Most reports of suture intrusion have concerned encircling sutures [
4,
5], which are actually encircling bands. The intrusion of an anchoring suture or suture knot is relatively rare [
6,
7]. Here, we have reported a case of the intrusion of a PET suture knot 15 years after scleral buckling surgery.
The manifestations of intrusion vary, from asymptomatic to severe visual loss attributable to vitreous haemorrhage or retinal detachment [
1,
2,
8‐
11]. In our case, the patient presented with highly elevated IOP and eye pain, headache, and nausea, and a clinical examination detected hyphema and vitreous haemorrhage. The intrusion of the suture knot was only found during surgery, so in patients with a history of scleral buckling, the possibility of intrusion must be considered.
An analysis showed that the suture was PET, possibly Dacron, a nonabsorbable suture from Alcon. PET is a compound synthesized from ethylene glycol and terephthalic acid in a polycondensation reaction, and is highly resistant to disintegration when buried in tissue [
12,
13]. In our patient, the suture knot was resting on a ring-shaped protrusion, and both the knot and the encircling silicone band were intact. Therefore, it is unlikely that the node was the anchoring suture for the encircling silicone band, but rather that the suture had been used to close the drainage port for subretinal fluid, and was covered by the encircling band. Weinberger reported that the intrusion of anchoring sutures occurs as a late complication of retinal detachment surgery when the extra-scleral buckling technique is used [
7]. But in our case, the suture was not the anchoring one. Schepens reported that erosion commences and progresses as the implant is held firmly against the sclera by the sutures, the encircling element, or the solid scar tissue that has grown over the external surface of the implant [
1].In our case, the Dacron knot may have been held against the scleral wall by the encircling band. The patient was highly myopic, another risk factor for intrusion. Moreover, the sclera was further weakened by the incision made for the drainage of the subretinal fluid. Cooper et al. reported a case in which a 5–0 Dacron scleral suture knot had eroded into the vitreous cavity 12 years after scleral laceration repair, pars plana vitrectomy, the removal of an intraocular foreign body, and a scleral buckling procedure for penetrating injury [
6]. In their case, the Dacron suture was used to close the scleral laceration, and had been covered with a 5 mm radial scleral sponge and overlain with an encircling 240 band. In both Cooper’s and our patients, the encircling band held the suture firmly against a sclera that had been compromised by a traumatic or surgical incision. Therefore, covering a nonabsorbable suture with an encircling band should be avoided in the buckling procedure, especially when the sclera is impaired by trauma, pathological myopia, or surgical incision. If a suture is unavoidable, then a soft, absorbable suture may be preferable.
In conclusion, when covered with an encircling band, a nonabsorbable suture, which is usually placed where the sclera has already been compromised, could erode the sclera and intrude into the vitreous cavity.