Diseases of the Lens — MCQs

Diseases of the Lens Indian Medical PG Practice Questions and MCQs

Question 221: Complicated cataract is associated with which of the following conditions?

A. Uveitis
B. Retinitis pigmentosa
C. Degenerative myopia
D. All of the above (Correct Answer)

Explanation: ### Explanation **Concept:** A **complicated cataract** refers to opacification of the lens resulting from metabolic disturbances caused by intraocular diseases. The lens depends on the aqueous and vitreous humor for nutrition; any chronic inflammation or degenerative process in the eye alters this environment, leading to the accumulation of toxins and interference with lens metabolism. **Why "All of the Above" is Correct:** 1. **Uveitis (Chronic Iridocyclitis):** This is the most common cause. Persistent inflammation leads to the release of inflammatory mediators and proteins into the aqueous humor, which damages the lens epithelium. 2. **Retinitis Pigmentosa (RP):** This retinal dystrophy is classically associated with **posterior subcapsular cataracts (PSC)**. The mechanism involves the migration of metabolic byproducts or inflammatory cells from the degenerating retina toward the posterior pole of the lens. 3. **Degenerative Myopia:** High myopia causes vitreous liquefaction and chorioretinal degeneration. These degenerative changes alter the nutritional supply to the lens, frequently resulting in early-onset posterior subcapsular or nuclear opacities. **Clinical Pearls for NEET-PG:** * **Morphology:** Complicated cataracts typically begin as a **"Bread-crumb" appearance** (polychromatic luster) in the posterior subcapsular region. * **Characteristic Sign:** The presence of a **polychromatic luster** (iridescence of reds, greens, and blues) is a pathognomonic finding on slit-lamp examination. * **Other Causes:** Retinal detachment (long-standing), intraocular tumors (e.g., retinoblastoma), and absolute glaucoma. * **Surgical Note:** Prognosis after surgery depends on the health of the underlying retina/uvea, not just the successful removal of the lens.

Question 222: In complicated cataract, opacity develops in which part of the lens?

A. Anterior capsule
B. Nucleus
C. Posterior subcapsular (Correct Answer)
D. Cortical

Explanation: **Explanation:** **Complicated cataract** refers to the opacification of the lens secondary to intraocular diseases, most commonly chronic anterior uveitis. **Why Posterior Subcapsular (PSC) is correct:** The lens is an avascular structure that derives its nutrition from the aqueous humor. In conditions like chronic uveitis, the inflammatory mediators and toxins present in the aqueous humor interfere with lens metabolism. The **posterior pole** is the most vulnerable site because it is the thinnest part of the lens capsule and lacks a protective epithelial layer (which is present anteriorly). This leads to the accumulation of fluid and denatured proteins, resulting in a characteristic **"bread-crumb"** or **polychromatic luster** appearance in the posterior subcapsular region. **Why other options are incorrect:** * **Anterior capsule:** Opacities here are typically associated with trauma, pseudoexfoliation, or "Glaukomflecken" (post-acute congestive glaucoma). * **Nucleus:** Nuclear cataracts are primarily age-related (senile) due to the compaction and sclerosis of central lens fibers. * **Cortical:** Cortical cataracts are usually age-related or metabolic (e.g., diabetes) and present as "cuneiform" or wedge-shaped opacities. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause:** Chronic Anterior Uveitis. * **Earliest sign:** A **polychromatic luster** (iridescence) seen at the posterior pole. * **Appearance:** Often described as a **"bread-crumb"** appearance. * **Other causes:** High myopia, Retinitis Pigmentosa, and long-term steroid use (though steroid-induced PSC is technically a drug-induced cataract, it mimics the morphology).

Question 223: A 70-year-old man presents with deterioration of vision 3 weeks after cataract extraction and intraocular lens implantation. Slit lamp examination shows honeycomb maculopathy and Fluorescein angiography shows 'flower petal' hyperfluorescence. What is the most likely diagnosis?

A. Age-related macular degeneration
B. Central serous retinopathy
C. Macular dystrophy
D. Cystoid macular edema (Correct Answer)

Explanation: ### Explanation The correct diagnosis is **Cystoid Macular Edema (CME)**, specifically known as **Irvine-Gass Syndrome** when it occurs following cataract surgery. **Why it is correct:** CME involves the accumulation of fluid in the outer plexiform (Henle’s) and inner nuclear layers of the retina. The classic clinical presentation occurs 2–8 weeks post-cataract surgery. * **Honeycomb appearance:** On slit-lamp biomicroscopy, the fluid-filled microcysts create a characteristic honeycomb pattern. * **Flower-petal appearance:** On Fluorescein Angiography (FFA), leakage from perifoveal capillaries accumulates in the radial arrangement of Henle’s layer, creating a pathognomonic "flower petal" or "stellate" hyperfluorescence. **Why other options are incorrect:** * **Age-related Macular Degeneration (ARMD):** Presents with drusen (Dry) or choroidal neovascularization (Wet). FFA would show a "smoke-stack" or "puddle" pattern in classic CNVM, not a petaloid pattern. * **Central Serous Retinopathy (CSR):** Typically affects younger males and presents with a localized sensory retinal detachment. FFA shows a "smoke-stack" or "ink-blot" appearance. * **Macular Dystrophy:** These are usually bilateral, genetic conditions (e.g., Best’s disease) presenting at a much younger age with specific patterns like an "egg-yolk" lesion. **NEET-PG High-Yield Pearls:** * **Most common cause of decreased vision after uncomplicated cataract surgery:** CME (Irvine-Gass Syndrome). * **Gold Standard Investigation:** Optical Coherence Tomography (OCT) – shows intraretinal cystic spaces. * **Prophylaxis/Treatment:** Topical NSAIDs (e.g., Nepafenac or Ketorolac) and Corticosteroids. * **Risk Factors:** Posterior capsular rupture, vitreous loss, diabetes, and uveitis.

Question 224: Which of the following statements is NOT true about the lens?

A. The pre-equatorial part of the lens capsule is the thickest, measuring 22-23 μm.
B. The anterior epithelium is composed of a single layer of cuboidal cells.
C. The posterior epithelium in postnatal life is made up of cuboidal epithelium. (Correct Answer)
D. Relative dehydration in the cortex is due to the action of the Na+-K+ ATPase pump.

Explanation: ### Explanation **1. Why Option C is the correct answer (The False Statement):** In embryology, the lens vesicle consists of an anterior and a posterior wall of cuboidal epithelium. However, during development, the cells of the **posterior wall** elongate to form the primary lens fibers, which fill the cavity of the vesicle. Consequently, in **postnatal life**, the posterior epithelium is **absent**. The lens only possesses an anterior epithelium, which continues to the equator. **2. Analysis of Incorrect Options (True Statements):** * **Option A:** The lens capsule is a basement membrane, and its thickness varies. The **pre-equatorial** (and post-equatorial) regions are indeed the thickest (approx. 21–23 μm) to provide structural support for zonular attachments. The posterior pole is the thinnest (~4 μm). * **Option B:** The anterior epithelium is a single layer of **cuboidal cells**. These cells are metabolically active and are responsible for the continuous production of new lens fibers at the equatorial "germinal zone." * **Option C:** The lens maintains a state of **relative dehydration** (66% water) to ensure transparency. This is primarily achieved by the **Na⁺-K⁺ ATPase pump** located in the anterior epithelium, which actively pumps sodium out (followed by water) and potassium in. **Clinical Pearls for NEET-PG:** * **Thickest part of the capsule:** Pre-equatorial region. * **Thinnest part of the capsule:** Posterior pole (Clinical significance: High risk of rupture during Phacoemulsification). * **Lens Protein:** Highest protein content in the body (33%). Crystallins are the major proteins. * **Metabolism:** 90% of energy is derived from **Anaerobic Glycolysis**. * **Sutures:** The fetal nucleus shows an upright **'Y'** suture anteriorly and an inverted **'Y'** suture posteriorly.

Question 225: Radiation-induced cataract is classified as which type?

A. Shield cataract
B. Anterior polar cataract
C. Posterior subcapsular cataract (Correct Answer)
D. Alport syndrome

Explanation: **Explanation:** **Radiation-induced cataract** typically presents as a **Posterior Subcapsular Cataract (PSC)**. The lens is one of the most radiosensitive tissues in the body. When exposed to ionizing radiation (X-rays, gamma rays), the germinal epithelium at the lens equator is damaged. These damaged cells migrate posteriorly toward the posterior pole, where they fail to differentiate into normal lens fibers and instead form opacities under the posterior capsule. **Analysis of Options:** * **A. Shield cataract:** This is a characteristic dense, plaque-like anterior subcapsular opacity seen in patients with **Atopic Dermatitis** (Atopic Cataract). * **B. Anterior polar cataract:** These are usually **congenital** and often associated with persistent pupillary membranes or intrauterine inflammation. * **D. Alport syndrome:** This genetic condition is classically associated with **Anterior Lenticonus** (a cone-shaped protrusion of the lens) rather than a specific radiation-induced morphology. **High-Yield Clinical Pearls for NEET-PG:** * **Infrared Radiation:** Causes "Glass-blower’s cataract" or "True Exfoliation" of the anterior capsule. * **Steroid-induced Cataract:** Also presents as **Posterior Subcapsular Cataract (PSC)**. * **Electric Shock:** Typically results in **Anterior Subcapsular** opacities. * **Sunflower Cataract:** Seen in **Wilson’s Disease** (Copper deposition). * **Snowflake Cataract:** Seen in **Diabetes Mellitus**. * **Christmas Tree Cataract:** Seen in **Myotonic Dystrophy**.

Question 226: Complete unilateral congenital cataract should preferably be operated:

A. Within a few weeks of birth (Correct Answer)
B. At the age of 6 months
C. At the age of 2 years
D. At the age of 5 years

Explanation: **Explanation:** The timing of surgery in congenital cataracts is critical to prevent **stimulus-deprivation amblyopia**. In a complete unilateral cataract, the brain receives no visual input from the affected eye, leading to rapid and permanent cortical suppression. **Why Option A is Correct:** The "critical period" for visual development is most sensitive during the first few months of life. For **unilateral** cases, surgery is ideally performed **within 4–6 weeks of birth**. Delaying surgery beyond this window leads to irreversible amblyopia and sensory nystagmus, resulting in poor visual prognosis even if the surgery is technically successful later. **Why Other Options are Incorrect:** * **Option B (6 months):** By this age, the critical period for establishing binocularity is significantly compromised. While bilateral cataracts can sometimes wait slightly longer (up to 10 weeks), 6 months is too late for a unilateral case. * **Options C & D (2 and 5 years):** Operating at these ages is considered "late." The eye will have already developed dense amblyopia, and the surgery would be primarily for cosmetic purposes rather than functional vision. **Clinical Pearls for NEET-PG:** * **Bilateral Complete Cataracts:** Should be operated on within **8–10 weeks** of birth. * **IOL Implantation:** Generally avoided in infants <6 months due to changing axial length and high inflammatory response; the child is managed with aphakic glasses or contact lenses initially. * **Most Common Cause:** Most unilateral congenital cataracts are sporadic (idiopathic), while bilateral cases are often hereditary (Autosomal Dominant) or associated with metabolic disorders (e.g., Galactosemia). * **Visual Rehabilitation:** Surgery is only the first step; aggressive patching of the "good" eye is mandatory post-operatively to treat amblyopia.

Question 227: Presbyopia occurs as a result of the following except?

A. Loss of elasticity of the capsule
B. Sclerosis of fibres within the lens
C. Reduced anterior displacement of the lens during accommodation (Correct Answer)
D. Reduced contraction of the ciliary muscle

Explanation: **Explanation:** Presbyopia is a physiological age-related decline in the eye's accommodative power, making it difficult to focus on near objects. The correct answer is **C** because, during normal accommodation, the lens actually moves **anteriorly** (forward). In presbyopia, this displacement is not necessarily "reduced" as a primary cause; rather, the failure lies in the lens's inability to change its shape (curvature). **Why Option C is the correct answer (The "Except"):** The primary mechanism of accommodation (Helmholtz theory) involves ciliary muscle contraction, which relaxes the zonules, allowing the lens to become more spherical. While the lens does move slightly forward during this process, "reduced anterior displacement" is not a recognized physiological cause of presbyopia. The condition is fundamentally a failure of **deformability**, not displacement. **Analysis of Incorrect Options (Causes of Presbyopia):** * **A. Loss of elasticity of the capsule:** With age, the lens capsule becomes thicker and less elastic, losing its ability to mold the lens into a convex shape. * **B. Sclerosis of lens fibres:** This is the most significant factor. As new lens fibers are added throughout life, the older central fibers become compressed and dehydrated (lenticular sclerosis), making the lens rigid. * **C. Reduced contraction of ciliary muscle:** Age-related atrophy and fatty infiltration of the ciliary muscle reduce its contractile power, contributing to the failure of the accommodative reflex. **Clinical Pearls for NEET-PG:** * **Definition:** Presbyopia is considered to have occurred when the near point of distinct vision recedes beyond the normal reading distance (usually >25 cm). * **Correction:** It is corrected using **convex (plus) lenses**. * **High-Yield Fact:** In patients with **uncorrected myopia**, presbyopia may appear later because their far point is already near. Conversely, **hypermetropes** experience symptoms earlier. * **Duane’s Graph:** This illustrates the age-related decline in the amplitude of accommodation.

Question 228: Bilateral inferior subluxation of the lens is typically seen in which of the following conditions?

A. Marfan syndrome
B. Homocystinuria (Correct Answer)
C. Hyperinsulinemia
D. Ocular trauma

Explanation: **Explanation:** The correct answer is **Homocystinuria**. Ectopia lentis (lens subluxation) is a hallmark of several systemic disorders, and the direction of displacement is a high-yield clinical differentiator in NEET-PG. **1. Why Homocystinuria is correct:** Homocystinuria is an autosomal recessive metabolic disorder caused by a deficiency of the enzyme **cystathionine beta-synthase**. This leads to an accumulation of homocysteine, which interferes with the cross-linking of fibrillin in the zonular fibers. The zonules become brittle and disintegrate, typically resulting in a **downward and inward (inferior/inferonasal)** subluxation. A key clinical feature is that the zonules are often absent or broken, and accommodation is lost. **2. Why the other options are incorrect:** * **Marfan Syndrome:** This is the most common cause of heritable ectopia lentis. However, the subluxation is typically **upward and outward (superotemporal)**. The zonules usually remain intact (though stretched). * **Hyperinsulinemia:** This is not associated with lens subluxation. It is more commonly linked to refractive changes or metabolic cataracts. * **Ocular Trauma:** While trauma is the **most common overall cause** of lens subluxation, it is usually unilateral and the direction depends on the point of impact rather than a systemic pattern. **High-Yield Clinical Pearls for NEET-PG:** * **Marfan vs. Homocystinuria:** Remember **"M"** for Marfan = **"More"** (Upward); **"H"** for Homocystinuria = **"Humble"** (Downward). * **Inheritance:** Marfan is Autosomal Dominant; Homocystinuria is Autosomal Recessive. * **Systemic Risk:** Patients with Homocystinuria have a high risk of **thromboembolic episodes**, especially during general anesthesia. * **Other causes of Inferior Subluxation:** Weill-Marchesani syndrome (though lenses are typically small and spherical—microspherophakia).

Question 229: The epithelium is absent in the lens on which surface?

A. Anterior surface
B. Posterior surface (Correct Answer)
C. Anterior pole
D. At zonular attachment

Explanation: **Explanation:** The lens is a unique avascular, transparent structure enclosed within a basement membrane called the lens capsule. To understand the distribution of the epithelium, one must look at the **embryological development** of the lens. **Why the Posterior Surface is the Correct Answer:** During the development of the lens vesicle, the cells of the **posterior wall** elongate to form the primary lens fibers. These cells move forward to fill the cavity of the vesicle. Once these primary fibers are formed, the posterior epithelial layer is effectively "used up" and disappears. Consequently, in a mature lens, the subcapsular epithelium is present **only on the anterior surface** and the equatorial region, but is **completely absent on the posterior surface.** **Analysis of Incorrect Options:** * **Anterior Surface & Anterior Pole:** These areas are covered by a single layer of cuboidal epithelium (the anterior lens epithelium) located just deep to the capsule. These cells are metabolically active and responsible for the life-long growth of the lens. * **At Zonular Attachment:** The zonules of Zinn attach to the lens capsule in the equatorial and para-equatorial regions. The epithelium is not only present here but is at its most mitotically active state (the "germinal zone"), where cells divide and differentiate into new lens fibers. **High-Yield Clinical Pearls for NEET-PG:** * **Lens Capsule:** It is the thickest basement membrane in the human body; it is thickest at the pre-equatorial region and **thinnest at the posterior pole.** * **Metabolism:** The anterior epithelium contains the highest concentration of **Na+/K+-ATPase pumps**, which are crucial for maintaining lens dehydration and transparency. * **Cataract Surgery:** During ECCE or Phacoemulsification, the posterior capsule is left intact. Because it lacks an epithelial layer, it remains clear unless "Elschnig pearls" (migrating cells from the equator) cause Posterior Capsular Opacification (PCO).

Question 230: Which morphological type of cataract is most visually handicapping?

A. Cortical
B. Nuclear
C. Posterior subcapsular (Correct Answer)
D. Zonular

Explanation: **Explanation:** The correct answer is **Posterior Subcapsular Cataract (PSC)**. **1. Why it is the most visually handicapping:** The visual impact of a cataract depends on its proximity to the eye’s nodal point (the optical center). PSC is located at the posterior pole of the lens, directly in the path of converging light rays. Because it lies so close to the nodal point, even a small opacity can cause significant visual distortion. Furthermore, PSC causes **glare** and severe reduction in near vision. This is exacerbated by **miosis** (pupillary constriction) during reading or in bright light, which forces light to pass through the central opacity, further degrading the image. **2. Why other options are incorrect:** * **Cortical Cataract:** These typically present as "cuneiform" (wedge-shaped) opacities in the periphery. They only affect vision when they extend into the pupillary axis. * **Nuclear Cataract:** This involves gradual sclerosis of the lens nucleus. While it causes a "second sight" phenomenon (myopic shift), it progresses slowly and allows for relatively better vision in bright light compared to PSC. * **Zonular (Lamellar) Cataract:** This is a congenital cataract affecting a specific shell of the lens. While it affects vision, it is usually static and less disruptive to functional adult vision than the central, axial opacity of PSC. **Clinical Pearls for NEET-PG:** * **Steroid use:** PSC is the classic type of cataract associated with prolonged systemic or topical corticosteroid therapy. * **Diabetes:** While cortical cataracts are common in diabetics, PSC is also frequently seen. * **Symptoms:** Patients with PSC characteristically complain of **day blindness (Hemeralopia)** and difficulty reading, while patients with nuclear cataracts often experience **night blindness (Nyctalopia)**.

Practice by Chapter

Lens Anatomy and Physiology

Practice Questions

Age-Related Cataract

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Congenital and Developmental Cataracts

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Traumatic Cataract

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Metabolic Cataracts

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Drug-Induced Cataracts

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Cataract Surgery Techniques

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Intraocular Lens Implants

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Complications of Cataract Surgery

Practice Questions

Posterior Capsular Opacification

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Lens Subluxation and Dislocation

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Specialty IOLs

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