Amblyopia — MCQs
Strabismic amblyopia is more common in patients with:
What does a visual acuity test primarily assess?
A 50-year-old patient has difficulty reading close objects. Likely diagnosis?
The most common type of strabismus seen in myopes is?
The most common cause of myopia is –
Treatment of presbyopia is by use of which type of lens?
A patient presents with convergent squint in one eye. Vision in the squinting eye is 6/60, and vision in the non-squinting eye is also 6/60. What is the most appropriate next step in management?
What is the critical period for the development of the fixation reflex?
Which of the following conditions is inherited in an autosomal dominant pattern?
Which of the following extraocular muscles of the eye is involved in intorsion, depression, and abduction of the eyeball?
Amblyopia Indian Medical PG Practice Questions and MCQs
Question 1: Strabismic amblyopia is more common in patients with:
- A. Constant strabismus (Correct Answer)
- B. Alternating strabismus
- C. Latent strabismus
- D. Intermittent strabismus
Explanation: **Constant Strabismus** - In **constant strabismus**, one eye is always deviated, leading to **continuous suppression** of the image from the deviated eye by the brain. - This consistent suppression prevents proper visual development in the deviated eye, resulting in **amblyopia**. *Alternating strabismus* - In **alternating strabismus**, the deviation switches between the two eyes, allowing each eye to take turns fixing. - This alternation helps maintain relatively good visual acuity in both eyes, making **amblyopia less common** or severe. *Latent strabismus* - **Latent strabismus** (phoria) is a deviation that is only present when binocular fusion is disrupted (e.g., when one eye is covered). - Since fusion is typically maintained in daily vision, there is **no constant suppression** of one eye, and amblyopia is rare. *Intermittent strabismus* - **Intermittent strabismus** involves periods of deviation alternating with periods of straight eye alignment, often varying with fatigue or visual tasks. - While it can lead to amblyopia, it is **less common and severe** than with constant strabismus because there are periods when the visual input from both eyes is utilized.
Question 2: What does a visual acuity test primarily assess?
- A. Ability to perceive light
- B. Ability to differentiate colors
- C. Ability to recognize shapes and details (Correct Answer)
- D. Ability to detect contrast
Explanation: ***Ability to recognize shapes and details*** - A visual acuity test, typically using a **Snellen chart**, measures the sharpness of vision, specifically the ability to discern letters or symbols at a given distance. - It assesses the eye's capacity to resolve fine **spatial detail**, which is crucial for tasks like reading and recognizing faces. - This is the fundamental definition of visual acuity and what these tests are specifically designed to measure. *Ability to perceive light* - This refers to **light perception (LP)**, the most basic form of vision, indicating whether a person can detect the presence or absence of light. - While essential for vision, it is a much simpler function than what visual acuity tests measure and is assessed separately. *Ability to differentiate colors* - This is assessed by **color vision tests**, such as the Ishihara plates, which evaluate the function of cone photoreceptors. - It specifically checks for **color blindness** (e.g., red-green or blue-yellow deficiencies) and is distinct from the sharpness of vision. *Ability to detect contrast* - This is measured by **contrast sensitivity tests**, which evaluate the ability to distinguish objects from their background at various contrast levels. - While related to overall visual quality, it is a different aspect of vision than the ability to recognize fine details at high contrast.
Question 3: A 50-year-old patient has difficulty reading close objects. Likely diagnosis?
- A. Hypermetropia
- B. Astigmatism
- C. Myopia
- D. Presbyopia (Correct Answer)
Explanation: ***Presbyopia*** - This condition is characterized by the **loss of elasticity** in the lens of the eye, which occurs naturally with age, making it difficult to focus on **near objects**. - Its typical presentation, as seen in this 50-year-old patient, is **difficulty reading close objects** or performing other tasks requiring near vision. *Hypermetropia* - Often causes **farsightedness**, meaning distant objects are seen clearly, but near objects appear blurry due to the eye attempting to constantly accommodate. - While it can make near vision difficult, it is not primarily an age-related loss of accommodation and can affect individuals of various ages. *Astigmatism* - Results from an **irregular curvature of the cornea or lens**, causing blurred or distorted vision at all distances, rather than specifically difficulty with close objects. - This condition makes it difficult for the eye to focus light uniformly on the retina, leading to multiple focal points or streaks. *Myopia* - This is commonly known as **nearsightedness**, where distant objects appear blurry while near objects are seen clearly. - It occurs when the eyeball is too long or the cornea is too steeply curved, causing light to focus in front of the retina.
Question 4: The most common type of strabismus seen in myopes is?
- A. Intermittent Exotropia (Correct Answer)
- B. Intermittent Esotropia
- C. Esotropia Hypotropia complex
- D. Exotropia Hypotropia complex
Explanation: ***Intermittent Exotropia*** - Myopes often employ less **accommodative effort** for near tasks, leading to reduced **accommodative convergence** and an increased tendency for the eyes to drift outwards. - This outward deviation, or **exotropia**, is frequently intermittent, especially during fatigue or inattention. *Intermittent Esotropia* - **Esotropia** is an inward turn of the eye and is typically associated with **hyperopia** due to excessive accommodative effort leading to increased accommodative convergence. - While it can be intermittent, it is not the most common form of strabismus in myopic individuals. *Esotropia hypotropia complex* - This complex involves both an inward deviation (**esotropia**) and a downward deviation (**hypotropia**). - It is not typically seen in healthy myopes and would suggest other underlying **neurological** or **structural abnormalities**. *Exotropia Hypotropia complex* - While **exotropia** can be common in myopes, the additional presence of **hypotropia** (downward deviation) suggests a more complex strabismic picture. - This combination is not the most frequent strabismus seen in uncomplicated myopia and may indicate **cranial nerve palsies** or **orbital anomalies**.
Question 5: The most common cause of myopia is –
- A. Altered curvature of the lens
- B. Increased anteroposterior (A–P) diameter of the eye (Correct Answer)
- C. Increased intraocular pressure
- D. Changes in the vitreous humor structure
Explanation: ***Increased anteroposterior (A–P) diameter of the eye*** - This leads to the light rays focusing **in front of the retina**, which is the hallmark of **myopia** (nearsightedness) - The longer axial length means the eye's refractive power is too strong for its length - **Axial myopia** is the most common type, accounting for approximately **90% of all myopia cases** - Each 1 mm increase in axial length causes approximately **3 diopters of myopia** *Altered curvature of the lens* - While changes in lens curvature can contribute to refractive errors, they are a **less common primary cause** of myopia compared to increased axial length - These changes typically result in **refractive myopia** (curvature myopia), which accounts for only a small percentage of cases - More commonly associated with lenticular changes in conditions like early cataracts or keratoconus *Increased intraocular pressure* - **Increased intraocular pressure** is the primary characteristic of **glaucoma** and does **not directly cause myopia** - Elevated pressure can damage the optic nerve leading to vision loss, but it doesn't typically alter the eye's focal length - However, chronic angle-closure glaucoma can sometimes lead to secondary changes, but this is not a primary cause *Changes in the vitreous humor structure* - Changes in the **vitreous humor**, such as liquefaction or detachment, can cause symptoms like **floaters** or flashes of light - However, these changes do **not directly lead to myopia** or alter the eye's refractive power significantly to cause nearsightedness - Vitreous changes are typically age-related or associated with high myopia as a consequence, not a cause
Question 6: Treatment of presbyopia is by use of which type of lens?
- A. Convex (Correct Answer)
- B. Concave
- C. Biconcave
- D. Concavoconvex
Explanation: **Convex** - **Presbyopia** is an age-related condition where the **lens stiffens**, impairing its ability to accommodate and focus on near objects. - **Convex lenses** add converging power to the eye, helping to bring near objects into focus on the retina. *Concave* - **Concave lenses** diverge light rays and are used to correct **myopia (nearsightedness)**, where the eye focuses images in front of the retina. - They spread light out before it enters the eye, pushing the focal point back onto the retina. *Biconcave* - **Biconcave lenses** are a type of concave lens with two concave surfaces, used for correcting severe **myopia (nearsightedness)**. - These lenses further diverge light rays and are not suitable for presbyopia, which requires converging power. *Concavoconvex* - A **concavoconvex lens** has one concave and one convex surface; its overall power depends on the relative curvatures of the two surfaces. - While some forms might be used in specialized optical systems, they are not the primary or standard correction for presbyopia, which typically requires a simple converging (convex) power.
Question 7: A patient presents with convergent squint in one eye. Vision in the squinting eye is 6/60, and vision in the non-squinting eye is also 6/60. What is the most appropriate next step in management?
- A. Glasses
- B. Refraction and treat underlying cause of poor vision (Correct Answer)
- C. Squint surgery
- D. Botulinum toxin
Explanation: ***Refraction and treat underlying cause of poor vision*** - When **both eyes have equally poor vision (6/60)** with a convergent squint, this suggests a **bilateral pathology** affecting visual acuity, not simply a refractive accommodative esotropia. - The **first step** is comprehensive **cycloplegic refraction** to determine if refractive error contributes to the poor vision. - **Equally important** is identifying the **underlying cause** of bilateral vision loss (6/60 in both eyes), which could be: - **Bilateral amblyopia** (though unusual to have equal severity) - **Uncorrected high refractive error** (hypermetropia causing accommodative esotropia) - **Cataracts** (congenital or developmental) - **Retinal pathology** or **optic nerve disorders** - Only after identifying and treating the underlying cause can definitive management of the squint be planned. *Glasses* - While **glasses** may be part of the treatment if refractive error is found, **prescribing glasses alone** without first performing refraction and investigating why both eyes have 6/60 vision is incomplete management. - This option is too narrow and doesn't address the need to identify the underlying pathology causing bilateral poor vision. *Squint surgery* - **Squint surgery** addresses ocular misalignment but does **not improve vision**. - Surgery should only be considered **after** refractive correction, treatment of amblyopia (if present), and management of any underlying pathology. - Operating without addressing the cause of poor vision would be premature. *Botulinum toxin* - **Botulinum toxin** is used for certain types of strabismus as a temporary or alternative to surgery. - Like surgery, it addresses alignment but **not visual acuity**. - The priority is to improve vision and identify the underlying cause before considering alignment procedures.
Question 8: What is the critical period for the development of the fixation reflex?
- A. 2-4 months of age (Correct Answer)
- B. 6-8 months of age
- C. 2 years
- D. 3 years
Explanation: **Explanation:** The development of visual function in infants follows a specific chronological sequence. The **fixation reflex** is the ability of the eyes to focus on and follow an object. While a rudimentary fixation reflex is present at birth, it undergoes a critical maturation phase between **2 to 4 months of age**. By the end of the 4th month, a healthy infant should demonstrate steady, central, and maintained fixation. * **Why Option A is correct:** The neural pathways connecting the retina to the visual cortex and the motor pathways for ocular movement mature rapidly during this window. If an infant does not show steady fixation by 4 months, it is a clinical red flag for sensory deprivation (like congenital cataracts) or neurological delay. * **Why Options B, C, and D are incorrect:** By **6-8 months**, higher-order functions like stereopsis (depth perception) are maturing. **2 to 3 years** represents the tail end of the "plastic period" for amblyopia treatment, but the foundational reflex of fixation is established much earlier in infancy. **High-Yield Clinical Pearls for NEET-PG:** * **Visual Acuity at Birth:** Approximately 6/60 to 6/120 (reaches adult levels of 6/6 by 3–5 years). * **Stereopsis:** Begins at 3–4 months and is well-developed by 6 months. * **Critical Period for Amblyopia:** The period during which the visual system is plastic and sensitive to abnormal visual input; it lasts from birth until approximately **7–9 years of age**. * **Accommodation:** Reaches adult-like levels by **4 months**.
Question 9: Which of the following conditions is inherited in an autosomal dominant pattern?
- A. Retinoblastoma (Correct Answer)
- B. Ataxia telangiectasia
- C. Bloom's syndrome
- D. Xeroderma pigmentosa
Explanation: **Explanation:** The correct answer is **Retinoblastoma (Option A)**. Retinoblastoma is the most common primary intraocular malignancy of childhood. While 60% of cases are sporadic and unilateral, 40% are hereditary. Hereditary retinoblastoma follows an **Autosomal Dominant** inheritance pattern with high penetrance (90%). It is caused by a mutation in the **RB1 gene** located on chromosome **13q14**. According to **Knudson’s Two-Hit Hypothesis**, in hereditary cases, the first mutation (hit) is germline (inherited), and the second is somatic. This explains why hereditary cases are often bilateral, multifocal, and present at an earlier age. **Why the other options are incorrect:** * **Ataxia Telangiectasia (Option B):** This is an **Autosomal Recessive** multisystem disorder characterized by cerebellar ataxia, oculocutaneous telangiectasia, and immunodeficiency. It involves a defect in the ATM gene (DNA repair). * **Bloom’s Syndrome (Option C):** This is an **Autosomal Recessive** disorder characterized by short stature, photosensitivity, and genomic instability due to mutations in the BLM gene. * **Xeroderma Pigmentosa (Option D):** This is an **Autosomal Recessive** condition caused by a defect in nucleotide excision repair, leading to extreme sensitivity to UV light and a high risk of skin malignancies. **High-Yield Clinical Pearls for NEET-PG:** * **Most common presenting sign:** Leukocoria (White pupillary reflex). * **Second most common sign:** Strabismus. * **Pathognomonic Histology:** Flexner-Wintersteiner rosettes. * **Calcification:** Present in 90% of cases (visible on CT/Ultrasound B-scan); a key diagnostic feature. * **Trilateral Retinoblastoma:** Bilateral retinoblastoma associated with a pinealoblastoma.
Question 10: Which of the following extraocular muscles of the eye is involved in intorsion, depression, and abduction of the eyeball?
- A. Inferior rectus
- B. Superior rectus
- C. Inferior oblique
- D. Superior oblique (Correct Answer)
Explanation: **Explanation:** The actions of the extraocular muscles are determined by their anatomical origin and insertion relative to the center of rotation of the eyeball. **1. Why Superior Oblique (SO) is correct:** The Superior Oblique originates from the body of the sphenoid, passes through the **trochlea** (acting as a functional origin), and inserts into the postero-superior quadrant of the globe. Because it inserts behind the equator and approaches from the front-medial side, its contraction results in: * **Primary Action:** Intorsion (Inward rotation) * **Secondary Action:** Depression (Downwards) * **Tertiary Action:** Abduction (Outwards) * *Mnemonic:* **"SIN"** (Superior muscles are Intorters) and **"Obliques are Abductors."** **2. Why the other options are incorrect:** * **Inferior Rectus (IR):** Its primary action is depression, but its secondary actions are **extorsion** and **adduction**. * **Superior Rectus (SR):** Its primary action is elevation. Its secondary actions are **intorsion** and **adduction**. * **Inferior Oblique (IO):** Its primary action is **extorsion**. Its secondary actions are elevation and abduction. **High-Yield Clinical Pearls for NEET-PG:** * **RAD Rule:** Recti are Adductors (except Lateral Rectus). * **SIN Rule:** Superior muscles (SR & SO) are Intorters; Inferior muscles (IR & IO) are Extorters. * **Oblique Rule:** Obliques are Abductors; Recti are Adductors. * **Nerve Supply:** All muscles are supplied by CN III except Superior Oblique (**CN IV** - Trochlear) and Lateral Rectus (**CN VI** - Abducens) [Formula: **LR6SO4**]. * **Clinical Testing:** To isolate the Superior Oblique’s action of depression, the eye must be placed in an **adducted** position.
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