spatial alignment of microperimeters

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1、SpatialAlignmentofMicroperimetersRussellL.Woods,FuensantaA.Vera-Díaz,LeeLichtenstein,EliPeliTheSchepensEyeResearchInstituteAnAffiliateofHarvardMedicalSchoolAbstractPurpose:Inmicroperimetry,thelocationsofvisualstimuliarereportedonaretinalimage.Thetermmicroperimetrycametorepresentretinalperimetry

2、eventhoughperimetrywithassmallorsmallertargetscanbeperformedinstandardperimetry.Thereasonthatthisterminologywasestablishedistheassumptionthatretinalperimetryprovidesmoreaccurateplacementoftargets,inrelationtofundusfeatures.Thiswasindeedthecaseinearlyscanninglaserophthalmoscopes(SLO)wheretheimag

3、inglaserwasalsousedtocreatetheperimetricstimuliandthereforetargetpositionwasknownexactly.Mostmicroperimeterstodayusedifferentsystemsforstimuluspresentationandretinalimaging.Reportedlocationsontheretinalimagewillbeincorrectwhennotspatiallyaligned.Wereportgenericpsychophysicalmethodsforconfirming

4、spatialalignmentofmicroperimeters.Methods:Twotechniquesweredevelopedandevaluatedusingnormally-sightedobserversandNidekMP-1instruments.(1)Thephysiologicalblindspotwasidentifiedusingsmallstimuli.Thecenteroftheopticdiskidentifiedbylocatingtheapparentedgeofthediskintheretinalimagewascomparedtothece

5、nteroftheblindspot.(2)Angioscotomataofatleasttwomajorretinalvesselswithorthogonalorientationsweremapped.Thelocationsofthoseangioscotomatawerecomparedtothelocationsofthevesselsintheretinalimage.Inadditiontothesetechniques,wecomparedthelocationsofthefoveaof16normally-sightedobserverstopublishedSL

6、O-derivednormalpopulationdatabasedonopticdisklocation.Theeffectofheadtiltoncomputedfoveallocationwasexamined.Results:Repeatablespatialalignmenterrorsof0.5ºormorecouldbefoundusingbothtechniques.Measurementerrorsassociatedwithdifferentoperators,subjectsandimageswerelessthanabout0.2º.Differencesbe

7、tweenoursmallpopulationsampleandpreviousstudieswereexplainedbyspatialmisalignment.Evensmalltiltsoftheheadproducedapparentchangesinfoveallocation.Discussion:Thesetechniquesforassessmentofspatialalignmentcouldbeappliedtoanymicroperi