Papadopoulou Caterina Thessaloniki – GREECE

catepapgr@hotmail.it www.tvrs.gr

OCT was first reported by Huang et al. in 1991.In vivo retinal imaging was first demonstrated in 1993, and early studies in 1995 provided the first demonstration of OCT imaging of the normal retina and of macular pathology.OCT is a noninvasive (non contact) medical imaging technology similar to ultrasound and MRI that provides high resolution, cross sectional images of the retina and the retina nerve fiber layer and the optic nerve head.In medicine, the technique has been compared to an in-vivo optical biopsy.

TIME DOMAIN OCT (TD-OCT) : is the early version of this technology.Low-coherence infrared light (800-1310nm) is transmitted into the eye through use of an interferometer (Michelson type interferometer)The infrared light is transmitted through the pupil and then penetrates through the transparent nine layers of the retina. Subsequently, the light backscatters and returns through the pupil, where detectors can analyze the interference of light returning from the layers of the retina compared with light traveling a reference path (mirror). An algorithm mathematically uses this information to construct a gray-scale or false-color image representing the anatomy of the retina

Uses a moving reference mirror for measuring the time it takes for the light to be reflected. This relatively slow mechanical process limits both the amount of data that can be captured as well as image quality.TD-OCT data is acquired at approximately 400 axial scans (or A-scans) per second with an axial resolution of 8-10μm.Because of the eye motion, it is not feasible to use TD-OCT to precisely map retinal tissue in three dimensions

In 2006, the first commercially available SD-OCT system was introduced.SD-OCT uses a significantly faster non mechanical technology.SD-OCT employs detection of the light echoes simultaneously by measuring the interference spectrum, using an interferometer with a high speed spectrometer.This technique achieves scan rates of 20.000-52.000 A scans per second and a resolution of 5-7μm in tissue.The increase speed and number of scans translates into higher resolution and better chance of observing disease

Improved resolution Improved acquisition speed Reduces motion artifacts Digital processing not required to align adjacent axial

scans = More accurate retinal scans 3D views More accurate segmentation Precise registration/orientation

Time Domain OCT400 axial scans per second (Zeiss Stratus-2002)8-10μm axial resolution

Spectral/Fourier Domain OCT-spectrometer25.000-50.000 axial scans per second (2006)5-7μm

Next Generation Spectral/Fourier OCT70.000-100.000 axial scans per second3-5μm axial resolution

Swept Source/Fourier OCT-swept laser200.000+axial scans per second5-7μm axial resolution at 1050nm wavelengths

In time-domain OCT, output of a low-coherence source is split between two arms, one of which scans the sample, while the other provides an adjustable time delay. The two arms are phase-matched so the returned light inerferes constructively only for light backscattered from a particular depth.Spectral-domain OCT splits light from a broadband source between the sample and the reference arms, then recombines the beams through a spectrometer onto a detector array

Swept-spectrum OCT splits light from a high speed wavelength-swept laser source between the sample and reference arms, then recombines the light a a detector array

• OCT performs “optical biopsy” imaging tissue pathology in situ and in real time

• Retinal pathology can be examined at the level of indivudual retinal layers

• 3D OCT provides comprehensive information about structure

• Reproducible registration, longitudinal follow up, quantitative assessment

Derived form a latin word “vitrum” which means glass.The vitreous is the trasparent, colourless, gelatinosous mass that fills the space between the lens and the retina. It comprises about 80% of the total volume of the globe (~4ml).

98-99% waterCollagen fibers with glycosaminoglycan hyaluronic acidVery few cells (phagocytes, hyalocytes of Balazs)NO BLOOD VESSELSRefractive index 1,336 The collagen fibers of the vitreous are held apart by electrical charges. In children, the vitreous has a consistency similar to an egg white. With age it gradually thins and becomes more liquid because of the reductions of these charges

Vitreous baseOptic discPerifoveal/macular regionVesselsPosterior lens - Weigert’s ligament

Uchino et al, ARVO 2000, Arch Ophthalmol 2001PVD begins around the maculabefore 50 y , 60 % of normal eyes have some degree of partial PVD

Mark W Johnson , Arch Ophth Feb 2001 Ultrasonography

Caused by partial posterior vitreous detachment: the posterior hyaloid is incompletely detached from the posterior pole and remains attached to the optic disc and the foveal center exerting traction on the foveal tissue.Traction on macular tissue produces gradual anatomic and functional deterioration in proportion to traction forces (anterior-posterior or tangenzial) and their duration of action.

Macular hole formation Macular pucker formation Macular detachment Cystic changes

ETIOLOGY Idiopatic disease Diabetic retinopathy Myopia Inflammation of the eye

Asymptomatic: normal or near-normal vision (initial stages).

Most commonMetamorphopsia e central scotomaBlurred visionLess commonMonocular diplopia: caused by foveal ectopia if occurs. Central photopsiaMacropsia

FUNDUS EXAMFUNDUS EXAM

FAGFAG

OCTOCT

GASS (1988, 1995)

Stage 1 : Impending MH A : foveal yellow spot B : foveal yellow ring (occult hole) Stage 2 : Full thickness early MH Stage 3 : Full thickness MH with

foveal vitreomacular separation Stage 4 : Full thickness MH with

complete PVD

The cysts develop in the inner part of the foveal center due to vitreofoveal traction. Often some degree of changes at the level of photoreceptors.

Expanding of the cyst in the outer retina

Posterior hyaloid is still attached to the edge of the hole via the operculumØ < 400μm

Stage 3 Thickened and elevated edge No PVD Operculum in front of the hole A non contractile ERM may be present around the hole White spots may be present in the center of the hole The diameter is variable

Stage 4 same characteristics, but complete PVD

If the vitreo-foveal separation have already occurred No risk for MH

If there is no vitreo-foveal separation at all, or an incomplete vitreo-foveal separation

50% risk of MH

If presence of an ERM little risk of MH

If Lamellar hole little risk of evolution to FTMH

SURGICAL TREATMENT (25GPPV)Release any vitreomacular tractionRemove the vitreous cortex (kenalog assisted)Remove as much vitreous gel as possiblePeel off any ERMILM peelingGas tampponade and face down positioning

MEDICAL TREATMENTMicroplasmin: phase IIIMicroplasmin: phase III

The use of intravitreal vital dyes has facilitated the peeling of the ILM.Several drugs may be used:ICGTrypan blueBrilliant blueTriamcinolone

The first popular dye in retinal surgery: ICG staining of ILM started in 1998 Tornanbee. Vitreous Society 1999 Kadodonoso. Arch Ophthalmol 2000 Is the use of ICG safe ? ICG is potentially toxic for RPE cells Engelbrecht et al, Am J Ophthalmol Jan 2002 Specific affinity of ICG for RPE cells RPE atrophy after prolonged contact depends on its concentration and the duration of contact ICG stains the ganglion cell axons (toxicity unknown) central microscotomas have been attributed to the use of ICG several studies show that final VA is worse when ICG have been used than without ICG.

Staining of ILM with Trypan blue has started in 2001 Feron, 2002 Arch Ophthalmol : PVR dissection Li, 2003 Br J Ophthalmol : ILM peeling for MH TB 0.15% CE mark , FDA approval, for VR surgery, TB can be diluted in 10% glucose 50/50%, for better contact with retina 2 min contact Exposure of cultured RPE cells to TB shows evidence for cytotoxicity specially in the presence of light and with concentration > 2 mg/ml Cox CA, ARVO 2003; Veckeneer M, Gaefe’s 2001 ICG is taken up by RPE at concentrations < clinically used, and TB is not. Hirasawa H, Retina 2007 Substantial retinal damage with Subretinal 0.05% ICG > 0.15% trypan blue Penha FM, Ophthalmology 2007

Clinical comparison with ICG Author Year Nb eyes Dye MH Closure VA Gain Beutel 2000 20 ICG 90% 59% ≥ 2l

99 TB 87% 71% ≥ 2l Lee 2005 19 ICG 98.5% 1.79 l

19 TB 97% 2.94 l

Unlike ICG, BBG does not cause apoptosis of retinal glial cells: safer adjuvant during VR surgery Kawahara S, IOVS 2007 With BBG, No significant reduction in RGC numbers or morphological alterations in rat eyes, AND No toxic effects attributable to the dye in patients Remy M, BJO 2008

Triamcinolone for ILM peeling: “to free from the possible toxicity of dyes”Frazer , 2005 Retina Shah , 2003 Retina Triamcinolone does not stain the ILM , but its deposit on the macular surface Cheapest…4 mg IVTA complications are known: Glaucoma, cataract … and possible retinal toxicity Preservatives Adverse effect suspicions: Toxicity for bared retina and RPE Reduces success rate of MH surgery

The gas bubble helps to the healing processInsulate the macula from the liquid of the vitreous cavity which results in dehydration of the hole edge flattening of the cystic cavities reattachement of the hole edge to the RPE narrowing of the hole aperture

Decreased visual acuity and metamorphopsia VISUAL ACUITYRE 2/10LE 10/10

Decreased visual acuity in the LE 5/10

25PPV after 5 days VISUAL ACUITYRE 4/10LE 10/10

Vitreomacular traction sydromes often can be bilateralSometimes should be treated as an emergency!!!Our clinical experience shows that the sooner we operate the better is going to be the visual outcome.

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