Vision and Optics — MCQs
All are true regarding cornea except:
A female presents with loss of vision in the right halves of both eyes. Where is the lesion located in the optic pathway?
Match the following: A) Glossopharyngeal nerve B) Spinal accessory nerve C) Facial nerve D) Mandibular nerve 1) Shrugging of shoulder 2) Touch sensation from the posterior one-third of the tongue 3) Chewing 4) Taste from the anterior two-thirds of the tongue
A 25-year-old male gets into a brawl outside a bar. During the altercation, someone pulls out a gun and shoots him in the head. The bullet enters the man's temple and severes his right optic nerve completely. He is quickly transported to a nearby emergency room and an emergency physician tests his pupillary response by shining a light in the right eye. What will the physician most likely find?
Retinal cells which secrete acetylcholine are:
Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.
Which of the following structures is responsible for detecting rotational acceleration?
A patient presents with an anesthetic patch in areas of the face. Which of the following nerves is the most commonly involved in this condition?
Following endarterectomy on the right common carotid, a patient is found to be blind in the right eye. It appears that a small thrombus embolized during surgery and lodged in the artery supplying the retina. Which artery would be blocked?
Which is the earliest feature of multiple sclerosis ?
Vision and Optics Indian Medical PG Practice Questions and MCQs
Question 1: All are true regarding cornea except:
- A. The cornea is richly vascular. (Correct Answer)
- B. Endothelium help in maintaining dehydrated state
- C. Oxygen is mostly derived by epithelium directly from the air through tear film
- D. Corneal thickness is greater at periphery than center
Explanation: ***The cornea is richly vascular.*** - The cornea is an **avascular** tissue, meaning it lacks blood vessels, which is crucial for its transparency. - This avascularity helps prevent light scatter and maintains clear vision. - The cornea receives nutrition from the **aqueous humor**, **tear film**, and **limbal blood vessels** through diffusion. *Endothelium help in maintaining dehydrated state* - The **corneal endothelium** actively pumps fluid out of the corneal stroma via **Na-K-ATPase pumps**, preventing swelling and maintaining its relative state of dehydration. - This **deturgescence** is essential for the cornea's transparency and optimal refractive power. *Oxygen is mostly derived by epithelium directly from the air through tear film* - The corneal **epithelium** primarily obtains oxygen directly from the atmosphere via the **tear film** when the eyes are open. - During sleep, oxygen is primarily supplied by the **palpebral conjunctival vessels**. *Corneal thickness is greater at periphery than center* - The cornea is **thinner at the center** (around 520-540 µm) and gradually **thicker towards the periphery** (around 600-640 µm). - This structural difference contributes to its optical properties and mechanical stability.
Question 2: A female presents with loss of vision in the right halves of both eyes. Where is the lesion located in the optic pathway?
- A. Left optic tract (Correct Answer)
- B. Optic radiation
- C. Optic chiasma
- D. Right optic tract
Explanation: Left optic tract - A lesion in the **left optic tract** causes **right homonymous hemianopsia**, meaning loss of vision in the right halves of both eyes [1]. - This is because the left optic tract carries visual information from the **nasal retina of the right eye** and the **temporal retina of the left eye**, both of which process the right visual field [1]. *Optic radiation* - A lesion in the optic radiation would also cause a **homonymous hemianopsia** but depending on the specific location within the radiation, it could result in a **quadrantanopia** (loss of a quarter visual field) rather than a complete hemianopsia. - The optic radiation projects from the **lateral geniculate nucleus** to the **visual cortex**, and damage here affects the post-chiasmatic visual pathway [1]. *Optic chiasma* - A lesion at the **optic chiasma** typically results in **bitemporal hemianopsia**, which is the loss of vision in the **temporal halves of both eyes** [1]. - This occurs because the **crossing nasal fibers** from both eyes, which carry information from the temporal visual fields, are affected [1]. *Right optic tract* - A lesion in the **right optic tract** would result in **left homonymous hemianopsia**, meaning loss of vision in the **left halves of both eyes** [1]. - This is due to the right optic tract carrying fibers from the **nasal retina of the left eye** and the **temporal retina of the right eye**, both of which process the left visual field [1].
Question 3: Match the following: A) Glossopharyngeal nerve B) Spinal accessory nerve C) Facial nerve D) Mandibular nerve 1) Shrugging of shoulder 2) Touch sensation from the posterior one-third of the tongue 3) Chewing 4) Taste from the anterior two-thirds of the tongue
- A. A-3 , B-1 , C-4 , D-2
- B. A-2 , B-3 , C-4 , D-1
- C. A-4 , B-1 , C-2 , D-3
- D. A-2 , B-1 , C-4 , D-3 (Correct Answer)
Explanation: ***A-2 , B-1 , C-4 , D-3*** - **A) Glossopharyngeal nerve (CN IX)** is responsible for **general sensation and taste from the posterior one-third of the tongue** [1]. (2). - **B) Spinal Accessory nerve (CN XI)** innervates the **sternocleidomastoid** and **trapezius muscles**, which are involved in shrugging the shoulders (1). - **C) Facial nerve (CN VII)** carries **taste sensation from the anterior two-thirds of the tongue** [1] (4) via the chorda tympani. - **D) Mandibular nerve (V3)**, a branch of the trigeminal nerve, innervates the muscles of mastication, enabling **chewing** (3). *A-3 , B-1 , C-4 , D-2* - This option incorrectly associates the **glossopharyngeal nerve** with chewing, which is a function of the mandibular nerve (V3). - It also incorrectly associates the **mandibular nerve** with touch sensation from the posterior one-third of the tongue, which is a function of the glossopharyngeal nerve [1]. *A-2 , B-3 , C-4 , D-1* - This option incorrectly links the **spinal accessory nerve** with chewing; this nerve primarily controls shoulder and neck movements. - It also incorrectly assigns shrugging of the shoulder to the **mandibular nerve** instead of the spinal accessory nerve. *A-4 , B-1 , C-2 , D-3* - This choice incorrectly attributes **taste from the anterior two-thirds of the tongue** to the glossopharyngeal nerve, which supplies the posterior one-third [1]. - It also incorrectly links **touch sensation from the posterior one-third of the tongue** to the facial nerve, which is involved in taste from the anterior two-thirds [1].
Question 4: A 25-year-old male gets into a brawl outside a bar. During the altercation, someone pulls out a gun and shoots him in the head. The bullet enters the man's temple and severes his right optic nerve completely. He is quickly transported to a nearby emergency room and an emergency physician tests his pupillary response by shining a light in the right eye. What will the physician most likely find?
- A. Pupillary constriction followed by pupillary dilatation in both eyes
- B. Pupillary constriction in the right eye, and no pupillary constriction in the left eye
- C. No pupillary constriction in the right eye, and no pupillary constriction in the left eye (Correct Answer)
- D. No pupillary constriction in the right eye, but pupillary constriction in the left eye
Explanation: ***No pupillary constriction in the right eye, and no pupillary constriction in the left eye*** - The **afferent limb** of the **pupillary light reflex** is carried by the **optic nerve**. Complete transection of the right optic nerve means the right eye cannot detect light. - When light is shone into the blind right eye, the brain receives no sensory input, so neither the right pupil (direct response) nor the left pupil (consensual response) will constrict. *Pupillary constriction followed by pupillary dilatation in both eyes* - This scenario would imply an initial detection of light by the right eye, which is impossible with a **severed optic nerve**. - A subsequent dilation might suggest a different neurological issue or drug effect, not a primary pupillary light reflex to light in a blind eye. *Pupillary constriction in the right eye, and no pupillary constriction in the left eye* - This is incorrect because a **severed optic nerve** means the right eye cannot send the signal for constriction, neither directly nor consensually. - Furthermore, pupillary constriction *only* in the right eye (direct response) without a consensual response in the left eye would suggest an issue with the efferent pathway to the left eye, not a unilateral afferent lesion. *No pupillary constriction in the right eye, but pupillary constriction in the left eye* - This response pattern would occur if there was a lesion *after* the **optic chiasm** affecting the nerve fibers going to the right side, but the information from the right eye was still able to cross and activate the left pupil. - With a completely severed right optic nerve, no light stimulus can be transmitted from the right eye to initiate any reflex, therefore no constriction would occur in either eye.
Question 5: Retinal cells which secrete acetylcholine are:
- A. Bipolar cells
- B. Ganglion cells
- C. Amacrine cells (Correct Answer)
- D. Horizontal cells
Explanation: ***Amacrine cells*** - A subpopulation of **amacrine cells** in the retina is known to be **cholinergic**, meaning they synthesize and release **acetylcholine**. - These cholinergic amacrine cells play a role in **directional selectivity** and spatial processing within the retina. *Bipolar cells* - **Bipolar cells** primarily act as interneurons that transmit signals from photoreceptors to ganglion cells in the retina. - They typically release **glutamate** as their neurotransmitter, not acetylcholine. *Ganglion cells* - **Ganglion cells** are the output neurons of the retina, whose axons form the **optic nerve**. - While they receive input from cholinergic amacrine cells, ganglion cells themselves do not secrete acetylcholine; they are primarily glutamatergic. *Horizontal cells* - **Horizontal cells** are interneurons that provide lateral inhibition in the outer plexiform layer of the retina. - They primarily release **GABA** (gamma-aminobutyric acid) as their neurotransmitter, not acetylcholine.
Question 6: Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.
- A. Statements 1 & 2 are correct, 2 is not explaining 1 (Correct Answer)
- B. Statements 1 and 2 are correct and 2 is the correct explanation for 1
- C. Statements 1 and 2 are incorrect
- D. Statement 1 is incorrect
Explanation: ***Correct: Statements 1 & 2 are correct, 2 is not explaining 1*** **Analysis of Statement 1:** - A 59-year-old patient with **flaccid bullae** and **suprabasal acantholytic split** on histopathology is the classic presentation of **Pemphigus vulgaris** - The flaccid (easily ruptured) nature of bullae distinguishes it from tense bullae seen in bullous pemphigoid - The suprabasal location of the split (just above the basal layer) with acantholysis (loss of cell-to-cell adhesion) is pathognomonic - **Statement 1 is CORRECT** ✓ **Analysis of Statement 2:** - The **"row of tombstones" or "tombstone appearance"** is indeed a diagnostic histopathological feature of Pemphigus vulgaris - This appearance results from basal keratinocytes remaining attached to the basement membrane while suprabasal cells separate due to acantholysis - The intact basal cells standing upright resemble a row of tombstones - **Statement 2 is CORRECT** ✓ **Does Statement 2 explain Statement 1?** - Statement 2 describes a **histopathological appearance** (tombstone pattern) that is a **consequence** of the suprabasal split - However, it does NOT explain the **underlying cause** of the flaccid bullae or the suprabasal split - The true explanation involves **IgG autoantibodies against desmoglein 3 (and desmoglein 1)**, which attack intercellular adhesion structures (desmosomes), causing **acantholysis** - Therefore, **Statement 2 does NOT explain Statement 1** ✗ *Incorrect: Statement 2 is the correct explanation for Statement 1* - While both statements describe features of Pemphigus vulgaris, the tombstone appearance is a descriptive finding, not an explanatory mechanism *Incorrect: Statements 1 and 2 are incorrect* - Both statements are medically accurate descriptions of Pemphigus vulgaris features *Incorrect: Statement 1 is incorrect* - Statement 1 correctly describes the cardinal clinical and histopathological features of Pemphigus vulgaris
Question 7: Which of the following structures is responsible for detecting rotational acceleration?
- A. Semicircular canals (Correct Answer)
- B. Cochlea
- C. Fovea centralis
- D. Saccule
Explanation: ***Semicircular canals*** - The **semicircular canals** are part of the inner ear and are specifically designed to detect **rotational acceleration** of the head. - They contain a fluid called **endolymph** and hair cells within the **ampulla** that are stimulated by the movement of this fluid during rotation. *Cochlea* - The **cochlea** is primarily responsible for processing **auditory (sound) information**, not head movement. - It contains the **organ of Corti**, which converts sound vibrations into electrical signals. *Fovea centralis* - The **fovea centralis** is a part of the **retina** responsible for sharp, central vision and **high visual acuity**. - It plays no role in detecting head acceleration or balance. *Saccule* - The **saccule** is part of the **otolith organs** (along with the utricle) and detects **linear acceleration** and the pull of gravity in the vertical plane. - It is involved in sensing up-and-down movements and static head tilt, not rotational acceleration.
Question 8: A patient presents with an anesthetic patch in areas of the face. Which of the following nerves is the most commonly involved in this condition?
- A. Facial nerve
- B. Abducens nerve
- C. Trigeminal nerve (Correct Answer)
- D. Optic nerve
Explanation: ***Trigeminal nerve*** - The **trigeminal nerve** (CN V) is responsible for **sensory innervation of the face, scalp, and mucous membranes** of the mouth and nose [1]. An anesthetic patch suggests a loss of sensation in these areas. - Involvement of the trigeminal nerve, particularly its branches (ophthalmic, maxillary, mandibular), would lead to **paresthesia, numbness, or anesthesia** in the corresponding dermatomes of the face. *Abducens nerve* - The **abducens nerve** (CN VI) primarily controls the **lateral rectus muscle**, responsible for **abduction of the eye**. - Dysfunction of this nerve would lead to **diplopia (double vision)** and an inability to move the eye laterally, not facial anesthesia. *Facial nerve* - The **facial nerve** (CN VII) is mainly responsible for **motor innervation of the muscles of facial expression** and taste from the anterior two-thirds of the tongue. - Damage to this nerve causes **facial weakness or paralysis** (e.g., Bell's palsy) and taste disturbances, not loss of sensation (anesthesia) in facial skin. *Optic nerve* - The **optic nerve** (CN II) is solely responsible for **vision**. - Damage to the optic nerve results in **visual field defects or blindness**, not sensory changes on the face.
Question 9: Following endarterectomy on the right common carotid, a patient is found to be blind in the right eye. It appears that a small thrombus embolized during surgery and lodged in the artery supplying the retina. Which artery would be blocked?
- A. Nasociliary artery
- B. Infraorbital artery
- C. Lacrimal artery
- D. Central artery of the retina (Correct Answer)
Explanation: ***Central artery of the retina*** - The **central artery of the retina** is a branch of the **ophthalmic artery** that supplies blood to the inner two-thirds of the retina, including the **photoreceptors** and **ganglion cells**. - Its occlusion, often due to an **embolus** like in this scenario, leads to sudden, **painless monocular vision loss**, often described as a "curtain" coming down, which aligns with **blindness in the right eye**. *Nasociliary artery* - The **nasociliary artery** supplies structures like the **ethmoid sinuses**, **dura mater**, and part of the **nasal cavity**. - It does not directly supply the **optic nerve** or the **retina** and its occlusion would not cause blindness. *Infraorbital artery* - The **infraorbital artery** supplies structures in the **maxilla**, **lower eyelid**, and part of the **cheek**. - Its occlusion would primarily affect these areas and would not result in **blindness**. *Lacrimal artery* - The **lacrimal artery** primarily supplies the **lacrimal gland**, which produces tears, as well as parts of the **eyelids** and **conjunctiva**. - While it's a branch of the ophthalmic artery, its occlusion would not directly cause **blindness** by affecting the retina or optic nerve.
Question 10: Which is the earliest feature of multiple sclerosis ?
- A. Internuclear opthalmoplegia
- B. Cerebellar ataxia
- C. Diplopia
- D. Optic neuritis (Correct Answer)
Explanation: ***Optic neuritis*** - **Optic neuritis** is often the initial manifestation of **multiple sclerosis (MS)**, presenting as monocular vision loss, eye pain, and a relative afferent pupillary defect [3]. - Due to **demyelination** of the optic nerve, it can precede other neurological symptoms by years. *Internuclear ophthalmoplegia* - This condition is characterized by impaired adduction of one eye during conjugate lateral gaze with nystagmus of the abducting eye, caused by a lesion in the **medial longitudinal fasciculus** [1]. - While it is a classic sign of MS, it typically appears later in the disease course, not usually as the **first symptom** [1]. *Cerebellar ataxia* - **Cerebellar ataxia** manifests as incoordination, unsteady gait, and dysarthria, resulting from demyelination in the cerebellum or its pathways [4]. - Although common in MS, it is rarely the **presenting complaint** and generally develops as the disease progresses. *Diplopia* - **Diplopia (double vision)** in MS often results from **cranial nerve palsies** (e.g., abducens nerve palsy) or **internuclear ophthalmoplegia** [2]. - While it can be an early symptom, **optic neuritis** is generally considered the **earliest and most common initial presentation**.
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