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Guilherme Ferrara, Jose F. Alfonso, Carlos lisa, Arancha Poo, Jesus Merayo-Lloves; Classification of Keratoconus According with Topographic Astigmatism, Coma and Type of Ectasia. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1081.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a surgical oriented classification of keratoconus for ICRS implantation.
Patients with keratoconus diagnosed according with Rabinowitz definition. Material: Patients were separated in groups according to the topographic axis (direct-90° axis, indirect-180° axis and oblique- 45° or 135°), coma aberration axis (0º to 105º from the astigmatism axis) and keratoconus type (central ectasia- 1 to 3 mm from the center of the visual axis, paracentral ectasia- 2 to 4 mm from the center of the visual axis, and pericentral ectasia - 3 to 5 mm from the center of the visual axis). Data were analyzed for descriptive statistical analysis.
Patients: 339 patients with keratoconus (179 right eye and 160 left eye), 53% men and 47% women with a mean age of 41 years old consecutively recruited in our institution from 2007 to 2009 were included in the study. 90% of the keratoconus were pericentral type, where 40% of the eyes presented inverse/oblique astigmatism and the coma aberration axis deviated in about 30° of the topographic axis of the astigmatism, and 50% of the eyes presented direct/oblique astigmatism, with the coma aberration axis varying in about 30° to 75° from the topographic axis of the astigmatism. The remaining 10% of the keratoconus eyes were paracentral and central types. The astigmatism on the paracentral type of keratoconus was direct and presented the coma aberration axis deviated in 75° to 105° from the topographic axis. On the keratoconus central type, the astigmatism could be direct, indirect or oblique and present the coma aberration axis coinciding in 30° with the topographic axis.
The knowledge obtained with this study that 90% of keratoconic eyes present a similar pattern, is possible to generalize the indications of the ICRS. In addition, this new classification should be useful to customize of ICRS according to surgeon and patient necessity.
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