Patient Selection for Refractive Surgery — MCQs
Which of the following is a contraindication to topical steroids?
Which of the following is not a relative contraindication for breast conservative surgery?
Which keratometry reading is most accurate in post-LASIK eyes for IOL power calculation?
Which of the following is TRUE about screening for Trichomonas vaginalis?
Which of the following statements about conjunctival lesions is NOT true?
Maximum correction of myopia can be done by?
A lady wants LASIK surgery for her daughter. All the following are indications for performing LASIK surgery, except:
A lady wants LASIK surgery for her daughter. She asks for your opinion. All the following things are suitable for performing LASIK surgery except:
Which is an example of Simple Myopic Astigmatism?
1mm change in axial length of the eyeball would change the refracting power of the eye by?
Patient Selection for Refractive Surgery Indian Medical PG Practice Questions and MCQs
Question 1: 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 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: 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: Which of the following is TRUE about screening for Trichomonas vaginalis?
- A. Urine samples are inadequate for testing
- B. Culture is no longer used for diagnosis
- C. NAAT is recommended for screening high-risk women (Correct Answer)
- D. Wet mount microscopy has sensitivity >95%
Explanation: ***NAAT is recommended for screening high-risk women*** - **Nucleic Acid Amplification Tests (NAATs)** are highly sensitive and specific for detecting *Trichomonas vaginalis*, making them the preferred method for screening in high-risk populations due to their superior performance over traditional methods. - Screening high-risk women (e.g., those with multiple sexual partners, other STIs, or in areas with high prevalence) with NAATs helps in early detection and treatment, which is crucial for preventing further transmission and complications. *Urine samples are inadequate for testing* - **Urine samples** can indeed be used for *Trichomonas vaginalis* testing, particularly with NAATs, as they provide an alternative to vaginal swabs and are often preferred for their ease of collection and non-invasiveness. - While less sensitive than vaginal swabs for microscopy or culture, **NAATs performed on urine** have good sensitivity and specificity, making them a common option. *Culture is no longer used for diagnosis* - **Culture (e.g., InPouch TV system)** is still considered a **gold standard** for *Trichomonas vaginalis* diagnosis due to its high sensitivity and ability to detect viable organisms, especially when NAATs are not available or for confirming ambiguous results. - It is particularly useful in cases where organisms are present in low numbers or in settings where resources for advanced molecular testing are limited, though it is **less rapid** than NAATs. *Wet mount microscopy has sensitivity >95%* - **Wet mount microscopy** is an inexpensive and rapid diagnostic method, but its sensitivity for detecting *Trichomonas vaginalis* is **relatively low**, typically ranging from **50-70%**, not >95%. - The sensitivity of wet mounts is highly dependent on the **operator's skill**, the concentration of organisms, and the time elapsed since sample collection, making it prone to false negatives.
Question 5: Which of the following statements about conjunctival lesions is NOT true?
- A. Arise from any part of conjunctiva
- B. Can cause Astigmatism
- C. Surgery is treatment of choice (Correct Answer)
- D. UV exposure is risk factor
Explanation: ***Surgery is treatment of choice*** - While surgery can be used to treat conjunctival lesions, it is not always the **treatment of choice**, especially for smaller, asymptomatic lesions like **pinguecula** which may only require observation and lubrication. - Many conjunctival lesions, such as uncomplicated **pterygium** or **pinguecula**, are managed conservatively unless they cause significant symptoms, vision impairment, or cosmetic concerns. *Arise from any part of conjunctiva* - **Conjunctival lesions** can indeed arise from various parts of the conjunctiva, including the palpebral, bulbar, and forniceal conjunctiva. - For example, **pterygium** typically arises from the bulbar conjunctiva, while **pinguecula** also originates in the bulbar conjunctiva, specifically in the interpalpebral fissure. *Can cause Astigmatism* - Larger **conjunctival lesions**, particularly a **pterygium** that encroaches onto the cornea, can induce or alter astigmatism. - The growth of the lesion can change the **curvature of the cornea**, leading to optical distortion and astigmatism. *UV exposure is risk factor* - **Ultraviolet (UV) light exposure** is a well-established risk factor for the development of many conjunctival lesions, including **pterygium** and **pinguecula**. - Chronic UV exposure leads to **elastotic degeneration** of the conjunctival collagen and is thought to play a key role in the pathogenesis of these growths.
Question 6: 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 7: A lady wants LASIK surgery for her daughter. All the following are indications for performing LASIK surgery, except:
- A. Stable refraction for 1 year
- B. Corneal thickness of 600 microns
- C. Age of 15 years (Correct Answer)
- D. Myopia of 4 Diopters
Explanation: ***Age of 15 years*** - LASIK surgery is generally not recommended for individuals under the age of 18, as their eyes and **refractive error** are still developing and stabilizing. - Performing LASIK on a 15-year-old could lead to **regression** of the refractive correction as the eye continues to grow. *Myopia of 4 Diopters* - A **myopia** of 4 Diopters (D) falls within the treatable range for LASIK, which can effectively correct moderate degrees of nearsightedness. - This is a common indication for individuals seeking freedom from glasses or contact lenses. *Stable refraction for 1 year* - **Stable refraction** for at least one year is a crucial criterion for LASIK, ensuring that the patient's prescription is unlikely to change significantly post-surgery. - Unstable refraction could result in suboptimal visual outcomes and the need for further correction. *Corneal thickness of 600 microns* - A **corneal thickness** of 600 microns is considered well within the safe range for LASIK surgery, allowing sufficient residual stromal bed after flap creation and ablation. - Adequate corneal thickness is essential to prevent complications such as **corneal ectasia**.
Question 8: A lady wants LASIK surgery for her daughter. She asks for your opinion. All the following things are suitable for performing LASIK surgery except:
- A. Myopia of 4 Diopters
- B. Age of 15 years (Correct Answer)
- C. Stable refraction for 1 year
- D. Corneal thickness of 600 microns
Explanation: ***Age of 15 years*** - LASIK surgery is generally not recommended for individuals under the age of 18 because their **refractive error** may still be changing. - Ensuring **refractive stability** is crucial for long-term success of the procedure. *Myopia of 4 Diopters* - This level of **myopia** (nearsightedness) is well within the treatable range for LASIK surgery. - LASIK can effectively correct moderate myopia for improved vision. *Stable refraction for 1 year* - **Refractive stability** for at least one year is a critical prerequisite for LASIK, indicating that the patient's prescription is no longer changing significantly. - This stability ensures that the surgical correction will be lasting and accurate. *Corneal thickness of 600 microns* - A corneal thickness of 600 microns is considered **more than adequate** for LASIK surgery, as it allows for the creation of a corneal flap and subsequent ablation without compromising corneal integrity. - The minimum required corneal thickness typically falls around 500 microns, with values above this being favorable.
Question 9: Which is an example of Simple Myopic Astigmatism?
- A. +2.00 sphere
- B. +1.00 -3.00 × 90°
- C. -2.00 sphere
- D. plano -2.00 × 90° (Correct Answer)
Explanation: ***plano -2.00 × 90°*** - This prescription indicates a **spherical equivalent of zero (plano)** in one meridian and **-2.00 diopters of myopia** in the meridian 90 degrees away. - This perfectly fits the definition of **simple myopic astigmatism**, where one principal meridian is emmetropic and the other is myopic. *+2.00 sphere* - This prescription represents **simple hyperopia**, meaning the eye is **farsighted** but without any astigmatism. - All light rays focus behind the retina, and there is no difference in refractive power between the principal meridians. *-2.00 sphere* - This represents **simple myopia**, where the eye is **nearsighted** but without any astigmatism. - All light rays focus in front of the retina, and there is no difference in refractive power between the principal meridians. *+1.00 -3.00 × 90°* - This prescription is an example of **mixed astigmatism**, where one principal meridian is hyperopic (+1.00 D) and the other is myopic (-2.00 D, calculated as +1.00 + [-3.00]). - This differs from simple myopic astigmatism where one meridian is emmetropic.
Question 10: 1mm change in axial length of the eyeball would change the refracting power of the eye by?
- A. 1D
- B. 2D
- C. 3D (Correct Answer)
- D. 4D
Explanation: ***3D*** - A 1mm change in the **axial length** of the eyeball leads to an approximate **3 diopter (D) change** in the refractive power of the eye. - This relationship is crucial for understanding **refractive errors** like myopia (if the eyeball is too long) or hyperopia (if it's too short). *1D* - A 1D change in refractive power corresponds to a much larger change in the **focal length** of the eye, not typically 1mm in axial length. - This value is too small to reflect the significant impact of a 1mm axial length alteration on the eye's focusing ability. *2D* - While a direct relationship exists, 2D is an **underestimation** of the actual refractive change caused by a 1mm alteration in axial length. - This value would imply a less sensitive optical system than the human eye. *4D* - A 4D change would represent an **overestimation** of the refractive power change for a 1mm alteration in axial length. - Such a high value is generally seen with more substantial anatomical variations or surgical interventions.
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