# Comparison of Amsler-Krumeich and Sandali Classifications for Staging Eyes with Keratoconus
## 3 Results  
Overall, 252 eyes of 137 consecutive patients with KC (86 males, 51 females; 41.45 \(\pm\) 16.93 years) were included. According to the Amsler-Krumeich classification, the studied eyes were divided as follows: stage I (n = 3 eyes, 1.2%); stage II (n = 144 eyes, 57.1%), stage III (n 69 eyes, 27.4%), and stage IV (n = 36 eyes, 14.3%). According to the Sandali classification, the studied eyes are divided as follows: stage 1 (n = 206 eyes, 81.7%), stage 2 (n = 16 eyes, 6.4%) which was subdivided into stage 2A (n = 9 eyes, 3.6%) and stage 2B (n = 7, 2.8%), stage 3 (n = 2 eyes, 0.8%) of which one in stage 3A (0.4%) and one in stage 3B (0.4%), stage 4 (n = 25 eyes, 9.9%), and stage 5 (n = 3 eyes 1.2%) of which one eye in stage 5A (0.4%) and another eye in stage 5B (0.4%). Tables 2 and 3 report the clinical parameters of each stage of the Amsler-Krumeich and Sandali classifications, respectively. In 156 eyes (61.9% of total), the Amsler and Sandali staging systems differed in one stage, in 75 cases (29.8%) they differed in two or more stages. In 222 eyes (88.1%), the Sandali staging was higher compared to the Amsler one; in 21 eyes (8.3%), the two staging systems provided the same value, while only in nine cases (3.6%) the Amsler staging provided a higher grade compared with the Sandali system. Of 252 eyes, 101 eventually underwent keratoplasty for visual rehabilitation during the study period. The mean time from diagnosis to keratoplasty was 16.74 \(\pm\) 16.7 months (1-69 months). Of these, 96 eyes underwent deep anterior lamellar keratoplasty (DALK), while 5 underwent mushroom-shaped penetrating keratoplasty (PK). According to the Amsler-Krumeich classification, the eyes undergoing keratoplasty were scored as follows: stage I (n = 0), stage II (n = 29 eyes, 28.7% of the overall surgical cases), stage III (n = 44 eyes, 43.6%), stage IV (n = 28 eyes, 27.7%), while according to the Sandali classification, they were scored as follows: stage 1 (n = 64 eyes, 63.5% of the overall surgical cases); stage 2 (n = 11 eyes, 10.9%); stage 3 (n = 2 eyes, 1.9%), stage 4 (n = 22 eyes, 21  
In the present study, we pointed out the different staging of KC obtained according to the two classifications, showing the lack of agreement between the curvature alterations observed with the corneal topography and structural changes detected by means of AS-OCT. The Amsler-Krumeich classification is useful in the detection of keratoconus and monitoring of its progression. This is particularly important in screening candidates for refractive corneal surgery or lens-based procedures using premium IOLs such as multifocal IOLs. Since only the anterior corneal curvature is considered in the Amsler-Krumeich classification, several other classification systems have been proposed. Using a Scheimpflug system, the ABCD grading system by [PERSON] and associates incorporates the anterior and posterior corneal curvature, the thinnest pachymetry value, and the vision to characterize the tomographic and functional aspects of keratoconic corneas [11]. As tomography provides information regarding the subtle changes in the posterior corneal curvature, which precedes the anterior steepening, this tomography-based classification system has been proposed to allow early diagnosis of subclinical disease. It does not, however, characterize the histopathological structural changes that result in the topographic alterations associated with keratoconus. High-resolution OCT provides evaluation of each corneal layer and allows assessment of the corneal structural changes in keratoconus. The OCT-based classification proposed by [PERSON] et al. establishes a grading system based on the changes observed in progressive corneal ectasia. In advanced cases of keratoconus, wherein the repeatability of corneal topography is less reliable, the OCT allows continued monitoring of the structural alterations [10].