Diseases of the Lens — MCQs

Diseases of the Lens Indian Medical PG Practice Questions and MCQs

Question 211: Uniocular polyopia is seen in which stage of cataract?

A. Incipient (Correct Answer)
B. Intumescent
C. Mature
D. Hypermature

Explanation: **Explanation:** **Uniocular polyopia** (seeing multiple images with one eye) is a classic early symptom of cataract, specifically occurring in the **Incipient stage**. **Why Incipient is correct:** In the incipient stage, the lens undergoes irregular changes in its refractive index due to the formation of water clefts and vacuoles (cuneiform cataract) or early nuclear sclerosis. This creates multiple "sectors" within the lens with different refractive powers. When light enters, it is refracted unevenly, focusing on different points on the retina, which the patient perceives as multiple images (polyopia). **Why other options are incorrect:** * **Intumescent:** The lens becomes swollen due to the continued imbibition of water. While vision is significantly blurred, the primary clinical feature is a shallow anterior chamber and the risk of angle-closure glaucoma, rather than polyopia. * **Mature:** The entire lens becomes opaque (pearly white). At this stage, no clear light rays can pass through to be refracted into multiple images; the patient typically only has perception of light (PL) and accurate projection of rays (PR). * **Hypermature:** The lens cortex liquefies (Morgagnian) or the lens shrivels (Sclerotic). The optical integrity is completely lost, making polyopia impossible. **High-Yield Clinical Pearls for NEET-PG:** * **Uniocular Diplopia/Polyopia:** Always think of Incipient Cataract, Subluxated lens, or Keratoconus. * **Second Sight (Index Myopia):** Seen in early nuclear cataract (Incipient stage) where the patient can suddenly read without glasses due to increased refractive power. * **Cupuliform Cataract:** A type of posterior subcapsular cataract that causes significant vision loss in bright light (glare).

Question 212: After radiation-induced injury, in which part of the lens is a cataract typically seen?

A. Anterior cortical
B. Posterior cortical (Correct Answer)
C. Subcapsular
D. Nucleus

Explanation: **Explanation:** The lens is highly sensitive to ionizing radiation. The correct answer is **Posterior cortical** (often specifically presenting as a posterior subcapsular cataract) because of the unique physiology of lens epithelial cells. **Why Posterior Cortical?** When the lens is exposed to radiation, the germinal epithelium at the **equator** is damaged. These damaged cells fail to differentiate properly into clear lens fibers. Instead, they migrate posteriorly toward the posterior pole. Because the lens lacks a mechanism to shed dead cells, these abnormal, opaque cells accumulate under the posterior capsule, forming a characteristic "breadcrumb" or "sandpaper" appearance. **Analysis of Incorrect Options:** * **Anterior cortical:** While some metabolic conditions affect the anterior cortex, radiation damage specifically targets the migrating fibers that culminate at the posterior pole. * **Subcapsular:** While radiation cataracts are technically subcapsular in location, "Posterior cortical" is the more specific anatomical description often used in clinical examinations to denote the migration of damaged fibers. * **Nucleus:** Nuclear cataracts (sclerosis) are typically associated with aging (senile cataract) and oxidative stress, not ionizing radiation. **NEET-PG High-Yield Pearls:** * **Threshold Dose:** The minimum dose to induce a cataract is approximately **2 Gy** (single dose) or **5.5 Gy** (protracted exposure). * **Latency:** There is a latent period between exposure and opacity, which is inversely proportional to the dose received. * **Glassblower's Cataract:** Do not confuse radiation (ionizing) cataracts with Glassblower’s cataract, which is caused by **Infrared (non-ionizing)** radiation and typically involves true exfoliation of the anterior capsule. * **Steroid-Induced Cataract:** Also typically presents as a **Posterior Subcapsular Cataract (PSC)**.

Question 213: What is the best method to prevent infection following cataract surgery?

A. Antibiotic administration (Correct Answer)
B. Shaving of eyebrows
C. Irrigation of the surgical site
D. None of the above

Explanation: **Explanation:** The prevention of postoperative endophthalmitis is a critical aspect of cataract surgery. The correct answer is **Antibiotic administration**, specifically the use of preoperative topical antibiotics and, most importantly, **Povidone-iodine (5%)** application to the conjunctival sac. 1. **Why Antibiotic Administration is Correct:** The primary source of infection in endophthalmitis is the patient’s own commensal flora (e.g., *Staphylococcus epidermidis*). Preoperative topical antibiotics and the application of 5% Povidone-iodine significantly reduce the bacterial load on the ocular surface. Furthermore, the use of **intracameral antibiotics** (like Cefuroxime or Moxifloxacin) at the end of surgery is currently considered the "gold standard" for reducing the risk of endophthalmitis. 2. **Why Other Options are Incorrect:** * **Shaving of eyebrows:** This is an outdated practice. Shaving can cause micro-abrasions that harbor bacteria, actually increasing the risk of infection rather than decreasing it. * **Irrigation of the surgical site:** While irrigation with saline is part of the surgical procedure, it is insufficient on its own to eliminate the microbial flora responsible for serious intraocular infections. **High-Yield Clinical Pearls for NEET-PG:** * **Most common organism** causing acute post-operative endophthalmitis: *Staphylococcus epidermidis*. * **Most common source** of infection: Patient’s own conjunctival and eyelid flora. * **Single most important step** in prophylaxis: Preoperative 5% Povidone-iodine (Betadine) instillation in the conjunctival sac for 3–5 minutes. * **ESCRS Study Gold Standard:** Intracameral Cefuroxime (1mg in 0.1ml) reduces the risk of endophthalmitis by nearly 5-fold.

Question 214: Most old fibres of the lens are located in which part of the lens?

A. Periphery
B. Centre (Correct Answer)
C. Superior portion
D. Inferior portion

Explanation: ### Explanation **Concept and Mechanism:** The crystalline lens is a unique structure that continues to grow throughout life. New lens fibers are constantly produced by the **mitotic division of the lens epithelium** located at the **equator** (periphery). As these new fibers are formed, they are laid down on the outer surface of the existing fibers. Because the lens is enclosed within a capsule, there is no mechanism to shed old cells. Consequently, the older fibers are progressively pushed inward toward the middle. Therefore, the **oldest fibers are found in the center (the embryonic and fetal nuclei)**, while the youngest fibers are located in the superficial cortex. **Analysis of Options:** * **B. Centre (Correct):** As explained, the centripetal growth pattern ensures that the oldest fibers form the dense central core (nucleus) of the lens. * **A. Periphery:** This is where the youngest fibers are located. The subcapsular cortex at the equator is the site of active fiber production. * **C & D. Superior and Inferior portions:** Lens growth is circumferential and symmetrical around the equator. There is no age-related differentiation based on vertical orientation (superior vs. inferior). **Clinical Pearls for NEET-PG:** * **Nuclear Sclerosis:** This is the age-related compaction and hardening of the oldest fibers in the center, leading to a "myopic shift" (Second Sight). * **Lens Sutures:** The meeting points of lens fibers at the poles form the **Y-sutures** (Upright 'Y' anteriorly, Inverted 'Y' posteriorly). * **Metabolism:** The lens is avascular; it derives its nutrition from the aqueous humor via anaerobic glycolysis (90%). * **High-Yield Fact:** The lens has the highest protein content (33%) of any organ in the body, primarily consisting of crystallins.

Question 215: Which of the following can cause cataracts?

A. Hypoparathyroidism
B. Cigarette smoking
C. Non-ionizing radiation
D. All of the above (Correct Answer)

Explanation: **Explanation:** Cataractogenesis is a multifactorial process involving the denaturation of lens proteins and oxidative stress. The correct answer is **All of the above** because each option represents a distinct mechanism of lens opacification. 1. **Hypoparathyroidism:** This leads to **hypocalcemia**. Low serum calcium levels disrupt the electrolyte balance and membrane permeability of the lens fibers, resulting in the formation of characteristic **punctate, polychromatic "snowflake" opacities** in the subcapsular cortex. 2. **Cigarette Smoking:** Smoking is a major modifiable risk factor. It promotes cataract formation (specifically **nuclear cataracts**) through the accumulation of heavy metals (like cadmium) and by inducing **oxidative stress**, which depletes the lens of protective antioxidants like Vitamin C and glutathione. 3. **Non-ionizing Radiation:** This includes **Infrared (IR) radiation** and **Ultraviolet (UV) light**. IR radiation is classically associated with "Glass-blower’s cataract" (true exfoliation of the lens capsule), while chronic UV-B exposure is a significant risk factor for cortical cataracts. **High-Yield Clinical Pearls for NEET-PG:** * **Hypercalcemia** does NOT cause cataracts; it is **Hypocalcemia** (as seen in hypoparathyroidism) that is the culprit. * **Ionizing radiation** (X-rays/Gamma rays) typically causes **Posterior Subcapsular Cataracts (PSC)**, which are the most visually debilitating. * **Wilson’s Disease** causes a "Sunflower cataract," while **Galactosemia** causes a "Oil droplet cataract." * **Diabetes Mellitus** is associated with "Snowflake cataracts" (due to sorbitol accumulation via the polyol pathway).

Question 216: Posterior lenticonus is a characteristic feature of which of the following conditions?

A. Alport syndrome
B. Lowe syndrome (Correct Answer)
C. Marfan syndrome
D. Homocystinuria

Explanation: **Explanation:** **Lowe Syndrome (Oculocerebrorenal Syndrome)** is an X-linked recessive disorder characterized by the triad of congenital cataracts, mental retardation, and renal tubular dysfunction (Fanconi syndrome). **Posterior lenticonus**—a cone-shaped protrusion of the posterior lens surface into the vitreous—is a classic ocular hallmark of this condition. It occurs due to a localized thinning or absence of the posterior lens capsule, often leading to early-onset cataract formation. **Analysis of Incorrect Options:** * **Alport Syndrome:** This is characteristically associated with **Anterior lenticonus**. It is a genetic disorder of Type IV collagen affecting the basement membranes of the kidney (nephritis), ear (sensorineural deafness), and eye. * **Marfan Syndrome:** The classic lens finding here is **Ectopia lentis** (subluxation), typically occurring in the **superotemporal** direction. The zonules are stretched but intact. * **Homocystinuria:** This also presents with **Ectopia lentis**, but the displacement is characteristically **inferonasal**. Unlike Marfan, the zonules are brittle and broken due to a deficiency in the enzyme cystathionine beta-synthase. **High-Yield Clinical Pearls for NEET-PG:** * **Lenticonus vs. Lentiglobus:** Lenticonus is cone-shaped; Lentiglobus is a hemispherical (spherical) protrusion. * **Oil Droplet Sign:** On distant direct ophthalmoscopy, lenticonus appears as a dark "oil droplet" in the red reflex. * **Alport Syndrome Mnemonic:** "A" for **A**nterior lenticonus and **A**lport. * **Lowe Syndrome Mnemonic:** **P**osterior lenticonus is seen in Lowe (think of the "o" in Lowe as the posterior curve).

Question 217: Which of the following conditions is associated with abnormalities of the optic lens?

A. Hypoparathyroidism
B. Homocystinuria
C. Congenital rubella
D. All of the above (Correct Answer)

Explanation: The correct answer is **D. All of the above**. The lens is highly sensitive to metabolic, genetic, and infectious insults, which manifest as cataracts or ectopia lentis. ### **Detailed Explanation:** 1. **Hypoparathyroidism:** Low levels of parathyroid hormone lead to **hypocalcemia**. This electrolyte imbalance disrupts the active transport of water and electrolytes in the lens, resulting in the formation of punctate, polychromatic, or **"snowflake" cataracts** (subcapsular opacities). 2. **Homocystinuria:** This is an autosomal recessive metabolic disorder. It is a classic cause of **Ectopia Lentis** (dislocation of the lens). Characteristically, the lens displaces **downward and inward** (inferonasal) due to a deficiency in cystathionine beta-synthase, which leads to brittle zonules. 3. **Congenital Rubella Syndrome (CRS):** Rubella is a potent teratogen. If the infection occurs during the first trimester, the virus can cross the lens capsule before it is fully formed. This leads to a **pearly white nuclear cataract**, often associated with "salt and pepper" retinopathy and microphthalmos. ### **High-Yield Clinical Pearls for NEET-PG:** * **Ectopia Lentis Comparison:** * *Marfan Syndrome:* Upward and outward (Superotemporal) dislocation. * *Homocystinuria:* Downward and inward (Inferonasal) dislocation. * **Galactosemia:** Associated with **"Oil droplet" cataracts**. * **Diabetes Mellitus:** Associated with **"Snowflake" cataracts** (true diabetic cataract) and early onset of senile cataracts. * **Wilson’s Disease:** Associated with **"Sunflower" cataracts** (though the classic sign is the Kayser-Fleischer ring in the cornea).

Question 218: What is the major function of major intrinsic protein-26 (MIP-26)?

A. Glucose transport in the lens
B. Transport of water in the lens (Correct Answer)
C. Diffusion barrier
D. Capsule of the lens

Explanation: **Explanation:** **Major Intrinsic Protein-26 (MIP-26)**, also known as **Aquaporin-0 (AQP0)**, is the most abundant membrane protein in the crystalline lens, accounting for over 60% of its total membrane protein content. 1. **Why Option B is Correct:** MIP-26 functions primarily as a water channel. It is essential for the **lens microcirculation system**, allowing for the rapid transport of water and small solutes between lens fibers. This maintains lens dehydration and transparency. Mutations in the gene encoding MIP-26 are clinically linked to the development of congenital cataracts. 2. **Why Other Options are Incorrect:** * **Option A:** Glucose transport in the lens is primarily mediated by **GLUT-1** receptors, not MIP-26. * **Option C:** A diffusion barrier usually refers to the physiological barrier created by aging or oxidative stress in the lens nucleus (the "barrier" to antioxidants like glutathione), rather than a specific protein function. * **Option D:** The lens capsule is a modified basement membrane composed mainly of **Type IV collagen** and glycosaminoglycans, not MIP-26. **High-Yield NEET-PG Pearls:** * **MIP-26/AQP0** is specific to the lens fiber cells. * **Lens Crystallins:** These are the soluble proteins of the lens (Alpha, Beta, Gamma). **Alpha-crystallin** acts as a molecular chaperone, preventing the aggregation of denatured proteins (preventing cataract). * **Lens Metabolism:** The lens derives most of its energy (90%) from **anaerobic glycolysis**. The sorbitol pathway (aldose reductase) becomes significant in diabetic cataracts. * **Highest Protein Content:** The lens has the highest protein concentration of any organ in the body (approx. 33%).

Question 219: Cataract is seen in all of the following conditions EXCEPT:

A. Wilson's disease
B. Diabetes mellitus
C. Hereditary fructose intolerance (Correct Answer)
D. Galactosemias

Explanation: **Explanation:** The correct answer is **Hereditary Fructose Intolerance (HFI)**. Cataract formation is primarily associated with disorders of glucose and galactose metabolism, rather than fructose metabolism. **1. Why Hereditary Fructose Intolerance (HFI) is the correct answer:** HFI is caused by a deficiency of **Aldolase B**. While it leads to severe systemic issues like hypoglycemia and liver failure upon fructose ingestion, it **does not** cause cataracts. This is because the lens lacks the enzyme required to convert fructose into osmotically active sugar alcohols (like sorbitol or dulcitol) in significant quantities to cause opacification. **2. Why the other options are incorrect:** * **Galactosemias:** Both Classic Galactosemia (Galactose-1-phosphate uridyltransferase deficiency) and Galactokinase deficiency cause **"Oil droplet" cataracts**. Excess galactose is converted to **dulcitol (galactitol)** by the enzyme aldose reductase, leading to osmotic swelling of lens fibers. * **Diabetes Mellitus:** Hyperglycemia leads to the conversion of glucose to **sorbitol** via the polyol pathway. Sorbitol accumulation causes osmotic stress. Classic diabetic cataract is the **"Snowflake" cataract**. * **Wilson’s Disease:** This disorder of copper metabolism is classically associated with the **"Sunflower" cataract** (copper deposition in the anterior capsule) and the Kayser-Fleischer (KF) ring in the cornea. **High-Yield Clinical Pearls for NEET-PG:** * **Galactosemia:** Most common metabolic cause of cataracts in newborns. * **Hypocalcemia:** Associated with **punctate/zonular cataracts**. * **Myotonic Dystrophy:** Associated with **"Christmas tree" cataracts**. * **Fabry’s Disease:** Associated with **"Spoke-like" (propeller) cataracts**. * **Rule of Thumb:** If a metabolic disease ends in "-ose" (Glucose, Galactose), think cataracts; if it involves Fructose, cataracts are generally absent.

Question 220: The 'Ring of Sommerring' is typically seen in which of the following conditions?

A. Galactosemia
B. Dislocation of the lens
C. Acute congestive glaucoma
D. After cataract (Correct Answer)

Explanation: **Explanation:** The **Ring of Sommerring** is a classic morphological type of **After-cataract** (Posterior Capsular Opacification). It occurs following Extracapsular Cataract Extraction (ECCE) or trauma. **1. Why "After cataract" is correct:** When the central part of the anterior capsule and the lens substance are removed, but the peripheral cortical fibers remain trapped between the anterior and posterior capsular flaps, these cells undergo proliferation. This creates a **doughnut-shaped ring** of lens matter behind the iris. While the central visual axis may remain clear initially, the ring can cause visual disturbances if it displaces or if the cells migrate centrally (forming Elschnig’s pearls). **2. Why other options are incorrect:** * **Galactosemia:** Characterized by a **"Oil droplet" cataract** due to the accumulation of dulcitol. * **Dislocation of the lens (Ectopia Lentis):** Refers to the displacement of the lens from its normal position (e.g., Marfan syndrome). It does not involve the formation of a peripheral cortical ring. * **Acute congestive glaucoma:** Associated with **Glaukomflecken** (small, grey-white subcapsular opacities) due to high intraocular pressure causing focal lens necrosis. **3. High-Yield Clinical Pearls for NEET-PG:** * **Elschnig’s Pearls:** Another form of after-cataract where subcapsular epithelial cells migrate to the posterior capsule and vacuolate, resembling "clusters of pearls" or "fish eggs." * **Treatment:** The gold standard for symptomatic after-cataract is **YAG Laser Capsulotomy**. * **Prevention:** Modern surgical techniques like "Square-edge" Intraocular Lenses (IOLs) help prevent cell migration and reduce the incidence of after-cataract.

Practice by Chapter

Lens Anatomy and Physiology

Practice Questions

Age-Related Cataract

Practice Questions

Congenital and Developmental Cataracts

Practice Questions

Traumatic Cataract

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Metabolic Cataracts

Practice Questions

Drug-Induced Cataracts

Practice Questions

Cataract Surgery Techniques

Practice Questions

Intraocular Lens Implants

Practice Questions

Complications of Cataract Surgery

Practice Questions

Posterior Capsular Opacification

Practice Questions

Lens Subluxation and Dislocation

Practice Questions

Specialty IOLs

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