Diseases of the Lens Practice Questions

Q: Which type of congenital cataract presents with a disc of opacity involving the fetal and embryonal nucleus with many white dots resembling dust?

Pulverulent cataract. **Explanation:** **Pulverulent cataract** (specifically the **Coppock cataract** or Doyne’s discoid cataract) is a hereditary, bilateral condition characterized by a disc-shaped opacity involving the embryonal and fetal nuclei. The term "pulverulent" refers to its "powdery" or "dust-like" appearance, consisting of numerous small white dots. It is typically non-progressive and rarely affects vision significantly. **Analysis of Incorrect Options:** * **A. Lamellar (Zonular) Cataract:** This is the most common type of congenital cataract. It involves a specific "shell" or layer of the lens (usually the fetal nucleus) while the core remains clear. It is characterized by **"riders"** (linear opacities extending towards the equator), which are absent in pulverulent cataracts. * **B. Punctate Cataract (Blue Dot Cataract):** Also known as *Cataracta punctata caerulea*, these appear as multiple small, bluish, translucent dots scattered throughout the lens. They do not form a central discoid mass in the fetal nucleus. * **C. Coronary Cataract:** This is a form of developmental cataract that occurs at puberty. The opacities are club-shaped or petal-shaped and are arranged in a ring (corona) in the peripheral cortex, leaving the center of the lens clear. **High-Yield Clinical Pearls for NEET-PG:** * **Most common congenital cataract:** Lamellar (Zonular) cataract. * **Most common cause of unilateral congenital cataract:** Persistent Fetal Vasculature (PFV) / Persistent Hyperplastic Primary Vitreous (PHPV). * **Maternal Rubella:** Typically causes a "pearly white" nuclear cataract. * **Galactosemia:** Characterized by a **"Oil droplet"** appearance. * **Diabetes Mellitus:** Characterized by **"Snowflake"** opacities.

Q: What is the mode of inheritance for congenital cataract?

Autosomal dominant. **Explanation:** **1. Why Autosomal Dominant is Correct:** Congenital cataract is a leading cause of preventable childhood blindness. While it can be associated with metabolic disorders (like Galactosemia) or intrauterine infections (TORCH), the majority of **isolated (idiopathic) hereditary cases** follow an **Autosomal Dominant (AD)** pattern of inheritance. This is primarily due to mutations in genes encoding **crystallins** (the structural proteins of the lens) or **connexins** (gap junction proteins), which are essential for maintaining lens transparency. **2. Why Other Options are Incorrect:** * **Autosomal Recessive (AR):** While AR inheritance can occur, it is much less common and typically associated with consanguinity or specific metabolic syndromes. * **X-linked Recessive/Dominant:** These are rare modes of inheritance for cataracts. X-linked recessive cataracts are usually seen as part of a systemic syndrome, such as **Lowe Syndrome** (Oculo-cerebro-renal syndrome). **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Most common type:** The most common morphological type of congenital cataract is **Zonular (Lamellar) cataract**. * **Visual Prognosis:** The most "amblyogenic" (vision-threatening) type is the **Total/Dense Central cataract**. * **Unilateral vs. Bilateral:** Bilateral cataracts are often genetic or metabolic, whereas unilateral cataracts are usually sporadic or traumatic. * **Surgery Timing:** To prevent stimulus-deprivation amblyopia, surgery is ideally performed within **4–6 weeks** of birth. * **Association:** Remember the "Oil droplet" appearance in **Galactosemia** and "Sunflower cataract" in **Wilson’s disease**.

Q: The SRK formula is used to calculate:

Power of intraocular lens. The **SRK (Sanders-Retzlaff-Kraff) formula** is a regression formula used to calculate the power of an **Intraocular Lens (IOL)** required for implantation during cataract surgery to achieve a desired postoperative refractive state. ### Why Option A is Correct The SRK formula is based on the relationship between axial length, corneal power, and IOL power. The standard formula is: **P = A – 2.5L – 0.9K** * **P:** Power of IOL (in Diopters) * **A:** A-constant (specific to the lens design/manufacturer) * **L:** Axial length of the eye (measured via Biometry/A-scan) * **K:** Average Keratometry reading (corneal power) ### Why Other Options are Incorrect * **B. Corneal curvature:** This is measured using **Keratometry** or **Corneal Topography**. While K-readings are a *component* of the SRK formula, the formula itself calculates lens power, not curvature. * **C. Corneal endothelial cell count:** This is assessed using **Specular Microscopy**. It is vital for evaluating corneal health before surgery but is unrelated to IOL power calculation. * **D. Extent of retinal detachment:** This is evaluated clinically via **Indirect Ophthalmoscopy** or **B-scan Ultrasonography**. ### High-Yield Clinical Pearls for NEET-PG * **Evolution of Formulas:** * **SRK-I & II:** Older regression formulas. * **SRK-T (Theoretical):** A 3rd generation formula preferred for **long (myopic) eyes**. * **Hoffer Q:** Preferred for **short (hypermetropic) eyes**. * **Barrett Universal II:** Currently considered one of the most accurate formulas for all eye lengths. * **Biometry:** The most common cause of error in IOL power calculation is an inaccurate measurement of the **Axial Length**.

Q: What is the most common type of senile cataract?

Cuneiform. **Explanation:** Senile cataract is the most common cause of visual impairment in the elderly, occurring due to age-related degenerative changes in the lens. It is broadly classified into two types: **Cortical (Soft)** and **Nuclear (Hard)**. **Why Cuneiform is the correct answer:** The **Cuneiform cataract** is a subtype of senile cortical cataract. It is statistically the **most common morphological type** of senile cataract. It is characterized by wedge-shaped opacities (spokes) that begin in the periphery of the lens cortex and progress toward the center. These opacities are caused by the hydration of lens fibers, leading to the formation of water clefts and vacuoles. **Analysis of Incorrect Options:** * **Nuclear Cataract:** While very common, it is the second most frequent type. It involves intensification of the age-related hardening (sclerosis) and yellowing of the lens nucleus. It is classically associated with "second sight" (myopic shift). * **Cupuliform (Posterior Subcapsular) Cataract:** This is the least common type of senile cataract but the most visually significant. It forms a saucer-shaped opacity at the posterior pole. It causes significant glare and affects near vision more than distance vision. **High-Yield Clinical Pearls for NEET-PG:** * **Most common type overall:** Cuneiform (Cortical). * **Cataract with "Second Sight":** Nuclear cataract (due to index myopia). * **Cataract associated with Steroids/Diabetes:** Posterior Subcapsular (Cupuliform). * **Earliest sign of Senile Cortical Cataract:** Vacuoles and water clefts. * **Morgagnian Cataract:** A hypermature stage where the cortex liquefies and the nucleus settles at the bottom.

Q: Dislocation of the lens is seen in all the following conditions except?

Congenital Rubella. **Explanation** The correct answer is **Congenital Rubella**. **1. Why Congenital Rubella is the correct answer:** In Congenital Rubella Syndrome (CRS), the primary lens pathology is a **congenital cataract** (typically pearly white and nuclear). The virus directly invades the lens vesicle during the first trimester. While it causes microphthalmos and cataracts, it does **not** typically cause ectopia lentis (dislocation). The zonules remain intact. **2. Analysis of Incorrect Options (Conditions where dislocation occurs):** * **Marfan Syndrome:** The most common cause of heritable lens dislocation. It typically presents as **superotemporal** (upward and outward) subluxation. The zonules are stretched but often remain intact. * **Homocystinuria:** An autosomal recessive metabolic disorder. It typically presents as **inferonasal** (downward and inward) dislocation. Unlike Marfan’s, the zonules are brittle and completely broken due to a deficiency in cystathionine beta-synthase. * **Marchesani’s Syndrome (Weill-Marchesani):** Characterized by **microspherophakia** (small, spherical lens). The lens is prone to downward dislocation and can cause pupillary block glaucoma. **3. High-Yield Clinical Pearls for NEET-PG:** * **Direction of Dislocation:** * **Marfan:** Upward (Think: Marfan patients are tall/up). * **Homocystinuria:** Downward (Think: "H" for Homocystinuria, "H" for humble/down). * **Ectopia Lentis et Pupillae:** A rare condition where the lens and the pupil are displaced in opposite directions. * **Trauma:** The most common overall cause of lens dislocation (acquired). * **Sulfite Oxidase Deficiency:** A rare cause of dislocation associated with severe neurological impairment.

Q: Which of the following is a cause of anterior polar cataract?

Perforating corneal injury. **Explanation:** **Anterior polar cataract** involves a small, well-defined opacity at the central part of the anterior lens capsule and the underlying subcapsular cortex. **Why Option B is correct:** The primary mechanism for acquired anterior polar cataract is a **perforating corneal injury**. When the cornea is perforated, the aqueous humor escapes, causing the anterior chamber to collapse. This leads to direct contact between the lens and the inflamed corneal endothelium. This contact, often associated with a corneal ulcer or trauma, triggers the proliferation of subcapsular epithelium and subsequent fibrous metaplasia, resulting in a localized opacity. **Why the other options are incorrect:** * **A. Diabetes Mellitus:** Typically causes "Snowflake" cataracts (subcapsular opacities) or accelerates the formation of senile nuclear sclerosis. * **C. Irradiation:** Radiation exposure (e.g., X-rays, Gamma rays) characteristically leads to **Posterior Subcapsular Cataract (PSC)**, as the damaged epithelial cells migrate to the posterior pole. * **D. Chalcosis:** Intraocular copper (Chalcosis bulbi) results in a **"Sunflower cataract"** due to copper deposition in the lens capsule. **High-Yield Clinical Pearls for NEET-PG:** * **Congenital Etiology:** Most anterior polar cataracts are congenital and sporadic, often associated with persistent pupillary membranes. * **Pyramidal Cataract:** If the opacity projects forward into the anterior chamber like a cone, it is termed a pyramidal cataract. * **Visual Impact:** These cataracts are usually stationary and rarely affect vision significantly because they are very small and central. * **Differential:** Do not confuse with **Posterior Polar Cataract**, which is associated with a weakened posterior capsule and carries a high risk of **Posterior Capsular Rupture (PCR)** during surgery.

Q: Which of the following can cause cataracts?

All of the above. **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).

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

Lowe syndrome. **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).

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

All of the above. 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 1

Which type of congenital cataract presents with a disc of opacity involving the fetal and embryonal nucleus with many white dots resembling dust?

Accepted Answer

Pulverulent cataract

Answer

Lamellar cataract

Answer

Punctate cataract

Answer

Coronary cataract

Question 2

What is the mode of inheritance for congenital cataract?

Accepted Answer

Autosomal dominant

Answer

Autosomal recessive

Answer

X-linked recessive

Answer

X-linked dominant

Question 3

The SRK formula is used to calculate:

Accepted Answer

Power of intraocular lens

Answer

Corneal curvature

Answer

Corneal endothelial cell count

Answer

Extent of retinal detachment

Question 4

The power of an intraocular lens is determined by which of the following measurements?

Accepted Answer

Keratometry

Answer

Retinoscopy

Answer

Ophthalmoscopy

Answer

Biometry

Question 5

What is the most common type of senile cataract?

Accepted Answer

Cuneiform

Answer

Nuclear

Answer

Cupuliform

Answer

None of the above

Question 6

Dislocation of the lens is seen in all the following conditions except?

Accepted Answer

Congenital Rubella

Answer

Marchesani's Syndrome

Answer

Marfan Syndrome

Answer

Homocystinuria

Question 7

Which of the following is a cause of anterior polar cataract?

Accepted Answer

Perforating corneal injury

Answer

Diabetes Mellitus

Answer

Irradiation

Answer

Chalcosis

Question 8

Which of the following can cause cataracts?

Accepted Answer

All of the above

Answer

Hypoparathyroidism

Answer

Cigarette smoking

Answer

Non-ionizing radiation

Question 9

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

Accepted Answer

Lowe syndrome

Answer

Alport syndrome

Answer

Marfan syndrome

Answer

Homocystinuria

Question 10

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

Accepted Answer

All of the above

Answer

Hypoparathyroidism

Answer

Homocystinuria

Answer

Congenital rubella

Diseases of the Lens — MCQs

Diseases of the Lens — MCQs

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