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Presbyopia

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• The bichrome method is based on the same principle, and is done in an analogous way, as that explained for refining the sphere in the chapter on the subjective exam from distances.
Important:
The refraction of DV must be correct
Keep the bichromatic test of NV at the patient’s habitual reading distance. Good lighting.
It can be done monocularly or binocularly.
Given that the person is presbyope, he/she is always expected to indicate better vision on the green background. After that, positive lenses are added until achieving clear and similar vision on both backgrounds.
Test lastly, as has been indicated before, functioning, clear vision.
• The cross-cylinder method from near consists in putting a cross-cylinder in front of the eyes that provokes formation of Sturn’s conoid. After that, the necessary positive lenses are put in front as well in order to situate the circle of least confusion on the retina.
Important:
The refraction of DV must be correct
Situate the grid test at 5 arms at the person’s habitual work distance. The illumination during the test must be dim (around 20 lux).
It can be done monocularly or binocularly.
Put the cross-cylinder with the negative axis at 90º in front of the person. Given that the person is appropriately compensated for DV, this will provoke Sturn’s conoid with less focal distance for the image of the horizontal lines.
Since this person is presbyope this image will form behind the retina.
The objective is to put the necessary positive lenses in front of the person in order to supplant the conoid and situate the circle of least confusion on the retina. In this moment, the subject will indicate that he/she sees the vertical and horizontal lines equally clearly.
Test lastly, just as mentioned before, functioning clarity of vision.
• Presbyopia

1. 1. Gauri S. Shrestha, M.Optom, FIACLE Co-Ordinator B.Optom Program Institute of Medicine Dipak Sah, B.optom final Year
2. 2.  Accommodation  Age normal amplitude of accommodation  Range of Accommodation  Near vision
3. 3. Gradual decrease in amplitude of accommodation as expected with age The onset is usually anticipated by age 40 years or amplitude of accommodation tends to drop below 5.00D. Old aged eye (आँखा बुढो भयो)
4. 4. Age Functional effect Hyperopia Additional accommodative demand Occupation Near vision demands Gender Earlier onset in females (short stature, menopause) Systemic disease Diabetes mellitus, multiple sclerosis, cardiovascular accident Drugs alcohol, chlorpromazine, hydrochlorothiazide, antianxiety agents, antidepressants Geographic factors Proximity to the equator (higher average annual temperatures, greater exposure to ultraviolet radiation) Iatrogenic factors laser photocoagulation; intraocular surgery
5. 5.  Incipient presbyopia  Premature presbyopia  Manifest presbyopia  Absolute presbyopia
6. 6. Incipient presbyopia ◦Beginning stage of presbyopia when symptoms or difficulty are first encountered in near vision. ◦Patient will have more difficulty in dim illumination while can do well in bright illumination.
7. 7.  Premature presbyopia ◦Presbyopia occuring at an earlier age than expected for normal population. ◦Usually associated with ocular diseases, nutritional deficiencies or ingestion of certain drugs.
8. 8.  Manifest presbyopia ◦ Presbyopia with some amplitude of accommodation present.  Absolute presbyopia ◦ Presbyopia with amplitude of accommodation completely absent.
9. 9. “My arms are not long enough to see up close anymore”
10. 10.  Blurring of near vision  Drowsiness after a short period of near work.  Headache
11. 11.  Biomechanical  Biochemical  Physiological
12. 12.  Decrease in elasticity of lens material (44%)  Decreased elasticity of capsule  Increase in size of lens  Anterior shifting of the equatorial fibers
13. 13.  Increased disulphide bondings between the lens material and the capsule.
14. 14.  Increase in size  Alteration of the lens material (Not any sclerosis)
15. 15. HYPEROPES EMMETROPES MYOPES
16. 16.  Half in reserve for distance greater than 40 cm  One third in reserve for working distance less than 40 cm
17. 17.  Addition based on amplitude of accommodation.  Tentative addition based on age.  Plus build-up method.  Bichrome method.  Cross-cylinder method.  Relative accommodation method.  Dynamic Retinoscopy method.
18. 18.  Amplitude of accommodation decreases with age.. ◦ Presbyopia is reported when NPA exceeds 8 inches (22cm) ie AA = 4.50D (Donders)  Presbyopia exists when amplitude of accommodation is less than 5D (Morgan).
19. 19. Working distance (WD)= 40cm RAF (Amp accommodation) = 2.00D What should be the near addition ??? Accommodation required for WD = 2.50 D Accommodation in Reserve = 1.00D Amount of accommodation left = 1.00D Amount of Near addition = (2.50 –1.00) = 1.50D
20. 20.  Example 2 Working distance (WD) = 25 cm RAF (Amp accommodation) = 1.50D What should be the near addition ??? Accommodation needed at WD = 4.00D Amplitude held in reserve = 0.50D Amplitude of accommodation left = 1.00D Amount of near addition = (4.00-1.00) = 3.00D
21. 21.  Amplitude of accommodation to age (Hofstetter) ◦ Maximum = 25.0 – 0.4 (age) ◦ Probable = 18.5 – 0.3 (age) ◦ Minimum = 15.0 – 0.25 (age) ◦ Amount of near add calculated by holding certain amount of accommodation in reserve Rule of 4s (४ को िनयम)= 4*4-age/4
22. 22. Age of Range (Years) Minimum Expected Amplitude (Diopter) Range of Near Add in Diopter for 40 cm. 40 to 44 5.00 to 4.00 +0.75 to +1.00 45 to 49 3.75 to 2.75 +1.00 to +1.50 50 to 54 2.50 to 1.50 +1.50 to +2.00 55 to 59 1.25 to 0.25 +2.00 to +2.25 60 and over 0 +2.25 to +2.50
23. 23.  Can be done binocularly or monocularly  Plus lenses are increased in steps of 0.25D to the amount necessary to read the desired letters at a customary working distance.  Monocular build-up usually lands in more amount of near addition.
24. 24.  Chromatic aberration  In presbyopic patients red & green are focused behind the retina with red farther away.  Green appears clear.  Plus lenses are added until both red & green appear equally clear Can be combined this technique with tentative add method/amplitude method etc
25. 25.  Bichromatic method: ◦ Patient with Rx for DV, ◦ Bichrome test at habitual distance in NV ◦ Ask patient which background letters are more clear  Green-add plus, Red-remove plus  until he/she sees letters equally clear in both
26. 26.  A near point grid is presented to the patient at their customary working distance.  Illumination on the target should be diffuse.  Plus lenses are added until patient sees the lines clearly
27. 27.  Crossed cylinder (±0.50D) with their minus axes vertical are placed before the patient’s eyes.  Patient is asked to report which sets of lines running across or up & down appear clearer, sharper, blacker
28. 28.  Cross cylinder creates artificial astigmatism with an interval of sturm of 1D  If patient accommodates exactly for the target, both sets of lines should be equally clear.  If patient under-accommodates, the horizontal lines will appear clear.
29. 29.  Add positive lenses until verticle and horizontal lines are seen equally clearly ◦ Can be done monocularly or binocularly
30. 30.  Measure of lenses to blur letters of N6.  Patient is provided with plus lenses determined by bichrome method/add based on age/Amplitude method  Determine ◦ Minus lens to blur (PRA) ◦ Plus lens to blur (NRA)  Near add = NRA+PRA/2
31. 31.  The addition is 1.00 (say)  We add minus lenses until blur and the value be (1- 0.5)= +0.50 D  We add plus lenses and the value be +2.00 D= (1+1)  Then the final add is (+0.50+2.0)/2=  1.25D
32. 32.  Determine lag of accommodation (dynamic retinoscopy)  Reduce amount of lag by +0.50 to +0.75D  Prescribe remaining as addition for near
33. 33. Method Procedure Advantage 40 cm fused (binocular) cross- cylinder. Compare manifest refraction to plus value on 40 cm fused cross-cylinder, add is the plus over the manifest refraction. In older patient with limited accommodative amplitude and accommodative flexibility. One-half accommodative amplitude Accommodative amplitude determined from PRA, add based on allowing the patient to use only one-half of available amplitude at the desired reading distance. Good for early presbyopia with slightly reduced amplitude of accommodation account for the patient’s desired reading distance. PRA/NRA Plus add is the value that puts the total near power in the middle of the PRA/NRA blur points. Add is the middle of the Accommodative range from PRA to NRA
34. 34. Plus lens (Convex lens)
35. 35. Thank YOU
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