Refractive Surgery — MCQs
Which of the following is NOT an approach followed in revised NPCB cataract surgeries?
Which of the following is the most devastating complication of cataract surgery?
Postoperative complications of cataract surgery are all except?
Which keratometry reading is most accurate in post-LASIK eyes for IOL power calculation?
A 20-year-old male complains of repeated changes in glasses prescription. This is most likely caused by:
A lady wants LASIK surgery for her daughter and asks for your opinion. All the following are suitable for performing LASIK surgery except:
Shortening of 2 mm of axial length of the eyeball causes?
Which of the following statements about congenital glaucoma is incorrect?
What does a visual acuity test primarily assess?
What surgery is used to treat posterior capsular opacification?
Refractive Surgery Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following is NOT an approach followed in revised NPCB cataract surgeries?
- A. Mobile surgical camps
- B. Consistent follow-up care
- C. Fixed-site surgical treatment alone (excluding camps) (Correct Answer)
- D. Standardized distribution of resources
Explanation: ***Fixed-site surgical treatment alone (excluding camps)*** - The revised **National Programme for Control of Blindness and Visual Impairment (NPCBVI)** adopts a **multi-pronged integrated approach** combining both fixed-site facilities and mobile outreach camps. - Relying **exclusively on fixed-site treatment** without mobile camps is **not the strategy** of the revised program, as this would limit access for rural and underserved populations. - The program emphasizes **both institutional capacity** (fixed sites at district hospitals and eye hospitals) **and community outreach** (mobile surgical camps) working together. *Mobile surgical camps* - **Mobile camps** are a crucial strategy in the revised NPCB to reach underserved populations in rural and remote areas. - They enhance **accessibility to care** and increase surgical coverage, particularly in areas without nearby fixed facilities. - Camps are conducted with **quality standards** and linked to fixed sites for follow-up care. *Consistent follow-up care* - **Comprehensive follow-up** is a cornerstone of the revised NPCB to ensure positive outcomes and address complications. - This includes **post-operative care protocols** at both camp and fixed-site surgeries to reduce morbidity. - Follow-up mechanisms help achieve the program's goal of **quality cataract surgery outcomes**. *Standardized distribution of resources* - The revised NPCB promotes **equitable and efficient allocation** of resources to ensure quality cataract services across regions. - This includes distribution of **equipment, consumables, trained personnel, and funding** based on need and surgical load. - Resource standardization helps maintain **quality benchmarks** across different service delivery models.
Question 2: 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 3: Postoperative complications of cataract surgery are all except?
- A. Endophthalmitis
- B. Glaucoma
- C. Scleritis (Correct Answer)
- D. After cataract
Explanation: ***Scleritis*** - **Scleritis** is an inflammatory condition of the sclera, which is the white outer layer of the eye, and is generally not a direct postoperative complication of cataract surgery. - While it can occur in patients with systemic inflammatory diseases, it is not causally linked to cataract surgery itself. *Endophthalmitis* - **Endophthalmitis** is a severe infection of the intraocular fluids (vitreous and aqueous humor) and tissues, representing a rare but devastating complication of cataract surgery. - It typically presents with rapidly progressive vision loss, pain, and hypopyon (pus in the anterior chamber) within days to weeks post-surgery. *Glaucoma* - **Glaucoma** can develop or worsen after cataract surgery due to various mechanisms, such as inflammation leading to trabecular meshwork dysfunction, pupillary block, or retained lens material. - Postoperative intraocular pressure (IOP) elevation can result in optic nerve damage if not promptly managed. *After cataract* - **After cataract**, also known as **posterior capsule opacification (PCO)**, is the most common long-term complication of cataract surgery. - It occurs when residual lens epithelial cells proliferate and migrate onto the posterior lens capsule, causing blurring of vision months to years after surgery, and is typically treated with Nd:YAG laser capsulotomy.
Question 4: 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 5: 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 6: A lady wants LASIK surgery for her daughter and asks for your opinion. All the following are suitable for performing LASIK surgery except:
- A. Stable refraction for 1 year
- B. Corneal thickness of 600 microns
- C. Myopia of 4 Diopters
- D. Age of 15 years (Correct Answer)
Explanation: ***Age of 15 years*** - LASIK surgery is generally not recommended for individuals under the age of 18-21 years because their **refractive error** may still be changing. - **Refractive stability** is a critical prerequisite to ensure a lasting surgical outcome. *Myopia of 4 Diopters* - This level of **myopia** (nearsightedness) typically falls within the treatable range for LASIK, which can correct moderate to high degrees of refractive error. - LASIK is highly effective for reducing or eliminating dependence on **glasses or contact lenses** for this range. *Stable refraction for 1 year* - **Refractive stability** is an essential criterion for LASIK candidacy, indicating that the patient's prescription has not significantly changed over a specific period. - This ensures that the surgical correction will be durable and accurate, preventing the need for future enhancements due to progression of refractive error. *Corneal thickness of 600 microns* - A **corneal thickness** of 600 microns is considered adequate for LASIK, as it allows for sufficient residual stromal bed thickness after ablation. - The minimum required **residual stromal bed thickness** is typically around 250-300 microns to maintain corneal integrity and prevent ectasia.
Question 7: Shortening of 2 mm of axial length of the eyeball causes?
- A. 3D myopia
- B. 2D myopia
- C. 6D hypermetropia (Correct Answer)
- D. 1D hypermetropia
Explanation: ***6D hypermetropia*** - A 1 mm shortening of the **axial length** of the eyeball typically results in approximately **3 diopters** of hypermetropia. - Therefore, a 2 mm shortening would cause **6 diopters** (2 mm x 3 D/mm) of hypermetropia. *3D myopia* - Myopia (nearsightedness) is caused by an **eyeball that is too long** or a cornea that is too steeply curved, not by a shortened axial length. - A 2 mm shortening would cause **hypermetropia** (farsightedness), not myopia. *2D myopia* - This option incorrectly identifies both the **type of refractive error** (myopia instead of hypermetropia) and the magnitude of the change. - Shortening of the axial length makes the eye effectively **farsighted**, not nearsighted. *1D hypermetropia* - While reflecting the correct type of refractive error (hypermetropia), the **magnitude is incorrect**. - A 1 mm change in axial length results in about 3 diopters, so 2 mm would be **6 diopters**, not 1 diopter.
Question 8: Which of the following statements about congenital glaucoma is incorrect?
- A. Thin and blue sclera seen
- B. Anterior chamber is shallow (Correct Answer)
- C. Photophobia is most common symptom
- D. Haab's Striae may be seen
Explanation: ***Anterior chamber is shallow*** - In congenital glaucoma, the **anterior chamber depth is typically normal or deep**, not shallow. - A shallow anterior chamber is more characteristic of **angle-closure glaucoma**, which is mechanistically different. - This makes the statement incorrect, as congenital glaucoma is associated with a **deep anterior chamber** due to globe enlargement. *Photophobia is most common symptom* - **Photophobia** (sensitivity to light) is indeed one of the classic presenting symptoms in congenital glaucoma. - It forms part of the classic triad: **photophobia, epiphora (tearing), and blepharospasm**. - This occurs due to **increased intraocular pressure** causing corneal edema and irritation. *Thin and blue sclera seen* - The **sclera** can appear thin and blue due to **buphthalmos** (enlargement of the eye) and stretching of the globe. - The stretching allows the underlying **uveal tissue** to show through, giving the characteristic blue appearance. - This is a direct consequence of elevated intraocular pressure in a developing eye. *Haab's Striae may be seen* - **Haab's striae** are **Descemet's membrane tears** that are pathognomonic of congenital glaucoma. - These horizontal or curvilinear breaks occur due to stretching of the cornea from **elevated intraocular pressure**. - They appear as visible linear opacities on corneal examination.
Question 9: What does a visual acuity test primarily assess?
- A. Ability to perceive light
- B. Ability to differentiate colors
- C. Ability to recognize shapes and details (Correct Answer)
- D. Ability to detect contrast
Explanation: ***Ability to recognize shapes and details*** - A visual acuity test, typically using a **Snellen chart**, measures the sharpness of vision, specifically the ability to discern letters or symbols at a given distance. - It assesses the eye's capacity to resolve fine **spatial detail**, which is crucial for tasks like reading and recognizing faces. - This is the fundamental definition of visual acuity and what these tests are specifically designed to measure. *Ability to perceive light* - This refers to **light perception (LP)**, the most basic form of vision, indicating whether a person can detect the presence or absence of light. - While essential for vision, it is a much simpler function than what visual acuity tests measure and is assessed separately. *Ability to differentiate colors* - This is assessed by **color vision tests**, such as the Ishihara plates, which evaluate the function of cone photoreceptors. - It specifically checks for **color blindness** (e.g., red-green or blue-yellow deficiencies) and is distinct from the sharpness of vision. *Ability to detect contrast* - This is measured by **contrast sensitivity tests**, which evaluate the ability to distinguish objects from their background at various contrast levels. - While related to overall visual quality, it is a different aspect of vision than the ability to recognize fine details at high contrast.
Question 10: What surgery is used to treat posterior capsular opacification?
- A. Laser Posterior Capsulotomy (Correct Answer)
- B. Extracapsular cataract Extraction
- C. Phacoemulsification
- D. Lensectomy
Explanation: **Explanation:** **Posterior Capsular Opacification (PCO)**, often called a "secondary cataract," is the most common late complication of cataract surgery. It occurs due to the proliferation and migration of residual lens epithelial cells across the posterior capsule, leading to decreased visual acuity and glare. **Why Option A is Correct:** The gold standard treatment for PCO is **Nd:YAG Laser Posterior Capsulotomy**. This non-invasive procedure uses a photodisruptive laser to create a small opening in the central axis of the opacified posterior capsule. This clears the visual axis and restores vision without the need for surgical incisions. **Why Other Options are Incorrect:** * **B & C (ECCE and Phacoemulsification):** These are primary surgical techniques used to *remove* a cataractous lens. They are not used to treat complications involving the capsule that remains after the initial surgery. * **D (Lensectomy):** This involves the complete removal of the lens and its capsule (often via the pars plana). It is typically reserved for complex cases like subluxated lenses or pediatric cataracts, not routine PCO. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Signs:** Look for **Elschnig pearls** (vacuolated cells) or **Soemmering’s ring** on slit-lamp examination. * **Laser Type:** Nd:YAG (Neodymium-doped Yttrium Aluminum Garnet) is a **solid-state, pulsed** laser. * **Mechanism:** It works via **photodisruption** (plasma formation). * **Complications of YAG Capsulotomy:** The most common high-yield complication is a transient **rise in Intraocular Pressure (IOP)**. Other risks include cystoid macular edema (CME) and retinal detachment.
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