Ahmet ELBEYLİ, Sucattin KOCAMİS, Hasan ÇAKMAK, Emine DOĞAN

Keratokonus Olgularında Farklı Topografik Referans Yüzeylerin Karşılaştırılması

Amaç: Keratokonus tanısında kullanılan topografik referans haritalama yöntemlerinin duyarlılık ve özgünlüğünün karşılaştırılması Materyal ve metodlar: Keratokonuslu 23 hastanın 40 gözü ile rastgele seçilen refraktif cerrahi gönüllüsü 25 hastanın 40 gözü Scheimpflug (Sirius CSO-Italy) topografi cihazı ile analiz edildi. Farklı referans yüzeylerden elde edilen anterior elevasyon ve posterior elevasyon haritaları ile bu referans yüzeylerin keratokonusu saptamadaki duyarlılık ve özgünlüğü araştırıldı. Bulgular: ROC eğri analizlerine göre; asferik ve asfero-torik yüzeylerden elde edilen posterior elevasyon verilerinin her ikisinin de keratokonusu saptamadaki duyarlılığı (97.5%), sferik referans yüzeyden elde edilen verilere göre anlamlı olarak daha yüksekti. Ayrıca asferik referans yüzeyin keratokonus tanısında en yüksek özgünlüğe (90%) sahip olduğu sonucuna ulaşıldı. Sonuç: : Çalışmaya göre yüksek duyarlılık ve özgünlük değerleri asferik ve asferotorik referans yüzeylerden elde edildi. Posterior elevasyon değerleri ile anterior elevasyon değerleri kıyaslandığında posterior yüzeyin daha değerli olduğu görüldü. Bu yüzden asferik ve asferotorik referans yüzeyin keratokonusu saptamada posterior elevasyon ile birlikte daha doğru sonuçlar vereceği sonucuna ulaşıldı.

Anahtar Kelimeler:

keratokonus, kornea, korneal topografi, referans yüzey seçimi, scheimpflug kamera

Comparison of Different Topographic Reference Surfaces in Keratoconus Cases

OBJECTİVE: To compare the sensitivity and specificity of elevation maps obtained from different topographical reference surfaces used in the diagnosis of keratoconus. MATERİALS AND METHODS: In this study 40 eyes of 23 patients with keratoconus and 40 eyes of 25 refractive surgery candidates as a control group was measured with a Scheimpflug camera (Sirius CSO-Italy). Using the receiver operator characteristic curves (ROC), a comparison was made of the ability to differentiate keratoconus from a normal cornea with anterior elevation(AE) and posterior elevation(PE) measurements obtained from the spherical, aspherical, asphero-toric reference surfaces. RESULTS: The ROC curve analysis showed that posterior elevation measured from the aspherical and asphero-toric surfaces had a significantly higher area under the ROC curves (0.987, 0.973 respectively) thanthevalueobtainedfromthesphericalreferencesurfaces. According to the data obtained from the ROC curve analysis, the posterior elevation maps obtained from the aspherical and asphero-toric reference surfaces had the highest sensitivity (97.5% for both) and the posterior elevation map obtained from the aspherical reference surface had the highest specificity (90%). CONCLUSION: The highest sensitivity and specificity values were obtained from the aspherical and asphero-toric reference surfaces rather than from the spherical reference surface. When compared to the anterior elevation values, the posterior elevation values were found to be more sensitive and specific. Therefore, aspherical and asphero-toric reference surfaces and a posterior elevation map would seem to be more accurate in the differentiation of keratoconus and normal cornea.

Keywords:

scheimpflug camera, cornea, corneal topography, keratoconus, reference body selection,

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References 1. Swartz T, Marten L, Wang M. Measuring the cornea: the latest developments in corneal topography. CurrOpinOphthalmol. 2007;18:325–33.
2. Konstantopoulos A, Hossain P, Anderson DF. Recent advances in ophthalmic anterior segment imaging: a new era for ophthalmic diagnosis? Br J.Ophthalmol. 2007;9:1551–7
3. Tomidokoro A, Oshika T, Amano S, Higaki S, Maeda N, Miyata K. Changes in anterior and posterior corneal curvatures in keratoconus. Ophthalmology. 2000;107:1328–32.
4. Rao SN, Raviv T, Majmudar PA, Epstein RJ. Role of Orbscan II in screening keratoconus suspects before refractive corneal surgery. Ophthalmology.2002;109:1642-6.
5. Gomes JA, Tan D, Rapuano CJ, Belin MW, et al. Group of Panelists for the Global Delphi Panel of Keratoconus and Ectatic Diseases. Global consensus on keratoconus and ectatic diseases. Cornea. 2015;34:359-69.
6.Fam HB, Lim KL. Corneal elevation indices in normal and keratoconic eyes. J Cataract Refract Surg. 2006;32:1281–7.
7. de Sanctis U, Loiacono C, Richiardi L, Turco D, Mutani B, Grignolo FM. Sensitivity and specificity of posterior elevation measured by Pentacam in discriminating keratoconus/subclinical keratoconus. Ophthalmology 2008;115:1534–9.
8. Mihaltz K, Kovacs I, Takacs A, Nagy ZZ. Evaluation of keratometric, pachymetric, and elevation parameters from keratoconic corneas with Pentacam. Cornea. 2009;28:976–80.
9. Tanabe T, Oshika T, Tomidokoro A, et al. Standardized color-coded scales for anterior and posterior elevation maps of scanning slit corneal topography. Ophthalmology 2002; 109:1298–302.
10.Wang JC, Hufnagel TJ, Buxton DF. Bilateral keratectasia after unilateral laser in situ keratomileusis: a retrospective diagnosis of ectatic corneal disorder. J Cataract Refract Surg. 2003;29:2015-8.
11. Nilforoushan MR, Speaker M, Marmor M, et al. Comparative evaluation of refractive surgery candidates with Placido topography, Orbscan II, Pentacam, and wavefront analysis. J Cataract Refract Surg. 2008;34:623–31.
12. Rufer F, Schröder A, Arvani MK, Erb C. Central and peripheral corneal pachymetry standard evaluation with the Pentacam system. KlinMonatsblAugenheilkd. 2005;222:117–22.
13. Ho JD, Tsai CY, Tsai RJ, Kuo LL, Tsai IL, Liou SW. The validity of the keratometric index: evaluation by the Pentacam rotating Scheimpflug camera. J Cataract Refract Sur. 2008;34:137–45.
14. Ucakhan O, Cetinkor V, Ozkan M, Kanpolat A. Evaluation of Scheimpflug imaging parameters in subclinical keratoconus, keratoconus, and normal eyes. J Cataract Refract Surg. 2011;37:1116–24.
15. Jafarinasab MR, Feizi S, Karimian F, Hasanpour H. Evaluation of corneal elevation in eyes with subclinical keratoconus and keratoconus using Galilei double Scheimpflug analyzer. Eur J Ophthalmol. 2013;23:377-84.
16. Ishii R, Kamiya K, Igarashi A, Shimizu K, Utsumi Y, Kumanomido T. Correlation of corneal elevation with severity of keratoconus by means of anterior and posterior topographic analysis. Cornea. 2012;31:253-8.
17. Reinstein DZ, Archer TJ, Gobbe M. Corneal epithelial thickness profile in the diagnosis of keratoconus. J Refract Surg 2009;25:604–10.
18. Smadja D, Santhiago MR, Mello GR, Krueger RR, Colin J, Touboul D. Influence of the reference surface shape for discriminating between normal corneas, subclinical keratoconus, and keratoconus. J Refract Surg. 2013;29:274-81.
19. Kovács I, Miháltz K, Ecsedy M, Nemeth J, Nagy ZZ. The role of reference body selection in calculating posterior corneal elevation and prediction of keratoconus using rotating Scheimpﬂug camera. Acta Ophthalmol.2011; 89:251–6.
20. Sideroudi H, Labiris G, Giarmoukakis A, Bougatsou N, Kozobolis V. Contribution of reference bodies in diagnosis of keratoconus. Optom Vis Sci. 2014;91: 676-81.