Evaluation of Anterior, Posterior, and Total Corneal Astigmatism in Normal Subjects

Document Type : Original Article (s)

Authors

1 MSc Student, Department of Optometry, School of Rehabilitation, Shahid Beheshti University of Medical Sciences, Tehran, Iran

2 Professor, Department of Optometry, School of Rehabilitation, Shahid Beheshti University of Medical Sciences, Tehran, Iran

3 Associate Professor, Department of Ophthalmology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran

4 Instructor, Department of Epidemiology and Biostatistics, School of Rehabilitation, Shahid Beheshti University of Medical Sciences, Tehran, Iran

5 Ophthalmic Research Center, Isfahan Parsian Clinic, Isfahan, Iran

Abstract

Background: The aim of this study was to evaluate the magnitude and axis orientation of anterior, posterior, and total corneal astigmatism (ACA, PCA, and TCA, respectively).Methods: In this retrospective study, pentacam topographical maps of 226 eyes (113 patients) with 1.0 to 6.0 diopters (D) of astigmatism were analyzed. Topographical anterior and posterior corneal surface astigmatism was determined. The magnitude and axis orientation of the anterior, posterior and total corneal astigmatism were compared.Findings: The mean age of the study population was 33.00 ± 6.74 years. The mean magnitude was 2.02 ± 0.99, 0.44 ± 0.20, and 1.98 ± 1.01 diopters for anterior, posterior, and total corneal astigmatism, respectively. Most eyes had with-the-rule (WTR) anterior astigmatism and against-the-rule (ATR) posterior astigmatism. With-the-rule astigmatism had a higher mean magnitude compared to against-the-rule and oblique astigmatism in anterior and posterior corneal astigmatism groups. Posterior corneal astigmatism magnitude exceeded 0.75 diopters in only 8% of the subjects. Anterior corneal astigmatism had a significant positive correlation with posterior and total corneal astigmatism (P < 0.001 for both, r = 0.83 and 0.98, respectively). Moreover, posterior corneal astigmatism had a significant positive correlation with total corneal astigmatism (P < 0.001, r = 0.78).Conclusion: The provided information of this study may be helpful in obtaining optimum results in astigmatism correction in refractive surgery or designing new intraocular lenses.

Keywords

References

  1. Cheng LS, Tsai CY, Tsai RJ, Liou SW, Ho JD. Estimation accuracy of surgically induced astigmatism on the cornea when neglecting the posterior corneal surface measurement. Acta Ophthalmol 2011; 89(5): 417-22.
  2. Hoffer KJ. Biometry of 7,500 cataractous eyes. Am J Ophthalmol 1980; 90(3): 360-8.
  3. Ferrer-Blasco T, Montes-Mico R, Peixoto-de-Matos SC, Gonzalez-Meijome JM, Cervino A. Prevalence of corneal astigmatism before cataract surgery. J Cataract Refract Surg 2009; 35(1): 70-5.
  4. Olsen T. On the calculation of power from curvature of the cornea. Br J Ophthalmol 1986; 70(2): 152-4.
  5. Ho JD, Liou SW, Tsai RJ, Tsai CY. Effects of aging on anterior and posterior corneal astigmatism. Cornea 2010; 29(6): 632-7.
  6. Koch DD, Ali SF, Weikert MP, Shirayama M, Jenkins R, Wang L. Contribution of posterior corneal astigmatism to total corneal astigmatism. J Cataract Refract Surg 2012; 38(12): 2080-7.
  7. Mohammadi M, Naderan M, Pahlevani R, Jahanrad A. Prevalence of corneal astigmatism before cataract surgery. Int Ophthalmol 2016; 36(6): 807-17.
  8. Ho JD, Tsai CY, Liou SW. Accuracy of corneal astigmatism estimation by neglecting the posterior corneal surface measurement. Am J Ophthalmol 2009; 147(5): 788-95, 795.
  9. Swartz T, Marten L, Wang M. Measuring the cornea: the latest developments in corneal topography. Curr Opin Ophthalmol 2007; 18(4): 325-33.
  10. Barkana Y, Gerber Y, Elbaz U, Schwartz S, Ken-Dror G, Avni I, et al. Central corneal thickness measurement with the Pentacam Scheimpflug system, optical low-coherence reflectometry pachymeter, and ultrasound pachymetry. J Cataract Refract Surg 2005; 31(9): 1729-35.
  11. Lackner B, Schmidinger G, Skorpik C. Validity and repeatability of anterior chamber depth measurements with Pentacam and Orbscan. Optom Vis Sci 2005; 82(9): 858-61.
  12. Buehl W, Stojanac D, Sacu S, Drexler W, Findl O. Comparison of three methods of measuring corneal thickness and anterior chamber depth. Am J Ophthalmol 2006; 141(1): 7-12.
  13. Fitzmaurice GM, Laird NM, Ware JH. Applied longitudinal analysis. Hoboken, NJ: Wiley; 2012.
  14. Miyake T, Shimizu K, Kamiya K. Distribution of posterior corneal astigmatism according to axis orientation of anterior corneal astigmatism. PloS One 2015; 10(1): e0117194.
  15. Nemeth G, Berta A, Lipecz A, Hassan Z, Szalai E, Modis L, Jr. Evaluation of posterior astigmatism measured with Scheimpflug imaging. Cornea 2014; 33(11): 1214-8.
  16. Tonn B, Klaproth OK, Kohnen T. Anterior surface-based keratometry compared with Scheimpflug tomography-based total corneal astigmatism. Invest Ophthalmol Vis Sci 2014; 56(1): 291-8.
  17. Eom Y, Kang SY, Kim HM, Song JS. The effect of posterior corneal flat meridian and astigmatism amount on the total corneal astigmatism estimated from anterior corneal measurements. Graefes Arch Clin Exp Ophthalmol 2014; 252(11): 1769-77.
  18. Feizi S, Naderan M, Ownagh V, Sadeghpour F. Distribution of the anterior, posterior, and total corneal astigmatism in healthy eyes. Int Ophthalmol 2017. [Epub ahead of print].
  19. Koch DD, Jenkins RB, Weikert MP, Yeu E, Wang L. Correcting astigmatism with toric intraocular lenses: effect of posterior corneal astigmatism. J Cataract Refract Surg 2013; 39(12): 1803-9.
  20. Kim H. Correlation between Anterior and Posterior Corneal Astigmatism in Total Corneal Astigmatism. J Korean Ophthalmic Opt Soc 2014; 19(3): 377-82.
Journal of Isfahan Medical School
Volume 35, Issue 450 - Serial Number 450
September and October 2017
Pages 1382-1388

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History

  • Receive Date: 08 September 2017
  • Revise Date: 27 May 2024
  • Accept Date: 06 April 2022

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