11
QUESTION
WHAT VISUALIZATION AGENTS ARE USED DURING VITRECTOMY SURGERY? AND WAIT, TELL ME ABOUT THE INTRAOCULAR TAMPONADE OPTIONS!
Sean M. Platt, MD
Sophie J. Bakri, MD
Visualization Agents
The use of visualization agents is very popular with vitreoretinal surgeons to help visualize near-transparent tissues such as the vitreous, epiretinal membrane (ERM), internal limiting membrane (ILM), and neurosensory retina. Commonly referred to as chromodissection, or chromovitrectomy the use of different dyes can selectively accentuate the target tissue, allowing the surgeon to visualize the layer and extent of peeling. We discuss the 4 most commonly used visualization agents: triamcinolone, indocyanine green (ICG), Brilliant Blue G (BBG), and Trypan Blue (Table 11-1).
Triamcinolone acetonide (Triescence) is composed of particles in suspension, which, when injected intravitreally, are trapped within the vitreous body. This helps the surgeon visualize the vitreous itself, whether there is a posterior vitreous detachment, the boundaries of the vitreous, and an ERM when present.1 Triamcinolone is approved for intraocular use and is not associated with retinal toxicity. Retained triamcinolone may cause elevation of intraocular pressure and should be used with caution in steroid responders or in patients with glaucoma and may contribute to cataract progression.
ICG is a popular visualization agent given its ILM selectivity and more pronounced staining effect compared to BBG (not US Food and Drug Administration [FDA]–approved, but commonly used outside the United States).2 There is also the additional benefit of the tissue-dye interaction allowing the ILM to peel more easily, thus potentially minimizing damage to the underlying retinal layers.
Table 11-1
Visualization Agents Used in Vitreoretinal Surgery
BBG also selectively stains the ILM, but not with the same intensity when compared to ICG. BBG is considered to have high biocompatibility in the eye, and thus binds well to the target tissue, is nontoxic, and degrades quickly with time. BBG is strongly absorbed at wavelengths in the visible spectrum compared to ICG, which has maximal absorption in the near infrared range. What this means is that a higher concentrations of ICG is needed compared to BBG to produce the desired effect.
Trypan Blue is used as a visualization agent to selectively stain ERM.3 Generally, ERMs are easier to visualize under normal viewing conditions and therefore do not need to be stained. If using ICG, ILM stains but not ERM, and thus there is negative staining that identifies the ERM. However, Trypan Blue is useful in staining complex ERMs in the macula and periphery, especially those due to proliferative vitreoretinopathy (PVR), and those that seem unusually adherent. It can also help differentiate the ERM from residual posterior cortical vitreous to ensure complete removal of an ERM.
Depending on the study, dyes have been linked to toxic effects, such as visual field defects and decreased functional outcomes. Measures to limit toxicity include using a low concentration, limiting dye time in the eye, limiting peeling time, and limiting light intensity by lowering the light, and limiting exposure by moving the light pipe away from the macula.4
Dyes can be injected in an air- or fluid-filled eye. If you are injecting into a fluid-filled eye, you will need to mix the dye in a solution heavier than water, such as glucose or dextrose. Injecting into an air-filled eye typically results in a darker stain due to a higher effective concentration of dye.
Gas Tamponade
Using gas as an intraocular tamponade has been an important adjunct to treating retinal pathology from retinal detachments to macular holes. Many different gases are used (Table 11-2), and the choice of gas depends on the duration of tamponade desired by the surgeon.
In most instances, the gas you choose will be based on how long you need the retina approximated to the retinal pigment epithelium (RPE) for the chorioretinal adhesions to form. The force of the bubble promotes apposition of the neurosensory retina against the RPE. In eyes with a rhegmatogenous retinal detachment, this contact is important as chorioretinal adhesions form because it keeps the retina attached and keeps fluid out of the subretinal space. The strong surface tension of a bubble allows the bubble to stay coalesced as one bubble and prevents the bubble from migrating through small retinal defects into the subretinal space.
Table 11-2
Intraocular Gases Used For Tamponade During Vitreoretinal Surgery
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