Corneal Disease Anterior And How To Detect Them Flashcards
Corneal abrasion
No need to dilate px or volk
Anterior eye problem
Measure visual acuity do all the before steps then diffuse parallelpiped optic section can put some fluorocein in to see where it is and to see the depth
Retro would be good as well
Corneal microcysts
If you use a beam or anything too wide what would happen
Again, same thing exactly. Optic section and move across to see if there is any reversed illumination within the microcyst and then see where this is in the cornea. Depth estimation.
Using something too wide would mask it so optic section is good as it is a narrow beam.
Put nafl in to see where it is, is it limited to the epithelium or is it leaching out into the stroma in which case you would need to do something more for the px eg antibiotics or artifical tears etc. can arise after wearing contact lenses.
Can use retro illumination to check for it as well, locate the microcysts under low magnification and then you can increase the magnification.
Irritable eyes contact lens patient
Anterior eye problem
Check diffuse all of diffuse then do parallelpiped then do optic section put some nafl
Check for corneal microcysts optic section and retro
Contact lens px so check endothelium for endothelial polymegathism using specular
Endothelium obstructed so check for corneal oedema using sclerotic scatter
Indirect or retro to check for vascularisation across the cornea or limbus
Around the limbal region check for neovascularisation may have occured as contact lens complications can lead to limbal changes- via indirect illumination w light adjacent to the cornea
Contact lens stuff
Contact lens wettability
What can diffuse be used for for contact lenses
Contact lens wettability is how easily a liquid spreads over the surface of a contact lens as we need a good wetting surface to prevent changes to the under surface of the eyelid as it blinks over the contact lens throughout the day= use specular reflection for this
Diffuse can help evaluate the quality of the tear film and detect if there is any unwanted debris in it, can be used with nafl and cobalt blue to view fluorescein patterns when fitting hard contact lenses, can assess lens position and see if there is adequate movement, detect lens defects, determine surface quality and also wettability of lenses. So wettability is both diffuse and specular.
What can parallelpiped and optic section be used for for contact lenses
Parallelpiped can be used with NAFL to evaluate how lenses interact with the corneal tear film and fitting
Optic section can be used to evaluate the tear layer under a permeable lens and to aid in the fitting process. Tear meniscus and tear film.
What can indirect and retro be used for contact lenses
Indirect- used to check for neovascularisation= overwear of contact lenses. Limbal or corneal
Retro illumination- fitting of contact lenses, to detect lens surface deposits as it illuminates them from behind helping to determine their shape and depth, view edges of soft contact lenses, observing cornea for oedema
What is sclerotic scatter and specular reflection used for for contact lenses
Sclerotic scatter- corneal oedema
Specular— endothelium. Tear film or tear cornea. Contact lens wettability, lipid tear film particles can be seen moving in front of the corneal surface w every blink of the px so you can test Tbut, you can also study tear meniscus.
What is slit height used for contact lenses
And describe the pre corneal tear film and measure of tear meniscus height and curvature
Why do we measure tear break up time and how
Slit height is used to measure tear meniscus height to see if the px has enough tears to wear contact lenses. Tear meniscus can be studied using optic section or specular reflection.
corneal tear film covers the ocular surface and protects the eye from the environment, lubricates the ocular surface. Measures of tear meniscus height and curvature are used to determine the absence of or presence of dry eye.
To test for tear break up time fluoroscein is used under slit lamp and we examine lipid tear film particles moving in front of the corneal surface with every blink of the px= specular reflection. So lipid tear film particles can be seen moving in front of the corneal surface with every blink. Tbut of less than 10= dry eyes and an abnormal tear film.
Suspected peripheral retinal tear how do I detect this with funduscopy
Where does illumination come from and where is the image formed and what is the image like
Most certainly not with parallelpiped or optic section or anything as it has to be straight on looking at the retina
Posterior so dilate and binocular indirect ophthalmoscopy. Firstly use a slit lamp with a volk lens to look at the fundus. Dilate eye make sure to take pre and post iop measurements, focus slit lamp using a parallel height type beam and a focusing rod and then focus on the centre of the cornea till it is in focus. Add your volk lens and pull back slowly till you see scratches on the lens and then pull further back till the fundus comes into focus.
Illumination comes from above and bounces off the centre to create an aerial image between the slit lamp and the examiner. The condensing lens creates an inverted and laterally reversed image of the pxs fundus so the condensing lens needs to move in opposite directions than expected. 78D and 90D lenses can see into mid periphery past the macula. Then take over with your binocular indirect ophthalmoscopy exam.
Describe the volk lenses and condensing lenses in general
Ranges from 60D to 90D and as the powers increase fov increases but magnification and wd decreases as flatter so lower power volks focus light over a greater distance.
Condensing lenses are also tinted yellow to decrease px discomfort and to protect the retina from photo toxicity.
Reflections from the lens surface need to be controlled.
now how do we continue this examination with head mounted BIO
Now we’ve looked at posterior segment, nerves, vessels, macula and periphery using the slit lamp and 78 and 90D lenses, now we want to look farther into the retina so at the peripheries so to do this we use head mounted BIO with 20 and 28D lenses so it allows for a less magnified but large field of view at the back of the eye.
Adjust it so it is eye level. Turn the beam on and it should have different sizes so use medium to wide starting with wide, tell px to look in different gazes to examine different areas of the retina. Keep your head still and you should see the retina in the whole lens.
what other things could we do to examine the posterior segment in detail so retina
You could use hruby lenses with slit lamps to look at the retina and optic nerve. Type of condensing lens placed directly on the surface of the eye, has a high mag and wide fov and allows examiner to examine posterior segment in detail. However because it has contact with the eye may cause temp blurring of vision and may require anaesthetics and may be hard to use on px with small eyes. Poor px fixation and glare tolerance and affected by media opacities.
Could also use scleral indentation with binocular indirect ophthalmoscopy- to confirm holes or tears but again need to be dilated.
Mirrored lenses have contact with the cornea and can view the mid and far periphery, 20D lenses and they can be used with a direct ophthalmoscope to examine the retina. Mirrored surface of a lens can help reduce glare and increase visualisation= helps to reflect light into the eye.
Talk about some advantages with binocular indirect compared to direct
What are some things we can see with binocular
And why is there a much sharper image in the presence of media opacities
Increased detail of fundus seen, greater fov
Stereoscopic view so can see disc cupping, raised lesions, retinal tears, sub retinal neovascular membranes, any feature with height or depth.
Rx has no affect on mag
Media opacities dont affect mag
Great wd
However px often need dilating- mydriatic= tropicamide and sympathomimetic= phenylephrine which may cause blurred vision and photosensitivity
Can also use Oct to look at the retina in detail
Much sharper image in the presence of media opacities due to a greater intensity of light source and bc the image is formed anterior to the eye.
Where things are in the eye using slit lamp and volk lens
Macula- move nasally w the lens to locate it eventhough it is temporal from optic disc
Scan across w joystick to se entire posterior pole, mid periphery etc, ask px to look up and tilt lens upwards to look at superior retina looking through inferior of volk lens and do same thing w 8 cardinal gaze directions to view the retina
Up, up and right, right, then straight down, down and left and left and then look right at them to see a good view of the nerves blood vessels and macula
Flashes and floaters
Retinal detachment, retinal tears, posterior vitreous detachment
Retinal tears and detachments in the mid periphery are most likely to be seen with BIO, 60 percent of these px have a retinal deatachment. So again previous technique
Looking for schafers sign which is a sign of retinal detachment caused by rpe cells that migrate and gather in the anterior vitreous behind the lens.
Also Look for tobacco dust in the area behind the lens. When px is asked to look up and forwards this becomes easier to see. Small dots are significant and wisps and strands are less. If found Schafers sign= px has certainly had a retinal break or a tear.
