Optometry 2nd year syllabus for Optometry instruments

1. ABBEROMETRY

2. ABERROMETER
• ALL FORM OF DEVIATION OR REFRACTIVE ERRORS
ARE BASICALLY ABERRATION
TYPES:
a)LOWER ORDER ABBERATION:
Myopia,Hypermetropia,Regular Astigmatism
b)Higher Order Aberration
*Sperical
*Chromatic
*Coma

3. • HIGHER ORDER ABERRATION
a)1ST ORDER: Tilt (Prism)
b) 2nd Order: Defocus Astigmatism
c): 3rd Order: Coma,Trefoil
d)4th Order: Sperical aberration,Tetrafoil
e)5th Order: Pentafoil
d)6th Order: hexafoil
Heptafoil,Octafoil

4. • People with higher order Aberrations my not
see perfectly even with the glass or CL

5. Aberrometer
• It is the instruments used to measure
aberration
• Aberromertry has become clinically important,
Since the Progress in Imaging and Refractive
Surgery may allow the correction of certain
aberration

6. Wave front aberrometry
• Wavefront aberrometry
Wavefront aberrometry is more popular in
clinical practice.
It is for the measurement of aberration in the
Optical system of eye by Wave Front analysis by
evaluating how light that enters into the eye is
modified and image on to the retina

7. Principles
1) Hatmann-Shack Principle
A single laser bean is projected as a spot on the
retina and the reflected bundle of rays passes
through the optical system of the eye. It is then
picked up by an array of small lenslets,which focus
these rays into spot on an array of CCD camer. Then
the mossaic of spot is used to define the wavefront
and analyse its deformation.Each spot are analyzed
and a color coded picture of the wavefront is
generated by the aberrometer (Eg: LASAR Wave
(alcon),Wavescan (Visx))

10. • 2) Tscherning Principle
A Bundle of equidistant light rays shown on the
cornea which are imaged on the retina. A low
light CCD camera linked to a computer is used to
analyze the pattern of the spots observed on the
retina
Eg: Allegreto

12. Factors effecting total ocular
Wavefront
• Age
• Size of pupil
• Accomodation
• Chromatic Abberation
• Tearfilm
• Misalignment of the eye
• Refractive Error

13. Clinical Application
• Wave front guided refractive sx.
• Role in early Diagnosis of keratoconus.
• Wavefront guided LASIK Enhancement.
• Cataract/PCO Who have good VA in the
normal Light Condition

14. Management
• Treat the cause
• Tinted Glass
• Filters
• Sunglass

15. THANK YOU!