Volumetric Assessment of Space Betw ILM via OCT
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Volumetric assessment of the space between the posterior hyaloid and internal limiting membrane using SD-OCT Romualdo Malagola, 1 Nicola Iozzo, 2 Pierluigi Grenga 3 1 U.O.S. Vitreo-retinal Service, U.O.C. B. of Ophthalmology, Sapienza University, Umberto I Hospital, Rome, Italy 2 Retinitis Pigmentosa Service, U.O.C. B. of Ophthalmology, Sapienza University, Umberto I Hospital, Rome, Italy 3 Department of Opthalmology, A.S.L. Latina, Sapienza University, Rome, Italy Correspondence to Profess or Nicola Iozzo, Retinitis Pigmentos a Service, U.O.C. B. of Ophthalmology, Sapienza Universi ty, Umberto I Hospital, 155 Viale del Policli nico, Rome 00161, Italy; [email protected] Received 22 April 2012 Revised 2 October 2013 Accepted 10 October 2013 Published Online First 29 October 2013 To cite: Malagola R, Iozzo N, Grenga P. Br J Ophthalmol 2014;98: 16–18. ABSTRACT The purpose of this study was to measure, for clinical and surgical utility, the distance between the post erior hyaloid and the internal limiting membrane using a spectral domain optical-coherence tomography (SD-OCT) device. Eight eyes of eight patients with subclinical partial posterior vitreous detachment (PPVD) with vitreomacular traction syndrome were examined with SD-OCT. To quantify the vitreoretinal distance, the basic applications of SD-OCT (Spectralis HRA+OCT Heidelberg Engineering) were modied. We conducted a topographic study of the entire posterior pole by de ning new maps, each generated from 19 raster scans. We obtained maps that represent the space between the residual vitreous and retina, expressed numerically and on a colour spectrum, and overlapped them on a posterior pole photograph. We also created a single map of the entire posterior pole. The mean PPVD volume in the eight eyes was 104.87±5.25 mm 3 . This study produced detailed maps of the vitreoretinal distan ce, which may facilitate the study of the clinical progr ession of PPVD. In case of surgery the maps may help to accurately determine where surgical manipulation is needed safely apart from the retina. These maps could also assist in the assessment of pharmacological vitreolysis ef cacy. INTRODUCTION Pa rtia l post erior vitr eous deta chment (PPVD) is consi der ed the rs t st age of pos ter ior vitreous det ac hme nt (PVD). PVD is a chr oni c ev ent tha t begins in the macular periphery and then extends to wa rds the ce nt re of the fo vea unti l just the fove ola is at ta che d. 1 Po ssibl e comp lica tions of PPVD are vitr eoma cula r traction syn dro me and macular pucker . T o measure the distance between the posterior hyaloid and retinal surface in a topo- gr aph ic fas hio n to st udy the pr ogr ess ion of the early stages of PVD, we modi ed the basic applica- tions of spectral domain optical-coherence tomog- raphy (SD-OCT; Spectralis HRA+OCT, Heidelberg Engi neer ing) and gene rated nume rica l and colour maps that may facilitate clinical studies of the early stages of PVD to achieve be tt er planni ng of surgery. 2 3 In the early stage PVD is usually partial (PPVD) and in many cases asymptomatic. This diagnosis is ach iev ed by the use of OCT, an ima ging method devised in 1991 and commercialised in 1996. 4 5 In re la tio n to re sid ual vitreous-reti nal adh erenc e, PPVD can beco me symptoma tic. A possi ble earl y complication of PPVD is acute vitreomacular trac- tion syndrome, in which the vitreous is incompletely separated from the retina at the pos- terior pole and remains attached in a focal, multi- focal or ext ende d reg ion comp risi ng the mac ula (macular oedema, macular hole) or more rarely the opt ica l ner ve (op tic oe dema). Ano the r pos sib le later complication of PPVD is epiretinal membrane pro life ra tion , with the dev elop ment of mac ular pucker. 6–8 The use of OCT in the evaluation of vitreoretinal pathology in relation to PPVD has been the subject of many studies. 9–12 For some years, a new form of OCT has been introduced, SD-OCT, which gives a higher signal-to-noise ratio than time domain OCT and, in turn, greater de niti on. W e do not kno w any study in whic h SD-OCT ha s been us ed to meas ure the dis tance betwee n the internal reti nal surface and cortical vitreous (posterior hyaloid) at each single point of the posterior pole in eyes with PPVD and to create a corresponding topographic map. Through this study detailed maps of the vitreor- etina l dist ance , whic h may facili tate the stud y of the clinical progression of PPVD, can be obtained. In case of surgery, such as for macular traction or epiretinal membrane, it may be possible to deter- min e pr eci sel y whe re sur gic al ma nip ula tio n is need ed saf ely apart from the ret ina. These maps could also assist in the assessment of pharmacologic vitreoly sis ef cacy. 13–18 METHODS W e exami ned SD-OCT images of eig ht ey es of eigh t pati ents with subclini cal PPVD with fov eal attachment. T o quant ify the vitreoretina l dist ance , the basi c applicati ons of SD-OCT wer e modi ed. Usually SD-OCT software traces, for every scan, two reference lines (markers) corresponding to the areas of maxi mum re ectivity . These are internal limiting membrane (ILM) and the retinal pigment epith eliu m (RPE) –chor ioca pill aris comp lex . The distance bet we en these lines was calcul at ed for every scan and a retinal thickness map was created. Conve rsely , by using an operating parameter in the sof tware, tha t is, the re tin al thickness , and manually modifying the position of the two lines, we shif te d the two li nes so that the inner one, whi ch denes ILM, coinc ided with the pos teri or hy alo id, whi le the out er one, whi ch denes the RPE–chor ioca pill aris comp lex , coin cide d with the ILM for each scan of every map ( gure 1A,B). We conducted a topographic study of the entire pos ter ior pol e by denin g ne w gr id map s, ea ch generated from 19 raster scans. 16 Malagola R, et al . Br J Ophthalmol 2014;98:16–18. doi:10.1136/bjophthalmol-2013-303590 Innovations group.bmj.com on August 4, 2014 - Published by bjo.bmj.com Downloaded from
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Volumetric assessment of the space between theposterior hyaloid and internal limiting membraneusing SD-OCTRomualdo Malagola,1 Nicola Iozzo,2 Pierluigi Grenga3
1U.O.S. Vitreo-retinal Service,U.O.C. B. of Ophthalmology,Sapienza University, Umberto IHospital, Rome, Italy2Retinitis Pigmentosa Service,U.O.C. B. of Ophthalmology,Sapienza University, Umberto IHospital, Rome, Italy3Department of Opthalmology,A.S.L. Latina, SapienzaUniversity, Rome, Italy
Correspondence toProfessor Nicola Iozzo, RetinitisPigmentosa Service, U.O.C. B. ofOphthalmology, SapienzaUniversity, Umberto I Hospital,155 Viale del Policlinico, Rome00161, Italy; [email protected]
Received 22 April 2012Revised 2 October 2013Accepted 10 October 2013Published Online First29 October 2013
To cite: Malagola R,Iozzo N, Grenga P. Br JOphthalmol 2014;98:1618.
ABSTRACTThe purpose of this study was to measure, for clinicaland surgical utility, the distance between the posteriorhyaloid and the internal limiting membrane using aspectral domain optical-coherence tomography (SD-OCT)device. Eight eyes of eight patients with subclinicalpartial posterior vitreous detachment (PPVD) withvitreomacular traction syndrome were examined withSD-OCT. To quantify the vitreoretinal distance, the basicapplications of SD-OCT (Spectralis HRA+OCT HeidelbergEngineering) were modied. We conducted atopographic study of the entire posterior pole by deningnew maps, each generated from 19 raster scans. Weobtained maps that represent the space between theresidual vitreous and retina, expressed numerically andon a colour spectrum, and overlapped them on aposterior pole photograph. We also created a single mapof the entire posterior pole. The mean PPVD volume inthe eight eyes was 104.875.25 mm3. This studyproduced detailed maps of the vitreoretinal distance,which may facilitate the study of the clinical progressionof PPVD. In case of surgery the maps may help toaccurately determine where surgical manipulation isneeded safely apart from the retina. These maps couldalso assist in the assessment of pharmacologicalvitreolysis efcacy.
INTRODUCTIONPartial posterior vitreous detachment (PPVD) isconsidered the rst stage of posterior vitreousdetachment (PVD). PVD is a chronic event thatbegins in the macular periphery and then extendstowards the centre of the fovea until just thefoveola is attached.1 Possible complications ofPPVD are vitreomacular traction syndrome andmacular pucker. To measure the distance betweenthe posterior hyaloid and retinal surface in a topo-graphic fashion to study the progression of theearly stages of PVD, we modied the basic applica-tions of spectral domain optical-coherence tomog-raphy (SD-OCT; Spectralis HRA+OCT, HeidelbergEngineering) and generated numerical and colourmaps that may facilitate clinical studies of the earlystages of PVD to achieve better planning ofsurgery.2 3
In the early stage PVD is usually partial (PPVD)and in many cases asymptomatic. This diagnosis isachieved by the use of OCT, an imaging methoddevised in 1991 and commercialised in 1996.4 5 Inrelation to residual vitreous-retinal adherence,PPVD can become symptomatic. A possible earlycomplication of PPVD is acute vitreomacular trac-tion syndrome, in which the vitreous is
incompletely separated from the retina at the pos-terior pole and remains attached in a focal, multi-focal or extended region comprising the macula(macular oedema, macular hole) or more rarely theoptical nerve (optic oedema). Another possiblelater complication of PPVD is epiretinal membraneproliferation, with the development of macularpucker.68
The use of OCT in the evaluation of vitreoretinalpathology in relation to PPVD has been the subjectof many studies.912 For some years, a new form ofOCT has been introduced, SD-OCT, which gives ahigher signal-to-noise ratio than time domain OCTand, in turn, greater denition. We do not knowany study in which SD-OCT has been used tomeasure the distance between the internal retinalsurface and cortical vitreous (posterior hyaloid) ateach single point of the posterior pole in eyes withPPVD and to create a corresponding topographicmap.Through this study detailed maps of the vitreor-
etinal distance, which may facilitate the study ofthe clinical progression of PPVD, can be obtained.In case of surgery, such as for macular traction orepiretinal membrane, it may be possible to deter-mine precisely where surgical manipulation isneeded safely apart from the retina. These mapscould also assist in the assessment of pharmacologicvitreolysis efcacy.1318
METHODSWe examined SD-OCT images of eight eyes ofeight patients with subclinical PPVD with fovealattachment.To quantify the vitreoretinal distance, the basic
applications of SD-OCTwere modied.Usually SD-OCT software traces, for every scan,
two reference lines (markers) corresponding to theareas of maximum reectivity. These are internallimiting membrane (ILM) and the retinal pigmentepithelium (RPE)choriocapillaris complex. Thedistance between these lines was calculated forevery scan and a retinal thickness map was created.Conversely, by using an operating parameter in
the software, that is, the retinal thickness, andmanually modifying the position of the two lines,we shifted the two lines so that the inner one,which denes ILM, coincided with the posteriorhyaloid, while the outer one, which denes theRPEchoriocapillaris complex, coincided with theILM for each scan of every map (gure 1A,B).We conducted a topographic study of the entire
posterior pole by dening new grid maps, eachgenerated from 19 raster scans.
16 Malagola R, et al. Br J Ophthalmol 2014;98:1618. doi:10.1136/bjophthalmol-2013-303590
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RESULTSMaps of retinal thickness and volume were automatically trans-formed into maps that represent the space between the posteriorhyaloid surface and the retinal surface, expressed numerically andon a colour spectrum. Both maps overlapped on a posterior polephotograph (gure 2).Ultimately, we created individual maps of the different
regions of the posterior pole to obtain a single map of the entire
posterior pole (gures 3 and 4). Overlapping the map with aphotograph enables the surgeon to identify various landmarks(eg, retinal vessels) that will facilitate surgery involving areaswith increased vitreoretinal distance.The mean volume of PPVD in the eight eyes examined was
104.875.25 mm3. The mean volume of PPVD was higher overthe macular area (48.012.4 mm3) than below the macular area(33.682.04 mm3).
Figure 2 Transformation of a map of retinal volume and thickness into one showing volume of partial posterior vitreous detachment.
Figure 1 (A) Incomplete posteriorvitreous detachment (PVD) with fovealattachment. The red lines, whichcorrespond to the internal limitingmembrane and retinal pigmentepithelium (RPE)choriocapillaris, havebeen shifted manually so that theycoincide with the detached hyaloid andinternal limiting membrane,respectively. This task was performedin all 19 horizontal scans for each ofthe nine maps. (B) Incomplete PVDwith foveal attachment. The red lines,which correspond to the internallimiting membrane and RPEchoriocapillaris, have been shiftedmanually so that they coincide withthe detached hyaloid and internallimiting membrane, respectively. Thistask was performed in all 19horizontal scans for each of the ninemaps.
Malagola R, et al. Br J Ophthalmol 2014;98:1618. doi:10.1136/bjophthalmol-2013-303590 17
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DISCUSSIONNumerical or colour maps of the cavity volume of PPVD in themacular zone and in the post-equatorial region with documenta-tion of progressive peripheral vitreoretinal adhesion could be
useful in studying the clinical progression of the early stages ofPVD and assessing the efcacy of pharmacological vitreolysis.This also applies to the vitreomacular traction syndrome toevaluate the clinical progression of vitreous detachment and toidentify the focal retinal points at which the detached perifovealposterior vitreous allows safer surgical manipulation usingforceps or picks.We hope that this study will lead to the creation of a new
protocol for the use of the latest OCT devices that automaticallydetect ILM and the posterior hyaloid.
Contributors NI: substantial contributions to conception and design, acquisition ofdata, or analysis and interpretation of data; drafting the article. RM: nal approvalof the version to be published. PG: analysis and interpretation of data.
Competing interests None.
Patient consent Obtained.
Ethics approval The study was approved by the Ethics Committee of Umberto IHospital.
Provenance and peer review Not commissioned; externally peer reviewed.
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Figure 4 Numerical map of the partial posterior vitreous detachmentin the macular area.
Figure 3 The related colour map of the partial posterior vitreousdetachment in the posterior pole.
18 Malagola R, et al. Br J Ophthalmol 2014;98:1618. doi:10.1136/bjophthalmol-2013-303590
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doi: 10.1136/bjophthalmol-2013-3035902013
2014 98: 16-18 originally published online October 29,Br J Ophthalmol
Romualdo Malagola, Nicola Iozzo and Pierluigi Grenga
limiting membrane using SD-OCTbetween the posterior hyaloid and internal Volumetric assessment of the space
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