Contact Lenses Flashcards
(38 cards)
Contact Lens
A corrective, cosmetic, or therapeutic lens usually placed on the cornea of the eye. Contact lenses usually serve the same corrective purpose as conventional glasses, but are lightweight and virtually invisible.
Wearing Schedule Categories
Daily disposable, extended wear or frequent replacement
Daily Disposable
Soft Contact Lens applied after waking and removed before going to sleep. Worn only one day and then disposed of.
Extended Wear Contact Lenses
- Approved for wearing twenty- four hours. Includes sleeping with lenses on the eye.
- Available for continuous, or overnight wear that ranges from one week to thirty days.
- Usually soft contacts, but can be RGPs also.
Frequent Replacement Contact Lenses
Soft contact lenses that are only used for a specified period of time, such as 2 week, 1 month or 3 months. Rigid gas permeable (GP) lenses and some specialty soft lenses are meant to be replaced annually.
Contact Lens Types
1.) Soft contact lens
2.) Rigid contact lens (rarely used)
3.) Rigid Gas-permeable/ Gas-permeable (GP) contact lens,
4.) Hybrid lenses.
What Is A Contact Lens Wearing Schedule?
How long each type of contact lens is made to be worn.
Disposable
To be discarded according to a prescribed schedule. They may be discarded after one day, one week, two weeks, one month after starting routine wear
Soft Contact Lens
- Made from polymers or materials that absorb water.
- Always kept in solution to keep them from drying out/breaking.
- Very flexible and comfortable.
- Last shorter than GPs.
*Harder to handle, but they are easier to adjust to.
What Is Water Content in Soft Contact Lenses?
How much fluid the lens polymers contain. Low water content typically has 38% water or less. High water content usually has 55% or greater water in it.
Rigid Contact Lenses “Hard Lenses”
*Rarely used
*Made of polymethylmethacrylate (PMMA).
*Didn’t allow oxygen to flow to cornea resulting in corneal edema/swelling.
Gas-Permeable Contact Lenses (GP)
- Replaced Rigid Lenses “Hard Lenses.
- Made from polymers and plastic materials that are oxygen-permeable.
- Less comfortable can be drier, but provide sharper vision.
- Also known as rigid gas-permeable, or simply gas-permeable (GP) lenses.
- Usually last longer than soft contact lenses.
- Easier to handle.
- Custom made for patient.
- Come in single vision, toric and bitoric, multifocal and ortho-k. Also scleral lenses.
Routine Contact Lens Care
Includes cleaning, rinsing, and disinfecting as needed. Done after the lenses are removed from the eye, not before wearing. If stored in case:
1.) Dump all solution out from the case wells
2.) Rub case with clean finger for at least five seconds
3.) Can use more solution to clean it out. Then dump it again. Best to avoid using tap water.
4.) Store case upside down with lids off/open.
Contact Lens Fitting/ I&R (Insertion And Removal) Training
Patient is instructed on:
1.) Handling procedures (always wash hands before handling the lenses, how to tell if the lens is inside out, right lens vs. left lens etc.)
2.) How to Apply and remove the lenses.
3.) How to care for them at the dispensing visit.
Given a wearing schedule to follow in order to gradually build up the amount of time the lenses are in the eye. They will also be given a schedule of follow-up visits so the health of the eye and the contact lenses may be evaluated on a regular basis. Encouraged to adhere/comply with, the prescribed regimens.
Three S’s rule for daily disposable contacts
Do not
1.) Sleep
2.) Shower
3.) Swim
In them.
Contact Lens Parameters
Measurements on a contact lens that correlate with the shape of the patient’s eye
Base Curve Radius (BCR; BC)
Primary curve on the posterior (backside of lens). Curve designed to approximate the shape of the cornea (front part of eye) measured in millimeters. Can be measured using Keratometer or Radiuscope.
What Determines The Contact Lens Power?
The prescription strength (sphere or sphere, cylinder and axis)
Are Eyeglass and Contact Lens Rx’s Same Prescription?
Not always since eyeglasses sit in front of eyes and contacts sit on eyes.
Vertex Distance
Distance from where the back of the eyeglass lens rests in front of the eye to where the contact lens rests on the eye.
What is contact Lens Overall Diameter (OAD, Diam.) ?
Diameter is the size of the lens when measured from edge to edge at the widest point. Small gas-permeable lens is generally 8.50 mm to 9.50 mm. Standard diameter for hydrogel and silicone hydrogel lenses is between 11.0 mm and 15.0 mm. Scleral lenses are another type of larger diameter GP lens which can reach to 22.0mm or higher
What Is The Optical Zone Diameter (OZD; OZ)?
Central area or zone of the lens that provides optical correction for the patient’s vision. Measured in Millimeters.
What Are Peripheral Curves On A Contact Lens?
Additional curves on the back surface
of the lens that surround the optical zone. Help tailor the contact lens fit to the individual patient. In a normal eye the cornea is steeper in the center and it flattens toward the periphery. These curves allow the back surface of the contact lens to imitate the gradual sloping of the cornea.
Edge And Center Thickness
Refers to the thickness of the center of the lens from posterior to anterior surface (center thickness) or the thickness of the lens at the edge
