Slit Lamp Bio-microscopy from contact Lenses -CSB Flashcards
What does it mean to be therapeutic?
Relating to the healing of disease.
What is Aphakia?
Aphakia is the absence of the crystalline lens of the eye
For myopes is visual acuity improved or decreased when comparing contacts to glasses?
Contact lenses provide a higher visual acuity for myopes than glasses
Why may acuity be decreased (when compared to glasses) for hyperopes when contact lenses are worn?
There is a possibility that the decreased acuity is due to decreased magnification and fluctuating accommodation.
How are slit lamps used in regards to Contact Lens Prescribing?
They are used in a contact lens fitting for baseline measurements and aftercare to check for lens fit, surface condition and ocular integrity.
What are concretions?
Little vacuoles or cysts filled with lipid
What are high, low and medium magnifications on a slit lamp used to look at in regards to the eye?
– Low 6-10x for general eye – Medium 16x for structures – High 25-40x for detail
What would low magnification on a slit lamp be used to look for?
- Lids/lashes • Cornea • Conjunctiva • Sclera
What would medium magnification on a slit lamp be used to look for in regards to Contact Lens Prescribing?
-Blepharitis • Meibomian gland dysfunction • Concretions • Corneal staining
What would medium magnification on a slit lamp be used to look for in regards to Contact Lens Prescribing?
-Epithelial changes • Stromal striae and folds • Endothelial folds, blebs, and polymegethism
What is your responsibility if you find any sign of corneal hypoxia in a contact lens patient?
Take the contact lens out. Not allow the patient to wear any lenses until the problem goes away and teach the patient about proper contact lens care.
What are Stromal Striae?
Fine grayish white lines in the corneal stroma. These represent localized separations of the highly ordered collagen
What are Stromal Folds?
More advanced striae where fluids have caused localized undulations (up and down outlines) or wrinkles in the cornea.
What do Stromal Striae lead to?
Stromal Folds
When are Stromal Striae or Folds present?
When corneal oedema is occuring.
What effect do corneal Straie or folds have?
They cause a loss of vision. (milky cornea).
What does the cobalt blue filter on a slit lamp do?
Excites Fluorescin
What does the green (red-free) filter do on a slit lamp?
Enhances contrast of blood vessels and rose bengal staining
What does the ground glass filter on a slit lamp do?
Diffuses beam to give broad unfocussed illumination
What does a neutral density filter on a slit lamp do?
Reduces beam brightness, increases patient comfort
What does a polarising filter on a slit lamp do?
Reduces specular reflections when used in crossed pairs
What is fluorescein staining used for in slit lamp?
It highlights epithelial defects as it stains areas of missing cells.
How long does it take the fluorescein dye to disapear?
2-4 minutes.
What filter/filters in slit lamp do we use in conjunction with fluorescin staining?
Cobal blue Filter however we may also use a Yellow (Wratten 12) filter to improve contrast.
(When a wratten 12 filter is used then you are looking out for green and everything that was previously blue is now black- essentially its like putting a yellow filter over a blue filter).
Do we add fluorescein to an eye that’s wearing a soft contact lenses?
No because fluorescein stains everything including the lens. The only time we would do this is if we are trying to check for the presence of a contact lens.
What is lissamine green stain used for?
Lissamine green is used in dry eye examinations . It stains dead and degenerative cells, but not healthy epithelial cells
What slit lamp filter is lissamine green used in conjunction with?
Red (Wratten 25) filter is used to enhance staining
When does optimum staining for lissamine green occur?
1-4 minutes
Does lissamine green stain cause discomfort for the patient?
A little
Which stain is more tolerable, Lissamine green or Rose Bengal (RB)?
Lissamine green
Is rose bengal stain uncomfortable for pateints?
Yes - It Stings!
What is Rose Bengal Stain and what does it do?
A fluorescein derivate that is able to bind to epithelial cells that are uncoated by certain proteins (mainly mucin).
It stains dead cells and healthy ones that are unprotected by an intact mucin layer
What are microcysts and why are they an important thing to look out for in regards to contact lens checking?
A tiny lesion filled with dead cell material.
They are very distinct and a definite indicator of contact lens induced hypoxia.
How can retro-illumination on slit lamp be used to identify vacuoles and microcysts?
Essentially both microcysts and vacuoles are spaces in the epithelium that are filled with either a gas or fluid. This means that the light that comes back from a point that you have illuminated is defracting/diverging or refracting/converging.
Whether the light hitting you back diverges or converges depends on what the space is filled with ( either gas or fluid -i.e. whether its a vacuole or microcyst).
What you would see in this case is like small circles that are half light and half black depending on where shadow has been created. - see picture attached.
What are vacuoles in the eye?
Cyst like inclusions (something embeded) which is filled with gas or fluid
Where do microcysts and vacuoles exist if they are present?
In the corneal epithelium
How can you diffrentiate between a microcyst and a vacuole using a slit lamp ( and retroillumination)?
So if the circle that you suspect to either be a vacuole or microcyst indication has a shadow on the same side as ur beam of light then its a microcyst. If the shadow is on the opposite side to the side where the beam of light exists then its a vacuole.
Why would there be a smile line staining pattern during corneal staining?
The patient doesn’t blink fully - the bottom part of their lensdries out - often from staring at computer
What contact lens patients may have dessication 3 & 9 staining ?
(3 and 9 refer to location on a clock)
Rigid Hard Contact Lenses (RGP) lenses
When may toxicity diffuse staining be seen?
By a patient that has an allergic reaction to the contact lens.
What are the different types of corneal Staining patterns?
