Overview

When it comes to treating keratitis, especially keratitis that doesn’t respond to medication, understanding surgical options is essential. Corneal transplantation and debridement are the 2 main forms of surgical treatment for this condition.

What is keratitis?

Keratitis, otherwise known as a corneal ulcer, is the irritation or inflammation of the cornea.¹

The cornea is the clear outermost layer of the eye, which helps focus light rays, allowing the brain to see a ‘picture’, which we know as eye sight.^1,2,3

Keratitis can form ulcers on the cornea, which can lead to corneal damage and an opaque cornea, stopping light from going through it and leading to corneal blindness.^1,2,3 

Symptoms of keratitis

Some common symptoms of keratitis that are seen initially:¹

• Eye pain
• Watery eyes
• Blurred vision
• Sensitivity to light
• The feeling of something in the eye

Types of keratitis

There are 2 main types of keratitis:

• Infectious keratitis
• Non-infectious keratitis

Infectious keratitis

Infectious keratitis, also known as microbial keratitis, is caused by infections, and there are 4 main types:^4,6

Bacterial keratitis – this is keratitis caused by a bacterial infection, and is often found in contact wearers, as bacteria can grow in contact lenses if they are not cleaned and stored properly, and if they are worn for long periods against medical advice.⁴

Fungal keratitis – this type of keratitis is less common and is caused by fungal infections.⁴ These fungal infections can occur with the improper use of contact lenses and steroid drops or injury to the eye from things like branches or plants.⁴

Viral keratitis – Keratitis can be caused by a viral infection, such as a common cold, chicken pox, and herpes simplex virus (cold sore)^.4 Viral infections can spread through touching the eyes, for example, touching a cold sore, then touching your eyes.⁴ Repeated viral keratitis can be triggered by stress and an impaired immune system, caused by the herpes simplex virus 4.

Parasitic keratitis – This type of keratitis can be caused by a parasite called Acanthamoeba, and swimming while wearing contact lenses can increase the risk of this type of keratitis.⁴

Non-infectious keratitis

Non-infectious keratitis can be caused by a few things:^3,4

Injury to the eye, such as scratches or scrapes to the cornea, can cause non-infectious keratitis or even lead to infectious keratitis.⁴

Dry eyes can be caused by dry eye syndrome, where the eyes are not able to produce tears, or eyelid disorders that stop the eye from closing properly, causing the eye to dry out and leading to the development of keratitis, as there is no protective layer of tears to stop corneal irritation.⁴

Photokeratitis is a type of keratitis caused by intense UV light, from things such as the sun, tanning beds, and looking at a solar eclipse without protective eye wear.^3,4

Treatment of keratitis

Indications for surgical interventions in keratitis:

Surgical treatment is considered when there is a lot of inflammation in the eye, medication is not working, there is a risk of vision loss, and the integrity of the eye structure is decreasing^4,5. The opacity of the cornea and the level of corneal scarring are also taken into consideration when deciding if surgery is the right treatment.^1,11,12

To understand each surgery, we must understand the structure of the cornea:¹⁵

There are 2 main types of surgical treatment for keratitis:

• Corneal debridement
• Corneal transplantation

Corneal debridement

Erasmus Darwin was the first in English literature to suggest corneal debridement⁶. He explained this as “[An] idea is with a sharp knife, to shave or pare off the external part of the opaque cornea, till it becomes transparent, like scraping ivory or horn quite thin, and try if it would become opaque again.”^6,7

Corneal debridement is used to treat infectious keratitis, where a blade is used to remove the ulcer from the cornea by scraping the ulcer gently but firmly.⁶ The purpose of this surgery is to help remove unhealthy tissue, i.e., the ulcer on the surface of the cornea, allowing it to heal, improving vision, and comfort.⁶

This procedure is done under topical anaesthetic, which is a medication applied to the eye to numb the area and stop any pain or feeling in the area.^6,8 

Advantages and limitations

The advantages of this procedure are that it is minimally invasive, so healing is easier and can be performed in an outpatient setting, as only a topical anaesthetic is required.⁶

While this is an advantageous surgery, it does not address the deeper issues, like damage to the structural integrity of the eye, which may require additional treatments to address.⁶

Corneal transplantation

Corneal transplantation, also known as keratoplasty, is an operation done to remove the damaged and unhealthy parts of the cornea and replace them with healthy donor tissue, which is tissue that has been donated from an organ donor.^10,11 This is done to improve vision and eye pain caused by conditions like keratitis.^10,11

This surgery is done for more moderate to severe corneal damage.

There are a few main types of transplantation:

• Penetrating keratoplasty (PK)
• Anterior lamellar keratoplasty (ALK) 
• Endothelial keratoplasty (EK) 

Penetrating Keratoplasty (PK)

PK involves a surgeon cutting and replacing all the corneal layers with a healthy donor cornea.¹² This is done when the majority of the cornea is opaque and damaged.¹² A transplant can last decades with proper care as advised by a health professional.¹¹

While PK is effective, there is a long recovery time, which can sometimes take years to achieve the best-corrected vision, and there is a chance of astigmatism error, which may require wearing contact lenses.¹¹

Anterior Lamellar Keratoplasty (ALK)

ALK is a surgery that removes the damaged tissue from the front layers of the cornea, particularly the endothelium and the stroma, which is a layer that is responsible for focusing light in the eye.^11,13,14

How deep the corneal damage is determines what EK surgery is suited for you.¹³

There are 2 types of ALK.^11,13

Superficial Anterior Lamellar Keratoplasty (SALK)

In SALK, only the front of the cornea is replaced, leaving the endothelium and stroma alone.^11,13

Deep Anterior Lamellar Keratoplasty (DALK)

DALK is used when the damage to the eye is deeper, so a portion of the stroma is removed, leaving the endothelium and Descemet's membrane alone, and replaced with healthy donor tissue.^11,13

This technique has a lower chance of donor rejection as the wound is smaller.¹¹ 

Endothelial Keratoplasty (EK)

EK involves removing damaged tissue from the back corneal layer, which is then replaced with healthy donor tissue.^11,12 The layers removed include a layer of tissue called the endothelium and the Descemet membrane, which is a layer attached to the endothelium.¹¹

There are 2 types of EK:¹³

Descemet Stripping Automated Endothelial Keratoplasty (DSAEK)

DSAEK is the first type of EK where a portion of the cornea, particularly the Descemet membrane and endothelium, is replaced with healthy donor tissue.¹¹

The healing time for this surgery is fairly quick in comparison to DALK and PK.¹¹

Descemet Membrane Endothelial Keratoplasty (DMEK)

The second type of EK is DMEK, where, like DSAEK, a portion of the cornea is removed and replaced with healthy donor tissue, but the layer of tissue is much thinner and therefore more fragile.^11,13

DMEK has the fastest healing time out of all of the corneal transplant surgeries, and the chances of the transplant being rejected by the body are lower, as the size of the tissue used is small.¹¹

Though there are a variety of different surgical options for the treatment of keratitis, which surgery used depends on the individual and the severity of the damage to the eye, where it is located, and how the individual responds.

Summary

Keratitis is a condition of the eye that causes inflammation of the cornea and ulcers, leading to an opaque cornea, which causes symptoms like corneal blindness and the feeling of something in the eye. There are 2 main types of keratitis: infectious and non-infectious. Infectious keratitis can be caused by a range of microorganisms like fungi, bacteria, viruses, and parasites, while non-infectious keratitis can be caused by poor contact hygiene or injury to the eyes.

Surgery is done when an individual is not responding to medication or if vision is at risk. 2 main types of corneal surgery that can be used for keratitis: corneal debridement and corneal transplantation. Corneal debridement is for less severe cases, while corneal transplantation is used to replace the damaged tissue with healthy donor tissue. There are 3 main types of corneal transplantation: penetrating keratoplasty (PK), anterior lamellar keratoplasty (ALK), which has 2 types: deep anterior lamellar keratoplasty (DALK) and superficial anterior lamellar keratoplasty (SALK) and endothelial keratoplasty (EK), which also has 2 types: Descemet stripping automated endothelial keratoplasty (DSAEK) and Descemet membrane endothelial keratoplasty (DMEK). The type of surgery used is dependent on the individual and the condition of the eyes.