RRB 2025 PYQ previous year questions explanation

Below is a detailed explanation of the first 20 multiple-choice questions (MCQs), Each explanation includes the correct answer, reasoning, and relevant background information to clarify the concepts.

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Q31. What is the primary effect of a concave lens on light that passes through it in terms of refraction through spherical surfaces?

Options:

• 1. It causes light rays to diverge away from the optical axis.
• 2. It focuses light rays to the retina.
• 3. It bends light rays parallel to the optical axis.
• 4. It causes light rays to converge at a single point.

Correct Answer: 1. It causes light rays to diverge away from the optical axis.

Explanation:

A concave lens is a diverging lens, meaning it spreads out light rays that pass through it. When parallel light rays (e.g., from a distant object) enter a concave lens, they are refracted in such a way that they appear to diverge from a virtual focal point on the same side as the incident light. This divergence occurs because the lens is thinner at the center than at the edges, causing the light rays to bend outward, away from the optical axis. 

• Option 2:  is incorrect because focusing light rays to the retina is a function of the eye’s natural lens or a convex lens, not a concave lens.
• Option 3: is misleading; while a concave lens bends light rays, it does not make them parallel to the optical axis—it causes divergence.
• Option 4: describes a convex (converging) lens, which focuses light rays to a single point (real focus), not a concave lens.

Relevance for Optometry: Concave lenses are used to correct myopia (nearsightedness), where the eye focuses light in front of the retina. The diverging effect of the concave lens helps shift the focus back to the retina.

Q32. Which of the following are the correct base pairs in DNA?

Options:

• 1. Adenine-Cytosine and Guanine-Thymine
• 2. Adenine-Thymine and Guanine-Cytosine
• 3. Adenine-Guanine and Thymine-Cytosine
• 4. Adenine-Uracil and Guanine-Cytosine

Correct Answer: 2. Adenine-Thymine and Guanine-Cytosine

Explanation:

In DNA (deoxyribonucleic acid), the nitrogenous bases form specific complementary pairs through hydrogen bonding:

- Adenine (A) pairs with Thymine (T) via two hydrogen bonds.

- Guanine (G) pairs with Cytosine (C) via three hydrogen bonds.

This base-pairing rule is fundamental to DNA’s double-helix structure and its replication process.

• Option 1: is incorrect because Adenine does not pair with Cytosine, and Guanine does not pair with Thymine.
• Option 3: is incorrect because Adenine and Guanine are both purines and do not pair with each other, nor do Thymine and Cytosine (both pyrimidines).
• Option 4: is incorrect because Uracil is found in RNA, not DNA. In RNA, Adenine pairs with Uracil, but in DNA, Adenine pairs with Thymine.

Relevance for Optometry: Understanding DNA base pairing is relevant in genetic eye disorders (e.g., retinitis pigmentosa), where mutations in DNA sequences can lead to vision impairment.

Q33. Which of the following is a common symptom of tuberculosis (TB)?

Options:

• 1. Night sweats and chills
• 2. Persistent cough and fatigue
• 3. Shortness of breath
• 4. Swollen joints

Correct Answer: 2. Persistent cough and fatigue

Explanation:

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis, primarily affecting the lungs (pulmonary TB). A hallmark symptom is a persistent cough lasting more than three weeks, often accompanied by fatigue, weight loss, and sometimes hemoptysis (coughing up blood). Fatigue is a systemic symptom due to the body’s immune response to the infection.

• Option 1: Night sweats and chills are associated with TB, especially in advanced or disseminated cases, but they are less specific and not as universally present as a persistent cough.
• Option 3: Shortness of breath may occur in severe TB with extensive lung damage, but it is not a primary or common early symptom.
• Option 4: Swollen joints are more characteristic of conditions like rheumatoid arthritis or septic arthritis, not TB (though TB can rarely cause joint involvement in extrapulmonary forms).

Relevance for Optometry: TB can affect the eye (ocular TB), causing uveitis or choroiditis. Recognizing systemic symptoms like persistent cough aids in suspecting TB-related ocular manifestations.

Q34. What does the Hirschberg test primarily assess?

Options:

• 1. Refractive error
• 2. Intraocular pressure
• 3. Visual acuity
• 4. Ocular alignment

Correct Answer: 4. Ocular alignment

Explanation:

The Hirschberg test is a simple, non-invasive clinical test used to assess ocular alignment, specifically to detect strabismus (misalignment of the eyes, e.g., esotropia or exotropia). It involves shining a light into the patient’s eyes and observing the reflection (corneal light reflex) on the cornea. If the reflections are symmetric and centered, the eyes are aligned. Asymmetry indicates a deviation of one or both eyes.

• Option 1: Refractive error (e.g., myopia, hyperopia) is assessed using refraction techniques like retinoscopy or subjective refraction, not the Hirschberg test.
• Option 2: Intraocular pressure is measured with tonometry, not the Hirschberg test.
• Option 3: Visual acuity is tested using charts like the Snellen chart, not the Hirschberg test.

Relevance for Optometry: The Hirschberg test is a quick screening tool in pediatric and adult eye exams to identify strabismus, which can lead to amblyopia (lazy eye) if untreated.

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Q35. Which of the following statements about the refractive index of spectacle lens material is correct?

Options:

• 1. A lower refractive index means the lens will be thinner for the same prescription.
• 2. High-index lenses are always heavier than standard plastic lenses.
• 3. A higher refractive index bends light more efficiently, allowing the lens to be thinner.
• 4. The refractive index has no effect on the thickness of the lens.

Correct Answer: 3. A higher refractive index bends light more efficiently, allowing the lens to be thinner.

Explanation:

The refractive index (n) of a lens material determines how much it bends light. A higher refractive index means the material bends light more efficiently, requiring less curvature and thickness to achieve the same refractive power (measured in diopters). High-index lenses are thus thinner and lighter for high prescriptions (e.g., strong myopia or hyperopia), improving comfort and aesthetics.

• Option 1: Incorrect. A lower refractive index requires a thicker lens to achieve the same power, as it bends light less efficiently.
• Option 2: Incorrect. High-index lenses are generally lighter than standard plastic lenses (e.g., CR-39, n ≈ 1.5) because they are thinner, despite sometimes being denser materials.
• Option 4: Incorrect. The refractive index directly affects lens thickness; higher-index materials reduce thickness.

Relevance for Optometry: Optometrists recommend high-index lenses for patients with high prescriptions to reduce lens thickness, improving cosmetic appearance and comfort.

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Q36. Which of the following statements is true about convergence insufficiency?

Options:

• 1. It is not related to binocular vision.
• 2. A symptom is the inability to turn the eyes outward.
• 3. It involves reduced ability of the eyes to turn inward while focusing on a near object.
• 4. It is caused by excessive accommodation.

Correct Answer: 3. It involves reduced ability of the eyes to turn inward while focusing on a near object.

Explanation:

Convergence insufficiency (CI) is a binocular vision disorder where the eyes have difficulty turning inward (converging) to focus on a near object, such as during reading. This leads to symptoms like eye strain, double vision (diplopia), headaches, and difficulty concentrating on near tasks. CI is often diagnosed using tests like near point of convergence (NPC).

• Option 1: Incorrect. CI is directly related to binocular vision, as it affects the coordinated movement of both eyes.
• Option 2: Incorrect. The issue in CI is difficulty turning eyes inward (convergence), not outward (divergence).
• Option 4: Incorrect. CI is not caused by excessive accommodation (focusing effort of the lens); however, accommodation and convergence are linked, and CI may strain the accommodative system.

Relevance for Optometry: CI is a common condition treated with vision therapy, prism lenses, or exercises to improve convergence ability, especially in children and young adults.

Q37. A converging lens is also known as:

Options:

• 1. Convex lens
• 2. Plano-concave lens
• 3. Plano-convex lens
• 4. Concave lens

Correct Answer: 1. Convex lens

Explanation:

A converging lens focuses parallel light rays to a single point (real focus) after refraction. This is achieved by a convex lens, which is thicker at the center than at the edges, causing light rays to bend inward (converge). Both plano-convex (one flat side, one convex side) and biconvex (both sides convex) lenses are types of convex lenses, but the general term for a converging lens is “convex lens.”

• Option 2: Incorrect. A plano-concave lens is a diverging lens, as one side is concave, causing light to spread out.
• Option 3: Incorrect. While a plano-convex lens is a type of convex lens, the question asks for the general term, which is “convex lens.”
• Option 4: Incorrect. A concave lens is a diverging lens, not a converging one.

Relevance for Optometry: Convex lenses are used to correct hyperopia (farsightedness) and presbyopia, where the eye cannot focus light properly on the retina.

Q38. Which infection is caused by the varicella zoster virus?

Options:

• 1. Conjunctivitis
• 2. Herpes zoster ophthalmicus
• 3. Keratitis
• 4. Endophthalmitis

Correct Answer: 2. Herpes zoster ophthalmicus

Explanation:

The varicella zoster virus (VZV) causes chickenpox during primary infection and can remain dormant in nerve ganglia. Reactivation later in life leads to herpes zoster (shingles). When the ophthalmic division of the trigeminal nerve (CN V1) is involved, it causes herpes zoster ophthalmicus (HZO), characterized by a painful rash on the forehead, eyelid, or face, and potential ocular complications like conjunctivitis, keratitis, or uveitis.

• Option 1: Conjunctivitis can be caused by various pathogens (e.g., bacteria, other viruses), but not specifically VZV.
• Option 3: Keratitis (corneal inflammation) can be a complication of HZO, but it is not the primary infection caused by VZV.
• Option 4: Endophthalmitis is a severe intraocular infection, typically bacterial or fungal, not caused by VZV.

Relevance for Optometry: HZO is a serious condition requiring urgent antiviral treatment to prevent vision-threatening complications like corneal scarring or glaucoma.

Q39. Which of the following structures plays a primary role in the outflow of aqueous humor and is most commonly implicated in the pathophysiology of primary open-angle glaucoma?

Options:

• 1. Schlemm's canal
• 2. Zonules of Zinn
• 3. Iris root
• 4. Vitreous body

Correct Answer: 1. Schlemm's canal

Explanation:

Aqueous humor, produced by the ciliary body, flows from the posterior chamber through the pupil to the anterior chamber and drains primarily via the trabecular meshwork into Schlemm’s canal. In primary open-angle glaucoma (POAG), the most common form of glaucoma, resistance to aqueous outflow in the trabecular meshwork or Schlemm’s canal increases, elevating intraocular pressure (IOP) and damaging the optic nerve.

• Option 2: Zonules of Zinn are fibers that suspend the lens, not involved in aqueous outflow.
• Option 3: The iris root is part of the anterior chamber angle but not the primary outflow structure.
• Option 4: The vitreous body is a gel-like structure in the posterior segment, unrelated to aqueous humor dynamics.

Relevance for Optometry: Understanding aqueous outflow is critical for diagnosing and managing glaucoma, as treatments (e.g., medications, laser trabeculoplasty) target the trabecular meshwork or Schlemm’s canal to lower IOP.

Q40. Which of the following best describes an integrated approach to tackling avoidable blindness, and how is it different from traditional models in terms of sustainability and accessibility?

Options:

• 1. Focuses on expensive laser-based technology and urban tertiary care centers.
• 2. Performs cataract surgeries for elderly patients only in city hospitals.
• 3. Relies entirely on government funding and rural volunteers.
• 4. Combines community-based screening, cross-subsidized care, and high-volume surgical efficiency.

Correct Answer: 4. Combines community-based screening, cross-subsidized care, and high-volume surgical efficiency.

Explanation:

An integrated approach to tackling avoidable blindness (e.g., from cataracts, refractive errors, or glaucoma) emphasizes accessibility and sustainability. It involves:

Community-based screening: to identify cases in underserved areas.

Cross-subsidized care: where revenue from paying patients subsidizes free or low-cost care for the poor.

High-volume surgical efficiency: like that seen in models such as Aravind Eye Care System, to reduce costs and increase output.

This approach differs from traditional models, which often rely on centralized, expensive facilities with limited reach to rural populations, making them less sustainable and accessible.

• Option 1: Incorrect. Expensive laser technology and urban centers limit accessibility and are not sustainable for widespread blindness prevention.
• Option 2: Incorrect. Restricting surgeries to elderly patients in city hospitals excludes other causes of blindness and rural populations.
• Option 3: Incorrect. Sole reliance on government funding and volunteers is unsustainable due to inconsistent resources and scalability issues.

Relevance for Optometry: Integrated approaches are vital for public health optometry, ensuring equitable access to eye care in resource-limited settings.

Q41. During the inflammation process, which of the following is the primary response of ocular tissue?

Options:

• 1. Inhibition of immune cell activity
• 2. Decreased blood flow to the affected area
• 3. Vasodilation and increased vascular permeability
• 4. Complete healing without scarring

Correct Answer: 3. Vasodilation and increased vascular permeability

Explanation:

Inflammation in ocular tissues (e.g., conjunctivitis, uveitis) follows the general inflammatory response. The primary response includes:

Vasodilation: Blood vessels widen, increasing blood flow to the affected area, causing redness (e.g., conjunctival injection).

Increased vascular permeability: Blood vessel walls become leaky, allowing immune cells and plasma proteins to enter the tissue, leading to swelling (edema) and aiding in pathogen clearance.

• Option 1: Incorrect. Inflammation involves activation, not inhibition, of immune cells (e.g., neutrophils, macrophages).
• Option 2: Incorrect. Blood flow increases due to vasodilation, not decreases.
• Option 4: Incorrect. Healing without scarring is a potential outcome, not the primary response during active inflammation.

Relevance for Optometry: Recognizing signs of inflammation (redness, swelling) is crucial for diagnosing ocular conditions like uveitis or keratitis and guiding treatment (e.g., corticosteroids).

Q42. What is the main feature of bifocal lenses?

Options:

• 1. They have two different focal lengths
• 2. They are used only for reading
• 3. They are used for color correction
• 4. They are designed for single-vision use

Correct Answer: 1. They have two different focal lengths

Explanation:

Bifocal lenses have two distinct optical zones with different focal lengths (powers):

- The upper portion corrects for distance vision (e.g., for myopia or hyperopia).

- The lower portion, often a visible segment, corrects for near vision (e.g., for presbyopia).

This allows wearers to switch between distance and near tasks without changing glasses.

• Option 2: Incorrect. Bifocals are used for both distance and near vision, not only reading.
• Option 3: Incorrect. Bifocals correct refractive errors, not color vision deficiencies.
• Option 4: Incorrect. Single-vision lenses have one focal length, unlike bifocals.

Relevance for Optometry: Bifocals are commonly prescribed for presbyopia, an age-related condition where the eye loses near-focusing ability.

Q43. Which of the following cranial nerves is responsible for the movement of the lateral rectus muscle in the eye?

Options:

• 1. Oculomotor nerve (CN III)
• 2. Trochlear nerve (CN IV)
• 3. Abducens nerve (CN VI)
• 4. Trigeminal nerve (CN V)

Correct Answer: 3. Abducens nerve (CN VI)

Explanation:

The lateral rectus muscle abducts the eye (moves it outward). It is innervated by the abducens nerve (cranial nerve VI). The extraocular muscles are controlled by three cranial nerves:

- Oculomotor nerve (CN III): Innervates superior rectus, inferior rectus, medial rectus, inferior oblique, and levator palpebrae superioris.

- Trochlear nerve (CN IV): Innervates superior oblique.

- Abducens nerve (CN VI): Innervates lateral rectus.

• Option 1: Incorrect. CN III controls most eye muscles but not the lateral rectus.
• Option 2: Incorrect. CN IV controls the superior oblique, not the lateral rectus.
• Option 4: Incorrect. CN V (trigeminal) is sensory for the face and cornea, not motor for eye muscles.

Relevance for Optometry: Damage to CN VI can cause esotropia (inward eye deviation) and diplopia, which optometrists may detect during motility testing.

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Q44. What is the primary use of a fundus camera?

Options:

1. Measuring the cornea

2. Measuring intraocular pressure

3. Taking photographs of the retina

4. Checking lens clarity

Correct Answer: 3. Taking photographs of the retina

Explanation:

A fundus camera is a specialized imaging device used to capture detailed photographs of the retina, optic disc, macula, and blood vessels at the back of the eye (fundus). These images are critical for diagnosing and monitoring conditions like diabetic retinopathy, glaucoma, and macular degeneration.

• Option 1: Incorrect. Corneal measurements are done with keratometry or topography.
• Option 2: Incorrect. Intraocular pressure is measured with tonometry.
• Option 4: Incorrect. Lens clarity (e.g., for cataracts) is assessed with a slit lamp or ophthalmoscopy, not primarily a fundus camera.

Relevance for Optometry: Fundus photography is a routine tool for retinal screening and documentation in optometric practice.

Q45. Which of the following is considered a subjective method of refraction?

Options:

• 1. Retinoscopy
• 2. Autorefraction
• 3. Trial frame testing
• 4. Keratometry

Correct Answer: 3. Trial frame testing

Explanation:

Subjective refraction relies on the patient’s feedback to determine the optimal lens prescription. In trial frame testing, the optometrist places lenses of varying powers in a trial frame and asks the patient to compare clarity (e.g., “Which is better, lens 1 or lens 2?”) to refine the prescription.

• Option 1: Retinoscopy is an objective method, as it uses the reflection of light from the retina to estimate refractive error without patient input.
• Option 2: Autorefraction is an objective method, using automated instruments to measure refractive error.
• Option 4: Keratometry measures corneal curvature, not refractive error, and is objective.

Relevance for Optometry: Subjective refraction, like trial frame testing, is essential for finalizing prescriptions, especially for complex cases or when objective methods are less accurate.

Q46. What is the unit of measurement for the power of a lens?

Options:

• 1. Hertz
• 2. Meter
• 3. Diopter
• 4. Newton

Correct Answer: 3. Diopter

Explanation:

The power of a lens, which indicates its ability to converge or diverge light, is measured in diopters (D). The power (P) is defined as the reciprocal of the focal length (f, in meters):  

\[ P = \frac{1}{f} \]  

For example, a lens with a focal length of 0.5 meters has a power of \( \frac{1}{0.5} = 2 \, \text{D} \). Convex lenses have positive power, and concave lenses have negative power.

• Option 1: Hertz measures frequency (e.g., of light waves).
• Option 2: Meter measures length, not lens power.
• Option 4: Newton measures force, not optical power.

Relevance for Optometry: Diopters are used to prescribe corrective lenses for conditions like myopia (-D) or hyperopia (+D).

Q47. A patient reports difficulty seeing distant objects clearly but has no issues with reading. What is the likely refractive error?

Options:

• 1. Hyperopia
• 2. Presbyopia
• 3. Myopia
• 4. Astigmatism

Correct Answer: 3. Myopia

Explanation:

Myopia (nearsightedness) is a refractive error where the eye focuses light in front of the retina, causing distant objects to appear blurry while near objects are clear. This occurs due to an elongated eyeball or excessive corneal/lens curvature.

• Option 1: Hyperopia (farsightedness) causes difficulty with near vision, not distance vision.
• Option 2: Presbyopia is an age-related loss of near focusing ability, affecting reading, not distance vision.
• Option 4: Astigmatism causes blurred vision at all distances due to irregular corneal or lens curvature, but the question specifies only distance vision issues.

Relevance for Optometry: Myopia is corrected with concave (minus) lenses, and optometrists must accurately diagnose it to prescribe appropriate glasses or contact lenses.

Q48. Which layer of the eye contains blood vessels and provides oxygen and nutrients to the retina?

Options:

• 1. Cornea
• 2. Sclera
• 3. Iris
• 4. Choroid

Correct Answer: 4. Choroid

Explanation:

The choroid is a vascular layer of the eye located between the retina and the sclera. It contains a dense network of blood vessels that supply oxygen and nutrients to the outer retina (e.g., photoreceptors) and other ocular structures. The choroid also absorbs stray light to prevent reflections within the eye.

• Option 1: The cornea is avascular (lacking blood vessels) and transparent, relying on aqueous humor and tears for nutrients.
• Option 2: The sclera is the fibrous outer layer, providing structural support, not blood supply.
• Option 3: The iris controls pupil size and has some blood vessels but is not the primary supplier to the retina.

Relevance for Optometry: Choroidal abnormalities (e.g., in choroiditis or neovascularization) can affect retinal health, detectable during fundus examination.

Q49. What is the function of the macula in the eye?

Options:

1. Provides peripheral vision

2. Controls eye movement

3. Facilitates night vision

4. Enables sharp central vision

Correct Answer: 4. Enables sharp central vision

Explanation:

The macula is a small, central area of the retina rich in cone photoreceptors, responsible for high-acuity vision, color perception, and fine detail (e.g., reading, recognizing faces). The fovea, at the macula’s center, has the highest cone density, providing the sharpest vision.

• Option 1: Peripheral vision is mediated by the peripheral retina, rich in rod photoreceptors.
• Option 2: Eye movement is controlled by extraocular muscles, not the macula.
• Option 3: Night vision is facilitated by rods, which are sparse in the macula but abundant in the peripheral retina.

Relevance for Optometry: Macular disorders (e.g., macular degeneration) severely impair central vision, and optometrists use tests like Amsler grid to assess macular function.

Q50. Which vitamin deficiency is most commonly associated with night blindness?

Options:

• 1. Vitamin A
• 2. Vitamin B12
• 3. Vitamin C
• 4. Vitamin D

Correct Answer: 1. Vitamin A

Explanation:

Vitamin A is essential for producing rhodopsin, a pigment in rod photoreceptors that enables vision in low-light conditions. A deficiency in vitamin A impairs rod function, leading to night blindness (nyctalopia), where individuals struggle to see in dim light or at night. Severe deficiency can also cause xerophthalmia or keratomalacia, affecting the cornea.

• Option 2: Vitamin B12 deficiency causes neurological issues (e.g., optic neuropathy), not night blindness.
• Option 3: Vitamin C deficiency causes scurvy, affecting connective tissues, not vision directly.
• Option 4: Vitamin D deficiency is linked to bone health, not night blindness.

Relevance for Optometry: Night blindness due to vitamin A deficiency is a key diagnostic clue in regions with malnutrition, and optometrists may recommend supplementation or referral.

Q51. Which part of the eye is responsible for focusing light onto the retina?

Options:

• 1. Cornea
• 2. Iris
• 3. Lens
• 4. Pupil

Correct Answer: 3. Lens

Explanation:

The lens, located behind the iris, is a transparent, biconvex structure that fine-tunes the focus of light onto the retina by changing its shape (accommodation). The cornea also contributes significantly to focusing light (about 70% of the eye’s refractive power), but the lens adjusts focus for near and far objects.

• Option 1: The cornea refracts light but does not adjust focus dynamically like the lens.
• Option 2: The iris controls the pupil size to regulate light entry, not focusing.
• Option 4: The pupil is an aperture that controls light intensity, not a focusing structure.

Relevance for Optometry: The lens’s role in accommodation is critical for diagnosing refractive errors like presbyopia (age-related loss of lens flexibility) and prescribing corrective lenses.

Q52. What is the normal range of intraocular pressure (IOP) in mmHg?

Options:

• 1. 5-10
• 2. 10-21
• 3. 22-30
• 4. 30-40

Correct Answer: 2. 10-21

Explanation:

Intraocular pressure (IOP) is the pressure exerted by the aqueous humor within the eye, typically measured in millimeters of mercury (mmHg). The normal range for most individuals is 10-21 mmHg, with slight variations. Elevated IOP (>21 mmHg) is a hallmark of glaucoma, though not all cases of glaucoma have high IOP (e.g., normal-tension glaucoma).

• Option 1: 5-10 mmHg is too low and may indicate hypotony, which can cause retinal or choroidal issues.
• Option 3: 22-30 mmHg is elevated and suggestive of ocular hypertension or glaucoma.
• Option 4: 30-40 mmHg is significantly elevated and associated with advanced glaucoma or acute angle-closure glaucoma.

Relevance for Optometry: Optometrists measure IOP using tonometry to screen for glaucoma, a leading cause of irreversible blindness.

Q53. What condition is characterized by increased intraocular pressure causing optic nerve damage?

Options:

• 1. Cataract
• 2. Glaucoma
• 3. Macular degeneration
• 4. Retinal detachment

Correct Answer: 2. Glaucoma

Explanation:

Glaucoma is a group of eye diseases characterized by increased intraocular pressure (IOP) that damages the optic nerve, leading to progressive vision loss, particularly peripheral vision. Primary open-angle glaucoma (POAG) is the most common form, involving impaired aqueous humor outflow.

• Option 1: Cataract involves lens clouding, not IOP or optic nerve damage.
• Option 3: Macular degeneration affects central vision due to retinal damage, not IOP.
• Option 4: Retinal detachment involves the retina separating from underlying tissue, unrelated to IOP.

Relevance for Optometry: Early detection of glaucoma through IOP measurement, optic disc evaluation, and visual field testing is critical for preventing vision loss.

Q54. Which of the following is the most common cause of refractive error in the human eye?

Options:

• 1. Myopia
• 2. Cataract
• 3. Glaucoma
• 4. Presbyopia

Correct Answer: 1. Myopia

Explanation:

Myopia (nearsightedness) is the most common refractive error globally, particularly in younger populations and urban areas with high near-work demands (e.g., reading, screen time). It occurs when the eyeball is too long or the cornea/lens is too curved, causing light to focus in front of the retina.

• Option 2: Cataract causes vision blur due to lens opacity, not a refractive error in the optical sense.
• Option 3: Glaucoma affects IOP and optic nerve health, not refractive error.
• Option 4: Presbyopia is common in older adults due to loss of lens elasticity, but myopia is more prevalent across all age groups.

Relevance for Optometry: Myopia management, including corrective lenses, contact lenses, or orthokeratology, is a core part of optometric practice, especially with rising myopia prevalence.

Q55. What is the primary function of rods in the retina?

Options:

• 1. Color vision
• 2. Peripheral and night vision
• 3. Sharp central vision
• 4. Depth perception

Correct Answer:2. Peripheral and night vision

Explanation:

Rods are photoreceptor cells in the retina, concentrated in the peripheral regions, and are highly sensitive to low light levels. They enable night vision (scotopic vision) and contribute to peripheral vision but do not detect color or fine detail.

• Option 1: Color vision is mediated by cone photoreceptors, not rods.
• Option 3: Sharp central vision is provided by cones, particularly in the macula.
• Option 4: Depth perception involves binocular vision and brain processing, not a specific retinal cell function.

Relevance for Optometry: Rod dysfunction (e.g., in retinitis pigmentosa or vitamin A deficiency) causes night blindness, which optometrists diagnose through history and fundus examination.

Q56. Which test measures the curvature of the cornea?

Options:

• 1. Retinoscopy
• 2. Keratometry
• 3. Tonometry
• 4. Visual acuity test

Correct Answer: 2. Keratometry

Explanation:

Keratometry measures the curvature of the cornea’s anterior surface, typically in diopters or millimeters of radius, to assess its refractive power. It is used in contact lens fitting, refractive surgery planning, and diagnosing conditions like keratoconus (irregular corneal curvature).

• Option 1: Retinoscopy estimates refractive error by observing light reflections from the retina.
• Option 3: Tonometry measures intraocular pressure, not corneal curvature.
• Option 4: Visual acuity tests (e.g., Snellen chart) assess clarity of vision, not corneal shape.

Relevance for Optometry: Keratometry is essential for fitting contact lenses and diagnosing corneal disorders, ensuring optimal vision correction.

Q57. What does the Snellen chart test?

Options:

• 1. Color vision
• 2. Visual acuity
• 3. Depth perception
• 4. Eye pressure

Correct Answer: 2. Visual acuity

Explanation:

The Snellen chart is a standardized tool used to measure visual acuity, the clarity or sharpness of vision, typically at a distance of 20 feet (6 meters). It consists of letters of decreasing size, with results expressed as a fraction (e.g., 20/20 indicates normal vision).

• Option 1: Color vision is tested with tools like Ishihara plates.
• Option 3: Depth perception is assessed with stereopsis tests (e.g., Randot test).
• Option 4: Eye pressure is measured with tonometry.

Relevance for Optometry: Visual acuity testing with the Snellen chart is a fundamental part of eye exams to diagnose refractive errors and monitor vision changes.

Q58. Which nerve is responsible for the sensation of the cornea?

Options:

• 1. Optic nerve (CN II)
• 2. Oculomotor nerve (CN III)
• 3. Trigeminal nerve (CN V)
• 4. Facial nerve (CN VII)

Correct Answer:3. Trigeminal nerve (CN V)

Explanation:

The cornea is innervated by the ophthalmic branch (V1) of the trigeminal nerve (cranial nerve V), which provides sensory innervation for touch, pain, and temperature sensations. This makes the cornea highly sensitive, aiding in protective reflexes like blinking.

• Option 1: The optic nerve (CN II) transmits visual information from the retina, not corneal sensation.
• Option 2: The oculomotor nerve (CN III) controls eye muscles and pupil constriction, not sensation.
• Option 4: The facial nerve (CN VII) controls facial muscles and tearing, not corneal sensation.

Relevance for Optometry: Corneal sensation testing (e.g., with a cotton wisp) assesses trigeminal nerve function, important in diagnosing conditions like neurotrophic keratitis.

Q59. Which condition causes clouding of the eye's natural lens?

Options:

• 1. Glaucoma
• 2. Cataract
• 3. Macular degeneration
• 4. Diabetic retinopathy

Correct Answer: 2. Cataract

Explanation:

A cataract is the clouding of the eye’s natural lens, leading to blurred vision, glare, and reduced color perception. It is often age-related but can also result from trauma, medications, or systemic diseases.

• Option 1: Glaucoma involves optic nerve damage due to increased IOP, not lens clouding.
• Option 3: Macular degeneration affects the retina’s macula, impairing central vision.
• Option 4: Diabetic retinopathy involves retinal blood vessel damage, not lens opacity.

Relevance for Optometry: Cataracts are diagnosed via slit-lamp examination, and optometrists refer patients for surgical intervention (lens replacement) when vision is significantly impaired.

Q60. What type of lens is used to correct hyperopia (farsightedness)?

Options:

• 1. Convex lens
• 2. Concave lens
• 3. Cylindrical lens
• 4. Plano lens

Correct Answer: 1. Convex lens

Explanation:

Hyperopia (farsightedness) occurs when light focuses behind the retina due to a short eyeball or insufficient refractive power. Convex lenses (positive power, converging) add focusing power to shift the focal point forward onto the retina.

• Option 2: Concave lenses (negative power, diverging) correct myopia, not hyperopia.
• Option 3: Cylindrical lenses correct astigmatism, not spherical errors like hyperopia.
• Option 4: Plano lenses have no refractive power and do not correct hyperopia.

Relevance for Optometry: Convex lenses are prescribed for hyperopia to improve near and sometimes distance vision, depending on the degree of error.