E-Poster Rio de Janeiro Corneal Tomography and Biomechanics Study Group The study of the correlations of the optic disc size with Cornal Geometry and Biomechanical

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Rio de Janeiro Rio de Janeiro Corneal Corneal

Tomography andTomography andBiomechanicsBiomechanicsStudy GroupStudy Group

The study of the correlations of the optic disc size with Cornal Geometry and Biomechanical

characteristics Fernanda B Fonyat,MD

Renata Siqueira, MD; Guilhermo C Velarde, DSc

Renato Ambrosio Jr, MD, PhDPurpose: Study the correlations between

corneal geometry (Pentacam) and biomechanical (ORA) properties with

morphology of the disc optic size (HRT)

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IntroductionCorneal properties represent independent risk factors for Glaucoma neuropathyOcular Hypertension Treatment Study (OHTS ) and European Glaucoma Prevention Study Group ( EGPS) demonstrated that low thickness of cornea is a important predictive factor for ocular hypertensive patients develop glaucoma lesion in the optic nerveA relation between geometrical and biomechanical properties of the cornea and optic nerve susceptibility may existCornea and sclera wall have same embryologic origin, thereby the cribriform lamina of the optic disc may share similarities with the cornea whose measurements may be able to anticipate higher impact of pressure on the optic nerve

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IntroductionOcular Response Analyzer (ORA, Reichert) is a non contact air pulse pressure measurement that dynamically measures corneal propertiesCorneal hysteresis, cornea resistant factor (CRF), intra-ocular pressure for Goldman (IOPg) and intra-ocular pressure compensate (IOPcc)Congdon et al identify that hysteresis reduction is a negative factor to perimetryPentacam have a specific software that analyze the paquimetry progression with is better than measure just the central thickness of the corneaLesk et al showed with Heidelberg Retina Tomography (HRT) a biggest complacence of cribriform lamina in patients with thin cornea

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Ocular Response Analyzer (ORA, Reichert) Measurement

ORA SignalORA Signal

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Corneal Tomography (CTm) (Pentacam, Oculus)

Patented 360º Scheimpflug camera that captures 25 to 50 corneal slits

Normal Values (n=200 normal corneas):

Pachy Thinnest: 541 ± 33.2 (438 to 611) Corneal volume (4mm): 11.44 ± 0.67 (9.3 to 12.9) Keratometric Astigmatism: 1.2 ± 0.97 (0 to 6.9) Pachymetric Progression (maximal): 1.1 ± 0.2 (0.6 to 1.9)

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Patients and MethodsRetrospective study in patients who did Pentacam, HRT and ORA. All patients where Caucasian and they didn’t have ocular disease or refractive surgeryThe retinography was classify as Disc Damage Likelihood Scale (DDLS)The statistic test was SPSS v 13.0. For IOP g , CRF and hysteresis were used Pearson’s test and for IOPcc Spearman’s test

THE DISC DAMAGE LIKELIHOOD SCALE

7b0 for more than 270°

0 for more than 180º

10

7a0 for more than 270°

0 for 181° to 270°0 for 91º to 180º9

60 for 181° to 270°

0 for 91° to 180°0 for 46º to 90º8

50 for 91° to 180°

0 for 46° to 90°0 for less than 45º7

40 for 46° to 90°

0 for less than 45°less than .16

30 for less than 45°less than .1.1 to .195

2less than .1.1 to .19.2 to .294

1.1 to .19.2 to .29.3 to .393

0b.2 to .29.3 to .39.4 to .492

0a.3 or more.4 or more.5 or more1

2.25 mm optic nerve

1.75 mm optic nerve

1.25 mm optic nerve

DDLS Stage

For Large Disc >2.00 mm

For Average Size Disc 1.50-

2.00 mm

For Small Disc <1.50 mm

DDLS Stage

ExamplesNarrowest width of rim (rim/disc ratio)

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Results75 patients were female and 47 were male244 eyes from 122 patients were analyzedThe mean age was 47,2 (8 to 97 years with sd 21,7)There was no statistical significant correlation between optic disc size and intra-ocular pressureThere were statistical significant correlations between optic disc size and biomechanical and geometrical characteristics of the cornea

4 6 8 10 12 14 16 18CRF.M

0.5

1.5

2.5

3.5

disc

.are

a

Optic disc size x CRFSignificant negative correlation r=-0.1337 (p=0.0263)

450 500 550 600D0.0mm.Pachy

0.5

1.5

2.5

3.5

disc

.are

a

Optic disc size x thinnest paquimetry

;

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ResultsThere was a significant negative correlation between CRF, hysteresis (CH), thinnest corneal value, Pachymetric Progression Index on the Maximal axis and corneal volume

There were a significant positive correlation between optic disc size and astigmatism and axis

Optic disc size x Corneal volume (4mm), Significant correlation

r=-1.887 (p=0.0017)

Optic disc size x greatest paquimetry progression

Optic disc size x astigmatism axisSignificant correlation r=-

0.1766(p=0.0034)

5 30 55 80 105 130 155 180Axis.K1

0.5

1.5

2.5

3.5

disc

.are

a

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Example: Thick cornea

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Example: Thin cornea

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DiscussionWe found a negative association between corneal geometric and biomechanical parameters and morphology of the optic discThis study was limited because some patients were treated with glaucoma medications and because functional tests such as perimetry were not analyzed

ConclusionThere is a negative correlation between optic disc and corneal characteristics, which can explain in part why the cornea is a important risk factor to increaseSuch data may lead to susceptibility parameters for glaucoma neuropathy development.

Documents

E-Poster Rio de Janeiro Corneal Tomography and Biomechanics Study Group The study of the correlations of the optic disc size with Cornal Geometry and Biomechanical