Glaucoma and Eye Pressure: How High is Too High?

When people hear the word “glaucoma,” many of them connect the eye disease with elevated eye pressures ( also known as intraocular pressure ... Skiptomaincontent BacktoExpertAdvice GlaucomaandEyePressure YvonneOu,MD UniversityofCalifornia,SanFrancisco,UCSFMedicalCenter ExpertAdvice Publishedon: July4,2021 Share Facebook Twitter Pinterest LinkedIn Print Email ReadthisarticleinSpanish Whenpeopleheartheword“glaucoma,”manyofthemconnecttheeyediseasewithelevatedeyepressures(alsoknownasintraocularpressureorIOP).However,therelationshipbetweenglaucomaandeyepressureiscomplicatedandhaschangedovertime. Historically,glaucomawasidentifiedasadiseaseinwhichtheeyewasfirmorhardduetohigheyepressure.However,doctorsgraduallycametounderstandthatglaucomacanoccurevenwheneyepressureisnormal,whichsometimesmakesithardertodiagnose.Today,eyepressureisconsideredamajorriskfactorforglaucomabutisnotincludedinthedefinitionofthiseyedisease.Eyepressurecontrolalsoplaysamajorroleinthetreatmentofglaucoma.Loweringeyepressureistheonlytreatmentwecurrentlyhave,whetherthrough medications,laser,orsurgery. WhatisConsideredHighEyePressure? Inmanyformsofglaucoma,theeyepressureishigh.Whatisconsidered“toohigh”?Patientsaskmethisallthetime,andItellthemitdepends. First,weknowthatstatisticallyspeaking,havingeyepressuresover21mmHg(millimetersofmercury)isnotverycommoninagenerallyhealthypopulation.Wealsoknowthateyepressuretendstoincreaseaswegetoldersincethedrainagesystemdoesnotfunctionaswell. Second,weknowthatanopticnervethatishealthycanwithstandahighereyepressurethananopticnervethatisunhealthy.Forexample,patientswhohaveopticnerveswithsignsofmoreadvanceddiseaselikelyneedlowereyepressurestopreventworseningofglaucoma. Third,theeyepressurethatis“toohigh”foryouropticnerveissometimesdeterminedovertime.Let’ssayyoubegintreatmentwithaneyedroptolowereyepressure,anditissuccessfulinloweringyoureyepressureby20percent.However,yourglaucomacontinuestoprogressslowly.Inthatcase,despitetheinitialeyepressurelowering,yourophthalmologistmaydeterminethatthisnewlowereyepressureisstill“toohigh”andyoureyesneedtohaveevenlowereyepressures. Finally,itisimportanttorealizethatmostpatientswiththemostcommonformofglaucoma, primaryopen-angleglaucoma,haveelevatedeyepressuresbutdonotfeelpain.Glaucomaisoftencalledthe“silentthiefofsight”becausepatientsdonothavesymptomsuntillateinthediseasewhentheynoticecentralvisionloss. Glaucomawith“Normal”EyePressure Anotherformofglaucomaiscalled normal-tensionglaucoma. Ifsomeonehasnormal-tensionornormal-pressureglaucoma,theireyepressurehasneverbeenrecordedabove21mmHg,yettheystillhaveopticnervedamage.Doesthismeanthattheireyepressurehas never beengreaterthan21mmHg?Thatisdifficulttosaysinceasingleeyepressuremeasurementatanygiventimeonanygivendayintheophthalmologist’sofficeisatiny“snapshot”ofwhattheeyepressuretrulyis. Patientswhohavenormal-tensionglaucomaarethoughttohavemoresusceptibleopticnerves,suchthatevenatnormaleyepressurestheopticnerveslowlydegenerates.Moreover,eventhoughtheeyepressureis“normal,”thetreatmentisthesame:loweringtheeyepressurethroughmedications,laser,orsurgery.Loweringeyepressureinnormaltensionglaucomapatientswasfoundtoslowglaucomaprogressioninwell-designedrandomizedclinicaltrialsincludingtheCollaborativeNormalTensionGlaucomaStudy(CNTGS).TheCNTGSwasthefirststudyofitskindtoshowthata30percentdecreaseineyepressurereduceddiseaseprogressioninpatientswithnormal-tensionglaucoma. AimingfortheTarget Onetermyoumayhearyourophthalmologistdiscussisyour“targeteyepressure.”Thisreferstoagoaleyepressureyourophthalmologistbelieveswillstopyourglaucomafromworsening.Thereisnomagicformulabutitisbasedonthestatusofyouropticnerve,theresultsofyourvisualfieldtests,andyourophthalmologist’sclinicaljudgment,amongotherfactors.Itisagoodgoaltohave,butitisnottheonlyfactortoconsider.And,eventhoughyoumayhaveatargeteyepressure,itisimportanttorecognizethatasingleeyepressuremeasurementintheofficeisnottrulyreflectiveofwhatyoureyepressureisonaverage,daytoday,weektoweek,ormonthtomonth. Finally,yourtargeteyepressuremaychangeovertimedependingonhowstableyourglaucomais.Forexample,ifyouhavebeenstableforalongtime,yourophthalmologistmaynotbeasconcernedbyaneyepressuremeasurementthatisslightlyabovegoal.Indeed,eyepressurecanvarydependingonthetimeofday,whenyouinstilledyourlastdoseofeyedrops(ifyouareonmedication),yourstresslevel,andotherfactors.Ontheotherhand,ifyoucontinuetodemonstrateworseningglaucomadespitebeingatyourtargeteyepressure,yourophthalmologistmaydecidetorevisethetargetpressuretoanevenlowergoal. Resources GlaucomaToolkit (InformationtoHelpYouUnderstandandManageGlaucoma) ExpertInformationonGlaucoma (Articles) NationalGlaucomaResearchReport (Newsletters) WhatisNormalEyePressure? (Q&A) PrimaryOpen-AngleGlaucoma (Article) HowisEyePressureMeasured? (Article) TheEyeExamforGlaucoma (Article) Normal-TensionGlaucoma (Article) OcularHypertensionandGlaucoma (Article) GlaucomaandtheImportanceoftheEye’sDrainageSystem (Article) WhatisaGlaucoma"Suspect"? (Article) PrimaryOpen-AngleGlaucoma (Article) Abouttheauthor YvonneOu,MD UniversityofCalifornia,SanFrancisco,UCSFMedicalCenter YvonneOu,MD,isaboardcertifiedophthalmologistwhospecializesinglaucoma,includingmedical,laserandsurgicaltherapies;cataractevaluationandtreatmentincludingcombinedcataractandglaucomasurgery;glaucomafilteringandimplantsurgery;andnewerprocedures. Fullbio Helpfindacure Donatetohelpend GlaucomaDisease Iwouldliketodonate $25 $50 $100 $250 $1000 Other DonateNow Stayintouch ReceiveGlaucomaresearchupdatesandinspiringstories