Sir,

We read with great interest the paper by Yip et al1 concluding that laser peripheral iridotomy (LPI) for primary angle closure (PAC) is not independently associated with cataract progression.

The authors mention that cataract surgery may be an alternative treatment for occludable angles, potentially addressing both PAC and cataract blindness with one procedure. The potential complications from intraocular surgery, though, are greater than those from LPI. However, LPI has complications such as intraocular haemorrhage and inflammation, intraocular pressure (IOP) spikes, glare, diplopia, and corneal damage. These are primarily not sight threatening, but have to be always taken into consideration.

Another potential complication is cataract formation, and this has been extensively reviewed by Yip et al. Despite their conclusion, there is still some controversy on this matter, with some authors supporting the opposite.2, 3 Thus, one must always be aware of such a theoretical risk after LPI. Except for the disturbances in aqueous flow in patients undergoing LPI, we suggest that, using higher-energy settings, inaccurate focusing of the laser beam, excessive or undertreated post-LPI uveitis, previous intermittent angle-closure episodes with IOP elevation, and other anatomical parameters, yet to be recognised, could be considered as possible stimuli of crystalline lens disturbance with consequent opacification.

A potential complication of Nd:YAG LPI was reported by us recently.4 This involves damage to the zonules with subsequent dehiscence during routine phacoemulsification cataract surgery, affecting an otherwise healthy female with narrow angles. Our paper includes reports suggesting the same effect of LPI (both with Nd:YAG and with argon lasers), resulting in spontaneous dislocation of the crystalline lens.4 We suggested that Nd:YAG LPI may be regarded as an isolated risk factor for structural zonular damage and instability of the crystalline lens, and appropriate precautions should be taken during intraocular surgery. Regardless of the opacification being the result of the LPI, age-related or of any other cause, zonular damage could have considerable implications in subsequent cataract surgery, especially in cases where the zonules are already compromised, such as in pseudoexfoliation syndrome, previous ocular trauma, and congenital systemic diseases like Marfan's syndrome.5

Considering the large number of patients who would potentially benefit from prophylactic LPI, potential adverse sequelae of such a procedure must not be underestimated. More specifically, the possibility of cataract progression and zonular instability after LPI has important implications for patients at risk of angle closure. Choosing between primary cataract surgery and LPI is the main consideration in such cases. The therapeutic approach should be individualised and treatment benefits must always be balanced against eventual complications.

Finally, we would like to congratulate the authors for their excellent contribution on a very important field of ophthalmology.