From waste to wonder: Transformational advances in scleral allograft technology
Unlocking the potential of donor scleral tissue: Innovations and future applications.
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When organs are donated, it is with the expectation that the contribution will benefit science. However, with donor scleral allograft tissue, whereby over 90% of harvested tissue is discarded, this is not always true.
According to the 2022 Eye Banking Statistical Report1 by the Eye Bank Association of America (EBAA), of 108,382 whole globes donated to eye banks, only 2,247 donor scleral patch grafts are used annually in the US—just 2% of all donor eyes and a small fraction of the total scleral tissue. Moreover, the use of donor scleral allograft is declining, with 3,151 scleral grafts used in 2020 vs 2,247 grafts in 2022, a reduction of almost 30%. This is despite the significant advantages of scleral allograft tissue: It is acellular, nonbiodegradable, highly inert, and biocompatible. Unlike cellular corneal grafts, which must be processed and used within days, scleral allograft material is sterilized, can be stored at room temperature, and may have a shelf life of up to 2 years.
The primary use of donated scleral tissue is in scleral reinforcement surgery. Over 90% of the procedures are performed in the context of glaucoma shunts, where the scleral allograft tissue is used to cover the tube and prevent erosion.
Two significant trends over the past decade have accelerated the decline in scleral allograft use, a shift toward the use of clear cornea allografts for tube coverage to achieve better cosmesis, and the bundling of scleral reinforcement surgery (Current Procedural Terminology (CPT) code 67255) and tube shunt implant surgery (CPT code 66180), which took place in 2015 and resulted in notable reductions to reimbursement.
A Better Future Is on the Horizon
Multiple drivers stand to decrease the waste of donated tissue and increase the utilization of scleral allografts, including increased reimbursement rates of scleral reinforcement surgery (CPT code 67255) will limit financial barriers for surgeons and facilities, and innovations in allograft processing have increased the number of clinical applications beneficial to surgeons and patients alike.
In 2024, the increased payment rate for scleral reinforcement was one of the few bright spots in ophthalmology’s reimbursement landscape. Scleral reinforcement surgery (CPT code 67255) nearly doubled in reimbursement from $1101 to $2045. Additionally, the Medicare Physician Fee Schedule 2024 national unadjusted payment rate for CPT code 67255 is $683. Finally, when scleral reinforcement (CPT code 67255) is not done in combination with CPT code 66180 (glaucoma shunt procedure), it is reimbursed either as a primary or secondary procedure, allowing surgeons to leverage the benefits of scleral reinforcement in a wide array of surgical settings.
A recent article by De Francesco et al2 highlights new innovative techniques in allograft biotissue processing and new clinical applications. A meaningful advancement the authors note is the recent ability to produce high-precision microtrephination of allograft tissue. This minimally manipulated micro-interventional scleral allograft can achieve focal ab interno or ab externo scleral reinforcement to scaffold, stent, and strengthen the native anatomy where medically necessary. Such applications already in clinical use include bioscaffolding of cyclodialysis for durable maintenance of a cyclodialysis cleft and to reduce early occlusion and restenosis. Microtrephined grafts can also be used to occlude and stent fistulas, over-filtering flaps in trabeculectomy and leaking optic disc pits in retina surgery.
The Future Is Now
An exciting development in the use of scleral allograft tissue and interventional glaucoma is being used in operating rooms across the United States. Microtrephined scleral allografts explicitly designed to reinforce sclera following the creation of a cyclodialysis cleft will allow ophthalmologists to treat the uveoscleral outflow pathway surgically—a highly anticipated solution for patients suffering from glaucoma.
In data from a recent study presented at both the American Academy of Ophthalmology 2023 and American Society of Cataract and Refractive Surgery 2024 meetings, the use of bio-interventional scleral reinforcement following the creation of a cyclodialysis cleft was found to result in a sustained 40% reduction in IOP from baseline at 12 months. Of note, the procedures were completed with no significant complications.
Additionally, the homologous nature of the microtrephined scleral allograft appears to integrate naturally with the native endoscleral gonio-anatomy with minimal fibrosis and foreign-body reaction, ultimately leading to long-term enhancement of uveoscleral outflow as well as structural and functional durability.
Reimbursement pathways for cyclodialysis cleft surgery and scleral reinforcement surgery are well established with Category I CPT codes, where the CPT code 67255 is used for the scleral allograft reinforcement procedure and CPT code 66740 for the cyclodialysis. The two codes can be billed in combination where medically appropriate.
References:
Mathews P, Benbow A, Corcoran K, DeMatteo J, Philippy B, Van Meter W. 2022 Eye Banking Statistical Report—Executive Summary. Eye Bank Corneal Transpl. 2023;2(3):e0008. doi:10.1097/ebct.0000000000000008
De Francesco T, Ianchulev T, Rhee D, Gentile R, Pasquale L, Ahmed I. The evolving surgical paradigm of scleral allograft bio-tissue use in ophthalmic surgery: techniques and clinical indications for ab-externo and ab-interno scleral reinforcement. Clin Ophthalmol. 2024;18:1789-1795. doi:10.2147/opth.s462719
