A 58-year-old myopic man presents with sudden onset of floaters, photopsia, and a progressive curtain-like visual field defect over 3 days. Dilated fundoscopy reveals a corrugated, mobile retinal elevation with loss of the underlying choroidal pattern and tobacco dust in the anterior vitreous. The structure marked **C** in the diagram shows a horseshoe tear with a free anterior flap. Which of the following best describes the PRIMARY PATHOPHYSIOLOGICAL MECHANISM underlying this detachment?
A. Separation of the outer retinal layers (photoreceptors) from the inner retinal layers due to cystoid edema and schisis
B. Contraction of epiretinal and subretinal fibrotic membranes exerting tangential traction on an intact retina
C. Full-thickness neurosensory retinal break allowing liquefied vitreous to access the subretinal space and separate the neurosensory retina from the RPE
D. Accumulation of serous fluid beneath the retina due to blood–retinal barrier breakdown without any retinal break
Explanation
Why option 1 is right
The clinical anchor defines rhegmatogenous retinal detachment (RRD) as caused by a full-thickness neurosensory retinal break that permits liquefied vitreous to enter the subretinal space, mechanically separating the neurosensory retina from the underlying retinal pigment epithelium (RPE). The horseshoe tear marked C is the pathognomonic break—a U-shaped defect with a free anterior flap created by vitreoretinal traction during posterior vitreous detachment (PVD). The patient's classic symptom triad (floaters, photopsias from retinal traction, and progressive visual field loss) and the examination findings (corrugated mobile elevation, loss of choroidal pattern, Shafer's sign) are all consistent with this mechanism. This is the most common form of retinal detachment and a true ophthalmic emergency.
Why each distractor is wrong
Option 2 (Exudative detachment): Describes accumulation of serous fluid without a retinal break—the hallmark of exudative detachment (seen in Coats disease, VKH, or other inflammatory/vascular conditions). The presence of a horseshoe tear and tobacco dust explicitly rules out this mechanism.
Option 3 (Tractional detachment): Describes contraction of fibrotic membranes (epiretinal and subretinal) exerting traction on an intact retina—the mechanism of tractional detachment in proliferative diabetic retinopathy (PDR) and advanced PVR. The horseshoe tear indicates a break, not pure traction.
Option 4 (Retinoschisis): Describes separation of outer from inner retinal layers due to cystoid edema—the mechanism of retinoschisis (smooth, dome-shaped, typically asymptomatic). The presence of a full-thickness break, acute symptoms, and mobile elevation distinguish RRD from retinoschisis.
High-YieldNEET PG
RRD = full-thickness break + liquefied vitreous in subretinal space; the horseshoe tear is created by vitreoretinal traction during PVD and is a true emergency requiring repair within 24 hours if macula is involved.
AAO BCSC Section 12 — Retina and Vitreous 2023
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