Refractive Surgery — MCQs

Q: Which of the following is used for the treatment of Myopia?

Excimer Laser. **Explanation:** **Correct Answer: B. Excimer Laser** The **Excimer laser** (Argon-Fluoride gas, 193 nm wavelength) is the gold standard for corneal refractive surgeries like **LASIK, PRK, and SMILE**. It works via **photoablation**, a process where high-energy ultraviolet light breaks molecular bonds in the corneal stroma without generating heat (cold laser). In myopia, the Excimer laser is used to flatten the central cornea, thereby reducing its refractive power so that light focuses accurately on the retina. **Incorrect Options:** * **A. Nd:YAG Laser (1064 nm):** This is a solid-state laser used for **photodisruption**. Its primary uses in ophthalmology include Posterior Capsulotomy (for PCO) and Peripheral Iridotomy (for Angle-Closure Glaucoma). It is not used for reshaping the cornea. * **C. Carbamazepine:** This is an anticonvulsant and the first-line treatment for **Trigeminal Neuralgia**. It has no role in treating refractive errors. * **D. SSRIs (Selective Serotonin Reuptake Inhibitors):** These are antidepressants. In ophthalmology, they are clinically significant because they can occasionally cause mydriasis and precipitate acute angle-closure glaucoma, but they do not treat myopia. **High-Yield Clinical Pearls for NEET-PG:** 1. **Laser Wavelengths:** Excimer (193 nm), Nd:YAG (1064 nm), Argon (514 nm - used for photocoagulation in diabetic retinopathy). 2. **Femtosecond Laser:** Used in "Bladeless LASIK" to create the corneal flap; it operates at 1053 nm. 3. **Contraindications for LASIK:** Thin cornea (<450-480 μm), Keratoconus, and unstable refractive error. 4. **SMILE (Small Incision Lenticule Extraction):** The newest refractive procedure that uses only a Femtosecond laser, eliminating the need for a corneal flap.

Q: Which of the following are treatment modalities for myopia?

LASER Keratoplasty. **Explanation:** The treatment of myopia focuses on decreasing the refractive power of the eye, typically by flattening the central cornea. **LASER Keratoplasty** (specifically Excimer laser-based procedures like PRK and LASIK) is the gold standard for surgical correction. It works by photoablative decomposition, where the laser breaks molecular bonds to reshape the corneal stroma with extreme precision, effectively reducing the corneal curvature to focus light directly on the retina. **Analysis of Options:** * **Radial Keratotomy (RK):** While historically used for myopia, it involves making deep radial incisions in the peripheral cornea to flatten the center. It is largely obsolete due to complications like diurnal vision fluctuation and globe instability. * **LASER Keratomileusis:** This is a component of LASIK (Laser-Assisted In Situ Keratomileusis). While technically used, "Keratoplasty" is the broader, more encompassing term used in clinical nomenclature for corneal reshaping surgeries in this context. * **Epikeratophakia:** This involves suturing a pre-lathed donor corneal lenticule onto the surface of the patient's cornea. It was primarily used for aphakia or high myopia in children but is rarely performed today due to poor predictability. **High-Yield Clinical Pearls for NEET-PG:** * **Excimer Laser:** Uses Argon-Fluoride (ArF) gas, emitting UV light at **193 nm**. * **LASIK Criteria:** Stable refraction for 1 year, age >18 years, and a residual stromal bed thickness of at least **250 µm** to prevent corneal ectasia. * **Femtosecond Laser:** Used in "Bladeless LASIK" to create the corneal flap and in **SMILE** (Small Incision Lenticule Extraction) for flapless myopia correction.

Q: What is the wavelength of laser (in nanometers) used for shaping the cornea in refractive surgery?

193 nm. **Explanation:** The correct answer is **193 nm**. This wavelength belongs to the **Excimer laser** (Argon-Fluoride gas), which is the gold standard for corneal refractive surgeries like LASIK, PRK, and LASEK. **Why 193 nm is correct:** The Excimer laser operates in the far-ultraviolet spectrum. Its primary mechanism is **photoablation** (or photodecomposition). The high-energy 193 nm photons have enough energy to break intermolecular organic bonds in the corneal stroma without generating significant heat. This allows for extremely precise tissue removal (0.25 microns per pulse) without damaging the surrounding transparent corneal tissue, making it ideal for reshaping the cornea to correct refractive errors. **Analysis of Incorrect Options:** * **451 nm:** This falls within the blue light spectrum and is not typically used for therapeutic corneal ablation. * **532 nm (Frequency-doubled Nd:YAG):** This is a green laser used primarily for **retinal photocoagulation** (e.g., in Diabetic Retinopathy) and laser trabeculoplasty in glaucoma. * **1064 nm (Nd:YAG):** This is an infrared laser used for **photodisruption**. It is commonly used for Posterior Capsulotomy (after cataract surgery) and Peripheral Iridotomy. **High-Yield Clinical Pearls for NEET-PG:** * **Femtosecond Laser:** Uses a wavelength of **1053 nm** (near-infrared) and is used for creating the LASIK flap or in SMILE (Small Incision Lenticule Extraction). * **Photoablation vs. Photodisruption:** Remember that Excimer (193 nm) *ablates* (vaporizes), while Nd:YAG (1064 nm) *disrupts* (cuts/blasts) tissue. * **Corneal Thickness:** A minimum residual stromal bed of **250–300 microns** must be maintained after laser ablation to prevent corneal ectasia.

Q: Which of the following lasers is used for the treatment of myopia?

Excimer Laser. **Explanation:** **1. Why Excimer Laser is Correct:** The **Excimer laser** (Excited Dimer) is the gold standard for refractive surgeries like LASIK, PRK, and LASEK. It utilizes a **193 nm Argon-Fluoride (ArF) gas** mixture to produce ultraviolet light. The underlying mechanism is **photoablation**, where the laser breaks intermolecular bonds in the corneal stroma without generating heat. By precisely reshaping the central cornea (flattening it), the refractive power is reduced, thereby correcting myopia. **2. Why Other Options are Incorrect:** * **Nd:YAG Laser (1064 nm):** This is a solid-state laser used for **photodisruption**. Its primary uses include Posterior Capsulotomy (for PCO) and Peripheral Iridotomy (for Angle Closure Glaucoma). * **Argon Laser (488–514 nm):** This laser works via **photocoagulation**. It is used for retinal procedures like Pan-Retinal Photocoagulation (PRP) in diabetic retinopathy and for treating retinal breaks. * **Harmonium Laser:** This is a distractor and is not a standard laser used in clinical ophthalmology. **3. High-Yield Clinical Pearls for NEET-PG:** * **Femtosecond Laser (1053 nm):** Used for creating the corneal flap in "Bladeless LASIK" and for lenticule extraction in **SMILE** (Small Incision Lenticule Extraction). * **LASIK Contraindications:** Keratoconus (most important), thin corneas (<450-480 μm), and active ocular infections. * **Post-LASIK Complication:** The most common side effect is **Dry Eye**. The most serious (though rare) is **Corneal Ectasia**. * **Wavelength Memory:** Excimer (193 nm), Argon (514 nm), Nd:YAG (1064 nm).

Q: Excimer laser is used in which of the following conditions?

None of the above. ### Explanation The correct answer is **None of the above** because the Excimer laser is primarily used in **refractive surgery** to reshape the cornea, rather than for treating glaucoma, cataracts, or uveitis. #### 1. Why "None of the above" is correct The **Excimer laser** (Argon-Fluoride gas, wavelength **193 nm**) is a "cold" ultraviolet laser. It works through **photoablation**, which breaks intermolecular bonds in the corneal stroma without causing thermal damage to surrounding tissues. Its primary clinical applications include: * **LASIK** (Laser-assisted in situ keratomileusis) * **PRK** (Photorefractive keratectomy) * **PTK** (Phototherapeutic keratectomy) for superficial corneal dystrophies and scars. #### 2. Why other options are incorrect * **Glaucoma:** Lasers used here include the **Argon laser** or **Frequency-doubled Nd:YAG** (for Trabeculoplasty) and the **Nd:YAG laser** (for Peripheral Iridotomy). * **Cataract:** The **Femtosecond laser** is used in FLACS (Femtosecond Laser-Assisted Cataract Surgery) for capsulotomy and lens fragmentation. The **Nd:YAG laser** is used for Posterior Capsulotomy (treating after-cataract). * **Uveitis:** Lasers have no direct role in treating active uveitis, which is managed medically (steroids/cycloplegics). #### 3. High-Yield Clinical Pearls for NEET-PG * **Wavelength:** 193 nm (Far UV spectrum). * **Mechanism:** Photoablation (1 micron of tissue is removed per pulse). * **Nd:YAG Laser (1064 nm):** Used for Posterior Capsulotomy and Iridotomy (Mechanism: Photodisruption). * **Argon Laser (488–514 nm):** Used for Retinal Photocoagulation and Trabeculoplasty (Mechanism: Photocoagulation). * **Femtosecond Laser (1053 nm):** Used for creating LASIK flaps and in cataract surgery (Mechanism: Photodisruption).

$Refractive Surgery — MCQs$

Refractive Surgery Indian Medical PG Practice Questions and MCQs

Question 1: Which of the following is used for the treatment of Myopia?

A. Nd–YAG LASER
B. Excimer Laser (Correct Answer)
C. Carbamazepine
D. SSRI

Explanation: **Explanation:** **Correct Answer: B. Excimer Laser** The **Excimer laser** (Argon-Fluoride gas, 193 nm wavelength) is the gold standard for corneal refractive surgeries like **LASIK, PRK, and SMILE**. It works via **photoablation**, a process where high-energy ultraviolet light breaks molecular bonds in the corneal stroma without generating heat (cold laser). In myopia, the Excimer laser is used to flatten the central cornea, thereby reducing its refractive power so that light focuses accurately on the retina. **Incorrect Options:** * **A. Nd:YAG Laser (1064 nm):** This is a solid-state laser used for **photodisruption**. Its primary uses in ophthalmology include Posterior Capsulotomy (for PCO) and Peripheral Iridotomy (for Angle-Closure Glaucoma). It is not used for reshaping the cornea. * **C. Carbamazepine:** This is an anticonvulsant and the first-line treatment for **Trigeminal Neuralgia**. It has no role in treating refractive errors. * **D. SSRIs (Selective Serotonin Reuptake Inhibitors):** These are antidepressants. In ophthalmology, they are clinically significant because they can occasionally cause mydriasis and precipitate acute angle-closure glaucoma, but they do not treat myopia. **High-Yield Clinical Pearls for NEET-PG:** 1. **Laser Wavelengths:** Excimer (193 nm), Nd:YAG (1064 nm), Argon (514 nm - used for photocoagulation in diabetic retinopathy). 2. **Femtosecond Laser:** Used in "Bladeless LASIK" to create the corneal flap; it operates at 1053 nm. 3. **Contraindications for LASIK:** Thin cornea (<450-480 μm), Keratoconus, and unstable refractive error. 4. **SMILE (Small Incision Lenticule Extraction):** The newest refractive procedure that uses only a Femtosecond laser, eliminating the need for a corneal flap.

Question 2: Which of the following are treatment modalities for myopia?

A. Radial keratotomy
B. LASER Keratomileusis
C. Epikeratophaki
D. LASER Keratoplasty (Correct Answer)

Explanation: **Explanation:** The treatment of myopia focuses on decreasing the refractive power of the eye, typically by flattening the central cornea. **LASER Keratoplasty** (specifically Excimer laser-based procedures like PRK and LASIK) is the gold standard for surgical correction. It works by photoablative decomposition, where the laser breaks molecular bonds to reshape the corneal stroma with extreme precision, effectively reducing the corneal curvature to focus light directly on the retina. **Analysis of Options:** * **Radial Keratotomy (RK):** While historically used for myopia, it involves making deep radial incisions in the peripheral cornea to flatten the center. It is largely obsolete due to complications like diurnal vision fluctuation and globe instability. * **LASER Keratomileusis:** This is a component of LASIK (Laser-Assisted In Situ Keratomileusis). While technically used, "Keratoplasty" is the broader, more encompassing term used in clinical nomenclature for corneal reshaping surgeries in this context. * **Epikeratophakia:** This involves suturing a pre-lathed donor corneal lenticule onto the surface of the patient's cornea. It was primarily used for aphakia or high myopia in children but is rarely performed today due to poor predictability. **High-Yield Clinical Pearls for NEET-PG:** * **Excimer Laser:** Uses Argon-Fluoride (ArF) gas, emitting UV light at **193 nm**. * **LASIK Criteria:** Stable refraction for 1 year, age >18 years, and a residual stromal bed thickness of at least **250 µm** to prevent corneal ectasia. * **Femtosecond Laser:** Used in "Bladeless LASIK" to create the corneal flap and in **SMILE** (Small Incision Lenticule Extraction) for flapless myopia correction.

Question 3: What is the wavelength of laser (in nanometers) used for shaping the cornea in refractive surgery?

A. 193 nm (Correct Answer)
B. 451 nm
C. 532 nm
D. 1064 nm

Explanation: **Explanation:** The correct answer is **193 nm**. This wavelength belongs to the **Excimer laser** (Argon-Fluoride gas), which is the gold standard for corneal refractive surgeries like LASIK, PRK, and LASEK. **Why 193 nm is correct:** The Excimer laser operates in the far-ultraviolet spectrum. Its primary mechanism is **photoablation** (or photodecomposition). The high-energy 193 nm photons have enough energy to break intermolecular organic bonds in the corneal stroma without generating significant heat. This allows for extremely precise tissue removal (0.25 microns per pulse) without damaging the surrounding transparent corneal tissue, making it ideal for reshaping the cornea to correct refractive errors. **Analysis of Incorrect Options:** * **451 nm:** This falls within the blue light spectrum and is not typically used for therapeutic corneal ablation. * **532 nm (Frequency-doubled Nd:YAG):** This is a green laser used primarily for **retinal photocoagulation** (e.g., in Diabetic Retinopathy) and laser trabeculoplasty in glaucoma. * **1064 nm (Nd:YAG):** This is an infrared laser used for **photodisruption**. It is commonly used for Posterior Capsulotomy (after cataract surgery) and Peripheral Iridotomy. **High-Yield Clinical Pearls for NEET-PG:** * **Femtosecond Laser:** Uses a wavelength of **1053 nm** (near-infrared) and is used for creating the LASIK flap or in SMILE (Small Incision Lenticule Extraction). * **Photoablation vs. Photodisruption:** Remember that Excimer (193 nm) *ablates* (vaporizes), while Nd:YAG (1064 nm) *disrupts* (cuts/blasts) tissue. * **Corneal Thickness:** A minimum residual stromal bed of **250–300 microns** must be maintained after laser ablation to prevent corneal ectasia.

Question 4: Which of the following lasers is used for the treatment of myopia?

A. Nd-YAG LASER
B. Excimer Laser (Correct Answer)
C. Harmonium Laser
D. Argon Laser

Explanation: **Explanation:** **1. Why Excimer Laser is Correct:** The **Excimer laser** (Excited Dimer) is the gold standard for refractive surgeries like LASIK, PRK, and LASEK. It utilizes a **193 nm Argon-Fluoride (ArF) gas** mixture to produce ultraviolet light. The underlying mechanism is **photoablation**, where the laser breaks intermolecular bonds in the corneal stroma without generating heat. By precisely reshaping the central cornea (flattening it), the refractive power is reduced, thereby correcting myopia. **2. Why Other Options are Incorrect:** * **Nd:YAG Laser (1064 nm):** This is a solid-state laser used for **photodisruption**. Its primary uses include Posterior Capsulotomy (for PCO) and Peripheral Iridotomy (for Angle Closure Glaucoma). * **Argon Laser (488–514 nm):** This laser works via **photocoagulation**. It is used for retinal procedures like Pan-Retinal Photocoagulation (PRP) in diabetic retinopathy and for treating retinal breaks. * **Harmonium Laser:** This is a distractor and is not a standard laser used in clinical ophthalmology. **3. High-Yield Clinical Pearls for NEET-PG:** * **Femtosecond Laser (1053 nm):** Used for creating the corneal flap in "Bladeless LASIK" and for lenticule extraction in **SMILE** (Small Incision Lenticule Extraction). * **LASIK Contraindications:** Keratoconus (most important), thin corneas (<450-480 μm), and active ocular infections. * **Post-LASIK Complication:** The most common side effect is **Dry Eye**. The most serious (though rare) is **Corneal Ectasia**. * **Wavelength Memory:** Excimer (193 nm), Argon (514 nm), Nd:YAG (1064 nm).

Question 5: Excimer laser is used in which of the following conditions?

A. Glaucoma
B. Cataract
C. Uveitis
D. None of the above (Correct Answer)

Explanation: ### Explanation The correct answer is **None of the above** because the Excimer laser is primarily used in **refractive surgery** to reshape the cornea, rather than for treating glaucoma, cataracts, or uveitis. #### 1. Why "None of the above" is correct The **Excimer laser** (Argon-Fluoride gas, wavelength **193 nm**) is a "cold" ultraviolet laser. It works through **photoablation**, which breaks intermolecular bonds in the corneal stroma without causing thermal damage to surrounding tissues. Its primary clinical applications include: * **LASIK** (Laser-assisted in situ keratomileusis) * **PRK** (Photorefractive keratectomy) * **PTK** (Phototherapeutic keratectomy) for superficial corneal dystrophies and scars. #### 2. Why other options are incorrect * **Glaucoma:** Lasers used here include the **Argon laser** or **Frequency-doubled Nd:YAG** (for Trabeculoplasty) and the **Nd:YAG laser** (for Peripheral Iridotomy). * **Cataract:** The **Femtosecond laser** is used in FLACS (Femtosecond Laser-Assisted Cataract Surgery) for capsulotomy and lens fragmentation. The **Nd:YAG laser** is used for Posterior Capsulotomy (treating after-cataract). * **Uveitis:** Lasers have no direct role in treating active uveitis, which is managed medically (steroids/cycloplegics). #### 3. High-Yield Clinical Pearls for NEET-PG * **Wavelength:** 193 nm (Far UV spectrum). * **Mechanism:** Photoablation (1 micron of tissue is removed per pulse). * **Nd:YAG Laser (1064 nm):** Used for Posterior Capsulotomy and Iridotomy (Mechanism: Photodisruption). * **Argon Laser (488–514 nm):** Used for Retinal Photocoagulation and Trabeculoplasty (Mechanism: Photocoagulation). * **Femtosecond Laser (1053 nm):** Used for creating LASIK flaps and in cataract surgery (Mechanism: Photodisruption).

Practice by Chapter

Corneal Topography and Tomography

Practice Questions

Patient Selection for Refractive Surgery

Practice Questions

LASIK

Practice Questions

PRK and LASEK

Practice Questions

Small Incision Lenticule Extraction

Practice Questions

Phakic IOLs

Practice Questions

Refractive Lens Exchange

Practice Questions

Astigmatic Keratotomy

Practice Questions

Intrastromal Corneal Ring Segments

Practice Questions

Corneal Collagen Crosslinking

Practice Questions

Complications of Refractive Surgery

Practice Questions

Future Trends in Refractive Surgery

Practice Questions

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