◄▬ 2007 Roldan-Pallares ea ▬►

Roldan-Pallares ea, Hydrolytic Degradation and Long-term Observations, Arch Ophthalmol 2007; Vol. 125 NoA   

Dit is de eerste grote retrospecieve studie naar de complicaties van episcleraal geplaatste Miragel plombes bij 415 patiënten, bij wie tussen maart 1984 en december 2000 Miragel plombes zijn toegepast. 

DESIGN AND SETTING 
Herein we describe an interventional consecutive case series of patients with rhegmatogenous retinal detachment who underwent scleral buckling surgery with the MIRAgel explant as a first surgical procedure between March 1, 1984, and December 31, 2000. The patients underwent operation at the Hospital Clinico San Carlos, Madrid, Spain, by one of us (M.R.-P.) with cryotherapy associated with the episcleral buckle.16 This is a retrospective institutional clinical study.  (…)

De auteurs brachten in kaart:

De criteria voor operatieve verwijdering betroffen de veranderingen als gevolg van de zwelling van de Miragel plombes.

RESULTS
(…) The criteria for buckle removal included morphological and/or functional changes related to swelling of the MIRAgel material. Removal was necessary in 27 (6.5%) of 415 patients with MIRAgel buckle explants. Clinical manifestations, frequently multiple, in patients with removed explants included redness and discharge in 25 (93%) (cultures yielded Staphylococcus epidermisin only 3); extrusion in 6 (22%); subconjunctival mass and/or protrusion of the buckle beneath the eyelids in 19 (70%); strabismus, rectus palsy, limitation of ocular motility, and/or diplopia in 18 (67%); and orbital fullness and/or pseudotumor in 6 (22%). (…)
COMMENT
(...) In our cases, swelling of the MIRAgel explant combined with progressive limitation of ocular motility and protrusion of the buckle beneath the eyelids frequently indicates the need for MIRAgel removal, as reported by other authors.6-8

Conclusie: ingeval van klachten dient dadelijke verwijdering in overweging te worden genomen ter vermijding van toenemende complicaties.

Abstract

De auteurs vermelden de Miragel problematiek.

Hydrogel implants (originally MAI and then commercialized as MIRAgel [MIRA Inc, Waltham, Mass]) initially seemed to be the ideal implant material,with a soft pliable texture and low risk of infection,1,2 when observed 6 to 53 months after surgery.3 However,with a longer follow-up of 7 to 11 years, complications have been reported in 8.5% of patients after an intrascleral buckling procedure.4 Recently, several reports of removal of MIRAgel episcleral buckling material have been published.5-8 Clinical manifestations ranged 5-8 from benign subconjunctival bulging, pain, strabismus, progressive limitation of ocular motility, protrusion of the buckle beneath the eyelids, and sensation of orbital fullness to pseudotumor 9 for the episcleral buckles or to intraocular erosion and migration into the vitreous for intrascleral procedures.4,10 After Hwang and Lim 11 reported the first case of scleral buckle extrusion and fragmentation associated with a MIRAgel episcleral explant, other cases have also been published.12,13
Fragmentation and peripheral degradation of hydrogel have been described in experimental models.14 The hydrogel fragments were found next to the inner limit of the surrounding fibrous capsule in human eyes undergoing reoperation; these were often found in association with mononuclear and giant cells, attesting to a foreign-body giant cell granuloma.15 Hydrolytic degradation of MAI hydrogel using micro-Fourier transform infrared spectroscopy was demonstrated by the presence of carboxylic groups in 2 recovered implant segments.4 The polymer implants (MAI) retrieved from these patients 4 were made before MIRA Inc obtained the license to make MIRAgel.14 Although the MAI hydrogel is the precursor of MIRAgel and both have the same chemical composition, up-to-date hydrolysis of MIRAgel has not been demonstrated. analysis of the explanted MIRAgel buckles from 3 patients for potential changes in the polymeric explant To further understand the long-term complications of MIRAgel episcleral buckles, we report the clinical outcome of 415 patients after MIRAgel buckling implantation for a mean follow-up of 187 months (range, 75 months to 20 years). We evaluated the results of microFourier infrared spectroscopic structure.

In deze studie relateren de auteurs naar hun weten voor de eerste keer tot dusverre de aanzienlijk gezwollen episcleraal toegepaste Miragel plombes aan de hydrolytische degradatie ervan. De combinatie met een silicone cerclagebandje vegrootte het aantal verwijderingen.

COMMENT
For the first time, to our knowledge, considerably swollen MIRAgel explants and clinical manifestations of orbital pseudotumor have been related to hydrolytic degradation of episcleral MIRAgel demonstrated by infrared spectroscopy. Removal of these buckles is a consequence of the explant’s progressive degradation and swelling. At present, removal has been necessary in 27 (6.5%) of 415 patients who received MIRAgel explants, and in 27 (7.6%) of 357 patients who received MIRAgel explants 7 or more years earlier. Eight of these 27 cases have already been reported.5,17 
It has been suggested in the literature 6-8 that a greater quantity of material used will increase the possibility of removal. In our patients, there was a trend toward a higher removal rate (Table) with an increased quantity of buckling material, and any of the cases with MIRAgel used as an additional and small side-by-side indentation to resolve a fishmouth phenomenon required removal. The association of MIRAgel with a silicone band of cerclage also increased the removal rate in our patients. As first suggested by Marin et al,4 the sutures may play a role in the physical or functional breakdown of the surrounding fibrous capsule, allowing hydration and swelling of the MIRAgel explant. 
In our cases, swelling of the MIRAgel explant combined with progressive limitation of ocular motility and protrusion of the buckle beneath the eyelids frequently indicates the need for MIRAgel removal, as reported by other authors.6-8 The symptoms usually started with redness and discomfort, and it took a mean of 15 (range, 6-22) months to slowly develop those symptoms related to swelling of the material. Six of our patients had orbital pseudotumor at the initial examination and required computed tomography and/or magnetic resonance imaging for diagnosis. Two of these cases with orbital pseudotumor (the interval from the start of redness and discomfort to removal was 20 and 22 months; the time from implantation to removal of the MIRAgel material, 11.1 and 11.2 years) showed great swelling of the MIRAgel explant related to its hydrolytic degradation. 
To our knowledge, this is the first report demonstrating hydrolytic degradation of MIRAgel by the presence of carboxylic groups using micro-Fourier transform infrared spectroscopy. Until now, chemical changes in the polymer were only confirmed spectrographically for the MAI hydrogel intrascleral implants.4 The presence of carboxylic groups found in our removed explants implies ester hydrolysis. The ionized carboxylic groups result in water absorption and, consequently, the MIRAgel material swelled and became gellike and friable. These characteristics explain the difficulty in grasping and removing MIRAgel fragments—sometimes embedding in the scleral wall, which then became thicker and rigid—and complications related to surgical removal. Persistence of discomfort after MIRAgel retrieval may likely be associated with residual MIRAgel fragments. 
After MIRAgel removal, the retina remained attached in 23 (85%) of 27 patients with stabilized visual acuity. In 2 of the cases of pseudotumor and considerable swelling of the MIRAgel material, scleral perforation occurred during removal with intraocular hemorrhage and final retinal redetachment. Retinal redetachment was found in 4 (15%) of 27 patients after MIRAgel material removal. The eyes usually became orthophoric and diplopia disappeared, but redness, discomfort, and ocular motility disturbance persisted in 6 (22%) of the 27 removal cases. We agree with Le Rouic et al 6 that patients should be informed of the possibility of complications related to the surgical removal of episcleral MIRAgel buckles.
Cultures in only 4 of our 27 removed MIRAgel explants yielded positive results. Negative culture findings may be owing to long-term antibiotic and/or corticosteroid therapy that was used to treat redness and discharge, or owing to the particular characteristics of the MIRAgel material. MIRAgel was reported to be an ideal buckling element that was considered less prone to infection because it lacked dead spaces and could absorb and gradually release antibiotic drugs.5,18 
Hence, MIRAgel buckles resulted in delayed, late complications owing to buckle swelling from hydrolytic degradation and required removal in 6.5% of patients, with a mean follow-up of 187 months. Patients with MIRAgel buckles require long-term follow-up, and removal should be considered once symptoms develop

◄▬ 2007 Roldan-Pallares ea ▬►
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