What Are the Characteristics of Primary Angle Closure With Longer Axial Length?

Purpose: To compare biometric parameters between primary angle closure with longer axial length (AL) and those with medium or shorter AL.

Methods: We prospectively recruited 138 primary angle-closure patients. Low-coherence interferometry and ultrasound biomicroscopy examinations were performed before laser peripheral iridotomy and pilocarpine treatment. AL was categorized as shorter (<22.5 mm), medium (≥22.5 to <23.5 mm), or longer (≥23.5 mm). Anterior chamber depth and width (ACD and ACW), lens vault (LV), anterior vault (AV), relative AV (AV/AL), relative lens position (RLP, [ACD + 1/2 lens thickness]/AL), trabecular-ciliary angle (TCA), keratometry, and other biometric parameters were compared among different AL groups.

Results: Among 138 angle-closure patients, 15 (10.9%) patients had longer ALs, of which 11 (73.3%) were male. These angle-closure eyes with longer AL had flatter cornea (P = 0.006 and 0.022 for flat and steep keratometry) and larger ACW (P = 0.006), but smaller RLP (P = 0.019) than those with medium AL; similarly, they had flatter cornea (P < 0.001 for both flat and steep keratometry), and larger ACW (P < 0.001), AV (P = 0.004), and TCA (P = 0.024), but smaller relative AV (P = 0.040) and RLP (P = 0.005) than those with shorter AL. No significant differences were found in the other parameters.

Conclusions: Primary angle closure with longer AL was uncommon. Causes of angle closure in these atypical patients were manifold. These patients were predominantly male; they had smaller relative dimension of the anterior segment, flatter cornea, and more anterior RLP and less anteriorly rotated ciliary body compared with those angle-closure patients with relatively shorter AL.