Refractive Surgery — MCQs

$Refractive Surgery — MCQs$

Refractive Surgery Indian Medical PG Practice Questions and MCQs

Question 21: Which of the following is a long-term side effect of phakic IOLs?

A. Chronic glaucoma (Correct Answer)
B. Retinal detachment
C. Optic neuritis
D. Cataract formation

Explanation: ***Chronic glaucoma*** - Chronic glaucoma is a well-recognized long-term complication of phakic IOL implantation, developing through multiple mechanisms: - **Pigment dispersion** from iris chafing can clog the trabecular meshwork - **Chronic inflammation** in the anterior chamber can impair aqueous outflow - **Pupillary block** can occur with certain IOL designs - This complication necessitates **lifelong monitoring** of intraocular pressure in all phakic IOL patients *Retinal detachment* - While retinal detachment can occur after phakic IOL surgery, it is primarily related to **pre-existing high myopia** (the underlying indication for surgery) rather than being a direct effect of the IOL itself - The risk is similar to that in unoperated high myopes *Optic neuritis* - **Optic neuritis** is an inflammatory condition of the optic nerve, typically associated with **autoimmune disorders** (e.g., multiple sclerosis) or infections - It has **no association** with phakic IOL implantation *Cataract formation* - While cataract formation is a recognized long-term complication of phakic IOLs (particularly with anterior chamber IOLs or ICLs touching the crystalline lens), **chronic glaucoma** is the more commonly emphasized long-term side effect requiring ongoing surveillance

Question 22: Oblate ellipsoid appearance of cornea is seen in which of the following conditions?

A. Astigmatism with the rule
B. Bi-oblique astigmatism condition
C. Oblique astigmatism condition
D. Post myopic LASIK surgery (Correct Answer)

Explanation: ***Post myopic LASIK surgery*** - Following **myopic LASIK**, the central cornea is flattened, leading to an **oblate ellipsoid shape** where the periphery is steeper than the center. - This flattened central cornea is a direct result of tissue ablation to correct **myopia**. *Astigmatism with the rule* - In **astigmatism with the rule**, the vertical meridian of the cornea is steeper than the horizontal meridian, which is a **prolate** rather than an **oblate** shape. - It does not involve a central flattening of the cornea but rather a difference in curvature between principal meridians. *Bi-oblique astigmatism condition* - This refers to an astigmatism where the two principal meridians are not 90 degrees apart and are both oblique, meaning they are not horizontal or vertical. - While it describes the orientation of astigmatism, it does not specifically result in an **oblate ellipsoid corneal shape**. *Oblique astigmatism condition* - **Oblique astigmatism** occurs when the steepest and flattest meridians of the cornea are located at an angle other than 90 or 180 degrees. - Like other forms of astigmatism, it describes the orientation of corneal curvature differences, not a central flattening that defines an **oblate ellipsoid**.

Question 23: Which of the following is not a standard treatment for myopia?

A. Phakic intraocular lens
B. Radial Keratotomy
C. Holmium laser thermoplasty (Correct Answer)
D. LASIK

Explanation: ***Holmium laser thermoplasty*** - This procedure was explored for the treatment of **hyperopia**, not myopia, as it aims to steepen the cornea to increase its refractive power. - It involves using a holmium laser to apply heat to the peripheral cornea, causing **collagen shrinkage** and steepening, which is the opposite of what is needed for myopia correction. *LASIK* - **LASIK (Laser-Assisted in Situ Keratomileusis)** is a common and effective surgical procedure for correcting myopia by reshaping the cornea to reduce its refractive power. - It involves creating a **corneal flap** and using an excimer laser to remove tissue from the underlying stromal bed. *Phakic intraocular lens* - **Phakic intraocular lenses (IOLs)** are implanted into the eye without removing the natural lens and are a standard treatment for moderate to high myopia, especially in patients not suitable for LASIK. - They work by adding refractive power to the eye, allowing light to focus correctly on the retina. *Radial Keratotomy* - **Radial Keratotomy (RK)** was an early surgical procedure for myopia, involving making radial incisions in the cornea to flatten it and reduce its refractive power. - Although largely replaced by LASIK due to its unpredictable outcomes and potential for glare and night vision problems, it was historically a standard treatment for myopia.

Question 24: In a case of myopia, LASIK can correct up to how many diopters?

A. -4D
B. -12D (Correct Answer)
C. -20D
D. -6D

Explanation: ***-12D*** - LASIK can effectively correct myopia up to approximately **-12 diopters** in suitable candidates, though this can vary slightly based on individual corneal thickness and health. - The excimer laser reshapes the **cornea** to reduce its curvature, thereby decreasing the focusing power of the eye and correcting the myopic error. *-20D* - While some highly myopic individuals might desire such a correction, LASIK is generally not recommended or effective for myopia higher than **-12 to -14 diopters** due to limitations in corneal tissue removal and potential for complications. - Correcting very high myopia with LASIK would require removing too much corneal tissue, potentially leading to **corneal instability** or vision-threatening complications like **ectasia**. *-6D* - This is a common and highly successful range for LASIK correction, but it represents only a **moderate level of myopia** and not the maximum correctable range. - Patients with myopia of -6D typically achieve excellent visual outcomes with very low complication rates after LASIK. *-4D* - This is a relatively low level of myopia, and LASIK is very effective for this amount of correction, but it is far from the **upper limit** of what LASIK can achieve. - This level of correction requires minimal corneal reshaping and typically results in a very high success rate and predictable outcomes.

Question 25: What is a contraindication for LASIK surgery?

A. >20 years
B. Keratoconus (Correct Answer)
C. Normal cornea
D. Myopia of -8D

Explanation: ***Keratoconus*** - **Keratoconus** is an absolute contraindication for LASIK as it involves progressive thinning and steepening of the cornea, which can be exacerbated by surgical removal of corneal tissue during LASIK, leading to further visual deterioration. - Performing LASIK on an already compromised cornea can worsen the instability and lead to severe complications, including **corneal ectasia**. *>20 years* - This is generally considered a suitable age for LASIK, as **refractive errors** are typically stable by this age. - Most surgeons prefer patients to be at least 18-21 years old to ensure that their **eyesight has stabilized**. *Myopia of -8D* - A **myopia** of -8 diopters is within the treatable range for LASIK for many patients, provided other corneal parameters are normal. - While higher prescriptions may have a slightly increased risk of complications like **dry eyes** or **halos**, it is not an absolute contraindication. *Normal cornea* - A normal cornea is a prerequisite for LASIK surgery, indicating that the eye is **healthy** and capable of undergoing the procedure safely. - The cornea's thickness and shape are crucial for determining eligibility and ensuring a successful outcome.

Question 26: 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 27: Presently, the surgical treatment of choice in a 22-year-old male with 10D myopia is

A. Phakic intraocular lens (Correct Answer)
B. Refractive lens exchange
C. Wavefront guided LASIK
D. Femtosecond laser LASIK

Explanation: ***Phakic intraocular lens*** - For high myopia such as **10D in a young patient**, phakic intraocular lenses are often preferred as they provide superior optical quality and are reversible, preserving the natural lens. - This procedure avoids removing the natural lens, which is important for maintaining **accommodation** [1] in a young individual. *Refractive lens exchange* - This procedure involves removing the natural lens and replacing it with an artificial intraocular lens, similar to cataract surgery. - It is generally reserved for older patients with high refractive errors or those already developing **cataracts**, as it sacrifices the eye's natural ability to accommodate. *Wavefront guided LASIK* - LASIK (Laser-Assisted In Situ Keratomileusis) involves reshaping the cornea and is less effective and may carry higher risks for very high myopia (typically above **-8 to -10 diopters**). - It can thin the cornea excessively in cases of high myopia [1], potentially leading to **ectasia**. *Femtosecond laser LASIK* - While using a femtosecond laser for flap creation improves safety in LASIK, the fundamental limitations of corneal reshaping for **high myopia (e.g., thinning of the cornea)** still apply. - It does not overcome the issues of insufficient tissue for correction or potential long-term corneal stability concerns in severe myopia.

Question 28: 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.

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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