ABBEROMETRY.pptx

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)1 ST ORDER: Tilt (Prism) b) 2 nd Order: Defocus Astigmatism c): 3 rd Order: Coma,Trefoil d)4 th Order: Sperical aberration,Tetrafoil e)5 th Order: Pentafoil d)6 th 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 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 ))

8. 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

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

10. 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

11. Management Treat the cause Tinted Glass Filters Sunglass

12. THANK YOU!