The Importance of the Correlation between CCT and Corneal Curvature in Refractive Surgery

ORIGINAL ARTICLE
Mimoza Ismaili

 
For citation: Ismaili M. The Importance of the Correlation between CCT and Corneal Curvature in Refractive Surgery. International Journal of Biomedicine. 2025;15(2):299-304. doi:10.21103/Article15(2)_OA5
 
Originally published June 5, 2025
 

Abstract: 

Background: The aim of this study was to analyze the relationship between central corneal thickness (CCT) and corneal curvature (CC) in patients with refractive anomalies and emmetropes, in three different age groups.
Methods and Results: The study included 330 respondents, with a total of 660 eyes, divided into two groups. The test group included 180 respondents with refractive anomalies (65 respondents with hypermetropia, 65 with myopia, and 50 with astigmatism); the control group included 150 emmetropic respondents with uncorrected visual acuity (VA) – 6/6 in both eyes.  Corneal curvature was measured by automated keratometry. We analyzed mean CC (Km), also known as mean keratometry, which is the average of the two major meridians of CC (K1 and K2) measured in diopters (D). CCT was measured by ultrasonic pachymetry.
The mean CCT in the myopic group was 521.0±28.2 μm, which was lower than in both the control group (550.0±18.0 μm) and the astigmatic groups (530.3±30.0 μm).  In the emmetropic group, with increasing age, the CCT values decreased from 557.6±19.7 μm in the age group <20 years to 549.5±15.7 μm in the age group 20–29 years and 545.5±4.0 μm in the age group ≥30 years (P<0.001). In the groups of patients with refractive abnormalities, we did not find a significant difference between the mean CCT values depending on the age of the patients (P>0.05). In the astigmatism and emmetropic groups, we found no statistically significant difference between the mean CCT values depending on gender (P>0.05). In the hypermetropic group, the mean CCT values were higher in women (569.1 ± 28.9 μm) than in men (555.1 ± 23.5 μm) (P=0.008). At the same time, in the myopic group, the CCT values were higher in men (529.5 ± 28.0 μm) than in women (516.0 ± 41.8 μm) (P=0.049). Regarding the correlation between CCT and CC, we found no significant correlation in the hypermetropic (rs=-0.101; P=0.249) and myopic (rs=-0.0101; P=0.869) groups. However, a statistically significant low negative correlation was found between CCT and Km in the astigmatism group (rs=-0.322; P=0.001), and a statistically significant low positive correlation was found between CCT and Km in the control group (rs=0.144; P=0.0120).
Conclusion: CCT is found to be thicker in hypermetropic patients than in emmetropes. With increasing age, the cornea tends to become thinner. We found no significant correlation between the CCT values and corneal keratometry. Also, we found that in the astigmatism group, the CCT values were higher in the corneal keratometric group 42-48D. The cornea is inclined to become thinner and steeper in myopes. These biometric findings will serve to update and advance protocols in refractory surgery.

Keywords: 
central corneal thickness • corneal curvature • refractive anomalies
References: 
  1. Ehlers N, Bramsen T, Sperling S. Applanation tonometry and central corneal thickness. Acta Ophthalmol (Copenh). 1975 Mar;53(1):34-43. doi: 10.1111/j.1755-3768.1975.tb01135.x. PMID: 1172910.
  2. Jobke S, Kasten E, Vorwerk C. The prevalence rates of refractive errors among children, adolescents, and adults in Germany. Clin Ophthalmol. 2008 Sep;2(3):601-7. doi: 10.2147/opth.s2836. PMID: 19668760; PMCID: PMC2694012.
  3. Opubiri I, Adio A, Megbelayin E. Refractive error pattern of children in South-South Nigeria: A tertiary hospital study. Sky J Med & Med Sci. 2013;1: 10-4.
  4. Rai S, Thapa HB, Sharma MK, Dhakhwa K, Karki R. The distribution of refractive errors among children attending Lumbini Eye Institute, Nepal. Nepal J Ophthalmol. 2012 Jan-Jun;4(1):90-5. doi: 10.3126/nepjoph.v4i1.5858. PMID: 22344004.
  5. Holden BA, Sulaiman S, Knox K. The challenge of providing spectacles in the developing world. Community Eye Health. 2000;13(33):9-10. PMID: 17491946; PMCID: PMC1705961.
  6. Wojciechowski R. Nature and nurture: the complex genetics of myopia and refractive error. Clin Genet. 2011 Apr;79(4):301-20. doi: 10.1111/j.1399-0004.2010.01592.x. Epub 2010 Dec 13. PMID: 21155761; PMCID: PMC3058260.
  7. Remón L, Monsoriu JA, Furlan WD. Influence of different types of astigmatism on visual acuity. J Optom. 2017 Jul-Sep;10(3):141-148. doi: 10.1016/j.optom.2016.07.003. Epub 2016 Sep 14. PMID: 27639497; PMCID: PMC5484781.
  8. Crawford JS, Shagass C,Pashby TJ. Relationship between visual acuity and refractive error in myopia. Am J Ophthalmol. 1945;28:1220–1225. 
  9. Boltz RL, Manny RE, Katz BJ. Effects of induced optical blur on infant visual acuity. Am J Optom Physiol Opt. 1983 Feb;60(2):100-5. doi: 10.1097/00006324-198302000-00002. PMID: 6846483.
  10. Smith G, Jacobs RJ, Chan CD. Effect of defocus on visual acuity as measured by source and observer methods. Optom Vis Sci. 1989 Jul;66(7):430-5. doi: 10.1097/00006324-198907000-00004. PMID: 2771329.
  11. Read SA, Vincent SJ, Collins MJ. The visual and functional impacts of astigmatism and its clinical management. Ophthalmic Physiol Opt. 2014 May;34(3):267-94. doi: 10.1111/opo.12128. Epub 2014 Mar 18. PMID: 24635572.
  12. Hashemi H, Mehravaran S. Central corneal thickness measurement with Pentacam, Orbscan II, and ultrasound devices before and after laser refractive surgery for myopia. J Cataract Refract Surg. 2007 Oct;33(10):1701-7. doi: 10.1016/j.jcrs.2007.05.040. PMID: 17889763.
  13. Ismaili M. Association Between Central Corneal Thickness and Intraocular Pressure in Patients with Refractive Anomalies and Emmetropes. International Journal of Biomedicine. 2023;13(3):91-95. doi:10.21103/Article13(3)_OA6
  14. Ismaili M. Association between Central Corneal Thickness and Axial Length in Patients with Refractive Anomalies and Emmetropes. International Journal of Biomedicine. 2023;13(3):96-100. doi:10.21103/Article13(3)_OA7
  15. Navyasree C, Satapathy J.Correlation of Central Corneal Thickness with Refractive Error, Corneal Curvature, and Axial Length: An Observational Study. TNOA Journal of Ophthalmic Science and Research. 2024;62(1):75-79.
  16. Lee S, Kim B, Oh TH, Kim HS. Correlations between magnitude of refractive error and other optical components in Korean myopes. Korean J Ophthalmol. 2012 Oct;26(5):324-30. doi: 10.3341/kjo.2012.26.5.324. Epub 2012 Sep 24. PMID: 23060718; PMCID: PMC3464315.
  17. Koucheki B, Mehravaran S, Hashemi H. Correlation Between Central Corneal Thickness and Refractive Indices in a Laser Refractive Surgery Population. Iranian Journal of Ophthalmology. 2010;22:43-48.
  18. Galgauskas S, Juodkaite G, Tutkuvienė J. Age-related changes in central corneal thickness in normal eyes among the adult Lithuanian population. Clin Interv Aging. 2014 Jul 16;9:1145-51. doi: 10.2147/CIA.S61790. PMID: 25075183; PMCID: PMC4106961.
  19. Kamiya K, Shimizu K, Ohmoto F. Effect of aging on corneal biomechanical parameters using the ocular response analyzer. J Refract Surg. 2009 Oct;25(10):888-93. doi: 10.3928/1081597X-20090917-10. Epub 2009 Oct 12. PMID: 19835329.
  20. Mercieca K, Odogu V, Fiebai B, Arowolo O, Chukwuka F. Comparing central corneal thickness in a sub-Saharan cohort to African Americans and Afro-Caribbeans. Cornea. 2007 Jun;26(5):557-60. doi: 10.1097/ICO.0b013e3180415d90. PMID: 17525651.
  21. Nayak A, Niveditha H, Vishnuvardhan B. Comparison of intraocular pressure & central corneal thickness amongst hypermetropes & myopes in adult Indian subjects. JMSCR. July 2019;7(7).
  22. Kadhim YJ, Farhood QK. Central corneal thickness of Iraqi population in relation to age, gender, refractive errors, and corneal curvature: a hospital-based cross-sectional study. Clin Ophthalmol. 2016 Nov 25;10:2369-2376. doi: 10.2147/OPTH.S116743. PMID: 27932859; PMCID: PMC5135410.
  23. Saxena AK, Bhatnagar A and Thakur S. Central Corneal Thickness: Important Considerate in Ophthalmic Clinic. Austin J Clin Ophthalmol. 2017; 4(1): 1076.
  24. Nomura H, Ando F, Niino N, Shimokata H, Miyake Y. The relationship between age and intraocular pressure in a Japanese population: the influence of central corneal thickness. Curr Eye Res. 2002 Feb;24(2):81-5. doi: 10.1076/ceyr.24.2.81.8161. PMID: 12187477.
  25. Lekskul M, Aimpun P, Nawanopparatskul B, Bumrungsawat S, Trakulmungkijkarn T, Charoenvanichvisit J, Herunpattarawong T, Suksangthong P, Jaiprasat T, Rattananantapat M, Sudprasert T. The correlations between Central Corneal Thickness and age, gender, intraocular pressure and refractive error of aged 12-60 years old in rural Thai community. J Med Assoc Thai. 2005 Nov;88 Suppl 3:S175-9. PMID: 16858956.
  26. Eballe AO, Koki G, Ellong A, Owono D, Epée E, Bella LA, Mvogo CE, Kouam JM. Central corneal thickness and intraocular pressure in the Cameroonian nonglaucomatous population. Clin Ophthalmol. 2010 Jul 30;4:717-24. doi: 10.2147/opth.s10575. PMID: 20689788; PMCID: PMC2915858.
  27. Suzuki S, Suzuki Y, Iwase A, Araie M. Corneal thickness in an ophthalmologically normal Japanese population. Ophthalmology. 2005 Aug;112(8):1327-36. doi: 10.1016/j.ophtha.2005.03.022. PMID: 15964631.
  28. Muthu Krishnan V, Jayalatha K, Vijayakumar C. Correlation of Central Corneal Thickness and Keratometry with Refraction and Axial Length: A Prospective Analytic Study. Cureus. 2019 Jan 19;11(1):e3917. doi: 10.7759/cureus.3917. PMID: 30931188; PMCID: PMC6426576.
  29. Mostafa A, Mohamed M, Mohamed M.  Correlation between Central Corneal Thickness and Degree of Myopia TheThe Egyptian Journal of Hospital Medicine (January 2018) Vol. 70, Page 109-113.
  30. Maria Pramod, Smitha V K. Correlation of Central Corneal Thickness and Corneal Curvature with Refractive Error in South Indian Population. Journal of Cardiovascular Disease Research. 2023;14(10).
  31. Thakur S, Saxena AK, Bhatnagar A. Central corneal thickness: Important considerate in ophthalmic clinic. Journal of Mahatma Gandhi Institute of Medical Sciences. Jul-Dec 2021;26(2):77-80.
  32. Shobita N, Selvam VP, Shah VJ, Radha J, Vijayraghavan V and Amalet G, et al. Correlation of Central Corneal Thickness with Refractive Errors and Corneal Curvature in the South Indian Population. Acta Scientific Ophthalmology.2021;4:31-38.
  33. Liu Z, Pflugfelder SC. The effects of long-term contact lens wear on corneal thickness, curvature, and surface regularity. Ophthalmology. 2000 Jan;107(1):105-11. doi: 10.1016/s0161-6420(99)00027-5. PMID: 10647727.
  34. Villegas EA, Alcón E, Artal P. Minimum amount of astigmatism that should be corrected. J Cataract Refract Surg. 2014 Jan;40(1):13-9. doi: 10.1016/j.jcrs.2013.09.010. PMID: 24355718.
  35. Hashmani N, Hashmani S, Hanfi AN, Ayub M, Saad CM, Rajani H, Muhammad MG, Aziz M. Effect of age, sex, and refractive errors on central corneal thickness measured by Oculus Pentacam®. Clin Ophthalmol. 2017 Jun 30;11:1233-1238. doi: 10.2147/OPTH.S141313. PMID: 28721008; PMCID: PMC5501622.

Download Article
Received February 24, 2025.
Accepted April 7, 2025.
©2025 International Medical Research and Development Corporation.