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Contact Lens III

Test 3

Bandage lenses are used to...? relieve pain; promote healing; hold medication and deliver it to the eye to reduce infection; protect the cornea; maintain ocular surface hydration; improve vision
What type of lenses are usually used for bandage lenses, plano or Rx? plano - although Rx lenses can be used depending on the condition
What lens materials are used in bandage lenses? hydrogel; silicone hydrogel, GP sclera (haptic) lenses, and collagen
What type of lens is being used more now for bandage lenses? Silicone Hydrogel, because they are more oxygen permeable
Are bandage lenses made from silicone hydrogel usually DW or CW? CW
What soft CLs are available in silicone hydrogel? Acuvue Oasys; Alcon-Air Optix Night and Day Aqua; B&L Purevision --- also HEMA lens - United States Contact lenses UCL 55
How do collagen shield-lenses dissolve in the eye? They become gel-like and eventually liquify.
What is collagen? A naturally occurring protein.
What is collagen extracted from? Porcine sclera
What is the name of the collagen lens made by B&L? BioCora collagen shield - available in different shapes and thicknesses. Dissolves in 6, 12, 24, 48, and 72 hours, and even one week.
What are scleral GP bandage lenses used for? severe ocular disease, irregular cornea, corneal thinning, scarring, keratitis, and irregularities due to ocular surgery.
How does a scleral GP bandage lens work? Vaults the cornea and traps fluid (unpreserved saline) behind the lens correcting the irregular astigmatism and distortion and keeps the eye wet. The liquid acts as a bandage
Fitting procedures for TCL's? Must center well, adequate movement for the condition, patient must be comfortable, and vision should not be worse than without the lens.
What is recurrent corneal erosion? Failure of the epithelial cells to adhere to bowmans layer. the epithelial cells will regenerate in 7 days if intact to bowmans, but if dislodged could take months to heal. caused by injury, chemical burns, surgery, infections, etc.
A lens fit for recurrent corneal erosion should have ______ movement. minimal
What is bullous keratopathy? The endothelium breaks down and caused edema that causes bullae (blister like lesions). The bullae proceed to the epithelial layer and causes painful breaks
A lens fit for bullous keratopathy should have what type of movement? minimal
What are the two types of corneal ulcers? Infectious and non infectious
What causes infectious corneal ulcers? bacteria, viruses, parasites
What causes non infectious corneal ulcers? abrasion, injury, chemical burns, thermal burns
What kind of movement should a contact lens for corneal ulcers have? Depends on the severity of the injury
How does a TCLs help with a corneal laceration or perforation? Tissue adhesive glue or sutures are used and the bandage lens serves as a splint to avoid wound leaking.
In trichiasis and entropian conditions, a TCLs is used for...? comfort
What is important when fitting TCLs? oxygen transmission; hydrogel lenses - higher water content and thinner; silicone hydrogel and GP - higher DK
A presbyopic eye has.... reduction and eventual loss of accomodation; reduction of lid tonicity; reduction of tear volume and quality; reduction of corneal sensitivity; reduction in pupil size
What should we evaluate mature CL candidates? physical characteristics; acuity; occupation/hobbies; motivation
What is important for our patients to understand about presbyopic CLs? It will not give them their youthful vision back; may need glasses for fine print or driving; they may need lots of follow ups; must be able to accept compromise
What are some methods of fitting presbyopic patients with CLs? Reading glasses over distance CL's; Distance glasses over near CL's; Monovision; Modified monovision; Multifocal
What type of multifocal CLs are available? Segmented bifocals, annular or concentric, aspheric=progressive type, diffractive
When checking monovision always check it with....? Both eyes, OU
For hyperopic patients in monovision, ________ the distance a little to balance both eyes. over-plus
For myopic patients in monovision, _________ both lenses to balance. under correct
Advantages of a monovision fit? easier to fit that bifocal CLs; more choices of material; replacement; spherical or toric; wider field of view; less expensive; more comfortable
Disadvantages of a monovision fit? Headaches; depth perception may be off; adaption period required; doesn't work well with high adds; may require reading or distance glasses over the top
Can pilots have monovision? NO!
What is modified monoviison? 1 sv lens for distance or near and 1 bifocal or multifocal cls
What is modified bivision? 2 different types of bifocals
Good candidates for multifocal cls include high motivated people, can afford them and return for follow ups; healthy eyes; no allergies or medications; Add powers between +1.00 to +1.75; hyperopes do better than myopes; low Rx's; astigmatism less than -2.00
Patients that are difficult to fit in MF CLs cranky; don't have time to return for follow ups; unhealthy; flaccid lids, unsuccessful CL wear in the past; opposite of good candidates
What are the two basic bifocal contact lens designs? 1. Alternating Vision/translating bifocal; 2. Simultaneous Vision
What is alternating vision bifocals? lens translates from distance vision to near vision; has 2 zones one for DV and one for near. view distance through the top portion, when you look down lens shifts upward to read through near segment
What is simultaneous vision bifocals? both distance and near are superimposed and the brain selects the image that is in focus;
In alternating vision the lens is _____ lid dependent and the _____ lid induces the translation. lower; upper
What is used to stabalize an alternating vision bifocal lens? Prism ballast or truncation
Does alternating vision BF CLs allow for sharp DV and NV? Yes
Are alternating lens available in soft, GP, or both? GP mostly, sometimes one will be available in soft, and then discontinued.
Segmented bifocals have _______ like spectacle lenses. 2 zones one for ____ vision and one for _______ vision. segments; near; distance
How do segmented lenses work? Segmented reading portion moves up when the patient looks down to read.
What makes segmented lenses more difficult to fit? Proper seg height; adequate transition from DV to NV; stable lens with minimal rotation
Fitting GP Alternating Design.... Examine lid position; Record K's - use MF guide for BC (fit flatter than K); Evaluate fit; Observe segment placement; Over-refract; Record BC, Power (DV/NV), Dia, Seg height, prism ballast 1.25 to 2.5 or truncation .3 to .6 mm
When examining the lid position if the lower lid is at or slightly above the limbus? use alternating design
When examining the lid position, if the lower lid is below the limbus? use simultaneous
If a GP alternating lens doesn't translate (move up when reading) refit with a.... flatter or steeper lens
Where should the seg be on a GP alternating design lens? top of seg should be at lower pupil margin in normal room lighting. Good starting point is to order a lens with seg 1 mm below the geometric center
What do we check when verifying a GP Alternating Design lens? BC; Power DV and add; Measure Seg Height from bottom of lens to the top of the seg using measuring magnifier; measure diameter - if truncated two diameters
When fitting a simultaneous lens it should be fit with _______ movement and good centration. minimal
Is prism ballast and truncation needed for simultaneous lenses? No, rotation is not an issue.
Ashperic lenses, also called progressive addition lenses or multifocal lenses, how do they work? The power of the lens increase in plus toward the periphery
Are aspheric lenses available in GP and soft? Yes
Aspheric lenses are defined by __________ values? eccentricity values (e values)
What is an e value? measurement of how far from a circle the shape varies
A spherical lens has an e value of? zero
What is the range of aspheric e values? .1 to 1.0 mm (cornea e value 0.4 to 0.6mm)
The lower the e value the _______ the fit. tighter
The higher the e value the _______ the fit. looser
What are diffractive bifocal CLs? looks like a Fresnel press on prism - the rings are smaller than a lathe mark; simultaneous; prism like facets that diffract light instead of refract
When are GP diffractive lenses used? When patients want sharper vision
When are soft diffractive lenses used? Pt's that desire comfort.
What determines the diopter power of a diffractive lens? The separation of the rings and the depth of the facets
Is truncation or prism ballast required for diffractive bifocal CLs No, rotation stabilization not required
What are concentric (annular) bifocal CLs? Mostly simultaneous, but the lens with near center and distance in the periphery can be fit alternating. This lens can also have distance center and near periphery.
Fitting Simultaneous lenses
Created by: griffiskr