Published on February 21, 2014
1. 2. 3. 4. 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.
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
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
Distance Intermediate Near
Lens makes the auto focus
Age (years) Distance (cm) 10 7 20 10 30 14 40 20 50 40
Age (years) Amplitude (D) Age (years) Amplitude (D) 10 14.00 45 3.50 15 12.00 50 2.50 20 10.00 55 1.75 25 8.50 60 1.00 30 7.00 65 0.50 35 5.50 70 0.25 40 5.00 75 0.00
Age Predicted near add 40 0 45 +1.00 48 +1.25 50 +1.50 52 +1.75 55 +2.00 60 +2.25 63 +2.50
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
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
ADD=Working distance – ½ amplitude
◦ 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
Spectacles ◦ Single vision reading glasses ◦ Multifocal lenses containing near Add Bifocal lenses Trifocal lenses Progressive addition lenses
Contact lenses ◦ ◦ ◦ ◦ Single vision contact lenses with glasses Monovision contact lenses Bifocal and multifocal contact lenses Modified monovision contact lenses
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
CORNEA SCLERA ANTERIOR CHAMBER LENS
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)
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.
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
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. The specific vision-correcting prescription for each patient is incorporated in the outer area of the lens. The procedure lasts about 10 minutes, and after the lens insertion, the pocket self-seals and holds the lens in place.
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.
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
How Does this treatment work if the pupil gets smaller when reading? CREATION OF A PERIPHERAL KNEE
PREOPERATIVE POSTOPERATIVE The knee
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
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.
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.
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..
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
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.
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.
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