24 Hour Ophthalmic Emergencies Part 1 – Acute Red Eye

Author: William Spackman, Adam Booth / Editor: Liz Herrievan / Codes: / Published: 06/05/2025

Editors intro: This fab four-part blog has been written for us by an ophthalmology registrar. The aim is to highlight the eye conditions we ED folk should be aware of, particularly those we need to refer asap. Some of the slit-lamp examination findings described might elude some of us (me, at least) in many cases, but dont let that put you off! Ive also Googled some of the more unfamiliar terms so you dont have to.

Introduction

There are a limited number of true ophthalmic emergencies, but it is important for emergency clinicians to be aware of ophthalmic conditions where immediate action needs to be taken. In many of the conditions discussed in this blog, prompt recognition and management can be sight-preserving and, in certain cases, life-preserving. This blog aims to guide emergency clinicians in the assessment and management of some of the most important emergency ophthalmic presentations.

The Acute Red Eye

The acute red eye is one of the most common ophthalmic presentations and has a wide differential that includes everything from an innocuous conjunctivitis to immediately sight threatening conditions such as Acute Angle Closure Glaucoma or Endophthalmitis.

Acute Angle Closure Glaucoma

Acute Angle Closure Glaucoma (AACG) is an acute elevation in intraocular pressure secondary to closure of the anterior chamber drainage angle.1 AACG typically presents with significant and acute eye pain, headache, nausea, blurred vision and haloes.1

Examination findings of AACG include reduced visual acuity, conjunctival hyperaemia, corneal haze and a mid-dilated, unresponsive pupil. More detailed examination at the slit lamp may reveal cataract, a closed drainage angle and a significantly raised intraocular pressure (IOP).1

If AACG is suspected, immediate referral for specialist ophthalmic management is crucial. When the IOP is significantly elevated, irreversible optic nerve damage can take place very quickly. Management would usually include intravenous acetazolamide to suppress aqueous humour production, topical pilocarpine to constrict the pupil and open the drainage angle and topical treatment to lower the intraocular pressure such as apraclonidine, dorzolamide and timolol.2 In order to break the cycle of angle closure, a laser peripheral iridotomy is usually performed.2 Further treatment may include cataract surgery or cyclodiode laser.1

Endophthalmitis

Endophthalmitis is severe intraocular inflammation, usually secondary to exogenous or endogenous infection.3 Exogenous endophthalmitis is far more common and usually follows intraocular surgery or trauma.3 Endogenous endophthalmitis is rarer and usually results from severe systemic infection.3

Acute post-operative endophthalmitis typically presents within the first 2 weeks and usually between 3 and 5 days.4 Acute endophthalmitis typically presents with rapidly progressive pain, redness, photophobia, blurred vision and/or swollen lids.3,4

Examination findings include reduced visual acuity, lid swelling, conjunctival hyperaemia, corneal oedema and fibrin or hypopyon (pus) in the anterior chamber.4 Posterior segment examination may reveal vitreous inflammation but the fundal view may be severely impaired.3

Immediate ophthalmic assessment and management is indicated. This involves anterior chamber and vitreous tap, followed by intravitreal injection of antibiotics, typically Ceftazidime and Vancomycin.4 Early vitrectomy may be indicated if the vision is particularly poor.5

Fig.1 Acute anterior uveitis with ciliary flush (hyperaemia at the corneal limbus) – image via Shutterstock

Uveitis

Uveitis is inflammation of the uvea which is composed of the iris, ciliary body and the choroid.6 Uveitis may be associated with systemic disease including infectious, inflammatory and malignant causes.6

The most common presentation of uveitis is acute anterior uveitis. This typically presents with acute pain, redness, photosensitivity and blurred vision.7 Examination will reveal ciliary flush, keratic precipitates (white deposits on the cornea), anterior chamber cells and flare and posterior synechiae (adhesions).7 In more severe cases there may be hypopyon or fibrin in the anterior chamber.7 It is important in all cases of uveitis to examine the back of the eye to look for signs of intermediate or posterior uveitis which have greater potential to cause sight threatening disease and require a different workup and management plan.

Where uveitis is suspected, urgent ophthalmology review is indicated. Acute anterior uveitis is usually treated with topical steroid drops starting hourly and tapering over a period of weeks.6 This is combined with a cycloplegic in the early period to prevent posterior synechiae formation and reduce discomfort and inflammation.6

Microbial Keratitis

Microbial Keratitis is an infection of the cornea and may be caused by bacteria, viruses, fungi or amoeba.6 It presents acutely with a painful, red eye with photosensitivity and epiphora (watering).6 There may be a history of trauma, contact lens wear or herpetic disease.

In bacterial keratitis, a round white infiltrate is usually seen within the corneal stroma with an epithelial defect. A corneal scrape may be performed to ascertain the pathogen and establish sensitivities. Initial management is typically with intensive hourly broad spectrum topical antibiotics and close follow-up.8

Fungal keratitis presents similarly but presents with a fluffier edge to the infiltrate and may present less acutely.9 Corneal scrape is important to confirm diagnosis and guide management. This is typically with topical, intrastromal or systemic anti-fungals.9

Viral keratitis is most commonly caused by the herpes viruses herpes simplex and herpes zoster.10 Epithelial disease is typically characterised by a linear dendritic lesion with terminal bulbs.6 Stromal disease may be characterised by a haze to the corneal stroma, often with associated corneal vascularisation.6 In endothelial disease there may be folds to Descemets layer (the basement membrane that lies between the corneal proper substance, also called stroma, and the endothelial layer of the cornea), keratic precipitates and/or an associated anterior uveitis.6 Investigation with PCR can be useful where there is diagnostic uncertainty. Management depends on the layer affected. Typically, epithelial disease can be managed with topical antivirals.6 Stromal and endothelial disease are usually treated with a combination of oral anti-virals and topical steroid but specialist input and close follow-up is particularly required in these patients.6 

Fig.2 Dendritic lesion seen in epithelial herpes simplex keratitis when stained with fluorescein image via Shutterstock

Herpes Zoster Keratitis also presents differently depending on the layer of the cornea affected. Epithelial disease may cause punctate epithelial erosions or pseudodendrites, stromal disease may cause infiltrate formation and endothelial disease causes localised corneal oedema and Descemet membrane folds.6 Specialist ophthalmic review is required and treatment involves systemic antivirals with the addition of topical lubricants and/or steroids depending on the presentation.6

Acanthamoeba keratitis is a rare but devastating disease that typically presents in contact lens wearers, particularly those with poor hygiene practices.10 It may present in a variety of different ways but can easily be missed and treatment delayed resulting in poor visual outcomes. Clinicians should therefore have a very low threshold to refer patients who wear contact lenses who present with a red eye. Patients who are suspected to have any form of keratitis should be referred urgently to ophthalmology.

Fig.3 Bacterial corneal ulcer with white infiltrate – image via Shutterstock

Other Causes

Other causes of an acute red eye to consider include:

  • Conjunctivitis (bacterial, viral, allergic, chemical)
  • Dry eye
  • Blepharitis
  • Corneal abrasion
  • Episcleritis
  • Scleritis
  • Subconjunctival haemorrhage.

References

  1. Khazaeni B, Zeppieri M, Khazaeni L. Acute Angle-Closure Glaucoma. [Updated 2023 Nov 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.
  2. Royal College of Ophthalmology. The Management Of Angle-Closure Glaucoma. Rcophth.ac.uk. 2022 Jun [accessed 2024 Nov 19]
  3. Simakurthy S, Tripathy K. Endophthalmitis. [Updated 2023 Aug 25]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-.
  4. American Academy of Ophthalmology. Endophthalmitis – EyeWiki. Eyewiki.org. 2024 Sep 7 [accessed 2024 Nov 19].
  5. Results of the Endophthalmitis Vitrectomy Study. A randomized trial of immediate vitrectomy and of intravenous antibiotics for the treatment of postoperative bacterial endophthalmitis. Endophthalmitis Vitrectomy Study Group. Archives of ophthalmology. 1995;113(12):14791496.
  6. Denniston AKO, Murray PI, editors. Oxford handbook of ophthalmology. 4th ed. Oxford University Press; 2018.
  7. American Academy of Ophthalmology. Acute anterior uveitis – EyeWiki. Eyewiki.org. 2022 Dec 21 [accessed 2024 Nov 19].
  8. Herbert R, et al. Potential new fluoroquinolone treatments for suspected bacterial keratitis. BMJ open ophthalmology. 2022;7(1):e001002. http://dx.doi.org/10.1136/bmjophth-2022-001002.
  9. Awad R, et al. Fungal keratitis: Diagnosis, management, and recent advances. Clinical ophthalmology (Auckland, N.Z.). 2024;18:85106. http://dx.doi.org/10.2147/OPTH.S447138.
  10. Ting DSJ et al. Infectious keratitis: an update on epidemiology, causative microorganisms, risk factors, and antimicrobial resistance. Eye. 2021;35(4):10841101.