Corneal Transplantation — MCQs
Which of the following is the most devastating complication of cataract surgery?
Allograft rejection is an example of which type of hypersensitivity reaction?
Which keratometry reading is most accurate in post-LASIK eyes for IOL power calculation?
For transplantation, cornea is preserved in:
Which of the following is a known complication of vernal keratoconjunctivitis?
Maximum correction of myopia can be done by?
Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.
A 20-year-old male complains of repeated changes in glasses prescription. This is most likely caused by:
Which of the following statements about Fuchs' corneal dystrophy is true?
The golden period of eye donation is
Corneal Transplantation Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following is the most devastating complication of cataract surgery?
- A. Endophthalmitis (Correct Answer)
- B. Optic neuropathy
- C. Retinal detachment
- D. Vitreous loss
Explanation: ***Endophthalmitis*** - **Endophthalmitis** is a severe intraocular infection following cataract surgery that can rapidly lead to irreversible vision loss or even loss of the eye if not promptly treated. - It is considered the most devastating complication due to its acute onset and high potential for **permanent vision impairment**. *Optic neuropathy* - While optic neuropathy can cause visual loss, it is a less common direct complication of cataract surgery compared to endophthalmitis. - It typically results from processes like **ischemia** or severe orbital inflammation, which are rare occurrences immediately post-cataract surgery. *Retinal detachment* - **Retinal detachment** is a serious complication, but generally occurs at a lower rate than endophthalmitis and often has a better visual prognosis with timely surgical repair. - It is a known risk, particularly in patients with pre-existing **myopia** or prior posterior capsular rupture, but not necessarily the *most* devastating. *Vitreous loss* - **Vitreous loss** is an intraoperative complication that increases the risk of other issues like retinal detachment, cystoid macular edema, and endophthalmitis but is not, in itself, the most devastating. - Proper surgical technique and management during the procedure can mitigate many of its long-term sequelae.
Question 2: Allograft rejection is an example of which type of hypersensitivity reaction?
- A. Type IV hypersensitivity (Correct Answer)
- B. Type I hypersensitivity
- C. Type II hypersensitivity
- D. Type III hypersensitivity
Explanation: ***Delayed hypersensitivity*** - Allograft rejection primarily involves **T-cell mediated mechanisms** [1][3][5], characteristic of delayed hypersensitivity reactions [1][2]. - This type of reaction occurs days to weeks after exposure, leading to lymphocyte infiltration and tissue damage [1][4]. *Immediate hypersensitivity* - This type is mediated by **IgE antibodies** and occurs rapidly (within minutes) upon exposure to the allergen. - It is exemplified by **anaphylaxis**, which is not related to the T-cell-mediated rejection seen in allografts. *Swartzmans reaction* - This is a form of **opsonization and hypersensitivity** that results in systemic reactions due to previously sensitized antigen. - Unlike allograft rejection, it is not specifically related to transplant rejection mechanisms. *GVHD* - Graft-versus-host disease (GVHD) is a complication where the **graft attacks the host's tissues** as seen in hematopoietic stem cell transplants. - While related to immune responses, it is not the same as allograft rejection, which refers to the host's rejection of the graft. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 173-174. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 216-218. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 240. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 242. [5] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 240-241.
Question 3: Which keratometry reading is most accurate in post-LASIK eyes for IOL power calculation?
- A. Topography-derived K
- B. Total corneal power (Correct Answer)
- C. Manual keratometry
- D. Automated keratometry
Explanation: ***Total corneal power*** * After LASIK, the **anterior and posterior corneal curvatures** are altered, leading to discrepancies in standard keratometry readings. * **Total corneal power** methods, such as those derived from **corneal tomography** or **anterior segment OCT**, account for both surfaces, providing a more accurate estimation of the true refractive power. * *Topography-derived K* * While corneal topography is valuable for assessing the anterior corneal surface and identifying **irregular astigmatism**, it traditionally focuses on the anterior curvature and may not fully account for the altered **posterior corneal surface** after LASIK. * Standard topography-derived K values often rely on assumptions about the posterior-to-anterior corneal curvature ratio, which are invalid after refractive surgery. * *Manual keratometry* * Manual keratometry measures the **anterior corneal curvature** at a few discrete points and is highly susceptible to inaccuracies due to the post-LASIK changes in corneal shape. * It tends to **overestimate the corneal power** in eyes that have undergone myopic LASIK and **underestimate it** in hyperopic LASIK, leading to significant IOL power calculation errors. * *Automated keratometry* * Similar to manual keratometry, automated keratometry primarily measures the **anterior corneal surface** and relies on a fixed refractive index ratio that is no longer valid after corneal reshaping. * These devices generally provide **inaccurate keratometry readings** in post-refractive surgery eyes, contributing to refractive surprises after cataract surgery.
Question 4: For transplantation, cornea is preserved in:
- A. Modified MK medium (Correct Answer)
- B. Wet medium
- C. Glycerine medium
- D. All of the options
Explanation: ***Modified MK medium*** - The **Modified MK medium (McCarey-Kaufman medium)** is a widely accepted and effective **cold storage medium** for corneal preservation. - It contains nutrients (glutathione, adenosine), osmotic agents (dextran), and antibiotics to maintain corneal viability and transparency for up to **4-7 days** at 4°C. *Wet medium* - The term "wet medium" is **non-specific** and does not refer to a standard corneal preservation solution. - While cornea is stored in a liquid medium, this option lacks the specificity of established preservation techniques. *Glycerine medium* - **Glycerine** can be used for **tissue preservation** but is not the standard medium for routine corneal storage for transplantation. - Modern corneal preservation relies on specialized cold storage media that maintain endothelial cell viability, not glycerine-based preservation. *All of the options* - This option is incorrect because "Wet medium" is not a standard preservation term, and "Glycerine medium" is not the primary method for routine corneal storage for transplantation. - Only specific, scientifically validated preservation solutions like Modified MK medium are routinely used to ensure donor corneal viability.
Question 5: Which of the following is a known complication of vernal keratoconjunctivitis?
- A. Keratoconus (Correct Answer)
- B. Retinal detachment
- C. Vitreous hemorrhage
- D. Cataract
Explanation: ***Keratoconus*** - **Vernal keratoconjunctivitis (VKC)** is a chronic allergic eye condition associated with persistent eye rubbing, which can lead to thinning and bulging of the cornea, a condition known as **keratoconus**. - Long-term inflammation and mechanical stress from allergic reactions and *eye rubbing* contribute to the corneal structural changes seen in keratoconus. - This is the **most common and well-recognized complication** of VKC. *Cataract* - While cataracts can occur in VKC patients (particularly from **chronic topical steroid use** or severe disease with shield ulcers), they are **less common than keratoconus** as a direct complication. - Keratoconus remains the more characteristic and frequently encountered complication specifically associated with the mechanical trauma of eye rubbing in VKC. *Retinal detachment* - **Retinal detachment** is a condition where the retina separates from its underlying support tissues and is typically associated with trauma, high myopia, or diabetic retinopathy, not VKC. - VKC primarily affects the conjunctiva and cornea, and its inflammatory processes do not directly cause retinal detachment. *Vitreous hemorrhage* - **Vitreous hemorrhage** involves bleeding into the gel-like substance that fills the eye and is commonly caused by conditions like diabetic retinopathy or retinal tears, not VKC. - VKC does not involve the posterior segment of the eye in a way that would lead to vitreous hemorrhage.
Question 6: Maximum correction of myopia can be done by?
- A. Radial keratotomy
- B. LASIK (Correct Answer)
- C. Photorefractive keratectomy
- D. Orthokeratology
Explanation: ***LASIK*** - **LASIK (Laser-Assisted In Situ Keratomileusis)** allows for significant correction of high myopia by reshaping the cornea with an excimer laser. - It involves creating a **corneal flap** and then ablating tissue underneath, offering precise and stable vision correction for a wide range of refractive errors. - Among the given corneal refractive procedures, LASIK can correct myopia up to **-10 to -12 D**. *Radial keratotomy* - **Radial keratotomy (RK)** involves making radial incisions in the cornea to flatten it, primarily used for low to moderate myopia (up to -3 to -4 D). - It has a higher risk of **unpredictable outcomes**, induced astigmatism, and glare compared to modern laser procedures. *Photorefractive keratectomy* - **Photorefractive keratectomy (PRK)** involves direct ablation of the corneal surface without creating a flap, which is suitable for moderate myopia (up to -8 to -10 D). - While effective, PRK typically has a **longer recovery period** and more post-operative pain than LASIK. *Orthokeratology* - **Orthokeratology (Ortho-K)** uses specially designed rigid contact lenses worn overnight to temporarily reshape the cornea and correct myopia. - The effect is **temporary**, requiring continuous lens wear to maintain vision correction, and is generally limited to low to moderate myopia (up to -4 to -6 D).
Question 7: Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.
- A. Statements 1 & 2 are correct, 2 is not explaining 1 (Correct Answer)
- B. Statements 1 and 2 are correct and 2 is the correct explanation for 1
- C. Statements 1 and 2 are incorrect
- D. Statement 1 is incorrect
Explanation: ***Correct: Statements 1 & 2 are correct, 2 is not explaining 1*** **Analysis of Statement 1:** - A 59-year-old patient with **flaccid bullae** and **suprabasal acantholytic split** on histopathology is the classic presentation of **Pemphigus vulgaris** - The flaccid (easily ruptured) nature of bullae distinguishes it from tense bullae seen in bullous pemphigoid - The suprabasal location of the split (just above the basal layer) with acantholysis (loss of cell-to-cell adhesion) is pathognomonic - **Statement 1 is CORRECT** ✓ **Analysis of Statement 2:** - The **"row of tombstones" or "tombstone appearance"** is indeed a diagnostic histopathological feature of Pemphigus vulgaris - This appearance results from basal keratinocytes remaining attached to the basement membrane while suprabasal cells separate due to acantholysis - The intact basal cells standing upright resemble a row of tombstones - **Statement 2 is CORRECT** ✓ **Does Statement 2 explain Statement 1?** - Statement 2 describes a **histopathological appearance** (tombstone pattern) that is a **consequence** of the suprabasal split - However, it does NOT explain the **underlying cause** of the flaccid bullae or the suprabasal split - The true explanation involves **IgG autoantibodies against desmoglein 3 (and desmoglein 1)**, which attack intercellular adhesion structures (desmosomes), causing **acantholysis** - Therefore, **Statement 2 does NOT explain Statement 1** ✗ *Incorrect: Statement 2 is the correct explanation for Statement 1* - While both statements describe features of Pemphigus vulgaris, the tombstone appearance is a descriptive finding, not an explanatory mechanism *Incorrect: Statements 1 and 2 are incorrect* - Both statements are medically accurate descriptions of Pemphigus vulgaris features *Incorrect: Statement 1 is incorrect* - Statement 1 correctly describes the cardinal clinical and histopathological features of Pemphigus vulgaris
Question 8: A 20-year-old male complains of repeated changes in glasses prescription. This is most likely caused by:
- A. Keratoconus (Correct Answer)
- B. Cataract
- C. Glaucoma
- D. Pathological myopia
Explanation: ***Keratoconus*** - **Keratoconus** is a progressive disorder where the cornea thins and protrudes into a cone shape, leading to irregular astigmatism and frequent changes in glasses prescription. - This condition commonly presents in young adults and is characterized by **rapid, repeated changes** in both spherical and cylindrical components due to progressive corneal distortion. - The irregular corneal shape makes it difficult to achieve stable, satisfactory vision correction with glasses alone. *Cataract* - A **cataract** is a clouding of the eye's natural lens, which causes blurred vision, glare, and difficulty seeing at night. - While it can cause a "myopic shift" leading to prescription changes, it is more common in older individuals (>50 years) and the changes are typically slower and less frequent than in keratoconus. *Glaucoma* - **Glaucoma** is a group of eye conditions that damage the optic nerve, often due to high intraocular pressure, leading to peripheral vision loss and eventually blindness. - It does not cause changes in refractive error or require frequent updates to glasses prescriptions. - Visual changes are related to field defects, not refractive changes. *Pathological myopia* - **Pathological myopia** is a severe form of nearsightedness where the eye elongates excessively, leading to progressive increases in myopic refractive error. - While it can cause prescription changes in young adults, the progression is typically more **gradual and predictable** (mainly increasing spherical myopia) compared to the **rapid, irregular changes** seen in keratoconus. - Keratoconus is distinguished by frequent changes in astigmatism due to irregular corneal shape, whereas pathological myopia mainly affects spherical power.
Question 9: Which of the following statements about Fuchs' corneal dystrophy is true?
- A. Glaucoma is not a common association.
- B. It is a type of endothelial dystrophy (Correct Answer)
- C. It is characterized by bilateral involvement
- D. It primarily occurs in older adults
Explanation: ***It is a type of endothelial dystrophy*** - **Fuchs' endothelial corneal dystrophy (FECD)** is the **classic posterior/endothelial corneal dystrophy**, classified in the **IC3D classification system** as a primary endothelial dystrophy. - It involves **progressive loss of corneal endothelial cells** and formation of **guttata** (excrescences in Descemet's membrane), leading to endothelial dysfunction. - The dysfunctional endothelium cannot maintain corneal deturgescence, resulting in **corneal edema** and eventually **bullous keratopathy** in advanced cases. *It is characterized by bilateral involvement* - While Fuchs' dystrophy is **typically bilateral**, it can be **asymmetric** in presentation and progression. - Bilaterality is a common feature but not the most defining characteristic of the disease. *It primarily occurs in older adults* - Fuchs' dystrophy typically manifests in **middle age (40s-50s)** and progresses with age. - However, the condition has a **genetic basis** and cellular changes begin earlier than symptom onset. - Symptomatic disease is more common in older adults, but this doesn't define the disease entity itself. *Glaucoma is not a common association* - Studies have shown **increased prevalence of glaucoma** in patients with Fuchs' dystrophy compared to the general population. - The association may relate to **endothelial dysfunction** affecting aqueous outflow or shared risk factors. - This statement is **false** - glaucoma association has been documented.
Question 10: The golden period of eye donation is
- A. 24 hours
- B. 12 hours
- C. 18 hours
- D. 6 hours (Correct Answer)
Explanation: ***6 hours*** - The **golden period** for eye donation, specifically for the removal of the **cornea**, is ideally within **6 hours** of death. - This timeframe is critical to ensure the **viability and quality** of the corneal tissue for successful transplantation, as cellular degradation begins rapidly after cessation of circulation. *24 hours* - While some tissues can be recovered up to 24 hours post-mortem, the **cornea's viability** for transplantation significantly decreases after the initial 6-hour window. - Beyond 6 hours, the risk of **cellular damage** and reduced graft success rate increases considerably. *12 hours* - A 12-hour window is generally considered too long for optimal **corneal tissue viability**. - While tissue might still be recoverable, the **quality and success rate** of the transplant are significantly lower compared to donation within 6 hours. *18 hours* - An 18-hour period is far beyond the recommended timeframe for **corneal donation**. - At this point, the **cellular integrity** of the cornea is highly compromised, making it unsuitable for transplantation.
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