visual optics

2. Eye as a camera
Components
Schematic eye and reduced eyes
Axes and visual angles

3. : shutter
: focusing system
: focusing
system
: diaphragm

4. THE CORNEA
THE ANTERIOR CHAMBER
THE PUPIL
THE CRYSTALLINE LENS
THE RETINA

6. • Vertical

8. • 2-4mmAverage size:
• Depth of focus increases
• Concept used as pin hole test in refractionSmall pupil:
• Retinal image quality improves
• Size of blur circle increasesLarge pupil:

9. • Thickness : Birth 3.5 to4mm
-Adult life 4.75 to 5mm
• Radius of curvature : Anterior surface 10mm
-Posterior surface 6mm
• Refractive index of lens : Nucleus 1.41
-Pole 1.385
-Equator 1.375
• Accommodation Power : At birth 14-16D
At 25yrs 7-8D
At 50yrs 1-2D
• Total Power : 15-18D

10.  Lens accounts for about one third of the power of the eye.
 ACCOMODATION : Provides a mechanism of focusing at different distance.
 OPTICAL CHANGES IN CATARACTOUS LENS
• Visual acuity reduction
• Myopic shift
• Monocular diplopia
• Glare
• Color shift

11.  Maximum resolving power at fovea.
 A Concave spherical surface with radius of curvature -12mm.
oThe images formed by optical system tends to have curved
surface ,the curvature of the retina is of the right order from
this point of view.
oA much wider field of view is covered by the steeply curved
retina.
 Advantages of curved surfaces of retina :

13. SCHEMATIC EYE
• Schematic eye is an mathematical or physical model that
represents the basic optical features of the real eye.
• Used to provide a basis for theoretical studies of the eye as an
optical instrumental

14. Cardinal points of schematic eye
• 2 Principal foci F1 and F2
• 2 Principle points P1 and P2
• 2 Nodal Points N1 and N2
Total Diopteric Power =58.64D

16. REDUCED EYE
 Is the simplified version By Listing and Donder
 Principal Point P
 Nodal Point N
 Anterior Focal Point F1
 Posterior Focal Point F2
 Anterior Focal Length f1 and Posterior focal length f2
Total Diopteric Power=60D
(+43 D by Cornea and +17 D by Lens)

18. AXES OF THE EYE
-Lines passing through centre of cornea (P),centre of Lens (N),and meets
the retina on the nasal side of the Fovea(R)
-Line joining the Fixation Point(O),Nodal Point (N),and Fovea (F)
-Lines Joining the Fixation Point (O) and the centre of rotation (C)

20. VISUAL ANGLES
o Angle formed between optic axis and visual axis at the nodal
point
o Angle formed optics axis and fixation axis at the centre of
rotation of the Eyeball.
o Angle formed between visual axis and the pupillary line.