Corneal Aberrations in Keratoconus: A Pentacam Scheimpflug Imaging Study

Abstract

Objective To investigate high-order corneal aberration alterations at different KC stages using a Pentacam Scheimpflug camera (OCULUS, Wetzlar, Germany), and to compare data with healthy eyes Materials and Methods This retrospective comparative study investigated clinical data of 50 patients (100 eyes) with KC and 59 healthy individuals (118 eyes) who underwent corneal topography using the Pentacam Scheimpflug camera in our clinic. Demographic characteristics, total aberrations, HOAs, coma and spherical aberrations of all participants were extracted and recorded. Results Mean age in the KC group was 29.7±10.3 years and 32.1±12.4 years in the control group. These two groups were compatible in terms of age and sex (P=0.11; P=0.76, respectively,). In the keratometric classification, KC was mild in 63, moderate in 23, and severe in 14 eyes. Differences in low-order astigmatism, trefoil, coma, tetra-foil, high-order astigmatism, high-order spherical aberration, and root mean square values between eyes with KC and healthy eyes were statistically significant (P<0.05). In addition, there were statistically significant differences in the corneal aberrations between the keratometric classification groups. Conclusions There is direct proportionality between the KC stage and corneal HOA changes, which may be helpful for staging and improving the safety of refractive surgery.

Keywords

• Corneal Aberrations
• Corneal Topography;
• Irregular Corneal Astigmatism
• Keratoconus
• Pentacam Scheimpflug Camera

Keratokonustaki Korneal Sapmalar: Bir Pentacam Scheimpflug Görüntüleme Çalışması

Abstract

Amaç Farklı keratokonus evrelerindeki yüksek dereceli kornea aberasyon değişikliklerini Pentacam Scheimpflug kamera ile araştırmak ve verileri sağlıklı gözlerle karşılaştırmak Gereç ve Yöntem Bu retrospektif karşılaştırmalı çalışmada, kliniğimizde Pentacam Scheimpflug kamera kullanılarak kornea topografisi yapılan keratokonuslu 50 hasta (100 göz) ve 59 sağlıklı bireyin (118 göz) klinik verileri araştırıldı. Çalışmaya dahil edilen tüm katılımcıların demografik özellikleri, toplam aberasyonları, yüksek dereceli korneal aberasyonları, koma ve küresel aberasyonları kaydedilip analize edildi. Sonuçlar Keratokonus grubunda ortalama yaş 29.7 ± 10.3 yıl ve kontrol grubunda 32.1 ± 12.4 yıl idi. İki grupta yaş ve cinsiyet açısından uyumlu idi (sırasıyla P = 0.11; P = 0.76). Keratometrik sınıflandırmaya göre 63 gözde hafif, 23 gözde orta ve 14 gözde şiddetli keratoconus var idi. Düşük dereceli astigmat, yonca (trefoil), koma, tetra-folyo, yüksek dereceli astigmat, yüksek dereceli sferik aberasyon ve kök ortalama kare (root mean square) değerleri keratokonuslu gözler ile sağlıklı gözler arasındaki farklılıklar istatistiksel olarak anlamlı idi (P <0.05). Ayrıca keratometrik sınıflandırma grupları arasında kornea aberasyonlarında istatistiksel olarak anlamlı farklılıklar var idi. Sonuç Keratokonus evresi yüksek dereceli korneal aberasyon değişiklikleri ile ilişkilendirlmektedir. Bu ilişki özellikle refraktif cerrahinin evrelendirilmesi ve güvenliğinin iyileştirilmesinde yardımcı olabilir.

Keywords

• Korneal Sapmalar;
• Korneal Topografya;
• Düzensiz Korneal Astigmatizma
• Keratokonus;
• Pentacam Scheimpflug Kamera

References

1. 1. Sugar J, Macsai MS. What causes keratoconus? Cornea. 2012;31:716–719.
2. 2. Gatzioufas Z, Panos GD, Hamada S. Keratoconus: is it a Non-inflammatory Disease? Med Hypothesis Discov Innov Ophthalmol. 2017;6:1–2.
3. 3. Krachmer JH, Feder RS, Belin MW. Keratoconus and related non inflammatory corneal thinning disorders. Surv Ophthalmol. 1984;28:293-322.
4. 4. Rabinowitz YS. Keratoconus. Surv Ophthalmol. 1998;42:297-319.
5. 5. Applegate RA, Hilmantel G, Howland HC, Tu EY, Starck T, Zayac EJ. Corneal first surface optical aberrations and visual performance. J Refract Surg. 2000;16:507–514.
6. 6. Maeda N, Klyce SD, Smolek MK, Thompson HW. Automated keratoconus screening with corneal topography analysis. Invest Ophthalmol Vis Sci. 1994;35:2749–2757.
7. 7. Uçakhan ÖÖ, Cetinkor V, Özkan M, Kanpolat A. Evaluation of Scheimpflug imaging parameters in subclinical keratoconus, keratoconus, and normal eyes. J Cataract Refract Surg. 2011;37:1116–1124.
8. 8. de Sanctis U, Loiacono C, Richiardi L, Turco D, Mutani B, Grignolo FM. Sensitivity and specificity of posterior corneal elevation measured by Pentacam in discriminating keratoconus/subclinical keratoconus. Ophthalmology. 2008;115:1534–1539.

9. 9. Jafri B, Li X, Yang H, Rabinowitz YS. Higher order wavefront aberrations and topography in early and suspected keratoconus. J Refract Surg. 2007;23:774–781.
10. 10. Pantanelli S, MacRae S, Jeong TM, Yoon G. Characterizing the wave aberration in eyes with keratoconus or penetrating keratoplasty using a high-dynamic range wave-front sensor. Ophthalmology. 2007;114:2013–2021.
11. 11. Gobbe M, Guillon M. Corneal wavefront aberration measurements to detect keratoconus patients. Cont Lens Anterior Eye. 2005;28:57–66.
12. 12. Alio JL, Shabayek MH. Corneal higher order aberrations: a method to grade keratoconus. J Refract Surg. 2006;22:539–545.
13. 13. Lim L, Wei RH, Chan WK, Tan DT. Evaluation of higher order ocular aberrations in patients with keratoconus. J Refract Surg 2007; 23:825–828.
14. 14. Gordon-Shaag A, Millodot M, Ifrah R, Shneor E. Aberrations and topography in normal, keratoconus-suspect, and keratoconic eyes. Optom Vis Sci 2012; 89:411–418.
15. 15. Ambrósio R Jr, Caiado AL, Guerra FP, et al. Novel pachymetric parameters based on corneal tomography for diagnosing keratoconus. J Refract Surg 2011; 27:753–758.
16. 16. Thibos LN, Bradley A, Hong X. A statistical model of the aberration structure of normal, well-corrected eyes. Ophthalmic Physiol Opt 2002; 22:427–433.
17. 17. Maeda N, Fujikado T, Kuroda T, et al. Wavefront aberrations measured with Hartmann–Shack sensor in patients with keratoconus. Ophthalmology 2002; 109:1996–2003.
18. 18. Schlegel Z, Lteif Y, Bains HS, Gatinel D. Total, corneal, and internal ocular optical aberrations in patients with keratoconus. J Refract Surg 2009; 25:S951–S957.
19. 19. Reddy JC, Rapuano CJ, Cater JR, Suri K, Nagra PK, Hammersmith KM. Comparative evaluation of dual Scheimpflug imaging parameters in keratoconus, early keratoconus, and normal eyes. J Cataract Refract Surg 2014; 40:582–592.
20. 20. Hashemi H, Beiranvand A, Yekta A, Maleki A, Yazdani N, Khabazkhoob M. Pentacam top indices for diagnosing subclinical and definite keratoconus. J Curr Ophthalmol 2016; 28:21–26.
21. 21. Colak HN, Kantarci FA, Yildirim A, et al. Comparison of corneal topographic measurements and high order aberrations in keratoconus and normal eyes. Cont Lens Anterior Eye. 2016;39:380–384.
22. 22. Delgado S, Velazco J, Delgado Pelayo RM, Ruiz-Quintero N. Correlation of higher order aberrations in the anterior corneal surface and degree of keratoconus measured with a Scheimpflug camera. Arch Soc Esp Oftalmol. 2016;91:316–319.
23. 23. Nakagawa T, Maeda N, Kosaki R, et al. Higher-order aberrations due to the posterior corneal surface in patients with keratoconus. Invest Ophthalmol Vis Sci. 2009;50:2660–2665.
24. 24. Alió JL, Piñero DP, Alesón A, et al. Keratoconus-integrated characterization considering anterior corneal aberrations, internal astigmatism, and corneal biomechanics. J Cataract Refract Surg. 2011;37:552–568.
25. 25. Ramin S, SanginAbadi A, Doroodgar F, et al. Comparison of Visual, Refractive and Aberration Measurements of INTACS versus Toric ICL Lens Implantation; A Four-year Follow-up. Med Hypothesis Discov Innov Ophthalmol. 2018;7:32–39.