Published in Primary Care

The Optometrist's Guide to Red Eye

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7 min read

Red eye is one of the most common ocular concerns that arise on a weekly basis in the offices of optometrists and physicians. Here, we're covering the most common causes of red eye.

The Optometrist's Guide to Red Eye
It’s Friday night, and the clinic is closing in less than an hour when you receive an emergency call. The patient complains of a red eye. How many optometrists can relate to this scenario?
Red eye is one of the most common ocular concerns that arise on a weekly basis in the offices of optometrists and physicians. Most patients continue to visit their physicians for these concerns. An Australian study found that 64% of treated cases by primary care physicians were misdiagnosed and 10% led to serious complications.6 Misdiagnosis and not knowing when to refer the patients can result in devastating consequences. Before going over a few common conditions, let’s go back to the basics.

Back to the basics

One of the basic aspects as physicians is communication. Taking an in-depth case history and determining the patient’s chief complaint is beneficial to streamline the eye examination. The chief complaint of red eyes may yield an extensive list of differentials and a detailed case history can formulate differential diagnoses. Listed below are a few important questions.

Case history for red eye

FrequencyPrevious episode or history?
OnsetAcute vs Chronic?
LocationUnilateral or Bilateral? Diffuse or Localized?
DurationHow long have symptoms been present?
Alleviating factorsUse of artificial tears or other eye drops? Cold compresses?
Related symptomsDischarge? Burning? Tearing? Itching? Pain? Photophobia? Foreign body sensation? Blurry vision?
QualityPain threshold? (on scale of 1 to 10)
Ocular historyHistory of trauma or chemical injury? Exposure to an infected person? Contact lens wearer? Use of topical or over the counter drops?
Medical/Social historyRecent illness or infections? Computer use? Occupation? Smoking history?
Communication, observations and listening to key phrases can narrow down a list of differential diagnoses. For example: a patient says ‘My eyes are always itchy’ which may indicate allergies or if your patient walks into the exam room wearing sunglasses, the patient may be photophobic. Good communication skills and bedside manner are critical skills for all physicians and can help lead to a more accurate diagnosis for the patient.
This article is a review of a few conditions commonly associated with red eyes, listed in order of urgency of the conditions (least to most urgent).
  1. Subconjunctival hemorrhage
  2. Dry eye syndrome
  3. Conjunctivitis
  4. Contact lens related problems
  5. Episcleritis/Scleritis
  6. Iritis
  7. Foreign body & Corneal abrasion

Subconjunctival hemorrhage

Subconjunctival hemorrhage is defined as diffuse or focal area of blood under the conjunctiva due to ruptured conjunctival blood vessel. Patients are usually asymptomatic.
Figure 1: Subconjunctival hemorrhage2
Key phrase“I did not notice anything until someone said something.”
Etiology Idiopathic Valsalva (coughing, sneezing, constipation) Trauma (isolated or associated with retrobulbar hemorrhage or ruptured globe) Systemic conditions (hypertension, diabetes) Bleeding disorders Use of antiplatelet or anticoagulant medications (aspirin, clopidogrel, warfarin)
SignsFocal or diffused hemorrhage Rule out conjunctival lesions and ruptured globe (check extraocular motility, intraocular pressure) If recurrent or suspect bleeding disorder, refer for blood work (bleeding time, prothrombin time, partial thromboplastin time, complete blood count, liver function test, protein C and protein S)
TreatmentCondition is self-limiting with spontaneous resolution within 2-3 weeks Artificial tears may be given if ocular irritation is present
Follow upNo follow up necessary unless condition reoccurs Refer to family doctor for high blood pressure and bleeding disorder if recurrent

Dry eye syndrome

Keratoconjunctivitis sicca, also known as dry eye syndrome, is caused by decreased tear production or poor tear quality. It may be associated with increased age, female > male, medications and some medical conditions.
Key phrase“My eyes are watering and I feel like something is in it.”
SymptomsBurning/Dryness Foreign body sensation Excessive tearing
SignsScant, irregular tear prism at inferior eyelid margin Decreased tear break-up time Punctate corneal or conjunctival staining Excess mucus or debris in tear film Meibomian gland dysfunction
TreatmentArtificial tears Lubricating ointment QHS or lubricating gel QHS Lifestyle modifications (use of humidifiers, smoking cessation) Cyclosporine 0.05% BID for chronic dry eye
Follow upDepends on severity


Conjunctivitis is the most common cause of red eyes, viral being the most prevalent. The term conjunctivitis refers to the inflammation of the conjunctiva. Below are a few clinical pearls for differentiating viral, bacterial and allergic conjunctivitis.

Viral Conjunctivitis
Figure 2: Viral conjunctivitis2
Key phrase“I think I have pink eye.”
PrevalenceMost prevalent (80%)
ContagiousHighly for 10-12 days
Medical historyRecent upper respiratory tract infection(cough/flu)
LocationUnilateral or bilateral
SymptomsItching/Burning Foreign body sensation Tearing
Preauricular nodesTender nodes
Other signsFollicles inferiorly Edematous eyelids Intraepithelial microcyst Subepithelial infiltrates
TreatmentSelf-limiting; however, palliative therapies include: Artificial tears Mild steroid (if necessary)
CounselingCopious handwashing Avoid touching eyes
Follow up2 weeks or sooner if condition worsens

Bacterial Conjunctivitis
Figure 3: Bacterial conjunctivitis3
Key phrase“My lids are shut closed when I wake up.” “My eyes are goopy.”
PrevalenceSecond most prevalent Children > Adults
Medical historyNone
LocationUnilateral or bilateral
SymptomsForeign body sensation Matted eyelashes
DischargeWhite/yellow purulent
Preauricular nodesNo
Other signsConjunctival papillae Moderate hyperemia Conjunctival chemosis
TreatmentBroad spectrum antibiotic (5-7 day course)
CounselingAvoid touching eyes
Follow up2-3 days then every 5-7 days until resolved

Allergic conjunctivitis
Figure 4: Allergic conjunctivitis2
Key phrase“My eyes are itchy."
PrevalenceDuring allergy season
Medical historySeasonal allergies Airborne allergens
LocationUsually bilateral
SymptomsItching & burning
Preauricular nodesNo
Other signsConjunctival papillae Mild hyperemia Conjunctival chemosis Red edematous eyelids
TreatmentCold compresses Artificial tears Anti-histamine or Mast cell inhibitors Mild steroid (if necessary) Oral anti-histamine (if necessary)
CounselingEliminate allergen Avoid rubbing eyes
Follow up1-2 weeks

Contact lens related problems

Contact lenses are used for correcting refractive errors, for cosmetic use and for therapeutic use such as bandage lens. However, contact lens overwear may cause several complications including giant papillary conjunctivitis, superior limbic keratoconjunctivitis & corneal ulcer.

Giant Papillary Conjunctivitis
Figure 5: Giant papillary conjunctivitis3
Key phrase“My eyelids feel heavy and I need to rub them.”
Etiology Contact lens overwear Loose fit (excessive lens movement)
Symptoms Itching & burning Foreign body sensation
SignsUpper tarsal micropapillae Superior limbal injection Ropy mucous discharge
TreatmentEducate patient on proper contact lens care For mild GPC: Decrease wear time of contact lenses Topical mast cell inhibitor or antihistamine For severe GPC: Suspend use of contact lenses Topical steroid
Follow up2-4 weeks

Superior Limbic Keratoconjunctivitis
Figure 6: Superior limbic keratoconjunctivitis2
Key phrase“I cannot wear my contacts for long anymore.” “I have to take out my contact lenses more often.”
Etiology Hypersensitivity/toxicity reaction to preservatives in contact lens solution
Symptoms Itching & burning Foreign body sensation Contact lens intolerance
SignsUpper tarsal micropapillae Superior limbal injection Pannus at 12 o’clock
TreatmentSuspend use of contact lenses Switch to preservative free contact lens solution Use preservative free artificial tears Topical steroid (if necessary)
Follow up2-4 weeks

Corneal Infiltrate & Corneal Ulcer
Figure 7: Corneal ulcer3
Key phrase"My eyes are red and hurt.”
Etiology Bacterial Fungal Acanthamoeba
Symptoms Pain Photophobia Contact lens intolerance
SignsWhite stromal opacity Corneal thinning/ulcer Anterior chamber reaction
TreatmentCycloplegic drops for comfort For mild condition: Fluoroquinolone q1-2 hrs For severe condition: Fluoroquinolone q1-2 hrs
Follow up1 day Maintain treatment until condition resolves

Episcleritis & Scleritis

Episcleritis is a localized area of inflammation of connective tissue between sclera and conjunctiva involving whereas scleritis is defined as an inflammation of the scleral tissue.

Figure 8: Episcleritis3
Key phrase“My eye is red in the corner.”
Epidemiology80% simple, 20% nodular Bilateral in 33% of cases
Etiology Idiopathic Infectious (herpes zoster) Other (rosacea, atopy, collagen vascular disease, gout, thyroid disease)
Symptoms Mild pain Hyperemia
SignsSectoral injection Chemosis Episcleral nodules Cells and flare
TreatmentArtificial tears Topical steroid (Fluorometholone QID) Oral NSAID for severe cases
Follow up1 week
PrognosisSelf-limiting condition & good prognosis Recurrent in 67% of cases

Figure 9: Scleritis3
Key phrase“My eye is red and it hurts.”
Epidemiology40% diffuse, 44% nodular, 14% necrotizing
Etiology Idiopathic Connective tissue disease Herpes zoster ophthalmicus Syphilis
Symptoms Severe pain Hyperemia & chemosis
SignsDecreased vision Diffused injection Chemosis Scleral nodules Globe tenderness Cells and flare
TreatmentOral steroid (Prednisone 60-100 mg po QD) Systemic NSAID
Follow up1 week or sooner if symptoms worsen
PrognosisDepends on etiology (poor for necrotizing) Recurrence is common


Iritis, also known as anterior uveitis, is an idiopathic inflammation of uvea (iris, choroid and/or ciliary body).
Figure 10: Keratic precipitates3
Key phrase“I am light sensitive.”
Symptoms Pain Redness Photophobia Decreased vision
SignsAnterior chamber reaction (cells and flare) Ciliary flush Keratic precipitates Hypopyon Iris synechiae
TreatmentCycloplegic bid Topical steroid (Prednisolone acetate 1% q4-6 hrs depending on severity) May consider steroid ointment overnight
Follow upEvery 1-7 days depending on severity, assess patient’s IOP at each visit Taper steroid once anterior chamber reaction has resolved

Foreign body & corneal abrasion

Defined as defects to the corneal epithelium, corneal abrasion can cause irritation, pain, tearing and photophobia.
Figure 11: Corneal abrasion3
Key phrase“Something got into my eye and it hurts.”
Risk factorsForeign body Trauma Contact lens use
Symptoms Sharp pain Photophobia Foreign body sensation Tearing
SignsEpithelial defect (stains with fluorescein) Conjunctival injection Mild anterior chamber reaction Protective ptosis
TreatmentFor non-contact lens wearer: antibiotic ointment q2-4 hrs or antibiotic drops QID For contact lens wearer: anti-pseudomonas coverage, antibiotic ointment or drop QID For abrasion secondary to fingernail or vegetative matter: Fluoroquinolone QID For large abrasion: place bandage contact lens
Follow upFor bandage contact lens: follow up within 24 hrs for re-evaluation Central or large abrasion: follow up within 24 hrs for re-evaluation Peripheral or small abrasion: follow up within 2-5 days


Red eye is the most common complaint found amongst patients and the concept that every case is a ‘pink eye’ is a huge misunderstanding. The average person will call their family physician if they have an eye problem. There is a misconception that optometrists only provide a spectacle prescription. Upon questioning patients, they are often unaware that optometrists may provide more detailed care including urgent eye problems. Reaching out to family physicians and providing reports for mutual patients can build a foundation for better communication between optometrists and family physicians. Educating patients and the public with regards to our role as primary care optometrists may help to prevent misdiagnosis and further patient consequences. Stay tuned for more details regarding atypical conditions in association with red eyes.


  1. Cronau H, Kankanala R, Mauger T. Diagnosis and Management of Red Eye in Primary Care. American Family Physician. 2010;81(2):137-144.
  2. Ehlers JP, Shah CP, Fenton GL. Wills Eye Manual Office and Emergency Room Diagnosis and Treatment of Eye Disease. Philadelphia, PA: Wolters Kluwer Health; 2012.
  3. Friedman NJ, Kaiser PK. The Massachusetts Eye and Ear Infirmary: Illustrated Manual of Ophthalmology. Philadelphia, PA: Saunders, Elsevier; 2014.
  4. Frings A, Geerling G, Schargus M. Red Eye: A Guide for Non-specialists. Deutsches Arzteblatt International. 2017;114:302-312. doi:10.3238
  5. Gilani C, Yang A, Yonkers M, Boysen-Osborn M. Differentiating Urgent and Emergent Causes of Acute Red Eye for the Emergency Physician. Western Journal of Emergency Medicine. 2017;18(3):509-517. doi:10.5811
  6. Statham MO, Sharma A, Pane AR. Misdiagnosis of acute eye diseases by primary health care providers: incidence and implications. Med J Aust. 2008;189:402–404
  7. Vo A, Williamson J. Red Eye Roundup. Review of Optometry. Published March 15, 2019. C
Roshni Naik, OD
About Roshni Naik, OD

Dr. Roshni Naik is a 2016 graduate from New England College of Optometry. She is board certified to practice in Canada and the United States and is qualified to prescribe therapeutic agents for treatment of ocular disease. Dr. Naik is a member of the College of Optometrists of Ontario, the Ontario Association of Optometrists, the Canadian Association of Optometrists and the American Optometry Association. Dr. Naik is currently an associate optometrist at a private practice in Milton, Ontario. She is passionate and committed to providing exceptional eye care to patients of all ages.

Roshni Naik, OD
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