Introduction

Keratitis is the name of a medical condition of the inflammation and swelling of the cornea. The cornea is the clear dome-shaped cover at the front of the eyes, which focuses vision. The inflammation of the cornea can be due to multiple causes; therefore, keratitis may or may not be associated with an infection. Infectious keratitis is often caused by the invasion of bacteria, viruses or fungi; however, non-infectious keratitis is due to physical eye injuries, improper contact lens use, dry eye or Ultraviolet (UV) light exposure.¹Despite the underlying cause. This condition progresses rapidly and can result in serious symptoms if left untreated. Control of the inflammation and appropriate treatment are essential, which can prevent long-term symptoms such as scarring, vision loss, or corneal perforation.

Corneal scarring

Mechanism

Corneal scarring is a symptom of keratitis when the inflammation damages the cornea. The inflammatory response results in breaking down the collagen framework of the cornea and replacing the damaged corneal tissue with fibrous scar tissue during the healing process. Unlike healthy corneal cells, scar tissue lacks the structure required for light transmission as the tissue is not transparent.²

Effects

The scarring of the cornea results in opacity in the cornea, therefore reducing visual clarity because of the blocking of incoming light. Generally, when the scar tissue is located within or near the central visual axis, this can impair vision significantly. As well as this, the scarred cornea has an uneven surface, which can cause distortion and irregular astigmatism, which is a challenge to correct with standard glasses.³

Clinical signs

The clinical signs of corneal scarring are a slightly grey/ white area on the surface of the cornea, which can be visible on routine eye examination or require slit-lamp evaluation for full assessment. Depending on the severity and location, patients may also report blurred vision.

Prevention & treatment

In order to prevent this issue, early and correct treatment of keratitis is required. The process of eliminating infection through targeted antimicrobial therapy should begin as soon as possible. To control inflammation and reduce further damage to the cornea, anti-inflammatory drugs such as corticosteroids may be used as recommended by a healthcare professional. However, severe cases where this scarring results in vision loss may require surgical options like a corneal transplant to restore transparency and possibly improve vision.²

Vision loss

Direct causes

Vision loss is a critical symptom that can affect individuals as a result of keratitis and can result from several mechanisms. The most common is scarring over the central visual axis, which blocks or distorts light entering the eye. As well as this the healing process and inflammation may lead to an uneven surface of the cornea, causing irregular astigmatism that blurs vision and is difficult to correct. There can also be cases with more severity when the infection or inflammation extends to deeper layers of corneal tissue or even the anterior chamber, which can further impair vision.⁴

Types of vision loss

The vision loss can be temporary or permanent. Generally, temporary vision loss occurs due to active inflammation, swelling of the cornea or epithelial defects. This can be improved with proper treatment. On the contrary, permanent vision loss is often due to the condition which causes irreversible damage, such as scarring and deforming structure within the eye, so vision loss may remain despite the resolution of the infection.⁵

Risk factors

The possibility or extent of vision loss generally increases with delayed treatment, because the continuous infection and inflammation cause more severe damage. There are specific pathogens which tend to be more aggressive and cause rapid corneal destruction, such as Pseudomonas aeruginosa in contact lens users and Herpes simplex virus, increasing the risk of permanent loss of vision. 

Management

In order to manage vision loss, residual visual impairment must be addressed in addition to the underlying disorder. Moderate visual defects can be improved with the use of glasses or specialised contact lenses such as rigid gas permeable lenses, which are able to mask the irregularities of the surface. However, in situations where the individual has significant scarring or structural damage, surgical options of corneal grafting may need to be sought. Early intervention remains the most critical step in preserving vision.⁵

Corneal perforation

Pathophysiology

Corneal perforation is a complication of advanced keratitis and is severe and vision-threatening. When intense inflammation occurs, it leads to extensive tissue necrosis, which causes progressive thinning of the cornea. If this is left untreated, the thinness of the cornea can result in a full-thickness rupture of the cornea, allowing intraocular contents or fluid to leak from the eye. This condition comprises the structural integrity of the eye and poses a serious risk of permanent vision loss or even loss of the eye itself .⁶

Clinical features

Individuals who have corneal perforation typically experience sudden, sharp eye pain, abrupt vision loss, and possibly fluid leaking from the eye. Because of the lack of aqueous humour, examination may show a shallow or flat anterior chamber. Iris tissue may occasionally prolapse through the perforation site, which would further muddle the clinical picture. It is crucial to identify these symptoms as soon as possible.⁷

Emergency status

This symptom is an ocular emergency, therefore demands immediate medical attention. If there are delays in treatment, it can lead to infection spreading further inside the eye (endophthalmitis), further vision loss, and possible loss of the eye.

Treatment

In order to manage this, surgical intervention is needed, which usually involves a corneal patch graft for small perforations or a full-thickness corneal transplant for larger defects. As well as this, the infection would need to be controlled with the use of targeted antimicrobials, as it is critical to address the underlying cause. Supportive therapy, including cycloplegics, intraocular pressure control, and systemic medications, may also be needed to stabilise the eye and improve surgical outcomes.^6,7

Preventing complications

Early identification is necessary in preventing the dangerous consequences of keratitis; any eye that is red, painful, or visually impaired should be evaluated by a healthcare professional immediately so that treatment may begin on time. As incorrect usage of contact lenses is a leading cause of infectious keratitis, it is important that users practise good hygiene by avoiding overnight wear, using the necessary cleaning solutions and replacing lenses and storage cases on a regular basis. Additionally important are education and awareness: healthcare professionals must remain diligent in spotting early signs of keratitis, and individuals should be made aware of the dangers of postponing treatment and adopting bad eye care practices. Lastly, regular follow-up care guarantees appropriate healing, permits therapeutic modifications if needed, and aids in avoiding long-term harm or recurrence.^1,3

Conclusion

Keratitis, if not identified and treated promptly, can result in serious complications such as corneal scarring, vision loss, and corneal perforation. These outcomes may lead to permanent visual impairment and, in severe cases, the loss of the eye. The key to preventing these complications lies in early recognition, timely and appropriate treatment, and adopting preventive measures like good contact lens hygiene and regular eye check-ups. By staying vigilant and acting quickly at the first signs of keratitis, patients and healthcare providers can work together to protect and preserve vision.