angle closure glaucoma and gonioscopy Flashcards
which type of patients are most susceptible to getting angle closure glaucoma
it is a disease of the over 50’s and is more common in women and hyperopes ( > +8D smaller eyes)
what is the cause of an ACG attack
when the anterior iris comes into contact (blocks) with the trabecular meshwork or the posterior cornea.
this prevents aqueous outflow causing a sudden rise in IOP and is very painful
what produces aqueous and where does the aqueous leave through to get into the anterior chamber
aqueous is produced by the ciliary processes and leaves through the canal of schlemm via the venus plexus
in an open angle, which route does the aqueous take to leave the eye
aqueous moves from posterior to anterior chamber and leaves the eye via the trabecular meshwork
what is the principle factor affecting aqueous outflow and why
the venous pressure, as there are veins here which can resist aqueous outflow
what is iris bombe, and what affects can it have
iris bombe is when the iris bows forward and obscures the angle
what causes the ability for fluid to leave the eye with age, resulting in increased IOP
with age the trabecular meshwork gets blocked and melanin stays in the eye: cells float off the iris e.g. pigment epithelial cells and can drift into the trabecular meshwork, and the macrophages there will phagocytose the pigment epithelial cells, leaving melanin and granule cells in the trabecular meshwork.
what is the cause of angle closure
an increased pressure in the posterior chamber, pushes the iris forwards blocking the trabecular meshwork, this obscures the angle and there is no way for the aqueous to leave the eye = rise in IOP
what does the iris become like when it sticks onto the anterior surface of the lens
iris becomes immobile and sluggish
what is a indirect goniolens composed of and what are the different versions
- a 90D volk lens
- mirrors
some can have a single lens and others can be 4 mirror versions
what does a mirror from each phase show with a indirect goniolens
the opposite angle
how do you use a indirect goniolens to assess a patients angle
- place the indirect goniolens on the patient’s eye with lubricating fluid
- too much pressure can distort the angle, so use gentle pressure
- if you want to see the superior angle, you need to look through the inferior mirror and you can see the structures within the chamber
- rotate the mirror to look at all parts of the angle
- the angles will look slightly magnified
what part of the indirect goniolens do you need to look through if you wish to view the superior angle on a patient
look through the inferior mirror
which indirect goniolens is mainly used by ophthalmologists
koeppe indirect goniolens
list the 4 structures that are found in the anterior chamber angle
- schwalbes line (descements membrane)
- scleral spur
- trabecular meshwork (canal of schlemm)
- ciliary processes
what is the main thing that you want to see when looking at an angle with a indirect goniolens, which indicates that the angle is open
trabecular meshwork (tells you the angle is open)
where does schwalbes line sit in the eye
at the base of he cornea i.e. descements membrane = where light comes in and meets
what structure is anything above the scleral spur
trabecular meshwork
what structure is fond below the scleral spur
ciliary body
what is the scleral spur a marker to show
to show that the angles are open because above it is the trabecular meshwork
why is the scleral spur easy to see
because it is white which will always remain white with age
which angle is the most open and why should it be viewed first
the inferior angle in the widest and should be through the superior mirror with the indirect goniolens
the major landmarks will be able to be viewed in the inferior angle, so you can familiarise yourself with the structures and then move on to see the more narrow angles
what colour is the trabecular meshwork usually, and what colour does it become as you age and why is this
it is usually pink and becomes more brown as you age as it picks up on the melanin and pigmentation from the iris
which structures can be viewed in a grade 4, classified by the schaeffer grading system, when using a indirect goniolens
all 4 structures:
- ciliary body
- scleral spur
- trabecular meshwork
- schwalbes line
characteristic of myopia and aphakia
ciliary body can be seen with ease
which structure can be seen with ease in a grade 4
ciliary body
which structures can be viewed in a grade 3, classified by the schaeffer grading system, when using a indirect goniolens
- scleral spur
- trabecular meshwork
- schwalbes line
but not the ciliary body
which structures can be viewed in a grade 2, classified by the schaeffer grading system, when using a indirect goniolens
- trabecular meshwork - only can be viewed
you lose view of the scleral spur
which structures can be viewed in a grade 1, classified by the schaeffer grading system, when using a indirect goniolens
- schwalbes line - only can be viewed (or maybe the top of trabecular meshwork)
which structures can be viewed in a grade 0, classified by the schaeffer grading system, when using a indirect goniolens
can’t see anything
when viewing the angle on a slit lamp, what indicates that that the angle is closed
the beam of the iris will intersect (be continuous with) the beam of the cornea, so there will be no junction/separation between them = iridocorneal contact
when viewing the angle on a slit lamp, what indicates that that the angle is not closed
the beam of the iris and cornea separates at an interface = no iridocorneal contact
how is a grade 0 (closed angle) identified
it is a closed angle due to iridocorneal contact and is recognised by the inability to identify the apex of the corneal wedge
how does the goniolens distinguish between ‘appositional’ from ‘synechial’ angle closure
with appositional angle closure, the goniolens can push the iris away but with synechial (anterior uveitis) angle closure the goniolens cannot push the iris away and the angle will be blocked
what structure is the border where light hits descements membrane
schwalbes line
what is the white band viewed in the angle
scleral spur
what is found sticking on the scleral spur and trabecular meshwork in angle closure glaucoma
iris processes
why are hyperopes at a greater risk of having an ACG
because there iris curves forwards (as it has a convex shape)
what is a concave iris, or myopes at a greater risk of having
pigment dispersion syndrome
the iris is big, and pigment is flying off
what is found in pigment dispersion syndrome
known as the chocolate box line
it is excessive pigment in the trabecular meshwork
other pigment may also be seen settling onto and anterior to schwalbe’s line (onto posterior surface of the cornea) = sampaolesis line
what is the name given to excessive on and anterior to schwalbe’s line
sampaolesis line
what are normal iris blood vessels never attached to and what is the appearance of normal iris blood vessels
never attached to structures anterior to the scleral spur
normal blood vessels are thick and have a definite pattern (circumferential or radial), they loop around the base of the iris and always below the scleral spur
what is the appearance of normal blood vessels and where do they extend through
they are more feathery and have an erratic pattern (does not follow a radial pattern) and also more thinner and are undirectional
they extend past the scleral spur and into the trabecular meshwork
what other condition will you look out for if you see a patient with neovascular vessels
a px who had a central retinal vein occlusion as they can have a 90 day glaucoma and then neovascular in the anterior chamber
