Keratoconic Cone using its Keratometry, Decentration, and Thickness as Staging Parameters
Kyaw L Tu, Abdo K Tourkmani, Singaram Srinivas
Citation Information :
Tu KL, Tourkmani AK, Srinivas S. Keratoconic Cone using its Keratometry, Decentration, and Thickness as Staging Parameters. Int J Kerat Ect Cor Dis 2016; 5 (3):99-104.
To propose a new system of keratoconus staging using a set of parameters describing the keratoconic cone.
Materials and methods
Retrospective case series study of 101 keratoconic eyes of 58 patients was undertaken. They all had complete eye examination including corneal topography (Oculus Pentacam). Kmean, Kmax, higher order aberrations (HOAs) root mean square (HOARMS) value, pachymetry at thinnest point and steepest corneal meridian were obtained from Pentacam. Apex to thinnest pachymetry distance (D) was calculated using trigonometry. Pearson correlation coefficients between Kmax and HOARMS, between D on the one hand and the adjusted angle of steepest meridian, Kmean and Kmax respectively on the other, were calculated.
Results
There is a statistically significant positive correlation between Kmax and HOARMS (p < 0.00001). There is a negative correlation, a “horizontalization,” of the steep meridian with D increase, although it fell short of statistical significance (p = 0.07). D and Kmean (p = 0.003), and D and Kmax (p = 0.005) are significantly negatively correlated.
Conclusion
Kmax correlates with significant changes in HOAs. D correlates with corneal astigmatic meridian change and has a divergent path to Kmean and to Kmax. We propose a new keratometry, decentration, and thinnest pachymetry staging using the parameters Kmax (K), distance from the corneal apex to the thinnest pachymetry point (D), and corneal thickness at its thinnest point (T) to give a better, detailed description of a keratoconic cornea which could lead to improvements in assessment of its severity and treatment outcomes.
How to cite this article
Tu KL, Tourkmani AK, Srinivas S. Keratoconic Cone using its Keratometry, Decentration and Thickness as Staging Parameters. Int J Kerat Ect Cor Dis 2016;5(3):99-104.
Keratoconus: update and new advances. Surv Ophthalmol 1998 Jan-Feb;42(4):297-319.
Keratoconus and related noninflammatory corneal thinning disorders. Surv Ophthalmol 1984 Jan-Feb;28(4):293-322.
Videokerato- graphy of the fellow eye in unilateral keratoconus. Ophthal- mology 1993 Feb;100(2):181-186.
Clinical detection of uni- lateral keratoconus. Aust N Z J Ophthalmol 1995 May;23(2):129-133.
Videokeratographic indices to aid in screening for keratoconus. J Refract Surg 1995 Sep-Oct;11(5):371-379.
KISA% index: a quantitative vid- eokeratography algorithm embodying minimal topographic criteria for diagnosing keratoconus. J Cataract Refract Surg 1999 Oct;25(10):1327-1335.
Group of Panelists for the Global Delphi Panel of Keratoconus and Ectatic Diseases. Global consensus on keratoconus and ectatic diseases. Cornea 2015 Apr;34(4):359-369.
Live-epikeratophakia for keratoconus. J Cataract Refract Surg 1998 Apr;24(4):456-463.
Corneal higher order aberra- tions: a method to grade keratoconus. J Refract Surg 2006 Jun;22(6):539-545.
A new tomographic method of staging/classifying keratoconus: the ABCD grading system. Int J Kerat Ect Cor Dis 2015;4(3):85-93.
Automated keratoconus screening with corneal topography analysis. Invest Ophthalmol Vis Sci 1994 May;35(6):2749-2757.
Evaluation of total and corneal wavefront high order aberrations for the detection of forme fruste keratoconus. Invest Ophthalmol Vis Sci 2012 May 17;53(6):2978-2992.
Progression of keratoconus by longitudinal assessment with corneal topography. Invest Ophthalmol Vis Sci 2012 Feb 23;53(2):927-935.
Progression of keratoconus assessed by Fourier analysis of videokerato- graphy data. Ophthalmology 2002 Feb;109(2):339-342.
Tangential vs sagittal videokeratographs in the “early” detection of keratoconus. Am J Ophthalmol 1996 Dec;122(6):887-889.
New clinical pathways for keratoconus. Eye 2013 Mar;27(3):329-339.
Corneal cross-linking for treatment of progressive keratoconus in various age groups. J Refract Surg 2014 Jul;30(7);454-460.
Is keratoconus a true ectasia? Arch Ophthalmol 2000 Sep;118(9):1179-1186.
Orbscan 11 anterior elevation changes following corneal collagen cross-linking treatment for keratoconus. J Refract Surg 2009 Aug;25(8):715-722.
Corneal thickness spatial profile and corneal volume distribution: tomographic indices to detect keratoconus. J Refract Surg 2006 Nov;32(11):1851-1859.
Collagen crosslinking with riboflavin and ultraviolet-A light in keratoconus: long-term results. J Cataract Refract Surg 2008 May;34(5):796-801.
CLMI: the cone location and magnitude index (CLMI). Cornea 2008 May;27(4):480-487.
Expanding the cone location and magnitude index to include corneal thickness and posterior surface information for the detection of keratoconus. Am J Ophthalmol 2013 Dec;156(6):1102-1111.
Evaluation of visual acuity pachymetry and anterior-surface irregularity in keratoconus and crosslinking intervention follow-up in 737 cases. J Kerat Ect Cor Dis 2013;2(3):95-103.
Changes in anterior and posterior corneal cur- vatures in keratoconus. Ophthalmology 2000 Jul;107(7):1328-1332.
Sensitivity and specificity of posterior corneal elevation measured by Pentacam in discriminating keratoconus/subclinical keratoconus. Ophthalmology 2008 Sep;115(9):1534-1539.
Assessing progression of keratoconus: novel tomographic determinants. Eye Vis 2016 Mar 11;3:6.
Location of steepest corneal area of cone in keratoconus stratified by age using Pentacam. J Refract Surg 2009 Nov;25(11):1012-1016.
Topography-guided vertical implantation of Intacs using a femtosecond laser for the treatment of keratoconus. J Cataract Refract Surg 2007 Jan;33(1):148-151.
Bilateral superior keratoconus: two case reports. Eye 2014 Oct;28(10):1254-1257.