introduction to refractive error 3.1

Question 1

what is refractive error ?

Answer 1

. Inability of the eye to produce a sharp image on the retina.
. includes spherical ametropia (hypermetropia and myopia) and astigmatism.
. measured in Dioptres at the spectacle plane (spectacle refraction ) or at the eye ( ocular refraction )

Question 2

what is ametropia ?

Answer 2

Any departure from emmetropia

Question 3

what is emmetropia ?

Answer 3

A sharp image is formed on the retina and vision cannot/won’t be improved with corrective lenses

Question 4

how is refractive error corrected ?

Answer 4

corrected by optical means-spectacle lenses , contact lenses or refractive surgery

Question 5

how significant is refractive error in terms of world visual impairment ?

Answer 5

. accounts for 42 % of world visual impairment
. 285 million people
. 85 % live in low income countries
. easily corrected

Question 6

what happens to vision when refractive error increases ?

Answer 6

vision gets worse

Question 7

what is Spectacle Refraction ?

Answer 7

Refractive error measured in the spectacle plane. It is given the symbol Fsp

Question 8

what is ocular refraction ?

Answer 8

Refractive error measured at the eye. It is given the symbol K for the reduced eye.

Question 9

What can refractive error have an Impact on?

Answer 9

our visual acuity- ability to distinguish between 2 points close to one another.