Correlation between refractive errors, Keratometry and axial length

Refractive power of the eye is affected by many factors including the status of visual system'' components such as anteroposterior diameter، cornea، lens status، and certain drugs such as thiazides، or certain systemic diseases such as diabetes Mellitus and some eye diseases such as keratoconus. The purpose of this study was to investigate the correlation between refractive errors، corneal dioptric power and axial length (AL). Observational study was done on 100 medical students aged 21 to 31 years in outpatient ophthalmic clinic of Ghaem Hospital، Mashhad. Corneal dioptric power was measured by Javal - Schiotz keratometry device power in two main axes. Anterior–posterior eye diameter was evaluated by Ascan ultrasonography. All evaluation was done by one examiner. In this study AL was found to be the main factor of development of myopia less than six diopter. The detailed findings are summarized as follows: 1. Corneal dioptric power in myopia less than (2D) was 42. 99  1. 18 D; in myopia (2-4D) = 44/05  1. 62D; in myopia more than (4D) = 43. 5  0. 89 D. There was no statistically significant difference between these types of myopia (P=0. 143). 2. AL in myopia less than (2D) was 23. 85  1. 23 mm; in myopia (2-4D) = 24. 06  1. 03mm; in myopia more than (4D) = 25. 39  0. 62 mm. There was statistically a difference between these types of myopias (P<0. 00006). There is statistically a significant relation between Axial Length (AL) and myopia less than 6D. There is no statistically significant relation between corneal dioptric power and myopia.