Random CL questions 2 Flashcards
a combination solution for rigid contact lenses that contains both wetting agents and disinfecting chemicals
Wetting & Soaking solution
Silicone and oxygen are made into a siloxane which is then copolymerized with PMMA to create an oxygen permeable material used in the manufacture of rigid lenses
Siloxane/Silicon Acrylates
Vision that is temporarily distorted or out of focus when a contact lens wearer, particularly a rigid contact lens wearer, switches from contact lens to glasses.
The blur may be caused by corneal edema, mechanical molding, or a combination of two
Spectacle Blurr
a mercury compound, used as a preservative in some contact lens solutions, that has been implicated as the cause of many red eyes and other adverse reactions in contact lens wearers
Thimerosal
retention of fluorescein dye by damaged corneal tissue
Corneal staining
a substance that enables tears to spread evenly over the surface of a rigid contact lens and helps to cushion the lens on insertion
Wetting agent
a detergent-like cleaner that emulsifies debris and removes foreign substances from the surfaces of a contact lens
Surfactant Cleaner
the pumping in of fresh, oxygenated tears between the contact lens and the cornea and the pumping out of deoxygenated tears and metabolic wastes with each blind
This is necessary to maintain normal corneal metabolism
Tear Exchange
the process of reducing the number of viable micro-organisms to a level which is harmful neither to ocular health nor the quality of contact lenses and accessories
Disinfection
the date, designated by the manufacturer, beyond which a product should not be first used
Expiry Date
Inflammatory cells within the cornea occurring as a response to viral or other infection, toxic or chemical stimulus
Typically seen as greyish disciform patches near the limbus
INFILTRATES
a storage solution used to enhance the biocompatibility of RGP lens surfaces
Conditioning Solutions
agent intended to prevent the growth of micro-organisms in a care product
Preservatives
soft contact lens used to protect the cornea, reduce pain and assist healing in conditions such as bullous keratopathy, ulcers and burns
Therapeutic CL (for aniridia) / Bandage CL
Hydrogel lens prior to hydration:
Xerogel
Lens design consisting of the central radius and two peripheral curves
Tricurve
Fitting technique where the BOZR is selected to be parallel to the corneal surface
Parallel fit / Alignment Fit
Lens design consisting of the central radius and multiple peripheral curves
Multicurve
angle formed by a tangent to a sessile drop of fluid at the point where the drop meets a surface.
a more wettable material has a smaller angle of contact
the angle is zero for a completely hydrophilic material
Contact Angle
irregularity in the size of cells of the corneal endothelium
observed in extended wear and in long-standing PMMA wearers
Polymegathism
Method of soft lens manufacture employing heat and closed moulds
Cast molding
a contact lens fitting, usually steep, in which there is a proof of tears between the back surface of a hard lens and the anterior surface of the corneal apex
generally observed with fluorescein
Apical Clearance / Pooling
the time in seconds for the break up of the precorneal tears film in a non-blinking eye
generally observed with fluorescein and the slit lamp
TBUT
small vesicles in the corneal epithelium containing fluid and cellular debris
occurs as a typical response to corneal stress, particularly extended wear
Microcyst
staining of the nasal and temporal areas of the peripheral cornea
Frequently associated with conjunctival injection in the horizontal meridian
Influenced by dry eyes, poor blinking, lens design and lens material
3 & 9 o’clock Staining
distance between a point on the back surface of a lens at a specified diameter and the continuation of the back central optic zone
Measured along a radius of curvature of the latter
Radial edge shape
a contact lens fitting, usually flat, in which the back surface of the lens rests on the apex of the cornea
Generally observed with fluorescein
Apical Touch
a solution having the same tonicity as 0.9% sodium chloride
Isotonic Solution
the shaping of a lens, normally with a straight edge to assist with correct orientation on the eye in Toric or bifocal fitting
Truncation
the formation of trapped air bubbles beneath a contact lens
usually associated with hard lenses but can also occur with soft lenses
Dimpling
the thickness of the layer of tears between the back surface of a contact lens and the front surface of the cornea
Tear Layer
Technique for correcting presbyopia in which reading addition is incorporated into the contact lens for the non-dominant eye
MonoVision
achieved with a bifocal contact lens which positions both distance and reading portions in front of the pupil at the same time
Simultaneous Vision / Multifocal
Lens design where part of all of the back surface is of toric construction
the front surface may be either spherical or toroidal in which case it is a bitoric
Back Surface Toric
The reduction, modification or elimination of a visual defect by a programmed application of contact lenses
The technique for reducing myopia consists of changing the shape of the cornea by fitting a series of hard lenses progressively flatter than “K”
Also called corneal refractive therapy (CRT) and Overnight vision correction (OVC)
Ortho-K / OrthoKeratology
achieved with a bifocal contact lens which has distinct zones for distance and near
The lens must translate for the different portions to line up with the pupil area for the appropriate visual task
The reading segment may be either fused or solid and only hard lenses have only proved successful
Alternating Vision
Soft lens materials made from a combination of silicone rubber and hydrogel monomers
Silicon Hydrogel
Translucent or opalescent dimples containing cellular debris trapped behind a contact lens
Most often associated with silicone hydrogels and sometimes known as lipid plugs or pre-corneal deposits
Mucin Balls
Lens design consisting of the central radius and one peripheral curve
Bi-Curve
Methods used to measure the stability of the tears film without a staining agent
employing a cold diffuse light source or grid pattern for observation
NITBUT
Loss of tolerance to contact lenses from long-term hypoxia resulting in chronic oedema
Corneal Exhaustion Syndrome / Intolerance
Method of soft lens manufacture employing liquid polymer spun to the required shape in rotating open moulds
Spin Casting
Extreme, painful response to gross corneal edema as a result of excessive contact lens wear
usually found with PMMA and typically occurring in the middle of the night
Over Wear Syndrome
The smoothing of a lens transition with a curve intermediate between the two radii
Blending may be light, medium or heavy
Blending
A lens where the second radius is steeper than the base curve
Such lenses are used mainly for orthokeratology but also for other fitting applications such as corneal grafts and post refractive surgery
Reverse Geometry
a contact lens which fits over both the cornea and bulbar conjunctiva
Typical overall sizes are 22-24mm
Scleral Lens
a small disc made of various silicone and or various silicone and or plastic materials usually containing an optical correction which is worn over the cornea as an alternative to spectacles which can correct ametropias and presbyopia
Contact Lens
Contact Lens manufacturing method in which dry buttons of the lens material are cut with lathes
most labor intensive and least reproducible method of contact lens manufacture, but useful for production of small quantities or custom parameters
Lathe Cutting
a discontinuity or break in the epithelial tissue of thecornea associated with inflammation in the cornea that could be sterile or may be caused by bacterial, fungal or viral infection
Corneal Ulcer
a discontinuity or break in the epithelial tissue of the cornea associated with inflammation in the cornea that could be sterile or may be caused by bacterial, fungal or viral infection
Corneal Ulcer
The amount of oxygen diffusing through a given amount of lens material in a give amount of time, under specified testing conditions
Oxygen Permeability
