Sir,

Laser goniopuncture on the trabeculo-Descemet's membrane may be required to treat a late rise in pressure when non-penetrating trabecular surgery (NPTS) begins to fail.1, 2 Herein we report a case of recurrent iris prolapse after laser goniopuncture and prophylactic peripheral iridotomy in a patient treated with NPTS.

Case report

A 22-year-old man received uneventful NPTS with reticulated hyaluronic acid implant (SK-GEL) in his left eye for open-angle glaucoma secondary to angle recession. Seven months later, laser goniopuncture was performed due to uncontrolled IOP, which was almost around 30 mm Hg. Twenty days after laser therapy, he complained of blurred vision and de-centred pupil in the operated eye. On biomicroscopy the pupil was found to be pear-shaped and de-centred superiorly. The transparent triangular SK-GEL implant was observed in the inferior anterior chamber. The IOP was 43 mm Hg. Gonioscopy showed that the superior iris root had prolapsed into the intrascleral chamber through the goniopuncture site. Goniosynechialysis was carried out to reposition the iris root through peripheral corneal incision, but the SK-GEL was left in this phakic eye. To prevent reoccurrence of iris prolapse, laser peripheral iridotomy (LPI) was performed at peripheral iris of 12 o'clock.3

The follow-up visits were unremarkable until 1 year postoperatively he complained again of a de-centred pupil in his left eye. On examination, the pupil was pear-shaped and de-centred superiorly, just like the first episode. The IOP OS was 16 mmHg. Gonioscopy revealed that the superior iris root wedged into the laser hole again (Figures 1a–c). Ultrasound biomicroscopy showed that majority of the superior iris prolapsed into the intrascleral chamber (Figure 1d).

Figure 1
figure 1

(a) Biomicroscopic view of the left eye: the pupil was pear-shaped and de-centred superiorly. (b) Gonioscopy revealed that the superior iris root prolapsed into the laser hole of the Descement’s membrane (red arrow). (c) The SK-GEL lay in the inferior AC (blue arrow) on gonioscopy. (d) Ultrasound biomicroscopy showed that majority of the superior iris prolapsed into the intrascleral chamber.

Full size image

Surgical iridectomy was performed after goniosynechialysis through a peripheral corneal incision, in which the superior peripheral iris behind the laser hole was excised and the SK-GEL was removed from AC. The pupil re-centred after the surgery. During the next 3 years of follow-up, the iris prolapse did not recur.

Comment

Theoretically, prophylactic LPI reduces oscillation amplitude of the iris by balancing the pressure between the anterior and posterior chamber. In this patient, however, iris prolapse recurred after prophylactic LPI, which would have eliminated pupil block as a cause of iris prolapse. Therefore, it is likely that the iris re-migrated into the sclerotomy site in an attempt to seal the outflow of aqueous fluid. This mechanism is seen after surgery and in perforating injuries when the iris adheres to any defect in the wall of the eye. To prevent iris prolapse, a wide trabeculo-Decemet's window and small anterior goniopunctures may be beneficial, while LPI is sometimes insufficient, as shown in this unusual case.2