Corneal Topographic Study Using Orbscan II between Keratoconus and Keratoconus Suspect

Seung Uk Lee; Chang Hwan Lee; Ji-Eun Lee; Jong Soo Lee

doi:10.3341/jkos.2007.48.12.1599

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Lee, Lee, Lee, and Lee: Corneal Topographic Study Using Orbscan II between Keratoconus and Keratoconus Suspect

Original Article

J Korean Ophthalmol Soc 2007;48(12):1599-1606.

Published online: 30 August 2007

DOI: https://doi.org/10.3341/jkos.2007.48.12.1599

Corneal Topographic Study Using Orbscan II between Keratoconus and Keratoconus Suspect

Seung Uk Lee, M.D.¹, Chang Hwan Lee, M.D.², Ji-Eun Lee, M.D., Ph.D.¹, Jong Soo Lee, M.D., Ph.D.¹

¹Department of Ophthalmology, College of Medicine, Pusan National University, Pusan, Korea

²Department of Ophthalmology, Wallace Memorial Baptist Hospita, Pusan, Korea

Address reprint requests to Jong Soo Lee, M.D., Ph.D., Department of Ophthalmology, Pusan National Unversity Hospital, #1-10 Ami-dong, Seo-gu, Pusan 602-739, Korea Tel: 82-51-240-7319, Fax: 82-51-242-7341, E-mail: jongsool@pusan.ac.kr

Received 4 July 2006 Accepted 14 August 2007

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To compare corneal topographic changes using Orbscn II between keratoconus and keratoconus-suspected eyes.

Methods

Thirty-seven keratoconus eyes, 17 keratoconus-suspected eyes and 37 normal eyes were evaluated by using Orbscan II corneal topography. We compared central phachymetry, anterior elevation from best-fit sphere (BFS), posterior elevation from BFS, most protruded corneal thickness, central corneal thickness, anterior chamber depth, corneal diameter, and pupil size.

Results

Central pachymetry, anterior and posterior elevation from BFS, central corneal thickness, and anterior chamber depth were statistically significantly different between keratoconus and control eyes. Anterior elevation from BFS showed a significant difference between keratoconus-suspected and control eyes. There were statistically significant differences in central pachymetry, posterior elevation from BFS, central corneal thickness and most protruded corneal thickness between keratoconus and keratoconus-suspected eyes. Corneal diameter and pupil size showed no differences among the 3 groups.

Conclusions

Suspected keratoconus eyes have a higher value of anterior elevation from BFS on Orbscan II topography as compared with control eyes. Central pachymetry, posterior elevation from BFS, central corneal thickness and most protruded corneal thickness may be helpful in distinguishing between keratoconus and keratoconus-suspected eyes.

Keywords: Anterior chamber depth, Best fit sphere (BFS), Keratoconus, Keratoconus suspect, Orbscan II corneal topography

References

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Figure 1.

The map of Orbscan II topography in keratoconus. The parameters including central corneal power, anterior and posterior elevation from BFS and central corneal thickness are significantly different from normal eyes.

Figure 2.

The map of Orbscan II topography in keratoconus suspect. Anterior elevation from BFS is the only significantly different parameter comparing with normal eyes, and central corneal power, posterior elevation from BFS, central corneal thickness and most protruded corneal thickness are the parameters significantly different from keratoconic eyes.

Table 1.

Comparison of parameters of Orbscan II system in keratoconic and normal eyes. The parameters including central corneal power, anterior and posterior elevation from BFS and central corneal thickness are significantly different from normal eyes

Parameter	Keratoconic eye	Normal eye	p-value
Central corneal power (Diopter)	48.81±6.33	42.48± 1.71	< 0.001
(Range)	(37.60∼72.06)	(38.98∼44.81)
Anterior elevation from BFS^* (μm)	43.05±27.26	6.80±4.91	< 0.001
(Range)	(4.00∼125.00)	(1.00∼14.00)
Posterior elevation from BFS^* (μm)	93.93±54.64	25.70±7.13	< 0.001
(Range)	(9.00∼225.00)	(15.00∼41.00)
Central corneal thickness (pm)	451.07±61.01	543.65±44.24	< 0.001
(Range)	(282.00∼560.00)	(441.00∼611.00)
Anterior chamber depth (mm)	3.34±0.36	3.07±0.23	0.024
(Range)	(2.64∼4.04)	(2.73∼3.47)
Corneal diameter (mm)	11.74±0.36	11.56±0.45	0.104
(Range)	(11.10∼12.50)	(11.10∼13.00)
Pupil size (mm)	4.91±1.48	5.15± 1.44	0.564
(Range)	(3.20∼10.80)	(3.70∼8.00)

^* Best-fit sphere. (By Scheffe's method)

Table 2.

Comparison of parameters of Orbscan II system in keratoconus-suspected and normal eyes. Anterior elevation from BFS is the only significantly different parameter compared with normal eyes

Parameter	Keratoconus-suspected eye	Normal eye	p-value
Central corneal power (Diopter)	42.74± 1.59	42.48± 1.71	0.999
(Range)	(40.32∼46.12)	(38.98∼44.81)
Anterior elevation from BFS^* (μm)	24.28±7.65	6.80±4.91	0.014
(Range)	(6.00∼37.00)	(1.00∼14.00)
Posterior elevation from BFS^* (μm)	30.72±19.03	25.70±7.13	0.591
(Range)	(1.00∼64.00)	(15.00∼41.00)
Central corneal thickness (pm)	501.84±55.34	543.65±44.24	0.065
(Range)	(362.00∼580.00)	(441.00∼611.00)
Anterior chamber depth (mm)	3.27±0.35	3.07±0.23	0.188
(Range)	(2.45∼3.83)	(2.73∼3.47)
Corneal diameter (mm)	11.81±0.43	11.56±0.45	0.101
(Range)	(10.80∼12.50)	(11.10∼13.00)
Pupil size (mm)	4.95±1.24	5.15±1.44	0.662
(Range)	(3.40∼7.80)	(3.70∼8.00)

^* Best-fit sphere. (By Scheffe's method)

Table 3.

Comparison of parameters of Orbscan II system in keratoconic and keratoconus-suspected eyes. Central corneal power, posterior elevation from BFS, central corneal thickness and most protruded corneal thickness are the parameters significantly differed from keratoconus-suspected eyes

Parameter	Keratoconic eye	Keratoconus suspected eye	p-value
Central corneal power (Diopter)	48.81±6.33	42.74±1.59	< 0.001
(Range)	(37.60∼72.06)	(40.32∼46.12)
Anterior elevation from BFS^* (μm)	43.05±27.26	24.28±7.65	0.980
(Range)	(4.00∼125.00)	(6.00∼37.00)
Posterior elevation from BFS^* (μm)	93.93±54.64	30.72±19.03	< 0.001
(Range)	(9.00∼225.00)	(1.00∼64.00)
Central corneal thickness (μm)	451.07±61.01	501.84±55.34	0.003
(Range)	(282.00∼560.00)	(362.00∼580.00)
Most protruded corneal thickness (μm)	440.05±66.38	497.38±59.13	0.001
(Range)	(280.00∼560.00)	(362.00∼579.00)
Anterior chamber depth (mm)	3.34±0.36	3.27±0.35	0.845
(Range)	(2.64∼4.04)	(2.45∼3.83)
Corneal diameter (mm)	11.74±0.36	11.81±0.43	0.563
(Range)	(11.10∼12.50)	(10.80∼12.50)
Pupil size (mm)	4.91±1.48	4.95± 1.24	0.924
(Range)	(3.20∼10.80)	(3.40∼7.80)

^* Best-fit sphere. (By Scheffe's method)

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