Vitamin A and Vision Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Vitamin A and Vision. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Vitamin A and Vision Indian Medical PG Question 1: During the dark phase of visual cycle, which form of vitamin A combines with opsin to make Rhodopsin:
- A. 11-cis-Retinaldehyde (Correct Answer)
- B. 11-cis-Retinol
- C. All trans-Retinol
- D. All trans-Retinaldehyde
Vitamin A and Vision Explanation: ***11-cis-Retinaldehyde***
- In the **dark phase** of the visual cycle, **11-cis-retinaldehyde** (retinal) is regenerated and combines with **opsin** to form **rhodopsin**.
- This molecule is crucial for initiating the visual transduction pathway in **rod cells** when light is detected.
*11-cis-Retinol*
- **11-cis-Retinol** is an intermediate in the regeneration of 11-cis-retinaldehyde from all-trans-retinol, but it does not directly bind to opsin to form rhodopsin.
- It is converted to 11-cis-retinaldehyde by the enzyme **11-cis-retinol dehydrogenase**.
*all trans-Retinol*
- **All-trans-retinol** is the form of vitamin A transported to the eye and is also an intermediate in the visual cycle, but it does not combine directly with opsin.
- It is converted to all-trans-retinaldehyde after the absorption of light and then subsequently isomerized to 11-cis-retinol.
*All trans-Retinaldehyde*
- **All-trans-retinaldehyde** is formed when **rhodopsin** absorbs light, causing the isomerization of 11-cis-retinaldehyde.
- This molecule is then released from opsin and subsequently reduced to all-trans-retinol before being recycled back to 11-cis-retinaldehyde in the pigment epithelium.
Vitamin A and Vision Indian Medical PG Question 2: Thiamine deficiency is best diagnosed by?
- A. Blood thiamine level
- B. Transketolase activity in blood (Correct Answer)
- C. Aldolase activity in blood
- D. Urinary thiamine level
Vitamin A and Vision Explanation: ***Transketolase activity in blood***
- **Transketolase** is a thiamine pyrophosphate (TPP)-dependent enzyme, and its activity in red blood cells is considered the **gold standard** for assessing thiamine status.
- A **decrease in transketolase activity** that improves after the addition of TPP in vitro (TPP effect) is highly indicative of thiamine deficiency.
*Blood thiamine level*
- While a direct measure, **blood thiamine levels** can be influenced by recent dietary intake and may not accurately reflect the body's overall thiamine stores or functional deficiency.
- Furthermore, measuring total blood thiamine doesn't always correlate well with the **functional status** of thiamine-dependent enzymes.
*Aldolase activity in blood*
- **Aldolase** is an enzyme involved in glycolysis, but its activity is **not dependent on thiamine**.
- Therefore, measuring aldolase activity provides no information regarding thiamine status.
*Urinary thiamine level*
- **Urinary thiamine levels** primarily reflect recent thiamine intake and renal excretion rather than the body's total thiamine stores or a functional deficiency.
- Low urinary thiamine can suggest deficiency, but it's **less reliable** than functional assays.
Vitamin A and Vision Indian Medical PG Question 3: At what age does a child typically know their full name?
- A. 15 months
- B. 24 months
- C. 36 months (Correct Answer)
- D. 48 months
Vitamin A and Vision Explanation: ***36 months***
- By **36 months old** (3 years), most children can clearly state their **full name** (first and last name) when asked.
- This milestone indicates developing **self-awareness** and **language skills**.
- This is a standard developmental milestone tested in CDC and AAP guidelines.
*15 months*
- At **15 months**, children typically know their **first name** and respond to it, but cannot state their full name.
- Their language at this age often includes only a few single words with primarily receptive understanding.
*24 months*
- By **24 months** (2 years), children often use two-to-four-word sentences and can identify familiar objects and people.
- While they know their first name and may start recognizing it, they usually cannot articulate their full name yet.
*48 months*
- At **48 months** (4 years), a child's language skills are much more advanced, and they can typically tell stories and engage in complex conversations.
- Knowing their full name is an expected milestone that should have been achieved earlier, typically by 36 months.
Vitamin A and Vision Indian Medical PG Question 4: Pseudo tumor cerebri is caused by?
- A. Vitamin B1 excess
- B. Vitamin D excess
- C. Vitamin E excess
- D. Vitamin A excess (Correct Answer)
Vitamin A and Vision Explanation: ***Vitamin A excess***
- **Hypervitaminosis A**, or excess vitamin A, is a known cause of **pseudotumor cerebri** (also called **idiopathic intracranial hypertension**).
- This condition involves increased **intracranial pressure**, often without an obvious structural cause.
*Vitamin B1 excess*
- Excess intake of **vitamin B1 (thiamine)** is generally considered benign and is not known to cause pseudotumor cerebri.
- Thiamine is a **water-soluble vitamin**, and excess amounts are typically excreted in urine.
*Vitamin D excess*
- **Vitamin D toxicity** primarily leads to **hypercalcemia**, which can cause kidney stones, bone pain, and gastrointestinal symptoms.
- While it can have neurological effects due to hypercalcemia, it typically does not directly cause pseudotumor cerebri.
*Vitamin E excess*
- **Vitamin E excess** can interfere with **blood clotting** and may increase the risk of bleeding, especially in individuals taking anticoagulants.
- There is no established link between hypervitaminosis E and the development of pseudotumor cerebri.
Vitamin A and Vision Indian Medical PG Question 5: Vitamin A is stored in
- A. Cells of Ito (Correct Answer)
- B. Hepatocyte
- C. Endothelial cell
- D. Kupffer cell
Vitamin A and Vision Explanation: ***Cells of Ito***
- **Ito cells**, also known as **hepatic stellate cells**, are the primary storage site for **vitamin A** in the body, specifically in lipid droplets within their cytoplasm.
- These cells play a crucial role in vitamin A homeostasis and are located in the **perisinusoidal space** (space of Disse) of the liver.
*Hepatocyte*
- **Hepatocytes** are the main functional cells of the liver and are involved in many metabolic processes, but their primary role is not **vitamin A storage**.
- While they metabolize and process vitamin A, the bulk of its storage occurs in the adjacent Ito cells.
*Endothelial cell*
- **Endothelial cells** line the vascular system, including the hepatic sinusoids, and are involved in nutrient and waste exchange, but not in significant **vitamin A storage**.
- Their primary function is to regulate vascular tone and permeability.
*Kupffer cell*
- **Kupffer cells** are specialized **macrophages** found in the liver, acting as antigen-presenting cells and clearing pathogens and debris.
- They are involved in immune surveillance and not in the long-term storage of **vitamin A**.
Vitamin A and Vision Indian Medical PG Question 6: A child of 8 kg has Bitot's spots in both eyes. Which of the following is the most appropriate schedule to prescribe vitamin A to this child?
- A. 2 lakh units orally on day 0, 14
- B. 2 lakh units orally on day 0, 1, 14 (Correct Answer)
- C. 1 lakh units orally on day 0, 14
- D. 1 lakh units orally on day 0, 1, 14
Vitamin A and Vision Explanation: ***2 lakh units orally on day 0, 1, 14***
- For a child weighing **8 kg** with **Bitot's spots (WHO classification X1B)**, the therapeutic dose is **200,000 IU** (2 lakh units) of vitamin A.
- The standard WHO/IAP schedule for treating **vitamin A deficiency with ocular signs** is administration on **Day 0, Day 1, and Day 14** to rapidly replete stores and prevent progression.
- The **oral route** is preferred for **Bitot's spots without corneal ulceration**, as it is effective, safe, and well-tolerated.
- **IM route** is reserved for severe xerophthalmia (X2/X3 with corneal ulceration), persistent vomiting, or inability to take oral medications.
*2 lakh units orally on day 0, 14*
- Although the individual dose of **200,000 IU** is correct for this 8 kg child with **Bitot's spots**, this schedule misses the critical **Day 1 dose**.
- The missing dose on Day 1 delays rapid **vitamin A replenishment**, which is crucial for preventing progression of **ocular damage** and achieving adequate tissue stores.
*1 lakh units orally on day 0, 14*
- This dose of **100,000 IU** is inadequate for a child weighing **8 kg or more** with clinical **vitamin A deficiency**.
- WHO guidelines recommend **100,000 IU for children <8 kg** and **200,000 IU for children ≥8 kg**, making this dosage insufficient.
- Additionally, the schedule is incomplete as it misses the **Day 1 dose**.
*1 lakh units orally on day 0, 1, 14*
- While the schedule of Day 0, Day 1, and Day 14 is appropriate, the **dose of 100,000 IU is inadequate** for a child weighing **8 kg**.
- This lower dose may not provide sufficient **vitamin A replenishment** to reverse **Bitot's spots** and prevent progression to more severe xerophthalmia.
Vitamin A and Vision Indian Medical PG Question 7: A patient complained of gradual diminution of vision. On examination, the patient had dry eyes and a rough corneal surface. What deficiency is most likely causing these manifestations?
- A. Iron
- B. Protein
- C. Niacin
- D. Vitamin A (Correct Answer)
Vitamin A and Vision Explanation: ***Vitamin A***
- **Vitamin A deficiency** is a common cause of **xerophthalmia**, characterized by **dry eyes** (**xerosis conjunctivae**) and roughening of the **cornea** due to impaired mucin production [1]. In vitamin A deficiency, mucus-secreting cells are replaced by keratin-producing cells [2].
- Progression of ocular epithelial keratinization can lead to **Bitot's spots**, corneal ulceration, and ultimately **blindness** [1], [2].
*Iron*
- **Iron deficiency** primarily leads to **iron-deficiency anemia**, causing fatigue, pallor, and weakness, but not directly ocular manifestations like dry eyes or rough cornea.
- While severe anemia can cause some visual disturbances, it does not typically present with the specific **xerophthalmic** changes seen here.
*Protein*
- **Protein deficiency** can lead to conditions like **kwashiorkor** (edema, muscle wasting) or **marasmus** (severe wasting), which broadly impair health and immunity.
- However, it does not directly cause the specific ocular signs of **dryness** and **corneal roughening** as a primary deficiency, though it can exacerbate other nutritional deficiencies.
*Niacin*
- **Niacin (Vitamin B3) deficiency** causes **pellagra**, characterized by the "3 Ds": **dermatitis**, **diarrhea**, and **dementia**.
- Ocular symptoms are not a common or primary feature of niacin deficiency; it does not cause **dry eyes** or **corneal roughening**.
Vitamin A and Vision Indian Medical PG Question 8: Match the following: A) Caplan syndrome- 1) Found first in coal worker B) Asbestosis- 2) Upper lobe predominance C) Mesothelioma- 3) Involves lower lobe D) Sarcoidosis- 4) Pleural effusion is seen
- A. A-3, B-4, C-2, D-1
- B. A-1, B-4, C-3, D-2 (Correct Answer)
- C. A-4, B-2, C-3, D-1
- D. A-2, B-4, C-3, D-1
Vitamin A and Vision Explanation: **A-1, B-4, C-3, D-2**
- **Caplan syndrome** was first described in **coal workers** with **rheumatoid arthritis** and progressive massive fibrosis.
- **Asbestosis** is often associated with **pleural effusion**, which can be benign or malignant.
- **Mesothelioma** typically involves the **lower lobes** of the lungs, specifically the pleura, and is strongly linked to asbestos exposure.
- **Sarcoidosis** is characterized by **non-caseating granulomas**, which have a predilection for the **upper lobes** of the lungs.
*A-3, B-4, C-2, D-1*
- This option incorrectly states that Caplan syndrome involves the lower lobe; **Caplan syndrome** is defined by the presence of large nodules in the lungs of coal workers with rheumatoid arthritis, and their specific lobar distribution is not a defining characteristic.
- This option incorrectly states that Mesothelioma has an upper lobe predominance; **Mesothelioma** is a pleural malignancy and typically involves the **lower lobes**, extending along the pleura.
*A-4, B-2, C-3, D-1*
- This option incorrectly associates Caplan syndrome with pleural effusion; **Caplan syndrome** manifests as rheumatoid nodules in the lungs, not primarily pleural effusion.
- This option incorrectly states that Asbestosis has an upper lobe predominance; **Asbestosis** predominantly affects the **lower lobes** of the lungs, causing interstitial fibrosis.
*A-2, B-4, C-3, D-1*
- This option incorrectly states that Caplan syndrome has an upper lobe predominance; the defining feature of **Caplan syndrome** is the combination of rheumatoid arthritis and pneumoconiosis, not specific lobar involvement.
- This option correctly identifies pleural effusion with asbestosis and lower lobe involvement with mesothelioma, but **Caplan syndrome** is not characterized by upper lobe predominance.
Vitamin A and Vision Indian Medical PG Question 9: Name the enzyme involved in this cycle:
- A. Retinal isomerase (Correct Answer)
- B. Retinol isomerase
- C. Transducin
- D. Gustducin
Vitamin A and Vision Explanation: ***Retinal isomerase***
- This enzyme is crucial for the regeneration of **11-cis-retinal** from **all-trans-retinal** in the visual cycle.
- It catalyzes the **isomerization** process, which is essential for rhodopsin to be reformed and ready to detect light again.
*Retinol isomerase*
- This term is a misnomer; the substrate that undergoes isomerization is retinal, not retinol.
- While **retinol** is a precursor to retinal, it doesn't directly undergo the isomerization step that is vital for the visual cycle.
*Transducin*
- **Transducin** is a **G-protein** involved in signal transduction after light activates rhodopsin.
- It binds to activated rhodopsin, triggering a cascade that ultimately leads to changes in membrane potential, but it is not an isomerase enzyme.
*Gustducin*
- **Gustducin** is a **G-protein** primarily involved in the **sensation of taste**, specifically bitter and sweet tastes.
- It plays no role in the visual cycle or the isomerization of retinal.
Vitamin A and Vision Indian Medical PG Question 10: All of the following are water-soluble antioxidants except?
- A. uric acid
- B. Polyphenols
- C. Carotenes (Correct Answer)
- D. Ascorbate
Vitamin A and Vision Explanation: ***Carotenes***
- **Carotenes** are **lipid-soluble** antioxidants that are typically found in cell membranes and lipid components of the body.
- They protect against **lipid peroxidation**, which is damage to cellular membranes caused by free radicals.
*Ascorbate*
- **Ascorbate** (Vitamin C) is a well-known **water-soluble** antioxidant that readily donates electrons to neutralize free radicals in aqueous environments.
- It plays a crucial role in regenerating other antioxidants, such as **alpha-tocopherol (Vitamin E)**.
*Uric acid*
- **Uric acid** is a potent **water-soluble** antioxidant present in high concentrations in the plasma.
- It scavenges various reactive oxygen species and reactive nitrogen species, especially in the **extracellular fluid**.
*Polyphenols*
- **Polyphenols** are a large group of **water-soluble** compounds found in plants that act as antioxidants.
- They reduce oxidative stress by **scavenging free radicals**, chelating metal ions, and inhibiting enzymes involved in radical generation.
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