Refractive Errors
when parallel rays of light coming from infinity and are focused on sensitive layer of Retina when accommodation at rest is called as Emmetropia.
when parallel rays of light coming from infinity and are focused either in front or behind the Retina in one or both meridian when accommodation at rest is called as Refractive error.
Also called Ametropia
It include myopia, Hypermetropia, Astigmatism
Causes of Refractive Error
• Axial length
(Normal axial length is 24 mm more in myopia and less in hypermetropia)
• curvatural
(Normal Corneal Curvature - Anterior 7.8mm and posterior 6.5 mm)
• Refractive index (Diabetes) decrease in refractive index in old age
• position of crysteline lens
(Anterior - Myopia, Posterior - Hypermetropia)
Type of Refractive Errors
• Myopia
• Hypermetropia
• Astigmatism
Sign of Refractive Errors
• size of Eyeball (more in myopia and less in hypermetropia)
• corneal size and curvature (increase corneal curvature in myopia and flat in hypermetropia)
• Anterior chamber Depth (2.5mm)(deep anterior chamber in myopia and shallow in hypermetropia)
• Fundus Examination (Optic disc large In myopes and small in Hypermetropia)
Symptoms of Refractive error
• Diminution of vision
• Eye strain
• Headache
• Eye pain
• Itching and Burning sensation
Treatment of Refractive Error
• Spectacle
• contact lenses
• surgery