Journal List > J Korean Ophthalmol Soc > v.50(11) > 1008429

TOOLS
Jo, Oh, Kim, Lee, and Wee: Corneal Power Estimation Using Orbscan II Videokeratography in Eyes With Previous Corneal Refractive Surgeries
Original Article

J Korean Ophthalmol Soc 2009;50(11):1730-1734.

Published online: 31 August 2009

DOI: https://doi.org/10.3341/jkos.2009.50.11.1730

Corneal Power Estimation Using Orbscan II Videokeratography in Eyes With Previous Corneal Refractive Surgeries

Dong Hyun Jo, MD1, Joo Youn Oh, MD, PhD1, Mee Kum Kim, MD, PhD1, 2, Jin Hak Lee, MD, PhD1, 2, Won Ryang Wee, MD, PhD1, 2

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

2Seoul Artificial Eye Center, Seoul National University Hospital Clinical Research Institute, Seoul, Korea

Address reprint requests to Won Ryang Wee, MD, PhD, Department of Ophthalmology, Seoul National University College of Medicine #28 Yeongeon-dong, Jongno-gu, Seoul 110-744, Korea Tel: 82-2-2072-2435, Fax: 82-2-741-3187, E-mail: wrwee@snu.ac.kr

Received 29 April 2009       Accepted 4 August 2009

Copyright © 2009 Korean Ophthalmological Society

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 report three cases of corneal power estimation for intraocular lens power calculation using Orbscan II videokeratography in eyes with previous corneal refractive surgeries.

Case summary

In three eyes of three patients with previous corneal refractive surgeries, corneal power values were respectively measured at three, four, five, six mm-diameter zones of total mean, axial, tangential, and optical maps using Orbscan II videokeratography. Then, intraocular lens power values were calculated via the SRK/T formula. After cataract surgeries, back-calculated corneal power (BCK) values were estimated from post-phacoemulsification refraction data, and compared with those measured at three, four, five, six mm-diameter zones of each map in Orbscan II videokeratography. The postoperative refractive values after cataract surgeries were achieved within 1.5D of the target refraction in all eyes by using five mm total axial power and four mm total optical power for intraocular lens power calculation. Orbscan II parameters including three mm, four mm total axial power, and three mm total optical power were the least different from the BCK (0.69±0.49D, 1.08±0.54D, and 1.10±0.44D, respectively).

Conclusions

If historical data are not available, Orbscan II videokeratography can be useful for estimating corneal power for intraocular lens power calculations in patients with previous corneal refractive surgeries.

Keywords: Cataract surgery, Corneal refractive surgery, Intraocular lens, IOL power calculation, Orbscan videokeratography

References

1. Tang M, Li Y, Avila M, Huang D. Measuring total corneal power before and after laser in situ keratomileusis with high-speed optical coherence tomography. J Cataract Refract Surg. 2006; 32:1843–50.
crossref
2. Holladay J. IOL calculations following RK. Refract Corneal Surg. 1989; 5:203.
3. Hoffer KJ. Intraocular lens power calculation for eyes after refractive keratectomy. J Refract Surg. 1995; 111:490–3.
4. Seitz B, Langenbucher A. Intraocular lens calculations status after corneal refractive surgery. Curr Opin Ophthalmol. 2000; 11:35–46.
crossref
5. Latkany RA, Chokshi AR, Speaker MG, et al. Intraocular lens calculations after refractive surgery. J Cataract Refract Surg. 2005; 31:562–70.
crossref
6. Haigis W. Corneal power after refractive surgery for myopia: contact lens method. J Cataract Refract Surg. 2003; 29:1397–1411.
crossref
7. Shammas HJ, Shammas MC. No-history method of intraocular lens power calculation for cataract surgery after myopic laser in situ keratomileusis. J Cataract Refract Surg. 2007; 33:31–6.
crossref
8. Srivannaboon S, Reinstein DZ, Sutton HF, Holland SP. Accuracy of Orbscan total optical power maps in detecting refractive change after myopic laser in situ keratomileusis. J Cataract Refract Surg. 1999; 25:1596–99.
crossref
9. Han ES, Lee JH. Intraocular lens power calculation in high myopic eyes with previous radial keratotomy. J Refract Surg. 2006; 22:713–16.
crossref
10. Qazi MA, Cua IY, Roberts CJ, Pepose JS. Determining corneal power using Orbscan II videokeratography for intraocular lens calculation after excimer laser surgery for myopia. J Cataract Refract Surg. 2007; 33:21–30.
crossref
11. Kurli M, Finger PT. Melanocytic conjunctival tumors. Ophthalmol Clin North Am. 2005; 18:15–24.
crossref
12. Menassa N, Kaufmann C, Goggin M, et al. Comparison and reproducibility of corneal thickness and curvature readings obtained by the Galilei and the Orbscan II analysis systems. J Cataract Refract Surg. 2008; 34:1742–47.
crossref
13. Kawamorita T, Uozato H, Kamiya K, et al. Repeatability, reproducibility, and agreement characteristics of rotating Scheimpflug photography and scanning-slit corneal topography for corneal power measurement. J Cataract Refract Surg. 2009; 35:127–133.
crossref
14. Cho HJ, Koo OS. Comparison of refraction-derived keratometric value and orbscan corneal power after laser in situ keratomileusis. J Korean Ophthalmol Soc. 2005; 46:623–8.

Table 1.
Demographic data and clinical features
Characteristics Case 1 Case 2 Case 3
Age (years) 51 63 42
Laterality Right Right Right
Type of corneal refractive surgery LASIK* LASIK PRK†
Interval between LASIK/PRK and cataract surgery (months) 37 132 240
Pre-cataract surgery spherical equivalent (diopters) −8.5 −2.375 N/A‡
UCVA§ before cataract surgery (20/) 300 200 200
BCVA∏ before cataract surgery (20/) 30 N/A N/A
Axial length (mm) 26.73 25.8 26.36

*LASIK=laser in situ keratomileusis

†PRK=photorefractive keratectomy

‡not available due to white cataract

§UCVA=uncorrected visual acuity

∏BCVA=best corrected visual acuity.

Table 2.
The Orbscan-derived keratometric values from 4 different power maps
  Case 1 Case 2 Case 3
Simulated K readings 38.4 41.8 41.5
3 mm zone 38.6 42.3 42.3
5 mm zone 41.9 43.6 43.4
Total mean power 3 mm 36.5317 40.3211 39.75
Total mean power 4 mm 37.4052 41.1473 40.8533
Total mean power 5 mm 39.0093 42.3808 41.6714
Total mean power 6 mm 40.7298 43.4473 41.9979
Total axial power 3 mm 35.8777 39.9967 38.287
Total axial power 4 mm 36.1463 40.1269 39.0487
Total axial power 5 mm 36.6661 40.6061 39.8009
Total axial power 6 mm 37.5603 41.2601 40.4422
Total tangential power 3 mm 36.641 39.7226 40.304
Total tangential power 4 mm 37.4911 41.2387 42.1397
Total tangential power 5 mm 40.1504 43.395 43.4647
Total tangential power 6 mm 43.366 45.6863 43.6561
Total optical power 3 mm 36.2351 40.4386 38.7261
Total optical power 4 mm 36.5944 40.7015 39.6429
Total optical power 5 mm 37.2758 41.4137 40.6279
Total optical power 6 mm 38.4543 42.3911 41.5681
Table 3.
Comparison of target refraction and real refraction after cataract surgery
  Case 1 Case 2 Case 3
Target refraction (D) 0 0 −1.5
Spherical equivalent 1 week after surgery (D) 1.75 0.25 N/A
Spherical equivalent 1 month after surgery (D) 1.125 0 0
Difference between target and real refraction (D) 1.125 0 1.5
Table 4.
Comparison of back-calculated keratometric value (BCK) value and Orbscan II parameters (Orbscan II parameters –BCK value)
    Case 1 Case 2 Case 3 Average
Total mean power 3 mm +1.9017 +0.6711 +1.94 +1.50
  4 mm +2.7752 +1.4973 +3.0433 +2.43
  5 mm +4.3793 +2.7308 +3.8614 +3.65
  6 mm +6.0998 +3.7973 +4.1879 +4.69
Total axial power 3 mm +1.2477 +0.3467 +0.477 +0.69
  4 mm +1.5163 +0.4769 +1.2387 +1.07
  5 mm +2.0361 +0.9561 +1.9909 +1.66
  6 mm +2.9303 +1.6101 +2.6322 +2.39
Total tangential power 3 mm +2.011 +0.0726 +2.494 +1.52
  4 mm +2.8611 +1.5887 +4.3297 +2.92
  5 mm +5.5204 +3.745 +5.6547 +4.97
  6 mm +8.736 +6.0363 +5.8461 +6.87
Total optical power 3 mm +1.6051 +0.7886 +0.9161 +1.10
  4 mm +1.9644 +1.0515 +1.8329 +1.61
  5 mm +2.6458 +1.7637 +2.8179 +2.40
  6 mm +3.8243 +2.7411 +3.7581 +3.44
TOOLS
Similar articles