Diseases of the Retina Practice Questions

Q: What is true about electroretinogram?

The 'c' wave is a positive wave.. ### Explanation: Electroretinogram (ERG) The Electroretinogram (ERG) is a diagnostic test that measures the electrical response of various layers of the retina to a light stimulus. **1. Why Option D is Correct:** The **'c' wave** is a slow, **positive** deflection that follows the 'b' wave. It represents the metabolic activity and electrical response of the **Retinal Pigment Epithelium (RPE)** in conjunction with the photoreceptors. **2. Analysis of Incorrect Options:** * **Option A:** The **'a' wave** is the first component of the ERG and is a **negative** wave (downward deflection). * **Option B:** The 'a' wave arises from the **photoreceptors** (rods and cones), not the RPE. It reflects the initial hyperpolarization of these cells. * **Option C:** The **'b' wave** is a large positive wave that arises from the **inner retinal layers**, specifically the **Müller cells and Bipolar cells**. It does not arise directly from the rods and cones. **3. High-Yield Clinical Pearls for NEET-PG:** * **Components Summary:** * **'a' wave:** Negative; Photoreceptors. * **'b' wave:** Positive; Bipolar/Müller cells (Largest component). * **'c' wave:** Positive; Retinal Pigment Epithelium (RPE). * **'d' wave:** Reflects the "off-response" of the retina. * **Clinical Utility:** ERG is most useful in diagnosing **Retinitis Pigmentosa** (where the ERG is typically "extinguished" or subnormal even before visual field loss occurs). * **Negative ERG:** A condition where the 'a' wave is preserved but the 'b' wave is lost (seen in Central Retinal Artery Occlusion and Congenital Stationary Night Blindness). * **EOG (Electro-oculogram):** Specifically tests RPE function (Arden Index < 1.5 is abnormal); it is the gold standard for **Best’s Disease**.

Q: Which of the following conditions is characterized by a "brush fire" appearance of the fundus?

CMV retinitis. **Explanation:** **CMV Retinitis (Correct Answer):** Cytomegalovirus (CMV) retinitis is the most common opportunistic ocular infection in patients with AIDS (typically when CD4 counts are <50 cells/µL). The "brush fire" appearance refers to the characteristic fundus finding of **fulminant necrosis** spreading peripherally, featuring a leading edge of white opacified retina (necrosis) associated with prominent intraretinal hemorrhages. This is also famously described as the **"Pizza-pie"** or **"Tomato-catsup"** appearance. **Analysis of Incorrect Options:** * **Toxoplasmosis:** Characterized by a "Headlight in the fog" appearance, which represents an active focus of yellow-white chorioretinitis seen through a hazy, vitreous inflammatory reaction (vitritis). * **Chloroquine Toxicity:** Classically presents with a **"Bull’s eye maculopathy"** due to a ring of retinal pigment epithelium (RPE) atrophy surrounding a central spared foveal area. * **Bacterial Endocarditis:** Associated with **Roth spots**, which are retinal hemorrhages with a central white/pale spot (representing fibrin-platelet plugs). **NEET-PG High-Yield Pearls:** * **Drug of Choice:** Ganciclovir (Intravenous or Intravitreal) is the first-line treatment for CMV retinitis. Foscarnet and Cidofovir are alternatives. * **Frosted Branch Angiitis:** Another presentation of CMV retinitis characterized by severe perivascular sheathing. * **Immune Recovery Uveitis (IRU):** A paradoxical inflammatory response seen in CMV patients after starting HAART as their CD4 count improves. * **Differentiating Feature:** Unlike Toxoplasmosis, CMV retinitis typically presents with **minimal vitritis** ("cold" inflammation) because the patient is severely immunocompromised.

Q: Visual loss in diabetic retinopathy is due to all except?

Background diabetic retinopathy. **Explanation:** The primary goal of this question is to distinguish between the stages of diabetic retinopathy (DR) that cause significant visual impairment versus those that are typically asymptomatic. **Why "Background Diabetic Retinopathy" is the correct answer:** Background Diabetic Retinopathy (BDR) is the earliest clinical stage of DR. It is characterized by microaneurysms, dot-and-blot hemorrhages, and hard exudates. In this stage, the lesions are confined to the retina and do not involve the fovea. Therefore, BDR is generally **asymptomatic** and does not cause vision loss unless it progresses to Diabetic Macular Edema (DME). **Analysis of Incorrect Options (Causes of Vision Loss):** * **Cataract formation:** Diabetes accelerates metabolic changes in the lens (e.g., sorbitol accumulation), leading to "Snowflake cataracts" or early-onset senile cataracts, both of which cause painless, progressive vision loss. * **Ischaemic maculopathy:** This occurs due to the closure of retinal capillaries at the fovea (foveal avascular zone enlargement). It is a major cause of irreversible central vision loss in diabetics and carries a poor prognosis. * **Vitreous hemorrhage:** A hallmark of Proliferative Diabetic Retinopathy (PDR). New vessels (neovascularization) are fragile and bleed into the vitreous cavity, causing sudden, painless floaters or total vision loss. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of legal blindness** in DR: Diabetic Macular Edema (DME). * **Most common cause of sudden vision loss** in DR: Vitreous hemorrhage. * **Earliest clinical sign** of DR: Microaneurysms. * **Earliest functional change** in DR: Loss of blue-yellow color vision and altered Contrast Sensitivity. * **Investigation of choice** for Macular Edema: Optical Coherence Tomography (OCT). * **Investigation of choice** for Macular Ischemia: Fundus Fluorescein Angiography (FFA).

Q: Which of the following is the commonest infectious cause for posterior uveitis?

Toxoplasma gondii. **Explanation:** **Toxoplasma gondii** is the most common cause of infectious posterior uveitis worldwide. It typically presents as a **focal necrotizing retinochoroiditis**. The infection can be congenital or acquired. In most cases, it occurs due to the reactivation of a latent cyst in a previous scar, leading to the classic **"Headlight in the fog"** appearance (an active creamy-white lesion adjacent to an old pigmented chorioretinal scar, seen through a hazy vitreous). **Analysis of Incorrect Options:** * **Toxocara (Option A):** While *Toxocara canis* causes ocular larva migrans, it typically presents as a unilateral solitary posterior pole granuloma or endophthalmitis in children, rather than being the most common cause of posterior uveitis. * **Taenia solium (Option B):** This causes **Cysticercosis**. In the eye, the cyst is most commonly found in the subretinal space or vitreous, but it is a parasitic infestation rather than a primary cause of diffuse infectious uveitis. * **Plasmodium falciparum (Option D):** Malaria primarily affects the systemic vasculature. Ocular involvement (Malarial retinopathy) involves hemorrhages and vessel whitening but is not a standard cause of posterior uveitis. **High-Yield Clinical Pearls for NEET-PG:** * **Primary site of infection:** In Toxoplasmosis, the primary site is the **retina** (Retinitis), and the choroid is involved secondarily. * **Treatment of choice:** Triple therapy (Sulfadiazine + Pyrimethamine + Folinic acid) or Clindamycin. * **Steroids:** Always used in conjunction with anti-parasitic drugs, never alone, to prevent rapid multiplication of the organism. * **Differential Diagnosis:** CMV Retinitis (commonest in HIV/AIDS patients, characterized by "Pizza-pie" or "Cheese and Ketchup" fundus).

Q: Which of the following is characteristic of Chloroquine retinopathy?

Progression of retinopathy after cessation of medication. **Explanation:** Chloroquine (CQ) and Hydroxychloroquine (HCQ) are known for their affinity for melanin-containing tissues, particularly the **Retinal Pigment Epithelium (RPE)**. **Why Option C is correct:** The hallmark of Chloroquine toxicity is its **long half-life** and its tendency to accumulate in the RPE. Even after the medication is discontinued, the drug remains stored in the ocular tissues for years. This leads to a phenomenon where the retinopathy continues to worsen or progress even after cessation of the drug. This is a critical clinical point for monitoring patients. **Why other options are incorrect:** * **Option A:** Chloroquine is not exclusively retinotoxic. It is associated with various CNS side effects, including headaches, seizures, and even toxic psychosis. It can also cause neuromuscular weakness and ototoxicity. * **Option B:** Chloroquine retinopathy is **irreversible**. Once the classic "Bull’s Eye Maculopathy" (a ring of depigmentation surrounded by a ring of hyperpigmentation) develops, the vision loss is permanent because the damage to the RPE and photoreceptors cannot be undone. **High-Yield Clinical Pearls for NEET-PG:** * **Earliest Sign:** The earliest clinical sign is a fine granular pigmentary change in the macula. * **Earliest Functional Change:** Decreased foveal reflex and a **paracentral scotoma** (detected on 10-2 Humphrey Visual Field testing). * **Screening Gold Standard:** SD-OCT (Spectral Domain Optical Coherence Tomography) showing the "Flying Saucer Sign" (loss of the ellipsoid zone in the parafovea). * **Safe Dosage:** To minimize risk, the daily dose should not exceed **2.3 mg/kg** for Chloroquine and **5.0 mg/kg** for Hydroxychloroquine.

Q: Subretinal demarcation lines indicate:

Old rhegmatogenous retinal detachment. **Explanation:** **Subretinal demarcation lines** (also known as "high-water marks") are a hallmark clinical sign of a **chronic or old rhegmatogenous retinal detachment (RRD)**. When a retinal detachment remains stationary for several weeks (usually 3 months or more), a reactive proliferation of the Retinal Pigment Epithelium (RPE) occurs at the junction of the detached and attached retina. This leads to the formation of a pigmented or white line on the subretinal surface. These lines indicate that the detachment has been present long enough for the eye to attempt to "wall off" the fluid. **Analysis of Options:** * **A. Fresh RRD:** In acute cases, the retina appears mobile, translucent, and convex with loss of underlying choroidal detail. There has not been sufficient time for RPE proliferation or demarcation line formation. * **C. Retinopathy of Prematurity (ROP):** This is characterized by peripheral vascular non-perfusion and a "demarcation line" or "ridge" at the **junction of vascular and avascular retina**, but it is an intraretinal/surface fibrovascular change, not a subretinal RPE response. * **D. Retinitis Pigmentosa:** This presents with "bone-spicule" pigmentation, arteriolar attenuation, and waxy disc pallor. It does not typically feature linear subretinal demarcation lines. **High-Yield Clinical Pearls for NEET-PG:** * **Timeframe:** It takes approximately **3 to 6 months** for a demarcation line to form. * **Significance:** Their presence suggests a relatively stable, long-standing detachment and carries a slightly better prognosis for surgical reattachment, though visual recovery depends on macular involvement. * **Other signs of Old RRD:** Secondary intraretinal cysts, retinal thinning (atrophy), and subretinal fibrosis. * **Convexity:** Remember that RRD is typically **convex** toward the vitreous, whereas tractional RD is often concave.

Question 1

What is true about electroretinogram?

Accepted Answer

The 'c' wave is a positive wave.

Answer

The 'a' wave is a positive wave.

Answer

The 'a' wave arises from the pigmented epithelium.

Answer

The 'b' wave arises from the rods and cones.

Question 2

Increased oxygen delivery during prematurity causes all the following EXCEPT:

Accepted Answer

Vasodilation

Answer

Vasoconstriction

Answer

Vaso obliteration

Answer

Neovascularisation

Question 3

Puscher's retinopathy in acute pancreatitis is due to which of the following?

Accepted Answer

Occlusion of the posterior retinal artery with aggregated granulocytes

Answer

Occlusion of ciliary artery with exudation

Answer

Central retinal artery occlusion with cotton wool spots and hemorrhage

Answer

Inflammatory exudates in the retinal vein

Question 4

Which of the following conditions is characterized by a "brush fire" appearance of the fundus?

Accepted Answer

CMV retinitis

Answer

Toxoplasmosis

Answer

Chloroquine toxicity

Answer

Bacterial endocarditis

Question 5

Visual loss in diabetic retinopathy is due to all except?

Accepted Answer

Background diabetic retinopathy

Answer

Cataract formation

Answer

Ischaemic maculopathy

Answer

Vitreous hemorrhage

Question 6

Which of the following is the commonest infectious cause for posterior uveitis?

Accepted Answer

Toxoplasma gondii

Answer

Toxocara

Answer

Taenia solium

Answer

Plasmodium falciparum

Question 7

In a detached retina, what is the usual site of detachment?

Accepted Answer

Between the pigment epithelial layer and the layer of outer segments of rods and cones

Answer

Within the outer plexiform layer

Answer

Within the inner plexiform layer

Answer

Between the inner nuclear layer and the outer nuclear layer

Question 8

Retinal neovascularization is seen in which of the following conditions?

Accepted Answer

Retinitis pigmentosa

Answer

Diabetic retinopathy

Answer

Eale's disease

Answer

Retinopathy of prematurity

Question 9

Which of the following is characteristic of Chloroquine retinopathy?

Accepted Answer

Progression of retinopathy after cessation of medication

Answer

Not associated with other central nervous system reactions

Answer

Vision loss recovers

Answer

All of the above

Question 10

Subretinal demarcation lines indicate:

Accepted Answer

Old rhegmatogenous retinal detachment

Answer

Fresh rhegmatogenous retinal detachment

Answer

Retinopathy of prematurity

Answer

Retinitis pigmentosa

Diseases of the Retina — MCQs

Diseases of the Retina — MCQs

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