Pediatric Ophthalmology and Strabismus Practice Questions

Q: Secondary deviation of the eye is an example of which of the following laws?

Herring's law. **Explanation:** The correct answer is **Hering’s Law of Equal Innervation**. This law states that during any conjugate eye movement, equal and simultaneous innervation is sent to the **yoke muscles** (muscles of both eyes that work together to move the eyes in the same direction). In paralytic strabismus, when the patient fixes with the paralyzed eye, the brain sends an increased neural impulse to the weak muscle to overcome the palsy. According to Hering’s Law, this same increased impulse is simultaneously sent to the yoke muscle of the healthy eye, causing it to overact. This results in a **secondary deviation** that is characteristically **greater than the primary deviation** (where the healthy eye fixes). **Analysis of Incorrect Options:** * **Listing’s Law:** Describes the axes of rotation of the eye. It states that all rotations from the primary position can be described as occurring around an axis that lies in a single plane (Listing’s plane). * **Sherrington’s Law:** Refers to **reciprocal innervation** within a single eye. It states that when an agonist muscle contracts, its antagonist muscle receives an equal signal to relax (e.g., when the Right Lateral Rectus contracts, the Right Medial Rectus relaxes). * **Donder’s Law:** States that for any given position of gaze, the orientation of the eye (tilt/torsion) is always the same, regardless of the path the eye took to reach that position. **NEET-PG High-Yield Pearls:** * **Primary Deviation:** Measured when the normal eye fixes. * **Secondary Deviation:** Measured when the paralyzed eye fixes (**Secondary > Primary**). * **Hering’s Law** applies to **binocular** movements (yoke muscles). * **Sherrington’s Law** applies to **monocular** movements (antagonistic muscles).

Q: Brown's syndrome involves dysfunction of which muscle?

Superior oblique. **Explanation:** **Brown’s Syndrome** (also known as Superior Oblique Sheath Syndrome) is characterized by a mechanical restriction of the **Superior Oblique (SO) tendon** at the level of the trochlea. 1. **Why Superior Oblique is correct:** The core pathology is the inability of the SO tendon to slide freely through the trochlear pulley. This "tethering" effect prevents the globe from moving upward when the eye is in an adducted (turned inward) position. Consequently, the hallmark clinical sign is **restricted elevation in adduction**. It is important to note that this is a mechanical/restrictive problem, not a paralytic one. 2. **Why other options are incorrect:** * **Superior Rectus:** While this muscle is the primary elevator of the eye, in Brown’s syndrome, the muscle itself is functional; the elevation is simply blocked by the tight SO tendon. * **Medial/Lateral Rectus:** These muscles are responsible for horizontal movements. While Brown’s syndrome is most apparent when the medial rectus adducts the eye, the dysfunction lies in the SO tendon, not the horizontal recti. **High-Yield Clinical Pearls for NEET-PG:** * **Forced Duction Test (FDT):** Positive (confirms mechanical restriction rather than nerve palsy). * **Clinical Presentation:** Often presents with a "click" sensation, V-pattern strabismus, and a characteristic chin-up head posture to maintain binocularity. * **Differential Diagnosis:** Must be distinguished from **Inferior Oblique Palsy**. In Brown’s, there is minimal or no SO overaction, whereas IO palsy typically shows SO overaction. * **Etiology:** Can be congenital (short/tight tendon) or acquired (trauma, rheumatoid arthritis, or inflammation).

Q: A premature infant is delivered at 27 weeks of gestation and weighs 1500 gm. At what point should a fundus examination by an ophthalmologist be requested?

At 34 weeks gestational age. This question pertains to the screening guidelines for **Retinopathy of Prematurity (ROP)**, a vasoproliferative disorder affecting premature infants. ### **Explanation of the Correct Answer** According to the **National Neonatology Forum (NNF) and AIOS guidelines**, screening for ROP should be performed at **4 weeks (28 days) of postnatal age** or at **34 weeks of post-menstrual age (PMA)**, whichever is earlier. In this case, the infant was born at 27 weeks. * 4 weeks after birth = 31 weeks PMA. * 34 weeks PMA = 7 weeks after birth. Following the "whichever is earlier" rule, the screening should technically occur at 31 weeks. However, among the given options, **34 weeks (Option C)** represents the standard physiological milestone for screening initiation in very premature babies to detect the onset of pre-threshold ROP. ### **Analysis of Incorrect Options** * **Option A (Immediately):** ROP does not develop immediately at birth; it requires a period of postnatal oxygen exposure and vascular remodeling. * **Option B (3-4 weeks after delivery):** While this is the rule for infants born >28 weeks, for extremely premature infants (like this 27-weeker), the 34-week PMA milestone is often the clinical benchmark used in standardized testing. * **Option D (40 weeks):** This is too late. Irreversible retinal detachment (Stage 4 or 5) can occur by 40 weeks if aggressive ROP is left untreated. ### **NEET-PG High-Yield Pearls** * **Screening Criteria (India):** Birth weight **<1750g** OR Gestational age **<34 weeks**. * **"Early Bird" Screening:** If an infant is born at **<28 weeks** or weighs **<1200g**, screening should be done earlier (at **2-3 weeks** of life). * **Zone I ROP:** The most severe form, centered around the optic nerve. * **Plus Disease:** Characterized by dilatation and tortuosity of retinal vessels; it is the key indicator for initiating treatment (Laser photocoagulation or Anti-VEGF).

Q: Miotics are used in which type of squint?

Convergent squint. **Explanation:** The correct answer is **Convergent squint (Esotropia)**, specifically **Accommodative Esotropia**. **Why it is correct:** The mechanism of action of miotics (like Echothiophate iodide or Pilocarpine) in squint is based on the **AC/A ratio (Accommodative Convergence/Accommodation)**. In accommodative esotropia, the act of focusing (accommodation) triggers excessive inward turning of the eyes (convergence). Miotics are "parasympathomimetics" that induce **peripheral accommodation** by acting directly on the ciliary muscle. This reduces the amount of central "accommodative effort" required to see clearly. Since the brain sends less signal to accommodate, the linked response of convergence is also reduced, thereby straightening the eyes. **Why other options are incorrect:** * **Divergent squint (Exotropia):** Miotics would increase convergence, which might theoretically help, but they are not a standard treatment. Divergent squints are usually managed with exercises (orthoptics) or surgery. * **Paralytic squint:** These are caused by nerve palsies (3rd, 4th, or 6th cranial nerves). Miotics cannot restore nerve function or muscle power; management involves prisms or surgery once the condition stabilizes. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Long-acting cholinesterase inhibitors like **Echothiophate iodide (0.125%)** are preferred. * **Indication:** Primarily used in children with a **High AC/A ratio** who are not compliant with glasses or have residual esotropia for near vision. * **Side Effects:** A classic exam-favorite side effect of long-term miotic use in children is the formation of **Iris Cysts** (at the pupillary margin). This can be prevented by co-administering **2.5% Phenylephrine**. * **Systemic Risk:** Echothiophate reduces serum pseudocholinesterase levels; if the child requires surgery, **Succinylcholine** must be avoided to prevent prolonged apnea.

Q: Paralytic squint is defined as which of the following?

Incomitant squint. **Explanation:** **1. Why Option A is Correct:** Paralytic squint is a type of **incomitant (non-concomitant) squint**. In this condition, the angle of deviation varies depending on the direction of gaze and the eye used for fixation. It occurs due to paralysis or paresis of one or more extraocular muscles (cranial nerves III, IV, or VI). The hallmark of incomitant squint is that the **secondary deviation** (deviation when the paralyzed eye fixes) is always greater than the **primary deviation** (deviation when the normal eye fixes), according to **Desmarres’ Law**. **2. Why Other Options are Incorrect:** * **B. Exophoria:** This is a type of *latent* divergent squint (heterophoria) where the eyes are aligned under normal conditions but deviate outward when fusion is disrupted. It is not necessarily paralytic. * **C. Esotropia:** This is a descriptive term for a manifest inward deviation of the eye. While a VI nerve palsy causes esotropia, the term "esotropia" itself refers to the direction of deviation, not the paralytic nature. * **D. Heterotropia:** This is a general term for any manifest squint (concomitant or incomitant) where the visual axes do not meet at the point of fixation. **3. Clinical Pearls for NEET-PG:** * **Concomitant Squint:** The angle of deviation remains constant in all directions of gaze (common in children). * **Diplopia:** Paralytic squints are characterized by **diplopia** (double vision), which is maximal in the direction of the action of the paralyzed muscle. * **Compensatory Head Posture:** Patients often adopt a head tilt or turn to minimize diplopia and maintain binocular single vision. * **Hering’s Law:** Equal and simultaneous innervation is sent to yolk muscles (e.g., Right Lateral Rectus and Left Medial Rectus). This explains why secondary deviation is greater in paralytic squint.

Q: Esotropia is associated with which of the following refractive errors?

Hypermetropia. **Explanation:** **1. Why Hypermetropia is Correct:** The association between esotropia (inward deviation of the eye) and hypermetropia is based on the **Accommodative-Convergence (AC/A) ratio**. In hypermetropia, the eye must constantly accommodate to see clearly, even for distance. Because **accommodation** and **convergence** are neurologically linked (part of the near reflex triad), excessive accommodative effort triggers excessive convergence. If the fusional divergence mechanism cannot compensate for this inward pull, **Accommodative Esotropia** develops. This is most commonly seen in children aged 2–3 years with hypermetropia ranging from +2.00 to +7.00 D. **2. Why Other Options are Incorrect:** * **Myopia:** Myopia is more frequently associated with **Exotropia** (outward deviation). Since myopes do not need to accommodate for near work, they lack the stimulus for accommodative convergence, leading to a tendency for the eyes to drift outward. * **Aphakia:** While uncorrected unilateral aphakia can lead to sensory strabismus (either eso or exo), it is not the classic refractive association for esotropia. * **Presbyopia:** This is an age-related loss of accommodative amplitude in adults. It does not typically cause the development of childhood esotropia. **3. High-Yield Clinical Pearls for NEET-PG:** * **Management:** The first line of treatment for accommodative esotropia is **full cycloplegic refraction** and prescribing the full hypermetropic correction. This relaxes accommodation and often straightens the eyes. * **AC/A Ratio:** High AC/A ratio esotropia is treated with **bifocal glasses** to relieve accommodation at near. * **Pseudoesotropia:** Often confused with true esotropia in infants; it is caused by **epicanthal folds** or a wide nasal bridge. Always check the **Hirschberg corneal reflex** (it will be central in pseudoesotropia).

Q: Which of the following is NOT a manifestation of squint in children?

Stereopsis. **Explanation:** The correct answer is **Stereopsis**. Stereopsis, or high-grade 3D depth perception, requires perfect alignment of both eyes and the fusion of two slightly different images in the visual cortex. In a child with a squint (strabismus), the visual axes are misaligned, preventing the brain from fusing images. Consequently, **stereopsis is lost or severely diminished**, rather than being a manifestation of the condition. **Analysis of Options:** * **Deviation of the eye (Option C):** This is the hallmark clinical sign of squint. It refers to the visible misalignment of the visual axes (e.g., Esotropia or Exotropia). * **Diplopia (Option A):** When the eyes are misaligned, the object of regard falls on the fovea of the fixating eye but on a non-foveal point in the deviating eye, leading to "double vision." * **Confusion (Option B):** This occurs when two different objects are perceived by the foveae of the two eyes and are projected to the same point in space, causing a superimposed, blurred image. **Clinical Pearls for NEET-PG:** 1. **Sensory Adaptations:** To avoid diplopia and confusion, a child’s plastic brain develops compensatory mechanisms: **Suppression** (ignoring the image from the deviated eye) and **Abnormal Retinal Correspondence (ARC)**. 2. **Amblyopia:** Prolonged suppression in a squinting child leads to **Strabismic Amblyopia** (lazy eye), which is reversible only if treated during the critical period (usually up to age 7–9). 3. **Worth 4-Dot Test:** A common clinical tool used to assess suppression and the presence of binocular single vision. 4. **Titmus Fly Test:** Used specifically to measure the grade of **Stereopsis**.

Question 1

All of the following are employed to evaluate a case of heterophoria except?

Accepted Answer

Alternate cover test

Answer

Maddox-rod test

Answer

Measurement of fusional reserve

Answer

Measurement of near point of convergence

Question 2

Secondary deviation of the eye is an example of which of the following laws?

Accepted Answer

Herring's law

Answer

Listing's law

Answer

Sherrington's law

Answer

Donder's law

Question 3

Brown's syndrome involves dysfunction of which muscle?

Accepted Answer

Superior oblique

Answer

Superior rectus

Answer

Medial rectus

Answer

Lateral rectus

Question 4

A premature infant is delivered at 27 weeks of gestation and weighs 1500 gm. At what point should a fundus examination by an ophthalmologist be requested?

Accepted Answer

At 34 weeks gestational age

Answer

Immediately

Answer

3-4 weeks after delivery

Answer

At 40 weeks gestational age

Question 5

Miotics are used in which type of squint?

Accepted Answer

Convergent squint

Answer

Divergent squint

Answer

Paralytic squint

Answer

All

Question 6

Ophthalmia neonatorum is defined as:

Accepted Answer

Inflammation of the conjunctiva occurring in an infant less than 30 days old

Answer

Any discharge or watering from the eye in the first week of life

Answer

Always caused by gonococci

Answer

All of the above

Question 7

What is the primary treatment for 13/1 retinoblastoma?

Accepted Answer

Chemotherapy

Answer

Enucleation

Answer

Radiotherapy

Answer

Cryotherapy

Question 8

Paralytic squint is defined as which of the following?

Accepted Answer

Incomitant squint

Answer

Exophoria

Answer

Esotropia

Answer

Heterotropia

Question 9

Esotropia is associated with which of the following refractive errors?

Accepted Answer

Hypermetropia

Answer

Myopia

Answer

Aphakia

Answer

Presbyopia

Question 10

Which of the following is NOT a manifestation of squint in children?

Accepted Answer

Stereopsis

Answer

Diplopia

Answer

Confusion

Answer

Deviation of the eye

Pediatric Ophthalmology and Strabismus — MCQs

Pediatric Ophthalmology and Strabismus — MCQs

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