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EditorialVitreous Substitutes: From Tamponade Effect toIntraocular Inflammation

Mario R. Romano,1 Xun Xu,2 and Kenneth K. W. Li3,4

1 Department of Neuroscience, University Federico II, Via Pansini 5, 80131 Naples, Italy2 Department of Ophthalmology, Shanghai First People’s Hospital Affiliated to Shanghai Jiaotong University, Shanghai, China3Department of Ophthalmology, United Christian Hospital and Tseung Kwan O Hospital, Hong Kong4Department of Ophthalmology, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong

Correspondence should be addressed to Mario R. Romano; [email protected]

Received 3 August 2014; Accepted 3 August 2014; Published 1 September 2014

Copyright © 2014 Mario R. Romano et al. This is an open access article distributed under the Creative Commons AttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properlycited.

Vitreous substitutes have been developed both as an intraop-erative and as a postoperative tool for the surgical treatmentof complicated vitreoretinal diseases.The tamponade effect ofthe vitreous substitutes depends on the arc of contact betweenthe agent and the inner retinal surface, whichmainly dependson 4 physical parameters, namely, specific gravity, buoyancy,interfacial tension, and viscosity. As reported by F. Barcaet al., the choice of different intraocular tamponade agentsdepends on the location of retinal break(s), compliance ofpostoperative posture, type of vitreoretinal disease(s), andduration required for the tamponade.Due to the hydrophobicproperty of intraocular tamponade agent, a thin aqueouslayer invariably exists between the tamponade agent andthe retina. This thin aqueous layer is further exaggerated inhighly myopic eyes with posterior staphyloma to becomea pocket of fluid leading to a theoretical reduction of thetamponade effect. However, the debate remains open onwhether it is still worthwhile to use silicone oil in these eyes asX.Valldeperas and J. Lorenzo-Carrero reported contradictingresults. An increased improved anatomical success usingsilicone oil in highly myopic eyes in their study was probablydue to the lower shear retinal stress of the compartmentalizedfluid, scarcely influenced by ocular movements, allowing themacular hole to close and the retinal detachment to reattach.

Based on this hypothesis, K. Isakova et al. reported atheoreticalmodel that predicted the stability conditions of theinterface between the aqueous and a vitreous substitute.Theyshowed that the presence of a thin layer of aqueous between

the retina and intraocular tamponade is responsible for sig-nificant reduction in the retinal shear stress.Their model alsoexplains the instability of the interface leading to the forma-tion of intraocular emulsion that remains the main drawbackof the use of intraocular tamponade agents. Although thetolerance for vitreous substitutes remains generally good,the recent introduction of new mixed compounds, such asheavy silicone oil (HSO), has been associated with relativelyhigh complication rates. In particular, emulsification andsevere inflammatory reactions can lead to poor functionalprognosis. According to L. Ambrosone et al., the spontaneousformation of water-silicone oil is a rare event and the very lowconcentration of surface-active agents cannot account for thesystematic production of emulsions. The authors suggestedthat gravitational instability, originated at the interface bytangential disturbances, plays a more significant role in theformation of emulsions.

Semifluorinated compounds and perfluorocarbon liquids(PFCLs), mainly used only as intraoperative tamponades, aremore prone to induce inflammation and emulsification.

As reported by M. S. Figueroa and D. R. Casas, PFCLshave also been used as postoperative short-term tamponadeagent with development of up to 30% inflammation andretinal infiltration due to foreign-body reaction, sustained bymacrophages that phagocytosed the PFCL droplets. Q. Yu etal. suggested that the physical properties of these tamponadeagents, mainly the low viscosity and surface tension, reducetheir stability and the superficial forces and could lead to

Hindawi Publishing CorporationBioMed Research InternationalVolume 2014, Article ID 159832, 2 pageshttp://dx.doi.org/10.1155/2014/159832

2 BioMed Research International

significant clinical findings such as intraocular inflammation,raised intraocular pressure (IOP), and sticky oil formation.

From a retrospective study conducted on 100 eyes, H.Schwarzer et al. concluded that HSO does not inducealarming complications in the majority of cases. However,they suggested that long-term tamponade with HSO willrequire more frequent follow-up because of its high inci-dence of IOP elevations or intraocular inflammation. Infact D. Odrobina and I. Laudanska-Olszewska reported,at 3 months after the surgery, the topographic evidencesof persistence of small hyperreflective round shaped SOdroplets above the optic nerve and in the cystoid retinalspaces. Despite good anatomical success rate with HSO, J.Prazeres et al. reported a 52% rate of emulsification and40% rate of keratic precipitates in their series with a 16%incident of IOP elevation. Interestingly F. Morescalchi et al.also reported more disturbing complications of HeavySil,a combination of high purity 75% silicone oil 5000 cStand 25% perfluoroalkyloxyoctane, including early optic discswelling, retinal edema, and intraretinal inflammation withdiffuse narrowing of arteries and veins. The challenges oftamponade research remain the provision of a wider arcof tamponade and long-term intraocular permanence withinertness of the compound while at the same time providinguniform transport of nutrients to intraocular tissue. Despiteyears of effort, we still remain far from providing goodsolutions for these “solutions.” S. Donati et al. reported that apromising alternative to the present compounds could be thesmart hydrophilic polymers. They are capable of swelling byabsorbing its own weight in water, with further possibilitiesof a thermosetting and with interactive properties with theenvironment (glucose, glutathione), pH, and light. Theseproperties allow the molecules to be modulated inducingthe gelification, better drug diffusion, and increased gelexpansion. Perhaps the real solution for an ideal tamponadeagent may involve a paradigm shift away from traditionalagents.

Mario R. RomanoXun Xu

Kenneth K. W. Li

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