49 The Eye:

I. Optics of Vision

Dr. A.R. Jamshidi Fard2011

Visual SystemVisual SystemVisual SystemVisual System

Visual Visual

PathwayPathway

3 Tunics3 Tunics

Tunica FibrosaTunica Fibrosa: : cornea, scleracornea, scleraTunica VasculosaTunica Vasculosa: : choroid, ciliary body, irischoroid, ciliary body, irisTunica NervosaTunica Nervosa: : retinaretina

3 Chambers3 Chambers

Anterior Chamber Anterior Chamber Posterior ChamberPosterior ChamberVitreous BodyVitreous Body

EYEBALLEYEBALL

LightRefraction

Refraction of Light

Emmetropia بينايى طبيعى

Optics of the Eye

Ametropia بينايى انکسارى نقص

– Near sightedness (Myopia)

– Farsightedness (Hyperopia)

– Astigmatism

– Presbyopia

Refractive error

Presbyopia پيرچشمى

• Physiologic loss of accommodation in advancing age

• around 45 years of age , accommodation become less than 3 D

• -->reading is possible at 40-50 cm– difficult reading of fine print – Headache – Visual fatigue

Anisometropia

چشمها انکسارى ناهمسانى

• Difference in refractive power

between 2 eyes

Nearsighted or Farsighted

Errors of Refraction

)Normal Vision(

)Farsightedness(

)Nearsightedness(

Correction of Myopia and Hyperopia

by Use of Lenses

Astigmatism

Visual Acuity

Visual Acuity Test

Cataracts

• With age, lens becomes hard and opaque• Diabetes mellitus• Heavy smoking• Vision becomes

hazy and distorted,

will lead to blindness

• Surgical removal

or glasses

Glocoma

Ophthalmoscope