKS topic on Blepharitis.
    • Ectropion (outward rotation of the eyelid margin).
    • Entropion (inward rotation of the eyelid margin).
    • Trichiasis (misdirection of the eyelashes towards the cornea).
• Child maltreatment — although rare, suspect child maltreatment if a child has retinal haemorrhages, or an eye injury without a major confirmed accidental cause or known medical explanation (including birth-related causes). For more information, see the CKS topic on Child maltreatment - recognition and management.

[Pflipsen, 2016; Tarff, 2017; Lansingh, 2018; Bristol Eye Hospital, 2020; Lu, 2020; Bonini, 2021; College of Optometrists, 2024]

How should I assess a person with a red eye?

Assessment of a person with red eye involves taking a history and performing an examination to help identify the underlying cause and any red flags for a serious condition.

• Take a history. Ask about:
  • Symptoms, including:
    • Onset and duration.
    • Whether symptoms are unilateral or bilateral (and if bilateral, whether onset was simultaneous).
    • Visual changes. 
    • Pain and severity.
    • Foreign body sensation. 
    • Discharge, itch, or photophobia. 
    • Any other associated symptoms, such as headache. 
  • Risk factors, such as contact lens use (which increases the risk of microbial keratitis), and history of trauma.
  • Previous ocular history.
  • Other past medical history, including recent illness, relevant systemic conditions, medications, and allergies. 
  • Family history of eye disease or other relevant conditions. 
• Perform an examination of both eyes. If perforation of the globe is suspected (for example, following ocular trauma or as a complication of scleritis), do not palpate the eye — arrange urgent ophthalmology assessment. 
  • Assess visual function.
    • Check visual acuity using a Snellen chart (or an age-appropriate method in children).
  • Inspect the face and eyelids: 
    • Look for evidence of facial trauma.
    • Check for discharge.
    • Examine the eyelids for swelling, trichiasis, entropion, or ectropion.
  • Examine the conjunctiva and cornea:
    •  Inspect the conjunctiva, including the tarsal surface; if a foreign body is suspected, evert the upper lid to check for a subtarsal foreign body.
    • Assess the pattern of redness — ciliary flush (injection of limbal vessels where the cornea meets the sclera) may indicate more serious causes, such as anterior uveitis or corneal disease.
    • Inspect the cornea for foreign body, opacity, haze, or ulceration.
    • Perform fluorescein staining — corneal staining may indicate a corneal abrasion or ulcer.
  • Inspect the anterior chamber.
    • Look for visible abnormalities, such as a hypopyon (pus in the anterior chamber).
  • Assess the pupils:
    • Observe in dim light and check for equal size and shape.
    • Check for photophobia.
    • Assess direct and consensual light reflexes.
    • Check for a relative afferent pupillary defect (RAPD) using the swinging flashlight test.
  • Measure blood pressure if subconjunctival haemorrhage is suspected.
• Document the history and findings of eye examinations (including negative findings). This is particularly important when management of a unilateral red eye is going to take place in primary care.
• Suspect child maltreatment if a child has retinal haemorrhages, or an eye injury without a major confirmed accidental cause or known medical explanation (including birth-related causes). For more information, see the CKS topic on Child maltreatment - recognition and management.

Scenario: Management of red eye

From birth onwards.

Search strategy

Scope of search

A literature search was conducted for guidelines, systematic reviews and randomized controlled trials on primary care management of red eye.

Search dates

May 2021 - February 2026

Key Search Terms

Various combinations of searches were carried out. The terms listed below are the core search terms that were used for Medline.

• exp eye diseases/
• *Acute
• Non acute
• *Anexa
• *Conjunctivital
• *Corneal
• occular inflammation.ti,ab.

Sources of guidelines

• National Institute for Health and Care Excellence (NICE)
• Scottish Intercollegiate Guidelines Network (SIGN)
• Royal College of Physicians
• Royal College of General Practitioners
• Royal College of Nursing
• NICE Evidence
• World Health Organization
• Guidelines International Network
• TRIP database
• Agency for Healthcare Research and Quality
• National Health and Medical Research Council (Australia)
• Royal Australian College of General Practitioners
• British Columbia Medical Association
• Canadian Medical Association
• Alberta Medical Association
• Michigan Quality Improvement Consortium
• Singapore Ministry of Health
• National Resource for Infection Control
• RefHELP NHS Lothian Referral Guidelines
• Medline (with guideline filter)
• Driver and Vehicle Licensing Agency
• NHS Health at Work (occupational health practice)

Sources of systematic reviews and meta-analyses

• The Cochrane Library:
  • Systematic reviews
  • Protocols
  • Database of Abstracts of Reviews of Effects
• Medline (with systematic review filter)
• EMBASE (with systematic review filter)

Sources of health technology assessments and economic appraisals

• NIHR Health Technology Assessment programme
• The Cochrane Library:
  • NHS Economic Evaluations
  • Health Technology Assessments
• Canadian Agency for Drugs and Technologies in Health
• International Network of Agencies for Health Technology Assessment

Sources of randomized controlled trials

• The Cochrane Library:
  • Central Register of Controlled Trials
• Medline (with randomized controlled trial filter)
• EMBASE (with randomized controlled trial filter)

Sources of evidence based reviews and evidence summaries

• Drug and Therapeutics Bulletin
• TRIP database
• Central Services Agency COMPASS Therapeutic Notes

Sources of national policy

• Department of Health
• Health Management Information Consortium (HMIC)

Patient experiences

• Healthtalk
• BMJ - Patient Journeys

Sources of medicines information

The following sources are used by CKS pharmacists and are not necessarily searched by CKS information specialists for all topics. Some of these resources are not freely available and require subscriptions to access content.

• British National Formulary (BNF)
• electronic Medicines Compendium (eMC)
• European Medicines Agency (EMEA)
• Medicines and Healthcare products Regulatory Agency (MHRA)
• REPROTOX
• Scottish Medicines Consortium
• Stockley's Drug Interactions
• TERIS
• TOXBASE
• Micromedex
• UK Medicines Information

Stakeholder engagement

Our policy

The external review process is an essential part of CKS topic development. Consultation with a wide range of stakeholders provides quality assurance of the topic in terms of:

• Clinical accuracy.
• Consistency with other providers of clinical knowledge for primary care.
• Accuracy of implementation of national guidance (in particular NICE guidelines).
• Usability.

Principles of the consultation process

• The process is inclusive and any individual may participate.
• To participate, an individual must declare whether they have any competing interests or not. If they do not declare whether or not they have competing interests, their comments will not be considered.
• Comments received after the deadline will be considered, but they may not be acted upon before the clinical topic is issued onto the website.
• Comments are accepted in any format that is convenient to the reviewer, although an electronic format is encouraged.
• External reviewers are not paid for commenting on the draft topics.
• Discussion with an individual or an organization about the CKS response to their comments is only undertaken in exceptional circumstances (at the discretion of the Clinical Editor or Editorial Steering Group).
• All reviewers are thanked and offered a letter acknowledging their contribution for the purposes of appraisal/revalidation.
• All reviewers are invited to be acknowledged on the website. All reviewers are given the opportunity to feedback about the external review process, enabling improvements to be made where appropriate.

Stakeholders

• Key stakeholders identified by the CKS team are invited to comment on draft CKS topics. Individuals and organizations can also register an interest to feedback on a specific topic, or topics in a particular clinical area, through the Getting involved section of the Clarity Informatics website.
• Stakeholders identified from the following groups are invited to review draft topics:
  • Experts in the topic area.
  • Professional organizations and societies (for example, Royal Colleges).
  • Patient organizations, Clarity has established close links with groups such as Age UK and the Alzheimer’s Society specifically for their input into new topic development, review of current topic content and advice on relevant areas of expert knowledge.
  • Guideline development groups where the topic is an implementation of a guideline.
  • The British National Formulary team.
  • The editorial team that develop MeReC Publications.
• Reviewers are provided with clear instructions about what to review, what comments are particularly helpful, how to submit comments, and declaring interests.

Patient engagement

Clarity Informatics has enlisted the support and involvement of patients and lay persons at all stages in the process of creating the content which include:

• Topic selection
• Scoping of topic
• Selection of clinical scenarios
• First draft internal review
• Second draft internal review
• External review
• Final draft and pre-publication

Our lay and patient involvement includes membership on the editorial steering group, contacting expert patient groups, organizations and individuals.

Evidence exclusion criteria

Our policy

Scoping a literature search, and reviewing the evidence for CKS is a methodical and systematic process that is carried out by the lead clinical author for each topic. Relevant evidence is gathered in order that the clinical author can make fully informed decisions and recommendations. It is important to note that some evidence may be excluded for a variety of reasons. These reasons may be applied across all CKS topics or may be specific to a given topic.

Studies identified during literature searches are reviewed to identify the most appropriate information to author a CKS topic, ensuring any recommendations are based on the best evidence. We use the principles of the GRADE and PICOT approaches to assess the quality of published research. We use the principles of AGREE II to assess the quality of published guidelines.

Standard exclusions for scoping literature:

• Animal studies
• Original research is not written in English

Possible exclusions for reviewed literature:

• Sample size too small or study underpowered
• Bias evident or promotional literature
• Population not relevant
• Intervention/treatment not relevant
• Outcomes not relevant
• Outcomes have no clear evidence of clinical effectiveness
• Setting not relevant
• Not relevant to UK
• Incorrect study type
• Review article
• Duplicate reference

Organizational, behavioural and financial barriers

Our policy

The CKS literature searches take into consideration the following concepts, which are discussed at the initial scoping of the topic.

• Feasibility
  • Studies are selected depending on whether the intervention under investigation is available in the NHS and can be practically and safely undertaken in primary care.
• Organizational and Financial Impact Analysis
• Studies are selected and evaluated on whether the intervention under investigations may have an impact on local clinical service provision or national impact on cost for the NHS. The principles of clinical budget impact analysis are adhered to, evaluated and recorded by the author. The following factors are considered when making this assessment and analysis.
  • Eligible population
  • Current interventions
  • Likely uptake of new intervention or recommendation
  • Cost of the current or new intervention mix
  • Impact on other costs
  • Condition-related costs
  • In-direct costs and service impacts
  • Time dependencies
• Cost-effectiveness or cost-benefit analysis studies are identified where available. 

We also evaluate and include evidence from NICE accredited sources which provide economic evaluations of recommendations, such as NICE guidelines. When a recommended action may not be possible because of resource constraints, this is explicitly indicated to healthcare professionals by the wording of the CKS recommendation.

Declarations of interest

Our policy

Clarity Informatics requests that all those involved in the writing and reviewing of topics, and those involved in the external review process to declare any competing interests. Signed copies are securely held by Clarity Informatics and are available on request with the permission of the individual. A copy of the declaration of interest form which participants are asked to complete annually is also available on request. A brief outline of the declarations of interest policy is described here and full details of the policy is available on the Clarity Informatics website. Declarations of interests of the authors are not routinely published, however competing interests of all those involved in the topic update or development are listed below. Competing interests include:

• Personal financial interests
• Personal family interest
• Personal non-financial interest
• Non-personal financial gain or benefit

Although particular attention is given to interests that could result in financial gains or losses for the individual, competing interests may also arise from academic competition or for political, personal, religious, and reputational reasons. An individual is not obliged to seek out knowledge of work done for, or on behalf of, the healthcare industry within the departments for which they are responsible if they would not normally expect to be informed.

Who should declare competing interests?

Any individual (or organization) involved in developing, reviewing, or commenting on clinical content, particularly the recommendations should declare competing interests. This includes the authoring team members, expert advisers, external reviewers of draft topics, individuals providing feedback on published topics, and Editorial Steering Group members. Declarations of interest are completed annually for authoring team and editorial steering group members, and are completed at the start of the topic update and development process for external stakeholders.

Competing interests declared for this topic:

None.