LASIK — MCQs
Which laser is used in the management of posterior capsule opacification (PCO)?
Which of the following is not a relative contraindication for breast conservative surgery?
What is the most likely complication of the condition shown in the image below?
Which keratometry reading is most accurate in post-LASIK eyes for IOL power calculation?
Laser used in LASIK is:
The laser procedure, most often used for treating iris neovascularization is
Maximum correction of myopia can be done by?
What does a visual acuity test primarily assess?
Which of the following is a contraindication to topical steroids?
Which of the following is used for the treatment of Myopia?
LASIK Indian Medical PG Practice Questions and MCQs
Question 1: Which laser is used in the management of posterior capsule opacification (PCO)?
- A. Krypton
- B. Argon
- C. Excimer
- D. Nd:YAG (Correct Answer)
Explanation: ***Nd:YAG*** - The **Nd:YAG laser** is the standard treatment for posterior capsule opacification (PCO) due to its ability to create a small opening in the **opacified posterior capsule** without damaging adjacent structures. - This laser works by **photodisruption**, using short pulses of high-energy light to create plasma and mechanically break apart the capsular tissue. *Krypton* - **Krypton lasers** are primarily used in ophthalmology for **retinal photocoagulation**, particularly for conditions like diabetic retinopathy and macular edema. - They are not used for treating PCO as their mechanism is based on thermal coagulation, which would be inappropriate for the delicate posterior capsule. *Argon* - **Argon lasers** are also used for **retinal photocoagulation** and for treating conditions like **glaucoma** (e.g., argon laser trabeculoplasty). - Similar to krypton lasers, their thermal effects are not suitable for the precise, non-thermal disruption required for PCO treatment. *Excimer* - The **excimer laser** is best known for its use in **refractive surgery** like LASIK and PRK to reshape the cornea. - Its mechanism involves **photoablation**, precisely removing tissue, but it is not used for creating an opening in the posterior capsule.
Question 2: Which of the following is not a relative contraindication for breast conservative surgery?
- A. Multicentric disease
- B. Previous radiation to breast
- C. Large tumor size
- D. Small tumor size (<3cm) (Correct Answer)
Explanation: ***Small tumor size (<3cm)*** ✓ - A small tumor size is **NOT a contraindication** for breast-conserving surgery; it is actually a **favorable condition** and an indication for breast conservation. - Small tumors allow for complete tumor removal with good cosmetic outcomes and adequate margins. - This is the **correct answer** as it is the only option that is NOT a relative contraindication. *Multicentric disease* - **Multicentric disease** refers to the presence of multiple tumor foci in **different quadrants** of the breast, making complete surgical removal challenging with breast-conserving surgery. - This is a **relative contraindication** as it increases the risk of **positive margins** and local recurrence, making mastectomy often a more appropriate option. *Previous radiation to breast* - Prior radiation therapy to the breast is a **contraindication** (often considered absolute) for subsequent breast radiation, which is an essential component of breast-conserving therapy. - Re-irradiation carries a high risk of severe **skin and tissue toxicity**, making further breast conservation unfeasible. *Large tumor size* - A large tumor size is a **relative contraindication** as it can make it difficult to achieve **clear surgical margins** while maintaining an acceptable cosmetic result. - However, **neoadjuvant chemotherapy** may downstage large tumors to make them suitable for breast-conserving surgery. - Without tumor reduction, it often requires **mastectomy**.
Question 3: What is the most likely complication of the condition shown in the image below?
- A. Exposure Keratitis (Correct Answer)
- B. Difficulty in eye movement
- C. Cataract
- D. Glaucoma
Explanation: ***Exposure Keratitis*** - The image shows **proptosis** (exophthalmos) of the right eye, where the eyeball protrudes forward. This condition often leads to incomplete eyelid closure (lagophthalmos). - **Exposure keratitis** occurs when the cornea is inadequately covered by the eyelids, leading to drying and damage due to constant exposure to air and environmental factors. *Difficulty in eye movement* - While **proptosis** can sometimes be associated with restricted eye movements (e.g., in severe Graves' ophthalmopathy due to muscle swelling), it is not the **most likely direct complication** of the exposure itself. - The image primarily depicts the physical displacement of the globe, which predisposes to corneal issues, not necessarily oculomotor dysfunction as the primary complication. *Cataract* - **Cataracts** are opacities of the lens and are typically associated with aging, trauma, or certain systemic conditions (e.g., diabetes, steroid use). - They are not a direct or common complication of **proptosis** or the resulting **exposure of the ocular surface**. *Glaucoma* - **Glaucoma** is a group of conditions characterized by damage to the optic nerve, often due to elevated intraocular pressure. - While severe **proptosis** leading to orbital congestion can theoretically increase intraocular pressure, it is not the most direct or prevalent complication compared to **exposure keratitis**, which is a direct consequence of inadequate globe protection.
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: Laser used in LASIK is:
- A. Excimer (Correct Answer)
- B. Argon
- C. Holmium
- D. Nd-yag
Explanation: ***Excimer*** - An **excimer laser** is used in LASIK procedures due to its ability to precisely ablate (remove) corneal tissue without causing thermal or collateral damage to surrounding tissues. - This laser operates in the **ultraviolet (UV) spectrum** and uses a mixture of inert and halogen gases (e.g., argon fluoride) to produce its beam. *Argon* - **Argon lasers** are primarily used for procedures involving the **retina and iris**, such as panretinal photocoagulation for diabetic retinopathy or iridotomy for narrow-angle glaucoma. - They emit light in the **visible blue-green spectrum**, which is absorbed by melanin and hemoglobin. *Holmium* - **Holmium lasers** are used in ophthalmology for procedures like **sclerostomy** (creating a drainage channel for glaucoma) or **transscleral cyclophotocoagulation**. - They operate in the **infrared spectrum** and are known for their strong tissue absorption and thermal effect. *Nd-yag* - A **Nd:YAG laser** is commonly used for **posterior capsulotomy** after cataract surgery to treat posterior capsular opacification, and for **peripheral iridotomy** in glaucoma. - It emits light in the **infrared spectrum** and works by creating photodisruption (plasma formation) to cut tissue without direct thermal effects.
Question 6: The laser procedure, most often used for treating iris neovascularization is
- A. Panretinal photocoagulation (PRP) (Correct Answer)
- B. Laser iridoplasty
- C. Laser trabeculoplasty
- D. Goniophotocoagulation
Explanation: ***Panretinal photocoagulation (PRP)*** - **PRP** is the most effective laser procedure for **iris neovascularization** and **neovascular glaucoma**, as it ablates the ischemic retina, reducing the production of **vascular endothelial growth factor (VEGF)**. - By destroying the ischemic peripheral retina, PRP reduces the **angiogenic drive** that leads to new vessel formation on the iris and in the angle. *Laser iridoplasty* - This procedure involves applying laser energy to the peripheral iris to cause contraction and widen the **anterior chamber angle**, primarily used for **angle-closure glaucoma**. - While it can open a closed angle, it does not address the underlying **ischemic drive** causing neovascularization. *Laser trabeculoplasty* - This procedure targets the **trabecular meshwork** to improve aqueous humor outflow, commonly used for **open-angle glaucoma**. - It does not directly affect **iris neovascularization** or the ischemic factors driving its development. *Goniophotocoagulation* - This involves directly lasering new vessels in the **anterior chamber angle**, often as an adjunct to PRP, but it's not the primary treatment to prevent **iris neovascularization**. - It treats existing vessels but does not address the underlying cause of **retinal ischemia** that promotes new vessel growth.
Question 7: 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 8: 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 9: Which of the following is a contraindication to topical steroids?
- A. Dendritic ulcer (Correct Answer)
- B. Herpetic stromal keratitis without epithelial defect
- C. Elevated intraocular pressure
- D. Non-infectious anterior uveitis
Explanation: ***Dendritic ulcer*** - A **dendritic ulcer** is characteristic of **herpes simplex keratitis**, which is an active viral infection of the cornea. - **Topical steroids** are contraindicated because they can suppress the immune response, leading to viral replication, corneal melt, and potentially severe vision loss or perforation. *Herpetic stromal keratitis without epithelial defect* - In cases of **stromal keratitis**, where the infection is deeper and an intact epithelium is present, topical steroids may be used cautiously in conjunction with antiviral agents to reduce inflammation and scarring. - The primary concern with steroids in herpes simplex keratitis is activating viral replication in the presence of an **epithelial defect**, which is not present here. *Elevated intraocular pressure* - **Elevated intraocular pressure** is a known side effect of topical steroid use, especially with prolonged administration, but it is not an absolute contraindication in itself. - It necessitates careful monitoring and may require concurrent glaucoma treatment, but the primary condition needing steroids may still warrant their use. *Non-infectious anterior uveitis* - **Topical corticosteroids** are the **mainstay of treatment** for non-infectious anterior uveitis to reduce inflammation and prevent complications such as synechiae and vision loss. - The benefits of controlling inflammation in uveitis generally outweigh the risks associated with judicious steroid use.
Question 10: 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.
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