Iridocorneal Angle and Anterior Chamber Architecture after Laser Iridotomy or Pilocarpine in Anatomically Narrow Angles

Abstract

 

Purpose

 

To compare the effects of laser iridotomy (LI) and pilocarpine on the iridocorneal angle and anterior chamber structures in anatomically narrow angles (ANA).

 

Methods

 

Patients with ANA but no ocular hypertension, glaucoma or prior ocular surgery were enrolled. Temporal LI was performed 1 hr after pilocarpine 2% administration. Horizontal and vertical swept-source optical coherence tomography (OCT) (Casia SS-1000; Tomey, Inc., Nagoya, Japan) B-scans of the anterior segment were obtained at baseline, 30 minutes after pilocarpine 2%, and 1 week after LI, in a standardized dark room. Angle opening distance (AOD), angle recess area (ARA), trabecular-iris surface area (TISA) and trabecular-iris angle (TIA) were measured at the superior, inferior, nasal and temporal quadrants (Fig 1). Anterior chamber depth (ACD) and lens vault (LV) were measured in the horizontal and vertical scans, and the 2 values were averaged to generate a mean value.

 

Results

 

10 eyes (10 subjects; mean age, 55±12 years; mean intraocular pressure, 14.2±3.5 mmHg) were included. All horizontal scans were ~1-2 mm away from the LI site. Mean AOD, ARA, TISA and TIA of the 4 quadrants increased from baseline after pilocarpine and after LI (baseline vs. post-pilocarpine, all p<0.036; baseline vs. post-LI, all p<0.001), but the increase was greater after LI than after pilocarpine although statistically insignificant (post-pilocarpine vs. post-LI, all p>0.200) (Table 1). In the temporal quadrant, mean AOD, ARA, TISA and TIA increased from baseline after piloparpine and after LI (baseline vs. post-pilocarpine, all p<0.043; baseline vs. post-LI, all p<0.001), but the increase was significantly greater after LI than after pilocarpine (post-pilocarpine vs. post-LI, all p<0.019) (Table 1). In the superior, inferior and nasal quadrants, all angle parameters were similar between post-pilocarpine and post-LI (all p>0.106). ACD decreased and LV increased after pilocarpine from baseline (all p<0.012) but vice versa after LI (all p>0.108). Post-pilocarpine anterior chambers were significantly shallower with greater LV than post-LI anterior chambers (all p<0.010) (Table 1).

 

Conclusions

 

LI may be more effective than pilocarpine in widening the iridocorneal angles and deepening the anterior chamber in ANA. Near the LI site, the angles are wider post-LI than post-pilocarpine, possibly because of iris contraction from laser burns.