Scleral Contact Lenses — MCQs
Scleral Expansion Bands are used in the management of:
The primary indication for collagen cross-linking is:
Thickest portion of sclera is -
All of the following are true about Keratoconus, except:
Maximum correction of myopia can be done by?
A patient with contact lens use for the past 2 years presents with the ocular findings shown in the image below. What is the most probable diagnosis?
What is the power of lens attached to this instrument to visualize the entire retina?
What is the most common type of cataract found in a newborn?
The Fincham test is used to diagnose which of the following conditions?
Where is the strongest attachment of the zonule found?
Scleral Contact Lenses Indian Medical PG Practice Questions and MCQs
Question 1: Scleral Expansion Bands are used in the management of:
- A. Astigmatism
- B. Keratoconus
- C. Presbyopia (Correct Answer)
- D. Myopia
Explanation: ***Presbyopia*** - **Scleral expansion bands** are a surgical treatment strategy designed to restore the eye's ability to accommodate by altering the biomechanics of the sclera and ciliary body. - They aim to improve the range of motion of the ciliary body, thereby allowing the **lens to change shape** more effectively for near vision in **presbyopic** patients. *Astigmatism* - **Astigmatism** is primarily caused by an **irregularly shaped cornea** or lens, leading to blurred vision at all distances. - It is typically managed with corrective lenses (glasses or contact lenses) or refractive surgeries like **LASIK** or **PRK**, which reshape the cornea. *Keratoconus* - **Keratoconus** is a progressive eye disease where the **cornea thins** and bulges into a cone-like shape, causing distorted vision. - Treatments include rigid gas permeable contact lenses, **corneal collagen cross-linking** to halt progression, and in severe cases, corneal transplant. *Myopia* - **Myopia**, or nearsightedness, occurs when the eye focuses images in front of the retina, often due to an **elongated eyeball** or excessive corneal curvature. - It is commonly corrected with concave lenses, contact lenses, or refractive surgeries such as **LASIK** or **PRK** to flatten the cornea.
Question 2: The primary indication for collagen cross-linking is:
- A. Pellucid marginal degeneration
- B. Corneal ectasia after refractive surgery
- C. Progressive corneal ectasia
- D. Keratoconus (Correct Answer)
Explanation: ***Keratoconus*** - *Keratoconus* is a progressive disorder causing corneal thinning and a conical shape, leading to vision distortion. - *Collagen cross-linking (CXL)* is primarily indicated to halt the progression of keratoconus by strengthening corneal collagen fibers through riboflavin and UV-A light exposure. - This is the **most common and primary indication** for CXL, as it is FDA-approved and evidence-based for progressive keratoconus. *Pellucid marginal degeneration* - Pellucid marginal degeneration (PMD) involves a band of corneal thinning, usually in the inferior periphery, causing high astigmatism. - While CXL can be considered, PMD is less common and often managed with contact lenses or surgical techniques like crescentic resection. *Corneal ectasia after refractive surgery* - Corneal ectasia after refractive surgery is a complication where the cornea thins and bulges following procedures like LASIK. - CXL can be used to stabilize this condition, but it is a secondary indication, as keratoconus is the most common primary ectatic disease. *Progressive corneal ectasia* - Progressive corneal ectasia is a broad term describing any corneal thinning and bulging that worsens over time. - While keratoconus is a form of progressive corneal ectasia, the question asks for the primary indication, which points to the most common specific condition.
Question 3: Thickest portion of sclera is -
- A. Posterior pole (Correct Answer)
- B. Posterior to rectus muscle insertion
- C. Anterior to rectus muscle insertion
- D. Limbus
Explanation: ***Posterior pole*** - The sclera is thickest at the **posterior pole**, particularly around the optic nerve entrance, where it provides structural support for the optic nerve head. - This region forms a robust protective layer for the delicate structures within the posterior segment of the eye. *Posterior to rectus muscle insertion* - While the sclera is relatively thick in this region compared to the equator, it is generally thinner than the posterior pole. - The rectus muscles insert approximately 5-7 mm from the limbus, and their insertion points represent thinner areas of the sclera. *Anterior to rectus muscle insertion* - This area, encompassing the region between the limbus and the rectus muscle insertions, is generally thinner than the posterior pole. [1] - The sclera gradually thickens towards the posterior pole and thins towards the limbus. [1] *Limbus* - The **limbus** is the thinnest part of the sclera, where it transitions into the transparent cornea. [1] - This **corneoscleral junction** is a crucial anatomical landmark but represents the thinnest portion of the scleral tissue.
Question 4: All of the following are true about Keratoconus, except:
- A. Astigmatism
- B. Increased curvature of cornea and Astigmatism
- C. Thick cornea (Correct Answer)
- D. Fleischer's ring
Explanation: ***Thick cornea*** - Keratoconus is characterized by **progressive corneal thinning** and weakening, not thickening. - This corneal thinning leads to a conical protrusion, causing significant visual distortion and irregular astigmatism. *Increased curvature of cornea and Astigmatism* - Keratoconus features **increased corneal curvature** with progressive steepening into a cone-shaped configuration. - This results in **irregular astigmatism**, a hallmark feature causing distorted vision at all distances. *Astigmatism* - **Irregular astigmatism** is a cardinal feature of keratoconus due to the asymmetric corneal shape. - Causes blurred and distorted vision that is difficult to correct with spectacles alone. *Fleischer's ring* - **Fleischer's ring** is an iron deposit ring at the base of the cone in keratoconus, visible on slit-lamp examination. - It represents hemosiderin deposition in the basal epithelial cells and is a characteristic clinical sign of keratoconus.
Question 5: 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 6: A patient with contact lens use for the past 2 years presents with the ocular findings shown in the image below. What is the most probable diagnosis?
- A. Trachoma
- B. Giant Papillary conjunctivitis (Correct Answer)
- C. Ocular Surface Squamous Neoplasia (OSSN)
- D. Vernal Keratoconjunctivitis
Explanation: ***Giant Papillary conjunctivitis*** - The image shows **large, elevated papillae** on the **tarsal conjunctiva**, which are characteristic findings of giant papillary conjunctivitis. - This condition is common among **contact lens wearers**, caused by chronic mechanical irritation and an allergic response to lens material or deposits. *Trachoma* - Trachoma is a **chronic infectious disease** caused by *Chlamydia trachomatis*, leading to scarring of the conjunctiva. - It typically presents with **follicles** in the early stages, followed by **scarring** and **pannus formation**, not the large papillae seen here. *Ocular Surface Squamous Neoplasia (OSSN)* - OSSN refers to a spectrum of conditions from **dysplasia to squamous cell carcinoma** affecting the conjunctiva or cornea. - It usually presents as a **gelatinous, fleshy, or leukoplakic lesion**, often at the limbus, which is distinct from the diffuse papillae shown. *Vernal Keratoconjunctivitis* - Vernal keratoconjunctivitis (VKC) is a **severe form of allergic conjunctivitis** but primarily affects children and young adults with a history of atopy. - While it can cause large papillae (cobblestone papillae), it is not specifically associated with contact lens wear and usually has other systemic allergic manifestations.
Question 7: What is the power of lens attached to this instrument to visualize the entire retina?
- A. 20 D (Correct Answer)
- B. 58 D
- C. 78 D
- D. 90 D
Explanation: ***20 D*** - The image depicts a **binocular indirect ophthalmoscope (BIO)**, which is used for wide-field examination of the retina. - The **20 D lens** is the **most commonly used condensing lens** with a BIO for visualizing the entire retina. - It provides the **widest field of view** (approximately 45-50 degrees) with adequate magnification, making it ideal for comprehensive peripheral retinal examination. - Other standard BIO lenses include 14 D, 28 D, and 30 D, but **20 D offers the optimal balance** of field of view and magnification for complete retinal visualization. *58 D* - A **58 D lens** is not a standard condensing lens used with binocular indirect ophthalmoscopy. - While high-power lenses can be used with various ophthalmoscopic techniques, they are not conventional for BIO examination of the entire retina. *78 D* - A **78 D lens** is typically used with a **slit lamp biomicroscope** for a magnified view of the posterior pole and macular details. - It does not provide the wide-field view necessary for visualizing the **entire retina** when used with a BIO. - This lens is excellent for detailed examination of the optic disc and macula but has a limited field of view. *90 D* - A **90 D lens** is also primarily used with a **slit lamp biomicroscope** for excellent magnification of the macula and optic nerve head. - It provides a high-resolution, magnified view of a *limited area*, making it unsuitable for a comprehensive survey of the entire retina. - Like the 78 D, it's designed for detailed central retinal examination, not peripheral screening.
Question 8: What is the most common type of cataract found in a newborn?
- A. Zonular (Correct Answer)
- B. Nuclear
- C. Snowflake
- D. Cortical
Explanation: **Explanation:** **Zonular (Lamellar) Cataract** is the most common type of congenital cataract. It is characterized by opacification of a specific layer (zone) of the lens fibers, typically surrounding a clear embryonic nucleus. This occurs due to a transient environmental or nutritional insult (such as Vitamin D deficiency or hypocalcemia) during a specific stage of lens development. Because it often allows some light to pass through the clear areas, it is frequently associated with relatively good visual prognosis if managed early. **Analysis of Incorrect Options:** * **Nuclear Cataract:** While common in age-related (senile) cataracts, it is less frequent in newborns. It involves the central core of the lens and is often associated with intrauterine infections like Rubella. * **Snowflake Cataract:** This is a classic finding in **Diabetes Mellitus** (specifically juvenile diabetes). It consists of subcapsular white opacities and is not a standard congenital presentation. * **Cortical Cataract:** This is typically an age-related change characterized by "cuneiform" or wedge-shaped opacities in the lens cortex. It is rarely seen as a primary congenital finding in newborns. **Clinical Pearls for NEET-PG:** * **Most common cause of Congenital Cataract:** Idiopathic (followed by genetic/hereditary factors). * **Most common infection:** Rubella (presents as "Pearls in the center" or dense nuclear cataract). * **Oil droplet cataract:** Classic for Galactosemia. * **Sunflower cataract:** Seen in Wilson’s disease (Chalcosis). * **Management:** If the cataract is visually significant (central opacity >3mm), surgery (Lens aspiration + Primary Posterior Capsulotomy + Anterior Vitrectomy) is ideally performed within the first 4–6 weeks of life to prevent amblyopia.
Question 9: The Fincham test is used to diagnose which of the following conditions?
- A. Open angle glaucoma
- B. Cataract (Correct Answer)
- C. Mucopurulent conjunctivitis
- D. Acute angle closure glaucoma
Explanation: **Explanation:** The **Fincham Test** (also known as the Fincham’s Stenopeic Slit Test) is a clinical method used to differentiate between halos caused by **corneal edema** (as seen in Acute Angle Closure Glaucoma) and those caused by **immature cataract**. 1. **Why Cataract is correct:** In an immature cataract, the opacities in the crystalline lens act as a diffraction grating. When a stenopeic slit is passed across the pupil, the halos **break up into segments** or rotate. This positive Fincham test confirms the halos are lenticular (cataractous) in origin. 2. **Why Acute Angle Closure Glaucoma (AACG) is incorrect:** In AACG, halos are caused by corneal edema (fluid in the epithelium). When the stenopeic slit is moved across the pupil, these halos **remain intact** and do not break up. 3. **Why Open Angle Glaucoma & Mucopurulent Conjunctivitis are incorrect:** These conditions do not typically present with the specific "halo" phenomenon that requires differentiation via Fincham’s test. Mucopurulent conjunctivitis may cause blurred vision due to discharge, but this clears with blinking. **Clinical Pearls for NEET-PG:** * **Mechanism:** Halos in cataract are due to diffraction by lens fibers; in glaucoma, they are due to diffraction by edematous corneal epithelial cells. * **Emsley’s Rule:** Another name for the principle that glaucomatous halos are circular and intact, while cataractous halos are fragmented. * **Differential Diagnosis of Halos:** Always consider AACG, Cataract, and sometimes contact lens overwear (Sattler’s veil).
Question 10: Where is the strongest attachment of the zonule found?
- A. Equator
- B. Just anterior to the equator (Correct Answer)
- C. Posterior to the equator
- D. Posterior lobe
Explanation: **Explanation:** The **Zonules of Zinn** (suspensory ligaments of the lens) are delicate fibers that bridge the ciliary body and the lens capsule, holding the lens in position and enabling accommodation. These fibers insert into the lens capsule in a specific distribution around the equator. **Why Option B is Correct:** The zonular fibers do not insert at a single point but rather in a broad band. Anatomical studies and tension tests demonstrate that the **strongest and thickest attachment** occurs in the **pre-equatorial (anterior)** region, approximately 1.5 mm anterior to the equator. This area provides the primary structural stability required to transmit the pull of the ciliary muscle to the lens during accommodation. **Analysis of Incorrect Options:** * **A. Equator:** While some fibers (equatorial zonules) do attach directly to the equator, they are fewer in number and less robust than the anterior group. * **C. Posterior to the equator:** Posterior zonules attach about 1.25 mm behind the equator. While important for stability, they are generally thinner and less numerous than the anterior fibers. * **D. Posterior lobe:** This is not a standard anatomical term for lens zonular insertion. **Clinical Pearls for NEET-PG:** * **Composition:** Zonules are composed of **Fibrillin-1**. Mutations in the FBN1 gene lead to **Marfan Syndrome**, causing ectopia lentis (typically superotemporal subluxation). * **Accommodation:** When the ciliary muscle contracts, the zonules **relax**, allowing the lens to become more spherical (increasing refractive power). * **Surgical Relevance:** During cataract surgery (Phacoemulsification), the strength of these attachments is vital. In conditions like **Pseudoexfoliation Syndrome**, zonular weakness can lead to lens instability or "phacodonesis."
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