| ◄▬ | Miragel artikelen - 1992 Marin ea | ▬► |
Marin, Tolentino, Refojo en Schepens, ‘Long-term Complications of the MAl Hydrogel Intrascleral Buckling Implant’, (Arch Ophthalmol-Vol 110, January 1992)
Marin e.a. beschrijven in hun artikel van januari 1992 ‘ Long-term Complications of the MAl Hydrogel Intrascleral Buckling Implant ’, lange-termijn-complicaties van de "MAl hydrogel intrascleral buckling implant", die 7-11 jaar na de operatie optraden.
Geadviseerd werd om periodieke lange termijn controles te houden bij patiënten die met de
MAl implant waren geopereerd.
Direct al in het abstract van het artikel wordt gewaarschuwd m.b.t. de MIRAgel implant:
Seven cases in which long-term complications developed from swelling of the MAI hydrogel intrascleral buckling implant are reported herein. Micro-Fourier transform infrared spectroscopic analysis of two recovered implants demonstrated the occurrence of chemical changes leading to increased swelling. Clinical problems with the implants appeared 7 to 11 years after surgery, suggesting the need for periodic, long-term follow-up. It is possible that the present-day MIRAgel implant, which has the same composition as the MAl implant, may require similar precautions.
In het artikel zelf wordt de MAl implant beschreven:
The MAI implant, also known as the Refojo implant, is a synthetic, hydrophilic scleral buckling material introduced in de late 1970s.1-2 MAl is made ofpoly(methyl acrylate-co-2-hydroxyethyl acrylate) crosslinked with ethylene driacrylate with 15% water. The material is soft, elastic, and smooth and can be heat sterilized.
The MAl implants were first used in 1979 at equilibrium hydration (15%) and functioned as either the primary episcleral or intrascleral buckling elements or as meridional implants under solid intrascleral silicone rubber buckles. Seven of 82 patients in whom this material was used intrasclerally for buckling from 1979 to 1982 developed complications from swelling of the implant. We report this complication in seven patients treated at Retina Associates, Boston, Mass.
In een van de vier gerapporteerde gevallen kon na 10 jaar de implant, die door erosie een glasvochtbloeding had veroorzaakt, niet volledig verwijderd worden omdat deze in stukken brak. Bij een operatie 3 maanden later kwam het niet verwijderde gedeelte door een grote netvliesscheur in het glasachtig lichaam en werd alsnog verwijderd met pars plana vitrectomy. Negen maanden later had het oog geen zicht meer.
CASE 4. A 66-year-old man underwent a scleral buckling procedure in April 1979 for rhegmatogenous retinal detachment. During surgery, subretinal fluid drainage was complicated by retinal perforation and vitreoretinal incarceration. To augment indentation, two MAl implants were placed side by side in a meridional fashion under the 279 solid silicone implant from the 9:30 to 11:30 positions. The postoperative course was uneventful, and the patient was unavailable for follow-up.
Ten years later the patient returned with a vitreous hemorrhage secondary to implant erosion. Two months later, after partial clearance of the hemorrhage, he underwent a buckle revision for recurrent retinal detachment. Removal of the implant was incomplete because the friable implant broke into pieces. Subretinal and vitreous fluid drained spontaneously. Choroidal detachment and proliferative vitreoretinopathy (class D3) developed after surgery.
Three months later, the patient underwent a closed vitrectomy with membrane peeling. During smgery, the remaining implant passed into the vitreous cavity through a large retinal break and was subsequently removed via the pars plana. At the end of the procedure, silicone oil was injected intravitreously to restore the ocular volume and maintain retinal tamponade.
After surgery, a pupillary membrane developed and vitreoretinal disorganization ensued, leading to globe atrophy despite a third surgical intervention. Nine months after implant removal, the eye was comfortable but had no light perception.
De auteurs merken op dat erosie niet uniek is voor de hydrogel implant maar zich voordoet bij alle huidige implants. Ook siliconen materiaal kan dit niet uitsluiten. Daarom is levenlange jaarlijkse controle aan te bevelen. De eigenschappen vande MAI plombe leken beter te zijn, maar nu rapporteren de auteurs de eerste gevallen van late erosie door deze implant.
Comment (...)
In a review of the MAl implant by Ho et al 4 several features of the implant as a buckling material were emphasized:
(1) it was as effective in buckling as solid silicone rubber and silicone sponge; (2) the degree of swelling could be varied by altering the state of hydration;
(3) its softness and elasticity were thought to guard against erosion;
(4) it was assumed to be less prone to infection because it lacked dead spaces and could absorb and gradually release antibiotics; and
(5) it stimulated the production of a surrounding fibrous capsule that
strengthened the sclera and presumably ensured the ease and safety of
subsequent operations.
Because of animal experimentations and clinical results 6 in 82 eyes of 79 patients who were followed up for 6 to 53 months after surgery, the implant was believed to be a safe, well-tolerated material. 6,7 The dependence of the implant's swelling property and hardness on hydration was viewed as an advantage for customizing buckle indentation with minimal risk of scleral erosion.
Seven clinical cases with long-term complications related to the swelling
properties of the intrascleral MAl implant were presented herein. Problems
ranged from a visible, benign, subconjunctival bulge to intraocular erosion
and migration of the implant. The MAI implant was used in patient 1 as a
primary buckle without a band, in patient 5 with a band, and in patients 2,
3, 4, 6, and 7 as meridional buckles under solid silicone rubber implants.
In seven (8.5%) of 82 case~ in which MAl was used intrasclerally, problems
surfaced 7 to 11 years after surgery.Micro-Fourier transform IR spectroscopy (Figure) confirmed the occurrence
of chemical changes within the polymer. The presence of carbolic groups mplies ester hydrolysis, which may have led to structural instability. The ionized carbolic groups result in a hydrogel that absorbs more water than the original polymer. The implant swelled and changed from opaque, soft, spongy, whitish, and compact to translucent, gel-like, cream-colored, and friable. Eventually, the swollen implant protruded and eroded through the diseased or scarred scleral bed into the vitreous cavity.
Implant erosion is not unique to the hydrogel implant. This complication reportedly has characterized all implants used to date.8 It was first noted in the 1950s with polyethylene tubing. This material was noted to harden in the tissues, and its erosion was precipitated by elevation of intraocular pressure. Donor sclera, sutures, and gelatin 9 have also been reported as being capable of causing erosion of the sclera.
The shift to silicone materials presumably reduced the risk of erosion but did not eliminate it. For this reason, a lifetime, yearly follow-up was recommended af ter silicone rubber implants were used. 10 Acute 11 or chronic 8 erosion is sometimes observed under episcleral silicone sponges held in place by scleral sutures. Because of the physical properties of the MAl implants,4 it was thought to be a better buckling element. Initial reports 4-7 attested to its effectiveness and safety. However, due to some alterations in its chemical composition and eventual swelling, we report the first cases, to our knowiedge, of late erosion by the implant.
The MAl implant is the precursor of the present-day MIRAgel; they have the same chemical composition. Hence, potential problems related to swelling of the implant exist and warrant diligent, periodic follow-up of patients for a long time af ter surgery. However, to our knowiedge, similar complications in patients who receive an episcleral implant have not been reported. We have used MIRAgel as an episcleral implant in a large number of patients since 1986 and have not observed such complications.
Randy Hasslinger, director of Research and Development at MlRA Inc., Waltham, Mass. Reageerde in hetzelfde nummer van Arch Ophthalmol- Voll110, January 1992 , als volgt:
To the Editor .-We at MlRA Inc, Waltham, Mass, have had the opportunity to support the investigation of MAI hydrogel implants described in this issue of the ARCHIVES. We performed the micro-Fourier transform infrared spectroscopic analysis that compared the clinical specimen from case 3 with production lots of hydrogel implants of different ages.
The spectroscopic analysis revealed that the clinical specimen had a polymeric structure significantly different from that of the production lots, but this does not imply that the clinical specimen degraded in vivo. The clinical specimen was synthesized from a laboratory batch process that predated the production lots. These laboratory batches were experimental and known to contain variable levels of components that would account for the differences described by the spectra. Polymers most resistant to degradation are prepared with careful control for extent of polymerization, level of impurities, and ratio of components. Furthermore, a hydrogel sample from the same laboratory batch was not available to serve as a control in the analysis. The original structure of the clinical specimen could not be confirmed.
To date, there have been no patients with MIRAgel implants who have developed the complications described in the report by Marin et al. MIRAgel continues to be manufactured according to good manufacturing practice guidelines for strict formulation and processing controls.
MlRA Inc concurs with the authors for lifetime annual follow-up of sc1eral buckling procedures regardless of tbe buckle material used.
Marin et al. reageerden in een naschrift als volgt:
In Reply.-We concur with Mr Hasslinger that because we were unable to obtain unused MAI polymer implants of the same vintage as the polymer implants retrieved from the patients, we cannot be sure that the hydrolysis observed in the retrieved implants was not a phenomenon characteristic of these early MAl samples. The polymer implants retrieved from the patients were made before MlRA Inc obtained the license from the Eye Research Institute to make MIRAge!. However; MAl polymer made by the same procedure as the retrieved implants, and the currently available MIRAgel implants have the same chemical composition, as is demonstrated by the identical micro-Fourier transform infrared spectra.
In fact, there are no data available to us to support Mr Hasslinger's remark that the early MAI "laboratory batches were experimental and known to contain variabie levels of components th at would account for the differences described by the spectra." Sterile MAl implants stored in saline solution in the laboratory for several years maintained their original hydration and chemical structure. The changes we re only observed in retrieved intrascleral MAl implants.
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| ◄▬ | 1992 Marin ea | ▬► |