1. Othertypesof glaucoma
If there is inflammationinthe eye (anterioruveitis),adhesionsmaydevelopbetweenthe lensandiris
(posteriorsynechiae).These adhesionswill blockthe flowof aqueousbetweenthe posteriorand
anteriorchambersandresultinforwardballooningof the irisanda rise inthe IOP.Adhesionsmayalso
developbetweenthe irisandcornea(peripheral anteriorsynechiae),coveringupthe trabecular
drainage meshwork.Inflammatorycellsmayalsoblockthe meshwork.Topical steroidsmaycause a
gradual asymptomaticrise inIOPthat can leadto blindness.(Patientstakingtopical steroidsoveralong
periodshouldalwaysbe underophthalmological supervision.) The growthof new vesselsonthe iris
(rubeosis) occursbothindiabeticpatientsandafterocclusionof the central retinal veinresultingfrom
retinal ischaemia.Thesevesselsalsoblockthe trabecularmeshworkcausingrubeoticglaucoma,whichis
extremelydifficulttotreat.The trabecularmeshworkitself mayhave developedabnormally(congenital
glaucoma) or beendamagedbytraumato the eye.Patientswhohave hadeye injurieshave ahigher
chance than normal of developingglaucomalaterinlife.If there isableedinthe eye aftertrauma,the
redcellsmayalso blockthe trabecularmeshwork.
Medical treatment
The main aimof therapyinglaucomamanagementisreductionof IOP.There isnow goodevidence from
multiple large randomisedtrialsthatreducingIOPiseffectiveinpreventingdiseaseprogressioninocular
hypertension,primaryopenangleglaucoma,andeveninso-callednormal tensionglaucoma.Target
pressuresinthe lowteensare associatedwiththe lowestprogressionrates.
blockers(forexample,timolol,levobunolol,carteolol,betaxolol,andmetipranolol) Thesereduce the
secretionof aqueousandare still the mostcommonlyprescribedtopical treatment.Contraindicationsto
theiruse include ahistoryof lungor heartdisease,asthe dropsmay cause systemic blockade.Itis
importantto be aware that topical blockerscanunmasklatentand previouslyundiagnosedchronic
obstructive airwaydiseaseinelderlypeople.Systemiceffectsfromeye dropscanbe reducedby
occlusionof the punctum(fingerpressedonthe caruncle,whichcanbe feltas a lumpat the inner
canthusof the eye) orshuttingthe eyesforseveral minutesafterputtinginthe drops.Thisreducesthe
lacrimal pumpingmechanismandstopsthe eyedrops runningdownthe lacrimal passagesandbeing
absorbedsystemicallyviathe nasal mucosaorby inhalationdirectlyintothe lungs.Thismayalso
enhance ocularabsorptionof the drugs.These dropsare usuallygiventwice a
ABC of Eyes
56
Effectsof topical steroids●Topical steroidsmaycause a change in the drainage meshwork,resultingin
a slowrise inintraocularpressure ●Patientsmaynotcomplainof visual symptomsuntil severe damage
has occurred
Newvesselsonthe iriscausingrubeoticglaucoma
2. It isimportantto rememberthatdropsusedtotreat glaucomacontainpowerful drugsthatcan have
markedsystemicside effects,despite the low topical dosesused
Eye closure to reduce systemicside effectsafterinstillingdrops
Keraticprecipitates
ABCE_final_cha09.qxd 2/3/04 9:30 AM Page 56
day,but longacting formsnowavailable canbe givenonce aday, eitheralone orincombinationwith
otherdrops.
Prostaglandinanalogues(forexample,latanoprost,travoprost,andbimatoprost) Thesereduce the IOP
by increasingaqueousoutflowfromthe eye viaanalternative drainageroute calledthe uveoscleral
pathway.Itis possible togetreductionsinIOPof upto 30–35% withthese drugs.Thisabilitytoachieve
largerreductionsinIOPwithimprovedsystemicsafetyprofileshasbeenamajortherapeuticadvance in
glaucoma.Systemicside effectsare minimalbutanunusual side effectinafew patientswithlightirides
isa gradual,permanentdarkeningof the iris.Patientsoftennotice thattheireyelashesincrease in
lengthanddarken.Foroptimumeffect,these dropsare usedonce daily(atnight).
SympathomimeticagentsTopical adrenaline,once commonlyprescribed,isnow rarelyusedbecause of
lack of efficacycomparedwith blockersandadverse effectsonthe conjunctiva.A newergenerationof
agentsthat stimulate the receptorsof the sympatheticsystemisnow used—forexample,brimonidine
(usedtwice aday) or apraclonidine.Contraindicationsinclude cardiovasculardisease,because of the
potential systemicsympathomimeticeffects.
Parasympathomimeticagents(forexample,pilocarpine) These constrictthe pupil and“pull”onthe
trabecularmeshwork,increasingthe flow of the aqueousoutof the eye.The small pupil may,however,
cause visual problemsif central lensopacitiesare present.Constrictionof the ciliarybodycauses
accommodationandblurredvisioninyoungpatients.Pilocarpine shouldnotbe usedif there is
inflammationinthe eye,asthe pupil maystickto the lensclose tothe visual axis(posteriorsynechiae)
and affectvision.Pilocarpine isusuallyadministeredfourtimesadaybut can be usedtwice dailyina
combinedformwitha blocker,oronce at nightin a gel preparation,whichreducessideeffects.When
patientsfirstinstill pilocarpine theyoftenexperienceamarkedbrow ache,whichtendsto reduce with
longertermuse of the drug.Pilocarpine therapycanincrease the riskof retinal detachment.
Carbonicanhydrase inhibitorsThese are available astopical (forexample,dorzolamide, brinzolamide) or
oral (forexample,acetazolamide) agents.Theyreduce the secretionof aqueous,andthe systemicform,
administeredorally,isthe mostpowerful agentforreducingIOP,althoughunfortunatelyitmayhave
side effects,includingnausea,lassitude,paraesthesiae,electrolytedisturbances,andrenal stones.The
topical formhas minimal systemicside effects.Carbonicanhydrase inhibitorsshouldnotbe usedin
patientswithsulphonamide allergy.
Neuroprotective agentsExperimental evidence existsthatsome neuroprotective agentsmayreduce
intraocularpressure inducedglaucomatousdamage.However,atpresentthere isnoconclusive
3. evidence thatthese agentsare helpful inglaucoma,butlarge scale clinical trialsare currentlybeing
carriedout inthisarea.
AllergytoglaucomadropsThe mainsymptomsof drop allergyare intense itchingandirritationof the
eyesandeyelids,whichare exacerbatedbyinstillationof the drops.The characteristicsignsof drop
hypersensitivityincluderedinjectedeyes,redswolleneyelids,andezcemalike excoriationof the eyelids
and periocularskin.
