oct-dec 2005 teinsight - national healthcare group oct-dec05.pdf · 8 quiz poster visual...

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I n 2004, about 9,000 patients in Singapore were admitted for strokes and stroke-related diseases. Up to 20% of strokes involve the central visual pathway, giving rise to field defects and other visual disabilities, thus resulting in limitations to daily activities and rehabilitation. The generally accepted view that nothing can be done leaves little hope for such patients. In recent years, however, a paradigm shift has taken place. Via high- resolution perimetry, areas of residual vision can now be identified where targeted training can help to restore function, at least partially. The evidence to support this observed improvement in visual field defects includes reports of spontaneous recovery and training-induced expansion of visual fields, and strongly suggests that the visual system is not as “hard-wired” as previously assumed. In fact, there is a considerable overlap of receptive fields in the visual system and an astonishing degree of “neuroplasticity” is maintained in life. Following injury, receptive fields may change their location and size. Through the process of perceptual learning, both the uninjured and the injured brain tissue can improve visual performance, which in some TEInsight MITA (P) 107/02/2005 DELIVERING THE FINEST QUALITY EYECARE Transient Visual Blurring 3 6 How Not to Miss Glaucoma Chamber of Secrets No More? 7 4 Are You at Risk of Glaucoma? 7 Optometrists’ Column 8 Quiz POSTER Visual Restoration Therapy New Hope for Stroke Patients OCT-DEC 2005 A publication of IN THE SPOTLIGHT Glaucoma and Neuro-Opthalmology INSIDE Hi-resolution perimetry plots of a 52 year old patient with a right homonymous hemianopia secondary to a cerebral haemorrhage, before and after VRT, which was initiated 9 months after the stroke. Source: NovaVision™ Continued next page TEInsight is sponsored by

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Page 1: OCT-DEC 2005 TEInsight - National Healthcare Group Oct-Dec05.pdf · 8 Quiz POSTER Visual Restoration ... OCT-DEC 2005 A publication of INSIDE IN THE SPOTLIGHT Glaucoma and Neuro-Opthalmology

In 2004, about 9,000 patients in Singapore were admitted for strokesand stroke-related diseases. Up to 20% of strokes involve the centralvisual pathway, giving rise to field defects and other visual disabilities,

thus resulting in limitations to daily activities and rehabilitation. Thegenerally accepted view that nothing can be done leaves little hope forsuch patients.

In recent years, however, a paradigm shift has taken place. Via high-resolution perimetry, areas of residual vision can now be identified wheretargeted training can help to restore function, at least partially.

The evidence to support this observed improvement in visual fielddefects includes reports of spontaneous recovery and training-inducedexpansion of visual fields, and strongly suggests that the visual system isnot as “hard-wired” as previously assumed.

In fact, there is a considerable overlap of receptive fields in the visualsystem and an astonishing degree of “neuroplasticity” is maintained inlife. Following injury, receptive fields may change their location and size.Through the process of perceptual learning, both the uninjured and theinjured brain tissue can improve visual performance, which in some

TEInsightMITA (P) 107/02/2005D E L I V E R I N G T H E F I N E S T Q U A L I T Y E Y E C A R E

Transient Visual Blurring

3 6How Not to MissGlaucoma

Chamber of Secrets No More?

7 4 Are You at Riskof Glaucoma?

7 Optometrists’ Column8 Quiz

P O S T E R

Visual Restoration Therapy New Hope for Stroke Patients

O C T - D E C 2 0 0 5

A publication of

IN THE SPOTLIGHT Glaucoma and Neuro-Opthalmology

INS

IDE

Hi-resolution perimetry plots of a 52 year old patient with a right homonymous hemianopia secondary to a cerebral haemorrhage, before and after VRT, whichwas initiated 9 months after the stroke.Source: NovaVision™

Continued next page

TEInsight is sponsored by

Page 2: OCT-DEC 2005 TEInsight - National Healthcare Group Oct-Dec05.pdf · 8 Quiz POSTER Visual Restoration ... OCT-DEC 2005 A publication of INSIDE IN THE SPOTLIGHT Glaucoma and Neuro-Opthalmology

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Welcome to the second issue ofTEInsight. We have been very encouragedby the positive feedback we have receivedfrom you and hope that this sophomoreedition lives up to our initial promise.

The subspecialty spotlight is now turnedonto glaucoma and neuro-ophthalmology,two groups of diseases which commonlyrear their heads in family physician andoptometry clinics. Neuropathy is the obviouspathological link, but both groups also shareanother troubling trait: they can be difficultto diagnose in the primary health caresetting and, if missed, may lead toirreversible blindness — insidiously in chronicglaucoma, and rapidly in many neuro-ophthalmic lesions.

With that in mind, we haveconsciously increased the quotient ofarticles focusing on hard-core diagnosticapproaches, while still keeping youupdated on revolutionary technologicaland research advancements in each field.This new balance will be sustained for allsubsequent installments of TEInsight.

To help us fine-tune our content evenfurther, we have invited A/Prof Goh LeeGan, Vice-President of the College of FamilyPhysicians, to come on board as our Advisor.

I am also particularly proud toannounce the debut of a column written byand for optometrists in this issue. The EyeInstitute is blessed with a very committedand active team of 'optoms', who are anindispensable component in ophthalmiccare. Through their articles, they hope toshare with their peers what they have learntin their day-to-day practice within TEI.

We hope you find TEInsight #2 a goodread. Do keep those comments coming in.

Dr Wong Hon Tym

TEInsight Editorial TeamDr Wong Hon Tym (Chief Editor)

Mr Christopher Koh (Secretariat)

Dr Gangadhara Sundar

Dr Christopher Khng

Dr Ronald Chung

A/Prof Goh Lee Gan (Advisor)

Editor’sMessage

instances manifests as improved visual fields. The observed field expansion isusually observed at transition zones between damaged and undamaged visualfield, thus it has been proposed that partially surviving neurons and their axonsresiding at the borders of these zones are responsible for this plasticity. Massivecompensatory structural and functional changes have been noted in these cells.

By repetitive visual stimulation ofthese surviving neurons, these cellsmay become more efficient byreducing their threshold of firing, thusincreasing their functionality.

This revolutionary visualrehabilitation therapy (VRT)programme is now available inSingapore to treat patients with visualfield defects from post-chiasmal braindisorders such as strokes, braintumours and post-surgicalneurosurgical patients. It is acollaborative effort between The EyeInstitute @ Tan Tock Seng Hospitaland NovaVision, a US-based company.This therapy was approved by theUSA Food & Drug Administration in2003 and is available in major eyeinstitutes and rehabilitation centres inthe USA.

VRT provides binocular visualstimulation on a monitor, targetedprimarily at the transition zonesbetween intact visual field andabsolute field defects. Its aim is to

expand this transition zone into a visually usable area for the patient. Treatmentinvolves twice-a-day sessions of 30 minutes each with a home device, wherebythe patient fixes his/her gaze on a spot in the centre of the screen and clicks tosignal when he/she becomes aware of a stimulus in the periphery. This iscustomised and modified according to the patient’s monthly progress. Reviews aremade regularly to adjust the test strategy. The treatment programme lasts sixmonths.

Over 800 patientsin USA and Europehave now receivedVRT. Early publishedclinical trials havedemonstratedobjective visual fieldimprovement ratesreported from 60 toeven 95% ofpatients, dependingon the study group.Expansions of thevisual field sizeamounting to 29.4%from baseline havealso been reported.

VRT has not been associated with any serious adverse effects on the patient.The major exclusion criteria include:

• Known seizures or photosensitive epilepsy• Total blindness or central scotoma• Unstable fixation or nystagmus• Intellectual deficits (IQ below 85)• Neglect • Dementia• Serious handicaps such as deficits of motor functions, concentration ability

or memory. By Dr Goh Kong Yong

Continued from page 1 Visual Restoration Therapy

The NovaVision VRT device.

This revolutionary visual

rehabilitation therapy

(VRT) programme is now

available in Singapore

to treat patients with

visual field defects from

post-chiasmal brain

disorders such as

strokes, brain tumours

and post-surgical

neurosurgical patients.

In our quest to constantly improve ourselves, we wouldappreciate your frank feedback on any part of thisnewsletter, be it on the format or content. Please emailyour comments to [email protected] or mail to Ms IzyaniAyik, The Eye Institute, National Healthcare Group, 6Commonwealth Lane, Level 6, GMTI Building, Singapore149547. Please indicate if you would grant us thepermission to publish your letter. If you would like toreceive our upcoming quarterly e-newsletter, pleasesend an e-mail with your name to [email protected] with thesubject heading ‘TEInsight Subscribe’.

Page 3: OCT-DEC 2005 TEInsight - National Healthcare Group Oct-Dec05.pdf · 8 Quiz POSTER Visual Restoration ... OCT-DEC 2005 A publication of INSIDE IN THE SPOTLIGHT Glaucoma and Neuro-Opthalmology

• Transient visual lossmay also resultfrom suggestfluctuating bloodsugar levels, such asin diabetes orcorticosteroid use.

Optic Nerve CausesThe transient loss ofvision due to optic nervedisease is usuallydescribed as a loss ofvision (visual field defect)as opposed to blurring(out of focus). Thefollowing causes areall serious and requireurgent referral.

• Patients with opticneuritis maycomplain of loss ofvision associatedwith a rise in bodytemperature(Uhthoffphenomenon).RAPD is usuallypresent, and colourvision is reduced.

• Visual loss on eyemovements (gaze-evoked amaurosis)should alert theclinician to opticnerve compression and prompt appropriate imaging studies.The optic disc may be swollen, and RAPD may be present.

• Patients with giant cell arteritis sometimes report darkeningof their vision prior to the event of optic nerve head infarction(anterior ischemic optic neuropathy). They are usually elderlyand may also have a history of jaw claudication, scalptenderness, headache or malaise.

CNS Causes• Raised intracranial pressure often presents with transient

visual obscurations (grey, black or white vision) related tochanges in posture, coughing or sneezing. Headache, whileoften present, may not be related temporally to the visual loss.Papilledema is seen on fundoscopy.

• Cortical TIAs involving the visual pathway can cause transienthomonymous scotomata. These may be accompanied byhemiparesis and dysphasia, and should last no more that 24hours. Both amaurosis fugax and cortical TIAs are symptomsof carotid occlusive disease and may herald future strokes.

• Migraine The visual loss in migraine is usually preceded byvisual phenomena such as fortification spectra, bright flashinglights or distorted vision. Headache in classic migraine usuallyfollows within 30 minutes. By Dr Clement Tan

For more approaches to different types of visual loss, please referto The Eye Institute’s flipchart “Practical Approaches to CommonProblems in Ophthalmology”.

Transient Visual Blurring

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N E U R O - O P T H A L M O L O G Y

SPOTLIGHT ON

TEI’s Neuro-Ophthalmology Team

Transient visual loss can be caused by common and innocuousconditions such as dry eyes or presbyopia. However,raised intracranial pressure, transient ischemic attacks

and tumours affecting the optic nerve (among others) mayalso present this way. A systematic history and clinical examinationgoes a long way in elucidating the cause.

The onset, character and duration of each attack must beelicited. A useful approach is to review the causes, beginning atthe ocular surface and ending at the brain.

Ocular Causes• In dry eyes, symptoms usually occur later in the day,

exacerbated by dry or windy conditions, and are associatedwith prolonged visual tasks (protracted sessions at thecomputer, reading). The “mistiness” resolves with blinking.Treatment with lubricants usually brings resolution.

• Transient blurring with headaches and seeing halos aroundlamps may be due to intermittent angle closureglaucoma. The anterior chamber is shallow (see also “HowNot To Miss Glaucoma” in this issue), and there may alreadybe optic disc cupping. Elderly Chinese females are at muchhigher risk.

• Amaurosis fugax, a transient ischemic attack of the eye ismonocular, abrupt, painless and typically described asdarkening (not blurring), like a curtain falling over the eye. Itlasts only a few minutes and resolves spontaneously. Suchpatients frequently have ischemic risk factors and one shouldexclude carotid bruits, heart murmurs and arrhythmias.

• As presbyopia sets in (usually around the age of 40), patientsdescribe difficulty focusing after reading for short periods, andthe ‘strain’ or fatigue is relieved by rest. These patients wouldfind a pair of reading glasses helpful.

Dr Goh Kong Yong Senior ConsultantHead of Neuro-Ophthalmology Service

Dr Goh completed his neuro-ophthalmology fellowship atthe prestigious BascomPalmer Eye Institute, USAunder the preceptorship ofDrs Joel Glaser and NormanSchatz. He has beenextensively involved inteaching and trainingyounger doctors in thischallenging sub-specialty. Asa founding member of theAsian Neuro-OphthalmologySociety, he has alsomentored fellow neuro-ophthalmologists in theregion. Recently, he wasinstrumental in launchingvision restoration therapy inAsia for stroke and braintrauma patients.

Dr. Lim Su Ann Consultant

Dr Lim was trained in adultand paediatric neuro-ophthalmology andstrabismus at the Dean AMcGee Eye Institute inOklahoma City, under thesupervision of Dr. R.Michael Siatkowski and Dr.Bradley Farris. She has aspecial interest in paralyticstrabismus and motilityproblems of neurologicorigin. She is also interestedin the epidemiology ofneuro-ophthalmic diseasesand is the principleinvestigator of the firstSingapore-wide neuro-ophthalmic database,supported by a grant fromthe National HealthcareGroup.

Dr Clement Tan Associate Consultant

Dr Tan has recently returnedto Singapore, following hisfellowship at King’s CollegeHospital and the NationalHospital for Neurology andNeurosurgery in London,UK. He has a specialinterest is in disorders ofocular motility and the pupil.He is also significantlyinvolved in undergraduateand postgraduateOphthalmology training inSingapore and the region.

Visiting ConsultantProfessor James F. CullenTEI @ TTSH

Differentiating the benign from the blinding

SOME CAUSESAND THEIR SYMPTOMS

Dry EyesMisty and gritty

IntermittentAngleClosureGlaucomaHalos

AmaurosisFugaxDark curtain

Raised ICPTransientdarkness

MigraineShimmering lights

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Glaucoma is a leading cause of blindness in SingaporeGlaucoma is an eye disease in which the internal eyeball pressure in one or both eyes builds up to an inappropriatelyhigh level. Permanent damage occurs to a delicate but vital eye structure called the optic nerve, and this canlead to blindness if left untreated.

This is because glaucoma is usually painless and the visual loss slowly affects one eye more than the other. Thehealthier eye is thus still able to compensate for the weaker eye until the advanced stage, or when both eyesbecome significantly affected.

Public Education Material with compliments ofTEInsightO C T - D E C 2 0 0 5

All clinical material and photographs are the property of TEI @ NUH

Glaucoma may steal your vision without you noticing...

Eye pressure is a balanceof inflow and outflowIn glaucoma, outflow is obstructedand permanent damage occurs.

Eyedrops Laser Surgery

What can be done?Your family doctor can look forevidence of optic nerve damage, giveadvice and refer you to an eyespecialist if required. Eye screening isalso available at most hospitals. Fromthe ages of 40 to 60, you should havean eye examination every 2 to 4 years.After the age of 60, you shouldincrease your visits to once every 1 to2 years. Ask your family doctor foradvice, particularly if you have a familyhistory of glaucoma. If detected early,effective treatments are available toprevent further optic nerve damageand preserve your vision.

...until it’s too late

Treatment Options to Control Glaucoma

• The elderly (over 60 years)

• Those with a family memberwho suffers from glaucoma

• Diabetics

• Those who have had previousinjury to the eyes

• Those taking long-term steroidtablets or eye drops.

If you have any of the above, youshould go for an eye screening

RISK?WHO IS AT

Are you at risk?GLAUCOMA

P UL L O

UT F

OR Y

OU

R

C L I NI C

NO

T I CE B

OA

R D

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Alerts in the HistoryMost glaucoma is chronic and asymptomatic. Butimportant clues in the history can be found, soask for these specifically:

• Epidemiological Clues (Risk Factors)- Family history of glaucoma- History of severe ocular trauma or surgery

(secondary glaucoma)- Use of steroid eye drops - Severe myopia (OAG) or severe

hyperopia (ACG)- Elderly + Oriental + Female (Acute ACG)

• Clues from Symptoms - Seeing halos around lamps - Decreased vision (only in very advanced

disease)- Transient blurring, with headache

(Intermittent ACG)- Severe one-sided headache with vomiting,

visual loss and eye pain and redness (AcuteACG)

Alerts in the Physical ExaminationAny of the symptoms above should prompt youto exclude the following:

• Shallow anterior chamber The eclipsesign is usually positive in ACG (whetheracute or chronic). Patients who have shallowanterior chambers should not be dilated foroptic disc examination. (Figure 1)

• Evidence of optic nerve damage- RAPD. Glaucoma is frequently bilateral but

asymmetrical, thus a Marcus-Gunn pupilmay be present.

- Optic Disc Signs: The hallmark ofglaucomatous disc damage is diffuse orfocal thinning of the rim of the opticdisc. (Figure 2)

• Classic Signs of Acute Angle Closure(Figure 3)- Unilateral red, painful eye - Mid-dilated, fixed pupil- Positive eclipse sign- Hazy cornea - Patient is usually an elderly Chinese female- A hard eyeball (gently ‘ballot’ both eyeballs

through closed eyelids, using the tips ofboth your index fingers - the attack eye isusually palpably harder than the fellow eye)

- In the very elderly or frail, watch out forsevere dehydration from vomiting

By Dr Wong Hon Tym

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G L A U C O M A

How Not To Miss GlaucomaSignposts in your patient’s history and examination that should set off alarm bells.

A/Prof Paul Chew Senior ConsultantHead,TEI Glaucoma Service

A/Prof Chew continuesto be mentor andinspiration to all buddingglaucomatologists inSingapore. Trained atMoorfields Eye Hospitaland AddenbrookesHospital in UK, A/ProfChew is also the Head ofTEI@NUH. Early in hiscareer, he recognized theimpact of angle-closureglaucoma in this regionand is regarded as apioneer in the researchof the disease. He is afounding member of theSouth East AsianGlaucoma InterestGroup, and his close andextensive ties withoverseas centres havemade him a key mover incollaborative glaucomaresearch worldwide.

Dr Lim Boon AngConsultant

Dr Lim received herglaucoma training at theSydney Eye Hospital/SaveSight Institute where shedid research on objectivevisual field assessmentusing visual evokedpotentials (VEP). She isalso a champion forbetter patient andoptometrist education,and has beeninstrumental in the set-up of glaucoma patientsupport groups inSingapore.

Dr Lennard TheanConsultant

Dr Thean is the team’slink to the subspecialityof uveitis. Havingreceived fellowshiptraining in bothglaucoma and uveitis, DrThean brings a wealth ofknowledge andexperience to both theseareas. Acknowledging hisexpertise in the area ofuveitic glaucoma, DrThean has been invitedto give numerous talkson this topic both locallyand regionally.

Dr Wong Hon TymConsultant

With a fellowship atMoorfields Eye Hospital,UK, Dr Wong has aspecific area of interestin optic nerve headimaging. He returned toset up TTSH’s glaucomadiagnostic services andhas since been invitedinternationally to instructon this topic. Dr Wong isalso Deputy Head ofTEI@TTSH and is cruciallyinvolved in thedevelopment and editingof the Singapore Ministryof Health Clinical PracticeGuidelines for glaucoma,to be published this year.

Dr Vernon YongAssociate Consultant

Dr Yong is the mostrecent addition to theglaucoma team, havingjust returned from a one-year fellowship at theLions Eye Institute inPerth, Australia. Dr Yongchose to be a glaucomaspecialist as he realizedthat the population wasan ageing one and thenumbers of glaucomapatients would steadilyincrease over the nextdecade or so.Involvement inpopulation screening isDr Yong’s other area ofinterest.

TEI incorporates the largest glaucoma service on the island. Being at theforefront of angle-closure research has put the team on the internationalmap, with our involvement in numerous key multi-centred trials. Aburgeoning roster of clinical and research fellows is testimony to theservice’s reputation and quality of training.

SPOTLIGHT ON

TEI’s Glaucoma Team

Dr Winifred NolanClinical Fellow/Associate Consultant

Dr Cecilia AquinoClinical Fellow

Currently on overseas fellowship postings:

Glaucoma continues to fly beneath theradar of most primary health carephysicians (including ophthalmologists and

optometrists on occasion), because it isfrequently asymptomatic, with subtle signs. Hereis a quick “should-not-miss-these” checklist ofthe symptoms and signs of glaucoma:

(OAG = Open Angle Glaucoma; ACG = AngleClosure Glaucoma)

Dr Loon Seng CheeAssociate Consultant

Dr Jovina SeeAssociate Consultant

Dr Leonard YipAssociate Consultant

Visiting Consultants:Dr Aung TinTEI@NUH

Dr Daniel SimTEI@TTSH

Dr Geh MinTEI@NUH

Figure 1 The Eclipse Sign

Figure 2 Optic Disc Signs in Glaucoma

Shine a torchlight from the temporal aspect of the eye (arrow). If the nasal iris is notilluminated, the eclipse sign is positive, i.e. thispatient may have a shallow anterior chamber,and is at risk of (or already has) angle closure.

The classic combination of a hazy cornea, mid-dilated pupil andthe eclipse sign are all seen in this picture.

Figure 3 Acute Angle Closure Glaucoma

a. Healthy Optic Disc A healthy neuro-retinal rim is seen all around. Cup/Discratio is 0.4.

b. Diffuse Rim Thinning A C/D ratio of0.7 is generally considered very

suspicious. C/D asymmetry of more than 0.2 between left & right discs is alsosignificant. Here, the rim is uniformly thinned, giving a C/D of 0.8.

c. Focal Rim Thinning Here, the inferior rim is particularly thinned out. A blood vessel isexiting at the very edge of the disc, as there is no rim for it to ‘climb over’

a b c

Some of the material in this article will also befeatured in the upcoming MOH Clinical PracticeGuidelines for Glaucoma

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G L A U C O M A

Chamber of SecretsNo More?

A new imaging toolthat is being test-runat TEI@NUH promisesto reveal vitalinformation aboutanterior chamberangle structure andbehaviour in AngleClosure Glaucoma

Accurate assessmentof the structures andspaces within the

anterior segment of the eye(the cornea, anteriorchamber, angle and lens) iscrucial in many clinicalcontexts, such as angleclosure glaucoma and forpatients undergoingspecialized surgery. Current methods (such asgonioscopy, ultrasoundbiomicroscopy andpachymetry) tend to besubjective, unwieldy orsimply too crude to providethe information that we need.

Anterior SegmentOptical CoherenceTomography (AS-OCT) is anew diagnostic imagingtechnique that will allowmore precise, objectiveassessment of anteriorsegment elements, includingthose previously hiddenfrom clinical observation.The new device is called“Visante” (from the words‘vision’ and ‘anterior’), anduses a 1310 nm light source

for illumination and high-speed imaging. (Figure 1)The entire anterior segmentis captured in a non-contactmethod at an imageresolution of 10µm. Besidesenhanced patient comfortand safety, anterior chamberdistortion is avoided (amajor bugbear ofantecedent techniques) and

minimal training is needed.Video capture is possibletoo, facilitating dynamicevaluation of anteriorsegment configuration.

This novel modality fromCarl Zeiss Meditec isproducing excellent results inour clinical studies. Pilottrials conducted at TEI @NUH have produced striking

images of unprecedentedclarity, objectively visualizingmost structures within the anterior chamber, andtheir spatial inter-relationships. The only major drawbackcurrently is that ciliary bodydelineation remains poor,due to inadequatepenetration of the lightsource.

The AS-OCT shouldeasily straddle the fields ofrefractive surgery andglaucoma. There is alsogreat potential for the AS-OCT to emerge as ascreening tool for the lattercondition. Other importantapplications include imagingthrough opaque corneas,imaging corneal and irispathology, scanningimmediately after surgery(with minimum risk ofinfection due to its non-contact nature) andquantitative measurementsof corneal thickness andanterior chamber depth.(Figure 2). By Dr Cecilia Aquino

AS-OCT scan,showing the

entire anteriorsegment ofthe eye in a

single image.

Figure 2: AS-OCT images of (from left) open angles with deep anterior chamber; closed angleswith shallow anterior chamber; detailed angle analysis. All images of property of TEI@NUH.

Figure 1: The Visante AS-OCT

INAPPROPRIATELY high intraocular pressure(IOP) is still the main risk factor forglaucomatous optic nerve damage. An IOP ofover 21mmHg, however, is no longer a goldenbenchmark in the diagnosis of the disease. Withmore optometric practices acquiring and usingnon-contact tonometers, here are someimportant facts, caveats and tips we must keepin mind whenever an IOP measurement is being taken.

• IOP, taken in isolation, can lead toboth over- and under-diagnosis ofglaucoma. Up to 50% of patients withglaucoma have a baseline IOP of less than21mmHg (Normotensive Glaucoma), and lessthan 10% of patients with “high” IOP havevisual field loss from glaucoma (OcularHypertension).

• Thicker corneas give higher-than-actualIOP readings and thinner corneas register alower-than-actual IOP. So we may be under-estimating IOPs in patients with thincorneas, in whom the Ocular HypertensiveStudy has shown higher risk of conversion toglaucoma.

• For patients who have undergonerefractive surgery, IOP measurement ischallenging. Studies have shown thattonometers are underestimating the IOP inthese thin corneas. Many studies have come upwith corrective formulae, but there is noconsensus as yet. A rough rule of thumb: forevery dioptre of myopic correction, add 0.5mmHg to the measured IOP.

• It is equally important to maintaincentration when measurements are taken. IOPmeasurements taken from the peripheral corneaare highly unreliable.

• Explain to patients what is being done toavoid eye squeezing during the test, whichcan lead to falsely high readings.

• Although the non-contact tonometer isfairly accurate within the normal IOP range,measurements still show some variability. It isadvisable to take an average of 3 ormore consistent readings.

• Finally, a note on the Tonopen, whichalso gives accurate IOP readings in the normalrange, but may overestimate IOP in low rangesand underestimate IOP in high ranges.

Non-contact tonometers are easy to use,and the risk of infection and allergic reactions totopical anaesthetic drugs are eliminated.However Goldmann Applanation Tonometryremains the gold standard of IOP measurement.By Ms Olivia Chng

TONOMETRYTo Believe or Not to Believe?

OOPTOM’S CORNERF O R O P T O M E T R I S T S

B Y O P T O M E T R I S T S

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AAODr Shawn Goh, TEI Resident,presenting his paper onPrognostic factors ofResponse to IntravitrealTriamcinolone Acetate inDiabetic Macular Edema atthe American Academy ofOphthalmology in Chicago,14-18 October.

Trip to Mae Hong Son,ThailandParticipating in ‘Unite forSight Inc.’ sponsored bySingapore OptometricAssociation, TEIOptometrist, Ms RebeccaChew, refracts a memberof the Long Neck Karentribe in Mae Hong Son,Thailand.

W H A T ’ S O N

U P C O M I N G E V E N T S

4th National Update forOptometrists andOpticians (NUOO)Singapore PolytechnicPrincipal, Mr Low WongFook, presenting TEI Headof Research, Adjunct A/ProfAu Eong Kah Guan withVisionary Award during theNUOO dinner. Dr WilfredTang in background.

TEI Research Day 2005 WinnersAbove, left: Winner of TEI-Allergan Research Prize, DrMandeep Singh, TEI Resident, presenting his paper onAnterior Segment OCT of Trabeculectomy Blebs atthe First TEI Research Day held 8 Oct ’05.

Above, right: Winner of TEI-Novartis Research Prize,Dr Ajeet Wagle, TEI Registrar (right), receiving hisaward from Director, Dr Lim Tock Han for his paper onEfficacy of a Single Drop Versus 3-drop Regime Using1% Tropicamide for Mydriasis in Patients with DarklyPigmented Irides – A Randomized Controlled Trial.

EYEQTEST YOUR

YOU MAKE THE DIAGNOSIS!

A N S W E R SA 29 year old male presentedwith a few weeks’ history ofheadaches with intermittentblurring of vision in both eyes.He had no past medical orfamily history of note.Examination revealed visualacuity of 6/6 in each eye, noRAPD, and a normal slit lamp

examination. His fundi had a similar appearance in BOTHeyes, and a photograph of the right eye is shown.

What are the classic fundus signs seen here?

What are the differential diagnoses?

What clinical tests and investigations need to be performed?

12

3

Q U I Z

Quiz master: Dr Gangadhara Sundar

1:Bilateral swelling centeredaround the optic nerve head(mild blurring of disc margins),severe arteriosclerosis (note AVcrossing changes), cottonwool spots, hard exudates

2:Papilledema from Intracranialhypertension/tumor, malignanthypertension, Bilateralinflammatory optic neuropathy(rare)

3:Blood pressure, Neuroimagingof the brain, Renal functiontests. This patient’s resultswere: BP 240/132 mm Hg; CTScan of brain: Normal; RenalParameters: Increased BUN,Creatinine, Decreased GFR,Shrunken kidneys.

Diagnosis: MalignantHypertension with Renal Failure

Date/Time Venue Fee Title Contact

For GPs 19 Nov 05 TTSH Eye Centre, Level 1 FOC Neuro-Ophthalmic Diagnosis: How Not To Miss Ms Lalitha K / Mr Kwek Joong Chuan1.30pm - 3.30pm Speakers: Dr Goh Kong Yong, Dr Lim Su Ann 6357 7648 / 7736

[email protected]

For Public27 Nov 05 TTSH Theatrette $5 Does Your Child Need Glasses? Mr Dennis Yeoh: 6357 82661.30pm - 3.00pm

3 Dec 05 Auditorium, FOC Cataract - What you should know Ms Alice How: 6379 3741, 6379 3540 (fax)11.00am - 3.30pm Alexandra Hospital Mandarin (11am), Hindi (1.30pm), English (12.30 & 2.30pm) [email protected]

3 Dec 05 AH, NUH, TTSH FOC National Eye Care Day Eye Screening & Pre-register for eye screening at selected Community Centres.9.00am - 5.00pm Art Exhibition by Visually Handicapped Artists at TTSH More information will be published in the media on 23 Nov.

17 Dec 05 Auditorium, Public Forum in English: Healthy Vision Ms Alice How: 6379 3741, 6379 3540 (fax)10.00am - 12.00nn Alexandra Hospital [email protected]

For Ophthalmologists & Trainees 10 & 11 Mar 06 STAR Lab, NUH Upon First Human Cadaver Dissection Course on Ms Valerie Ng: 6772 53189.00am - 5.30pm enquiry Orbital Anatomy & Oculoplastic Surgery [email protected]

Guest Speaker: Dr Santosh Honavar

TEI Doctors in the Research Publications1. Yip CC, Gonzalez-Candial M, Jain A, Goldberg RA, McCann JD.Lagophthalmos in enophthalmic eyes. British Journal ofOphthalmology. 2005 Jun;89(6):676-8.

2. Khng C, Snyder ME.Ophtec iris reconstruction lens. Ophthalmology. 2005 Jun;112(6):1172; author reply 1172-3.

3. Aung T, Yong VH, Chew PT, Seah SK, Gazzard G, Foster PJ, Vithana EN.Molecular analysis of the myocilin gene in Chinese subjects withchronic primary-angle closure glaucoma. Investigative ofOphthalmology and Visual Sciences. 2005 Apr;46(4):1303-6.

4. Aung T, Nolan WP, Machin D, Seah SK, Baasanhu J, Khaw PT,Johnson GJ, Foster PJ.Anterior chamber depth and the risk of primary angle closure in 2 East Asian populations. Archives of Ophthalmology. 2005 Apr;123(4):527-32.

5. Loon SC, Chew PT, Oen FTs, Chan YH, Wong HT, Seah SK, Aung T.Iris ischaemic changes and visual outcome after acute primary angleclosure.Clin Experiment Ophthalmol. 2005 Oct;33(5):473-7.

6. JC Wang, A Tan, Ray Manatosh, P Chew. Experience with Arraymultifocal Lens in Singapore. Singapore Medical Journal 2005;46(11):1

National University Hospital - Eye ClinicGP Hotline: 6772 2000Clinic Line: 6772 5408Clinic Fax: 6772 5508

Tan Tock Seng Hospital - Eye CentreGP Hotline: 6357 8383Centre Line: 6357 8000Centre Fax: 6357 8675

Alexandra Hospital - Ophthalmology and Visual SciencesGP Hotline: 9369 3912OVS Line: 6379 3500OVS Fax: 6379 6292

General Enquiries by E-mail: [email protected]