Diseases of the Lens — MCQs

Diseases of the Lens Indian Medical PG Practice Questions and MCQs

Question 231: Which is the thinnest part of the lens of the eye?

A. Anterior pole
B. Posterior pole (Correct Answer)
C. Posterior capsule
D. Apex

Explanation: ### Explanation The crystalline lens is an avascular, transparent, biconvex structure enclosed within a hyaline membrane called the **lens capsule**. The thickness of this capsule varies significantly across different zones, which is a high-yield anatomical fact for surgical considerations. **Why the Correct Answer is Right:** The **posterior pole** (Option B) is the thinnest part of the entire lens capsule, measuring approximately **2.8 to 4 μm**. This extreme thinness makes it the most vulnerable site for accidental rupture during cataract surgery (specifically during cortical aspiration or polishing). **Analysis of Incorrect Options:** * **Anterior Pole (A):** While the anterior capsule is thicker than the posterior pole (approx. 14 μm), it is not the thickest part. It is, however, the site where the continuous curvilinear capsulorhexis (CCC) is performed. * **Posterior Capsule (C):** This is a general term. While the posterior capsule is thinner than the anterior capsule overall, the specific thinnest point is localized at the **pole**. * **Apex (D):** This is not a standard anatomical term for lens thickness. The **pre-equatorial and post-equatorial regions** (near the insertion of zonules) are actually the **thickest** parts of the lens capsule (approx. 17–23 μm). **Clinical Pearls for NEET-PG:** 1. **Thickest part of the lens capsule:** The pre-equatorial and post-equatorial zones (not the poles). 2. **Thinnest part of the lens capsule:** Posterior pole (4 μm). 3. **Embryology:** The lens capsule is a true basement membrane secreted by the lens epithelium. 4. **Surgical Significance:** The fragility of the posterior pole is why **Posterior Capsular Rupture (PCR)** is a dreaded complication in phacoemulsification, potentially leading to vitreous loss.

Question 232: Which is the best intraocular lens (IOL) position?

A. Anterior chamber
B. Posterior chamber (Correct Answer)
C. Iris supported
D. Angle supported

Explanation: **Explanation:** The **Posterior Chamber (PC-IOL)** is the gold standard and the most physiological position for an intraocular lens. Specifically, placement **"in-the-bag"** (within the capsular bag) is the ideal location as it mimics the natural position of the crystalline lens. **Why Posterior Chamber is the Best:** 1. **Anatomical Position:** It is located behind the iris, maintaining the normal anatomy of the anterior segment. 2. **Reduced Complications:** It minimizes contact with the corneal endothelium, iris, and the trabecular meshwork, leading to lower rates of corneal edema, uveitis, and secondary glaucoma. 3. **Optical Stability:** It provides better centration and a more stable refractive outcome with minimal image magnification (approx. 1–2%). **Why Other Options are Incorrect:** * **Anterior Chamber (A-IOL) & Angle Supported:** These are placed in front of the iris. They carry a higher risk of damaging the corneal endothelium (leading to pseudophakic bullous keratopathy) and causing chronic inflammation or secondary glaucoma due to proximity to the drainage angle. * **Iris Supported:** These lenses (e.g., Iris Claw lens) are fixed to the iris tissue. They are associated with chronic low-grade iritis, iris atrophy, and pupillary distortion. **High-Yield Clinical Pearls for NEET-PG:** * **Ideal Site:** Capsular bag (In-the-bag). * **Second Best Site:** Ciliary Sulcus (if the posterior capsule is ruptured but peripheral support remains). * **IOL Power Calculation:** Most commonly uses the **SRK-II or SRK/T formula**. * **Material of Choice:** Foldable **Hydrophobic Acrylic** is currently preferred for its low rate of Posterior Capsular Opacification (PCO).

Question 233: Which of the following are complications of cataract surgery?

A. Endophthalmitis, Optic neuropathy, Retinal detachment, Vitreous loss
B. Optic neuropathy, Retinal detachment, Vitreous loss, Lagophthalmos
C. Endophthalmitis, Optic neuropathy, Vitreous loss, Lagophthalmos
D. Endophthalmitis, Retinal detachment, Vitreous loss (Correct Answer)

Explanation: **Explanation:** Cataract surgery, while highly successful, involves intraocular maneuvers that carry specific risks. The correct answer (D) identifies three classic complications: 1. **Vitreous Loss:** An intraoperative complication occurring due to posterior capsular rupture (PCR). It increases the risk of subsequent issues like glaucoma and retinal detachment. 2. **Endophthalmitis:** The most dreaded postoperative complication. It is an acute intraocular inflammation (usually bacterial) that can lead to permanent vision loss if not treated urgently. 3. **Retinal Detachment (RD):** Pseudophakic RD is a known late complication, especially in patients with high myopia or those who experienced intraoperative vitreous loss. **Analysis of Incorrect Options:** * **Optic Neuropathy:** While Ischemic Optic Neuropathy can rarely occur post-surgery due to fluctuations in intraocular pressure, it is not considered a standard or common complication of cataract surgery compared to the others listed. * **Lagophthalmos:** This is the inability to close the eyelids completely. It is typically a complication of **eyelid surgeries** (like ptosis correction) or facial nerve palsy, not intraocular cataract surgery. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of Endophthalmitis:** *Staphylococcus epidermidis* (Source: Patient's own flora). * **Toxic Anterior Segment Syndrome (TASS):** An acute sterile inflammation occurring within 12–24 hours post-surgery, often confused with endophthalmitis. * **After-cataract:** Posterior Capsular Opacification (PCO) is the **most common late complication** of cataract surgery, treated with YAG laser capsulotomy. * **Irvine-Gass Syndrome:** Cystoid macular edema (CME) occurring after cataract surgery.

Question 234: The early changes in corticosteroid-induced cataract are in the form of:

A. Central posterior subcapsular lens changes (Correct Answer)
B. Anterior conical lens changes
C. Nuclear changes
D. Diffuse lens changes

Explanation: **Explanation:** The hallmark of **corticosteroid-induced cataracts** is the development of **Central Posterior Subcapsular (PSC) opacities**. This occurs regardless of the route of administration (topical, systemic, or inhaled). 1. **Why Option A is Correct:** Steroids interfere with the active transport of electrolytes and water in the lens fibers. This leads to the migration of lens epithelial cells from the equator toward the posterior pole. These cells enlarge and become "bladder cells" (Wedl cells), forming a granular opacity directly under the posterior capsule, typically in the central visual axis. 2. **Why Incorrect Options are Wrong:** * **Option B (Anterior conical):** This is characteristic of *Lenticonus* (as seen in Alport syndrome), not steroid use. * **Option C (Nuclear):** Nuclear sclerosis is primarily associated with senile (age-related) cataracts or smoking, characterized by hardening and yellowing of the lens nucleus. * **Option D (Diffuse):** While advanced steroid cataracts can eventually involve the whole lens, the *early* and classic presentation is localized to the posterior subcapsular region. **High-Yield Clinical Pearls for NEET-PG:** * **Dose-Dependency:** Steroid cataracts are both dose-dependent and duration-dependent. * **Visual Impact:** PSC cataracts affect vision significantly, especially in bright light (due to miosis) and for near work. * **Reversibility:** Unlike steroid-induced glaucoma (which may resolve), steroid-induced cataracts are generally **irreversible** even after stopping the medication. * **Differential Diagnosis:** PSC opacities are also seen in **Diabetes Mellitus**, **Ionizing Radiation**, and **Chronic Uveitis**.

Question 235: What is the earliest clinical feature of senile cataract?

A. Glare (Correct Answer)
B. Frequent change of glasses
C. Colored halos
D. Unifocal polyopia

Explanation: ### Explanation **Correct Answer: A. Glare** The earliest clinical feature of a senile cataract is **glare** (intolerance to bright light). This occurs due to the **scattering of light** as it passes through the opacifying lens. In the early stages, even minimal changes in the refractive index of the lens fibers cause light rays to deviate from their normal path, leading to discomfort and blurred vision in bright sunlight or when facing oncoming headlights at night. **Analysis of Incorrect Options:** * **B. Frequent change of glasses:** This occurs due to **index myopia** (progressive increase in the refractive index of the nucleus). While a common early sign, it typically follows the initial onset of glare and light scattering. * **C. Colored halos:** These are caused by the splitting of white light into its spectral components by water droplets (morgagnian fluid) between lens fibers. This is more characteristic of **immature cortical cataracts** or can be a sign of angle-closure glaucoma. * **D. Unifocal polyopia:** This refers to seeing multiple images through a single eye. It is caused by irregular refraction through different areas of the lens with varying densities. It is a classic symptom but usually manifests after the initial glare. **Clinical Pearls for NEET-PG:** * **Earliest Symptom:** Glare (especially in posterior subcapsular cataracts). * **Earliest Sign:** Vacuoles and water clefts (seen on slit-lamp examination in cortical cataracts). * **Second Sight:** A phenomenon seen in nuclear cataracts where the development of index myopia allows an elderly patient to read without near-glasses again. * **Cuneiform Cataract:** The most common type of senile cortical cataract, characterized by wedge-shaped opacities in the periphery.

Question 236: Which gene is most often implicated in congenital cataract and is a mutation of alpha crystallin?

A. GLC3A
B. PAX6
C. PITX2
D. CRYAA (Correct Answer)

Explanation: **Explanation:** **CRYAA** is the correct answer because it encodes the **alpha-A crystallin** protein. Crystallins are the major structural proteins of the ocular lens, responsible for its transparency and high refractive index. Alpha-crystallins also function as molecular chaperones that prevent the aggregation of denatured proteins. Mutations in the **CRYAA gene** (located on chromosome 21) lead to protein misfolding and opacification, resulting in various forms of autosomal dominant congenital cataracts (most commonly zonular or nuclear types). **Analysis of Incorrect Options:** * **GLC3A (Option A):** This gene (encoding the CYP1B1 enzyme) is the most common genetic cause of **Primary Congenital Glaucoma**, not cataracts. * **PAX6 (Option B):** Known as the "master control gene" for eye development. Mutations are primarily associated with **Aniridia**, though it can cause Peter’s anomaly and secondary cataracts. * **PITX2 (Option C):** This gene is involved in the development of the anterior segment. Mutations typically lead to **Axenfeld-Rieger Syndrome**, characterized by iris hypoplasia and polycoria. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of Congenital Cataract:** Idiopathic (followed by genetic/hereditary factors). * **Most common infection:** Rubella (presents with "pearly white" nuclear cataract). * **Most common metabolic cause:** Galactosemia (classic "oil droplet" cataract). * **Crystallin distribution:** Alpha, Beta, and Gamma crystallins make up 90% of lens proteins. Alpha-crystallin is the largest and acts as a heat-shock protein.

Question 237: Type of cataract in chalcosis is

A. Sunflower cataract (Correct Answer)
B. Blue dot Cataract
C. Snowflake cataract
D. Polychromatic lustre

Explanation: **Explanation:** **1. Why Sunflower Cataract is correct:** Chalcosis refers to the intraocular deposition of copper, typically following a copper-containing intraocular foreign body. Copper ions deposit in the basement membranes of the eye. In the lens, copper accumulates under the **posterior lens capsule**, radiating outwards in a petal-like configuration from the center. This characteristic appearance resembles a **Sunflower**. It is important to note that sunflower cataracts are usually reversible if the foreign body is removed and rarely cause significant visual impairment. **2. Why the other options are incorrect:** * **Blue dot Cataract (Punctate cataract):** This is the most common type of **congenital cataract**. It appears as small, bluish, opaque dots scattered throughout the lens and is usually non-progressive and asymptomatic. * **Snowflake cataract:** This is the classic finding in **Juvenile Diabetes Mellitus**. It consists of subcapsular white opacities that resemble snowflakes, caused by osmotic swelling of lens fibers due to sorbitol accumulation. * **Polychromatic lustre:** This refers to a "rainbow-like" play of colors seen at the posterior pole of the lens. It is the hallmark of a **Complicated Cataract**, occurring secondary to intraocular inflammation (like chronic uveitis) or high myopia. **3. High-Yield Clinical Pearls for NEET-PG:** * **Kayser-Fleischer (KF) Ring:** Copper deposition in the **Descemet’s membrane** of the cornea (seen in Wilson’s disease and Chalcosis). * **Siderosis Bulbi:** Iron deposition in the eye, leading to a **rusty brown** discoloration of the lens (Cataracta lentis browni). * **Glass-blower’s cataract:** True exfoliation of the anterior capsule due to infrared radiation. * **Rosette-shaped cataract:** Classically seen in **Concussive (Traumatic)** ocular injury.

Question 238: A 32-year-old patient presents with blurred vision, photophobia, and mild ocular pain. Examination reveals aqueous flares and keratic precipitates in the anterior chamber. What is the likely diagnosis?

A. D. Iridocyclitis (Correct Answer)
B. A. Intermediate uveitis
C. B. Posterior uveitis
D. C. Toxoplasma uveitis

Explanation: ***D. Iridocyclitis***- **Iridocyclitis** is the preferred term for **anterior uveitis**, which involves inflammation of the iris and ciliary body.- The hallmark signs of **aqueous flares** (protein and cells in the anterior chamber) and **keratic precipitates** (inflammatory cell deposits on the corneal endothelium) confirm that the inflammation is localized to the **anterior chamber**.*A. Intermediate uveitis*- Characterized by inflammation primarily in the **vitreous** and **pars plana**, often referred to as *vitritis*.- While it causes blurred vision and floaters, the anterior chamber signs like *aqueous flares* and *keratic precipitates* are not the dominant features; fundoscopy may reveal **snowbanking**.*B. Posterior uveitis*- Involves inflammation of the **retina** and/or **choroid** (e.g., retinitis or choroiditis), often causing significant central vision loss and scotomas.- The primary findings are located in the posterior segment (fundus lesions), and the anterior chamber is often **quiet** or shows only mild reaction.*C. Toxoplasma uveitis*- This is a specific cause of **posterior uveitis**, typically presenting as a focus of **necrotizing retinitis** adjacent to an old, pigmented scar.- Although it can cause a *secondary* anterior chamber reaction, the primary diagnostic feature is the specific retinal lesion, which is not mentioned in this presentation.

Question 239: A patient presented 2 weeks after cataract surgery with decreased vision. On examination, there were anterior chamber cells and flare with hazy vitreous. What is the most likely cause and organism?

A. Endophthalmitis with Staphylococcus
B. Endophthalmitis with Propionibacterium (Correct Answer)
C. Sympathetic ophthalmia
D. Toxic anterior segment syndrome

Explanation: ***Endophthalmitis with Propionibacterium*** - ***Propionibacterium acnes*** (now ***Cutibacterium acnes***) is the classic organism responsible for **delayed-onset** or subacute endophthalmitis, which typically presents weeks to months following cataract surgery. - This indolent infection is characterized by low-grade inflammation, **vitritis**, and often subtle findings, making the 2-week history highly suggestive of this causative agent. ***Endophthalmitis with Staphylococcus*** - **Acute post-operative endophthalmitis**, most commonly caused by *Staphylococcus epidermidis*, typically presents much earlier, usually within **1 to 7 days** post-surgery, with rapid decline in vision. - *Staphylococcus aureus* causes a highly virulent, fulminant acute infection that would almost certainly present less than 2 weeks post-op. ***Sympathetic ophthalmia*** - This is a rare, bilateral, granulomatous **panuveitis** that occurs after a penetrating trauma or surgery to one eye. - While it can present weeks after surgery, it is an autoimmune condition and would not typically be caused by a specific pathogen like *Propionibacterium* or *Staphylococcus*. ***Toxic anterior segment syndrome*** - TASS is an acute, **sterile inflammatory** response to non-infectious toxic substances (like detergents or preservatives) introduced during surgery. - TASS presents very early (12–48 hours post-op), is confined mainly to the **anterior segment**, and does not involve significant **vitritis**.

Question 240: An elderly patient presents with white, dandruff-like deposits on the anterior lens surface, seen during slit-lamp examination. What is the most likely diagnosis?

A. Iris cyst
B. Persistent pupillary membrane
C. Pigment dispersion syndrome
D. Pseudoexfoliation syndrome (Correct Answer)

Explanation: ***Pseudoexfoliation syndrome*** - The pathognomonic finding of **white, dandruff-like material** deposited on the **anterior lens capsule** (often forming a characteristic clear central zone and peripheral zone separated by a clear space) is indicative of Pseudoexfoliation syndrome. - This material is an **abnormal fibrillar glycoprotein** that can block the trabecular meshwork, elevating intraocular pressure and predisposing the patient to **pseudoexfoliation glaucoma**. *Iris cyst* - An iris cyst appears as a localized, non-transilluminating mass or elevation within the iris stroma or attached to the pupil margin. - It does not present as diffuse **dandruff-like material** covering the lens surface, which is the hallmark of pseudoexfoliation. *Persistent pupillary membrane* - This is a **congenital anomaly** where remnants of the embryonic **tunica vasculosa lentis** persist, appearing as fine strands bridging the pupil or extending from the iris collar to the lens. - They are typically dark, thread-like structures, and are not the widespread **white deposits** usually seen in elderly patients with PEX. *Pigment dispersion syndrome* - This condition involves the dispersion of **iris pigment**, which classically manifests as a **Krukenberg spindle** (vertical pigment line on the corneal endothelium) and dense pigment deposits in the trabecular meshwork. - The deposits are visually **brown/black (pigmentary)**, not white/gray as described in PEX, and they primarily affect the corneal endothelium and trabecular meshwork.

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

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Posterior Capsular Opacification

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Lens Subluxation and Dislocation

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Specialty IOLs

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