Introduction 

What is conjunctivitis?

Conjunctivitis is the inflammation of the conjunctiva (the thin, transparent membrane that protects the eye). Conjunctivitis can cause the eye to turn red or pink. The most common symptoms of conjunctivitis are swelling and redness. Due to the swelling, the blood vessels become more prominent.¹

What is keratoconjunctivitis? 

Keratoconjunctivitis originated from two words: “keratitis” indicates inflammation of the cornea (protective curved outer layer that focuses light), and “conjunctivitis” indicates involvement of the conjunctiva. Keratoconjunctivitis is a condition that affects the cornea and conjunctiva. This condition has various causes and manifestations, making it challenging to diagnose in a clinical setting.²

Anatomy of the conjunctiva 

The conjunctiva of the eye protects and lubricates the eye by producing mucus and tears. It helps block the entry of germs and supports immune defence. This membrane lines the inner surface of the eyelids and covers the sclera (the white part of the eye). It contains numerous blood vessels and a well-developed lymphatic network. The conjunctiva covers the front, non-corneal parts of the eye, including the fornices and eyelids. It acts as a physical barrier, produces mucin (protein found in mucus) through goblet cells to help maintain eye moisture, and contains immune cells that support eye surface defence.³

Anatomy of the cornea

The cornea is an avascular (lacks blood vessels), transparent tissue that serves as a structural barrier to keep infections out of the eye. Along with the tear film, it provides the eye with the appropriate anterior refractive surface to focus light. The cornea provides about two-thirds of the eye’s focusing power. Because the normal human cornea lacks blood vessels, it receives nutrients primarily from the aqueous humour. Its blood supply is limited to small vessels at its periphery (edges) and to components delivered via the tear film and aqueous humour from branches of the facial and ophthalmic arteries.⁴

Clinical manifestations of keratoconjunctivitis 

Some of the common symptoms of keratoconjunctivitis include:

• Redness
• Blurred vision
• Photophobia (eyes are sensitive to light)
• A feeling that something is in the eye
• Extreme tearing
• Dryness 

In severe cases of keratoconjunctivitis, the symptoms include:²

• Sharp pain
• Mucopurulent discharge (thick, yellow or green discharge)
• Due to irritation, patients face difficulty in keeping the eye open 

Types of keratoconjunctivitis

Generally, keratoconjunctivitis can be classified into two categories based on cause: infectious and non-infectious. Infectious types of keratoconjunctivitis include bacteria. However, viral infections are frequently observed. Non-infectious types of keratoconjunctivitis include toxic, allergic or immune-mediated causes. If the onset of keratoconjunctivitis is less than a week, then it is known as hyperacute keratoconjunctivitis. If the onset is between three and four weeks, it is described as acute keratoconjunctivitis. If keratoconjunctivitis lasts more than four weeks, it is known as chronic keratoconjunctivitis.² 

Based on the cause, keratoconjunctivitis can be further classified as:

• Viral keratoconjunctivitis
• Bacterial keratoconjunctivitis
• Allergic keratoconjunctivitis
• Dry eye-related keratoconjunctivitis

Viral keratoconjunctivitis

Viral keratoconjunctivitis is caused by viruses. The most common type is adenovirus. Outbreaks of viral keratoconjunctivitis occur in crowded settings, such as workplaces or schools. 

Viruses associated with keratoconjunctivitis:² 

• Adenovirus
• Herpes simplex virus
• Varicella-zoster virus (VZV)
• Cytomegalovirus (CMV) 

Types of viral keratoconjunctivitis:^2,5 

• Epidemic keratoconjunctivitis
• Herpes zoster ophthalmicus 
• Herpetic blepharokeratoconjunctivitis 

Epidemic keratoconjunctivitis (EKC) is a viral keratoconjunctivitis caused by adenovirus. Adenovirus is a non-enveloped virus with double-stranded DNA (deoxyribonucleic acid). This virus commonly infects the eyes and the respiratory, gastrointestinal, and genitourinary systems. Studies have shown that human adenovirus types 8, 19, 37, and 54 are primarily responsible for EKC outbreaks.²

Adenoviruses are highly resistant to environmental conditions and spread between individuals via infectious bodily fluids, especially tears. EKC can affect people of all ages and occurs year-round worldwide, but is mainly endemic in Asia and primarily affects children.

EKC patients experience severe pain, diminished visual acuity, a strong foreign body sensation, and frequently a generalised sense of being ill for three to six weeks. Sometimes after EKC, small cloudy spots (granular deposits) called nummuli can form on the cornea, and they may linger for several months.⁶

Herpes zoster ophthalmicus affects the cornea and conjunctiva and is caused by varicella zoster virus.² Clinical manifestations include fever, pain, headache, facial rash, discomfort, eye discharge and redness. Herpes zoster ophthalmicus can lead to permanent vision impairment. Hence, it is important to visit an ophthalmologist if symptoms occur.⁷

Herpetic blepharokeratoconjunctivitis is caused by the herpes simplex virus (HSV) and is characterised by chronic keratitis with dendritic ulceration.^2,5

Herpetic keratoconjunctivitis is characterised by multinucleated giant cells (large cells formed by the fusion of smaller cells) and intranuclear inclusion bodies (an abnormal collection of debris such as proteins or viruses within a cell’s nucleus).² 

Individuals stay contagious for 10 to 14 days after an estimated 5 to 12 days of incubation. This prolonged healing period should be communicated to patients and caregivers to relieve concerns about lingering symptoms and reduce unnecessary follow-up appointments with medical professionals. Cool compresses, artificial tears, and topical antihistamines can all help alleviate symptoms, while there is currently no proven cure. The potential of topical ganciclovir and cidofovir as therapeutic options has been demonstrated in vitro.²

Bacterial keratoconjunctivitis

Organisms involved in bacterial keratoconjunctivitis include:

• Staphylococcus aureus 
• Streptococcus pneumoniae
• Pseudomonas aeruginosa
• Neisseria gonorrhoeae 
• Chlamydia trachomatis

Staphylococcus aureus and Streptococcus pneumoniae cause acute bacterial keratoconjunctivitis. In those who wear contact lenses, keratoconjunctivitis is caused by a Pseudomonas aeruginosa infection, and if left untreated, it can lead to corneal perforation. Neisseria gonorrhoeae and Chlamydia trachomatis, which cause keratoconjunctivitis in neonates, appear in the initial days of life. A heavy infiltration of neutrophils (a type of white blood cell) and regions of stromal necrosis (cell death of keratocytes in the cornea) are usually characteristic of bacterial keratoconjunctivitis. For bacterial infections, broad-spectrum topical antibiotics such as moxifloxacin are effective.²

Allergic keratoconjunctivitis

Allergic keratoconjunctivitis commonly involves environmental allergens. Vernal keratoconjunctivitis (VKC) is a serious form of allergic conjunctivitis with an uncertain cause. It is widely believed that an allergic mechanism, particularly involving the IgE-mediated mast cell pathway, plays a significant role in the development of symptoms. The condition is thought to result from a complex interplay among immune responses, genetic predisposition, and environmental factors such as allergens and air pollution.²

Vernal keratoconjunctivitis (VKC) is a recurring eye condition, more common in those assigned male at birth (AMAB) over five and in warm, dry climates. It typically worsens in spring and summer but may become year-round over time. Most cases improve by puberty, though some may progress to atopic keratoconjunctivitis. Chronic cases are more likely to have persistent symptoms.⁸

The clinical manifestations of vernal keratoconjunctivitis include:⁹

• Itching
• White mucus discharge
• Lacrimation
• Photophobia
• Sensation of pain in the eyes due to corneal involvement
• Sensation of a foreign body

Treatment for vernal keratoconjunctivitis (VKC) depends on the severity of the condition. In mild cases, simple steps like avoiding allergens, using cold compresses, practising good eyelid hygiene, and wearing sunglasses to reduce light sensitivity and protect from irritants can help. When symptoms are more intense, eye drops that stabilise mast cells or block histamines are commonly used. Dual-action drops that do both are especially helpful because they provide quick relief and help control the condition over time. Non-steroidal anti-inflammatory drops can also ease discomfort.

For more serious cases, doctors may prescribe steroid eye drops, but these should be used carefully and for short periods, as they can raise eye pressure. If the condition keeps coming back, steroid-sparing medications like cyclosporine or tacrolimus may be used to control inflammation long-term.

In rare, complex cases, especially when other allergic conditions like asthma or eczema are also present, systemic medications may be needed. These can include oral drugs such as montelukast or newer biologic treatments such as dupilumab or omalizumab, which target the underlying allergic response.⁸

Dry eye-related keratoconjunctivitis

Dry eye syndrome (DES), also called dry eye disease or keratoconjunctivitis sicca, is a common condition in which the eyes don’t produce enough tears or the tears evaporate too quickly, leading to discomfort and blurred vision. Treatment varies depending on the severity of the symptoms. For mild cases, using preservative-free artificial tears, gels, or ointments can provide relief by keeping the eyes moist. Warm compresses and eyelid cleaning may improve oil secretion from glands around the eyes, preventing tears from drying out too quickly. Simple lifestyle changes, like drinking enough water, using a humidifier, and blinking often during screen use, also help.

If symptoms persist, doctors may prescribe anti-inflammatory eye drops such as cyclosporine or tacrolimus to reduce inflammation. Steroid eye drops might be used for a short time but need careful monitoring. For more severe cases, small plugs called punctal plugs can be inserted to block tear drainage and keep eyes moist. Sometimes, a more permanent procedure, such as cautery, is needed. Low-dose oral doxycycline may also help reduce inflammation. In advanced cases, autologous serum drops made from the patient’s own blood can provide healing benefits, although they can be expensive. Most people find that a combination of these treatments, tailored to their needs, offers the best relief from dry eye symptoms.²

Summary 

Early identification and treatment of keratoconjunctivitis is crucial for preventing complications. Individuals should undergo regular eye check-ups. Use preventive measures, such as hand hygiene and regularly wearing protective glasses, to minimise the spread of the disease.