Hereditary Retinal Dystrophies — MCQs
What is the best diagnostic test for Best vitelliform macular dystrophy?
In diabetic retinopathy, which layer of the retina is primarily affected?
Retinitis pigmentosa is characterized by ?
Which of the following is not a true statement regarding the classic findings in retinitis pigmentosa?
A patient presents with superior quadrant vision loss since one week. Patient has Rheumatic Heart Disease (RHD) and is not taking medications. What is the most likely diagnosis?
Which one of the following is an autosomal dominant disorder?
Which of the following vascular lesions has the least clinical significance?
Arden index is related to
All are manifestation of dengue virus infection in eye except?
A-wave in Electroretinogram corresponds to the activity of
Hereditary Retinal Dystrophies Indian Medical PG Practice Questions and MCQs
Question 1: What is the best diagnostic test for Best vitelliform macular dystrophy?
- A. Dark adaptation
- B. ERG
- C. EOG (Correct Answer)
- D. Gonioscopy
Explanation: ***EOG*** - The **electrooculogram (EOG)** measures the **standing potential of the eye** and is typically abnormal in Best vitelliform macular dystrophy. - This test is crucial for diagnosis as it shows a **reduced Arden ratio**, even in asymptomatic carriers. *Dark adaptation* - **Dark adaptation** tests are used to assess the function of rod photoreceptors but are typically **normal** in Best vitelliform macular dystrophy. - This condition primarily affects the retinal pigment epithelium and cone function in the macula, not overall rod adaptation. *ERG* - The **electroretinogram (ERG)** measures the **mass electrical response of the retina** to light stimulation and is usually **normal** in Best vitelliform macular dystrophy. - While it assesses photoreceptor and bipolar cell function, the specific dystrophy primarily impacts the RPE, which the ERG may not fully capture. *Gonioscopy* - **Gonioscopy** is an examination technique used to visualize the **anterior chamber angle** of the eye. - It is primarily used for diagnosing and monitoring **glaucoma** and has no role in diagnosing retinal dystrophies like Best vitelliform macular dystrophy.
Question 2: In diabetic retinopathy, which layer of the retina is primarily affected?
- A. Layer of rods and cones
- B. Retinal pigment epithelium
- C. Outer plexiform layer
- D. Inner nuclear layer (Correct Answer)
Explanation: ***Inner nuclear layer*** - The inner nuclear layer contains the **retinal capillary network**, which is the primary site of pathology in diabetic retinopathy. - **Microangiopathy** (pericyte loss, basement membrane thickening, endothelial cell damage) occurs in the capillaries located within this layer. - **Microaneurysms**, the earliest ophthalmoscopic sign of diabetic retinopathy, form from damaged capillaries in the inner nuclear layer. - **Diabetic macular edema (DME)** involves fluid accumulation that begins at the level of the capillaries in the inner nuclear and inner plexiform layers, then extends to the outer plexiform layer. *Outer plexiform layer* - This layer is **secondarily affected** by leakage from damaged capillaries in deeper retinal layers (inner nuclear and inner plexiform layers). - **Hard exudates** (lipid and protein deposits) accumulate in the outer plexiform layer as a consequence of capillary leakage, but this is not the primary site of vascular pathology. - The outer plexiform layer itself has minimal vasculature and is not where the initial microvascular changes occur. *Layer of rods and cones* - Photoreceptors are affected only in advanced stages of diabetic retinopathy due to chronic ischemia and secondary damage. - The primary pathology is vascular and occurs in the inner retinal layers where capillaries are located, not in the avascular photoreceptor layer. *Retinal pigment epithelium* - The RPE is not directly affected by the microvascular changes that characterize diabetic retinopathy. - RPE dysfunction is more characteristic of **age-related macular degeneration (AMD)** and other degenerative conditions. - In diabetic retinopathy, the RPE may be affected indirectly in very advanced cases but is not a primary site of pathology.
Question 3: Retinitis pigmentosa is characterized by ?
- A. Loss of central vision
- B. Visual field constriction
- C. Tubular vision
- D. Loss of peripheral vision (Correct Answer)
Explanation: ***Loss of peripheral vision*** - Retinitis pigmentosa is a group of genetic disorders that cause **progressive degeneration of photoreceptor cells**, primarily rods, which are concentrated in the periphery of the retina. - This degeneration leads to a gradual **loss of peripheral vision**, often beginning with **night blindness** and progressing to tunnel vision. *Loss of central vision* - Loss of central vision is characteristic of conditions affecting the **macula**, such as **age-related macular degeneration** or certain forms of **macular dystrophy**. - While later stages of retinitis pigmentosa can affect central vision, the initial and primary characteristic is loss of peripheral vision. *Tubular vision* - **Tubular vision** is an advanced stage of peripheral vision loss, where the visual field shrinks to a narrow central area, resembling looking through a tube. - While it can be a consequence of retinitis pigmentosa, it is a description of the **extent of visual field constriction** rather than the primary characteristic of the disease itself. *Visual field constriction* - **Visual field constriction** is a general term for any reduction in the extent of the visual field. - While retinitis pigmentosa certainly causes visual field constriction, the term "loss of peripheral vision" is more specific to the initial and dominant pattern of vision loss in this condition.
Question 4: Which of the following is not a true statement regarding the classic findings in retinitis pigmentosa?
- A. Disc edema is part of the classic triad of RP findings (Correct Answer)
- B. Argus 2 retinal implant is used as a treatment modality
- C. Electrophysiological changes appear early in the disease before the objective signs
- D. The classic triad includes peripheral pigmentation, attenuated vessels, and optic atrophy. Disc edema is not part of the triad.
Explanation: ***Disc edema is part of the classic triad of RP findings*** - This statement is **FALSE** and is therefore the correct answer to this negatively-worded question. - The **classic triad** of findings in **retinitis pigmentosa** includes **peripheral pigmentary retinopathy** (bone-spicule pigmentation), **attenuated retinal vessels**, and **waxy pallor of the optic disc** (optic atrophy). - **Disc edema is NOT part of the classic triad** - its presence would suggest an alternative or co-existing pathology such as papillitis or papilledema. *RP is associated with Cystoid macular edema* - This is a **true** statement - **cystoid macular edema (CME)** is a well-recognized complication of **retinitis pigmentosa** and often contributes to central vision loss in affected individuals, occurring in approximately 10-50% of RP patients. *Argus 2 retinal implant is used as a treatment modality* - This is a **true** statement - the **Argus II retinal prosthesis** is an FDA-approved treatment option for patients with severe to profound **retinitis pigmentosa** who have lost useful vision, providing some restoration of functional vision. *Electrophysiological changes appear early in the disease before the objective signs* - This is a **true** statement - **electrophysiological changes**, particularly abnormalities on the **electroretinogram (ERG)**, are often the **earliest detectable signs** of **retinitis pigmentosa**, appearing even before visible funduscopic changes or significant symptoms develop.
Question 5: A patient presents with superior quadrant vision loss since one week. Patient has Rheumatic Heart Disease (RHD) and is not taking medications. What is the most likely diagnosis?
- A. CRAO
- B. CRVO
- C. BRAO (Correct Answer)
- D. BRVO
Explanation: ***BRAO*** - **Branch retinal artery occlusion** (BRAO) presents with **sudden, painless sectoral or quadrant visual field loss** corresponding to the distribution of the occluded arterial branch. - Superior quadrant vision loss indicates **inferior retinal involvement** (visual field is inverted on retina). - **Rheumatic heart disease** not on anticoagulation poses high risk for **cardiac emboli** from valvular vegetations or atrial fibrillation, which preferentially cause **arterial occlusions** (BRAO/CRAO). - Fundoscopy shows **retinal whitening** in the affected area with a clear demarcation line. *BRVO* - **Branch retinal vein occlusion** causes quadrant vision loss but is **NOT typically embolic** in nature. - BRVO is associated with systemic **vascular risk factors** (hypertension, diabetes, hyperlipidemia), not cardiac emboli. - Fundoscopy shows **flame-shaped hemorrhages** and cotton-wool spots in a wedge distribution. *CRAO* - **Central retinal artery occlusion** presents with **complete, sudden painless monocular vision loss** affecting the entire visual field. - Shows classic **"cherry-red spot"** at the fovea due to diffuse retinal ischemia. - Would not present with isolated quadrant vision loss. *CRVO* - **Central retinal vein occlusion** causes **complete monocular vision loss** with "blood and thunder" appearance on fundoscopy. - Presents with diffuse retinal hemorrhages throughout the retina, not isolated to one quadrant.
Question 6: Which one of the following is an autosomal dominant disorder?
- A. Cystic fibrosis
- B. Hereditary spherocytosis (Correct Answer)
- C. Sickle cell anemia
- D. G-6PD deficiency
Explanation: ***Hereditary spherocytosis*** - It is characterized by **autosomal dominant inheritance** [1], leading to the destruction of red blood cells. - Mutations in proteins that maintain the **red blood cell membrane** integrity result in spherocyte formation [1]. *Cystic fibrosis* - This condition follows a **autosomal recessive inheritance pattern**, requiring two copies of the mutated gene for disease manifestation. - It is caused by mutations in the **CFTR gene**, affecting chloride transport and leading to thick secretions. *G-6PD deficiency* - This disorder is inherited in an **X-linked recessive manner** [2], primarily affecting males and transmitted through carrier females. - Characterized by **hemolytic anemia** triggered by certain medications or infections, it does not follow dominant inheritance [2]. *Sickle cell anemia* - Sickle cell anemia is also an **autosomal recessive disorder** [3], meaning affected individuals must inherit two copies of the sickle cell gene. - It results in a mutation in the **HBB gene**, leading to the production of abnormal hemoglobin (HbS) [3].
Question 7: Which of the following vascular lesions has the least clinical significance?
- A. Monckeberg's medial calcification (Correct Answer)
- B. Glomus tumor
- C. Hyaline arteriolosclerosis
- D. Hyperplastic arteriolosclerosis
Explanation: ***Monckeberg's medial calcification*** - This condition involves **calcification** of the media layer of the arteries and is typically **asymptomatic** with little clinical significance. - It does not obstruct blood flow and is usually found incidentally on imaging, making it a benign finding. *Hyperplastic aeriolosclerosis* - This lesion is associated with **hyperplasia** of smooth muscle cells and can lead to complications in conditions such as **hypertension** [1]. - It may indicate underlying vascular disease, thus having more clinical importance than Monckeberg's. *Glomus tumor* - Glomus tumors, while benign, can cause significant pain and discomfort, typically occurring under the nail bed. - Their potential for local invasion and distorting normal anatomy makes them clinically significant. *Hyaline aeriolosclerosis* - This condition is characterized by **hyaline deposition** in small arteries and is often associated with chronic hypertension and diabetes [1]. - It can indicate vascular injury and related complications, thus having more clinical relevance. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 498-499.
Question 8: Arden index is related to
- A. ERG (Electroretinogram)
- B. VER (Visual Evoked response)
- C. Perimetry
- D. EOG (Electrooculogram) (Correct Answer)
Explanation: ***EOG (Electrooculogram)*** - The **Arden index** is a measure derived from the **electrooculogram (EOG)**, which assesses the function of the **retinal pigment epithelium (RPE)**. - It represents the ratio of the maximum light peak to the minimum dark trough recorded during EOG, with a normal value typically above 1.8. *ERG (Electroretinogram)* - The **electroretinogram (ERG)** measures the **electrical responses of photoreceptors and other retinal cells** to light stimuli. - While it assesses retinal function, it does not directly yield the Arden index; that is specific to EOG readings. *VER (Visual Evoked response)* - **Visual evoked response (VER)** or **VEP (visual evoked potential)** measures the **electrical activity in the brain's visual cortex** in response to visual stimuli. - It assesses the integrity of the visual pathway from the optic nerve to the cortex, not directly the function of the RPE or the Arden index. *Perimetry* - **Perimetry**, or **visual field testing**, maps the sensitivity of the entire visual field, helping to detect deficits in peripheral or central vision. - It evaluates the functional extent of vision rather than the electrical activity of specific retinal layers or the RPE as assessed by the Arden index.
Question 9: All are manifestation of dengue virus infection in eye except?
- A. Cataract (Correct Answer)
- B. Vitreous hemorrhage
- C. Maculopathy
- D. Optic neuritis
Explanation: ***Cataract*** - **Cataracts** are primarily associated with aging, congenital factors, trauma, or long-term steroid use, not directly with acute dengue virus infection. - While dengue can cause various ocular manifestations, the formation of cataracts is a **chronic process** that does not fit the typical acute or subacute presentation of dengue-related eye complications. *Vitreous hemorrhage* - **Vitreous hemorrhage** can occur in dengue due to associated **thrombocytopenia** and coagulation abnormalities, leading to bleeding in the eye. - Severe dengue can induce systemic vasculopathy and bleeding tendencies, which may manifest as intraocular hemorrhage. *Maculopathy* - **Dengue maculopathy** is a recognized complication, often presenting as macular edema, hemorrhage, or foveolitis, leading to visual impairment. - This is thought to be due to direct viral effects, immune-mediated responses, or vasculitis affecting the retinal microvasculature. *Optic neuritis* - **Optic neuritis** following dengue infection has been reported, characterized by inflammation of the optic nerve, causing acute vision loss. - This is considered to be an **immune-mediated post-infectious complication** rather than a direct viral cytopathic effect on the nerve.
Question 10: A-wave in Electroretinogram corresponds to the activity of
- A. Pigment epithelium
- B. Rods and cones (Correct Answer)
- C. Nerve fibre layer
- D. Ganglion cell layer
Explanation: ***Rods and cones*** - The **'a' wave** of the Electroretinogram (ERG) represents the **initial negative deflection**, primarily generated by the activity of the **photoreceptors** (rods and cones) in response to light stimulation. - This wave reflects the **hyperpolarization** of the photoreceptor cells as they absorb light and initiate the visual transduction cascade. *Pigment epithelium* - The **retinal pigment epithelium (RPE)** plays a crucial role in supporting photoreceptor function and has a slower, sustained electrical response, which contributes more to the **c-wave** of the ERG. - While the RPE is vital for retinal function, its primary electrical contribution is not represented by the initial negative a-wave. *Nerve fibre layer* - The **nerve fiber layer** consists of the axons of ganglion cells and does not directly contribute to the primary a-wave or b-wave of the ERG as it is involved in transmitting signals to the brain. - Damage to this layer may affect overall visual function but is not the source of the initial photoreceptor-driven electrical response. *Ganglion cell layer* - The **ganglion cell layer** is responsible for sending visual information to the brain, and its activity is typically reflected in later, more complex components of the ERG or in other electrophysiological tests like pattern ERG. - The initial photoreceptor response (a-wave) occurs upstream of the ganglion cell activity.
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