Contact Lens Practice Questions

Q: Onion peel appearance of the lens is characteristic of which of the following conditions?

Posterior polar cataract. **Explanation:** **Posterior Polar Cataract (PPC)** is a congenital, often bilateral, discoid opacity located at the posterior pole of the lens. It is characterized by a dense central opacity surrounded by concentric rings of varying density, which gives it the classic **"onion peel"** or **"bull’s eye"** appearance. **Why the correct answer is right:** The "onion peel" appearance occurs because the opacity is composed of malformed lens fibers that have migrated posteriorly. These fibers are arranged in concentric layers around a central core, mimicking the layers of an onion. This condition is clinically significant because the posterior capsule is often extremely thin or even absent at the site of the opacity, leading to a high risk of **posterior capsular rupture (PCR)** during surgery. **Why the incorrect options are wrong:** * **Posterior Subcapsular Cataract (PSC):** Typically presents with a **"cupuliform"** or **"sandpaper"** appearance. It is associated with steroid use, diabetes, and radiation. * **Anterior Subcapsular Cataract:** Often appears as a white plaque or "pyramidal" shape. It is frequently seen following acute angle-closure glaucoma (Glaukomflecken) or trauma. * **Anterior Polar Cataract:** Usually a small, central, white opacity on the anterior capsule. It is often stationary and rarely affects vision significantly. **High-Yield Clinical Pearls for NEET-PG:** * **Surgical Caution:** In PPC, hydrodissection is strictly **contraindicated** to avoid rupturing the fragile posterior capsule. Hydrodelineation is the preferred technique. * **Genetics:** Most cases are autosomal dominant (AD) and associated with mutations in the **PITX3** gene. * **Dalgleish’s Sign:** The presence of satellite opacities around the main polar cataract.

Q: A 55-year-old patient complains of decreased distance vision but no longer requires near glasses for near work. What is the most likely cause?

Nuclear sclerosis. **Explanation:** The clinical scenario describes a phenomenon known as **"Second Sight."** This occurs due to the development of **Nuclear Sclerosis** (a type of senile cataract). **Why Nuclear Sclerosis is correct:** As the lens nucleus becomes increasingly dense and sclerotic, its refractive index increases. This results in **index myopia** (a myopic shift). For a presbyopic patient (like this 55-year-old), this newly acquired myopia compensates for their loss of near vision, allowing them to read without glasses again. However, because the eye is now more myopic, distance vision becomes blurred. **Why the other options are incorrect:** * **Posterior Subcapsular Cataract (PSC):** Typically causes significant glare and profound vision loss in bright light (due to miosis). It does not cause a myopic shift; instead, it affects near vision more severely than distance vision. * **Anterior Subcapsular Cataract:** Often associated with trauma or specific drugs (like chlorpromazine). It does not lead to the "second sight" phenomenon. * **Zonular (Lamellar) Cataract:** This is the most common type of **congenital** cataract, usually affecting a specific shell of lens fibers. It is not a degenerative condition of the elderly. **High-Yield Clinical Pearls for NEET-PG:** * **Second Sight:** Pathognomonic for early nuclear sclerosis. * **Grading:** Nuclear cataracts are graded using the **LOCS III** (Lens Opacities Classification System). * **Refractive Shifts:** Nuclear sclerosis causes **Myopic shift**, while cortical cataracts can sometimes cause **Hyperopic shift**. * **Cataract of Diabetes:** True diabetic cataract is "Snowflake cataract," but DM also accelerates the formation of senile nuclear sclerosis.

Q: What is the major function of Major Intrinsic Protein 26 (MIP-26)?

Transport of water in the lens. **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 the total membrane protein content. 1. **Why Option B is Correct:** MIP-26 functions primarily as a water channel (Aquaporin). The lens is an avascular structure that relies on a unique internal circulatory system to maintain transparency. MIP-26 facilitates the movement of water and small solutes between lens fibers. It plays a critical role in maintaining lens dehydration and osmotic balance; mutations in the gene encoding MIP-26 are associated with congenital cataracts. 2. **Why Other Options are Incorrect:** * **Option A:** Glucose transport in the lens is primarily mediated by **GLUT-1** receptors located in the lens epithelium. * **Option C:** The lens does not have a "diffusion barrier" in this context; rather, it utilizes **Gap Junctions** (Connexins like Cx43, Cx46, and Cx50) to allow the free flow of ions and metabolites. * **Option D:** The lens capsule is a modified basement membrane composed mainly of **Type IV Collagen** and glycosaminoglycans, not intrinsic membrane proteins like MIP-26. **High-Yield Clinical Pearls for NEET-PG:** * **MIP-26 = Aquaporin-0:** Remember this synonym, as the exam may use them interchangeably. * **Lens Crystallins:** These are soluble proteins (Alpha, Beta, Gamma) that maintain lens clarity. Alpha-crystallin also acts as a **molecular chaperone** to prevent protein aggregation. * **Metabolism:** The lens derives most of its energy from **anaerobic glycolysis** (90%). * **Cataractogenesis:** Any disruption in the function of MIP-26 or Connexins leads to increased water content and protein denaturation, resulting in lens opacification.

Q: The cataract seen in patients with CTG/CUG trinucleotide repeats is?

Christmas tree cataract. ### Explanation **Correct Answer: C. Christmas tree cataract** **Medical Concept:** The question refers to **Myotonic Dystrophy (Type 1)**, which is caused by an unstable expansion of **CTG trinucleotide repeats** in the *DMPK* gene (Type 2 involves CCTG repeats). The hallmark ocular finding in these patients is the **Christmas tree cataract**. This is characterized by polychromatic, needle-like crystals (cholesterol deposits) in the deep cortex and subcapsular regions of the lens that glisten with various colors under slit-lamp examination. Over time, these evolve into a more classic "stellate" posterior subcapsular opacification. **Analysis of Incorrect Options:** * **A. Snow flake cataract:** This is characteristic of **Diabetes Mellitus** (specifically Juvenile/Type 1 DM). It consists of subcapsular white opacities that resemble snowflakes. * **B. True exfoliation cataract:** This involves the delamination of the anterior lens capsule due to **infrared radiation (heat) exposure**, classically seen in glassblowers or furnace workers ("Glassblower’s cataract"). It is distinct from Pseudoexfoliation syndrome. **High-Yield Clinical Pearls for NEET-PG:** * **Myotonic Dystrophy:** Look for the triad of "Frontal balding, Myotonia (delayed muscle relaxation), and Christmas tree cataract." * **Genetics:** It exhibits **Anticipation** (symptoms become more severe/earlier in successive generations) due to the expansion of CTG repeats. * **Other "Tree" signs in Ophthalmology:** * *Dendritic ulcer:* Herpes Simplex Keratitis. * *Arborescent (Tree-like) pigmentation:* Seen in lightning strikes (Lichtenberg figures). * **Sunflower Cataract:** Seen in Wilson’s Disease (Copper deposition). * **Oil Droplet Cataract:** Seen in Galactosemia.

Q: Soemmering's ring is seen in which of the following conditions?

After cataract. **Explanation:** **Soemmering’s Ring** is a classic morphological type of **After-cataract** (Posterior Capsular Opacification). It occurs following extracapsular cataract extraction (ECCE) or trauma when the central part of the lens is removed, but peripheral lens epithelial cells (LECs) remain trapped between the anterior and posterior capsular flaps. These cells proliferate and undergo metamorphosis, forming a doughnut-shaped ring of cortical matter in the periphery of the capsular bag. While the center remains clear, the ring can cause visual disturbances if it displaces or if the cells migrate centrally (Elschnig’s pearls). **Analysis of Options:** * **Option A (Posterior subcapsular cataract):** This is a primary cataract located in the visual axis just in front of the posterior capsule, often associated with steroid use or diabetes. It is not a postoperative complication. * **Option C (Endophthalmitis):** This is a severe intraocular inflammation/infection. While it can occur post-surgery, it presents with hypopyon and vitreous exudates, not capsular rings. * **Option D (Fuchs heterochromia iridis):** This is a chronic non-granulomatous uveitis characterized by iris atrophy and heterochromia. While it leads to complicated cataracts, it does not specifically form Soemmering’s ring. **High-Yield Clinical Pearls for NEET-PG:** 1. **Elschnig’s Pearls:** Another form of after-cataract where LECs migrate to the posterior capsule, appearing like "clusters of grapes" or "fish eggs." 2. **Treatment:** The gold standard for symptomatic after-cataract is **Nd:YAG Laser Capsulotomy**. 3. **Prevention:** Modern IOL designs (square-edge optics) and thorough cortical aspiration significantly reduce the incidence of Soemmering’s ring.

Q: After cataract surgery, when are glasses typically prescribed?

Six weeks. **Explanation:** The correct answer is **Six weeks (Option B)**. **Why it is correct:** Following cataract surgery (especially with traditional incisions), the cornea undergoes a period of structural remodeling and wound healing. During the first few weeks, the surgical incision causes temporary corneal edema and induced astigmatism. It takes approximately **6 weeks** for the wound to achieve tectonic stability and for the corneal curvature (refraction) to stabilize. Prescribing glasses before this "refractive stabilization" would result in an inaccurate prescription as the eye's power continues to shift. **Analysis of incorrect options:** * **Two weeks (Option A):** At this stage, the wound is still healing, and sutures (if used) are still tight, causing significant temporary astigmatism. Refraction at this point is highly unstable. * **Twelve weeks (Option C) & Twenty weeks (Option D):** While the eye is stable at these points, waiting this long is clinically unnecessary and delays the patient’s visual rehabilitation. By 6 weeks, the refraction is sufficiently permanent for definitive corrective lenses. **Clinical Pearls for NEET-PG:** * **Modern Trend:** With modern **MICS (Micro-incision Cataract Surgery)** or Phacoemulsification using sub-2.8mm valvular incisions, stabilization occurs faster (often by 2–3 weeks). However, for standard examination purposes, **6 weeks** remains the classical gold standard. * **Aphakia vs. Pseudophakia:** In cases of aphakia (no IOL), high-plus glasses (+10D) are prescribed. In pseudophakia (IOL present), simple cylindrical or reading glasses are usually required. * **Steroid Taper:** The 6-week mark usually coincides with the completion of the post-operative topical steroid taper.

Q: Which condition is typically associated with bilateral inferior subluxation of the lens?

Homocystinuria. **Explanation:** The correct answer is **Homocystinuria**. Lens subluxation (ectopia lentis) occurs due to the weakening or destruction of the ciliary zonules. 1. **Homocystinuria:** This is an autosomal recessive metabolic disorder caused by a deficiency of the enzyme cystathionine beta-synthase. The accumulation of homocysteine interferes with the cross-linking of collagen and fibrillin. In this condition, the zonules are brittle and completely disintegrated. Characteristically, the lens displaces **inferiorly and nasally** (Down and In). Patients also present with intellectual disability, a marfanoid habitus, and a high risk of thromboembolism. 2. **Incorrect Options:** * **Marfan’s Syndrome:** This is the most common cause of heritable ectopia lentis. However, the subluxation is typically **superior and temporal** (Up and Out). The zonules remain intact but are stretched. * **Hyperinsulinemia:** This is not a recognized cause of lens subluxation. Metabolic shifts in insulin levels are more commonly associated with refractive changes or cataract formation. * **Ocular Trauma:** While trauma is the **most common overall cause** of lens subluxation, it is usually unilateral and does not follow a specific directional pattern like genetic syndromes. **NEET-PG High-Yield Pearls:** * **Direction Mnemonic:** **M**arfan = **M**ore (Up); **H**omocystinuria = **H**eavy (Down). * **Zonular Integrity:** Zonules are **stretched** in Marfan’s but **broken/absent** in Homocystinuria. * **Other associations:** Ectopia lentis is also seen in **Weill-Marchesani syndrome** (inferior subluxation + microspherophakia) and **Sulfite oxidase deficiency** (dislocation at birth).

Question 1

Onion peel appearance of the lens is characteristic of which of the following conditions?

Accepted Answer

Posterior polar cataract

Answer

Posterior subcapsular cataract

Answer

Anterior subcapsular cataract

Answer

Anterior polar cataract

Question 2

What is the ideal fluid for irrigation during Extra Capsular Cataract Extraction (ECCE)?

Accepted Answer

Balanced salt solution + glutathione

Answer

Normal saline to dextrose

Answer

Normal saline

Answer

Balanced salt solution

Question 3

A 55-year-old patient complains of decreased distance vision but no longer requires near glasses for near work. What is the most likely cause?

Accepted Answer

Nuclear sclerosis

Answer

Posterior subcapsular cataract

Answer

Zonular cataract

Answer

Anterior subcapsular cataract

Question 4

What is the major function of Major Intrinsic Protein 26 (MIP-26)?

Accepted Answer

Transport of water in the lens

Answer

Glucose transport in the lens

Answer

Diffusion barrier

Answer

Capsule of the lens

Question 5

In a pseudophakic eye, which of the following rays penetrate up to the retina?

Accepted Answer

UV-A

Answer

UV-B

Answer

UV-C

Answer

Infrared

Question 6

The cataract seen in patients with CTG/CUG trinucleotide repeats is?

Accepted Answer

Christmas tree cataract

Answer

Snow flake cataract

Answer

True exfoliation cataract

Answer

None of the above

Question 7

Soemmering's ring is seen in which of the following conditions?

Accepted Answer

After cataract

Answer

Posterior subcapsular cataract

Answer

Endophthalmitis

Answer

Fuchs heterochromia iridis

Question 8

After cataract surgery, when are glasses typically prescribed?

Accepted Answer

Six weeks

Answer

Two weeks

Answer

Twelve weeks

Answer

Twenty weeks

Question 9

Which condition is typically associated with bilateral inferior subluxation of the lens?

Accepted Answer

Homocystinuria

Answer

Marfan's syndrome

Answer

Hyperinsulinemia

Answer

Ocular trauma

Question 10

Which of the following is NOT a treatment for pediatric cataract?

Accepted Answer

Intracapsular cataract extraction

Answer

Phaco-aspiration

Answer

Corneo-scleral tunnel technique

Answer

Intraocular lens implantation

Contact Lens — MCQs

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