new orleans computer club · anatomy of the eye ... out, frequent changes to eyeglass prescription
TRANSCRIPT
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New Orleans Computer Club November 2th, 2011
Ginny Kullman, MD
Department of Ophthalmology
Ochsner Medical Center
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Background information:
field of ophthalmology
anatomy of the eye
how the eye works
Common causes of decreased vision
How to correct decreased vision
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Ophthalmologist – specialist in medical and surgical eye problems
subspecialties within ophthalmology:
Cornea & Refractive Surgery Glaucoma Oculoplastics Retina & Vitreoretinal disease (medical vs. surgical)
Neuro-ophthlamology Pediatrics Uveitis Oncology Pathology
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Anterior segment: refractive error, lens, cornea
Posterior segment: retina, macula
Systemic diseases: diabetes, hypertension
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Anterior segment: refractive error, lens, cornea
Posterior segment: retina, macula
Systemic diseases: diabetes, hypertension
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the shape of the eye does not bend light correctly, resulting in a blurred image
types of refractive error:
myopia – objects blurred at a distance
hyperopia - close objects are blurred
astigmatism – blurring of vision at all distances
presbyopia – difficulty reading up close
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Age-related process; begins to affect people beginning in mid-40s
90 million Americans have presbyopia or will develop it by 2014
cannot be prevented
can be tx’ed with bifocals, reading glasses
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Anterior segment: refractive error, LENS, cornea
Posterior segment: retina, macula
Systemic diseases: diabetes, hypertension
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• Clouding of the eye’s natural lens that prevents light from focusing on the retina
• Patients experience blurry vision, double vision, sensitivity to light, glare, colors that appear washed out, frequent changes to eyeglass prescription
• Can affect activities of daily
living if progressed
• Age is the biggest risk factor
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By age 65, > 90% of people have a cataract
>20 million adults in the US have cataracts
In the US, cataract surgery is the most frequent procedure performed on patients 65 and above
Nearly 3 million cataract procedures are performed in the United States every year Cataract is the most common cause of blindness in the world, although it is treatable.
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Cataracts are not a “film” over the eye
Cataracts do not travel from one eye to the other
Cataracts are not caused by using the eyes too much
Cataracts are not related to cancer
Cataracts cannot be prevented
Cataracts cannot be removed with a laser*
* True, up until recently…
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Surgical Techniques
Intraocular Devices
Surgical Equipment and Devices
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The eye is struck with a blunt object with sufficient force to cause the zonules to break, causing the lens to dislocate into the vitreous cavity
Vision is restored - but limited and unfocused
The technique was modified so that a sharp fine instrument was inserted into the eye to break the zonules to cause the dislocation
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1748: first reported surgical
removal of a cataract from
the eye occurred in Paris
surgery required a large incision, entire opaque lens removed in one piece
surgery limited to most advanced cataracts
patients were kept immobilized with sandbags around their head to allow for wound healing
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technique allowed removal of lens while leaving capsule behind
commonly performed in 1980’-90’s
cataract removed manually
required large incision, sutures
prolonged healing (6-8wks)
suture removal required
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Invented in 1967 by
Dr. Charles Kelman
ultrasonic power used to
break the lens into minute
fragments that can be aspirated
very small incision, no sutures required
quicker healing, vision restored within days
relatively no restriction in activity
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phacoemulsification –modern cataract surgery in which the lens is emulsified with an ultrasonic hand-piece and aspirated from the eye
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During WWII, Sir Harold Ridley observed that fighter pilots could tolerate shards of plastic from aircraft windshields in their eyes
Used this knowledge to create and implant the first intraocular lens in 1949.
1952: he supervised the first IOL implantation in the U.S.
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Originally, no lenses implanted after cataract sx
First implantable IOL made of PMMA 1949
Originally, IOLs correct for distance vision
New generations provide full range of vision and correct astigmatism
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Material: PMMA plastic acrylic, silicone
Foldable
Incision size
Monofocal vs. Premium IOLs
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MONOFOCAL
light enters eye, passes through lens with a single zone of clear focus, and is bent to one specific focal point on the retina
focal point usually set for distance, requiring reading glasses for near
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MONOFOCAL
light enters eye, passes through lens with a single zone of clear focus, and is bent to one specific focal point on the retina
focal point usually set for distance, requiring reading glasses for near
MULTIFOCAL
incorporates both distance and near powered lenses into one
lower powered zones bend light coming from a distance to a single focal point on the retina; while higher powered zones bend light from near objects to the same focal point
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principle of refractive laser surgery is to sculpt the cornea in such a way to allow light rays to focus on the retina without additional correction (ie. glasses, CL)
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PRK = Photorefractive keratectomy
LASIK = Laser Assisted In Situ Keratomilieusis
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A flap of cornea is not created, instead the corneal epithelium (top layer of the cornea) is removed and the laser is applied to the underlying corneal surface
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A superficial flap (~120 microns) is made; the flap is reflected, and the excimer laser treatment is applied to the underling stroma, flap is repositioned into place
faster visual recovery, less pain
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Microkeratome
hand held device that cuts
the cornea with a metal blade
Femtosecond Laser “bladeless surgery”
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LASER = Light Amplification by Stimulated Emission of Radiation
Refractive layers of the eye (cornea, lens) do not absorb radiation in the visible or near-infrared spectrum
At higher power densities, these structures will absorb light energy small bubbles of CO2 focal disruption of tissue
“photodisruption”
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Approved by the FDA in 2000 for LASIK
FS laser parameters:
1053 nm
10-15 second (femtosecond) pulse duration
Zone of collateral tissue damage ~ 5μm
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near-infrared laser energy (1053nm) is fired into tissue at a specific depth, excited particles create a precise pattern of tiny, overlapping cavitation bubbles, corresponding to each laser pulse
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laser can be focused to a 3um spot (accurate to 5um); causes virtually no trauma to surrounding tissue
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complete flap achieved by placing thousands of laser pulses next to each other; as the laser moves back and forth across the eye, the bubbles are connected
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“Will my cataract be removed by a laser?”
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FS laser recently approved for use of several steps of cataract surgery Anterior capsulotomy
Nuclear fragmentation
Advantages: Predictable
Customized
Safety
Disadvantages: Expense
Logistics
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