A 52-year-old hyperopic woman with a history of intermittent episodes of blurred vision and mild eye discomfort is found on routine examination to have a shallow anterior chamber and narrow angles bilaterally. Intraocular pressure is normal at 16 mmHg. Which feature best distinguishes the chronic asymptomatic stage of primary angle-closure from the acute angle-closure attack?

Explanation

## Chronic Asymptomatic vs. Acute Angle-Closure Attack ### Natural History of Primary Angle-Closure **Key Point:** Primary angle-closure glaucoma progresses through distinct stages: (1) **Anatomically predisposed eye** (narrow angles, shallow AC, no symptoms, normal IOP), (2) **Intermittent/subacute episodes** (transient angle closure, mild symptoms), (3) **Acute attack** (sudden complete angle closure, severe symptoms, markedly elevated IOP), and (4) **Chronic angle-closure** (persistent angle closure, chronic IOP elevation, optic nerve damage). ### Comparison Table: Stages of Primary Angle-Closure | Stage | Gonioscopy | IOP | Symptoms | Anterior Chamber | Pupil | Cornea | |-------|-----------|-----|----------|------------------|-------|--------| | **Predisposed (asymptomatic)** | Narrow angles, appositional closure | Normal (≤21) | None | Shallow | Normal | Clear | | **Intermittent/Subacute** | Intermittent closure | Transiently elevated | Mild blurring, halos (resolves) | Shallow | Normal or mid-dilated | Clear or transient edema | | **Acute Attack** | Complete angle closure | Very high (>40) | Severe pain, halos, vision loss | Shallow | Mid-dilated, non-reactive | Edematous | | **Chronic Angle-Closure** | Synechial closure | Chronically elevated | Variable (may be asymptomatic) | Shallow | Normal or fixed | Clear or hazy | ### Clinical Pearl **Clinical Pearl:** The **asymptomatic predisposed eye** has all the anatomic risk factors (narrow angles, shallow AC, hyperopia, short axial length) but **normal IOP and no symptoms**. The angles are narrow but *not yet closed*. Once an acute attack occurs, the angles become *completely closed*, IOP spikes, and symptoms become severe. The key discriminator is the **functional status of the angle at the time of examination** — open vs. closed. ### High-Yield Distinction **High-Yield:** - **Asymptomatic stage:** Narrow angles on gonioscopy, but angles are still *patent* (not closed), IOP is normal, no symptoms. - **Acute attack:** Angles are *closed* (appositional or synechial), IOP is severely elevated, symptoms are acute and severe. - **Chronic stage:** Angles are *permanently closed* (synechial), IOP is chronically elevated, optic nerve damage may be present. The **best discriminator** is that in the asymptomatic predisposed stage, the angles are narrow but *open* at the time of examination, IOP is normal, and there are no symptoms. In contrast, during an acute attack, the angles are *closed*, IOP is very high, and symptoms are severe. ### Why Other Features Are Not Discriminators Between Stages - **Narrow angles on gonioscopy:** Present in *all* stages (predisposed, intermittent, acute, chronic). This is the anatomic substrate, not a stage discriminator. - **Shallow anterior chamber:** Present in *all* stages. It is the anatomic predisposition, not a stage indicator. - **Hyperopic refractive error and short axial length:** These are *fixed anatomic features* present throughout the natural history. They do not change between stages. **Mnemonic:** **SCAN** — **S**tage discrimination by **C**urrent **A**ngle status and **N**ormal IOP (asymptomatic) vs. closed angle and elevated IOP (acute).