Comment on: Variations in morphology and patency of disposable hydrodissection cannulas used in cataract surgery

I read with interest the article by Mudalegundi et al.¹ As a medicolegal expert, I deal with breaches of duty and levels of care expected on a daily basis. We owe a duty of care to ensure that all the equipment used for our surgeries is safe to use.

Patients have to accept risks of surgery, and unfortunately, things can and do go wrong. Unavoidable complications are by their very nature unavoidable; however, introducing sharp instruments into the eye due to poor manufacturing is not something a patient would accept as a valid excuse for potential visual loss. Many surgeons use the cannula tip to polish the posterior capsule and remove cortical remnants. If the sharpened edge of a cannula ruptures the posterior capsule because of imperfections in manufacturing or accidental damage, then we have performed our patients a disservice.

We know that similar issues arise with the irrigation and aspiration tips, whereby sharp edges can be seen on the metallic tips under high magnification, and these can also risk the posterior capsule during otherwise routine cataract surgery.²

The authors discuss the risk of contamination causing toxic anterior segment syndrome (TASS) and indeed that is correct; however, contamination also risks postoperative endophthalmitis, which is catastrophic. Furthermore, they mention the issue of cannula dislodgment, and indeed, a recent survey published in this journal highlighted the frequency of this avoidable complication that would result in even greater harm if the ejected cannula had sharper edges at its tip.³

To avoid the risk of cannula dislocation with ophthalmic viscosurgical devices, some manufacturers provide a screw cap that goes over the cannula. The cannula is thus threaded through a small hole, and it is difficult to thread the needle without making contact with the plastic insides of the cap. This could theoretically cause damage to the delicate tip of the cannula resulting in sharp edges or contamination with all the concomitant risks of infection or TASS.

If using the screw cap great care should be taken to avoid hitting the sides and causing inadvertent damage to the tip as well as avoidance of touching the gloved hand with the tip during the application. Furthermore, according to the aseptic nontouch technique, an internationally recognized standard, key parts, such as the cannula tip, should not be touched with even a gloved hand to avoid contamination, and therefore ideally, the screw cap should be applied with forceps or another device to keep fingers clear.⁴

Surgeons have a duty and a responsibility to their patient to ensure that the surgical tools are fit for purpose and do not expose patients to the risk of avoidable harm.