EVALUATION OF PACHYMETRY,PROGRESSION INDEX AND BACK DIFFERENCE ELEVATION VALUES IN

PATIENTS OF KERATOCONUS

E- POSTER 0235

Presenting and Chief author Dr. Seema Bhosale Co-author Dr. Vijay Shetty Dr. Suhas Haldipurkar Dr. Ravish Vaishnav

FINANCIAL DISCLOSURE

None of the authors have any financial interest in any products mentioned in this study

Introduction• Keratoconus(KC)is a non inflammatory ectatic corneal dystrophy

characterized by a usually progressive corneal thinning that results in corneal steepening,protrusion and irregular astigmatism1

• Elevation based Scheimpflug imaging is used for the diagnostic characterization of the front and back corneal shape, along with pachymetric mapping2

• The Enhanced Best Fit Sphere(Reference shape) utilized in the Belin/Ambrosio Enhanced Ectasia display provides the back difference elevation values extrapolated from the difference maps3

• 1 Rabinowitz YS. Keratoconus. Surv Ophthalmol. 1998;42:297–319

• 2 Ucakhan OO, Cetinkor V, Ozkan M, Kanpolat A. Evaluation of Scheimpflug imaging parameters in subclinical keratoconus, keratoconus, and normal eyes. J Cataract Refract Surg. 2011;37(6):1116–1124

3 Belin MW, Khachikian SS. Keratoconus / Ectasia Detection with the Oculus Pentacam: Belin / Ambrósio

Enhanced Ectasia Display . Highlights of Ophthalmology. 2009; 35(6):5-12.

Purpose

• To evaluate the change in pachymetry, progression index, front and back elevation points and back difference elevation values in patients of different grades of keratoconus

Materials and Methods• Study site : Tertiary eye institute in Western Maharashtra

• Study design : Secondary data analyses

• Time frame : Conducted between February 2012 – April 2016

• Sample Size :80 eyes of 42 patients of Keratoconus, 30 eyes of 15

normals

• Inclusion criteria : All Patients diagnosed of Keratoconus in the study

period

• Exclusion criteria : Patients of Keratoconus who had undergone

treatment elsewhere and patients who had any other additional corneal

pathology

Materials and Methods• Methodology : - All patients underwent ophthalmic examination(Keratometry, Manifest Refraction, Slit lamp biomicroscopy) and Pentacam measurements of the first visit. - The patients were divided into grades according to Amsler-Krumeich classification. - Pachymetry at the apex(PA) and at the thinnest location(PT) with difference in the distance between PA and PT, Progression Index (PI), front and back elevation points and back difference elevation values were obtained from the Pentacam. - The back difference elevation values were extrapolated from the difference maps of the Belin-Ambrosió enhanced ectasia display of the system.

Results

Pachymetry in all groups

F value P Value

PA 22.32 0.000

PT 19.51 0.000

Results

PI in all groups of KC

F Value P value

PI minimum 16.58 0.000

PI maximum 20.82 0.000

PI average 19.71 0.000

Results

Elevation point Mean Std.

DevP Value

FRONT NM(30) 2.07 1.80 0.000

KC1 (29) 14.55 9.92

BACK NM(30) 4.23 3.74 0.000

KC1 (29) 33.2 21.5

Elevation point in all groups

F Value P Value

Front 1.37 0.000

Back 4.39 0.000

Results

• ‘D ‘Values in all Groups

F Value P

D 47.58 0.000

Df 36.04 0.000

Db 18.60 0.000

‘D ‘ value

Mean Std .Dev

P value

NM (30)

1.159 0.636 0.000

KC1 (29)

6.81 2.94

Discussion• In our study, a descending trend for both PA and at the thinnest

location(PT)was noted for all stages and also for distance between PA and PT. Similar trend in the difference between PA and PT was noted in all groups except stage 3(KC3).

• PI , Front and back elevation points and Back difference elevation points(D,Df,Db,Dp,Dt,Dy) showed an increasing trend in all stages, except Dt and Dy in Stage 3.

• The variation could be due to small sample size in Stage3(KC3=7)• A statistically significant difference was noted between normals and stage 1

KC for all parameters.• Kazutaka Kamiya et al4 also noted similar results for PA,PT and elevation

points with Elevation difference measurements improving the diagnostic accuracy of keratoconus, especially in the early stage of the disease , whereas Xian- Li Du et al5 noted better diagnostic value in moderate stage of KC

• 4 Kazutaka Kamiya,Rie Ishii et al. Evaluation of corneal elevation, pachymetry and keratometry in keratoconic eyes with respect to the stage of Amsler-Krumeich classification.Br J Ophthalmol 2014 Apr;98(4):459-63

• 5 Xian- Li Du et al. Correlation of basic indicators with stages of keratoconus assessed by Pentacam tomography. Int J Ophthalmol. 2015; 8(6): 1136–1140

Conclusion

• All parameters on Pentacam assessed in the study, pachymetric, and elevation based, showed good correlation in all stages of Keratoconus and significant difference than normals.

• All the parameters could be useful to differentiate between normals and stage 1 of keratoconus