indications for CLs, slit lamp use in practice, record keeping and staining Flashcards
Name the two materials of two types of RGP contact lenses
- Polymethylmethacrylate (PPMA)
2. (Rigid) gas permeable (R)GP
List the 4 different types of contact lenses
- Rigid gas permeable (RGP)
- Soft
- Hybrids
- Silicone rubber (SRCL)
List the sizes of RGP lenses
- smaller than corneal diameter (+/- 9.5mm)
- semi-scleral (+/- 14mm)
- scleral (+/- 18mm)
What was the first hard contact lens material
PPMA
Since when were PPMA lenses made
1946
What is a disadvantage of PPMA
Difficult to fit
& allows 0% of oxygen through the lens
What is the advantage of rigid gas permeable lenses over PPMA
RGP lenses allows oxygen to go through the lens
How does the cornea get oxygen when using an RGP lens
Behind the lens, so the cornea will take oxygen from the tears
Name the two different material types of soft contact lenses
- Hydrogel
2. Silicone hydrogel
What is the disadvantage of hydrogel lenses
Can get dry at the end of the day and then can lose its shape
What type of material is a hydrogel lens
Hydrophilic
With different water contents (amount of water in them)
What is silicone hydrogel lenses a mixture of
Silicone rubber
&
Hydrophilic materials
What does silicone hydrogel lenses contain a high amount of
Oxygen
What category of lenses are silicone hydrogel
Extended wear
What is the purpose of extended wear contact lenses
Can be worn over night
What size is soft lenses
Larger than corneal diameter (+/- 14mm)
Describe the material of hybrid contact lenses
Rigid centre
&
Soft skirt attached
Why do hybrid lenses have a rigid centre
Provides good vision like an RGP lens
Why do hybrid lenses have a soft skirt attached
Provides comfort like a soft CL
What type of lens is a silicone rubber (SRCL)
Hydrophobic (made hydrophilic)
What size is the silicone rubber SRCL
Lombok size
What is a silicone rubber SRCL extremely high in
Oxygen permeability
What is silicone rubber SRCL mainly used for
Therapeutic use only
Name some therapeutic uses of silicone rubber SRCL
- aphakia
- corneal irregularities
- dry eyes
list the motivations for using contact lenses
- cosmetic
- convenience
- refractive, pathological
list 5 indications for using contact lenses
- refractive
- cosmetic (plano colour)
- sports (head contact, fast movement, but avoid RGP lenses)
- occupational (armed forces, sports, entertainment industry)
- pathological
explain 4 refractive indications for the use of contact lenses and myopia
- improved acuity
- greater FoV
- normal eye size
- myopia is controlled
explain 3 refractive indications for the use of contact lenses and hyperopia
- greater FoV
- normal eye size
- possibility of reduced acuity
why is there a possibility of reduced acuity for a hyperope who wears contact lenses (give 2 reasons)
- less mag with contact lenses
- can control accommodation with specs
explain the refractive indication for contact lenses and anisometropia
- uniocular (RE plano LE -6.00DS) or binocular (RE -2.00DS LE -14.00DS) is more visually comfortable
explain 3 refractive indications for the use of contact lenses and astigmatism
- greater success in myopic eyes
- greater success if DC
explain the refractive indication for contact lenses and binocular vision problems
only vertical prism in 1 eye possible
list the pathological indications for contact lenses (list 8)
- cranio-facial anomalies
- allergies
- irregular cornea
- keratoconus
- aphakia
- bandage
- protection
- cosmetic (so both eyes look the same e.g. a coloured contact lens)
list the 4 contra-indications of contact lenses and occupation
- dust
- chemical vapours
- PC use
- poor ventilation
list the 3 contra-indications of contact lenses and allergies
- hayfever
- eczema
- sinusitis
list the 4 contra-indications of contact lenses and poor hygiene
- regular onset of conjunctivitis
- blepharitis
- herpes zoster
- smoker
list the 3 contra-indications of contact lenses and ill health - implications on tear film quality
- DM
- hyper or hypothyroidism
- arthritis
list the 3 contra-indications of contact lenses and age - ability to handle contact lenses
- infant
- student
- presbyope
list 5 choices for choosing RGP lenses
- vision (is better)
- corneal irregularity
- dry eyes
- compliance
- SCL failure
list 3 choices for choosing SCL
- infrequent wear
- environment
- RGP failure inc fitting problems
list the 2 reasons for slit lamp use and contact lenses
- CL fitting
- baseline measurements - aftercare
- lens fit
- surface condition
- ocular integrity
list the 3 levels of magnification required on a slit lamp in relation to contact lenses
- general eye - low 6-10x
- structures - medium 16x
- detail - high 25-40x
explain the 4 observations of slit lamp use in CL practice on a low mag for general eye
- lids/lashes
- cornea
- conjunctiva
- sclera
explain the 4 observations of slit lamp use in CL practice on a medium mag for structures
- blepharitis
- meibomian gland dysfunction
- concretions
- corneal staining
state the severity of stromal oedema of 0-5%
safe
explain the 3 observations of slit lamp use in CL practice on a high mag for details
- epithelial changes (any staining)
- stromal striae and folds (in stroma)
- endothelial folds, blebs (of missing endothelium) and polymegathism
state the severity of stromal oedema of 5-10%
caution
state the severity of stromal oedema of 10-15%
danger
state the severity of stromal oedema of 15-20%
pathological (loss of transparency & loss of vision)
which filter excites flourescein
cobalt blue
what is the green (red-free) filter used for
enhances contrast of blood vessels and rose bengal staining
what is the neutral density filter used for
reduces beam brightness, increases patient comfort
what is the round glass filter used for
diffuses beam to give broad unfocused illumination
what is the polarising filter used for
reduces specular reflections when used in crossed pairs
what does flourescein do
highlights epithelial defects as it stains areas of missing cells
how long does the flourescein dye last for
2-4 minutes
which other filter is used with flourescein to enhance staining/improve contrast
yellow (wratten 12)
what does lissamine green stain
dead and degenerative cells
name the stain which allows to see more staining than flourescein
lissamine green
how much discomfort is there with lissamine green
little
how long is optimal staining of lissamine green
1-4 minutes
which intensity of illumination should lissamine green be used with
low
which filter is used to enhance the lissamine green staining
Red (wratten 25)
what does rose bengal stain
dead cells and those unprotected by intact mucin layer
what is rose bengal used to investigate
dry eye
what sensation does rose bengal staining cause
stinging
what does rose bengal show in the eye
high areas of toxicity in eye
what is direct illumination of slit lamp in relation to the beam
within the beam
what is indirect illumination of slit lamp in relation to the beam
outside the beam
what is diffuse used for
general overview, see whole of CL
what is parallelepiped used for
scan the cornea, conjunctiva and CL
what is optic section used for
assess depth (increase mag)
what is specular reflection used for
assess tear film (horizontal beam) and endothelium (high mag)
what is retro illumination used for
back light from iris or fundus
where are micro cysts and vacuoles found
epithelial layer of cornea (intra epithelial)
which slit lamp technique is used to observe micro cysts and vacuoles
retro illumination
what are vacuoles and micro cysts
small bubbles in the front surface of the epithelium
what is a description of a vacuole
cyst like inclusions
what are vacuoles filled with
gas or fluid
what are microcysts a distinctive and easily detectable indicator of
contact lens induced hypoxia
what are micro cysts filled with
dead cell material
explain the unreversed effect
if light is shone from the right, the shadow is on the left and structure is on the left
which structure uses the unreversed effect
vacuole
what is the reason behind the unreversed effect
there is a lower refractive index of material (gas or fluid) that sits in the vacuole
explain the reversed effect
if light is shone from the right, the shadow is on the right and structure is on the left
which structure uses the reversed effect
microcyst
what is the reason behind the reversed effect
there is a higher refractive index of material (dead cell material) in the microcyst
what is a slit lamp routine CL fit used to observe
- tear film
- lid margin inferior & superior (for meibomian gland dysfunction)
- lashes inferior & superior
- palpebral conjunctiva inferior & superior
- bulbar conjunctiva 4 segments (ISNT)
- cornea 5 segments (CISNT) c=central
state the slit lamp routine 1
start with white light
general look at ocular adnexa
- diffuse, low mag, whole eye at once
- sclerotic scatter, low mag, ALERTS!
increase mag, parallelepiped scan for
- lashes and lid margins
- tear prism height and continuity
- conjunctiva
- cornea: swing nasal-temp and back, two times. check whole cornea
change to optic section on high mag to assess depth of anything unusual
while scanning cornea view direct and indirect
investigate limbus separately
state the slit lamp routine 2
then use blue light and flourescein - TBUT - timing, position - tear prism - height and regularity - lid margin - staining conjunctiva 4 segments & cornea - location, depth & extent
state the slit lamp routine 3
back to white light - lower lid eversion - meibomian glands push & squeeze - upper lid eversion white light - hyperaemia blue light - roughness/papillae
state the slit lamp routine 4
lens fit and condition
- diffuse for centration and movement of lens
- direct for fit and surface condition
dryness, broken/chipped, deposits
what are the advantages of real life photos of clinical grading
they are real eyes so can see a real life image
what are the disadvantages of real life photos of clinical grading
- different patients in different pictures
- some pictures have different illuminations for the same problem
what are the advantages of the animated pictures of clinical grading
it is the same eye so no variance
what are the disadvantages of animated pictures of clinical grading
cannot relate to real patient
list the 3 reasons of a legal document
- accurate recording of presenting signs and symptoms
- respond to complaints
- proof that standard of care was met (if not written, it was not done)
what is the advantage and reason for using standardised grading scale
uses common language and reduces intra/inter observer variability
list 5 reasons why record keeping is very important
- monitoring progression
- record across time, within and between practitioners
- impact new therapies or management
- medico-legal requirements
- patient communications
what is the severity of grade 0
normal
what is the clinical interpretation of grade 0
no action required
what is the severity of grade 1
trace
what is the clinical interpretation of grade 1
action rarely required
what is the severity of grade 2
mild
what is the clinical interpretation of grade 2
action possibly required
what is the severity of grade 3
moderate
what is the clinical interpretation of grade 3
action usually required
what is the severity of grade 4
severe
what is the clinical interpretation of grade 4
action required
what are the corneal staining rules
- chose a scale and stick with it
- always write which scale you used
- don’t guess the scale, look it up
grade ~/>1 = clinically significant
grade ~/>3 = requires management plan
corneal staining is…
- clinically insignificant in 60% of CL wearers
- often asymptomatic (i.e. severity signs not related to symptoms)
- in 35% of non CL wearers due to incomplete blink or closure
what type of corneal staining is ‘smile’
desiccation
what type of staining is ‘linear’
foreign body
what type of staining is ‘SEAL’
mechanical
what type of staining is 3&9
desiccation
what type of staining is diffuse
toxicity
