Purpose: To detect the prevalence of clinical and subclinical Keratoconus (KC) among patients with myopic astigmatism ≥ -1.5 diopters (D) using Sirius Scheimpflug Analyzer. Methods: An observational cross-sectional study was carried out on 375 eyes of 188 patients with an astigmatic error of ≥ -1.5 diopters who came to ophthalmology outpatient clinic of Zagazig University Hospitals for glasses prescription in the period between July and December 2021. All subjects underwent a complete ophthalmic examination which included history taking, uncorrected visual acuity (UCVA) & best corrected visual acuity (BCVA), cycloplegic refraction using autorefractometer, slit lamp biomicroscopy, retinoscopy, direct ophthalmoscopy and dilated fundus examination. Patients with ≥ -1.5 D astigmatism by autorefractometer were scanned by the Sirius Scheimpflug Analyzer. According to clinical and topographic findings, patients were classified into 3 groups; KC, subclinical KC and astigmatism. Results: The study included 375 eyes of 188 patients who fulfilled the inclusion criteria: 95 males (50.5 %), 93 females (49.5 %). Mean age was 22.4 ± 5.84 (range from 12 to 29 years). Prevalence of KC was 10.9%, subclinical KC was 3.2% and normal astigmatism was 85.9%. Conclusion: This high prevalence of KC in the studied sample reflects the high prevalence of KC in the general population of Middle East countries compared with the western countries.