Which clinical feature best distinguishes rhegmatogenous retinal detachment from tractional retinal detachment?

Explanation

## Distinguishing Rhegmatogenous from Tractional Retinal Detachment ### Key Pathophysiologic Difference **Key Point:** The defining feature of rhegmatogenous retinal detachment (RRD) is the presence of a **full-thickness break (hole or tear)** in the neurosensory retina, allowing liquefied vitreous to seep into the subretinal space and separate the retina from the RPE. Tractional retinal detachment (TRD) occurs without any break — the retina is mechanically pulled off by fibroglial scar tissue contraction. ### Comparative Features Table | Feature | Rhegmatogenous RD | Tractional RD | |---------|-------------------|---------------| | **Full-thickness break** | **Yes (defining)** | No | | Retinal appearance | Convex (bulging inward) | Concave (pulled inward) | | Vitreous involvement | Liquefied vitreous enters subretinal space | Vitreous traction without break | | PVR association | Common (secondary complication) | Can occur but not primary cause | | Progression rate | Rapid (days to weeks) | Slow (weeks to months) | | Common causes | Myopia, lattice degeneration, trauma | Diabetes, sickle cell, ROP | ### Clinical Pearl **Clinical Pearl:** The **convex vs. concave appearance** is a useful bedside discriminator: RRD appears convex (bulging toward vitreous) because gravity and vitreous pressure push the detached retina inward; TRD appears concave (pulled outward) because scar tissue contracts and drags the retina toward the scar. ### High-Yield Point **High-Yield:** On indirect ophthalmoscopy or B-scan ultrasound, RRD shows a **convex or dome-shaped** detachment; TRD shows a **concave or funnel-shaped** detachment. However, the **pathognomonic feature** that definitively distinguishes RRD is the presence of a retinal break visible on examination. ### Why the Correct Answer Stands The full-thickness break is the **sine qua non** of RRD — it is the mechanism by which vitreous gains access to the subretinal space. Without a break, the condition is by definition not rhegmatogenous. This is the most specific and diagnostically decisive feature. [cite:Yanoff & Duker Ophthalmology 5e Ch 6.7]