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?
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:
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?
Examination of the vitreous is best performed by which of the following methods?
Contracted socket occurs because of all the following except?
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: 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: 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 5: 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 6: 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 7: 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 8: 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.
Question 9: Examination of the vitreous is best performed by which of the following methods?
- A. Direct ophthalmoscope
- B. Indirect ophthalmoscope (Correct Answer)
- C. Slit-lamp with a contact lens
- D. Oblique illumination
Explanation: **Explanation:** The examination of the vitreous requires a technique that provides a wide field of view, excellent illumination, and stereopsis (depth perception) to visualize the transparent gel and any associated pathologies. **Why Indirect Ophthalmoscopy is the Correct Answer:** The **Indirect Ophthalmoscope** is the gold standard for a comprehensive evaluation of the vitreous cavity. It utilizes a strong light source and a condensing lens (typically 20D) to provide a **wide-angled, stereoscopic, and bright image**. This allows the examiner to visualize the vitreous from the anterior hyaloid face all the way to the peripheral retina (ora serrata), making it superior for detecting vitreous opacities, hemorrhages, or membranes. **Analysis of Incorrect Options:** * **A. Direct Ophthalmoscope:** While it provides high magnification, it lacks stereopsis and has a very narrow field of view (about 5-10 degrees), making it ineffective for surveying the three-dimensional vitreous volume. * **C. Slit-lamp with a contact lens:** While a slit-lamp with a Hruby lens or a Goldmann 3-mirror lens provides excellent detail of the posterior vitreous and vitreoretinal interface, the **Indirect Ophthalmoscope** remains the primary and best method for a global, comprehensive examination of the entire vitreous body. * **D. Oblique illumination:** This is a basic technique used primarily for the anterior segment (cornea, iris, lens) and cannot penetrate or visualize the vitreous cavity effectively. **High-Yield Clinical Pearls for NEET-PG:** * **Shafer’s Sign:** The presence of "tobacco dust" (RPE cells) in the anterior vitreous on slit-lamp exam is a pathognomonic sign of a retinal tear. * **Weiss Ring:** A ring-shaped opacity in the vitreous indicating a posterior vitreous detachment (PVD). * For the **extreme periphery** of the vitreous/retina, indirect ophthalmoscopy combined with **scleral indentation** is the technique of choice.
Question 10: Contracted socket occurs because of all the following except?
- A. Chronic low-grade infection
- B. Chronic mechanical irritation
- C. Irradiation
- D. Loss of orbital fatty tissue during enucleation (Correct Answer)
Explanation: ### Explanation A **contracted socket** is a condition where the orbital cavity shrinks, leading to a reduction in the surface area of the conjunctival fornices. This makes it difficult or impossible to retain a prosthetic eye. **1. Why "Loss of orbital fatty tissue" is the correct answer:** Loss of orbital fat during enucleation leads to **Enophthalmos** (a sunken appearance) and a "deep superior sulcus" deformity, but it does **not** cause a contracted socket. While the volume of the orbit is reduced, the mucosal lining (conjunctiva) remains intact. A contracted socket is primarily a failure of the **conjunctival surface area**, not just a loss of posterior orbital volume. **2. Analysis of Incorrect Options:** * **Chronic low-grade infection:** Persistent inflammation (e.g., chronic discharge) leads to sub-conjunctival fibrosis and scarring, which gradually pulls the fornices inward, causing contraction. * **Chronic mechanical irritation:** An ill-fitting prosthesis or a rough-surfaced artificial eye acts as a chronic irritant, triggering a cicatricial (scarring) response in the conjunctiva. * **Irradiation:** Radiotherapy for orbital tumors (like Retinoblastoma) causes endarteritis obliterans and tissue ischemia, leading to severe fibrosis and shrinkage of the socket tissues. **3. Clinical Pearls for NEET-PG:** * **Definition:** A contracted socket is characterized by the shortening of the conjunctival fornices (especially the inferior fornix). * **Commonest Cause:** The most common cause is the **non-wearing of a prosthesis** for a long duration after surgery, leading to disuse atrophy of the fornices. * **Management:** * *Mild:* Conformers or mucous membrane grafts. * *Severe:* Reconstruction using a split-thickness skin graft or amniotic membrane transplant. * **Distinction:** Do not confuse **Post-Enucleation Socket Syndrome (PESS)**—which includes fat atrophy and ptosis—with a **Contracted Socket**, which specifically refers to mucosal scarring.
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