Chapter 14 Flashcards
What does a prescription for contact lenses include?
Power of the contact lens along with the diameter and base curve measurements. Measurements of the refractive error (refraction) and astigmatism (keratometry) are needed to make those qualifications.
What is the primary purpose of disinfecting contact lenses?
Preventing growth of bacteria, viruses, and fungi. Chemical disinfection: often hydrogen peroxide, and UV radiation: a germicidal UV-C light, can be used to kill microorganisms
An allergic reaction due to contact lens wear is most often due to what substance?
Preservative or disinfectant chemicals in a lens solution.
About 10-20% of all CL wearers have sensitivity reactions to at least one of the preservative or disinfectant chemicals used in contact lens solutions. Thimerosal is the most common allergy. Preservative free solutions can only be used for rinses as they are not disinfecting agents
What is a significant advantage of soft CL versus Rigid Gas-Permeable lenses?
Soft CL are easier to adapt to and initially more comfortable.
Rigid Gas-Permeable (RGP) are better at correcting irregular astigmatisms and can provide better vision potential due to their larger optical centers
What is a contraindication for being prescribed CL?
Working in an environment with exposure to fumes.
Pathological conditions, compliance, blink reflex, dryness, disability, and seizure can also be contraindications
What is the only acceptable rinsing solution for CL?
Sterile saline solution.
Homemade and preservative-free saline solutions are only effective at rinsing and can lead to microorganism exposure
Where should a tech first place the lens when inserting a soft CL on a patient?
On the sclera below the cornea or on the cornea directly.
When placed on the sclera, it is placed below the cornea and moved into place by the patient closing the eye and rolling it. If placing on the cornea, the patient will look down, and the tech will hold the CL concave up and place onto the cornea.
Cosmetic restorative lenses are most appropriate for what purpose?
Prosthetic for disfigured eyes.
CRL have a sclera, Iris, or pupil printed on them to mask trauma or infection.
What is the risk of a Corneal abrasion caused by FB lodged between the cornea and CL?
Corneal Infection.
Foreign material is more painful for rigid CL wearers due to the “bandage” effect of soft CL. Ulcers have been developed after simply patching for CL patients, so all abrasions are treated as potentially infected.
What signs and symptoms indicate an allergic reaction to CL solution?
Irritation, redness, fogging, and decreased tolerated wearing time.
10-20% of CL patients will have a reaction, the most common culprit being Thimerasol.
What type of soft CL is best for dry eye patients?
Daily silicone hydrogel.
Soft CL have reduced incidence of overwear symptoms (especially in high oxygen-permeable or high Dk).
What is a complication of poor lens fit or inadequate oxygenation of the cornea?
Corneal vascularization.
An ingrowth of superficial or deep blood vessels into the cornea that could be caused by Corneal oxygen deprivation or mechanical trauma from improper fit. Stromal or deep vascularization can result in Corneal scarring or intracorneal hemorrhage.
What refractive correction is best suited for Keratoconus or corneal scars?
Rigid gas-permeable CL.
RGP lenses have a large optical center allowing for better correction of Keratoconus and irregular astigmatisms
