PATHOPHYSIOLOGY 

The pathophysiology of red eye is dependent on its specific aetiology.

CAUSES OF PAINLESS RED EYES

• Blepharitis
• Conjunctivitis 
• Episcleritis 
• Dry eye syndrome
• Subconjunctival hemorrhage which can be idiopathic, as result of hypertension, bleeding disorders, warfarin, NSAIDS or  from viral illnesses like measles and yellow fever

CAUSES OF PAINFUL RED EYES

• Scleritis
• Corneal abrasion, ulcer, foreign body or any other causes of keratitis
• Iritis/Uveitis
• Acute angle closure glaucoma
• Endophthalmitis
• Orbital cellulitis

CLINICAL PRESENTATION AND TREATMENT

• PAINLESS RED EYES

BLEPHARITIS: Is the inflammation of the margins of the eye lid which can be anterior, posterior or both. Anterior affects the base of the eye lashes and it is caused by bacterial infections or seborrheic dermatitis. Posterior blepharitis is mainly caused by meiboman gland dysfunction since it affects the meiboman glands.

Presentation includes burning sensation in the eye lids, eye redness, itching, scaling and crusting of the eyelids.

Common treatment include cleansing of the eyelid and eye lashes, warm compresses, application of artificial tear and in some cases topical antibiotics like erythromycin ointment can be included. 

CONJUNCTIVITIS: This is the most common cause of red eyes, it is the inflammation of the conjunctiva. It can be caused by viruses, bacteria, irritants and allergens.

Symptoms include foreign body sensation, eye redness, eye discharge, itching or tearing. 

Patients with bacterial conjunctivitis usually have eye discharge, tearing is common in viral conjunctivitis and allergic conjunctivitis is notorious for itching. Emphasis on good hygiene such as meticulous hand washing is important in decreasing the spread of acute viral and bacterial conjunctivitis

Bacterial conjunctivitis may require topical antibiotics after a week of conservative treatment. . Caution should be taken with use of steroid in the management of red eye, because this can worsen the patient's condition when used for patients with bacteria conjunctivitis.

Viral conjunctivitis is usually self-limiting, they may require counselling against activities that enhance the spread of the eye secretion, and herpetic viruses may however need topical antivirals such as valacyclovir or acyclovir.

As for allergic conjunctivitis, cool compresses, topical+/- oral antihistamines/mast cell stabilisers are used. In severe cases, corticosteroids may be included. These are however advised to be reserved for the ophthalmologists.

Figure 1: Bacterial conjunctivitis. Picture source: Bhamra J, Sylvestre-Bouchard A. Management and Treatment of Red Eyes in Primary Care.

Figure 2: Viral conjunctivitis. Picture source: Bhamra J, Sylvestre-Bouchard A. Management and Treatment of Red Eyes in Primary Care.

EPISCLERITIS: This is the inflammation of the episclera, the most superficial layer of the sclera beneath the conjunctiva. It usually affects one eye but occasionally both and occurs in a diffuse or sectoral pattern. 

Symptoms include tearing, eye redness, discomfort or sensitivity to light. It is occasionally associated with autoimmune disorders like lupus disease or rheumatoid arthritis.

A close differential of episcleritis is scleritis. Scleritis however has high level of deep and boring pain with severe tenderness. The eye redness in scleritis still persists with the application of phenylephrine drops.

Episcleritis can be managed with chilled artificial tears, cold compress and steroidal or non-steroidal antiinflammatory drugs.

Figure 3: Episcleritis. Picture source: Bhamra J, Sylvestre-Bouchard A. Management and Treatment of Red Eyes in Primary Care.

DRY EYE SYNDROME (also known as) KERATOCONJUNCTIVITIS SICCA: This results from inadequate or poor quality tears affecting the lubrication and protection of ocular surface. It can be caused by increased screen time, systemic disease, ageing, medications or eye lid abnormalities.

Symptoms include foreign body sensation, redness, light sensitivity and reduced vision.

Treatment is by addressing the underlying cause, eyelid hygiene and frequent blinking.

SUBCONJUNCTIVAL HEMORRHAGE: This is bleeding beneath the conjunctiva. It can be caused by hypertension, trauma, bleeding disorders or viral illnesses. The cause can also be idiopathic.

It presents with painless bright red patch on the white part of the eye without affectation of vision.

The management is usually supportive and by addressing the underlying cause.

Figure 4: Subconjunctival haemorrhage. Picture source: Bhamra J, Sylvestre-Bouchard A. Management and Treatment of Red Eyes in Primary Care.

• PAINLESS RED EYES

SCLERITIS:This is inflammation of the sclera.

It presents with red eye, severe deep, boring pain to the back of the eye or head, thinning of sclera(purple hue) or eye tenderness.

It can be treated using NSAIDS like ibuprofen 

IRITIS/UVEITIS: This is the inflammation of the anterior and or the posterior uveal tract. In most cases, the cause cannot be determined. However, like episcleritis it can be caused by autoimmune disorders. Trauma can also be a cause.

Patients can present with eye pain, eye redness or photophobia.

Treatment can be done with prednisolone, dexamethasone or cyclopentolate eye drops with further review by the ophthalmologists.

CORNEAL ABRASION, ULCER OR FOREIGN BODY: This is abrasion, ulceration or foreign body in the cornea usually secondary to ocular trauma.

It presents with eye pain, eye redness, photophobia, tearing or presence of foreign body in the cornea, corneal opacity, infiltrate or epithelial loss.

Treatment is by ocular antibiotics with removal of foreign body if present and further referral to the ophthalmologists.

ACUTE ANGLE CLOSURE GLAUCOMA: It occurs in patients who have pre-existing narrowing of the angle of the anterior chamber. Older patients and hypermetropic patients are at increased risk.

Patients may present with severe eye pain, eye redness, nausea and vomiting, corneal oedema, shallow anterior chamber, high IOP.

Treatment is by oral or intravenous acetazolamide 500mg stat, then drops q15mins  × 3 doses, timolol, brimonidine or latanoprost, with immediate referral to the ophthalmologists.

ENDOPHTHALMITIS: Is an inflammatory condition of aqueous and vitreous humour usually caused by infection. It can be complicated by decreased vision or permanent loss of vision.

Patients present with eye pain, red eye, blurry vision, hypopyon or anterior chamber cells. There can be history of recent ocular trauma or eye procedure.

Patient should be commenced on ocular and intravenous antibiotics with prompt referral to the ophthalmologists.

ORBITAL CELLULITIS: This is the infection of the soft tissues posterior to the orbital septum. It is caused by infection from adjacent structure, direct inoculation or hematogenous spread. 

Patients can present with eye pain, redness, swelling, proptosis, ophthalmoplegia, decreased vision or pain with eye movements.

Treatment is by intravenous antibiotics with immediate referral to the ophthalmologists.

CONCLUSION

Red eye is a common eye condition seen in primary care. Correct understanding of the causes, proper and prompt evaluation are essential in its management. Refer patients promptly presenting with red flags to ophthalmologists. Avoid treatment with steroids in patients with bacterial conjunctivitis. Educate patients on not using harmful substances to treat red eyes.