Keratitis

Keratitis is a condition characterised by inflammation of the cornea, the transparent, dome-shaped surface that covers the front of the eye. This ocular disorder can be caused by various factors, including bacterial, viral, fungal, or parasitic infections, as well as injuries, contact lens wear, or underlying autoimmune diseases. The inflammation of the cornea can lead to symptoms such as eye pain, redness, light sensitivity, blurred vision, and in severe cases, vision loss. Prompt diagnosis and appropriate treatment are crucial to prevent complications and preserve vision. Management typically involves a combination of topical or oral medications tailored to the underlying cause of the keratitis. Understanding the causes, symptoms, and treatment options for keratitis is essential for effective management and prevention of potential complications.

Symptoms

Recognising the symptoms of keratitis is crucial for prompt diagnosis and appropriate management.

Eye Pain and Discomfort

One of the hallmark symptoms of keratitis is eye pain or discomfort. Patients often describe it as a sharp, stabbing pain that worsens with blinking or rubbing the eyes. The pain may be accompanied by a feeling of foreign body sensation, as if there’s something lodged in the eye, making it uncomfortable to keep the eye open.

Redness

Inflammation of the cornea typically leads to redness in the affected eye(s). The blood vessels in the conjunctiva, the thin membrane covering the white part of the eye, become dilated, resulting in a reddish appearance. The degree of redness can vary from mild to severe, depending on the underlying cause and the extent of corneal involvement.

Light Sensitivity (Photophobia)

Keratitis often causes heightened sensitivity to light, known as photophobia. Even normal indoor lighting or sunlight may trigger discomfort and pain in affected individuals. Photophobia can lead to squinting, avoidance of bright environments, and the need to shield the eyes from light sources.

Blurred Vision

Corneal inflammation can disrupt the smoothness and transparency of the cornea, leading to blurred or distorted vision. This symptom may range from mild blurriness to severe vision loss, depending on the severity of the condition. Individuals with keratitis may notice difficulty in focusing on objects, particularly at a distance, and may experience fluctuations in visual acuity.

Excessive Tearing (Epiphora)

Excessive tearing, or epiphora, is another common symptom of keratitis. The eye’s natural response to irritation or inflammation is to produce tears as a protective mechanism. However, in keratitis, the tears may not adequately lubricate the eye or wash away irritants, leading to a cycle of increased tearing and persistent discomfort.

Eye Discharge

Depending on the underlying cause of keratitis, patients may experience various types of eye discharge. This discharge can range from watery to thick, mucous-like discharge, and may be accompanied by crusting around the eyelids, especially upon waking. The presence of discharge may indicate an infectious component to the keratitis, such as bacterial or viral involvement.

Sensation of Something in the Eye

Individuals with keratitis often report a sensation of having something in their eye, despite no foreign body being present. This feeling of discomfort or irritation may persist even after attempts to rinse or flush the eye. This symptom, known as a foreign body sensation, can be distressing and may exacerbate other symptoms such as eye pain and redness.

Causes

Understanding the diverse causes of keratitis is essential for effective management and prevention of this sight-threatening condition.

Infectious Agents

• Bacterial Keratitis: Bacterial infections, commonly caused by organisms such as Staphylococcus aureus, Streptococcus pneumoniae, and Pseudomonas aeruginosa, can infiltrate the cornea through trauma or contact lens wear. Improper contact lens hygiene and extended wear increase the risk of bacterial keratitis.
• Viral Keratitis: Viral pathogens, including herpes simplex virus (HSV) and varicella-zoster virus (VZV), can cause viral keratitis. HSV keratitis, in particular, may result in recurrent episodes of corneal inflammation, leading to scarring and visual impairment.
• Fungal Keratitis: Fungal infections, often associated with agricultural or outdoor activities, can penetrate the cornea through trauma with plant material or contaminated soil. Fusarium and Aspergillus species are common fungal culprits implicated in fungal keratitis.
• Parasitic Keratitis: Acanthamoeba keratitis, caused by the protozoan Acanthamoeba, is a rare but serious form of keratitis associated with contact lens wear, contaminated water exposure, or corneal trauma. The amoeba can invade the corneal epithelium, leading to severe inflammation and potential vision loss.

Mechanical Trauma

• Corneal Abrasions: Abrasions or scratches on the corneal surface, often resulting from foreign bodies, contact lens misuse, or eye injuries, can predispose the cornea to inflammation and infection. Even minor trauma can disrupt the corneal epithelium, creating a gateway for microbial invasion.
• Contact Lens-Related Trauma: Improper contact lens hygiene, extended wear, and overnight use increase the risk of corneal trauma and subsequent keratitis. Contact lens-induced keratitis, whether due to mechanical irritation or microbial contamination, underscores the importance of proper lens care and compliance with wearing schedules.

Environmental Factors

• Ultraviolet (UV) Radiation: Prolonged exposure to UV radiation, particularly from sunlight or artificial sources such as tanning beds, can contribute to corneal inflammation and photokeratitis. UV-induced keratitis, also known as snow blindness or welder’s flash, manifests as painful corneal inflammation and temporary vision loss.
• Chemical Exposure: Chemicals found in household cleaners, industrial solvents, or agricultural pesticides can cause chemical keratitis upon ocular exposure. Direct contact with corrosive substances can lead to severe corneal damage and inflammation, necessitating prompt irrigation and medical intervention.

Underlying Conditions

• Autoimmune Disorders: Autoimmune conditions such as rheumatoid arthritis, lupus, and Sjögren’s syndrome may predispose individuals to keratitis due to immune dysregulation and ocular surface inflammation.
• Dry Eye Syndrome: Insufficient tear production or poor tear quality associated with dry eye syndrome can lead to corneal epithelial defects and inflammation, increasing the susceptibility to infectious keratitis and other ocular complications.

Treatments

The therapeutic approach to keratitis varies depending on the underlying cause, severity of inflammation, and individual patient factors.

Antimicrobial Therapy

• Bacterial Keratitis: Empirical treatment with broad-spectrum topical antibiotics, such as fluoroquinolones or fortified antibiotics (e.g., vancomycin, ceftazidime), is initiated pending culture and sensitivity results. Adjustments to targeted therapy are made based on microbiological findings to optimize efficacy and minimize resistance.
• Viral Keratitis: Antiviral agents, such as topical acyclovir, ganciclovir, or trifluridine, are prescribed for herpetic keratitis caused by herpes simplex virus (HSV) or varicella-zoster virus (VZV). Systemic antiviral therapy may be warranted for severe or recurrent cases, particularly involving stromal or endothelial involvement.
• Fungal Keratitis: Antifungal medications, including natamycin, amphotericin B, or voriconazole, are employed for the treatment of fungal keratitis. Topical therapy is often supplemented with oral antifungal agents in severe or refractory cases to achieve adequate corneal penetration and systemic coverage.

Anti-inflammatory Agents

• Corticosteroids: Topical corticosteroids, such as prednisolone or dexamethasone, play a crucial role in reducing inflammation and mitigating the immune response in keratitis. However, their use is typically reserved for non-infectious or adequately treated infectious keratitis to avoid exacerbating microbial proliferation and corneal thinning.
• Nonsteroidal Anti-inflammatory Drugs (NSAIDs): NSAIDs, such as ketorolac or diclofenac, provide adjunctive anti-inflammatory therapy in keratitis, particularly in cases of ocular surface inflammation or discomfort. These agents help alleviate pain, reduce swelling, and improve patient comfort without compromising microbial control.

Supportive Measures

• Lubrication: Preservative-free artificial tears or ointments are utilized to maintain corneal hydration, alleviate dryness, and promote epithelial healing in keratitis. Frequent instillation of lubricating drops helps prevent further epithelial damage and discomfort associated with ocular surface irregularities.
• Bandage Contact Lenses: Soft or silicone hydrogel bandage contact lenses are employed as adjunctive therapy in refractory or recurrent epithelial defects associated with keratitis. These lenses protect the cornea, promote reepithelialization, and improve patient comfort during the healing process.

Surgical Intervention

• Corneal Debridement: Mechanical debridement of necrotic tissue, epithelial defects, or infiltrates may be necessary in cases of severe or non-resolving keratitis. This procedure facilitates better penetration of antimicrobial agents, reduces microbial burden, and promotes corneal healing.
• Corneal Transplantation: In advanced cases of keratitis associated with corneal thinning, perforation, or scarring, corneal transplantation (keratoplasty) may be considered to restore visual function and structural integrity. Lamellar or penetrating keratoplasty techniques are tailored to the extent of corneal involvement and underlying pathology.