Definition

The corneas are the clear and dome-shaped front layer of the eye. 

It acts as a protective barrier to allow only light to enter and keeps debris and germs out.

Anatomy

The cornea is located in front of the anterior chamber of the eye  which is filled with aqueous humour.

It is surrounded by the sclera, which is the white part of the eye. It plays an important role in vision by refracting light.

Layers of the Cornea

1. Epithelium: It is the outermost layer of the cornea. It is sensitive to pain and acts as a barrier. 

2. Bowman’s Layer: It is the tough layer of the cornea and provides structure to it.

3. Stroma: It is the thickest layer and helps in light refraction. 

4. Pre-Descemet’s Layer (PDL): It is an airtight barrier and the most recent discovery. 

5. Descemet’s Layer: It is a thin, stretchy and protective layer of cornea.

6. Endothelium: It is responsible for regulating the fluid balance in the cornea.

Function

The functions of cornea are: It

• Protects inner eye structures,
• refracts light, 
• absorbs oxygen, and 
• serves as the first line of defence against environmental hazards.

Common Disorders

The cornea can face the following disorders: 

Dry Eye: It occurs due to Insufficient tear fluid and causes pain and visual disruption. 

Acanthamoeba keratitis: It is caused due to infections in the cornea.

Keratitis: Caused due to inflammation due to infections or injuries. 

Corneal Dystrophies: It is a structural disease like keratoconus.

Treatments

1. Over-the-counter remedies for mild irritations. 

2. Ointments and eye drops for infections. 

3. Eye patches, contact lenses, amniotic membrane grafts. 

4. Laser surgeries such as LASIK (Laser-Assisted In Situ Keratomileusis), which is a surgical procedure to correct vision by reshaping the cornea of the eye.

5. Transplants for severe conditions.

Why is the Cornea transplant needed?

Patients with damaged cornea such as bulging outward, thinning, shearing or tearing, swelling, ulcers, and other complications from previous surgeries  basically need a cornea transplant to restore vision.

As per the Health Ministry, An estimated 2 lakh corneas are in demand each year in India and only 50% of the demand is met today.

Reasons for ease of the cornea donation:

1. The Cornea does not require blood supply unlike other organs and it can be harvested up to six hours after death.

2. Most hospitals can harvest the Cornea as its harvest process is easy.

3. Facial features of the deceased are not changed when harvesting cornea.

4. Corneas are not required for collecting evidence in legal cases.

Organ donation in India

Organ donation in India is under the regulation of the Transplantation of Human Organs and Tissues Act of 1994.

The act allows everyone to donate organs, regardless of age, caste, religion, or community. However, people over 18 years of age are preferred.

However, the eligibility for donation is determined based on the donor’s physical condition and not the age.

Read about the Transplantation of Human Organs and Tissues Act of 1994 and procedure here:

Transplantation of Human Organs and Tissues Act of 1994

PRACTICE QUESTION

Q.With reference to Cornea, consider the following statements:

1. It is the layer of the eye which allows only light to enter.

2. Cornea does not require blood supply unlike other organs.

3. Harvesting the Cornea is a difficult process.

How many of the statements given above are correct?

(a) Only one

(b) Only two

(c) All three

(d) None

Answer: b

Explanation:

Statement 1 is correct: 

Corneas is the clear and dome shaped front layer of the eye. 

It acts as a protective barrier to allow only light to enter and keeps debris and germs out.

Statement 2 is correct: 

The cornea is located in front of the anterior chamber of the eye  which is filled with aqueous humour.

It is surrounded by the sclera, which is the white part of the eye. It plays an important role in vision by refracting light.

Cornea does not require blood supply unlike other organs and it can be harvested up to six hours after death.

Statement 3 is incorrect: 

Most hospitals can harvest the Cornea as its harvest process is easy. And facial features of the deceased are not changed when harvesting cornea.