Contact Lens Practice Questions

Q: In complicated cataract, in which part of the lens does opacity develop?

Posterior subcapsular. **Explanation:** **Complicated cataract** refers to the development of lens opacification secondary to intraocular inflammatory or degenerative diseases (e.g., chronic anterior uveitis, high myopia, or retinitis pigmentosa). **Why Posterior Subcapsular (PSC) is correct:** The lens is most metabolically vulnerable at its posterior pole. Unlike the anterior surface, the posterior part of the lens lacks an epithelial lining. In diseased states, inflammatory mediators and toxins from the uvea or vitreous diffuse through the thin posterior capsule. This disturbs the osmotic balance and metabolism of the lens fibers, leading to the formation of "polychromatic luster" (a breadcrumb-like appearance) specifically in the **posterior subcapsular** region. **Why other options are incorrect:** * **Anterior capsule:** Opacities here are typically associated with trauma, specific toxins (e.g., chlorpromazine), or "Glaukomflecken" following acute angle-closure glaucoma. * **Nucleus:** Nuclear sclerosis is primarily an age-related (senile) change caused by the compaction of central lens fibers. * **Cortical:** Cortical cataracts (cuneiform) are usually senile or metabolic (e.g., Diabetes Mellitus) in origin, characterized by hydration of lens fibers. **High-Yield Clinical Pearls for NEET-PG:** * **Polychromatic Luster:** The earliest sign of a complicated cataract is an iridescent play of colors (rainbow-like) at the posterior pole. * **Breadcrumb Appearance:** As the opacity progresses, it looks like chalky white breadcrumbs. * **Commonest Cause:** Chronic anterior uveitis is the most frequent cause of complicated cataract. * **Visual Impact:** PSC cataracts cause significant glare and vision loss, especially in bright light (due to miosis), compared to other types.

Q: In aphakia, which Purkinje fibres are absent?

3 and 4. **Explanation:** The Purkinje-Sanson images are reflections produced by the different refractive surfaces of the eye. To understand why images 3 and 4 are absent in aphakia, we must look at the anatomical structures responsible for each reflection: 1. **Purkinje Image 1:** Formed by the anterior surface of the **cornea**. 2. **Purkinje Image 2:** Formed by the posterior surface of the **cornea**. 3. **Purkinje Image 3:** Formed by the anterior surface of the **crystalline lens**. 4. **Purkinje Image 4:** Formed by the posterior surface of the **crystalline lens**. **Aphakia** is defined as the clinical absence of the crystalline lens. Since images 3 and 4 are generated specifically by the surfaces of the lens, they cannot be formed if the lens is missing. Therefore, **Option D (3 and 4)** is the correct answer. **Analysis of Incorrect Options:** * **Options A, B, and C:** These are incorrect because they include images 1 or 2. Images 1 and 2 are corneal reflections; as long as the cornea is intact, these images will persist regardless of the status of the lens. **High-Yield Clinical Pearls for NEET-PG:** * **Image Characteristics:** Images 1, 2, and 3 are **erect** (formed by convex surfaces acting as mirrors). Image 4 is **inverted** (formed by the concave posterior lens surface). * **Brightness/Size:** Image 1 is the brightest. Image 3 is the largest. * **Pseudophakia:** In a patient with an Intraocular Lens (IOL), all four images are present, but they may appear sharper or have different intensities compared to a natural lens. * **Sanson’s Test:** This clinical test uses these reflections to diagnose the presence of a lens or the type of cataract. In a mature cataract, image 4 is typically lost because light cannot penetrate to the posterior surface.

Q: In homocystinuria, in which direction does the lens subluxate?

Inferonasal. **Explanation:** In **Homocystinuria**, an autosomal recessive metabolic disorder caused by a deficiency of cystathionine beta-synthase, the lens typically subluxates in an **inferonasal** direction. This occurs because of a systemic deficiency in cysteine, which is essential for the structural integrity of the **zonules**. The zonules in homocystinuria are characteristically brittle, disintegrated, and lack the normal tension required to hold the lens in place, leading to a downward and inward displacement. **Analysis of Options:** * **Inferonasal (Correct):** This is the classic presentation in Homocystinuria. A key clinical differentiator is that the zonules are completely broken or absent, and there is a high risk of the lens dislocating into the anterior chamber or vitreous. * **Superotemporal (Incorrect):** This is the characteristic direction of subluxation in **Marfan Syndrome**. In Marfan’s, the zonules are stretched but usually remain intact, pulling the lens upward and outward. * **Inferolateral/Superonasal (Incorrect):** These are not standard patterns for common systemic syndromes. Superonasal displacement is occasionally associated with **Weill-Marchesani syndrome** (though it is more commonly inferior). **High-Yield NEET-PG Pearls:** * **Mnemonic:** "Marfan is **UP** (Superotemporal) and Homocystinuria is **DOWN** (Inferonasal)." * **Zonular Status:** In Marfan’s, zonules are *stretched*; in Homocystinuria, zonules are *shredded/absent*. * **Secondary Glaucoma:** Homocystinuria has a higher risk of pupillary block glaucoma due to the lens dislocating into the anterior chamber. * **Systemic Association:** Patients with Homocystinuria also present with intellectual disability, skeletal abnormalities (marfanoid habitus), and a high risk of **thromboembolism**.

Q: What are the essential parameters for intraocular lens (IOL) power calculation?

Keratometry and axial length of the eyeball. To calculate the power of an Intraocular Lens (IOL) required to achieve emmetropia after cataract surgery, we primarily rely on the **SRK (Sanders-Retzlaff-Kraff) formula**: **$P = A - 0.9K - 2.5L$** ### Why Option A is Correct The two most critical variables in determining the refractive state of the eye are: 1. **Keratometry (K):** This measures the corneal curvature (refractive power of the cornea). Since the cornea provides approximately two-thirds of the eye's total refractive power, its measurement is vital. 2. **Axial Length (L):** This is the distance from the anterior surface of the cornea to the fovea, measured via A-scan ultrasonography or optical biometry. Even a 1 mm error in axial length measurement can lead to a ~2.5 Diopter refractive error. ### Why Other Options are Incorrect * **Corneal Thickness (Options B, C, & D):** While central corneal thickness (CCT) is crucial for glaucoma screening and refractive surgeries like LASIK, it is **not** a standard parameter for routine IOL power calculation. * **Anterior Chamber Depth (Option D):** While ACD is used in newer generation formulas (like Haigis) to predict the Effective Lens Position (ELP), it is secondary to Keratometry and Axial Length, which remain the "essential" baseline parameters. ### NEET-PG High-Yield Pearls * **SRK Formula:** $P = A - 0.9K - 2.5L$ (where $P$ is IOL power and $A$ is the specific lens constant). * **A-Constant:** It is a theoretical value specific to each IOL model and manufacturer; it depends on the lens material and design. * **Standard Biometry:** Ultrasound A-scan uses a velocity of **1550 m/s** for the lens and **1532 m/s** for aqueous/vitreous. * **Optical Biometry (e.g., IOL Master):** Uses partial coherence interferometry; it is more accurate as it is non-contact and measures to the fovea.

Q: In Marfan's syndrome, in which direction is lens dislocation most commonly seen?

Supero-temporally. **Explanation:** In **Marfan’s syndrome**, the most common ocular manifestation is **Ectopia Lentis** (displacement of the crystalline lens), occurring in approximately 50–80% of patients. The correct answer is **Supero-temporally** because, in Marfan’s, the zonular fibers are genetically weak but often remain intact in certain quadrants. The displacement typically occurs in the **upward and outward** direction due to the relative preservation of the inferior zonules, which pull the lens superiorly as the superior zonules fail. **Analysis of Options:** * **Option A (Upwards):** While the lens moves upward, "Supero-temporally" is the more specific and clinically accurate description required for NEET-PG. * **Option B (Downwards):** This is characteristic of **Homocystinuria**. In Homocystinuria, zonules are completely disintegrated (due to cysteine deficiency), and the lens typically dislocates **infero-nasally**. * **Option D (Nasally):** Isolated nasal dislocation is rare and not the classic presentation for any major systemic syndrome. **High-Yield Clinical Pearls for NEET-PG:** * **Marfan’s Syndrome:** Autosomal Dominant; FBN1 gene mutation (Fibrillin-1); lens is displaced **Supero-temporally**; zonules are stretched but intact. Accommodation is often preserved. * **Homocystinuria:** Autosomal Recessive; Cystathionine beta-synthase deficiency; lens is displaced **Infero-nasally**; zonules are absent/broken. High risk of secondary glaucoma and thromboembolism. * **Weill-Marchesani Syndrome:** Characterized by **Microspherophakia** (small, spherical lens) and downward/anterior dislocation. * **Trauma:** The most common overall cause of lens dislocation (usually in the direction opposite to the impact).

Q: What is the surgery of choice for congenital cataract?

Extracapsular cataract extraction (ECCE). **Explanation:** The management of congenital cataract focuses on providing a clear visual axis to prevent irreversible amblyopia. **Why ECCE is the Correct Answer:** **Extracapsular Cataract Extraction (ECCE)**, specifically via **Lens Aspiration**, is the gold standard. In children, the lens matter is soft and can be easily aspirated. Modern pediatric cataract surgery involves ECCE with **Primary Posterior Capsulotomy (PPC)** and **Anterior Vitrectomy**. This is crucial because, in children, the posterior capsule opacifies (PCO) almost 100% of the time if left intact. For children >2 years of age, ECCE is combined with Posterior Chamber Intraocular Lens (PCIOL) implantation. **Analysis of Incorrect Options:** * **Intracapsular Cataract Extraction (ICCE):** This is **contraindicated** in children. The vitreous is strongly adherent to the posterior lens capsule (Wieger’s ligament). Removing the entire lens capsule would result in massive vitreous loss and high risk of retinal detachment. * **Needling:** An obsolete technique where a needle was used to puncture the capsule to allow aqueous to dissolve the lens. It often led to severe inflammation (phacoanaphylactic uveitis) and secondary glaucoma. * **Discission:** Similar to needling, it involves incising the anterior capsule. While it may be a component of surgery, it is not a complete procedure for cataract removal. **High-Yield Clinical Pearls for NEET-PG:** * **Timing:** Surgery should be done as early as possible (ideally before 6–8 weeks of age) to prevent stimulus-deprivation amblyopia. * **IOL Calculation:** In infants, the eye is under-corrected (hyperopic target) to account for the "myopic shift" as the eye grows. * **Most common cause:** Idiopathic (overall), but **Galactosemia** is a classic metabolic cause (Oil droplet cataract). * **Rubella:** Characterized by "Pearly white nuclear cataract."

Q: A 55-year-old male presents with vision of 6/12 in both eyes and complaints of glare at night, particularly while driving. What is the most likely diagnosis?

Opacification of the lens. **Explanation:** The correct answer is **Opacification of the lens (Cataract)**. **1. Why Opacification of the lens is correct:** The hallmark symptom described—**glare (photophobia) at night**, especially from oncoming headlights while driving—is a classic presentation of early cataracts, particularly **posterior subcapsular** or **cortical cataracts**. As the lens becomes opaque, it causes light rays to scatter (diffraction) instead of focusing sharply on the retina. This scattering manifests as glare and halos. A visual acuity of 6/12 in a 55-year-old further supports the diagnosis of age-related lens changes. **2. Why other options are incorrect:** * **Diabetic Retinopathy:** Typically presents with blurred vision, floaters, or sudden vision loss (vitreous hemorrhage). While it affects vision, "glare at night" is not its primary or pathognomonic symptom. * **Age-related Macular Degeneration (ARMD):** Patients usually complain of central vision loss, metamorphopsia (distortion of shapes), or a central scotoma. Peripheral vision and light scattering are generally not the initial complaints. * **Corneal Degeneration:** While some corneal pathologies (like Keratoconus or corneal edema) can cause glare, they are less common in a 55-year-old presenting with bilateral 6/12 vision compared to the high prevalence of cataracts in this age group. **Clinical Pearls for NEET-PG:** * **Cataract Types & Symptoms:** Nuclear cataracts often cause "second sight" (myopic shift), while Posterior Subcapsular Cataracts (PSC) cause significant glare and near-vision impairment. * **Glare Test:** The Brightness Acuity Tester (BAT) is used clinically to evaluate the impact of glare on a patient's functional vision. * **Differential for Glare:** Always consider Cataract, Corneal edema, and status post-refractive surgery (LASIK/PRK).

Q: UGH syndrome is commonly due to which type of intraocular lens implantation?

Anterior chamber intraocular lens (ACIOL). **Explanation:** **UGH Syndrome** (Uveitis-Glaucoma-Hyphema) is a classic complication caused by mechanical irritation of ocular structures by an intraocular lens (IOL). **1. Why ACIOL is the Correct Answer:** UGH syndrome is most commonly associated with **Anterior Chamber IOLs (ACIOLs)**, particularly older, rigid, or poorly finished closed-loop designs. Because these lenses are placed in the anterior chamber angle, the haptics or the optic can rub against the **vascular iris** or the **ciliary body**. This chronic friction leads to: * **Uveitis:** Breakdown of the blood-aqueous barrier. * **Glaucoma:** Pigment dispersion or inflammatory debris clogging the trabecular meshwork. * **Hyphema:** Mechanical erosion of iris vessels causing bleeding. **2. Analysis of Incorrect Options:** * **B. Posterior Chamber IOL (PCIOL):** These are placed in the capsular bag, away from vascular uveal tissue. While UGH can occur if a PCIOL is "sulcus-fixated" and rubs the posterior iris, it is statistically much less common than with ACIOLs. * **C. Several fixed IOLs:** This is not a standard terminology for a specific lens type associated with this syndrome. * **D. Piggyback IOL:** This involves placing two IOLs in one eye (usually to correct refractive surprises). While interlenticular opacification is a risk, UGH is not its primary association. **3. High-Yield Clinical Pearls for NEET-PG:** * **Clinical Presentation:** Blurred vision, "white-out" (due to hyphema), and increased intraocular pressure (IOP) following cataract surgery. * **Management:** Initial treatment is medical (steroids and IOP-lowering drugs), but the **definitive treatment** is often IOL explantation or exchange. * **Modern Context:** With the advent of modern, flexible, open-loop ACIOLs, the incidence of UGH has significantly decreased, but it remains a classic exam favorite.

Question 1

Mittendorf dots may be associated with which of the following conditions?

Accepted Answer

Congenital rubella syndrome

Answer

Posterior uveitis

Answer

Retinal detachment

Answer

Diabetic retinopathy

Question 2

Nuclear cataract can cause which refractive error?

Accepted Answer

Myopia

Answer

Hyperopia

Answer

Presbyopia

Answer

Astigmatism

Question 3

In complicated cataract, in which part of the lens does opacity develop?

Accepted Answer

Posterior subcapsular

Answer

Anterior capsule

Answer

Nucleus

Answer

Cortical

Question 4

In aphakia, which Purkinje fibres are absent?

Accepted Answer

3 and 4

Answer

1 and 3

Answer

2 and 4

Answer

2 and 3

Question 5

In homocystinuria, in which direction does the lens subluxate?

Accepted Answer

Inferonasal

Answer

Inferolateral

Answer

Superionasal

Answer

Superiotemporal

Question 6

What are the essential parameters for intraocular lens (IOL) power calculation?

Accepted Answer

Keratometry and axial length of the eyeball

Answer

Keratometry and corneal thickness

Answer

Corneal thickness and axial length of the eyeball

Answer

Corneal thickness and anterior chamber depth

Question 7

In Marfan's syndrome, in which direction is lens dislocation most commonly seen?

Accepted Answer

Supero-temporally

Answer

Upwards

Answer

Downwards

Answer

Nasally

Question 8

What is the surgery of choice for congenital cataract?

Accepted Answer

Extracapsular cataract extraction (ECCE)

Answer

Intracapsular cataract extraction (ICCE)

Answer

Needling

Answer

Discission

Question 9

A 55-year-old male presents with vision of 6/12 in both eyes and complaints of glare at night, particularly while driving. What is the most likely diagnosis?

Accepted Answer

Opacification of the lens

Answer

Diabetic retinopathy

Answer

Age-related macular degeneration

Answer

Corneal degeneration

Question 10

UGH syndrome is commonly due to which type of intraocular lens implantation?

Accepted Answer

Anterior chamber intraocular lens (ACIOL)

Answer

Posterior chamber intraocular lens (PCIOL)

Answer

Several fixed intraocular lenses

Answer

Piggyback intraocular lens

Contact Lens — MCQs

Contact Lens — MCQs

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