Response to ‘Role of miotics and cycloplegics in angle closure’

Sir,

We sincerely thank Dr Gupta for his expert comments¹ on our article.² Urbanek had coined the term inverse glaucoma to describe the pupillary block caused by miotics. Miotics cause ciliary muscle contraction, slackening the zonules, causing forward movement of the crystalline lens, thus shallowing the anterior chamber and increasing the pupillary block.³ We have used miotics to prevent an anteriorly dislocated crystalline lens from falling back into the posterior chamber/vitreous before surgery. Ritch and Wand propose the use of thymoxamine after a peripheral iridotomy to prevent lens dislocation into the anterior chamber. Thymoxamine is an alpha adrenergic blocker that causes miosis by inhibiting sympathetic pupillary dilatation and does not affect the ciliary muscle.⁴ We do not have any personal experience with the use of thymoxamine and the drug for ocular use is not available in our country. Cycloplegic agents on the other hand relax the ciliary muscles, tighten zonular support thereby pushing the lens back and deepening the anterior chamber.⁴ As Dr Gupta D rightly points out, the effect of miotics and cycloplegics would depend on the zonular integrity that is difficult to predict. It has been our experience and that of others^{4, 5} that the use of mydriatics is associated with a high incidence of lens dislocation in the anterior chamber. Cyclopentolate has been reported to produce bilateral angle closure glaucoma in a patient with Weill Marchesani syndrome.⁶ We believe that a laser peripheral iridotomy is a more reliable way to prevent pupillary block in microspherophakia and pharmacological agents (miotics/mydriatics) may have a very limited role in the management of this condition. Caution is advised with their use.