Diseases of the Lens Practice Questions

Q: A patient presents to the emergency department with uniocular diplopia. Examination with oblique illumination shows a golden crescent while examination with co-axial illumination shows a dark crescent line. Which of the following is the most likely diagnosis?

Ectopia lentis. ### **Explanation** **1. Why Ectopia Lentis is the Correct Answer:** The clinical signs described—a **golden crescent** on oblique illumination and a **dark crescent line** on co-axial illumination (retroillumination)—are pathognomonic for the **edge of a subluxated lens**. * **Uniocular Diplopia:** When the lens is displaced, light enters the eye through two distinct zones: the phakic area (through the lens) and the aphakic area (beside the lens). This creates two images on the retina. * **Optical Phenomena:** In oblique illumination, light reflects off the equator of the lens, appearing as a golden crescent. In co-axial illumination, the lens edge scatters light away from the observer, appearing as a dark, well-defined border against the red reflex. **2. Why Other Options are Incorrect:** * **Lenticonus:** This is a conical protrusion of the lens capsule. On retroillumination, it presents with an **"Oil droplet" appearance**, not a crescentic edge. * **Coloboma:** While it involves a defect in the lens periphery, it is a localized notch or indentation due to deficient ciliary body development, not a displacement of the entire lens edge across the pupillary axis. * **Microspherophakia:** The lens is small and spherical. While it can lead to subluxation, the primary sign is a visible 360-degree lens margin within the dilated pupil and high lenticular myopia, rather than the specific crescentic signs of displacement. **3. High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of Ectopia Lentis:** Trauma. * **Systemic Associations:** * **Marfan Syndrome:** Upward and outward (Superotemporal) displacement. * **Homocystinuria:** Downward and inward (Inferonasal) displacement; associated with secondary glaucoma. * **Iridodonesis:** Tremulousness of the iris is a common associated finding in lens subluxation due to lack of posterior support.

Q: Which of the following statements is false regarding Mercurius lentis?

It is bilateral and affects visual acuity.. **Explanation:** **Mercurius Lentis** (also known as Mercuria Lentis) is a rare ocular condition caused by chronic exposure to mercury, typically through industrial vapors or prolonged use of mercury-containing eye drops (e.g., phenylmercuric nitrate). **Why Option D is the correct (False) statement:** While Mercurius lentis is indeed **bilateral** and symmetrical, it is characterized by the fact that it **does not affect visual acuity**. The mercury deposits are superficial and do not lead to true lens opacification (cataract) or significant light scattering that would impair vision. Therefore, the claim that it affects visual acuity is incorrect. **Analysis of other options:** * **Option A:** It presents as a characteristic **brownish or rose-colored** luster/deposit on the **anterior lens capsule**. * **Option B:** On slit-lamp examination, the deposit often exhibits a **"Maltese cross"** or "flower-petal" appearance due to the pattern of mercury deposition. * **Option C:** The most common cause is chronic occupational exposure to **mercurial vapors** in industries like thermometer or mirror manufacturing. **High-Yield Clinical Pearls for NEET-PG:** * **Nature of the lesion:** It is a "deposition," not a true cataract. * **Color:** Often described as "rose-brown" or "pinkish-grey." * **Reversibility:** The discoloration is usually permanent even after the source of mercury is removed. * **Differential Diagnosis:** Do not confuse this with **Chalcosis** (sunflower cataract due to copper) or **Siderosis** (iron deposition), both of which can significantly impact vision.

Q: The crystalline lens absorbs light rays shorter than which of the following wavelengths?

350 nm. **Explanation:** The crystalline lens acts as a natural filter for the eye, protecting the retina from high-energy radiation. It primarily absorbs ultraviolet (UV) radiation, specifically **UVA (315–400 nm)** and some **UVB (280–315 nm)**. While the cornea absorbs most wavelengths shorter than 295 nm, the lens is the primary filter for wavelengths between **300 nm and 400 nm**, with its peak absorption threshold effectively preventing rays shorter than **350–390 nm** from reaching the retina. In the context of standard ophthalmic teaching for NEET-PG, **350 nm** is recognized as the critical cutoff below which the lens absorbs almost all incident light. **Analysis of Options:** * **A. 295 nm:** This is the cutoff for the **cornea**. The cornea absorbs most UVC and shorter UVB rays; radiation shorter than 295 nm does not even reach the lens. * **C. 390 nm:** While the lens does absorb light up to 400 nm (the edge of the visible spectrum), 350 nm is the more precise physiological threshold for total absorption of the shorter, more damaging UV rays. * **D. 490 nm:** This falls within the **visible blue-green light spectrum**. If the lens absorbed light at 490 nm, human vision would be significantly impaired. **Clinical Pearls for NEET-PG:** * **Aphakic Protection:** In aphakia (absence of lens), the retina is vulnerable to UV damage (solar retinopathy). Therefore, aphakic glasses or IOLs must have **UV filters**. * **Cataractogenesis:** Chronic absorption of UV light leads to the generation of free radicals, resulting in the opacification of the lens (senile cataract). * **Nuclear Sclerosis:** As the lens ages, it turns yellow/brown (brunescent cataract), which actually increases its ability to filter blue light, potentially protecting the macula.

Q: Cataract is caused by the deficiency of all of the following EXCEPT?

Vitamin A. **Explanation:** The development of cataract is primarily linked to oxidative stress and metabolic imbalances within the lens. **Why Vitamin A is the correct answer:** Vitamin A deficiency is classically associated with **Xerophthalmia**, which involves the conjunctiva, cornea, and retina (causing Night Blindness). It does **not** cause cataracts. In fact, Vitamin A (Retinol) is essential for the health of the ocular surface and the synthesis of rhodopsin in the retina, but its absence does not trigger lens opacification. **Analysis of Incorrect Options:** * **Vitamin D & Calcium:** These are closely linked. **Hypocalcemia** (often due to Vitamin D deficiency or hypoparathyroidism) leads to the formation of **Zonular (Lamellar) cataracts** or punctate subcapsular opacities. Calcium is vital for maintaining the permeability of the lens capsule; low levels disrupt electrolyte balance, leading to hydration changes and opacification. * **Vitamin E:** This is a potent **antioxidant**. The lens is susceptible to oxidative damage from free radicals. A deficiency in antioxidants like Vitamin E (and Vitamin C) reduces the lens's defense mechanisms, accelerating the aging process and leading to **Senile Cataract**. **High-Yield Clinical Pearls for NEET-PG:** * **Hypocalcemic Cataract:** Characterized by many small, white, iridescent "breadcrumbs" or "polychromatic lustres" in the cortical layers. * **Galactosemia:** Causes "Oil droplet" cataract (Deficiency of GALT enzyme). * **Wilson’s Disease:** Causes "Sunflower" cataract (Copper deposition). * **Myotonic Dystrophy:** Causes "Christmas tree" cataract. * **Diabetes Mellitus:** Causes "Snowflake" cataract.

Q: Zonular cataract is seen in which of the following conditions?

Hypoparathyroidism. **Explanation:** **Zonular (Lamellar) Cataract** is the most common type of congenital/infantile cataract. It is characterized by opacity involving a specific "zone" or layer of the lens fibers (usually the fetal nucleus), while the core and the outer cortex remain clear. **1. Why Hypoparathyroidism is Correct:** Hypocalcemia is a well-known metabolic cause of zonular cataract. In **hypoparathyroidism**, low serum calcium levels disrupt the electrolyte balance within the lens. Calcium is essential for maintaining the integrity of lens fiber membranes and the activity of the sodium-potassium pump. A deficiency leads to increased membrane permeability and hydration of specific lens fibers, resulting in the characteristic lamellar opacities. **2. Analysis of Incorrect Options:** * **Diabetes Mellitus:** Typically associated with "Snowflake cataracts" (true diabetic cataract) or early-onset senile cataracts (nuclear/cortical). * **Gaucher’s Disease:** A lysosomal storage disorder that primarily affects the viscera and bones; it is not a classic cause of zonular cataracts. * **Niemann-Pick Disease:** Known for the "Cherry-red spot" at the macula due to sphingomyelin accumulation in ganglion cells, but not typically associated with zonular cataracts. **3. NEET-PG High-Yield Pearls:** * **Morphology:** Zonular cataracts often show **"Riders"** (linear opacities extending from the equator of the opacity into the clear cortex). * **Etiology:** Besides hypocalcemia, other causes include maternal malnutrition (Vitamin D deficiency) and rubella infection. * **Galactosemia:** Associated with **"Oil droplet"** cataracts. * **Wilson’s Disease:** Associated with **"Sunflower"** cataracts. * **Myotonic Dystrophy:** Associated with **"Christmas tree"** cataracts.

Q: Which of the following best describes zonular cataract?

Developmental cataract. **Explanation:** **Zonular (Lamellar) Cataract** is the most common type of **developmental (congenital) cataract** presenting with visual impairment. It occurs due to a transient interference with lens fiber formation during fetal development or early infancy. 1. **Why Option B is Correct:** Zonular cataract is classified as a developmental cataract because it affects a specific "zone" or layer of the lens (usually the fetal or infantile nucleus) while the layers formed before and after the insult remain clear. It is typically bilateral and symmetrical, often associated with maternal malnutrition, Vitamin D deficiency, or hypocalcemia during pregnancy. 2. **Why Other Options are Incorrect:** * **Option A (Riders not seen):** This is incorrect. **"Riders"** (linear opacities extending from the equator of the opacity into the clear cortex) are a **pathognomonic hallmark** of zonular cataracts. * **Option C (Acquired cataract):** Acquired cataracts (like senile, traumatic, or metabolic cataracts) involve the degeneration of previously clear lens fibers later in life, rather than a developmental arrest in a specific zone. * **Option D (After complication):** This refers to "Complicated Cataract," which occurs secondary to intraocular diseases like chronic uveitis or high myopia, typically presenting as a posterior subcapsular "polychromatic luster." **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Appears as a central opacity surrounded by a clear cortex, with characteristic **"Riders."** * **Etiology:** Most common cause is **genetic (autosomal dominant)**; however, environmental triggers like **hypocalcemia** are frequently tested. * **Visual Impact:** It usually causes significant visual deprivation, often requiring surgical intervention (lens aspiration with IOL implantation).

Q: Mittendorf dot is found on which structure?

Posterior capsule of lens. **Explanation:** **Mittendorf dot** is a small, circular, white opacity located on the **posterior capsule of the lens**, typically slightly nasal to the visual axis. It represents a benign, congenital remnant of the **hyaloid artery**, specifically where the artery was previously attached to the lens during fetal development. * **Why Option B is correct:** During embryogenesis, the hyaloid artery supplies the developing lens. Normally, this vessel regresses completely by the seventh month of gestation. If the anterior-most attachment of the hyaloid artery fails to involute fully, it leaves a small fibrotic scar on the posterior lens capsule known as a Mittendorf dot. It does not affect vision. * **Why Options A, C, and D are incorrect:** * **Anterior capsule:** Opacities here are usually related to persistent pupillary membranes or Epicapsular stars (remnants of the tunica vasculosa lentis). * **Vitreous:** A remnant of the hyaloid artery projecting into the vitreous from the optic disc is known as a **Bergmeister’s papilla**, not a Mittendorf dot. * **Retina:** While the hyaloid artery originates from the optic disc (retinal surface), the specific term "Mittendorf dot" is reserved for the lenticular attachment site. **High-Yield Clinical Pearls for NEET-PG:** * **Cloquet’s Canal:** The vestigial channel in the vitreous that previously housed the hyaloid artery. * **Bergmeister’s Papilla:** The posterior counterpart of the Mittendorf dot (remnant at the optic disc). * **Persistent Fetal Vasculature (PFV):** A more severe condition where the hyaloid system fails to regress, often leading to congenital cataracts or leukocoria.

Q: What is the approximate water content of the human lens?

64%. **Explanation:** The human crystalline lens is a unique, transparent, avascular structure. Its composition is approximately **64% water** and **35% protein** (primarily crystallins), with the remaining 1% consisting of lipids and electrolytes. The high water content is essential for maintaining the lens's transparency and refractive index. This hydration is tightly regulated by the **lens epithelium**, specifically through the **Na+/K+-ATPase pump** (the "pump-leak" mechanism). Any significant disruption in this water-protein balance leads to protein aggregation and opacification, clinically known as a **cataract**. **Analysis of Options:** * **Option A (1%):** This represents the approximate concentration of lipids and trace electrolytes in the lens, not the water content. * **Option B (28%):** This is too low for the lens. For comparison, the water content of the cornea is much higher (approx. 78%). * **Option C (35%):** This is the approximate **protein content** of the lens. The lens has the highest protein concentration of any tissue in the human body. * **Option D (64%):** This is the correct physiological water content of a healthy human lens. **NEET-PG High-Yield Pearls:** * **Refractive Power:** The lens contributes approximately **15-18 Diopters** to the total refractive power of the eye. * **Metabolism:** The lens derives its nutrition from the **aqueous humor** and relies primarily on **anaerobic glycolysis** (90%) for energy. * **Aging Change:** As the lens ages (nuclear sclerosis), the water content slightly decreases while the insoluble protein content increases. * **Sutures:** The lens fibers meet to form the characteristic **Y-sutures** (erect 'Y' anteriorly, inverted 'Y' posteriorly).

Q: What is the primary function of the zonules of Zinn?

To suspend the lens.. **Explanation:** The **Zonules of Zinn** (also known as the suspensory ligaments of the lens) are a series of delicate, transparent fibers that originate from the ciliary body and insert into the lens capsule. **Why Option B is Correct:** The primary physiological function of the zonules is to **suspend the lens** in the visual axis and connect it to the ciliary muscle. This connection is fundamental to the mechanism of **accommodation**. When the ciliary muscle contracts, zonular tension decreases, allowing the elastic lens to become more spherical (increasing refractive power for near vision). **Analysis of Incorrect Options:** * **Option A:** Stability of the eyeball is primarily maintained by the sclera (structural integrity) and intraocular pressure (IOP). * **Option C:** Zonules do not attach to the posterior pole. They insert circumferentially into the **lens capsule at the equator**, extending slightly onto the anterior and posterior surfaces. * **Option D:** Extraocular muscles attach to the sclera on the external surface of the globe to control eye movements; they have no direct anatomical connection to the zonules. **High-Yield Clinical Pearls for NEET-PG:** * **Ectopia Lentis:** Subluxation or dislocation of the lens occurs due to the weakening or breakage of zonules. * **Marfan Syndrome:** Typically causes **superior-temporal** lens subluxation (zonules are stretched/weak). * **Homocystinuria:** Typically causes **inferior-nasal** lens subluxation (zonules are often absent or brittle). * **Pseudoexfoliation Syndrome:** Characterized by deposition of fibrillar material on the zonules, leading to zonular instability, which is a major risk factor for complications during cataract surgery (phacoemulsification).

Q: Which type of senile cataract is notorious for glaucoma formation?

Intumescent cataract. **Explanation:** The correct answer is **Intumescent cataract**. **Mechanism of Glaucoma Formation:** An intumescent cataract occurs during the immature stage of senile cataract development. As the lens fibers degenerate, they create an osmotic gradient that draws aqueous humor into the lens. This causes the lens to become **swollen (hydrated)** and enlarged. The increased anteroposterior diameter of the lens pushes the iris forward, narrowing the iridocorneal angle and leading to **Secondary Angle-Closure Glaucoma** (specifically, Phacomorphic Glaucoma). **Analysis of Incorrect Options:** * **Incipient cataract:** This is the earliest stage where small opacities appear. The lens volume remains normal; therefore, it does not pose a risk for glaucoma. * **Hypermature Morgagnian cataract:** While this can cause **Phacolytic Glaucoma** (due to leakage of liquefied lens proteins blocking the trabecular meshwork), it is less "notorious" for the acute, mechanical angle closure seen in the intumescent stage. * **Nuclear cataract:** This involves central sclerosis and yellowing of the lens. It typically causes a "myopic shift" (second sight) but does not involve significant lens swelling or angle compromise. **Clinical Pearls for NEET-PG:** * **Phacomorphic Glaucoma:** Caused by an **Intumescent** lens (mechanical angle closure). * **Phacolytic Glaucoma:** Caused by a **Hypermature** lens (macrophages clogging the meshwork). * **Phacoantigenic Glaucoma:** A type of endophthalmitis/uveitis following lens capsule rupture. * **Iris Shadow:** This is a classic clinical sign of an immature/intumescent cataract, which disappears once the cataract becomes mature.

Question 1

A patient presents to the emergency department with uniocular diplopia. Examination with oblique illumination shows a golden crescent while examination with co-axial illumination shows a dark crescent line. Which of the following is the most likely diagnosis?

Accepted Answer

Ectopia lentis

Answer

Lenticonus

Answer

Coloboma

Answer

Microspherophakia

Question 2

Which of the following statements is false regarding Mercurius lentis?

Accepted Answer

It is bilateral and affects visual acuity.

Answer

A brownish deposit of mercury on the anterior lens capsule.

Answer

Slit lamp examination shows a maltese cross reflex.

Answer

Caused by exposure to mercurial vapors.

Question 3

The crystalline lens absorbs light rays shorter than which of the following wavelengths?

Accepted Answer

350 nm

Answer

295 nm

Answer

390 nm

Answer

490 nm

Question 4

Cataract is caused by the deficiency of all of the following EXCEPT?

Accepted Answer

Vitamin A

Answer

Vitamin D

Answer

Calcium

Answer

Vitamin E

Question 5

Zonular cataract is seen in which of the following conditions?

Accepted Answer

Hypoparathyroidism

Answer

Diabetes mellitus

Answer

Gaucher's disease

Answer

Niemann-Pick disease

Question 6

Which of the following best describes zonular cataract?

Accepted Answer

Developmental cataract

Answer

Riders not seen

Answer

Acquired cataract

Answer

After complication

Question 7

Mittendorf dot is found on which structure?

Accepted Answer

Posterior capsule of lens

Answer

Anterior capsule of lens

Answer

Vitreous

Answer

Retina

Question 8

What is the approximate water content of the human lens?

Accepted Answer

64%

Answer

1%

Answer

28%

Answer

35%

Question 9

What is the primary function of the zonules of Zinn?

Accepted Answer

To suspend the lens.

Answer

To provide stability to the eyeball.

Answer

To attach at the posterior pole of the lens.

Answer

To attach to the extraocular muscles.

Question 10

Which type of senile cataract is notorious for glaucoma formation?

Accepted Answer

Intumescent cataract

Answer

Incipient cataract

Answer

Hypermature morgagnian cataract

Answer

Nuclear cataract

Diseases of the Lens — MCQs

Diseases of the Lens — MCQs

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