Contact Lens — MCQs

Contact Lens Indian Medical PG Practice Questions and MCQs

Question 81: Which of the following does not cause lens dislocation?

A. Ehlers-Danlos syndrome
B. Marfan's syndrome
C. Sulphite oxidase deficiency
D. Diabetes mellitus (Correct Answer)

Explanation: **Explanation:** The correct answer is **Diabetes mellitus**. Lens dislocation (Ectopia Lentis) occurs due to the disruption or weakness of the **ciliary zonules** (Zinn’s zonules) that hold the lens in place. While Diabetes mellitus causes various ocular complications like cataracts and retinopathy, it does not affect the structural integrity of the zonules enough to cause lens displacement. **Analysis of Options:** * **Marfan’s Syndrome (Option B):** The most common genetic cause of ectopia lentis. It typically causes **superotemporal** (upward and outward) dislocation due to a mutation in the Fibrillin-1 gene. * **Ehlers-Danlos Syndrome (Option A):** A connective tissue disorder characterized by collagen deficiency. This weakness extends to the zonular fibers, leading to lens subluxation. * **Sulphite Oxidase Deficiency (Option C):** A rare metabolic disorder that, along with **Homocystinuria**, is a classic cause of lens dislocation. In Homocystinuria, the dislocation is typically **inferonasal** (downward and inward). **High-Yield Clinical Pearls for NEET-PG:** * **Trauma:** The #1 overall cause of lens dislocation. * **Homocystinuria vs. Marfan’s:** Remember the direction! Marfan’s = **Up** (M-U); Homocystinuria = **Down** (H-D). * **Other causes:** Weill-Marchesani syndrome (associated with microspherophakia), Aniridia, and Buphthalmos (due to stretching of zonules). * **Iridodonesis:** A clinical sign of lens dislocation where the iris trembles due to lack of posterior support from the lens.

Question 82: Elschnig pearls are seen in which of the following conditions?

A. Wilson's disease
B. Secondary cataract (Correct Answer)
C. Complicated cataract
D. Congenital cataract

Explanation: **Explanation:** **Elschnig pearls** are the most common clinical manifestation of **Secondary Cataract**, also known as **Posterior Capsular Opacification (PCO)**. 1. **Why Secondary Cataract is correct:** After extracapsular cataract extraction (ECCE) or Phacoemulsification, some residual lens epithelial cells (LECs) may remain in the equatorial region of the capsular bag. These cells undergo proliferation and migration across the posterior capsule. When these cells undergo **hydropic degeneration** and swell into large, globular, translucent structures, they are termed **Elschnig pearls**. On slit-lamp examination, they resemble a "cluster of grapes" or "fish eggs." 2. **Why other options are incorrect:** * **Wilson’s Disease:** Characterized by the **Kayser-Fleischer (KF) ring** (copper deposition in Descemet's membrane) and **Sunflower cataract** (anterior subcapsular copper deposition). * **Complicated Cataract:** Occurs secondary to intraocular inflammation (e.g., Uveitis). It typically presents with a characteristic **"Breadcrumb appearance"** and **polychromatic luster** (iridescence) at the posterior pole. * **Congenital Cataract:** These are present at birth and have various morphologies (e.g., Zonular, Blue dot, or Total), but Elschnig pearls are a postoperative complication, not a primary congenital finding. **High-Yield Clinical Pearls for NEET-PG:** * **Soemmering’s Ring:** Another form of PCO where lens fibers are trapped between the two layers of the capsule, forming a ring-like structure. * **Treatment of PCO:** The gold standard treatment is **Nd:YAG Laser Capsulotomy**. * **Most common complication of Cataract Surgery:** Posterior Capsular Opacification (PCO). * **Prevention:** Use of square-edge Intraocular Lenses (IOLs) significantly reduces the incidence of Elschnig pearls by creating a physical barrier to cell migration.

Question 83: The 'second sight' phenomenon is most commonly observed in which of the following conditions?

A. Nuclear cataract (Correct Answer)
B. Cortical cataract
C. Senile cataract
D. Iridocyclitis

Explanation: **Explanation:** The correct answer is **Nuclear cataract (Option A)**. **Why Nuclear Cataract is Correct:** The phenomenon of 'second sight' (also known as **myopic shift**) occurs due to the progressive hardening and increased density of the lens nucleus, a process called **nuclear sclerosis**. As the refractive index of the lens increases, the eye becomes more **myopic** (nearsighted). This shift compensates for pre-existing age-related presbyopia, allowing elderly patients to suddenly read without their near glasses again. While it feels like an improvement, it is a temporary stage before the cataract matures and significantly blurs vision. **Why Other Options are Incorrect:** * **B. Cortical cataract:** These involve the hydration of lens fibers (cuneiform opacities). They typically cause glare and blurred vision but do not significantly increase the refractive index of the nucleus to cause a myopic shift. * **C. Senile cataract:** This is a broad category that includes both nuclear and cortical types. Since "Nuclear cataract" is a specific subtype listed, it is the more precise and correct answer. * **D. Iridocyclitis:** This is an inflammation of the iris and ciliary body. It typically presents with pain, redness, and photophobia, and may cause a transient shift in refraction due to ciliary spasm, but it is not associated with the "second sight" phenomenon. **High-Yield Clinical Pearls for NEET-PG:** * **Index Myopia:** The underlying mechanism of second sight in nuclear cataracts. * **Grading:** Nuclear cataracts are graded based on color (e.g., *Cataracta Brunescens* is brown, *Cataracta Nigra* is black). * **Visual Complaint:** Patients with nuclear cataracts often complain of poor distance vision but improved near vision. * **Contrast:** In contrast, **Posterior Subcapsular Cataracts (PSC)** cause significant glare and difficulty reading (near vision is worse than distance vision).

Question 84: True regarding exfoliation of lens occurs in:

A. Glass furnace workers
B. Glass blowers
C. Infrared exposures
D. All of the above (Correct Answer)

Explanation: **Explanation:** The correct answer is **D. All of the above**. This question tests the understanding of **True Exfoliation of the Lens**, a condition distinct from Pseudoexfoliation syndrome. **Underlying Medical Concept:** True exfoliation is a rare condition characterized by the lamellar splitting of the lens capsule. It is primarily caused by chronic exposure to **Infrared (IR) radiation** (thermal energy). When the iris absorbs infrared rays, it converts them into heat, which is then transferred to the underlying lens capsule. This chronic thermal stress causes the superficial layers of the anterior capsule to peel off in thin, translucent sheets, often described as "scrolls." **Analysis of Options:** * **A & B (Glass furnace workers and Glass blowers):** These occupations involve long-term exposure to intense heat and infrared radiation from molten glass. Historically, this led to the term **"Glass-blower’s cataract."** Similar risks are seen in steelworkers and blacksmiths. * **C (Infrared exposures):** This is the direct physical cause of the pathology. IR radiation (wavelengths 700–1400 nm) is specifically responsible for the thermal damage to the lens zonules and capsule. **High-Yield Clinical Pearls for NEET-PG:** * **True Exfoliation vs. Pseudoexfoliation:** True exfoliation is due to heat/IR (lamellar splitting), whereas Pseudoexfoliation (PEX) is a systemic deposition of fibrillar material (basement membrane disorder) associated with glaucoma. * **Appearance:** In true exfoliation, the "split" capsule may float in the anterior chamber like a "coiled-up membrane." * **Cataract Type:** Infrared exposure typically leads to a **posterior subcapsular cataract** or a discoid opacity in the lens. * **Prevention:** The use of IR-protective goggles (green-tinted or cobalt blue) is the primary preventive measure for industrial workers.

Question 85: Polychromatic luster is seen in which type of cataract?

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

Explanation: **Explanation:** **Posterior Subscapular Cataract (PSC)** is the correct answer. The characteristic **"polychromatic luster"** (an iridescent, rainbow-like play of colors) occurs due to the interference of light reflected from the irregular posterior surface of the lens and the opacified subscapular area. This luster is often described as having a "bread-crumb" appearance. PSC is typically associated with prolonged corticosteroid use, ionizing radiation, diabetes, and chronic intraocular inflammation (uveitis). **Analysis of Incorrect Options:** * **Zonular (Lamellar) Cataract:** This is a congenital cataract where opacification involves a specific "zone" or layer of the lens (usually surrounding a clear nucleus). It is characterized by "riders" (linear opacities) rather than a polychromatic luster. * **Nuclear Cataract:** This involves intensification of the normal age-related sclerosis of the lens nucleus. It is characterized by a yellow or brown discoloration (**brunescent cataract**) and causes a "second sight" phenomenon due to induced lenticular myopia. * **Anterior Subscapular Cataract:** These are usually caused by trauma or are secondary to acute angle-closure glaucoma (**Vogt’s Striae/Glaukomflecken**). They appear as small, white, necrotic spots but do not exhibit the iridescent luster seen in posterior lesions. **High-Yield Clinical Pearls for NEET-PG:** * **Cupuliform Cataract:** Another name for Posterior Subscapular Cataract. * **Visual Impact:** PSC affects near vision more than distance vision and causes significant glare (photophobia) in bright light due to pupillary constriction. * **Steroid Link:** PSC is the most common type of cataract induced by systemic or topical steroid therapy. * **Christmas Tree Cataract:** Associated with Myotonic Dystrophy (distinct from polychromatic luster).

Question 86: Posterior lenticonus is seen in which of the following conditions?

A. Alport syndrome
B. Lowe syndrome (Correct Answer)
C. Marfan syndrome
D. Homocystinuria

Explanation: **Explanation:** **Lowe Syndrome (Oculocerebrorenal Syndrome)** is the correct answer. It is an X-linked recessive disorder characterized by renal tubular dysfunction (Fanconi syndrome), mental retardation, and specific ocular findings. **Posterior lenticonus**—a cone-shaped protrusion of the posterior lens surface—is a hallmark feature of this condition. It often leads to the development of early-onset cataracts and glaucoma in these patients. **Analysis of Incorrect Options:** * **Alport Syndrome:** This is classically associated with **Anterior lenticonus**. It is a genetic disorder of Type IV collagen, presenting with sensorineural deafness and progressive nephritis. * **Marfan Syndrome:** The characteristic lens finding is **Ectopia lentis** (subluxation), typically occurring in an **upward and outward** (superotemporal) direction. * **Homocystinuria:** This also presents with **Ectopia lentis**, but the displacement is typically **downward and inward** (inferonasal). Patients also have a high risk of secondary glaucoma and thromboembolic events. **High-Yield Clinical Pearls for NEET-PG:** * **Lenticonus vs. Lentiglobus:** Lenticonus is a cone-shaped bulge; Lentiglobus is a hemispherical (spherical) bulge. * **Oil Droplet Appearance:** On distant direct ophthalmoscopy, lenticonus presents as a characteristic "oil droplet" reflex. * **Alport’s Mnemonic:** **A**lport = **A**nterior lenticonus. * **Lowe’s Mnemonic:** **P**osterior lenticonus is seen in **P**hakoantigenic uveitis and Lowe syndrome (though Lowe is the most common systemic association).

Question 87: What is the most common cause of keratitis in soft contact lens users?

A. Acanthamoeba (Correct Answer)
B. Staphylococcus aureus
C. Naegleria
D. Herpes simplex virus

Explanation: **Explanation:** The correct answer is **A. Acanthamoeba**. **Why Acanthamoeba is the correct answer:** Acanthamoeba is a free-living protozoan commonly found in soil and contaminated water (tap water, swimming pools, hot tubs). It is the most characteristic and feared cause of keratitis specifically associated with **soft contact lens wear**, particularly when patients use homemade saline solutions or practice poor lens hygiene (e.g., "topping off" solutions or swimming with lenses). While bacterial infections are numerically frequent, in the context of NEET-PG and standard ophthalmology textbooks (like Khurana), Acanthamoeba is highlighted as the classic organism linked to contact lens misuse. **Analysis of Incorrect Options:** * **B. Staphylococcus aureus:** While a common cause of bacterial keratitis generally, *Pseudomonas aeruginosa* is actually the most common bacterial pathogen specifically associated with contact lens wear. *S. aureus* is more common in non-lens-related corneal ulcers. * **C. Naegleria:** Though a free-living amoeba, *Naegleria fowleri* is primarily associated with Primary Amoebic Meningoencephalitis (PAM) and is not a standard cause of keratitis. * **D. Herpes simplex virus:** HSV is a leading cause of corneal blindness worldwide, but its etiology is viral reactivation in the trigeminal ganglion, not contact lens wear. **Clinical Pearls for NEET-PG:** * **Pathognomonic Sign:** **Radial Keratoneuritis** (infiltration along corneal nerves) is the hallmark of Acanthamoeba keratitis. * **Clinical Presentation:** Characterized by **"pain out of proportion to clinical findings"** and a classic **ring-shaped infiltrate** in later stages. * **Diagnosis:** Best diagnosed using **non-nutrient agar with E. coli overlay** or Confocal Microscopy. * **Treatment:** Medical management involves biguanides like **PHMB (Polyhexamethylene biguanide)** or **Chlorhexidine**, often combined with Propamidine isethionate (Brolene).

Question 88: What is the treatment of choice in unilateral aphakia?

A. Spectacles
B. Contact lens
C. Intraocular lens (Correct Answer)
D. Laser-assisted in situ keratomileusis

Explanation: **Explanation:** The primary challenge in managing **unilateral aphakia** is **aniseikonia** (difference in image size between the two eyes). To maintain binocular single vision, the image size difference must be minimized. **Why Intraocular Lens (IOL) is the Correct Choice:** The **Intraocular Lens (IOL)** is the treatment of choice because it is placed closest to the eye's nodal point. This results in the least amount of magnification (only **0–2%**), which is physiologically acceptable for the brain to fuse images from both eyes. It provides the best quality of vision, permanent correction, and eliminates the need for daily handling. **Analysis of Incorrect Options:** * **Spectacles (A):** In unilateral aphakia, spectacles produce a magnification of **25–30%**. This leads to significant aniseikonia and diplopia (double vision), making it impossible for the patient to use both eyes together. * **Contact Lens (B):** While contact lenses reduce magnification to about **7–10%** (which is tolerable), they are considered the **second-best** option. They are used only when an IOL is contraindicated due to poor manual dexterity, risk of infection, or ocular surface disease. * **LASIK (D):** Laser refractive surgery is generally not used to correct the high refractive error (usually +10D to +12D) seen in aphakia, as it exceeds the safe limits of corneal tissue ablation. **High-Yield Clinical Pearls for NEET-PG:** * **Magnification Comparison:** Spectacles (25-30%) > Contact Lenses (7-10%) > IOL (0-2%). * **Secondary IOL:** If an IOL was not placed during the initial surgery, a "Secondary IOL" (PCIOL, ACIOL, or Scleral Fixated IOL) is the preferred rehabilitative procedure. * **Epikeratophakia:** A historical surgical option where a donor corneal lenticule was sutured onto the host cornea; now largely obsolete due to IOLs.

Question 89: What is the typical incision size for standard sutureless cataract surgery performed with phacoemulsification and foldable intraocular lens implantation?

A. 1 mm to 1.5 mm
B. 2 mm to 2.5 mm
C. 3 mm to 3.5 mm (Correct Answer)
D. 3.5 mm to 4.5 mm

Explanation: **Explanation:** In modern cataract surgery, the goal is to achieve a self-sealing, astigmatically neutral incision. The standard incision size for **Phacoemulsification** with a foldable intraocular lens (IOL) typically ranges between **2.8 mm and 3.2 mm**, making **3 mm to 3.5 mm** the most accurate choice among the provided options. * **Why Option C is Correct:** A 3.2 mm clear corneal incision is the traditional "sweet spot." It is large enough to allow the phacoemulsification probe and the cartridge of a foldable IOL to enter the anterior chamber, yet small enough to remain **sutureless** due to the "valve effect" of the architectural construction. * **Why Options A & B are Incorrect:** While "Micro-incision Cataract Surgery" (MICS) uses incisions below 2.2 mm (Option B) or even 1.8 mm, these require specialized sub-2mm phaco tips and ultra-thin IOLs. They are not considered the "standard" size for routine phacoemulsification. Option A (1–1.5 mm) is typically reserved for side-port (paracentesis) incisions, not the main entry. * **Why Option D is Incorrect:** Incisions larger than 3.5 mm (e.g., 5–6 mm) are characteristic of **Manual Small Incision Cataract Surgery (SICS)** or ECCE. These larger incisions often require sutures or result in significant surgically induced astigmatism. **High-Yield Clinical Pearls for NEET-PG:** * **SICS Incision:** 5.5 mm to 7 mm (V-shaped or frown incision). * **ECCE Incision:** 10 mm to 12 mm (requires multiple sutures). * **Astigmatism:** Larger incisions cause more "flattening" along the meridian of the incision. * **Foldable IOL Materials:** Usually made of Silicone or Hydrophobic/Hydrophilic Acrylic to fit through <3.2 mm incisions.

Question 90: Epithelium is absent in the lens in which of the following locations?

A. Anterior surface
B. Anterior pole
C. Posterior surface (Correct Answer)
D. Zonular attachment

Explanation: ### Explanation The crystalline lens is a unique, avascular structure enclosed within a basement membrane known as the **lens capsule**. The distribution of the lens epithelium is a high-yield anatomical fact essential for understanding lens growth and cataract formation. **1. Why the Correct Answer (C) is Right:** During embryonic development, the posterior epithelial cells are used up to form the **primary lens fibers**, which fill the cavity of the lens vesicle (the embryonic nucleus). Consequently, in the mature lens, the **subcapsular epithelium is entirely absent on the posterior surface**. The lens consists only of the capsule and the lens fibers posteriorly. **2. Analysis of Incorrect Options:** * **Anterior Surface & Anterior Pole (A & B):** A single layer of cuboidal epithelial cells (the **anterior epithelium**) is present deep to the anterior capsule. These cells are metabolically active and responsible for the life-long growth of the lens. * **Zonular Attachment (D):** The zonules of Zinn attach to the lens capsule in the pre-equatorial and post-equatorial regions. The epithelium is present in the equatorial region (the "germinal zone"), where cells actively divide and differentiate into new lens fibers. **3. Clinical Pearls for NEET-PG:** * **Germinal Zone:** Located at the lens **equator**, this is the site of maximum mitotic activity. * **Lens Growth:** The lens is the only structure in the body that continues to grow throughout life, as new fibers are constantly added at the periphery. * **Posterior Subcapsular Cataract (PSC):** Although the posterior epithelium is absent, PSC occurs when epithelial cells from the equator migrate abnormally toward the posterior pole, causing opacification. * **Metabolism:** The anterior epithelium contains the highest concentration of **Na+/K+-ATPase pumps**, which are vital for maintaining lens dehydration and transparency.

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Contact Lens Materials

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Specialty Contact Lenses

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Contact Lens Care and Maintenance

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Contact Lens Complications

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Contact Lenses for Keratoconus

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Orthokeratology

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Contact Lenses for Astigmatism

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Contact Lenses for Presbyopia

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Scleral Contact Lenses

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