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.