Diseases of the Retina — MCQs

Diseases of the Retina Indian Medical PG Practice Questions and MCQs

Question 191: A 35-year-old patient with insulin-dependent diabetes mellitus (IDDM) who has been on insulin for 10 years complains of gradually progressive painless loss of vision. What is the most likely diagnosis?

A. Cataract (Correct Answer)
B. Vitreous hemorrhage
C. Total rhegmatogenous retinal detachment
D. Tractional retinal detachment not involving the macula

Explanation: **Explanation:** The most likely diagnosis in this patient is **Cataract**. In a long-standing diabetic patient (10 years of IDDM), the most common cause of **gradually progressive, painless loss of vision** is a cataract (specifically senile-type or "snowflake" metabolic cataract). While diabetic retinopathy is a major concern, the clinical presentation of slow, painless progression is the classic hallmark of lens opacification. **Analysis of Options:** * **A. Cataract (Correct):** Diabetes accelerates the formation of cataracts due to the accumulation of sorbitol in the lens via the polyol pathway, leading to osmotic swelling. It is the most frequent cause of gradual vision loss in this demographic. * **B. Vitreous Hemorrhage:** This typically presents as **sudden**, painless loss of vision or the appearance of "floaters" and "cobwebs," rather than a gradual decline. * **C. Total Rhegmatogenous Retinal Detachment:** This usually presents with a sudden onset of flashes (photopsia), floaters, and a "curtain-like" loss of the visual field, leading to rapid vision loss. * **D. Tractional Retinal Detachment (TRD):** While TRD is a complication of Proliferative Diabetic Retinopathy (PDR), the option specifies it does **not involve the macula**. If the macula is spared, the patient would likely maintain good central vision and would not complain of significant progressive loss of vision. **Clinical Pearls for NEET-PG:** * **Snowflake Cataract:** A specific type of bilateral subcapsular cataract seen in young patients with uncontrolled IDDM. * **Most common cause of legal blindness in diabetics:** Macular Edema (CSME). * **Most common cause of sudden painless vision loss in diabetics:** Vitreous Hemorrhage. * **Refractive changes:** Hyperglycemia often causes a **myopic shift** due to lens swelling, while sudden lowering of blood sugar can cause a hyperopic shift.

Question 192: Indocyanine green angiography (ICG angiography) is most useful in detecting which of the following conditions?

A. Occult choroidal neovascularization (Occult CNV) (Correct Answer)
B. Classic choroidal neovascularization (Classic CNV)
C. Angioid streaks with choroidal neovascularization (CNV)
D. Polypoidal choroidal vasculopathy

Explanation: **Explanation:** Indocyanine Green Angiography (ICGA) is superior to Fluorescein Angiography (FFA) for imaging the **choroidal circulation**. This is due to two primary properties of ICG dye: it is 98% protein-bound (remaining within the choroidal vessels) and it emits near-infrared fluorescence, which penetrates the retinal pigment epithelium (RPE), exudates, and thin hemorrhages more effectively than the visible light used in FFA. **1. Why Occult CNV is the correct answer:** In **Occult Choroidal Neovascularization**, the neovascular membrane is located beneath the RPE or is obscured by blood/exudate. On FFA, these lesions appear as "stippled hyperfluorescence" or "leakage of undetermined source," making the boundaries poorly defined. Because ICG dye penetrates the RPE and stays intravascular, it can pinpoint the exact location and extent of these "hidden" membranes, appearing as a "hot spot" or a "plaque." **2. Analysis of other options:** * **Classic CNV:** These membranes are above the RPE. They are well-delineated and easily identified on **FFA** (showing early lacy hyperfluorescence). While ICG can see them, FFA remains the gold standard for classic lesions. * **Angioid Streaks with CNV:** While ICG can be used, the primary diagnosis of angioid streaks is clinical/FFA. The question asks where ICG is *most* useful/indicated; occult CNV is the classic indication. * **Polypoidal Choroidal Vasculopathy (PCV):** While ICG is indeed the gold standard for PCV, in the context of standard NEET-PG questions regarding "Occult CNV vs. Classic CNV," ICG’s primary historical and clinical utility is defined by its ability to unmask occult membranes. **Clinical Pearls for NEET-PG:** * **FFA Dye:** Sodium Fluorescein (80% protein-bound); best for **retinal** vessels. * **ICG Dye:** Indocyanine Green (98% protein-bound); best for **choroidal** vessels. * **Contraindication:** Avoid ICG in patients with **iodine or shellfish allergy**, as the dye contains iodine. * **High-Yield:** ICG is the investigation of choice for **PCV** and **Occult CNV**.

Question 193: All of the following are true for medullated nerve fibers of the retina except:

A. Appear as a whitish patch usually present around the disc
B. Are commonly seen at birth in premature children (Correct Answer)
C. Disappear in patients with optic atrophy
D. May cause enlargement of the blind spot

Explanation: **Explanation** Medullated (myelinated) nerve fibers are a benign congenital anomaly where the myelination of the optic nerve, which normally stops at the lamina cribrosa, extends onto the retinal nerve fiber layer. **Why Option B is the Correct Answer (The False Statement):** Myelination of the optic nerve proceeds from the chiasm toward the eye and typically reaches the lamina cribrosa at birth. Therefore, medullated nerve fibers are **rarely present at birth**; they usually develop postnatally during the first few weeks of life. They are not specifically associated with prematurity. **Analysis of Other Options:** * **Option A:** They appear as **striated, feather-edged white patches** (due to the arrangement of the nerve fiber layer) and are most commonly found adjacent to the optic disc. * **Option C:** Since myelin is maintained by the presence of intact axons, any condition causing **optic atrophy** (death of the axons) will lead to the disappearance of the medullated appearance. * **Option D:** Because the thick layer of myelin is opaque, it can block light from reaching the underlying photoreceptors, leading to a scotoma or **enlargement of the blind spot** on perimetry. **High-Yield Clinical Pearls for NEET-PG:** * **Appearance:** "Feathery" or "Flame-shaped" white patches with blurred margins that obscure underlying retinal vessels. * **Association:** Most cases are isolated, but they can be associated with **Gorlin-Goltz syndrome**. * **Straatsma Syndrome:** A triad of unilateral medullated nerve fibers, high myopia, and amblyopia. * **Differential Diagnosis:** Must be distinguished from cotton wool spots (which are smaller and transient) and retinoblastoma.

Question 194: All of the following are causes of night blindness EXCEPT:

A. Oguchi's disease
B. Vitamin A deficiency
C. High myopia
D. Devic's disease (Correct Answer)

Explanation: **Explanation:** **Night blindness (Nyctalopia)** occurs due to the dysfunction of **rod photoreceptors** or a deficiency in the regeneration of visual purple (rhodopsin). **Why Devic’s Disease is the correct answer:** **Devic’s disease (Neuromyelitis Optica)** is an autoimmune inflammatory disorder characterized by synchronous or successive episodes of **optic neuritis** and transverse myelitis. While it causes significant vision loss (central scotomas or blindness) due to optic nerve involvement, it does **not** specifically target the rod system or cause night blindness. It is a disease of the central nervous system/optic nerve, not the peripheral retina. **Analysis of incorrect options:** * **Oguchi’s Disease:** A rare autosomal recessive form of **Stationary Night Blindness**. It is characterized by the *Mizuo-Nakamura phenomenon* (the fundus turns a golden-yellow color in light and reverts to normal after prolonged dark adaptation). * **Vitamin A Deficiency:** The most common cause of acquired night blindness. Vitamin A is a precursor to **11-cis-retinal**, which combines with opsin to form rhodopsin in the rods. * **High Myopia:** Pathological myopia leads to degenerative changes in the peripheral retina and choriocapillaris (chorioretinal degeneration), which can impair rod function and lead to night blindness. **High-Yield Clinical Pearls for NEET-PG:** * **Retinitis Pigmentosa** is the most common hereditary cause of night blindness. * **Other causes:** Gyrate atrophy, Choroideremia, Vitamin A deficiency (X1A stage), and Zinc deficiency. * **Mizuo-Nakamura Phenomenon:** Pathognomonic for Oguchi's disease. * **Devic’s Disease Marker:** Highly specific **NMO-IgG (Aquaporin-4 antibody)**.

Question 195: On fundoscopic examination of a patient with a history of sudden and painless loss of vision two days prior, the surgeon finds an orange reflex and segmentation of blood column in the vessels. What are these vessels and what condition has the patient suffered from?

A. Retinal arteries and Central Retinal Artery occlusion
B. Retinal veins and Central Retinal Artery occlusion (Correct Answer)
C. Retinal veins and Central Retinal Vein occlusion
D. Retinal arteries and Central Retinal Vein occlusion

Explanation: ### Explanation **Correct Answer: B. Retinal veins and Central Retinal Artery occlusion** #### 1. Understanding the Clinical Presentation The patient presents with **sudden, painless loss of vision**, which is the classic hallmark of **Central Retinal Artery Occlusion (CRAO)**. In CRAO, the cessation of arterial blood flow leads to severe retinal ischemia. The "orange reflex" mentioned refers to the **Cherry Red Spot**. This occurs because the fovea is thin and lacks the inner retinal layers that become opaque and milky-white due to edema; thus, the underlying vascular choroid (orange-red) shines through. The **segmentation of the blood column** (also known as "cattle-tracking" or "box-carring") is a critical diagnostic sign. It occurs due to the stasis of blood flow. Interestingly, while the primary pathology is arterial, this segmentation is most prominently visible in the **retinal veins**, as the sluggish flow leads to the separation of RBC clumps and serum within the venous system. #### 2. Why Other Options are Incorrect * **Option A:** While CRAO is the correct diagnosis, the segmentation (cattle-tracking) is a classic description associated with the venous column in late-stage or complete arterial obstruction. * **Options C & D:** **Central Retinal Vein Occlusion (CRVO)** typically presents with a "Blood and Thunder" fundus (extensive flame-shaped hemorrhages, dilated tortuous veins, and disc edema). It does not present with a cherry red spot or cattle-tracking. #### 3. NEET-PG High-Yield Pearls * **Cherry Red Spot Differential:** CRAO, Tay-Sachs disease, Niemann-Pick disease, Gaucher’s disease, and Berlin’s edema (commotio retinae). * **Cattle-tracking:** Indicates a very poor prognosis and signifies nearly total cessation of retinal blood flow. * **Immediate Management:** CRAO is an ocular emergency. Treatment includes digital ocular massage, anterior chamber paracentesis, and inhalation of Carbogen (95% $O_2$, 5% $CO_2$) to induce vasodilation and dislodge the embolus. * **Cilioretinal Artery:** In 15-20% of the population, this artery (derived from ciliary circulation) spares the macula, preserving central vision despite CRAO.

Question 196: Sudden painless loss of vision is typically seen in retinal detachment due to which of the following conditions?

A. Iridocyclitis
B. Chorioretinitis
C. Vitreous hemorrhage (Correct Answer)
D. Diabetic retinopathy

Explanation: ### Explanation **Correct Option: C. Vitreous hemorrhage** **Medical Concept:** Sudden, painless loss of vision is a classic ophthalmic emergency. In the context of retinal detachment (RD), specifically **Rhegmatogenous RD**, the mechanical tear in the retina often involves a retinal vessel, leading to an associated **vitreous hemorrhage**. The presence of blood in the vitreous cavity prevents light from reaching the retina, resulting in an immediate and profound drop in visual acuity. While the detachment itself causes a field defect (often described as a "curtain falling"), the sudden "blackout" or "floaters followed by vision loss" is typically due to the hemorrhage. **Analysis of Incorrect Options:** * **A. Iridocyclitis:** This is an anterior uveitis. It typically presents with **pain**, photophobia, and redness (ciliary congestion), rather than sudden painless vision loss. * **B. Chorioretinitis:** This is a form of posterior uveitis. While it can cause vision loss, it is usually **gradual or subacute** and associated with "floaters" or blurred vision rather than a sudden, total loss. * **D. Diabetic Retinopathy:** While advanced Proliferative Diabetic Retinopathy (PDR) is a leading cause of vitreous hemorrhage and tractional RD, the disease itself is a **chronic, progressive condition**. The sudden loss of vision in a diabetic patient is usually a *complication* (like vitreous hemorrhage), not the retinopathy itself. **NEET-PG High-Yield Pearls:** * **Differential Diagnosis for Sudden Painless Loss of Vision:** 1. Central Retinal Artery Occlusion (CRAO) – "Cherry red spot." 2. Central Retinal Vein Occlusion (CRVO) – "Blood and thunder fundus." 3. Vitreous Hemorrhage – "Absent red reflex." 4. Retinal Detachment – "Fresh-looking greyish reflex/folds." * **Clinical Sign:** In vitreous hemorrhage, the red reflex is often absent or dull, and the fundus details are obscured during ophthalmoscopy. B-Scan ultrasonography is the investigation of choice to rule out underlying RD when the media is opaque.

Question 197: What is the earliest symptom of retinitis pigmentosa?

A. Ring scotoma
B. Nyctalopia (Correct Answer)
C. Tubular vision
D. None

Explanation: **Explanation:** **Retinitis Pigmentosa (RP)** is a hereditary, progressive dystrophy primarily affecting the photoreceptors and the retinal pigment epithelium (RPE). **Why Nyctalopia is the correct answer:** The hallmark of RP is the **predominant involvement of rods** before cones. Rods are responsible for vision in dim light (scotopic vision) and are concentrated in the mid-periphery of the retina. Since rods are the first to degenerate, the **earliest clinical symptom** reported by patients is **Nyctalopia (night blindness)**, often occurring years before visible changes appear on fundoscopy. **Analysis of Incorrect Options:** * **Ring Scotoma (Option A):** This is the earliest **visual field defect (sign)**, not the earliest symptom. It corresponds to the degeneration of rods in the mid-peripheral "equatorial" zone (30–50 degrees from the fixation point). * **Tubular Vision (Option B):** This is a **late-stage manifestation**. As the disease progresses centripetally, the ring scotoma expands, leaving only a small central island of vision (tunnel vision). * **None (Option D):** Incorrect, as Nyctalopia is the classic presenting symptom. **High-Yield Clinical Pearls for NEET-PG:** * **Inheritance:** Most common is Autosomal Recessive; most severe is X-linked. * **Classic Triad (Fundus):** 1. Bony spicule pigmentation (perivascular), 2. Arteriolar attenuation (narrowing), 3. Waxy pallor of the optic disc. * **Electroretinogram (ERG):** The most sensitive test for early diagnosis. The **scotopic ERG** is reduced or abolished early in the disease. * **Associated Syndromes:** **Usher Syndrome** (RP + Sensorineural hearing loss) and **Refsum Disease** (RP + Peripheral neuropathy + Ataxia; treatable by restricting phytanic acid).

Question 198: What is the earliest pathological change in diabetic retinopathy?

A. Hyaloid changes
B. Hard exudates
C. Microaneurysms and pinpoint hemorrhages (Correct Answer)
D. Vitreous hemorrhage

Explanation: ### Explanation **Correct Answer: C. Microaneurysms and pinpoint hemorrhages** **Pathophysiology:** The earliest clinical sign of diabetic retinopathy is the formation of **microaneurysms**. The fundamental pathological process begins with the **loss of pericytes** (cells that support the capillary walls) and thickening of the capillary basement membrane. This weakens the capillary wall, leading to focal saccular outpouchings known as microaneurysms. These appear as tiny, round, red dots on fundoscopy. Pinpoint hemorrhages often occur simultaneously due to the rupture of these weakened capillaries or microaneurysms. **Analysis of Incorrect Options:** * **A. Hyaloid changes:** These are late-stage changes associated with Proliferative Diabetic Retinopathy (PDR). They involve the posterior hyaloid membrane and are related to vitreous detachment or traction, occurring long after microvascular damage. * **B. Hard exudates:** These are composed of lipoprotein and lipid-filled macrophages. They occur due to chronic leakage from weakened vessels but typically appear *after* the initial formation of microaneurysms. * **D. Vitreous hemorrhage:** This is a severe, late-stage complication of PDR. It occurs when new, fragile vessels (neovascularization) bleed into the vitreous cavity, leading to sudden vision loss. **NEET-PG High-Yield Pearls:** * **Earliest Clinical Sign:** Microaneurysms (found in the inner nuclear layer). * **Earliest Pathological Change:** Loss of pericytes (Pericyte:Endothelial cell ratio changes from 1:1 to 1:0). * **First Sign on FFA:** Microaneurysms appear as "hyperfluorescent dots." * **Classification:** Microaneurysms are the hallmark of **Very Mild Non-Proliferative Diabetic Retinopathy (NPDR)**. * **Cotton Wool Spots:** Represent focal ischemia in the nerve fiber layer (not an early sign).

Question 199: In retinal artery angiogram, through which vessel is the dye typically injected?

A. Peripheral veins (Correct Answer)
B. Aorta
C. Retinal artery
D. Retinal vein

Explanation: **Explanation:** The question refers to **Fundus Fluorescein Angiography (FFA)**, a gold-standard diagnostic procedure used to visualize the retinal and choroidal circulation. **Why Peripheral Veins is Correct:** In FFA, a water-soluble dye called **Sodium Fluorescein (5ml of 10% or 3ml of 25%)** is injected into a **peripheral vein**, typically the **antecubital vein** in the arm. The dye follows the systemic circulation: it travels from the peripheral vein to the right heart, through the lungs, to the left heart, and then via the aorta and carotid arteries to reach the ophthalmic artery and finally the retinal/choroidal vessels. This route is preferred because it is minimally invasive, safe, and allows for the study of the "arm-to-retina" circulation time (normally 10–15 seconds). **Why Other Options are Incorrect:** * **Aorta:** Injecting into the aorta would require an invasive arterial catheterization (similar to cardiac angiography), which is unnecessary and carries high risks for a diagnostic eye procedure. * **Retinal Artery:** Direct injection into the retinal artery is anatomically impossible without highly invasive intra-arterial surgery and would likely cause permanent vascular damage or blindness. * **Retinal Vein:** The retinal veins are the "exit" vessels of the eye. Injecting here would not allow for the visualization of the arterial filling phases, which are crucial for diagnosis. **High-Yield Clinical Pearls for NEET-PG:** * **Dye used:** Sodium Fluorescein (excitation peak: 490 nm; emission peak: 530 nm). * **Side Effects:** Nausea (most common), yellowish skin/urine discoloration (transient), and rarely, anaphylaxis. * **Contraindications:** History of severe allergic reaction to the dye; use with caution in patients with severe renal failure. * **Phases of FFA:** Pre-arterial (Choroidal flush) → Arterial → Arteriovenous (Capillary) → Venous → Recirculation/Late phase.

Question 200: What is the most common organism causing chorioretinitis in HIV patients?

A. Cytomegalovirus (CMV) retinitis (Correct Answer)
B. Toxoplasma chorioretinitis
C. Syphilitic retinitis
D. Pneumocystis jirovecii pneumonia (PCP)

Explanation: **Explanation:** **1. Why CMV Retinitis is the Correct Answer:** Cytomegalovirus (CMV) is the most common opportunistic ocular infection in patients with HIV/AIDS, typically occurring when the **CD4+ T-cell count falls below 50 cells/µL**. It is a necrotizing retinitis that spreads through the retina, leading to irreversible vision loss if untreated. It classically presents in two forms: the **"Pizza-pie" or "Cottage cheese and ketchup" appearance** (hemorrhagic necrosis) and the **"Brushfire" border** (granular white opacification). **2. Why the Other Options are Incorrect:** * **Toxoplasma chorioretinitis:** While *Toxoplasma gondii* is a common cause of posterior uveitis in the general population and can occur in HIV patients, it is less frequent than CMV. In HIV, it often presents as multifocal lesions and is usually associated with CNS toxoplasmosis. * **Syphilitic retinitis:** Known as "The Great Imitator," syphilis can cause various forms of uveitis in HIV patients. While its incidence is rising, it remains less common than CMV as a primary opportunistic retinal infection. * **Pneumocystis jirovecii:** While PCP is a leading cause of pneumonia in AIDS, its ocular manifestation (choroiditis) is relatively rare and typically occurs in patients receiving aerosolized pentamidine without systemic prophylaxis. **3. NEET-PG High-Yield Clinical Pearls:** * **CD4 Threshold:** Always look for a CD4 count **<50 cells/µL** in the clinical stem for CMV. * **Drug of Choice:** **Ganciclovir** (Intravenous or intravitreal) or Valganciclovir (Oral). * **Complication:** The most common cause of vision loss in CMV retinitis is **Rhegmatogenous Retinal Detachment**. * **Differential:** Unlike CMV, **Progressive Outer Retinal Necrosis (PORN)** caused by VZV presents with rapid progression and minimal inflammation/hemorrhage.

Practice by Chapter

Retinal Anatomy and Physiology

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Age-Related Macular Degeneration

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Diabetic Retinopathy

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Retinal Vascular Diseases

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Retinal Detachment

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Hereditary Retinal Dystrophies

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Inflammatory Retinal Diseases

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Retinal Tumors

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Retinopathy of Prematurity

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Retinal Imaging Techniques

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Intravitreal Pharmacotherapy

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Vitreoretinal Surgery

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