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Corneal collagen cross-linking for treating keratoconus: a cochrane interventional review
Presenter: Dr.Arushi Goyal
Moderator: Dr. R.R.Sudhir
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Cochrane review
Cochrane Reviews aresyste&atic reviews o$ /rimary research in human heath care an" heath
/oicy, an" are internationay reco0nise" as the hi0hest stan"ar" in evi"ence-#ase" heath care+ 1hey investi0ate th
e e2ects o$ interventions $or /revention, treatment an" reha#iitation+
A systematic review is a type ofliterature review that collectsand critically analyzes multiple
research studies or papers
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'ackground
• (eratoconus : 'ilateral nonin)a&&atory
corneal ectasia• *ncidence : $ in !### eole
• Collagen cross-linking +C,:
/reat&ent to slow or halt rogression of
keratoconus
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Signi0cance
• C, :only treat&ent to halt rogression ofkeratoconus
• Ro1ust evidence on long ter& results ofe2cacy and safety of this rocedure lacking
• Standardised criteria for selection of idealatient lacking
• Review is evidence 1ased reference oint for
eole with keratoconus for validated infor&ation regarding the e2ciency of this treat&ent.
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3'45C/*65
/o assess whether there is evidence that C,is an e7ective and safe treat&ent for halting the rogression of keratoconus co&ared to n
o treat&ent+
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M5/83DS A9D R5S/S*9CS*39 A9D 5,CS*39 CR*/5R*A
• /ye of studies:
Ran"omise" controe" trias 3RC1s4 where /atients are"ia0nose" with keratoconus+
•
/ye of articiants:*ncluded A a0e /artici/ants
5;cluded with history o$ some other treatment+
• /ye of intervention:
Stu"ies that com/are" C56 with the e/itheium o2 techni7ueto no treatment
5;clusion: Stu"ies com/arin0 "i2erent ways o$ "oin0 C56
Stu"ies with no contro 0rou/
8se o$ C56 $or ectasias other that keratoconus
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M5/83DS and R5S/S+cont.
Search ðods for identi0cation of studies:
Eectronic searches A eectronic "ata#ases ti%9th au0ust %&':
% review authors ES an" RK reviewe" a stu"ies
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M5/83DS and R5S/S+cont.
*ncluded studies:
< RC/S!$= eyes > $$= cases and $## controls
Australia +?ittig-Silva !##"@ the nited(ingdo& +3'rart !#$$@ and the nited State
s +8ersh !#$$.
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M5/83DS and R5S/S+cont.
/ye of intervention +C, with eitheliu& o7techniBue
Epithelium removed undertopical anaesthesia
Isotonic ribofavin solution o0.1% applied
Cornea treated with UVradiation !"#0 nm at "
m$cm&' or "0 minutes.
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M5/83DS and R5S/S+cont.
• Assess&ent of risk of 1ias in includedstudies
8sin0 cochranes too $or assessin0 risk o$ #ias 3as a/ercenta0e4 havin0 the $oowin0 criterias
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BIAS
ttrition refers to thereduction of
experimental participants leaving an experiment or
study for reasons,
Selective reporting
Concealed allocation isa procedure implementedin a randomized control
trial where the individualsscreening and separatingthe candidates into two
(or more) arms of a studyare linded!
(andomisation is the estmethod
removingselection iasetween two
groups ofpatients
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M5/83DS and R5S/S+cont.
3utco&e &easures:
Pri&ary outco&e: Disease rogression at $!&onths after treat&ent
• *ncrease (&a; $. D
• ?orsening in uncorrected 6A #.! logMAR
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M5/83DS and R5S/S+cont.
Secondary Measures+$! &onths aftertreat&ent:
• Mean average corneal ower
• Mean corneal achy&eter at thinnest artof cornea
• Mean sherical eBuivalent
•
Contact lens intolerance• Adverse e7ects of C, included in these
studies
• Euality of life outco&es
•
5cono&ic data
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M5/83DS andR5S/S+cont.
Measure of treat&ent e7ect
Pri&ary outco&es +dichoto&ous data : risk
ratio+RRSecondary outco&es +continuous data :Mean di7erence)ichotomous variabl
es are nominalvariables which haveonly two cate+ories
or levels. ,ore-ample i we wereloo/in+ at +ender
we would mostprobably cate+oriesomebody as eithermale or emale.
2he ris/ ratio !orrelative ris/' is
the ratio othe ris/ o an event
in the two +roups avalue o 1 indicatesthat the estimated
e3ects are the sameor both
interventions.
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M5/83DS and R5S/S+cont.
4ro+ression at 1& months o 5ma-
6tudy C78 Control
+roup
(is/
ratio
Con9denc
e interval"#Brart$%&&
%'$$ '$$ %!& %!%&,$!*&
+ittig Silva$%%
%'- '&% %!&$ %!%&,$!%%
4ro+ression at ": months o 5ma-
+ittig Silva$%%
%'* &-' %!% %!%%,%!
;o study too/ the other primary outcome i.e
UCV as their outcome
4rimary outcome analysis
M5/83DS d
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M5/83DS andR5S/S+cont.
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M5/83DS andR5S/S+cont.
dverse outcomes
6tudy participants
dverse event
+itting Silva$%% ( *months)
&! 1orneal edema withparacentral in2ltrate$! 3eripheral cornealvascularisation, ! Suepithelial in2ltrates withacIn4ammation
"#Brart $%&&(&$ months)
1orneal edema, acin4ammation, recurrent cornealerosion
5uality of life
6ersh $%&& 7eported it for treated eye ut
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M5/83DS and R5S/S+cont.
;vera 7uaity o$ evi"ence usin0 ery ow 3 ?e are uncertain o$ the
estimate4
• 1he main reasons $or "own0ra"in0 the evi"ence
incu"e" risk o$ #ias in the incu"e"
stu"ies, im/recision, in"irectness an" /u#ication #ias+
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Su&&ary of &ain results
• 3nly < RC/s@ out of which $ +8ersh !#$$ had very littleusa1le data.
• 9ot ossi1le to ool data due to di7erences in &easuringand reorting outco&es
• 8igh overall risk of 1ias
• "#-=#F reduction in relative risk for rogression ofkeratoconus 1ut this result is very uncertain
• Adverse e7ects not unco&&on
• S&all sa&le sie
• Risk of visual acuity loss@ Buality of life outco&es andecono&ic data not reorted
• 3nly $ study followed u for &ore than $ year
• Children not included in any of the studies
• Euality of evidence low@ the &ain reasons 1eing risk of 1ias @i&recision@ indirectness and u1lication 1ias.
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•/his syste&atic review is not a &etaanlysis:
as few studies
Studies did not reort reBuired outco&es in correct
for&at to ena1le data to 1e ooled 1here$ore it is a 7uaitative anaysis not7uantitative3metaanaysis4
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D)SC8SS);N
;ther systematic reviews6tudy> ;ICE &01" > C78 is e3ective inhaltin+ pro+ression
;law
Increase in nown
A study y
6enri?uez $%&&
7andom allocation of
treatment not done
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A / 8 3 R S C 3 9 C S * 3 9 S
Desite the nu&erous rosective and retrosective studies
availa1le in the literature and the fact that C, see&s to 1e
acceted worldwide as a 1reakthrough treat&ent in the &anage
&ent of keratoconus@ evidence is li&ited due to the lack of roe
rly conducted RC/s. *f strict criteria are used and only data fro&
RC/s acceted@ then there is a lack of evidence that C, is indeed
an e7ective treat&ent in halting the rogression of keratoconus+
8igher-Buality studies are needed 1efore an aroriate
&etaanalysis can 1e conducted to con0r& the i&ortance of this
treat&ent
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?hy is stu"y si0ni=cant
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Ma@or /ositives an"ne0atives
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examined! Lhe mainoutcome measures wererefractive error, visual
acuity, cornealtopographic>eratometry, ultrasonicpachymetry, andtopography.derivedcorneal wavefront!(E6U826>
At 0 years compared topreoperative values,mean sphericale?uivalent refractive
error (S85) increased
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;uture
research
Jap in literature
8xisting
Eiterature
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