Diseases of the Lens — MCQs

Diseases of the Lens Indian Medical PG Practice Questions and MCQs

Question 281: Which type of congenital cataract is commonly associated with significant visual defects?

A. Punctate Cataract
B. Blue dot cataract
C. Fusiform cataract
D. Nuclear cataract (Correct Answer)

Explanation: ***Nuclear cataract*** - It involves the **nucleus** of the lens, which is the central and most visually critical part. - This type of cataract can cause **significant visual impairment** due to its central location and density, impacting early visual development. *Punctate Cataract* - These are **small, dot-like opacities** that are usually clinically insignificant and do not typically cause significant visual defects. - They are often **peripheral** or very fine, thus not obstructing the central visual axis. *Blue dot cataract* - Also known as **cerulean cataract**, this type consists of small, bluish opacities in the lens cortex. - While congenital, it often has **minimal impact on vision** and is frequently observed incidentally. *Fusiform cataract* - This cataract forms in the shape of a **spindle or needle**, usually along the visual axis. - While it can sometimes cause minor visual compromise, its impact is generally **less severe** compared to a dense nuclear cataract.

Question 282: In the context of homocystinuria, which direction does the lens typically subluxate?

A. Inferotemporal
B. Inferonasal (Correct Answer)
C. Superonasal
D. Superotemporal

Explanation: ***Inferonasal*** - In **homocystinuria**, the **ectopia lentis** (lens subluxation) often occurs due to weakening of the **zonular fibers**. - The classic direction for lens subluxation in homocystinuria is **inferior and nasal**. *Inferotemporal* - While lens subluxation can occur in various directions, **inferotemporal** is not the classic or most common presentation in homocystinuria. - This direction is less specific and does not strongly point to homocystinuria as the underlying cause. *Superonasal* - **Superonasal** dislocation of the lens is more characteristic of **Marfan syndrome**, which is important to differentiate from homocystinuria. - This direction helps distinguish different causes of lens ectopia. *Superotemporal* - **Superotemporal** lens subluxation is the hallmark of **Marfan syndrome**, a genetic connective tissue disorder. - This specific finding is crucial for differential diagnosis in patients presenting with lens ectopia.

Question 283: Which type of cataract is associated with the phenomenon known as 'second sight'?

A. Nuclear cataract (Correct Answer)
B. Cortical cataract
C. Zonular cataract
D. Punctate cataract

Explanation: ***Nuclear cataract*** - A nuclear cataract causes the lens to become more **myopic** or nearsighted due to an increase in its **refractive index**. - This temporary increase in nearsightedness can allow elderly individuals who previously needed reading glasses (due to presbyopia) to read without them, a phenomenon known as "**second sight**." *Cortical cataract* - Cortical cataracts primarily affect the **outer layer or cortex** of the lens, appearing as spokes or wedges radiating from the periphery. - They tend to cause **glare** and **reduced peripheral vision**, but generally do not improve near vision. *Zonular cataract* - A zonular cataract is a **congenital type of cataract**, characterized by opacity in specific layers (lamellae) of the lens, often in the fetal nucleus. - It does not typically lead to the "second sight" phenomenon, as it is present from birth and affects vision differently. *Punctate cataract* - Punctate cataracts are small, **dot-like opacities** scattered throughout the lens, often considered benign. - They are usually **incidental findings** and rarely cause significant visual disturbances or "second sight."

Question 284: Which type of cataract is specifically associated with decreased reading ability?

A. Blue dot cataract
B. Nuclear cataract (Correct Answer)
C. Fusiform cataract
D. Punctate cataract

Explanation: ***Nuclear cataract*** - **Nuclear cataracts** cause progressive hardening and yellowing of the lens nucleus with increased refractive index - This produces a **myopic shift** that initially causes **"second sight"** (temporary improvement in near vision) - However, as the cataract progresses, the increasing opacity leads to **overall visual decline affecting both distance and near vision**, including reading ability - Among the given options, nuclear cataract is the most common age-related cataract that significantly impairs vision including reading *Blue dot cataract* - **Blue dot cataracts** (cerulean cataracts) are small, bluish peripheral opacities, usually congenital and stationary - They rarely cause significant visual impairment and do not affect reading ability *Fusiform cataract* - **Fusiform cataracts** are congenital spindle-shaped opacities along the visual axis - While they can affect vision if dense, they are rare and not typically associated with progressive reading difficulty *Punctate cataract* - **Punctate cataracts** are small, scattered dot-like opacities in the lens - They are often congenital or age-related and cause minimal visual disturbance - Not specifically associated with decreased reading ability

Question 285: Sunflower cataract is seen in:

A. Wilson's disease (Correct Answer)
B. Galactosemia
C. Diabetes mellitus
D. Haemochromatosis

Explanation: ***Wilson's disease*** - A **sunflower cataract** is a classic ophthalmological sign of **Wilson's disease**, characterized by **copper deposition** in the lens. - This specific cataract is formed by granular deposits of **copper** in the anterior capsular and subcapsular regions, radiating outwards like a sunflower. *Galactosemia* - **Galactosemia** is associated with **oil droplet cataracts**, which are small, translucent, and centrally located in the lens. - This type of cataract is due to the accumulation of **galactitol**, an osmotically active metabolite, in the lens. *Diabetes mellitus* - **Diabetes mellitus** can cause several types of cataracts, including **"snowflake" cataracts** (in juvenile diabetes) and accelerated **age-related cataracts**. - These cataracts are related to metabolic changes such as **osmotic swelling** and **non-enzymatic glycation** of lens proteins, not copper deposition. *Haemochromatosis* - **Haemochromatosis** is characterized by **iron overload** in various organs, including the liver and heart. - It is not known to cause a specific type of cataract like the sunflower cataract, which is unique to copper deposition.

Question 286: What is the normal water content percentage in the human lens?

A. 64% (Correct Answer)
B. 35%
C. 1%
D. 28%

Explanation: ***64%*** - The human lens is approximately **64% water** and 35% protein, with minor amounts of lipids and carbohydrates. - This specific water content is critical for maintaining its **transparency** and refractive properties. *35%* - This percentage represents the approximate **protein content** of the human lens, not its water content. - The lens is one of the most protein-dense organs in the body, crucial for its optical function. *1%* - A water content of 1% is far too low for any living mammalian tissue, and such a low percentage would result in a **desiccated**, non-functional lens. - This value doesn't reflect the physiological composition of the human lens. *28%* - This percentage is significantly lower than the actual water content of the lens and would compromise its **structural integrity** and transparency. - A lens with only 28% water would likely be non-functional and involved in conditions like severe dehydration.

Question 287: A patient complains of an inability to read a newspaper, particularly in bright sunlight. What is the most likely diagnosis?

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

Explanation: ***Posterior subcapsular cataract*** - This type of cataract causes significant **glare** and **photophobia**, making it difficult to read in bright light due to opacities located at the **posterior lens capsule**. - The patient experiences worsening vision in **bright light** conditions because the constricted pupil directs more light through the **central posterior opacity**, which lies directly in the visual axis. *Nuclear cataract* - Patients with **nuclear cataracts** typically experience **myopic shift** and improved near vision (second sight) due to increased refractive power of the lens. - Vision is usually worse in **dim light** conditions because of pupillary dilation, which allows more light to pass through the central opacity. *Cortical cataract* - Characterized by **spoke-like opacities** that start in the periphery and extend inward. - While it can cause glare, vision often remains good until the opacities encroach upon the **visual axis**, and it doesn't specifically cause worsening vision in bright light to the same degree as PSC. *Congenital cataract* - Present at birth or shortly after, and symptoms depend on the density and location of the opacity. - While it affects vision, the specific complaint of difficulty reading in bright sunlight is not a typical distinguishing feature of **congenital cataracts**.

Question 288: A 76-year-old female presents with difficulty reading. Bilateral white opacifications consistent with cataract formation are observed. In which structure are these opacifications located?

A. Aqueous humor
B. Cornea
C. Lens (Correct Answer)
D. Optic nerve

Explanation: ***Lens*** - **Cataracts** are defined by the **clouding of the natural lens** of the eye, which causes blurred vision and difficulty with activities like reading. - The condition is very common, especially among older adults, and affects the **bilateral vision** as described in the case. *Aqueous humor* - The **aqueous humor** is a clear fluid that fills the space between the cornea and the lens; it is not the structure that becomes opaque in cataracts. - Problems with aqueous humor are typically associated with glaucoma (due to increased intraocular pressure) rather than cataract formation. *Cornea* - The **cornea** is the transparent outer layer of the eye that helps focus light, but it does not develop cataracts. - Opacities in the cornea (e.g., from injuries or infections) would be described differently and produce different visual symptoms. *Optic nerve* - The **optic nerve** transmits visual information from the retina to the brain; it is a nerve, not a structure where light focuses or where cataracts develop. - Damage to the optic nerve typically leads to vision loss or blind spots, not blurred vision from opacification.

Question 289: A cause of anterior polar cataract is

A. DM
B. Perforating corneal injury (Correct Answer)
C. Irradiation
D. Chalcosis

Explanation: **Perforating corneal injury** - A **perforating corneal injury** can directly disrupt the anterior lens capsule, leading to localized opacification and the formation of an **anterior polar cataract**. - This type of cataract is often *fibrous* and *subcapsular*, forming as a reaction to trauma, sometimes with lens epithelial proliferation or metaplasia into fibroblasts. *DM* - **Diabetes mellitus** typically causes other types of cataracts, such as **snowflake cataracts** (in younger patients with uncontrolled diabetes) or accelerated **senile cataracts**. - Diabetic cataracts are metabolic in origin, affecting lens metabolism globally, rather than causing a localized polar opacity directly from injury. *Irradiation* - **Irradiation** (e.g., from X-rays or nuclear radiation) can induce cataracts, but these are typically **posterior subcapsular cataracts**. - The lens epithelium, particularly at the posterior pole, is highly sensitive to radiation, leading to migration and opacification. *Chalcosis* - **Chalcosis** refers to ocular changes due to copper deposition, classically causing a **sunflower cataract** (in Wilson's disease or copper intraocular foreign bodies). - This cataract has a distinctive greenish-brown discoloration and a petal-like appearance, which is different from an anterior polar opacity.

Question 290: Which of the following is NOT a known cause of posterior subcapsular cataract?

A. Diabetes mellitus
B. Wilson's Disease (Correct Answer)
C. Myotonic dystrophy
D. Ionizing radiation

Explanation: ***Wilson's Disease*** - This is the **CORRECT ANSWER** because Wilson's disease does **NOT** cause posterior subcapsular cataract. - **Wilson's disease** is characterized by a **Kayser-Fleischer ring** (copper deposition in Descemet's membrane of the cornea) and less commonly by a **sunflower cataract** (copper deposition in the **anterior lens capsule**, not posterior). - The sunflower cataract has a characteristic appearance with petal-like opacities radiating from the center, but it affects the anterior capsule, not the posterior subcapsular region. *Myotonic dystrophy* - **Myotonic dystrophy** is a well-known cause of specific cataracts, including a distinctive **"Christmas tree" cataract**, which often begins as a **posterior subcapsular cataract**. - This condition is a systemic autosomal dominant disorder affecting multiple systems, including skeletal muscle, cardiac muscle, and the eyes. *Ionizing radiation* - Exposure to **ionizing radiation**, such as X-rays or radiation therapy, is a classic and recognized risk factor for developing **posterior subcapsular cataracts**. - The lens epithelial cells at the posterior pole are highly susceptible to damage from radiation, leading to migration and abnormal differentiation causing opacification. *Diabetes mellitus* - **Diabetes mellitus** is a significant risk factor for various types of cataracts, including both **snowflake cataracts** (in acute uncontrolled diabetes) and more commonly, **posterior subcapsular cataracts** in chronic diabetes. - High blood glucose levels lead to osmotic changes (sorbitol accumulation via the polyol pathway) and oxidative stress within the lens, contributing to cataract formation.

Practice by Chapter

Lens Anatomy and Physiology

Practice Questions

Age-Related Cataract

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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

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Complications of Cataract Surgery

Practice Questions

Posterior Capsular Opacification

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Lens Subluxation and Dislocation

Practice Questions

Specialty IOLs

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