Transcript Document

Risk Factor Analysis of Topographic Progression
in Keratoconus
Seong Joon Ahn, MD1,2, Mee Kum Kim MD, PhD1,2,
Won Ryang Wee, MD, PhD1,2
1Department
of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea
of corneal regenerative medicine and ocular immunology, Seoul Artificial Eye Center, Seoul National University Hospital
Clinical Research Institute, Seoul, Korea
2Laboratory
The authors have no financial interest in the subject matter of this poster.
Introduction

Keratoconus is a progressive noninflammatory disease of the
cornea characterized by central stromal thinning that causes
apical protrusion, irregular astigmatism, and decreased
vision.

In previous studies on keratoconus progression, the criteria
of progression had been diverse.
• From the clinical progression which needed penetrating
keratoplasty
• To several topographic indices such as parameters of corneal
apex, thinnest point, and central point
Table. The criteria for keratoconus progression in previous studies
Author
Year
Number of
Mean age
patients
Sahin et al.1
2008
79
Follow-up period
Indices used for progression
Proportion of
(months)
31.6
24
progressed case
Radius, semimeridian, elevation, pachymetry, tangential NS
curvature, mean spheric curvature at apex and thinnest/center
point, SimK max, SimK min
Kang et al.2
2010
68
22.3
17.5
SimK max, SimK min, Astigmatism, anterior/posterior NS
elevation, corneal thinnest/central pachymetry, anterior/
posterior best fit sphere value
Suzuki et al.3
2009
34
24.1
72
Regular
astigmatism,
asymmetry,
and
higher-order NS
irregularity component in the central 3 mm zone.
Hwang et al.4
2010
107 eyes
24.5
22.6/20.5*
Sim Kmax, Sim Kmin, apical power, astigmatic index, NS
irregularity index, anterior elevation
Weed et al.5
2007
364 eyes
19/24
1004 days
Progression to corneal graft surgery
4%
Reeves et al.6
2005
131 eyes
37.1
NS
Progression to penetrating keratoplasty
45%
Li et al.7
2007
369
32/39*
4.0/3.8* years
Central K (CK), I-S, and KISA values
NS
McMahon et al.8
2006
1032
38.9
8 years
Flat K
24.1% (> or = 3.0D)
Oshika et al.9
2002
64
28.3
≥1 year
Spherical component, regular astigmatism, decentration NS
component, and higher order irregularity
* Follow-up periods and mean ages were denoted as those in lens-wearing or keratoconus group / those in control group.
Purpose

We intended to develop the criterion for topographic
progression of keratoconus.
• By including many topographic parameters which were reported
previously

Using the criterion, all patients were classified into
progressed or non-progressed cases.

Subsequently, we performed risk factor analysis to
explore associated factors with topographic progression.
Methods

Retrospective study
• The patients who visited Seoul National University Hospital from
May 2005 to July 2009
• Inclusion criteria
• Patients who underwent follow-up examinations for more than 2 yrs.
• In patients who underwent surgical treatment, the preoperative follow-up
examinations were performed for more than 2 years.
• Orbscan II topography were performed more than twice.
• Exclusion criteria
• Any surgical treatment before the first visit
• Corneal topography was performed using Orbscan II (Bausch &
Lomb, Claremont, CA).

In total, 211 eyes of 128 patients were included.
Methods

Previously used 8 topographic indices suggesting progression in earlier studies
• Increase in
• Simulated K (SimK), astigmatism
• Irregularity index of 3 mm and 5 mm
• Anterior and posterior elevation
• Inferior minus superior (I-S value) asymmetry
• Decrease in
• Thinnest-point pachymetry

The criterion for topographic progression
• Patient showing ≥ 5 progressed parameters compared to baseline examination
• This criterion has the greatest value of kappa with gold standard (progression to
keratoplasty)

Logistic analysis was performed to evaluate the risk factors associated with
topographic progression.
• Age, sex, the age of diagnosis, the use and duration of contact lens, follow-up period,
•
severity at initial visit, atopic disease, slit-lamp findings.
Using Statistical Package for the Social Sciences (SPSS) Ver. 12.0
Results
Table. Comparision of clinical features and treatment methods between patients with and without
progression
Clinical characteristics
Progression (n=94)
No Progression (n=117)
p value*
Sex (M:F)
58.5%:41.5%
59.0%:41.0%
0.946
Age of diagnosis
22.235.65†
24.657.87
0.049
Follow-up period (months)
43.112.4
40.7  14.0
0.214
History of atopic disease
12 (12.7%)
15 (12.8%)
0.991
Severity of keratoconus
7:54:33‡
6:59:42
0.764
Glasses prescription
10 (10.6%)
11 (9.4%)
0.781
Contact lens use
76 (80.9%)
98 (83.8%)
0.487
Keratoplasty
21 (22.3%)
16 (13.8%)
0.098
Central PEE
25 (26.6%)
33 (28.2%)
0.795
Corneal opacity
15 (15.6%)
29 (24.8%)
0.126
Treatment
Slit lamp findings
* P value was obtained by Chi-square test for nominal or interval variables and Student’s t test for continuous variables.
† Mean  standard deviation
‡ Mild (central K < 45D) : Moderate (45  central K  52D ) : Severe (central K > 52D)
Results
Table. Comparison of topographic parameters at baseline and follow-up examinations between patients
with and without progression
With progression
Without progression
Index
P value for change*
Baseline
Follow-up
Baseline
Follow-up
SimK max
50.04.7
52.15.4
52.16.1
51.15.0
<0.001
Corneal astigmatism
3.92.6
5.12.8
5.23.4
4.22.6
<0.001
Irregularity at 3mm
5.52.7
6.22.5
6.32.9
5.12.7
<0.001
Irregularity at 5mm
6.23.2
6.52.6
7.13.2
6.02.8
<0.001
Thinnest-point pachymetry
44373
43678.3
43285
44491.1
<0.001
Anterior elevation
29.418.5
34.920.1
37.022.2
30.321.2
0.045
Posterior elevation
63.738.8
77.644.9
86.041.5
71.245.6
<0.001
6.03.6
7.04.2
7.13.8
4.53.3
<0.001
Inferior minus superior
(I-S) index
*The change of a topographic parameter was calculated by subtraction of the value at baseline from that at the last follow-up.
The value was compared between patients with and without progression using Student’s t test.
• Logistic analysis for risk factors of topographic progression
• Age of onset was the only risk factor for the progression
• OR = 0.948 (95% confidence interval = 0.907 - 0.991), p value = 0.010
Discussion

This study developed the criterion which determines
whether keratoconic eye is topographically progressed or not.
• Despite its clinical usefulness, there has been no trial to develop the
criterion.
• Keratoconic eye have diverse changes in several topographic indices.
If some patients show progressive changes in only a few indices but
these indices were used for the criterion for keratoconus progression,
bias can come.
• We used various (8) parameters to evaluate topographic progression in
•
keratoconus.
Progression in equal to or more than 5 parameters indicates generalized
progressive changes in corneal topography.
• We set gold standard as progression to keratoplasty and the most
agreeable criterion with gold standard was chosen.
• Thus, patients with topographic progression under our criterion may
have greater chance of keratoplasty.
Discussion

Under the criterion of topographic progression,
younger age was discovered to be a risk factor of
topographic progression.
• Age is a well-known risk factor of keratoconus
progression.3,6,8
• Our study confirmed it, using a new criterion for
topographic progression.
Summary


Our study developed the criterion for topographic
progression of keratoconus and suggests that
younger age is a risk factor for the progression.
In clinical practice,
• Clinicians can envisage the course of keratoconus in
•
individual patients with patients’ age
The decision on the surgical treatment can be supported
using the criterion.
References
1. Sahin, A., N. Yildirim, et al. (2008). "Two-year interval changes in Orbscan II
topography in eyes with keratoconus." J Cataract Refract Surg 34(8): 1295-1299.
2. Kang, Y. S., Y. K. Park, et al. (2010). "The effect of the YK lens in keratoconus."
Ophthalmic Physiol Opt 30(3): 267-273.
3. Shirayama-Suzuki, M., S. Amano, et al. (2009). "Longitudinal analysis of corneal
topography in suspected keratoconus." Br J Ophthalmol 93(6): 815-819.
4. Hwang, J. S., J. H. Lee, et al. (2010). "Effects of multicurve RGP contact lens use on
topographic changes in keratoconus." Korean J Ophthalmol 24(4): 201-206.
5. Weed, K. H., C. J. Macewen, et al. (2007). "The Dundee University Scottish
Keratoconus Study II: a prospective study of optical and surgical correction." Ophthalmic
Physiol Opt 27(6): 561-567.
6. Reeves, S. W., S. Stinnett, et al. (2005). "Risk factors for progression to penetrating
keratoplasty in patients with keratoconus." Am J Ophthalmol 140(4): 607-611.
7. Li, X., H. Yang, et al. (2007). "Longitudinal study of keratoconus progression." Exp Eye
Res 85(4): 502-507.
8. McMahon, T. T., T. B. Edrington, et al. (2006). "Longitudinal changes in corneal
curvature in keratoconus." Cornea 25(3): 296-305.
9. Oshika, T., T. Tanabe, et al. (2002). "Progression of keratoconus assessed by fourier
analysis of videokeratography data." Ophthalmology 109(2): 339-342.