We measured the anterior chamber depth in 20 consecutive phakic glaucoma patients undergoing thermal sclerostomy (n = 12) or trabeculectomy (n = 8). Using the Haag-Streit pachymeter, measurements were taken preoperatively and at postoperative days 1, 2, 3, 6, 15, and 42. In all eyes, shallowing of the anterior chamber was observed following surgery. It was greatest by postoperative day 2 or 3, with maximum mean decreases from preoperative anterior chamber depths of 70.9% for thermal sclerostomy and 54.0% for trabeculectomy. In 18 patients, the anterior chamber depth gradually deepened over the course of postoperative days 4 through 15, so that by 15 days after surgery, the average anterior chamber depth was 87.6% of the preoperative level. In two patients who ultimately required surgical reformation on their anterior chamber, however, only a minimal deepening occurred over this interval. At 15 days after surgery, the average anterior chamber of these two patients was significantly more shallow (37.5% of the preoperative anterior chamber depth, p = 0.003) than the mean of the other 18 patients (87.6% of the preoperative anterior chamber depth). These observations suggest that if the anterior chamber has not reformed by postoperative day 15, spontaneous reformation of the anterior chamber is unlikely and surgical intervention may be required.