Ординатура / Офтальмология / Английские материалы / Textbook of Vitreoretinal Diseases and Surgery_Natarajan, Hussain_2008
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Textbook of Vitreoretinal Diseases and Surgery
COMPARISON WITH ICG
Trypan blue, in concentration from 0.06% to 0.20%, stains the ILM but less intensely and uniformly than ICG. However it has been postulated by some to be a safer option than ICG.
A recent randomized control trial20 to test this hypothesis found no difference in the structural or functional outcomes between the two. However, this was a pilot study with a sample size of 20 patients in each arm and no predetermined end point for efficacy, but had the advantage of testing vision, visual field and OCT on all patients. The obvious next step is an adequately sized study for answering this question.
Safety in clinical reports has been established but In vitro studies have shown conflicting results on the safety of intravitreal TB injections. Due to its solubility it has been proposed that TB has less acute toxicity to cultured RPE cells compared to ICG and IfCG, however it has been reported to have more chronic toxicity. RPE cell culture studies indicate a potential increase in apoptosis even after application of lower concentrations of 0.05% of Trypan blue for 5 minutes. In contrast, no direct TB-related toxic effects were observed in a postmortem study, in rabbit eyes, and in several clinical trials. Carcinogenic and teratogenic properties of trypan blue have been described in animal models21 and long-term side effects are unknown in humans, so far.
Patent Blue
Patent blue (PB) is an anionic dye and is orange in acid conditions and blue in alkali. It has been used to assist in fungus identification and removal of lymph nodes. The dye has been recently certified for capsule staining during cataract surgery at the concentration of 2.4 mg/ml. The carcinogenic and mutagenic effects described with systemic use of TB in laboratory animals have not been seen for PB.
Patent blue is reported to provide better visualization of the ERM in comparison to the ILM, and no visual field defects or visible RPE-changes were observed postoperatively. In vitro studies have revealed conflicting data on the retinal safety of the dye and the safe dose is yet unknown.
Sodium Fluorescein
Sodium fluorescein (SF) is an anionic hydrophilic dye and was found to be highly safe for fundus angiography in a concentration of 5- 25% solution, even when leakage through the retina occurred. Because of its hydrophilic properties, SF is highly absorbed by the vitreous gel. The use of sodium fluorescein in vitrectomy was reported by Abrams and co-workers22 as early as 1978. Das and Vedantham23 showed that intravitreal SF injectable dye improved the visualization of clear vitreous fibers through a green coloring during chromovitrectomy, and no complications were noticed in their clinical series. To date, the main indication of SF in chromovitrectomy remains in the vitreous, while future clinical investigations should determine its role in ILM staining. There is a lack of data evaluating retinal toxicity of intravitreal sodium fluorescein in human eyes.
Brilliant Blue G (BBG)
178 Also known as Coomassie or acid blue, it is a synthetic dye and a food additive having been used intraocularly for anterior lens capsule staining and chromovitrectomy.
Role of Biostains in Vitreous Surgery
In humans studies, BBG was used in an iso-osmolar solution of 0.25 mg/ml to stain ILM for ERM and macular hole surgery, with 85% of patients improving at least two Snellen lines. No clinical signs of toxicity have been observed in the long-term24. In rat and primate eyes no significant retinal toxicity has been reported both structurally and functionally. Due to its high affinity to ILM, BBG is an alternative to ICG and IfCG for ILM staining although toxicity data are presently limited.
Bromophenol Blue (BrB)
BrB has been proposed as an alternative biostain for chromovitrectomy. RPE culture studies demonstrated that among six biological stains (light green yellowish, E68, Chicago blue, rhodamine, rhodulinblau-basic), BrB stained better the ERM, ILM, and did not cause RPE toxicity at concentrations of 0.2 and 0.02%.25 Further studies in rodent and porcine eyes demonstrated that BrB at concentrations of 0.5 and 0.02% promoted less significant retinal toxicity in comparison with three other vital dyes.26
Triamcinolone Acetonide
Triamcinolone acetonide (TA) is a relatively insoluble steroid that is used for local treatment of several ocular diseases, such as ocular inflammation, macular edema and age-related macular degeneration. TA was added as an alternative stain for chromovitrectomy based on experience from other ophthalmic applications.
TA injections for chromovitrectomy have been performed with 0.5 mL of the 40 mg/ml commercial product. The white steroid is used to visualize the vitreous gel and posterior vitreous cortex. The high affinity of TA to the vitreous particles and the fine ILM was postulated as the result of the steroid precipitation. Besides aiding in the visualization of preretinal tissues, TA application in chromovitrectomy may improve surgical outcomes by decreasing the break down of blood-ocular barrier and reducing the chance of preretinal fibrosis. While TA was proposed for visualization of the ILM and vitreous, further investigation on its exact target tissue during chromovitrectomy is required. Intraoperative identification of the preretinal membranes may be hindered by the deposition of TA particles.
During chromovitrectomy, TA is found to deposit in the macular or submacular space for several days after its intravitreal application, although no clinical signs of retinal damage were observed. Researchers have proposed that the toxic substance in TA is the vehicle, rather than the steroid itself.27 Probably, to minimize the risks, TA should be filtered to generate a vehicle-poor suspension.
This steroid has shown no toxic effects and complications associated with intravitreal injection such as glaucoma occur less frequently due to the removal of most of the steroid by the end of the surgery in chromovitrectomy. The risk of endophthalmitis associated with intravitreal injection of TA is related to the injection procedure and not an independent complication of triamcinolone in the vitreous. This lack of toxicity remains the most remarkable advantage of staining preretinal membranes with TA.
Fluorometholone Acetate
Fluorometholone acetate is a synthetic fluorinated glucocorticosteroid and a creamy ophthalmic |
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suspension that can be prepared for use. Hata et al.28 investigated the safety of intravitreal or subretinal |
Textbook of Vitreoretinal Diseases and Surgery
Fluorometholone acetate to the morphology and function of the retina in rat and primate eyes for possible use in chromovitrectomy. They concluded it was a useful alternative to triamcinolone acetonide during chromovitrectomy.
Vitreoretinal Internal-limiting Membrane Color Enhancer (VINCE)
A new dye applicator named VINCE has been recently released to allow painting of preretinal tissues. The painting brush is constructed of a silicone tube connected to a 20 gauge metal cannula. The dye diluted in fluid is provided by connection to a silicone disposable cartridge containing the vital dye. The flexible dye-filled tip smoothly traverses the retinal surface, enabling the dye to paint with a minimum of dye. The novel approach should enable vitreoretinal surgeons to stain the fine delicate semitransparent tissues on the retinal surface, avoiding an excessive and unselective staining of the entire retinal surface 29
Conclusion
Visualization of preretinal structures and membranes has become easier due to availability of various dyes. ICG has been the “pioneer dye” for ILM-peeling. Current recommendations for ICG-assisted chromovitrectomy consist of injection in concentrations as low as possible, short incubation times and no concomitant light exposure; a similar approach is warranted for novel vital dyes. Alternatives to ICG are IfCG and Brilliant blue Green. For ERM removal the current preferance is trypan blue, with alternative options being patent blue and Bromophenol blue. Triamcinolone acetonide is preferred for vitreous visualization, while sodium fluorescein and fluorometholone acetate are good alternatives approaches.
References
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1. |
Mester VKF. Internal Limiting Membrane Removal in the Management of Full-Thickness Macular Holes. Am J |
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Ophthalmol 2000;129:769-77. |
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2. |
Kang HKCA, Beaumont PE. The macular hole: report of an Australian surgical series and meta-analysis of the |
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literature. Clinical and Experimental. Ophthalmology 2000;28:298-308. |
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3. |
D Tognetto RG, G Sanguinetti, and the macular hole surgery study group. Internal Limiting Membrane Removal |
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during Macular Hole Surgery Results of a Multicenter Retrospective Study. Ophthalmology 2006;113:1401-10. |
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4. |
AKH Kwok TYYL, W Man-Chan and DCF Woo. Indocyanine green assisted retinal internal limiting membrane |
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removal in stage 3 or 4 macular hole surgery. Br J Ophthalmol 2003;87:71-4. |
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5. |
Kwok AKLT, Yuen KS, Tam BS, Wong VW. Macular hole surgery with or without indocyanine green stained |
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internal limiting membrane peeling. Clin Experiment Ophthal 2003;31:470-5. |
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6. |
Sheidow TG BK, Holekamp N, et al. Outcome results in macular hole surgery: an evaluation of internal limiting |
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membrane peeling with and without indocyanine green. Ophthalmology 2003;110:1697-701. |
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7. |
Lochhead J JE, Chui D, et al. Outcome of ICG assisted ILM peel in macular hole surgery. Eye 2004;18:804-8. |
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8. |
Ando F SK, Ohba N, Hirose H, Yasui O. Anatomic and visual outcomes after indocyanine green-assisted peeling of |
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the retinal internal limiting membrane in idiopathic macular hole surgery. Am J Ophthalmol 2004;137:609-14. |
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9. |
Jackson TL HJ, Knight BC, et al. Safety testing of indocyanine green and trypan blue using retinal pigment |
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epithelium and glial cell cultures. Invest Ophthalmol Vis Sci 2004;45):2778-85. |
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10. |
Ho JD TR, Chen SN, Chen HC. Cytotoxicity of indocyanine green on retinal pigment epithelium: implications for |
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macular hole surgery. Arch Ophthalmol 2003;121:1423- 9. |
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11. |
Haritoglou C GC, Schaumberger M, Ehrt O, Gandorfer A, Kampik A. Macular changes after peeling of the internal |
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limiting membrane in macular hole surgery. Am J Ophthalmol 2001;132:363-8. |
Role of Biostains in Vitreous Surgery
12.al DMe. Indocyanine Green–Assisted Internal Limiting Membrane Peeling for Macular Holes To Stain or Not To Stain? Retina 2005;25(4):395-401.
13.Eduardo B, Carsten H, Stefan MME. Mechanisms Of Intravitreal toxicity of indocyanine green dye, Implications for Chromovitrectomy. Retina 2007;27(7):958-70.
14.Rodrigues E, Meyer, CH, et al. Vital dyes for chromovitrectomy. Curr Opin Ophthalmol 2007;18:179-87.
15.Kodjikian LRT, Halberstadt M, et al. Toxic effects of indocyanine green, infracyanine green and trypan blue on the human retinal pigmented epithelium. Graefes Arch Clin Exp Ophthalmol 2005;243:917-25.
16.Jackson TL VB, Knight BC, et al. Safety testing of infracyanine green using retinal pigment epithelium and glial cell cultures. Invest Ophthalmol Vis Sci 2004;45:3697-703.
17.Hiebl WGB, Meinert H. Substances for staining biological tissues: use of dyes in ophthalmology. Klin Monatsbl Augenheilkd 2005;222:309-11.
18.Stalmans PFJ, Van Ginderdeuren R, Van Lommel A, Melles GRJ, Veckeneer M. Double vital staining using trypan blue and infracyanine green in macular pucker surgery. Br J Ophthalmol 2003;87:713-6.
19.Jackson TLKA, Laidlaw AH, Aylward W. Identification of retinal breaks using subretinal trypan blue injection. Ophthalmology 2006.
20.Julia Beutel GD, Andreas Ziegler, Hans Hoerauf. Internal Limiting Membrane Peeling with Indocyanine Green or Trypan Blue in Macular Hole Surgery A Randomized Trial. Arch Ophthalmol 2007;125:326-32.
21.Bressman PLSF. Neural abnormalities induced by selected chemical agents. Proc Okla Acad Sci 1976;56:10-14.
22.Abrams GW TT, Machemer R. An improved method for practice vitrectomy. Arch Ophthalmol 1978;96:521-5.
23.Das TVV. Visualization of clear vitreous during vitreous surgery for macular hole: a safety and efficacystudy. Clin Exp Ophthalmol 2004;32:55-7.
24.Enaida HHT, Hata Y, et al. Brilliant blue G selectively stains the internal limiting membrane/brilliant blue G-assisted membrane peeling. Retina 2006;26:631-6.
25.Haritoglou CYA, Freyer W, et al. An evaluation of novel vital dyes for intraocular surgery. Invest Ophthalmol Vis Sci 2005;46:3315-22.
26.Schuettauf FHC, May CA, et al. Administration of novel dyes for intraocular surgery: an in vivo toxicity animal study. Invest Ophthalmol Vis Sci 2006;47:3573-8.
27.Morrison VL KH, Cheng L, et al. Intravitreal toxicity of the kenalog vehicle (benzyl alcohol) in rabbits. Retina 2006;26:339-44.
28.Hata Y, Enaida H, Sassa Y, et al. Preclinical investigation of fluorometholone acetate as a potential new adjuvant during vitreous surgery. Graefes Arch Clin Exp Ophthalmol 2007; 245(7):1019-25 .
29.Meyer CH. A novel applicator for the selective painting of preretinal structures during vitreoretinal surgery. Graefes Arch Clin Exp Ophthalmol 2005;243:487-9.
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Textbook of Vitreoretinal Diseases and Surgery
Introduction
Modern vitreous surgery was largely the result of pioneering effort of Robert Machemer. During the process of further improvement till today, vitreoretinal surgical techniques and instrumentations has facilitated the surgical management of vitreoretinal pathologies. However, besides surgical instrumentation, optimal viewing of the surgical field is one of the most important factors which can influence the surgical outcome. This viewing system includes a very good operating microscope and a contact or a non-contact optical lens system.
The older contact lens (either assistant held or those fixed to the episclera) does aid in the surgical viewing but limited field of view is the major disadvantage. Peripheral retina can only be seen with indentation. Besides this, difficulty in keeping the lens properly aligned during surgery, limited access to the limbus, air bubble or blood film coming beneath the lens system are the other drawbacks. Limited use in small pupil as well as poor visualization during fluid gas exchange in phakic or pseudophakic eyes are added disadvantages.
Vitreous microsurgery has made a tremendous progress in the last couple of decades. The wideangle viewing systems provide a panoramic view of the surgical field up to the ora serrata. Though the initial cost may be higher and might demand a steeper learning curve, it has several advantages over the contact lenses. Because of the ease of operation, overall surgical time is less. Besides, it has greater depth of field and easy view during fluid-gas exchanges.
Wide-angle viewing system is mainly of two types:
NONCONTACT
•BIOM with SDI (Binocular Indirect Ophthalmomicroscope with Stereoscopic Diagonal Inverter)
•EIBOS (Erect Indirect Binocular Ophthalmo-microscope System).
CONTACT
•VPFS (Vitreous Panfunduscope System)
•CWF (Contact Wide Field System)
•AVIS (Advanced Visual Instrument System)
•ROLS (Reinverting Operating Lens System).
Though these conctact lens systems can achieve up to 150° field of view and great optical resolution, they might cause change in intraocular pressure, corneal trauma and perform poorly in steep corneal curvature. The noncontact systems can avoid most of the above problems, the trade – off being that the optical resolution is of inferior quality to the contact systems. Moreover, systems like EIBOS cannot be used in all microscopes.
All the above contact or non-contact viewing systems produce an indirect image, hence necessitating the incorporation of image inverter system in the microscope which would reinvert the image in the surgical field. This image inverter system is called the Stereoscopic Diagonal Invertor (SDI).
Stereoscopic Diagonal Invertor (SDI)
SDI is an inverter system which is incorporated in the operating microscope to reinvert the inverted image produce by a wide-angle viewing system (Figure 16-1). This system was first developed by
184 Spitznas and Reiner.1
Wide-angle Viewing System in Vitreoretinal Surgery
FIGURE 16-1: Stereoscopic diagonal invertor
The SDI has an internalized prism system with nearzero light escape to achieve maximal illumination and light intensity. It provides stereoscopic erection of the inverted image and can be activated by electrical hand or footswitch or manually. It can be adapted to different types of microscopes.
Indirect Surgical Non-Contact Lens Systems
BINOCULAR INDIRECT OPHTHALMOMICROSCOPE (BIOM)
BIOM (Figure 16-2) manufactured by OCULUS, Optikgeraete, GmBH, (Wetzler, Germany) was an invention of Prof Spitznas where he incorporated the principle of indirect ophthalmoscopy in the operating microscope.2 As BIOM provides an inverted image, it can only be used in conjunction with
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FIGURE 16-2: Binocular indirect ophthalmomicroscope
Textbook of Vitreoretinal Diseases and Surgery
SDI. BIOM can be mounted with case on the microscope and can be shifted in to the beam path when required. It has a mounting plate secured to the lower surface of the operating microscope by a flange and a dovetail. There is a condensing lens on the top of an indirect viewing tower and a small objective lens combined to a retractable extension arm. Manual rotation of a knurled-knob attached to the extension arm facilitates upward or downward movement of the objective lens for finer adjustments while focusing.
The advantages of BIOM are:
1.Wide angle of view (90°-110°)
2.Good stereopsis and depth of focus
3.Wide angle of view even with small pupil
4.Non contact system, hence there is no risk of corneal touch.
5.The eye can be rotated allowing the view of the peripheral fundus
6.Good view even in air filled aphakic, phakic or pseudophakic eyes.
BIOM 3
It can be installed very fast and can be swung into the path of rays when desired. Advantages are:
1.Large depth and sharpness.
2.Simple to focus.
3.All components can be sterilized.
4.No load on cornea.
Instrumentation and Maneuvering
A clear visual axis with a minimum pupillary diameter of 2.5 mm is required. The operating table should be as low as possible with comfortable leg position for the surgeon.
After the standard pars plana ports are made and anterior vitrectomy done under the normal microscope light, the light is turned off and endo-illuminator is switched on. The SDI foot pedal is activated and the microscope slowly lowered. Magnification is achieved by using the zoom system of the operating microscope or by lowering the microscope so that the objective lens is closer to the cornea.
The knurled-knob should be started about an inch below its highest setting. When the knob is rotated anticlockwise the small objective lens moves up but focuses down and a clockwise movement will cause the objective lens to go closer to cornea and will focus upward. To achieve the initial focus, the endo-illuminator in the vitreous should be aimed at the disc. After the surgeon has decided about the adequate magnification, he adjusts the knurled knob to achieve the fine focus. Once the disc and the posterior pole is properly focused, the periphery is also viewed by manipulating the eye and the X-Y movement of the microscope.
During the surgery, if the surgeon wants to shift to a contact lens the assistant has merely to flip the BIOM up to move away from the visual axis.
Sterilization
The BIOM can be sterilized with gas or autoclaved. The lenses can be sterilized with ethylene oxide 186 (ETO) or Cidex. The SDI is incorporated into the microscope and is not sterile.
Wide-angle Viewing System in Vitreoretinal Surgery
FIGURE 16-3: Erect indirect binocular ophthalmomicroscope system
EIBOS
EIBOS (Figure 16-3) is a non-contact wide angle viewing system which works on the same principle as BIOM, except that it has an integrated reversing optics and hence does not require SDI. This has disadvantage that the inverter cannot be used independently with miniature indirect contact lens, unlike BIOM. But, it allows the use of direct contact lenses as it can be flipped up and out of visual axis.
Sterilization
The one piece design does not allow sterilization of the entire unit, and it must be draped with a sterile covering, though the objective lens can be sterilized.
Wide-angle Indirect Surgical Contact Lens Systems
VPFS (VITREOUS PANFUNDOSCOPE SYSTEM)
VPFS is a modified Rodenstock panfundoscope with a portion of the lens trimmed off to allow easy introduction of instruments into the vitreous cavity without disturbing the lens. The system provides an inverted image, and hence SDI is necessary. It gives an observation angle of 130°-150°. It can be stabilized with a handle held by an assistant or a link chain. The major disadvantage is its weight (28 gm), which appears to be heavy compared to other lenses, hence often difficult for the assistant to hold the lens for prolonged period of time.
CWF (CONTACT WIDE FIELD LENS) |
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These wide field contact lenses (Figure 16-4) provide inverted images, hence have to be used with |
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SDI. It provides surgical field of view of 120°-130°. It is lighter (4 gm) and smaller than VPFS. It can |
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be held by handle or standard lens ring. |
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