ReviewScleral buckling biomaterials and implants for retinal detachment surgery
Introduction
Retinal detachment (RD) is a serious pathological condition which can eventually lead to total vision loss in the affected eye if it is not promptly treated [1], [2], [3]. In order to treat the RD and depending on its extent, size and features, the surgeon may decide to perform surgical procedures of pneumatic retinopexy, scleral buckling or vitrectomy combined or not with scleral buckling [4], [5], [6], [7], [8], [9], [10]. During these surgical procedures, all the retinal holes, if present, must be sealed by laser photocoagulation or cryoteraphy in order to preclude the fluid flow into the subretinal space, thereby preventing retinal re-detachments.
Scleral buckling is a widely used procedure for treating RDs: its effect is to maintain the neurosensory retina and the retinal pigment epithelium (RPE) attached to each other until the healing process accompanied by scarring has taken place, thereby ensuring that the retina remains tightly attached thereafter to prevent further RD; in addition, it also contributes to relieve vitreo-retinal tractions [6].
A wide range of natural or synthetic materials has been proposed and tested in the course of scleral buckling procedures carried out on animal models and humans and, at present, most surgeons considers permanent silicone buckle(s) as the “gold standard” choice. However, further improvements can be achieved: for instance, the design and development of resorbable buckles could be very suitable for treating RD in children, as such implants do not carry the need for surgical removal, which is necessary for non-absorbable buckles to allow the normal growth of child's eye. In addition, recent advances concerning the modelling of eyeball deformation under scleral cerclage open new perspective towards the design of an optimal and tailor-made buckle depending on the peculiar features of each clinical case.
This article, after giving a short overview on eye anatomy and physiology, as well as on the methods commonly adopted in retinal detachment surgery, focuses specifically on scleral buckling procedures and provides a comprehensive picture – at the best of the author's knowledge – about the materials used for manufacturing scleral implants. For the first time, the suitability, advantages and drawbacks of the materials currently in use, with particular emphasis on silicone implants, are outlined and extensively discussed and, finally, a forecast for the future is presented.
Section snippets
Anatomy and functions of the eye: short overview
The eyeball, or ocular globe, is approximately a spherical shell that is transparent at the front portion and opaque (or nearly so) over the remaining 80% of its surface [11]. The main structures of the eye are represented in Fig. 1. The optical path consists of a series of transparent liquids and solids: beginning from the exterior and proceeding towards the retina, it is possible to find in succession the cornea, the anterior chamber containing the aqueous humour, the iris, the posterior
Retinal detachment
According to the specific pathogenic mechanism, RDs can be divided in three groups [1], [6]: (i) rhegmatogenous RD (RRD), (ii) tractional RD (TRD) and (iii) exudative RD (ERD). In RRD, fluid from vitreous cavity enters the sub-retinal space through a full-thickness retinal break; in TRD, the retina is mechanically lifted up as a result of vitreous tractions, for instance induced by the presence of vitreo-retinal membranes in the case of diabetic retinopathy; ERD is caused by fluid leakage from
Biomaterials for scleral buckling
In the beginning, the design of scleral buckling materials and implants was quite easy: essentially, the surgeon needed an element that would encircle the eye partially or totally along globe equator, thereby creating an indentation that would approximate the neurosensory retina to the underlying RPE. Progressively, surgeons developed new element shapes and styles in order to improve the outcome of the specific applications they had in mind.
Table 1 chronicles the development of scleral buckling
Polyviol
In the early 1950s, Custodis implanted the first permanent buckle by using polyviol as buckling material [40], [41]. Polyviol was a red rubber, constituted by poly(vinyl alcohol), Arabic gum and Congo red, that could be compressed over the sclera to about half of its original thickness; the buckle was held in place by means of silk sutures. Over the next few hours after surgery, the explant expanded thereby creating a high buckle that closed the retinal breaks and reattached the retina without
Absorbable implants
A wide range of absorbable materials of biological or synthetic origin has been tested to achieve a temporary buckling effect. Biological materials have been derived from human or animal tissues, and they could be used for performing transplants (autografts, allografts and xenografts) or properly treated for obtaining suitable substances, e.g. collagen or fibrin. Biological materials carry some problems, such as limited availability and morbidity at the harvest site for autologous tissues and
Summary of the present strategies
The procedure to be followed by surgeons for treating RD has to be carefully selected depending on each specific clinical case. Non-invasive procedures based on laser photocoagulation are usually adopted for preventing further enlargements of small retinal hole(s), thereby preventing RRD [1], [4], [5], [6]. Pneumatic retinopexy or scleral buckling are commonly used for treating uncomplicated RRDs, whereas in the case of multiple retinal breaks, giant tears or TRD, vitrectomy by itself or the
Towards an ideal scleral buckling material: an integrate approach
Although silicone implants are commonly considered the “gold standard” choice and the high variety of styles and designs allows the surgeon to treat successfully a very wide range – at least virtually – of RD requiring a scleral buckling procedure, nonetheless new researches and experimentations are essential to further improve the clinical outcomes of such operations. In the author's opinion, the synergy between advanced techniques of medical investigation such as the high-resolution
Conflict of interest
There are no conflicts of interest between the authors and other people or organizations.
Acknowledgements
Dr. Daniela Dolcino, Head of the Ophthalmology Ward at “SS. Antonio e Biagio” Hospital of Alessandria (Italy) is gratefully acknowledged for stimulating the author in writing this article.
In addition, the author wishes to acknowledge Prof. Pietro Rossi, Head of the Ophthalmology Ward at “San Martino” Hospital of Genova (Italy) for fruitful discussions, useful suggestions and really essential help.
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2018, Experimental Eye ResearchCitation Excerpt :Despite the improving technique and reduced risk of intravitreal injections, patient non-compliance persists. To bypass the need for frequent injections, cell-based and biodegradable (hydrogel) implants that act as a reservoir of the therapeutic protein are being developed(Baino, 2010; Tao, 2006). In patients with retinal disease, cell-based implants secreting Ciliary Neurotrophic Factor (CNTF) have provided therapeutic benefit up to 12–18 months (Kauper et al., 2012).