cataracts
Wavefront-guided or "custom" laser
"Imprints" patient's custom refraction Theoretically removes aberrations in cornea Higher chance of reaching refractive goal in low/moderate myopes -can be used for PRK/LASEK/LASIK
Cataract Treatment indications
- vision has decreased to 20/40 or worse -decreased vision is having negative effect on activities of daily living
INTRASTROMAL CORNEAL RINGS (INTACS)
-Circular rings of polymethylmethacrylate (PMMA) placed in mid peripheral stroma -Treats low myopia -Removable/exchangeable
PHAKIC INTRAOCULAR LENSES (IOLs)
-IOL inserted into eye with natural lens still in place -Allows for accommodation -Typically used in younger high myopes -Avoids ablation of cornea -Removable -Small risk of cataract and iritis
INTRAOCULAR SURGERY
-Improved technology and techniques allow for relatively safe "elective" intraocular surgery 1) Phakic IOL 2) Clear lens extraction 3) Accommodative IOL
RADIAL KERATOTOMY (RK)
-Multiple radial cuts into corneal stroma to correct mild to moderate myopia -No longer the most popular, safest, or most stable refractive procedure -Irregular astigmatism, Glare, Wound dehiscence
MONOVISION
-One eye (dominant) set for distance and one eye set for near or intermediate (as shown) -Can be used in a variety of refractive procedures
NATURAL LENS REPLACEMENT indications
-Replacing noncataractous crystalline lens with IOL for refractive purpose 1) Not a good photoablative candidate 2) Cornea too thin, too flat, too steep 3) High myopia/hyperopia
Excimer ("excited dimer") laser
-Used for PRK, LASEK, LASIK
lens changes overtime Ciliary body/lens changes
-Yellows: may affect color discrimination -Opacifies: cataract -Hardens: nuclear sclerosis -Loses accommodative ability: presbyopia
Causes of Cataract
-age (most common over the age of 65) -diabetes -family history -previous surgery or injury -nutritional deficiencies -oral prednisone
Presbyopia
-age-related loss of lens flexibility, causing reduced near vision -Loss of accommodation with age -Manifests in early 40s -Cannot be halted or mitigated with refractive surgery
misconceptions
-cataract is not a film over the eye -it is not a cancer -it is not caused by straining the eye -it is not spread from one eye to the other -it is not a cause of irreversible blindness
Cataract surgery process
-outpatient/awake/IV valium -pupil dilation drops 2hrs prior -local anesthetic(local injection or topical drops) -usually done through small sutureless incision (approximately 3mm) -usually removed with ultrasound instrument called phacoemulsification -intraocular implant lens placed in the eye to replace natural lens that was removed as the cataract -usually 90% recovered within 5-7 days -distance prescription typically reduced with intraocular lens
after cartaract tx cloudiness may occur months to years after surgery due to what
-posterior capsule clouds up 10-30% of the time after surgery -laser used to open a hole through the posterior capsule
Refractive Surgerys
-to primarily reduce distance prescription 1) Lasik 2) PRK 3) Phakic IOL 4) Clear lens extraction monovision or presbyopic IOL can correct near vision
PHOTOREFRACTIVE KERATECTOMY (PRK): PROCEDURE
1) Alcohol placed to loosen epithelium 2) Central epithelium debrided 3) Laser ablation 4) Epithelium grows back from periphery under bandage contact lens
LASER IN SITU KERATOMILEUSIS (LASIK): PROCEDURE
1) Suction ring stabilizes globe 2) Microkeratome creates thin stromal flap with a hinge 3) Flap reflected back 4) Laser ablation sculpts cornea 5) Stromal flap replaced
Signs and Symptoms of cataracts
1) painless gradual loss of vision in one or both eyes 2) reduced visual acuity on exam 3) reduced red reflex 4) discoloration of lens of eye ranging from green to brown to white
Risks of cataract surgery
1) vision loss-retinal detachment 2) loss of eye-corneal edema 3) infection-ptosis 4) hemorrhage-diplopia 5) glaucoma edema-cystoid macular
PRK: ADVANTAGES AND DISADVANTAGES
Advantages 1) No corneal flap complications 2) Long-term stability 3) Can perform on thin cornea Disadvantages 1) More patient discomfort 2) Inconvenience: usually done one eye at a time 3) Slightly higher risk of infection 4) Risk of haze (mitomycin C may minimize) 5) Glare/halos
NATURAL LENS REPLACEMENT: ADVANTAGES AND DISADVANTAGES
Advantages 1) Same procedure as cataract surgery - same provider can do 2) Avoids risks of flap creation and corneal ablation 3) Corrects high degree of myopia/hyperopia Disadvantages 1) Endophthalmitis 2) hemorrhage 3) retinal detachment 4) Patient expectations
LASIK: ADVANTAGES AND DISADVANTAGES
Advantages: 1) Little discomfort 2) Fast visual recovery 3) Long-term stability Disadvantages 1) Thin corneas not good candidates 2) Flap complications 3) Glare/halos 4) Diffuse lamellar keratitis (DLK)
Conventional laser
Laser program "imprints" standard refraction onto cornea -can be used for PRK/LASEK/LASIK
Astigmatism
Uneven curvature of cornea Causes separate areas of focus and consequent blurring
what can be corrected by new cartaract lens
astigmatism and presbyopia
Hyperopia
farsightedness Renders refractive surgery less predictable, requires longer to stabilize (PRK and Lasik)
Myopia
nearsightedness (not being able to see far) Severity is related to success of refractive surgery (PRK and Lasik)
phacoemulsification
ultrasound instrument used for cataract threatment