Treating strabismus

Evaluating minimally invasive strabismus surgery versus Fornix incision

Soosan Jacob

Posted: Tuesday, May 1, 2018

Simon Westby

Minimally invasive strabismus surgery (MISS) is an exciting new option for the treatment of strabismus, potentially offering several advantages over current conventional techniques, Simon Westby, University College London, UK, told the World Congress of Paediatric Ophthalmology and Strabismus in Hyderabad, India.

Mr Westby first detailed the technique itself. Two radial parainsertional keyhole incisions are made at the upper and lower borders of the muscle respectively, with a sub-Tenon tunnel connecting the incisions. A recession or plication is then performed. The theoretical advantages of this technique include more rapid healing, reduction in immediate postoperative complications and reduced long-term postoperative scarring.

He said that although previous data by Sharma et al. in 2014 suggested a benefit in the short-term complication rates for MISS as compared to the limbal incision, no studies have compared it to the Park’s fornix incision. This was especially important because the majority of the potential benefits of MISS could also be applied to Park’s fornix incision surgery. His study therefore aimed at looking for any difference in effectiveness, quality of life, complication rates and surgical success between these two approaches.

This was a prospective study over nine months that included 14 patients, with seven in each group. The fornix recess-resect procedure was compared with a MISS recess-plication procedure for horizontal strabismus surgery, as measured by dioptres achieved per mm moved, pre- and postoperative Adult Strabismus-20 (AS-20) questionnaires and postoperative complication rates.

The study found a significant difference in the effectiveness of the surgical procedures, with MISS showing reduced effect of surgery per mm. The significant difference in effectiveness could in part be explained by the fact that MISS patients underwent plication versus a resection for the fornix incision group.

MISS patients also had a smaller preoperative angle of deviation and it is known that higher angles of deviation generally respond better to surgery. In addition, there could be some effect of fascial pulleys that remain following incomplete dissection. He also highlighted that intraoperative target visualisation is reduced during MISS, and hence the distance that muscles are moved may be overestimated. Taken together, he emphasised that this finding should be taken into account during patient selection and when deciding on surgical dosage.

The study found no significant difference in postoperative complication rates, surgical outcome or in pre- and postoperative AS-20 scores. A lack of significant difference in postoperative complication rates likely reflected the short follow-up period of his study. Indeed, it was possible that with longer-term follow-up, MISS would show reduced fibrosis and scarring compared to Park’s fornix incision and thus provide easier access and better tissue quality for any redo procedures.

To conclude, he stressed the importance of the study as a step towards understanding the role of MISS and the need for larger, randomised studies with longer follow-up.

Simon Westby:

In our May 2018 issue we published an article entitled “Treating strabismus”. It covered a presentation given by Mr Simon Westby at WCPOS 2017 in Hyderabad. Mr Westby would like to clarify that Mr Saurabh Jain and Ms Naomi Tan were co-authors of the project and all the procedures took place at The Royal Free Hospital in Hampstead, London, UK.