AIM: To study the keratoconus(KCN)and subclinical KCN in patients with astigmatism ≥2D by Pentacam anterior segment analyzer.

METHODS: Two hundred and one eyes in 107 patients with astigmatism ≥2D were included in this study. All patients underwent optometry, visual acuity, corrected visual acuity, slit lamp biomicroscopy, fundus examination, traditional corneal topography and examination with Pentacam. Changes of several parameters were observed including K1(horizontal central curvature within the scope with diameter of 3mm), K2(vertical central curvature within the scope with diameter of 3mm); Kmax(the maximum anterior corneal refractive power), corneal astigmatism(CYL), MinPachy(the thickness at the thinnest area of cornea), index of surface variation(ISV), index of vertical asymmetry(IVA), keratoconus index(KI), height of anterior corneal surface(AE)and height of posterior corneal surface(PE), etc. ROC curve was made. Cutoff value and the sensitive index of each group were compared. Mann-Whitney U test was used for analysis of several parameters obtained from Pentacam. ROC curve was analyzed to determine the best diagnosis cutoff value.

RESULTS: Mean age of the study population was 25.7±6.6 years old. Kmax, IVA, KI, AE and PE of the clinical and subclinical group were significantly higher than those of the astigmatism group, while the thickness at the thinnest area of cornea in clinical and subclinical group was lower than that of the astigmatism group(P<0.05). Sensitive index of Pentacam to diagnose keratoconus at clinical stage \〖the area under the curve(AUC)≥0.9\〗 were AE, PE, IVA, ISV, KI, Kmax, respectively. Sensitive index for the diagnosis of subclinical keratoconus \〖the area under the curve(AUC)≥0.9\〗 was PE.

CONCLUSION: The current study shows that subjects with 2D or more of astigmatism, even some of them have normal vision, should undergo corneal topography screening. Pentacam may provide more accurate information about anterior and posterior corneal anatomy especially for the height of posterior corneal surface, which plays an important role in screening of subclinical KCN.