A 45-year-old myopic man presents with sudden onset of floaters and photopsia in his right eye. On dilated fundus examination with scleral depression, the structure marked **B** is identified. Which of the following best describes the pathophysiological mechanism by which this finding leads to rhegmatogenous retinal detachment?

Explanation

## Why "Vitreous fluid enters the subretinal space through the break, separating the neurosensory retina from the retinal pigment epithelium" is right The structure marked **B** is a horseshoe retinal tear — the classic break in rhegmatogenous retinal detachment (RD). The defining pathophysiology of rhegmatogenous RD is that vitreous fluid gains access to the subretinal space through a retinal break (tear or hole), creating a separation between the neurosensory retina and the underlying retinal pigment epithelium (RPE). This is the most common form of RD (~80% of cases) and is the direct consequence of the tear marked **B**. The horseshoe tear, with its operculum still attached, is a particularly common and clinically significant break that initiates this fluid-driven detachment. (AK Khurana 7e) ## Why each distractor is wrong - **Fibrovascular membranes mechanically pull the retina away from the underlying choroid**: This describes tractional retinal detachment, which occurs in proliferative diabetic retinopathy, retinopathy of prematurity, and post-traumatic cases — NOT the mechanism of rhegmatogenous RD caused by a horseshoe tear. - **Fluid leaks into the subretinal space from the choroid without any break in the retina**: This describes exudative (serous) retinal detachment, seen in choroidal tumors, Coats disease, and severe hypertension — there is NO retinal break involved, which contradicts the presence of the tear marked **B**. - **Posterior vitreous detachment causes traction on the macula, leading to central visual loss**: While PVD is a risk factor for retinal tears, this option describes a traction mechanism and focuses on macular involvement rather than the fundamental pathophysiology of how a horseshoe tear causes RD. **High-Yield:** Rhegmatogenous RD = retinal break (tear/hole) → vitreous fluid enters subretinal space → neurosensory retina separates from RPE. Horseshoe tears are the most common break type and are sight-threatening emergencies requiring urgent intervention. [cite: AK Khurana 7e — Retinal Detachment classification and pathophysiology]