From the Bascom Palmer Eye Institute (HA, FF); and the Florida Lions Ocular Pathology Laboratory (SD), Bascom Palmer Eye Institute, Miami, Florida.
The authors have no financial or proprietary interest in the materials presented herein.
Address correspondence to Sander Dubovy, Bascom Palmer Eye Institute, Ophthalmology, Miami, FL 33136. E-mail: SDubovy@med.miami.edu
Glaucoma surgery has been proven to significantly decrease the intraocular pressure and slow the progression of the disease.1 Drainage implants have become an integral part of modern glaucoma surgical procedures. The improvement in design, material, and surgical implantation technique has made this possible.2
One of the major complications of glaucoma implantation is the granulomatous inflammatory reaction induced toward the biomaterial. The fibrosis formed around the tube can potentially restrict filtration and lead to failure of the procedure.3 Micromotion and shearing against adjacent tissue can impinge on extraocular muscles and cause limitation of motility.
The Ex-PRESS shunt (Optonol, Ltd., Neve Ilan, Israel) is a new miniature valveless stainless steel shunt that is inserted at the limbus under a partial-thickness scleral flap. Aqueous humor is shunted from the anterior chamber into a subconjunctival bleb as in trabeculectomy. We report the histopathologic features of an eye with an implanted Ex-PRESS shunt.
A 86-year-old man presented with a painful right eye. The patient had a history of a central retinal vein occlusion that was treated with panretinal photocoagulation in 2000. He subsequently developed neovascular glaucoma in 2005. In 2007, an Ex-PRESS mini glaucoma shunt developed by Optonol, Ltd. was placed. Two years later, the patient complained of severe right orbital pain that required three retrobulbar alcohol injections.
On ocular examination, the patient had visual acuity of no light perception in the right eye and 20/25 in the left eye. The intraocular pressures were 44 mm Hg in the right eye and 16 mm Hg in the left eye. Mild superficial punctuate keratitis was noted in the right cornea. The anterior chambers were deep and quiet in both eyes. Fundus examination of the right eye disclosed panretinal photocoagulation scars. The optic nerve was markedly cupped. His ophthalmic medications in the right eye included dorzolamide and timolol 1 guttae twice a day, latanoprost 1 guttae every hour, ketorolac tromethamine 1 guttae three times a day, and atropine 1% 1 guttae every hour. Due to the persistence of pain, the eye was enucleated and the specimen was sent to the Florida Lions Ocular Pathology Laboratory at the Bascom Palmer Eye Institute for evaluation.
On gross examination, a metallic structure measuring 1 × 3 mm was present with a portion located subjacent to a partial-thickness scleral flap. The remainder of the device was present within the anterior chamber at the 12:30 clock position posterior to the cornea and anterior to the peripheral iris. The base of the implant was located subjacent to the aforementioned scleral flap. The anterior chamber angle appeared closed peripherally.
The specimen was processed for routine histologic evaluation. Examination of serial sections disclosed the imprint of the Ex-PRESS shunt located subadjacent to the partial-thickness scleral flap and overlying conjunctiva. Minimal cellular reaction was identified surrounding the implant. A thin fibrocellular tissue was present deep to the implant. No granulomatous inflammation or marked cellular inflammatory infiltrate was identified (Figs. 1 and 2). The tube portion of the Ex-PRESS shunt entered the anterior chamber anterior to Schwalbe’s line through Descemet’s membrane. The surrounding cornea and sclera were essentially unremarkable. Moderate stromal atrophy of the iris was present adjacent to the shunt. Peripheral neovascularization of the iris was identified on both sides with secondary angle closure.
Figure 1. (A) Histologic section of the right eye discloses the imprint of the Ex-PRESS (Optonol, Ltd., Neve Ilan, Israel) shunt with minimal cellular reaction. (B) Artistic rendition of Ex-PRESS shunt present within the corneoscleral imprint (hematoxylin–eosin, original magnification ×40).
Figure 2. Histologic section of the right eye discloses a thin fibrocellular tissue with minimal evidence of an inflammatory response surrounding the imprint of the Ex-PRESS shunt (Optonol, Ltd., Neve Ilan, Israel) (hematoxylin–eosin, original magnification ×200).
We present the histopathologic features of an eye with rubeotic glaucoma secondary to a central retinal vein occlusion with subsequent placement of an Ex-PRESS shunt.
A major concern of glaucoma drainage devices is the chronic inflammatory response toward the implant and eventual scar formation. The fibrous tissue will isolate the bleb and in time lead to implant failure.
The main glaucoma drainage devices currently in use are the Molteno implant (Molteno Ophthalmic Ltd., Dunedin, New Zealand), Ahmed glaucoma Valve (New World Medical, Rancho Cucamonga, CA), and Baerveldt glaucoma implant (Abbott Medical Optics, Abbott Park, IL). A chief factor in the success rate of the device is biocompatibility, which is determined by its design, biomaterial, and shape. Implants are primarily composed of silicone or polypropylene; the latter induces a larger degree of inflammation.4 The rate of fibrotic encapsulation of the filtration bleb is 40% to 80% in the Ahmed glaucoma implant and 20% to 30% in the double-plate Molteno and Baerveldt implants.1 It is the fibrotic encapsulation of these devices that leads to long-term failure with elevation of the intraocular pressure.
Nyska et al. evaluated the histopathologic findings of the Ex-PRESS shunt in rabbit eyes. The device was implanted into the anterior chamber at the corneoscleral junction in 1 eye each of 8 rabbits while the contralateral eye served as control. Although rabbit eyes have high reactivity, their results showed minimal capsular reaction at 3 and 6 months after implantation.5 De Feo et al. published a case report on the histopathology of the Ex-PRESS shunt in an enucleated human eye that showed a thin, fibrous capsule covering the body of the device with no evident signs of inflammation.6 In this case, the human eye showed similar results with minimal fibrous tissue and inflammation surrounding the shunt. This demonstrates that in these cases the Ex-PRESS shunt implant is relatively well tolerated in the human eye. This may have general applicability for the clinical use of this glaucoma implant.
- Hong CH, Arosemena A, Zurakowski D, Ayyala RS. Glaucoma drainage devices: a systematic literature review and current controversies. Surv Ophthalmol. 2005;50:48–60. doi:10.1016/j.survophthal.2004.10.006 [CrossRef]
- Lim KS, Allan BD, Lloyd AW, Muir A, Khaw PT. Glaucoma drainage devices; past, present, and future. Br J Ophthalmol. 1998;82:1083–1089. doi:10.1136/bjo.82.9.1083 [CrossRef]
- Salthouse TN, Woodward SC. The tissue response to implants and its evaluation by light microscopy. In: Von Recum AF, ed. Handbook of Biomaterials Evaluation. New York: Macmillan; 1984:364–377.
- Ayyala RS, Harman LE, Michelini-Norris B, et al. Comparison of different biomaterials for glaucoma drainage devices. Arch Ophthalmol. 1999;117:233–236.
- Nyska A, Glovinsky Y, Belkin M, Epstein Y. Biocompatibility of the Ex-PRESS miniature glaucoma drainage implant. J Glaucoma. 2003;12:275–280. doi:10.1097/00061198-200306000-00017 [CrossRef]
- De Feo F, Jacobson S, Nyska A, Pagani P, Traverso CE. Histological biocompatibility of a stainless steel miniature glaucoma drainage device in humans: a case report. Toxicol Pathol. 2009;37:512–516. doi:10.1177/0192623309336150 [CrossRef]