In eye donation, which one of the following parts of donor’s eye is utilised ?

1. Anatomy of the Human Eye (basic)

To understand ophthalmic surgery, we must first master the biological camera: the human eye. The eye is a nearly spherical organ, roughly 2.3 cm in diameter, designed to capture light and convert it into electrical signals Science, Chapter 10, p.161. Light first encounters the cornea, a thin, transparent membrane forming a bulge at the front. Interestingly, while we often credit the lens for focusing, most of the refraction (bending) of light actually occurs at the outer surface of the cornea. In the context of medical miracles, this is the specific tissue harvested during eye donation to restore sight to those with corneal blindness. Behind the cornea lies the iris, a dark muscular diaphragm that gives the eye its color. The iris acts like a camera's aperture, adjusting the size of the pupil to regulate how much light enters Science, Chapter 10, p.161. Just behind the pupil sits the crystalline lens. Made of a transparent, jelly-like fibrous material, the lens is not rigid; its curvature is dynamically adjusted by the ciliary muscles. This adjustment, known as accommodation, allows the eye to shift focus between a distant horizon and a nearby book by changing the lens's focal length Science, Chapter 10, p.162. Finally, the light is focused onto the retina, a delicate, light-sensitive layer at the back of the eye that serves as the 'screen' where images are formed Science, Chapter 10, p.170. Understanding these structures is vital because modern surgical technologies, such as LASIK or cataract surgery, work by precisely modifying these specific anatomical components to correct vision.

Structure	Primary Function	Key Characteristic
Cornea	Major light refraction	Transparent front bulge; used in transplants
Iris	Light regulation	Muscular diaphragm; controls pupil size
Ciliary Muscles	Focusing (Accommodation)	Changes the curvature of the crystalline lens
Retina	Image formation	Light-sensitive screen at the back of the eyeball

Sources: Science (NCERT 2025 ed.), Chapter 10: The Human Eye and the Colourful World, p.161; Science (NCERT 2025 ed.), Chapter 10: The Human Eye and the Colourful World, p.162; Science (NCERT 2025 ed.), Chapter 10: The Human Eye and the Colourful World, p.170

2. Vision Defects and Optical Correction (basic)

To understand how we correct vision, we must first understand the Power of Accommodation. This is the eye's remarkable ability to adjust its focal length using the ciliary muscles so that images of both near and distant objects fall precisely on the retina Science, Class X (NCERT 2025 ed.), Chapter 10, p. 170. For a healthy young adult, the near point (the closest distance for clear vision without strain) is about 25 cm, while the far point is at infinity. When the eye lens cannot properly focus these images due to changes in its curvature or the length of the eyeball, we develop refractive defects.

The two most common refractive errors are Myopia and Hypermetropia. In Myopia, the eye is too 'strong' or the eyeball too long, causing light to converge in front of the retina. Conversely, in Hypermetropia, the eye is too 'weak' or the eyeball too short, causing light to focus behind the retina Science, Class X (NCERT 2025 ed.), Chapter 10, p. 163. A third condition, Presbyopia, arises naturally with age as the ciliary muscles weaken and the eye lens loses its flexibility, making it difficult to see nearby objects clearly.

Feature	Myopia (Near-sightedness)	Hypermetropia (Far-sightedness)
Vision Capability	Can see nearby clearly; distant is blurred.	Can see distant clearly; nearby is blurred.
Image Formation	In front of the retina.	Behind the retina.
Anatomical Cause	Excessive curvature of the lens or elongated eyeball.	Focal length is too long or eyeball is too small.
Optical Correction	Concave lens (Diverging) to push the image back.	Convex lens (Convergent) to pull the image forward.

Sources: Science, Class X (NCERT 2025 ed.), Chapter 10: The Human Eye and the Colourful World, p.162; Science, Class X (NCERT 2025 ed.), Chapter 10: The Human Eye and the Colourful World, p.163; Science, Class X (NCERT 2025 ed.), Chapter 10: The Human Eye and the Colourful World, p.170

3. Legal Framework: Organ & Tissue Transplantation (intermediate)

In the realm of medical ethics and law, organ and tissue transplantation is governed by a robust framework designed to ensure that the gift of life is handled with dignity and transparency. At its core, organ donation is a voluntary act where an individual (the donor) provides an organ or tissue to replace a failing one in a recipient Science, class X (NCERT 2025 ed.), Life Processes, p.98. In India, the primary legislation governing this process is the Transplantation of Human Organs and Tissues Act (THOTA), 1994. This law was enacted to provide a system for the removal, storage, and transplantation of human organs and tissues for therapeutic purposes and, crucially, to prevent commercial dealings in human organs.

One of the most important aspects of this legal framework is the definition of consent. Donation can only occur with the explicit consent of the donor (while alive) or their family members (after death). A significant feature of this system is its inclusivity: anyone, regardless of age or gender, can become a donor Science, class X (NCERT 2025 ed.), Life Processes, p.98. In the context of ophthalmic surgery, the focus is often on tissue transplantation, specifically the cornea. The cornea is the transparent, bulging front layer of the eye that provides the majority of the eye's refractive power Science, class X (NCERT 2025 ed.), The Human Eye and the Colourful World, p.161. Unlike major organs like the heart or lungs, which typically require "brain stem death" for retrieval, corneal tissue can be retrieved after cardiac death, making it one of the most common and successful types of transplants.

Feature	Organ Donation (e.g., Heart, Liver)	Tissue Donation (e.g., Cornea, Bone)
Retrieval Window	Very short; usually requires brain death with heart still beating.	Longer; can often be retrieved several hours after cardiac death.
Impact	Saves a life from organ failure.	Restores function or transforms quality of life (e.g., sight).
Legal Basis	THOTA, 1994 (as amended).	THOTA, 1994 (as amended).

Sources: Science, class X (NCERT 2025 ed.), Life Processes, p.98; Science, class X (NCERT 2025 ed.), The Human Eye and the Colourful World, p.161

4. Public Health: National Blindness Control (intermediate)

To understand the National Blindness Control efforts in India, we must first look at the scale of the challenge. Globally, approximately 35 million people in the developing world suffer from blindness, and a significant portion of these cases are actually treatable Science, Class X (NCERT 2025 ed.), Chapter 10, p.164. Within this group, corneal blindness stands out as a critical public health priority because it is reversible through a surgical procedure known as corneal transplantation (or Keratoplasty). In India, it is estimated that 4.5 million people suffer from corneal blindness, and heartbreakingly, about 60% of these are children below the age of 12 Science, Class X (NCERT 2025 ed.), Chapter 10, p.164.

The core of this surgical solution is eye donation. A common misconception is that the entire eyeball is transplanted; in reality, only the cornea — the thin, transparent, dome-shaped front layer of the eye — is utilized for transplantation Science, Class X (NCERT 2025 ed.), Chapter 10, p.161. This tissue is vital because it acts as the eye's primary 'window,' providing most of the eye's refractive power to focus light. When the cornea becomes opaque due to injury, infection, or malnutrition (like Vitamin A deficiency), vision is lost, but the underlying neural machinery (the retina and optic nerve) often remains healthy, making the patient a perfect candidate for a 'window replacement' via a donor cornea.

From a public health management perspective, the government has integrated these efforts into broader digital frameworks. The National Digital Health Mission (NDHM) and the National Digital Health Blueprint aim to streamline health records, which can assist in the efficient matching of donors to recipients Indian Economy, Nitin Singhania (ed 2nd 2021-22), Sustainable Development and Climate Change, p.622. Furthermore, inclusive education initiatives like PM eVIDYA provide specialized digital content for the visually impaired, ensuring that those currently living with blindness are not excluded from the nation's progress while they await surgical intervention Indian Economy, Nitin Singhania (ed 2nd 2021-22), Sustainable Development and Climate Change, p.622.

Feature	Corneal Transplantation Details
Tissue Used	Only the Cornea (the transparent front layer)
Donor Eligibility	Any age or sex; even those with diabetes or hypertension
Time Sensitivity	Eyes must be removed within 4-6 hours after death
Impact	One donor can potentially restore sight to two individuals

Sources: Science, Class X (NCERT 2025 ed.), Chapter 10: The Human Eye and the Colourful World, p.161, 164; Indian Economy, Nitin Singhania (ed 2nd 2021-22), Sustainable Development and Climate Change, p.622

5. The Science of Immune Privilege & Avascularity (exam-level)

In the world of medicine, the cornea is often called a "miracle tissue." To understand why, we must look at its unique biological design. The cornea is the transparent, bulging layer at the very front of the eyeball that handles most of the eye's refractive power Science, Class X (NCERT 2025 ed.), Chapter 10, p. 161. However, to stay perfectly clear and let light pass through without obstruction, it must be avascular—meaning it possesses no blood vessels. While most tissues in your body are packed with capillaries to deliver nutrients, the cornea receives its oxygen directly from the air and its nutrients from the aqueous humor behind it.

This lack of blood supply leads to a fascinating phenomenon called Immune Privilege. Usually, when a foreign organ (like a kidney or heart) is transplanted, the recipient's immune system detects it via the bloodstream and attacks it, leading to "organ rejection." Because the cornea has no blood vessels, the body's immune "sentries" (white blood cells) cannot easily reach or recognize the donor tissue as foreign. This is why corneal transplants have a much higher success rate compared to other organs and often do not require the same intensive tissue-matching or lifelong immunosuppressants.

This biological advantage is the reason why corneal transplantation is a primary solution for the 4.5 million people globally suffering from corneal blindness Science, Class X (NCERT 2025 ed.), Chapter 10, p. 164. Because it is a robust, hardy tissue protected by its immune-privileged status, it can be harvested up to 4-6 hours after a donor's death and successfully restore sight to others Science, Class X (NCERT 2025 ed.), Chapter 10, p. 165.

Feature	Vascular Tissue (e.g., Skin/Kidney)	Avascular Tissue (Cornea)
Blood Supply	Rich capillary network	None (Avascular)
Immune Response	Rapid detection of foreign antigens	Delayed or absent (Immune Privilege)
Transplant Success	Requires complex tissue matching	High success due to low rejection risk

Sources: Science, Class X (NCERT 2025 ed.), Chapter 10: The Human Eye and the Colourful World, p.161; Science, Class X (NCERT 2025 ed.), Chapter 10: The Human Eye and the Colourful World, p.164; Science, Class X (NCERT 2025 ed.), Chapter 10: The Human Eye and the Colourful World, p.165

6. Keratoplasty and Eye Banking Procedures (exam-level)

Keratoplasty, commonly known as corneal transplantation, is a surgical procedure where a damaged or diseased cornea is replaced by healthy corneal tissue from a deceased donor. The cornea is the thin, transparent front layer of the eye that covers the iris and pupil; it acts as the eye's primary lens, providing most of its refractive power to focus light Science, Class X (NCERT 2025 ed.), Chapter 10, p.161. When the cornea becomes opaque due to injury, infection, or malnutrition, it leads to corneal blindness. This condition is uniquely reversible because, unlike many other forms of blindness, it can be cured by simply replacing the "window" of the eye.

The success of these surgeries relies on a robust Eye Banking system. Eye banks are responsible for the collection, evaluation, and distribution of donated eyes. Time is of the essence in this process: eyes must be harvested within 4 to 6 hours after death Science, Class X (NCERT 2025 ed.), Chapter 10, p.165. The removal procedure is brief (10–15 minutes) and does not cause any facial disfigurement, allowing for traditional funeral rites to proceed normally. Interestingly, one donor can often restore sight to multiple individuals because modern techniques allow the corneal tissue to be layered or split for different recipients.

In terms of eligibility, eye donation is highly inclusive but governed by strict safety protocols. While age, sex, or common vision defects (like wearing spectacles or having had cataract surgery) do not prevent someone from donating, certain systemic diseases are absolute contraindications to ensure recipient safety.

Category	Eligible Donors	Ineligible Donors (Contraindications)
General Health	People of any age, sex, or blood group.	Those with AIDS, Hepatitis B or C, Rabies, or Tetanus.
Vision History	Users of spectacles or those with past cataract surgery.	Those with Acute Leukaemia or certain brain infections (Meningitis/Encephalitis).
Cause of Death	Most causes of death (e.g., cardiac arrest, accidents).	Deaths caused by Cholera or other highly infectious systemic diseases.

Sources: Science, Class X (NCERT 2025 ed.), Chapter 10: The Human Eye and the Colourful World, p.161; Science, Class X (NCERT 2025 ed.), Chapter 10: The Human Eye and the Colourful World, p.165

7. Solving the Original PYQ (exam-level)

You have just mastered the anatomical building blocks of the human eye, and this question is the perfect application of that knowledge. While the term "eye donation" is commonly used, it is a technical misnomer; in reality, medical science focuses on the cornea—the transparent, dome-shaped window covering the front of the eye. As you learned in Science, class X (NCERT 2025 ed.), the cornea is responsible for the majority of the eye's refractive power. Because it is avascular (lacking blood vessels), it has a remarkably high success rate in transplants, as there is a lower risk of the recipient's immune system rejecting the donor tissue.

To arrive at the correct answer, (C) Cornea, you must navigate the functional roles of the other components. The Iris and Lens are internal structures; while the lens is frequently replaced during cataract surgery, doctors use synthetic intraocular lenses rather than donor tissue. The most common trap here is the Retina; however, the retina is actually a complex layer of neural tissue connected directly to the brain via the optic nerve. Currently, neural transplantation of the retina is not possible in standard medical practice, making the cornea the only viable part listed for traditional restorative donation.