Ophthalmic Surgery Practice Questions

Q: Deep anterior lamellar keratoplasty is indicated in:

Superficial corneal opacities. **Explanation:** **Deep Anterior Lamellar Keratoplasty (DALK)** is a partial-thickness cornea transplant procedure where the diseased corneal stroma is removed down to the level of Descemet’s membrane (DM) and the endothelium. The patient’s own healthy endothelium and DM are preserved. **Why Option D is Correct:** DALK is indicated for conditions involving the **anterior and mid-to-deep stroma** where the **endothelium is healthy and functional**. While "superficial corneal opacities" can be treated with simpler lamellar techniques, they are a valid indication for DALK if the scarring extends into the deeper stroma. Other classic indications include Keratoconus (with no history of hydrops), corneal dystrophies (e.g., Macular, Lattice), and scars from healed keratitis. **Why Other Options are Incorrect:** * **Option A & C:** Diseases involving **endothelial damage** (e.g., Fuchs' Dystrophy) or **Bullous Keratopathy** (caused by endothelial pump failure) are contraindications for DALK. These require either **Penetrating Keratoplasty (PKP)** or **Endothelial Keratoplasty (DSEK/DMEK)**. * **Option B:** **Full-thickness opacities** involve all layers, including the endothelium. Replacing only the anterior layers would leave the posterior scarring intact, resulting in poor visual outcomes. These require a PKP. **High-Yield Clinical Pearls for NEET-PG:** * **Advantage of DALK:** The primary benefit is the **elimination of endothelial graft rejection**, which is the most common cause of failure in full-thickness grafts. * **"Big Bubble" Technique:** This is the most popular surgical method (described by Anwar) to separate the stroma from the Descemet’s membrane using air. * **Key Contraindication:** Any condition with a damaged or diseased endothelium. * **Comparison:** If the question asks for the treatment of choice for **Keratoconus**, DALK is now preferred over PKP because it preserves the host endothelium.

Q: In canalicular blockage, what are the typical findings of the Jones test?

Both first and second tests are negative. ### Explanation The Jones Dye Tests are used to differentiate between a functional and a mechanical obstruction of the lacrimal drainage system. **1. Why Option D is Correct:** In **canalicular blockage**, there is a physical obstruction in the proximal part of the drainage system (before the lacrimal sac). * **Jones Test I (Primary):** Fluorescein dye is instilled into the conjunctival sac. Since the canaliculi are blocked, the dye cannot enter the lacrimal sac or reach the inferior meatus of the nose. Thus, the test is **negative** (no dye recovered from the nose). * **Jones Test II (Secondary):** This involves washing out the remaining dye and syringing saline through the punctum. In canalicular blockage, the saline will either encounter a "soft hit" and reflux through the opposite punctum or fail to enter the sac entirely. No dye will reach the nose during syringing, making the test **negative**. **2. Why Other Options are Incorrect:** * **Option A:** This pattern does not exist clinically; if the first test is positive (dye reaches the nose spontaneously), the system is patent, and a second test is unnecessary. * **Option B:** This indicates a **functional block** (e.g., pump failure). Dye doesn't reach the nose spontaneously (Test I negative), but syringing successfully pushes the dye into the nose (Test II positive). * **Option C:** This is impossible as the second test is only performed if the first is negative. **3. Clinical Pearls for NEET-PG:** * **Jones I:** Tests the "physiological" patency (lacrimal pump). * **Jones II:** Tests the "anatomical" patency. * **Positive Jones II:** Dye recovered in the nose (indicates functional block). * **Negative Jones II:** No dye recovered (indicates total mechanical obstruction). * **High-Yield Site:** Canalicular block is a **proximal** obstruction; Nasolacrimal duct (NLD) block is a **distal** obstruction.

Q: Which of the following instruments is NOT used in intracapsular lens extraction?

Phaco-emulsifier. **Explanation:** The core concept here is distinguishing between **Intracapsular Cataract Extraction (ICCE)** and **Extracapsular Cataract Extraction (ECCE)** techniques. **Why Phaco-emulsifier is the correct answer:** Phacoemulsification is a modern form of **ECCE**. It uses ultrasonic energy to fragment the lens nucleus *within* the lens capsule, followed by aspiration. In ICCE, the entire lens along with the intact capsule is removed; therefore, a machine designed to break up the lens inside the capsule is fundamentally incompatible with the ICCE technique. **Analysis of incorrect options (Instruments used in ICCE):** * **Cryo extractor:** This is the most common instrument for ICCE. It uses a probe cooled by CO2 or N2O to create a "cryo-adhesion" to the anterior capsule and the lens cortex, allowing the lens to be pulled out in toto. * **Elschning’s forceps:** These are specialized intracapsular forceps used to grasp the lens capsule (usually at the 6 o'clock position) to facilitate its delivery. * **Von Graefe’s cataract knife:** Historically used in ICCE to create a large (180-degree) limbal incision to allow the delivery of the entire lens. **High-Yield Clinical Pearls for NEET-PG:** * **ICCE Indication:** Currently, the primary indication for ICCE is **subluxated or dislocated lenses** (e.g., Marfan syndrome). * **Complications of ICCE:** Higher risk of vitreous loss, aphakic glaucoma, and **Cystoid Macular Edema (CME)** compared to ECCE. * **Enzymatic Zonulolysis:** Alpha-chymotrypsin was historically used in ICCE to dissolve zonules, facilitating easier lens removal. * **Phacoemulsification:** Uses a **Piezoelectric crystal** to convert electrical energy into mechanical vibrations (frequency ~40,000 Hz).

Q: What size of donor cornea is taken in keratoplasty?

8 mm. **Explanation:** In Penetrating Keratoplasty (PKP), the goal is to replace the central diseased cornea with a healthy donor graft. The standard size for a donor cornea typically ranges between **7.5 mm and 8.5 mm**, making **8 mm** the most appropriate choice among the options provided. **Why 8 mm is correct:** A graft size of 7.5–8.5 mm is considered "ideal" because it is large enough to clear the visual axis and remove most central pathology, yet small enough to remain away from the limbus. Staying away from the limbus is crucial to minimize the risk of graft rejection, as the limbus is highly vascularized and contains immune cells. **Analysis of incorrect options:** * **2 mm & 4 mm:** These sizes are far too small for optical keratoplasty. They would result in significant irregular astigmatism and would not sufficiently cover the pupillary area for functional vision. * **6 mm:** While used in rare pediatric cases or specific tectonic grafts, a 6 mm graft is generally considered too small for adults, as it leads to high postoperative astigmatism and a limited visual field. **High-Yield Clinical Pearls for NEET-PG:** * **The "Oversizing" Rule:** In standard PKP, the donor button is usually cut **0.25 mm to 0.50 mm larger** than the recipient bed (e.g., an 8.0 mm donor for a 7.5 mm bed). This ensures a watertight closure, reduces postoperative flattening, and helps prevent secondary glaucoma. * **Large Grafts (>9 mm):** These are avoided in routine cases because they are closer to the limbal vessels, significantly increasing the risk of **immunological rejection** and peripheral anterior synechiae (PAS). * **Small Grafts (<7 mm):** These are associated with high **astigmatism** and poor optical outcomes.

Q: Which of the following methods is NOT used to measure corneal thickness?

Javal-Schiøtz method. **Explanation:** The measurement of corneal thickness is known as **Pachymetry**. The **Javal-Schiøtz method** is the correct answer because it is a technique used for **Keratometry**, not pachymetry. It measures the curvature of the anterior corneal surface to determine corneal power and astigmatism, but it cannot measure the depth or thickness of the corneal tissue. **Analysis of Options:** * **A. OCT (Optical Coherence Tomography):** Specifically, Anterior Segment OCT (AS-OCT) uses light waves to provide high-resolution cross-sectional images, allowing for precise, non-contact measurement of corneal thickness. * **B. Ultrasonography:** Ultrasound Pachymetry is considered the traditional **gold standard**. It uses a high-frequency (20 MHz) probe to measure the time taken for sound waves to reflect from the epithelium and endothelium. * **C. Orbscan:** This is a slit-scanning topography system that provides a global map of the cornea, measuring both the anterior and posterior surfaces to calculate thickness across the entire cornea. **High-Yield Clinical Pearls for NEET-PG:** * **Average Central Corneal Thickness (CCT):** Approximately **540–560 μm**. * **Glaucoma Correlation:** CCT is vital for accurate Intraocular Pressure (IOP) readings. A thin cornea leads to an underestimation of IOP, while a thick cornea leads to an overestimation (Goldmann Applanation Tonometry). * **Refractive Surgery:** A minimum residual stromal bed (usually >250 μm) must be maintained post-LASIK to prevent corneal ectasia. * **Optical Pachymetry:** Uses a slit-lamp attachment (e.g., Haag-Streit) based on the principle of optical sectioning.

Q: Which gas is used in retinal tamponade?

SF6. **Explanation:** **Correct Answer: A. SF6 (Sulfur Hexafluoride)** In vitreoretinal surgery, **intraocular gases** are used as a "tamponade" to provide surface tension that holds the retina against the retinal pigment epithelium (RPE) while a chorioretinal scar forms. **SF6** is a commonly used gas because it is inert, non-toxic, and expands to roughly double its volume once injected into the eye. It remains in the vitreous cavity for approximately 10–14 days, providing sufficient time for retinal reattachment. Another frequently used gas is **C3F8 (Perfluoropropane)**, which lasts longer (up to 8 weeks). **Why the other options are incorrect:** * **B. Ethylene oxide:** This is a potent gas used primarily for **sterilization** of heat-sensitive medical equipment (e.g., plastic syringes, intraocular lenses). It is highly toxic and never injected into the eye. * **C. Nitrous oxide (N2O):** This is an **inhalational anesthetic** agent. It is actually contraindicated or must be discontinued during retinal surgery involving gas because it can diffuse into the gas bubble, causing a rapid increase in intraocular pressure (IOP). * **D. CO2:** Carbon dioxide is used in laparoscopy for insufflation but has no role in retinal tamponade as it is rapidly absorbed by the blood. **High-Yield Clinical Pearls for NEET-PG:** 1. **Expansion Ratios:** SF6 expands **2x** its volume; C3F8 expands **4x** its volume. 2. **Post-operative Positioning:** Patients must maintain a specific "prone" or "face-down" position to ensure the buoyant gas bubble presses against the retinal break. 3. **Travel Warning:** Patients with an intraocular gas bubble must **avoid air travel** or high altitudes, as the decrease in atmospheric pressure causes the gas to expand, leading to a sight-threatening spike in IOP.

Q: Which atomic environment is used in the laser machines employed in ophthalmology?

Any of the above. **Explanation:** The correct answer is **D. Any of the above**, as laser technology in ophthalmology utilizes various mediums (active environments) to generate specific wavelengths required for different clinical applications. 1. **Crystal Rod (Solid-state lasers):** These use a solid crystalline medium. The most common example is the **Nd:YAG laser** (Neodymium-doped Yttrium Aluminum Garnet), used for posterior capsulotomy and peripheral iridotomy. Another example is the Frequency-doubled Nd:YAG (Green laser) used in retinal photocoagulation. 2. **Gas-filled cavity (Gas lasers):** These use gases or gas mixtures. Examples include the **Argon laser** (blue-green spectrum) used for retinal procedures and the **Excimer laser** (Argon-Fluoride gas) used in refractive surgeries like LASIK and PRK for corneal ablation. 3. **Fluid-filled cavity (Liquid/Dye lasers):** These use organic dyes (e.g., Rhodamine) dissolved in a liquid solvent. They are tunable to different wavelengths, historically used in specialized retinal treatments, though largely replaced by solid-state diodes today. **Why "Any of the above" is correct:** Laser (Light Amplification by Stimulated Emission of Radiation) requires an **active medium** to achieve population inversion. Since ophthalmology targets diverse tissues (cornea, iris, retina), different media are employed to produce the specific energy levels and wavelengths needed. **High-Yield Clinical Pearls for NEET-PG:** * **Excimer Laser:** 193 nm (Ultraviolet); used for "Photo-Refractive" work. * **Nd:YAG Laser:** 1064 nm (Infrared); used for "Photodisruption" (cold cutting). * **Argon Laser:** 488–514 nm; used for "Photocoagulation." * **Femtosecond Laser:** Uses ultra-short pulses ($10^{-15}$ seconds) for high precision in LASIK flaps and cataract surgery.

Q: What is the treatment of chronic dacryocystitis?

All of the above. The treatment of **Chronic Dacryocystitis** is multifaceted, aiming to eliminate infection, restore drainage, and prevent complications like orbital cellulitis. **Explanation of the Correct Answer:** The correct answer is **"All of the above"** because management involves a step-wise approach depending on the stage and patient profile: 1. **Antibiotics:** Used to control the active infection and prevent the spread of bacteria. While they do not cure the underlying anatomical obstruction, they are essential for managing the "chronic catarrhal" or "mucocele" stages. 2. **Probing:** This is the primary treatment for **congenital** nasolacrimal duct obstruction (NLDO). In adults, while less successful as a permanent cure, it can be used diagnostically or in early incomplete stenosis. 3. **Dacryocystorhinostomy (DCR):** This is the **gold standard surgical treatment** for chronic dacryocystitis. It creates a new permanent bypass channel between the lacrimal sac and the middle meatus of the nose. **Why individual options are not the "only" answer:** * **A (DCR):** While it is the definitive surgery, it cannot be performed during an acute exacerbation without first using antibiotics. * **B (Antibiotics):** These are supportive, not curative for the mechanical obstruction. * **C (Probing):** Effective in infants but rarely curative in long-standing adult chronic cases. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard Surgery:** DCR (Dacryocystorhinostomy). * **Indications for DCT (Dacryocystectomy):** Indicated if the patient is very elderly, has a shrunken/fibrotic sac, or has a lacrimal sac tumor. * **Most common organism:** *Staphylococcus aureus* (Acute), *Streptococcus pneumoniae* (Chronic). * **Investigation of choice:** Dacryocystography (DCG) to locate the site of obstruction. * **Jones Test:** Used to differentiate between anatomical and functional lacrimal obstruction.

Question 1

Deep anterior lamellar keratoplasty is indicated in:

Accepted Answer

Superficial corneal opacities

Answer

Disease of deeper cornea e.g. endothelial damage

Answer

Full thickness corneal opacities

Answer

Bullous keratopathy

Question 2

Which of the following statements regarding phacoemulsification surgery is not true?

Accepted Answer

Hydrodissection is performed to separate the layers of the nucleus.

Answer

A clear corneal incision is preferred.

Answer

Capsulorhexis is performed to remove the anterior capsule.

Answer

The divide and conquer technique is used for nucleus removal.

Question 3

In canalicular blockage, what are the typical findings of the Jones test?

Accepted Answer

Both first and second tests are negative

Answer

First test positive, second test negative

Answer

First test negative, second test positive

Answer

Both first and second tests are positive

Question 4

Which of the following instruments is NOT used in intracapsular lens extraction?

Accepted Answer

Phaco-emulsifier

Answer

Cryo extractor

Answer

Elschning's forceps

Answer

Von Graefe's cataract knife

Question 5

A 60-year-old man presented with watering from his left eye for one year. Syringing revealed a patent drainage system, and the rest of the ocular examination was normal. A provisional diagnosis of lacrimal pump failure was made. Confirmation of the diagnosis would be by which of the following investigations?

Accepted Answer

Dacryoscintigraphy

Answer

Dacryocystography

Answer

Pressure syringing

Answer

Canaliculus irrigation test

Question 6

What size of donor cornea is taken in keratoplasty?

Accepted Answer

8 mm

Answer

2 mm

Answer

4 mm

Answer

6 mm

Question 7

Which of the following methods is NOT used to measure corneal thickness?

Accepted Answer

Javal-Schiøtz method

Answer

OCT (Optical Coherence Tomography)

Answer

Ultrasonography

Answer

Orbscan

Question 8

Which gas is used in retinal tamponade?

Accepted Answer

SF6

Answer

Ethylene oxide

Answer

Nitrous oxide

Answer

CO2

Question 9

Which atomic environment is used in the laser machines employed in ophthalmology?

Accepted Answer

Any of the above

Answer

Crystal rod

Answer

Fluid-filled cavity

Answer

Gas-filled cavity

Question 10

What is the treatment of chronic dacryocystitis?

Accepted Answer

All of the above

Answer

Dacryocystorhinostomy

Answer

Antibiotics

Answer

Probing

Ophthalmic Surgery — MCQs

Ophthalmic Surgery — MCQs

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