Retinal Detachment Repair Outlook for the Future

William R. Freeman

Due to the pioneering work of many ophthalmologists, including Gonin, Lincoff, and others, the basic pathophysiology of rhegma-togenous retinal detachment has been established. A retinal tear is caused by a vitreous detachment and traction on the retinal tear, and peripheral retina is responsible for fluid currents, which go through the break and detach the retina. More fundamental questions remain to be answered and will have important implications for our ability to detect, prevent, and treat rhegmatogenous retinal detachment and its complications.

Many controversies remain regarding surgical repair of this disease. This controversy is complicated due to a lack of prospective randomized clinical trials comparing different methods of

Fig. 10.1. Radial sponge has cured a retinal detachment without the need for drainage

Fig. 10.2. Balloon buckle in place closing retinal break

treatment. For this reason, much of the debate revolves around theory and philosophy, not hard clinical data. There is little doubt that the most minimal operation that would be highly effective would be the procedure of choice. Highly effective should include minimal complications and inconveniences, such as the induction of refractive error (Lincoff, Kreissig) [1].In this regard, the classical radial sponge (Fig. 10.1) or the balloon buckle (Fig. 10.2) remains the gold standard for many, due to the extraocular nature of the surgery and low complication rate. These procedures shared in common extraocular placement of a bulky device,which reapposes or nearly apposes the neurosensory retina and retinal pigment epithelium/choroicapillaris. By bringing these two layers in close proximity, the rate of fluid flow under the retina is limited and the pumping action of the pigmented epithelium overcomes the leakage of fluid through the retinal tear; thus the retina reattaches. The use of retinopexy is a backup procedure to further prevent fluid leakage, causing a permanent scar or adhesion of the two layers (Figs. 10.3 and 10.4). Unfortunately, segmental buckling is not

Fig. 10.3. Horseshoe retinal tear with vitreous traction
Fig. 10.4. Laser retinopexy surrounding horsehoe retinal tear

applicable to all cases. For example, very large posterior tears are difficult to externally tamponade. Giant retinal tears do not respond to external buckle procedures because one cannot reappose the layers; the retina is merely pushed inward. In addition, the procedure can only work when all retinal breaks can be well visualized (Fig. 10.5). This may be difficult in eyes with media problems or

Fig. 10.5. A well-visualized peripheral retinal tear

when intraocular lenses, retained lens material, and other difficulties preclude identification of all retinal breaks [2].

Let us now consider the evolution of surgical techniques in the future. One of the many obstacles to performing minimal buckling techniques, as well as pneumatic retinopexy and the balloon buckle, is the difficulty in finding all retinal breaks in certain eyes as outlined above. New techniques will evolve to allow visualization of the peripheral retina, which will make break identification more universally possible.

New imaging techniques, such as ballistic light imaging (Fig. 10.6), hold the promise of high-resolution trans-scleral optical images [3]. Ordinarily, it is not possible to view clearly through a semi-transparent tissue, such as the thin sclera. A degraded image results due to scattered light. Light passes through the tissue, but scatter presents the ability to obtain a clear image. Scattered light is delayed compared with non-scattered light; however, the amount of delay is extremely small. The ability to fabricate femtosecond optical filters can theoretically gate out this scattered light based on time differences. In the future, such ballistic light imaging promises to be a non-invasive way of examining the vitre

Trans Scleral Retinal imaging

Fig. 10.6. Trans-scleral retinal imaging (scattering media)

ous base area at high resolutions and will be particularly helpful in cases of small pupils, intraocular lenses with anterior capsular phimosis, and other conditions. A trans-scleral imaging probe could be used with topical anesthesia and would allow thorough examination of the peripheral retina at high magnification, similar to how ultrasound is currently used. Additional imaging techniques, which may be applicable to detect retinal breaks, include higher resolution and intraoperative ultrasound biomicroscopy that is easier to use (Fig. 10.7). Current techniques are limited by awkwardness of probe placement and large instrumentation; but, this should change in the future. The use of ultrasound will not actually visualize retinal breaks optically; however, clearly, breaks can be identified by ultrasound, particularly using high-resolution techniques. Ophthalmoscopic techniques that involve visualization of the retina through the optical media of the eye are also evolving;

Fig. 10.7. Ultrasound biomicroscopy images peripheral retinoschisis

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Fig. 10.8. Pseudo-color wide-angle scanning laser may allow screening for retinal detachment

Fig. 10.8. Pseudo-color wide-angle scanning laser may allow screening for retinal detachment the wide-angle pseudo-color SLO and related techniques (Fig. 10.8) may allow noninvasive screening for retinal detachment by primary care health care providers, which will allow us to treat detachments prior to macular involvement [4]. Such wide-angle SLO devices currently do not allow reliable imaging of structures anterior to the equator of the globe; however, they can detect retinal detachment early and, if set up as easy to use screening devices, will allow

Fig. 10.9. Vitreous endoscopy allows visualization of far anterior structures such as the ciliary body and pars plana

patients to be treated at earlier stages of the detachment, when the macula has not been affected, and the rate of success is higher. High-resolution scans, such as those used now for magnetic resonance imaging (MRI) scanning of the head and neck vessels, may become applicable to the retinal periphery and help with break localization and prophylaxis issues. Functional MRI may increase our understanding of peripheral retinal tissues as well. This technique may allow insights into vitreous and peripheral retina metabolism and degeneration and may help allow us to predict those at risk for early vitreous detachment and retinal detachment [5]. Intraoperative techniques will evolve, and these will include even better wide-angle viewing systems and the future use of stereoscopic endoscopy, which will allow the advantages of stereoscopic viewing and tissue manipulation currently not possible with grin and other forms of endoscopy [6] (Fig. 10.9). New lasers may allow us to transect the flaps of flap tears, thereby relieving traction; if this is possible, retinopexy may not even be required, and minimal manipulations to close the break may be possible. Electron knives and other devices will be able to be used intraoperatively to allow tissue to be cut in a non-traumatic and, therefore, non-pro-inflammatory manner.

Fig. 10.10. Accommodating intraocular lens (IOL): two positions. IOL moves with ciliary body contraction

In the future, the incidence of pseudophakia will be much higher. Anterior segment surgeons will be implanting accommodating intraocular lenses (IOLs) to treat presbyopia (Fig. 10.10). The development of this and other lens replacement devices to treat presbyopia and, potentially, low vision will increase the number of eyes that have had cataract surgery, and this will likely increase the prevalence of retinal detachment [7].The technologies of accommodating IOLs being currently developed do entail an intact posterior capsule and the use of capsulorhexis, so the difficulties of viewing the peripheral retina using our current technologies will need to be addressed (Fig. 10.11). Multizone phakic

Fig. 10.11. Phimosis of anterior capsule limits peripheral retina visualization
Fig. 10.12. Several types of multifocal intraocular lenses

IOLs for presbyopia will also complicate our view in the future as their use becomes widespread (Fig. 10.12).

Let us also consider clinical trials of the future. Clearly, the current clinical trials methodologies in use are awkward, expensive, and extremely personnel intense. Anybody who has participated in a definitive National Institutes of Health or drug company trial knows this. These trials take years to plan and, by definition, cannot test cutting edge techniques and are not applicable to techniques in evolution. The paperwork and infrastructure currently required to perform high-quality clinical trials is extremely cumbersome and inefficient. Let us consider the concept of the Secure VPN or Virtual Private Network (Fig. 10.13). Consider that groups of surgeons will be securely networked and will have the power to

Fig. 10.13. Virtual personal collaborative networks

query the sum experience of the group. Imagine that data will be ferreted out because all data will be computerized and that sophisticated programs, worms, and internet cookies will allow compilation of preoperative data, procedure data, and outcomes, including standardized visual acuity. In addition, patients will be able to be contacted to determine quality of life outcomes. Although all procedures may not be standardized, standardization can evolve and may allow us to collect real time data and outcomes as they occur in patients throughout the United States or the world. One can only imagine what the ability to determine success and outcomes nationally and internationally will do to our ability to advance and understand surgical techniques when such information will be available with minimal effort in comparison with today's clinical

Fig. 10.14. Stereo photograph of old giant retinal tear with cyst. Fellow eyes are at high risk trial techniques. The network of academic collaborations will be able to be formalized, and individual physicians will be able to collaborate seamlessly. Clinical science will also advance as we learn more about genetics and other cofactors that predispose to retinal detachment. Our knowledge of who is at high risk for retinal detachment remains rudimentary. We know that fellow eyes are at risk, particularly in certain conditions (Fig. 10.14); but there remains great controversy as to the role of prophylaxis of peripheral retinal lesions that may be related to retinal detachment. Clearly, as we learn more about risk factors, the role of different types of prophylaxis will become better understood. This, in conjunction with more facile ways to perform clinical trials and surveys, will allow preventive treatment algorithms to evolve.

The pioneering work of Sawa and Tano in Osaka has shown us that it is not instrumentation of the vitreous itself, but infusing of fluids that is likely the cause of nuclear sclerosis and cataract induction after vitrectomy [8]. As vitreous surgery is applied to eyes with relatively good visual potential, the side effect of cataract is more clinically important. Our indications for vitrec-tomy in the repair of retinal detachment and for other diseases may expand considerably if we can avoid cataract formation in these eyes.

Fig. 10.15. Proliferative vitreoretinopathy

Finally, let us not forget drug treatment and pharmacotherapy in the area of retinal detachment. One of the main nemeses of retinal detachment surgeons is proliferative vitreoretinopathy (PVR) (Fig. 10.15). This is the result of a biological process gone awry. Cellular elements already in the eye and, in some cases in the blood, proliferate, lay down collagen, and cause collagen contraction. This biological process results in membrane formation, recurrent retinal detachment, and macular pucker. There has been widespread study of the classical antiproliferatives to reduce the risk of PVR or to limit it. These drugs, such as 5FU and Dauno-mycin, are intrinsically toxic. We will soon be using the techniques of molecular biology and intelligent drug design to create more sophisticated anti-proliferative drugs. Such drugs may take the shape of the hammerhead ribozyme, which cleaves mRNA involved in proliferation and other processes (Fig. 10.16). These types of drugs are similar to antisense, but unlike antisense are recycled intracellularly [9]. Thus, they may be able to be applied into the eye and remain active in cells for months or longer. There will be other ways to block this biological process, including acting on inflammation, proliferative pathways, and cytokine pathways. The

Cleaved Target RNA

Degraded

Fig. 10.16. Ribozyme cleavage of RNA associated with cell proliferation

Cleaved Target RNA

Point of cleavage

Fig. 10.16. Ribozyme cleavage of RNA associated with cell proliferation role of other cellular pathways in proliferation and cellular damage is being explored by many basic scientists. We have yet to take full advantage of molecular drug design to inhibit the pathways involved in PVR. Similarly, as we elucidate the roles of cytokines and develop non-toxic inhibitors of these molecules, we can use this knowledge to inhibit (Fig. 10.17).

Similarly, our understanding of what damages the retina after retinal detachment and new drugs to stabilize this delicate neural tissue will be developed, which will also result in better visual outcomes, even in more long-standing macula off retinal detachment. We can now design functional peptide-based drugs and will be able to incorporate signaling peptides into nanofibers (Fig. 10.18) and engineer an instructional matrix for stem cells to replace and repopulate maculae with damaged photoreceptor elements [10]. In vivo fluorescence staining and other cell and molecular techniques are allowing us to visualize pathology in living cells as we see here, using fluorescence microscopy in vivo to follow cell motion with cytoskeletal marker staining. Understanding these fundamental processes will help prevent and treat intraocular proliferative diseases, such as PVR.

Fig. 10.17. Small molecule inhibits matrix metalloproteinase enzyme involved in angiogenesis
Fig. 10.18. Cross-linked self-assembling peptide nanofibers

It is impossible to know what the future holds. The ever-accelerating progress of scientific discovery and the desire of vision scientists and ophthalmologists to help patients will assure us that new and exciting tools and techniques will evolve to take us to where we have not been or even dreamt before.

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