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CL 1 > Intro to CL > Flashcards

Intro to CL Flashcards

1
Q

First real contact lens

A

made by adolf fick -> scleral contct lens of blown glass

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2
Q

Hard CL

A

made of PMMA or polymethylmethacrylate

resistent but no oxygen allowed

used 1950-1980

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3
Q

Modern GP lenses (gas permeable)

A

1st gen GP: polycon, CAB
dia b/n 8.5-9.5 mm
-low oxygen transmitters

2nd gen GPs (Boston, Fluoroperm, etc)
- addition of siloxane to allow more oxygen

3rd gen GPs (Menicon-Z, Contex Paragon CRT)

  • daily wear 30 continuous
  • used for high cl rx errors
  • more oxygen permeable than soft cl
  • orthokeratology
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4
Q

Soft lenses (hydrogels)

A

Soft lenses has HEMA:
-oxygen and water attached to methacrylate
-soft and flexible -> improvement of comfort
-silicone hydrogels for extended wear
(B&L soflens, Vistakon)

silicone hydrogels (SiHy) for extended wear

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5
Q

Who developed HEMA

A

Dr. Otto Wichterle and Professor Drahoslav Lim

from a children’s toy

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6
Q

CL indications

A

Optical correction: myopia, hyperopia, astigmatism, aphakia, presbyopia, irregular astig

therapeutic: bandage lens for corneal disease, drug delivery to cornea and ant. seg
amblyopia: fogging or occluder lens

corneal reshaping: reduction of RE, myopia control

prosthetic: cosmetic enhancement

Keratoconus and irregular corneas (enabling these patients to see)

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7
Q

Caution with contact lenses

A

Pinguecula and pterygia

dexterity problems

hygiene considerations

environment concerns

severe allergies

dermatological problems: acne rosacea, stpah lid disease, psoriasis, eczema

allergies and respiratory disorders: Rhinitis, sinusitis, hay fever, and asthma tend to produce conj. injection and increased ocular sensitivity w/ cl

pts with sac (seasonal allergic conj.)

allergy symptoms: itching, tearing, photophobia, burning, mucus, increased tear debris

dry eyes, glaucoma, DM, thyroid dysfxn, herpetic disease, immunocompromise (HIV)

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8
Q

ocular side effects of systemic medication

A

oral antihistamines and decongestants: reduction in tear flow and increased dryness

acutane (acne medication): reduces meibomian secretion and increases dry eye symptoms; corneal infiltrates

diuretics (for edema and hypertension) can cause lid and conj. allergic rxn

valium: mydriasis, photosensitivity

dry eye: antihistamines, decongestants, oral contraceptives, antihypertensives, anticholinergics, muscle relaxants

refractive changes: topomax, oral contraceptives, acetazolamide

mydriasis: anti-cholinergics, anti-psychotics, antihistamines
miosis: codeine

ocular irritation: gold salts, salicylates

altered behavior: disulfuram (antabuse)

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9
Q

CL wear in the US

A

40.9 million americans 18 and older wore CL in 2014 => 17% of US adult population

10% GP, 20% soft, 2% hybrid, 67% silicone hydrogel

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10
Q

Soft contact lenses

A

hydrophilic

hydrogels (35-75% water)

  • soft,pliable
  • comfortable

oxygen transmission

  • ^H2O => ^ O2
  • dec. thickness => ^ O2

soft lenses - semi scleral

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11
Q

CL care and maintenance

A

huge industry

cleaning/rinsing/storing/disinfecting

purpose: limit deposit build up, kill harmful micro-organisms

toxic preservatives

compliance problems

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12
Q

Daily wear cl

A

worn during waking hours; removed before sleep; must be cleaned and disinfected before re-use unless daily disposable; replaced daily, 2 weeks, or monthly

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13
Q

extended wear cl

A

all day wear, including sleep;

typically worn 1-2 weeks without removal; if removed, must clean and disinfect if lenses are to be re-worn (max. 1 month)

greater risk of complications with extended wears usage

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14
Q

continuous cl

A

extended wear with no lens removal until such time that lens is to be replaced (typically monthly); no reuse; includes bandage contact lens wear

  • can wear 1-2 weeks without removal
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15
Q

disposable frequent replacement cl

A

daily disposable cl

  • eliminates care regimen
  • lower complications of DW
  • safest, most convenient way to wear CLs

varieties of DCL/FR CLs

  • correct myopia, hyperopia, astigmatism and presbyopia
  • tints for handling and for enhancing or changing color
  • uv blocking
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16
Q

silicone hydrogels revolutionized the industry

A

silicone hydrogel gives highest oxygen content

17
Q

Types of rigid cl

A

PMMA lenses

Gas permeable lenses

hybrid contact lenses

18
Q

PMMA lenses

A

made of transparent rigid plastic material called polymethylmethacrylate (PMMA)

excellent optics, no transmit oxygen

replaced by gp lenses

19
Q

Gas permeable lenses (GP or RGP lenses)

A

Rigid cl that look and feel like PMMA but allow oxygen to pass through them

advantage over soft/silicon hydrogel lenses is sharper optics due to rigid nature of lens material

20
Q

hybrid contact lenses

A

comfort of soft/silicone hydrogel and clear optics of rigid gas permeable

rigid gas permeable central zone surrounded by skirt of hydrogel or silicone hydrogel material

21
Q

Rigid lens design advantages

A

superior vision

durability

ease of care

added eye health safety characteristics

ability to correct irregular astigmatism

myopia control for young patients

22
Q

disadvantage of rigid lenses

A

initial discomfort (try to keep using positive terms)

allow dirt and dust under lens

unstable for sports or activities

requires more chair time and skill to fit

-teach upper lid touches lens

23
Q

Patient control on RGP

A

educate on benefit of RGP

be positive and watch your terminology

avoid: hurt, discomfort, irritation, blurry, hard
substitute: initial awareness, lid sensation, tickling, itchy, water, firm

24
Q

Anesthetic use

A

Concerns: staining, effect of eye rubbing, potentially misleads patient

benefits: sensitive patient become less apprehensive, accelerates time for diagnostic lens evaluation

25
Q

Contact lens for special needs

A

keratoconus and irregular corneas

bandage lenses for disease

red-green color deficiency and achromatopsia (restores color vision to distinguish colors)

prosthetic lenses (for albinism, aniridia, coloboma)

26
Q

contact lens fitting

A

evaluation of trial cl to determine rx

primary fitting criteria: good vision, good comfort, satisfactory physiological response

important role of centration and movement

goal: determine back surface design that is neither too steep nor too flat

27
Q

prefitting data for GP lenses

A

pupil size (and location)

palpebral fissure size

eyelid position

HVID (horizontal visible iris diameter): limbus to limbus horizontal

eyelid tension

blink (rate, frequency, fullness)

iris color

keratometry (mire quality)

28
Q

lid positions

A

if lid margin is at limbus = 0

if lid margin covers limbus = +

if lid margin is away from limbus (sclera showing = -

29
Q

blink types

A

partial

complete

twitch (rgps only)

forced

30
Q

cl workup includes

A

keratometry and/or corneal topography

updated manifest refraction and acuities

  • always adjusted for vertex distance to corneal plane when over +/- 4.00 D
  • prysbyopia/add determination

slit-lamp biomicroscopy

lid eversion

vital dyes: sodium fluorescein, rose bengal, lissamine green

remember: decrease vertex to cornea = less minus or more plus RX for glasses to CL

31
Q

sodium fluorescein

A

use in sterile strip form

used to prescreen corneal epithelium for healthy cl wear (no uptake) and to rule out dry eyes

used to evaluate GP patterns on eyes

used for post-cl wear health evaluation

32
Q

vital dyes

A

rose bengal is chemically related to sodium fluorescein; may sting on insertion; technically somewhat toxic to epithelium

lissamine green in non-toxic and does not sting

both rose and lissamine green are intracellular dyes:

  • stain devalized, desiccated cells (dry eye)
  • they both stain walls of dendrites in HSV keratitits where active virus resides

vital dyes stain intracellular: will be devitalized and stain walls of dendrites => active cells

sodium fluorescein stains inter-cellularly

33
Q

grading of stain

A

temporal 1/3

central 1/3

nasal 1/3

on scale of 0 - 3

34
Q

keratometry

A

measures corneal curvature

only central area

used to fit types of CLs

baseline for early disease detection

35
Q

corneal topography

A

keratometry measure only 4 pts (2 in each of two principle meridians)

corneal topography: typically measures 15,000 to 20,000 points all over cornea

36
Q

preliminary examination of ant. segment

A

eyelids

conj.

tears

cornea

anterior chamber

iris and lens

37
Q

biomicroscopy

A

used to examine front structures of eyes + surroundings
non-invasive viewing

high mag.

high illumination

inspection of both front and back cell layers of cornea

performed: before cl fitting or cl wear, to establish a ‘baseline’

38
Q

list for successful contact lens fitting

A

wearing time

comfort

vision

physiological response

appearance

CL 1 (5 decks)

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