Sir,

Semi-permanent tarsorrhaphies commonly use Vicryl as a suture material due to its ability to degrade in situ but maintain tensile strength for many weeks. Ionising radiation theoretically can affect its degradation though this phenomenon has not been previously reported in the ophthalmic literature. We present a case of a patient with premature dehiscence of his semi-permanent tarsorraphy whilst undergoing orbital radiotherapy.

Case report

A 52-year-old man with Wegeners granulomatosis and an orbital extension of a left maxillary antral squamous cell carcinoma was seen with a persistent 8-mm left corneal epithelial defect, despite prior treatment with intensive lubricants and upper eyelid botulinum toxin. Contributing factors to the defect included gross left proptosis, lagophthalmos, complete ophthalmoplegia, corneal anaesthesia and daily external radiotherapy for his left orbital tumour. The vision in this eye was NPL.

The patient therefore underwent a semipermanent left tarsorrhaphy using 5′0 Vicryl sutures and continued his daily course of teletherapy. The tarsorrhaphy opened 3 days postoperatively and after the weekend (day 6) had no visible suture remnants. An identical tarsorrhaphy was repeated 3 days later using 5′0 prolene, which remained intact for the residual 2 days of daily teletherapy and which only developed a small, limited dehiscence at 3 weeks. As no further teletherapy was planned, the tarsorrhaphy was revised using 5′0 Vicryl again and remains intact at 3 months.

Comment

Vicryl (polyglactin 910) is a synthetic absorbable material consisting of a co-polymer of lactide and glycolide with good tensile strength and rapid degradation (half-life around 2 weeks).1 Ionising gamma radiation is known to cause chain scission in polyglycolic acid polymers and reduce its molecular weight.2 Treating Vicryl with high-dose gamma radiation accelerates its degradation, forming the basis of the more rapidly absorbing suture Vicryl Rapide.3

We propose that in this case the 5′0 Vicryl suture placed directly in the teletherapy pathway absorbed significant doses of ionising radiation leading to its premature degradation in the first tarsorrhaphy. This did not occur with the Prolene suture or when Vicryl was used after completion of the radiotherapy. Furthermore, the very superficial placement of the suture in the path of the radiation would lead to much greater degradation as compared with longer-acting absorbable sutures such as poly(L-lactide/glycolide) placed in a deep subcutaneous environment.4 This phenomenon has not been previously described in the ophthalmic literature and has implications for choice of suture material placed in patients receiving radiotherapy.