Chapter 14: Principles and Problems of Contact Lenses

Question 1

Basic Principles

Answer 1

1) Determine refractive error (Refraction)
2) Determine flat and steep corneal meridians, and axis
3) Choice of lens type based on medical and ocular history, and specific needs of the patient

Question 2

Characteristics of Contact Lenses

Answer 2

Prescription information:
1) Spherical equivalent, cylinder and axis
2) Diameter of lens
3) Base curve
4) Lens thickness
5) Material, polymer, or brand name
6) Edge blends or peripheral curves
7) Lens tint or lens color
8) Wearing instruction
9) Care regimen
10) Schedule of follow up

Advantages: they do not distort peripheral vision, do not fog, better for certain kinds o refractive errors (high power, keratoconus, nystagmus, irregular astigmatism)

Disadvantages: high maintenance, increased risk of infection, not recommended for certain environments (dust), higher cost, easier to lose

Question 3

Soft Lenses

Answer 3

Flexible contact lenses that permit oxygen and carbon dioxide diffusion through the lens material itself, with minimal tear buildup
Most commonly used lens type today

Advantages: More comfortable, rarely cause spectacle blur, less risk of overwear, less expensive
Disadvantages: variable vision due to dehydration of the lens, less durable

Question 4

Rigid-Gas Permeable Lenses

Answer 4

Contact lenses that permit oxygen and carbon dioxide diffusion through both the lens material and the tear pump

Advantages: More comfortable than PMMA, better suited for problems like keratoconus and irregular astigmatism
Disadvantages: more fragile and prone to protein deposit buildup, more expensive

Question 5

Spectacle Blur

Answer 5

Temporary blurred vision upon switching from contacts to eyeglasses

Question 6

Polymethyl Methacrylate Lenses

Answer 6

Contact lenses that provide oxygen by means of a tear pump only, there is no diffusion through the lens materials

Question 7

Oxygen-Permeable

Answer 7

The ability of a contact lens to transmit oxygen through it material

Question 8

Extended-Wear Contact Lenses

Answer 8

Soft contact lenses that are approved for overnight wear for up to 7 days
Associated with adverse corneal effects and corneal ulcers

Question 9

Daily-Wear Contact Lenses

Answer 9

Rigid and soft contact lenses intended to be worn for fewer than 24 hours consecutively while awake
Associated with oxygen depravation to the cornea if not used as directed

Question 10

Disposable Contact Lenses

Answer 10

Soft contact lenses designed for both daily and extended wear, and then to be discarded after 1-4 weeks

Question 11

Planned-Replacement Contact Lenses

Answer 11

Contact lenses that are designed to be replaced on a regular schedule determined by the ophthalmologist according to patient wearing characteristics and other factors (typically between 1,2,3,or 6 months)

Question 12

Toric Contact Lenses

Answer 12

A contact lens that is specified to correct astigmatism

Question 13

Bifocal Contact Lenses

Answer 13

A contact lens that is multifocal, consisting of a portion that corrects for distance and another portion that corrects for near vision

Question 14

Monovision

Answer 14

An artificially produced system creating visual clarity for near in one eye, and for distance in the other eye. This can be done with either contact lenses or surgically (LASIK or cataract surgery)
There is decreased stereopsis with monovision

Question 15

Keratoconus

Answer 15

A rare degenerative corneal disease in which the center of the cornea thins and assumes the shape of a cone, seriously affecting vision
Will typically have RPG contact lenses prescribed

Question 16

Corneal Bullous Edema

Answer 16

Swelling of the corneal tissue severe enough to cause blisters on the surface of the cornea and decreased vision

Question 17

Care of Contact Lenses

Answer 17

1) Cleaning and disinfecting the contacts in order to prevent infection and remove deposits
2) Lubricating the lenses
3) Using the lenses as instructed by the physician
4) Cleaning and Disinfecting
5) Lubrication

Question 18

Enzyme Cleaners

Answer 18

A specially designed detergent removing protein deposits from contact lenses

Question 19

Proteolytic Enzymes

Answer 19

Enzyme cleaners that are capable of dissolving proteins

Question 20

Triphasic Enzymes

Answer 20

A specialized cleaning agent that dissolved adhered substances on contact lenses

Question 21

Surfactant Cleaners

Answer 21

A specialized contact lens cleaning solution and wetting agent

Question 22

Insertion of Contacts

Answer 22

1) Wash hands
2) Remove lens from case
3) Rinse lens with saline
4) Place lens on tip of index finger
5) Pull down lower eyelid, look up, and place lens on lower portion of globe
6) Close your eyes and massage eyelid to center the lens

Question 23

Removal of Contacts

Answer 23

1) Wash hands
2) Look up, pull down lower eyelid and place index finger on lower edge of lens
3) Move lens down the globe
4) Compress lens between finger tips
5) Remove lens
6) Clean lens and place in storage case

Question 24

Problems with Contact Lenses

Answer 24

1) Allergies to lens solutions
2) Solution-Contact lens interaction
3) Overwearing syndrome
4) Improper contact lens fitting
5) Giant Papillary Conjunctivitis
6) Irritation and Tearing
7) Corneal edema, vascularization, infiltrates, corneal ulcer, infections, abrasions
8) Inability to remove lenses
9) Losing lens in eye

Question 25

Ciliary Spasm

Answer 25

A painful contraction of the ciliary muscle commonly caused by inflammation of the cornea or iris

Question 26

Contact-lens Induced Acute Red Eye

Answer 26

Dilation of blood vessels in the conjunctiva caused by contact lens irritation

Question 27

Giant Papillary Conjunctivitis

Answer 27

Inflammation of the palpebral conjunctiva, characterized by large-raised bumps on the underside of the eyelids

Question 28

Corneal Edema

Answer 28

Swelling of the corneal tissue

Question 29

Corneal Vascularization

Answer 29

Abnormal condition charactered by blood vessels growth in the cornea

Question 30

Corneal Infiltrates

Answer 30

A discrete collection of inflammatory cells in the cornea

Question 31

Contact Lens Peripheral Ulcers

Answer 31

Contact lens-induced noninfectious corneal ulcers outside of the visual axis

Question 32

Corneal Ulcer

Answer 32

Pathological condition involving a defect in the corneal surface and associated with inflammation; infectious ulcers are caused by a pathogenic organism

Question 33

Corneal Abrasion

Answer 33

A scratch or other defect in the superficial cornea caused by trauma

Question 34

Contraindication

Answer 34

Any condition that renders a particular treatment, medication, or medical device inadvisable for a particular patient

1) Ocular pathologic conditions
2) Inability to comply with hygiene regiment
3) poor/no blink reflexes
4) Moderate-severe dry eye
5) Disabilities that limit mobility
6) Occupation
7) Seizures