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R E F R A C T I VEEY E C A R E O
A P R I L2 O O 7
PushingtheFrontiersof CornealDiagnosis
with theConfocalMicroscope
Chrktophe Baudouin, MD, PhD
Micron-level Resolution
TheRostockCornealModule, develEquippingthe HRT3with an
opedat RostockUniversityin Germany,
optional cornealmodulelets
convertsthe basicHRT3 into a confocal scanninglasermicroscope.In this
cliniciansgarnerhintsfrom
mode, the HRT3 can show the clinithe eye'smicrostructureto
solvetheir mostdifficult cases cianlayer-by-layerviewsofthe corneal
microstructure, from the epithelium
of ocularsurfacedisease.
to the endothelium (Figure 1). It has
a resolution of I micron and covers a
n 1991. the first version of the field 400 microns square.
My clinical researchgroup began
Heidelberg Retinal Tomograph
(HeidelbergEngineering,Heidelberg, working with a Rostock-equipped
Germany) gave ophthalmologists a HRT when the corneal add-on was
clinical tool that used cellular auto- at the prototype stage.During three
fluorescenceto diagnoseand monitor yearsof helping Heidelbergrefine the
glaucomatousdamage to the optic module, we have found the confocal
nerve.HRT2, the secondgeneration microscope to be an excellent,nonofthis confocal scanninglaseroph- invasive tool for addressingthe difthalmoscope(SLO),was releasedin ficult diagnosticand treatmentchal1999and expanded the technique's lengesofthe corneaand ocular suruses to the retina and, later, the face(Figures2A,28 and 3).
The HRT3 is portable, a feature
cornea.
that should make it more convenient
to share among multiple users in
group practicesor different locations.
Also, unlike earlierdesigns,the confocal microscopecan be usedacross
the entireanteriorocular surfaceand
not just in the optical center.
Help with Diagnosis
The confocal microscope producesin vivo, cellularlevel views of
the cornea,conjunctiva,and sclera,
FIGURE
1 The corneamodule allowsvisualiza- which can give the physician crucial
tion of multiple layersofthe cornea.Shownfrom information about an array of clinileft to right are:the surfaceepithelium,cellsfrom
cal problems,including:
the middleof theepithelial layer;cornealnerves
. Delayed healing or poor vision
in Bowmanslayer; and keratocyteswithin the
epithelialstroma.
after LASIK or PRK
. Diffuse lamellar keratitis and
other problems with the LASIK
Today, the latest generation, the
flap interface
I Pachymetry of the cornea before
HRT3, also has an improved corneal
module, which makes it possible to
and after LASIK and of the flap
quickly diagnoseand treat cornealpaafter surgery
o Recurrent corneal ulcers. Ifthe
thologiesby looking at their structural
effectswithin the ocular surface.
cause is basement membrane
POTENTIAL
CLINICAL
USESOF
THEHRT3 CORNEAT
MODUTE
l1
Haze,ingrowth,and similarproblems
post-refractivesurgery
ff
Diffut" lamellarkeratitisand other
interfaceproblems
d
corneal pachymetry
t'
flap thicknessmeasurementafter LASIK
t'
R"aurr"nt cornealerosions/
anteriorbasementmembrane
dystrophy diagnosis
tr
tr
tr
r
o
0
o
Evaluatingand differentiating
cornealdystrophies
Blebexaminationand evaluation
lmmediatediagnosisand
characterizationof infection
dystrophy, this would not be visible at the slit lamp
Evaluating and differentiating
cornealdystrophies
Knowingwhether a filtering bleb
is functioning (aqueoushumor
can be seen in the subconjunctival space),has flattenedor has
become fibrotic
Monitoring long-term contact
lenswear
Determining whether a patient
has bacterial,viral, amoebic,or
fungal keratitis, an urgent situation becauseofthe vision-threatening implications of delayed
treatment
Diagnosis in Infection
With the confocalmicroscope,differentpathogenshaveunique features
that make diagnosisvirtually immediate, compared to the days or even
weeksthat may be requiredfor culture
results.The importance ofthis potential role for confocal microscopywas
highlighted last year during the intercontinental outbreak of Fusarium
O 2007EthisCommunications,
Inc. Reprintedfrom Refroctive
Eyecare" www.ref
ractiveeyeca
re.com
'1ffi.if$Sil",ffi'ffiffi:,
keratitis associated with a contact
lens care solution. An investigation
led by the US Centers for Disease
Control & Preventionfound 164cases.l
lessandresembles
takingintraocular
pressurewith an applanationtonometer.The objectivehasa disposable
coverfor sterility.
amongthe membersof a grouppracticecouldalsoprovecosteffective.For
the subspecialist,
especially
onewith
an interestin cornealresearch,the
HRT3with a corneamodule
couldbe
a very usefuland cost-effectivetool.
While the slit lamp remainsthe
unit ofchoicefor routinecornealexfor thosecases
aminations,
thatarent
routine, cornealsubspecialists
and
generalophthalmologistscanbenefit,
today,from examiningthesepatients
with anHRT3equippedwith thelatest
RostockCornealModule.
THEBOTTOMLINE
FIGURE
2A Squamousmetaplasiain superficlalpunctat€ keratitisprior to treatment with topical cyclosporlne.
FIGURE
2B Normalepithellumfollowing
cyclosporinetherapy.
A third ofthem weresevereenoughto
warrant a cornealtransplant,which
might havebeenavoidedwith earlier diagnosisandtreatment.Alfonso
et al showedthat antifungaltherapy
worked fasterwhen Fusarium infections wererecognizedearly.2
Fromthepatient'sperspective,
the
corneamodulefor the HRT3hasone
drawbackthe objectivetouchesthe
eye.However,the procedureis pain-
FIGURE3 Epithelialbasementmembrane
dystrophy. This patlent is a poor candidate for LASIKbut could be consldered
for PRK.
Thelatestmodel of the Heidelberg
Retinal Tomograph,called HRT3,
has an optional RostockCorneal
Modulethat canhelpophthalmologistssolveclinicalpuzzlesofthe ocular surface.Added onto the newly
portableHRT3,themoduleconverts
theconfocalscanninglaser
ophthalmoscope
into aconfocalmicroscope.
HRT3 wasredesignedto makethe
entire deviceportable; also for the
first time, the microscopecan be
usedto visualizenot only the central corneabut alsothe coniunctiva
and sclera.
A Complementto the Slit Lamp
Pastpredictionsthat the confocal
microscope
mightonedayreplace
the
slitlamphave,to date,provedwrong.
Indeed,theconfocalmicroscope
cannot and should not replacethe slit
lamp.In part this is because
the slit
lamp givesthe ophthalmologistan
essential,wide view of intraocular
structuresat the tissuelevel,while
the confocalmicroscopeshowsonly Christophe Baudouin, MD, PhD, is a professor
a 400-by-400micronsectionat the of ophthalmology at Quinze-Vingts National
cellularlevel-a viewthatis unneces- Ophthalmology Hospital in Paris. He claims
sarily detailedfor routine casesand no financial interest in the products discussed.
patientswithout cornealdisease.
Dr. Baudouin received assistance with this
In addition,unlikethe slit lamp,a article from medical writer Linda Roach.
high-resolution
devicelike theHRT3
with a cornealmoduleprobablystill References
coststoomuchandislikelytobeused 1. Alfonso EC, Cantu-Dibildox L MunirWM,
et al. Insurgence of Fusarium keratitis
toolittletojustifyitspresence
in every
associatedwith contact lenswear.Arch Ophophthalmologist's
office.However,if a
thalmol 2OO6:124;9
4l-9 47.
practicealreadyhas
anHRT3forpos- 2. Chang DC, Grant GB, O'Donnell K, et al, for
the Fusarium Keratitis Investigation Team.
terior segmentwork,thecorneamodMultistate outbreak of Fusarium keratitis
ule may be a cost-effective
decision. associatedwith use of a contact lens soluFurther,a singleconfocalunit shared
tion. JAMA. 2006;296:953-9 63.
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