Contact Lens — MCQs

Contact Lens Indian Medical PG Practice Questions and MCQs

Question 61: Onion peel appearance of the lens is characteristic of which of the following conditions?

A. Posterior subcapsular cataract
B. Anterior subcapsular cataract
C. Posterior polar cataract (Correct Answer)
D. Anterior polar cataract

Explanation: **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.

Question 62: What is the ideal fluid for irrigation during Extra Capsular Cataract Extraction (ECCE)?

A. Normal saline to dextrose
B. Normal saline
C. Balanced salt solution
D. Balanced salt solution + glutathione (Correct Answer)

Explanation: **Explanation:** The primary goal of an intraocular irrigating solution during cataract surgery (ECCE/Phacoemulsification) is to maintain the structural integrity of the anterior chamber while protecting the **corneal endothelium**. **Why Option D is Correct:** The corneal endothelium is responsible for maintaining corneal transparency through an active pump mechanism. **Balanced Salt Solution (BSS) Plus** (BSS with added **Glutathione, Bicarbonate, and Dextrose**) is considered the "gold standard" because: * **Glutathione:** Acts as a potent antioxidant that protects endothelial cells from oxidative stress and surgical trauma. * **Bicarbonate:** Acts as a buffer to maintain physiological pH. * **Dextrose:** Provides an immediate energy source for the endothelial pump. This combination minimizes corneal edema and ensures faster visual recovery compared to standard solutions. **Analysis of Incorrect Options:** * **A & B (Normal Saline/Dextrose):** Normal saline (0.9% NaCl) is non-buffered and lacks essential ions like Calcium and Magnesium. It is acidic (pH ~5.5) and can cause irreversible damage to the endothelial cell junctions, leading to corneal bullous keratopathy. * **C (Balanced Salt Solution):** While standard BSS is superior to saline because it contains essential electrolytes (K+, Ca2+, Mg2+), it lacks the protective antioxidant properties of glutathione and the buffering capacity of bicarbonate found in BSS Plus. **High-Yield Clinical Pearls for NEET-PG:** * **Ideal pH:** The intraocular environment requires a pH of **7.4**. * **Endothelial Cell Count:** A minimum of **500-800 cells/mm²** is required to maintain corneal clarity; using sub-optimal fluids during surgery can drop the count below this threshold. * **Additives:** If BSS Plus is unavailable, surgeons often add **Adrenaline (1:1000, preservative-free)** to the irrigating fluid to maintain pupillary dilation (mydriasis) during the procedure.

Question 63: 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?

A. Posterior subcapsular cataract
B. Nuclear sclerosis (Correct Answer)
C. Zonular cataract
D. Anterior subcapsular cataract

Explanation: **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.

Question 64: What is the major function of Major Intrinsic Protein 26 (MIP-26)?

A. Glucose transport in the lens
B. Transport of water in the lens (Correct Answer)
C. Diffusion barrier
D. Capsule of the lens

Explanation: **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.

Question 65: In a pseudophakic eye, which of the following rays penetrate up to the retina?

A. UV-A (Correct Answer)
B. UV-B
C. UV-C
D. Infrared

Explanation: **Explanation:** The human crystalline lens acts as a natural filter, protecting the retina by absorbing most ultraviolet (UV) radiation. When the lens is removed (aphakia) or replaced with a standard intraocular lens (pseudophakia), this protective barrier is altered. **1. Why UV-A is the correct answer:** The natural lens primarily absorbs UV radiation in the **300–400 nm range (UV-A)**. In a pseudophakic eye, unless the prosthetic IOL is specifically manufactured with high-efficiency UV-blocking chromophores, UV-A rays (315–400 nm) have the highest penetration capability to reach the retina. This exposure is clinically significant as it increases the risk of phototoxicity and age-related macular degeneration (AMD). **2. Why the other options are incorrect:** * **UV-B (280–315 nm):** These rays are mostly absorbed by the **cornea** and the anterior segment. While some reach the lens, they are less likely to reach the retina in significant amounts compared to UV-A. * **UV-C (100–280 nm):** These are the shortest and most harmful waves, but they are almost entirely filtered out by the **Earth’s ozone layer** and do not reach the eye in significant quantities under normal conditions. * **Infrared (IR):** While IR rays can penetrate the eye, they are generally associated with thermal damage (e.g., Glassblower’s cataract) rather than the specific penetrative risk profile discussed in the context of standard pseudophakic retinal protection. **Clinical Pearls for NEET-PG:** * **Aphakic Glasses:** Traditionally required a UV filter because the retina is completely unprotected from UV-A. * **Blue-Light Filtering IOLs:** Modern "yellow-tinted" IOLs are designed to mimic the natural aging lens by filtering both UV and high-energy blue light to prevent macular damage. * **Corneal Absorption:** The cornea absorbs most wavelengths shorter than **295 nm**. * **Lens Absorption:** The natural crystalline lens absorbs wavelengths between **300–400 nm**.

Question 66: The cataract seen in patients with CTG/CUG trinucleotide repeats is?

A. Snow flake cataract
B. True exfoliation cataract
C. Christmas tree cataract (Correct Answer)
D. None of the above

Explanation: ### 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.

Question 67: Soemmering's ring is seen in which of the following conditions?

A. Posterior subcapsular cataract
B. After cataract (Correct Answer)
C. Endophthalmitis
D. Fuchs heterochromia iridis

Explanation: **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.

Question 68: After cataract surgery, when are glasses typically prescribed?

A. Two weeks
B. Six weeks (Correct Answer)
C. Twelve weeks
D. Twenty weeks

Explanation: **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.

Question 69: Which condition is typically associated with bilateral inferior subluxation of the lens?

A. Marfan's syndrome
B. Homocystinuria (Correct Answer)
C. Hyperinsulinemia
D. Ocular trauma

Explanation: **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 70: Which of the following is NOT a treatment for pediatric cataract?

A. Phaco-aspiration
B. Corneo-scleral tunnel technique
C. Intraocular lens implantation
D. Intracapsular cataract extraction (Correct Answer)

Explanation: **Explanation:** The management of pediatric cataract differs significantly from adult cataract surgery due to the unique anatomy of the child’s eye (smaller size, increased elasticity, and higher inflammatory response). **Why Intracapsular Cataract Extraction (ICCE) is NOT used:** ICCE involves removing the entire lens along with its capsule. In children, the **Zinn’s zonules** (which hold the lens) are extremely strong, and there is a firm **hyaloid-capsular adhesion** (Wieger’s ligament). Attempting ICCE in a child would lead to severe vitreous loss, retinal detachment, and significant trauma to the ocular structures. Therefore, it is absolutely contraindicated in pediatric cases. **Analysis of other options:** * **Phaco-aspiration:** This is the **gold standard** for pediatric cataract. Since the pediatric lens is soft and lacks a hard nucleus, it can be easily aspirated using a phacoemulsification probe or a vitrectomy cutter without the need for high ultrasonic energy. * **Corneo-scleral tunnel technique:** This refers to the surgical approach/incision site. In children, a scleral tunnel is often preferred over a clear corneal incision to ensure a more watertight seal and reduce the risk of endophthalmitis. * **Intraocular lens (IOL) implantation:** While controversial in infants under 6 months, IOL implantation is a standard treatment for older children to correct aphakia and prevent amblyopia. **Clinical Pearls for NEET-PG:** * **Primary Posterior Capsulotomy (PPC) + Anterior Vitrectomy:** These are mandatory steps in pediatric surgery (usually <6 years) to prevent **Posterior Capsule Opacification (PCO)**, which occurs almost 100% of the time in children if the capsule is left intact. * **Choice of IOL:** Heparin-coated PMMA or hydrophobic acrylic lenses are preferred to minimize postoperative inflammation. * **Visual Rehabilitation:** The most critical postoperative goal is preventing **amblyopia** through timely surgery and refractive correction.

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