Relationship Between Corneal and Refractive Astigmatism

Abstract

AllS'I'RAC'l' The aim of this study was to find arelationship between the corneal and refractive astigmtism , (RA) & (CA) and to show if it is possible to derive the subjective astigmatism (SA) from kcralomctric reading (KR). SO subjects(lOO eyes) were examined using Shin-nippon 9000 autorelkeratometer for RA and CA measurements , and subjective results were obtained . The difference in location of the axes of RA with CA and CA with SA was approximately same .There was no fixed relation in the axes . RA and SA axes exhibited small variation , §i5° difl”crcnce was the most (39.3%) , followed by £il0° (22.7%). l The dioptric difference of i0.75D and less between RA and CA was (95.8%) (95.7%) between CA and SA and (95.7%) between RA and SA. 20.1% for RA with CA , 25.6% for CA with SA and 18.3% for RA with SA were the difference of si0.50D. CA was agreed RA in l8.2%,with SA in 19.2% while RA and SA agreed in 32.6% . Generally , amathematical formula for the relation of RA with CA could not be drown . \ Key words : refractive , corneal, subjective,astigmatism . ll