Glomerular Filtration rate and its determinants.pptx
Presbyopia
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PRESBYOPIA IS LOSS OF ACCOMODATION
INSIDE THE EYE
Loss of “auto-focus”
Difficult vision at near
Need to increase the distance between the
objects and the eye
Distant vision remains unchanged.
3.
Progressive Age-related loss of accommodation
Begins early in life
Early 40s: Functional vision affected
Complete loss of accommodation by 5th to 6th
decade
Most prevalent ocular affliction
◦ 100% of population
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Lenticular Changes
◦ lenticular sclerosis
◦ changes in capsular elasticity
◦ change in zonular insertion angle
Extralenticular Changes
◦ Neuromuscular changes
◦ Ciliary muscle changes
Glasser, A et al RSIG 1997
11.
Comfortable vision at near uses less than or
equal to half of the available amplitude of
accommodation
Near work becomes difficult when the
amplitude of accommodation is less than
5.00D
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Working distance at 40 cm requires 2.50D
of accommodation
◦ Patient A has 5.00D of accommodation
He can use up to 2.50D of accommodation comfortably
Therefore, he has just enough accommodative power for
reading at 40 cm, and no reading glasses are required
◦ Patient B has 3.00D of accommodation
He can use up to 1.50D of accommodation comfortably
Therefore, he needs an additional 1.00D of
accommodative power for reading at 40 cm, and +1.00D
reading glasses are required
14. ◦ Converging or plus lenses for near work
only in spectacles or contact lenses
Changes in prescriptions are required every
two to three years for presbyopia
◦ Surgery
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Contact lenses
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Single vision contact lenses with glasses
Monovision contact lenses
Bifocal and multifocal contact lenses
Modified monovision contact lenses
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Surgery
◦ Laser in-situ keratomileusis (LASIK)
More for presbyopic hyperopia than presbyopia
myopia at the moment
◦ Multifocal intraocular lens (IOL)
◦ Conductive keratoplasty (monovision)
◦ Scleral expansion
20. CORNEAL INLAYS:
a) Acufocus: ACI 7000 (Irvine, Cal)
b) Presbylens (Revision Optics, Cal)
c) FlexiVue microlens (Presbia Corp.
Amsterdam)
They are made of Biocompatible material
inserted inside the cornea and alter the way
light rays enter the eye (Like a Contact Lens)
21. Corneal Inlays
Waring recently discussed results of the Kamra
smallaperture corneal inlay to improve near vision in
emmetropic presbyopes. The inlay is 5-μm thick and
3.8 mm in total diameter, with a 1.6-mm central
aperture that increases depth of focus and improves
near visual acuity by restricting bent light rays from
entering the eye similar to the f-stop in a camera.
22. CORNEAL INLAYS:
Still not approved by FDA and therefore not
available in USA. All of them in Clinical FDA
trials.
Several advantages:
a) Extraocular surgery
b) Reversible
c) Exchangeable
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The Flexivue Microlens, a corneal inlay treatment
for presbyopia, is 3-mm in diameter and about
15 microns thick. The lens is placed about 280300 microns deep in the cornea of the patient's
non-dominant eye through a pocket created
using a femtosecond laser.[1] The specific
vision-correcting prescription for each patient is
incorporated in the outer area of the lens.[2] The
procedure lasts about 10 minutes, and after the
lens insertion, the pocket self-seals and holds
the lens in place.
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28. EXCIMER LASER SURGERY:
Monovision: one eye (dominant) for distance
and one eye (Non Dominant) for near
Only approved Corneal surgery in USA by the
FDA.
Difficult to tolerate by most of the patients.
Loss of Contrast and depth perception by the
patients (not suitable for high demanding visual
needs)
Limited useful time.
29. EXCIMER LASER SURGERY:
Multifocal Cornea: Excimer Laser reshapes the
cornea and alters the way light rays enter the
eye. (Like Contact Lenses)
Has been named as PRESBYLASIK.
Both eyes see near and distance.
Several softwares in use by some of the Lasers
Manufacturers.
Temporary solution for some years
Repeatable and/or reversible
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How Does this treatment work if the pupil gets
smaller when reading?
CREATION OF A PERIPHERAL KNEE
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It should be noted that,
although near vision is better, the quality of
distance vision
provided by these models is worse than that of a
presbyopic
emmetropic eye.6
35. CONDUCTIVE KERATOPLASTY:
A probe touches the cornea with High
Radiofrequency and by collagen shrinkage
reshapes the cornea.
Produces controlled monovision inducing
Myopia
Only suitable for Hyperopes
FDA approved as Monovision Blended Vision
Rapid loss of effect is the main problem
Its use has decreased in the last years.
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38. SCLERAL EXPANSION PROCEDURE:
Small incisions in the sclera close to the cornea
and insertion of a band to create an space for
the ciliary muscle to move.
Ciliary muscle is the “autofocus” muscle
Defensors claim improve accomodation
Not FDA approved. Not in use in USA.
Its use has declined dramatically due to not
consistent results.
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41. PHAKIC MULTIFOCAL INTRAOCULAR
LENSES:
Lenses inserted inside the eye over the iris
(Verizyse-Artisan) or under the iris (Visian ICL)
The natural Lens is not removed
FDA approved for correction of Myopia not for
Presbyopia
Still prototypes.
Main advantage is reversibility..
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43. MULTIFOCAL INTRAOCULAR LENSES
ACCOMODATIVE INTRAOCULAR LENSES
The natural lens is removed through surgery and
replaced by one of those lenses.
FDA approved to be used for cataract surgery
Off Label used as clear lens exchange (PRELEX)
Very popular method internationally
Not very commonly used in USA
Cristalens Accomodative is number one used in
USA
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47. MULTIFOCAL INTRAOCULAR LENSES
ACCOMODATIVE INTRAOCULAR LENSES
Both types still under development and research.
Very strong visual symptoms have produced
decrease of its use in “young” presbyopes.
Not reversible surgery
Decreased contrast sensitivity
They require a careful selection of candidates and
lots of counseling.
48.
Hao et al recently introduced data on injectable in situ
curable accommodating IOLs. Using functionalized polysiloxane
macromonomers, they were able to refill the
empty lens capsular bag via an injection. To prevent leakage
from the capsular bag, the investigators performed
in situ cross-linking of polysiloxane gel using blue light
(wavelength, 400-500 nm) at an intensity of 70 mW/cm2.
A 3-month in vivo biocompatibility study was performed
in rabbits. No iritis, uveitis, retinal detachment. or corneal
decompensation was observed.
