Sir,

The authors incorrectly cite Ian Mackie's paper (reference 41). Mackie did not advocate the induction of ptosis with botulinum toxin for the treatment of recurrent corneal erosions.

His method was to reduce the action of the orbital part of the orbicularis muscle by injecting it with botulinum toxin.

Thirty-five years ago, Mackie had shown that contraction of the orbital portion of the orbicularis muscle stopped Bell's phenomenon.1 Normal blinking involves only the palpebral portion of the orbicularis muscle and is accompanied by Bell's phenomenon. He presumed that orbital orbicularis action prevented Bell's phenomenon during rapid eye movements in sleep and induced corneal erosion.

Using a modification of Mackie's method, in which I inject into the upper eyelid Riolan's muscle, I have successfully treated eight cases of recalcitrant recurrent corneal epithelial erosions without noticeably altering the eyelid position. The intention is to reduce horizontal tension in the lid, on the basis that shearing between the lid and the ocular surface in combination with overnight reduction in tear secretion, and thus lubrication, is contributory.

I make two injections, each of 4 IU of Botox™ or 12 IU of Dysport™, just above the upper-lid margin near the medial and lateral canthi (Figure 1). The choice of injection site was inspired by Mackie's paper on Riolan's muscle.2

Figure 1
figure 1

Injection sites for botulinum toxin are marked ‘X’. The syringe is orientated to point in the directions of the arrows.

Full size image