Pediatric Ophthalmology and Strabismus — MCQs

Pediatric Ophthalmology and Strabismus Indian Medical PG Practice Questions and MCQs

Question 291: Which muscle is primarily affected in Duane syndrome?

A. Lateral rectus muscle (Correct Answer)
B. Superior rectus muscle
C. Medial rectus muscle
D. Superior oblique muscle

Explanation: ***Lateral rectus muscle*** - In Duane syndrome, the **lateral rectus muscle** is the primarily affected muscle due to **congenital absence or hypoplasia of the abducens nucleus (CN VI)**. - The lateral rectus receives **aberrant innervation from branches of the oculomotor nerve (CN III)** instead of normal abducens innervation. - This leads to **co-contraction** of both medial and lateral rectus muscles during attempted adduction, causing the characteristic **globe retraction and narrowing of palpebral fissure**. - The hallmark clinical finding is **limited or absent abduction** of the affected eye due to the primary lateral rectus dysfunction. *Medial rectus muscle* - The medial rectus has normal innervation from CN III in Duane syndrome. - While it participates in the co-contraction phenomenon, it is **not the primarily affected muscle**. - The pathology originates in the lateral rectus, not the medial rectus. *Superior rectus muscle* - The superior rectus muscle is responsible for **elevation, adduction, and intorsion** of the eye. - Its dysfunction is not characteristic of Duane syndrome, which primarily affects **horizontal eye movements**. *Superior oblique muscle* - The superior oblique muscle primarily causes **depression, abduction, and intorsion** of the eye. - Duane syndrome's core pathology involves the lateral rectus and horizontal gaze limitations, not superior oblique function.

Question 292: Iris coloboma is most common in which location?

A. Superotemporal
B. Inferonasal (Correct Answer)
C. Inferotemporal
D. Superonasal

Explanation: ***Inferonasal*** - **Iris coloboma** most commonly occurs in the **inferonasal quadrant** (at approximately the **6 o'clock position**) - This location corresponds to the site of the **embryonic fetal fissure** (choroidal fissure), which normally closes during the **5th to 7th week of gestation** - When the fetal fissure fails to close completely, it results in a **keyhole-shaped defect** in the iris, and potentially involves other ocular structures (ciliary body, choroid, retina, optic nerve) along the same inferonasal axis - This is a well-established anatomical pattern seen in **congenital colobomas** *Inferotemporal* - The inferotemporal quadrant is **not the typical location** for iris coloboma - Embryologically, the fetal fissure does not extend into the temporal region, making colobomas in this location extremely rare - Colobomas outside the inferonasal location are usually **atypical colobomas** caused by different mechanisms *Superotemporal* - The superotemporal quadrant is **not associated** with the fetal fissure closure pathway - Colobomas in this location would be considered atypical and not related to embryonic fissure closure defects - This is not a common presentation for congenital iris coloboma *Superonasal* - The superonasal quadrant is also **not part of the fetal fissure pathway** - While superior colobomas can occasionally occur as atypical variants, they do not represent the classic congenital coloboma pattern - The embryological basis for typical coloboma formation does not involve the superior regions of the eye

Question 293: When should surgery be performed for congenital cataracts with visual disturbances?

A. After 2 months
B. After 4 months
C. After 1 year
D. As soon as possible (within 6-10 weeks) (Correct Answer)

Explanation: ***As soon as possible (within 6-10 weeks)*** - **Early surgical intervention** (within the first few weeks of life) is crucial for congenital cataracts to prevent **irreversible visual deficits**, such as **amblyopia**. - The brain's visual pathways develop rapidly in infancy, and prolonged visual deprivation from cataracts can lead to **permanent impairment**. *After 2 months* - This time frame represents a delay that can increase the risk of **amblyopia** and poorer visual outcomes. - The critical period for visual development is very early in life, making immediate intervention vital. *After 4 months* - A delay of four months significantly increases the likelihood of **dense amblyopia** and **strabismus**, making complete visual rehabilitation much more challenging. - At this age, the potential for achieving good vision post-surgery dramatically decreases due to entrenched abnormal visual processing. *After 1 year* - Performing surgery at one year or later for congenital cataracts is generally considered too late, often resulting in **profound and irreversible amblyopia**. - The visual system will have already established abnormal connections, making significant improvement in visual acuity unlikely.

Question 294: What is the most common cause of amblyopia?

A. Cortical visual impairment
B. Strabismus
C. Deprivation amblyopia
D. Refractive errors (Correct Answer)

Explanation: ***Refractive errors*** - **Refractive amblyopia**, particularly **anisometropia** (a significant difference in refractive power between the eyes), is the most common cause globally, accounting for approximately 50% of all amblyopia cases. - This imbalance prevents clear retinal images from forming in one eye, leading to its visual underdevelopment. *Strabismus* - **Strabismic amblyopia** is caused by ocular misalignment, where the brain suppresses the image from the misaligned eye to avoid double vision. - While a significant cause (30-40% of cases), it is less common overall than amblyopia due to uncorrected refractive errors. *Deprivation amblyopia* - This is caused by any obstruction of the visual axis, such as **congenital cataracts** or **ptosis**, which physically blocks light from reaching the retina. - Although severe, it is the least common type of amblyopia (<10% of cases). *Cortical visual impairment* - This results from damage to the visual cortex or posterior visual pathways, not from abnormal visual input during the critical period of development. - While it causes visual deficits, it is not classified as amblyopia, which is specifically a developmental disorder of the visual system due to abnormal visual experience.

Question 295: Child with mild squint. Intrauterine, birth history, developmental history till date all normal. Corneal light reflex normal. All other eye parameters normal except exaggerated epicanthal fold. Diagnosis ?

A. Pseudostrabismus (Correct Answer)
B. Exophoria (outward drift)
C. Esophoria (inward drift)
D. Accommodative esotropia

Explanation: ***Pseudostrabismus*** * The presence of **exaggerated epicanthal folds** can create the optical illusion of a child having misaligned eyes, even when the eyes are perfectly straight. * The normal **corneal light reflex** (Hirschberg test) confirms that the eyes are properly aligned, and the perceived "squint" is not a true strabismus. *Exophoria (outward drift)* * This condition involves a **tendency for the eyes to drift outwards**, which would be detected by specific cover/uncover tests. * An outward drift would usually result in an abnormal corneal light reflex, and the exaggerated epicanthal folds would not explain this type of misalignment. *Esophoria (inward drift)* * This is a **tendency for the eyes to drift inwards**, which would also be revealed by tests for phorias and often by an abnormal corneal reflex. * The clinical presentation points away from a true inward deviation, as the corneal reflex is normal. *Accommodative esotropia* * This is a **true inward turning of the eye** (strabismus) that is often linked to uncorrected farsightedness (hyperopia). * It would present with an **abnormal corneal light reflex** and would not be explained solely by epicanthal folds, as it involves actual ocular deviation.

Question 296: How is the angle of squint measured?

A. Gonioscopy
B. Prism (Correct Answer)
C. Retinoscopy
D. Keratometry

Explanation: ***Prism*** - The **angle of squint**, which indicates the deviation of the eyes, is most accurately measured using **prisms** in conjunction with the **prism cover test** or **alternate prism cover test**. - Prisms quantify the degree of ocular deviation in **prism diopters** by neutralizing the misalignment so that the light falls correctly on the fovea. *Gonioscopy* - This technique is used to examine the **anterior chamber angle** of the eye, which is relevant for diagnosing conditions like **glaucoma**. - It does not involve measuring the angle of ocular deviation or misalignment of the eyes. *Retinoscopy* - Retinoscopy is an objective method to determine the **refractive error** of the eye (e.g., myopia, hyperopia, astigmatism). - While it assesses the eye's ability to focus light, it does not directly measure the angle of a squint. *Keratometry* - Keratometry measures the **curvature of the cornea**, primarily used for fitting contact lenses or calculating intraocular lens power for cataract surgery. - It does not assess the alignment of the eyes or the magnitude of a squint.

Question 297: What is the treatment of choice for amblyopia?

A. Corrective spectacles
B. Surgical intervention
C. Occlusion therapy (Correct Answer)
D. Convergent exercises for vision therapy

Explanation: ***Occlusion therapy*** - **Occlusion therapy** involves patching the stronger eye to force the weaker, amblyopic eye to work harder, thereby strengthening its neural connections. - This treatment is most effective when initiated during the **critical period of visual development** in childhood. *Corrective spectacles* - While essential for addressing **refractive errors** that may contribute to amblyopia, spectacles alone are often insufficient to resolve the amblyopia. - Spectacles primarily optimize the image quality on the retina, but don't directly address the **cortical suppression** of the amblyopic eye. *Surgical intervention* - **Surgical intervention** is typically reserved for correcting structural issues like **strabismus** (misalignment of the eyes) that contribute to amblyopia. - Surgery for strabismus aims to align the eyes, which can then be followed by occlusion therapy or other treatments to address the functional amblyopia. *Convergent exercises for vision therapy* - **Vision therapy exercises**, including convergent exercises, may be used as an adjunct to occlusion therapy or in cases of **convergence insufficiency**. - However, they are not the primary or solitary treatment of choice for amblyopia, which requires direct stimulation of the amblyopic eye.

Question 298: Which of the following statements about amblyopia is true?

A. Irreversible loss of vision
B. Can be associated with strabismus (Correct Answer)
C. Primarily caused by uncorrected refractive error
D. None of the above

Explanation: ***Can be associated with strabismus*** - **Amblyopia**, or **lazy eye**, is a developmental problem where the brain favors one eye over the other, leading to reduced vision in the weaker eye. - **Strabismus** (misalignment of the eyes) is one of the three major causes of amblyopia because the brain suppresses the image from the misaligned eye to avoid **diplopia** (double vision), leading to the visual pathway of that eye not developing properly. - This statement is unequivocally true and represents a well-established association. *Irreversible loss of vision* - Amblyopia, if detected and treated early during the **critical period of visual development** (typically before age 7-8), is often reversible or significantly improvable. - Treatment involves **patching the stronger eye** or using atropine penalization drops to force the brain to use the weaker eye, promoting its visual development. - While some cases may have persistent deficits if detected late, calling it "irreversible" is incorrect. *Primarily caused by uncorrected refractive error* - While **anisometropia** (significant refractive difference between eyes) and **high bilateral refractive errors** are indeed common causes of amblyopia, the word "primarily" suggests this is the main or dominant cause. - Amblyopia has **three equally important categories of causes**: strabismic, refractive (anisometropic/isoametropic), and deprivation amblyopia. - The relative frequency varies by population and screening methods, making it inaccurate to designate one as the singular "primary" cause. - This statement is partially true but less precise than the strabismus association. *None of the above* - This option is incorrect because the statement "Can be associated with strabismus" is definitively true.

Question 299: What is the term for a latent deviation of the eyes that can be revealed under certain conditions?

A. Phoria (Correct Answer)
B. Tropia
C. Apparent squint
D. Manifest strabismus

Explanation: ***Phoria*** - A **phoria** is a **latent deviation** of the eyes that is normally corrected by the patient's **fusion mechanisms**. - It becomes manifest only when **fusion is disrupted**, such as when one eye is covered or the patient is fatigued. *Apparent squint* - This term is sometimes used to describe the **optical illusion** of strabismus due to facial features, such as a wide nasal bridge or epicanthal folds, when the eyes are actually aligned. - It is not a true ocular misalignment but rather a perceived deviation. *Manifest strabismus* - **Manifest strabismus**, also known as **tropia**, is a **constant or intermittent deviation** of one or both eyes that is always present and cannot be controlled by the patient's fusion mechanisms. - It is a **visible misalignment** of the eyes under normal viewing conditions. *Tropia* - **Tropia** is synonymous with **manifest strabismus**, meaning the eye deviation is **always present** and visible under binocular viewing conditions. - Unlike phoria, a tropia is not masked by fusion and does not require disruption of fusion to be observed.

Question 300: All are true about concomitant squint except which of the following?

A. Angle of primary deviation is equal to angle of secondary deviation
B. Diplopia is typically absent
C. Position of head is typically normal.
D. There may be a limitation of movement in some cases (Correct Answer)

Explanation: ***There may be a limitation of movement in some cases.*** - In concomitant squint, there is **no primary limitation of ocular movement**; the deviation is constant in all directions of gaze. - A limitation of movement would suggest an **incomitant** or paralytic squint, where the deviation varies with gaze direction. *Angle of primary deviation is equal to angle of secondary deviation* - This statement is **true** for concomitant squints, meaning the deviation is the same regardless of which eye is fixing. - Primary deviation refers to the deviation when the unaffected eye is fixing, and secondary deviation is when the affected eye is fixing. *Diplopia is typically absent* - This statement is generally **true** in concomitant strabismus, especially if the condition is long-standing and develops in childhood. - The brain often adapts to avoid double vision through mechanisms like **suppression** or **amblyopia**. *Position of head is typically normal.* - This statement is generally **true** for concomitant squints, as there is no specific gaze direction that minimizes the deviation. - A **compensatory head posture** (e.g., head turn or tilt) is more characteristic of **incomitant strabismus**, where it is adopted to maintain single vision in the field of action of a paretic muscle.

Practice by Chapter

Amblyopia

Practice Questions

Esotropia

Practice Questions

Exotropia

Practice Questions

Vertical Deviations

Practice Questions

Special Forms of Strabismus

Practice Questions

Nystagmus in Children

Practice Questions

Pediatric Cataract

Practice Questions

Retinopathy of Prematurity

Practice Questions

Pediatric Glaucoma

Practice Questions

Pediatric Neuro-ophthalmology

Practice Questions

Genetic Eye Diseases in Children

Practice Questions

Pediatric Ocular Trauma

Practice Questions

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