Glaucoma part 1, 2 and 3 Flashcards
What are the increase % of glaucoma ?
by 44% from 2015-2035
What is glaucoma ?
- a disease of the optic nerve
- gets worse over time
Definition of glaucoma
is a group of progressive optic neuropathies
that have in common a slow progressive degeneration of
retinal ganglion cells and their axons, resulting in a
distinct appearance of the optic disc and a concomitant
pattern of visual loss”
“A disease of the optic nerve with characteristic changes in the optic nerve head (optic disc) and typical defects in the visual field with or without raised intraocular pressure.”
How do we classify glaucoma?
either primary or secondary
What is primary ?
Occurs without any preceding ocular or systemic disease
95%
What is secondary ?
Develops as a consequence of an ocular or medical comorbidity
(5%)
e.g someone taking steroid drops after cataract surgery ,could have a risk of increasing IOP
What can we subcategories primary glaucoma into ?
open angle (85%of glaucomas) closed angle (15% of glaucomas) congenital glaucoma (less than 1%)
What is an open angle glaucoma like when examined?
no obstruction visible for the aqueous to flow from ciliary body from posterior chamber into the anterior chamber travelling into the trabecular meshwork into schlemms canal.
when examine the angle there is no obvious obstruction of the outflow to the aqueous
What is closed angle glaucoma like when examined?
the iris stick down to posterior cornea obstructing the outflow of the aqueous causing IOP to rise.
Peripheral iris causes a significant obstruction to aqueous outflow through the trabecular meshwork
What does prevalence mean?
Prevalence is the number of all cases in a given population at one point in time
What is the prevalence of Primary Open Angle Glaucoma?
2% in the over 40s in UK
8% in Black population
10% in the over 75s in UK
What is the prevalence of Primary Angle Closure Glaucoma?
- 4% in UK
1. 26% in China
What are the risk factors for POAG?- Primary OPEN angle glaucoma
-Ocular:
High IOP – modifiable risk
Myopia
Corneal thickness
-Demographic and Genetic: Age prevalence – over 40yrs: 2%, over 75 years: 10% Race – African ethnicity - 4x more risk Gender - Men more than women Family history - 6.7%
-Systemic Disease
Diabetes (3.3%)
Migraine/Vasospasm?
How do we detect POAG?
-is asymptomatic until end stages of disease
-Optometrists play a leading role in the detection of glaucoma
-Triad of tests:
IOPs
Optic Disc
Visual Fields
-Also important to assess the angle
What is the most important risk factor in POAG?
raised IOP
What is the prevalence of IOP in px with POAG?
Definition of glaucoma does not include the phrase “raised IOP”
Up to 50% of patients with glaucoma have normal IOP
=Ocular Hypertension (IOP>21mmHg in the absence of glaucoma) – prevalence 2.7% - 10%
What factors are the value of IOP measurement affected by ?
Diurnal variation – higher in morning
Central corneal thickness CCT
What do we assume when we are measuring IOP?
The Imbert-Fick law assumes that the cornea has a dry surface, is infinitely thin, and behaves as a membrane where the applanating pressure = IOP.
What is the impact of CCT on our measurement of IOP?
-Average CCT is approximately 540 μm
But CCT can range from around 440 μm to 640 μm
-GAT closest to true IOP when central corneal thickness CCT = 520 μm
What Will a thin CCT result in ?
an underestimation of IOP Thin = uNder
What will a thick CCT result in ?
A thick CCT will cause an overestimation of IO
How do you record for IOP ?
Record:
Instrument used (GAT is gold standard )
Time of day
Mean reading
Repeat readings at different time of day
Check National Guidelines on when to refer
What is the optic disc rule?
- good to determine the neuroretinal rim on the start if the optic cup - give cup:disc ratio
- determine margin of disc for this
What is the optic disc assessment ?
1. CD Ratio >0.6 be suspicious >0.15 change in C/D ratio over time 2.Neuro-retinal rim ISN’T Rule/Notch/Pallor 3. Disc size - larger disc – larger cup – larger CD ratio 4. Compare the 2 eyes is there asymmetry >0.2? 5. Disc Haemorrhage 6.Assess the Retinal Nerve Fibre Layer
What is the Neuro-retinal rim rule?
Neuroretinal rim - Layer of neural tissue between edge of disc and edge of cup.
-look at cup disc ratio
-ISNT rule
-Look for sectoral/focal or diffuse pallor
As nerve fibres die so the disc becomes paler
Colour is a subjective judgement look at changes in vessels
What is the inferior rim in the healthy eye?
thickest
What is the temporal rim in the healthy eye?
thinnest
What is the optic disc size rule?
- Optic Disc size varies on average between racial groups - largest in Afro-Caribbean population
- Average size in Caucasians: 1.8mm
- Larger discs have larger cupping than smaller discs
What is the Optic disc asymmetry rule?
A difference in vertical cup-to-disc ratio of 0.2 or greater, should arouse suspicion
What is the Haemorrhages at the optic disc rule ?
Most commonly occur inferotemporally
More common with normal tension glaucoma
What is the Retinal nerve fibre layer changes rule ?
Best seen with green filter or in red-free photography
What is the Assessment of Visual Fields?
Visual fields are very subjective – variability, need to repeat test to account to fatigue/learning effect
There may have been considerable nerve fibre death (up to 50%) before the patient has a definite field defect
What are the triads of tests?
- IOP
- optic disc assesment
- visual field
- van heroic
What is the ocular hypertension ?
-Elevated IOP
-IOP >21 mm Hg
Normal optic discs
Normal visual fields
Open anterior chamber angle
What is the prevalence of the OHT in adult population?
2.7%- 10%
and Between 4% and 10% of individuals with OHT will eventually develop glaucoma
What is the glaucoma check list ?
D iscs size, cd Ratio, notching, haemorrhage A ngle Van Herick method F ields Early arcuate scotomas, nasal steps T onometry IOPs major risk factor
What is the primary closed angle glaucoma (PACG)?
- makes up 15% of the primary glaucomas
- RESPONSIBLE FOR approx half of all blindness caused by glaucoma - has a more devastating effect on visual impairment
What is the prevalence of PACG?
in asian countries is highest
What is the optics behind PACG?
Peripheral iris causes a significant obstruction to aqueous outflow through the trabecular meshwork
What is the mechanism of PACG?
-The major mechanism acting in acute primary angle closure is pupil block
What is pupil block ?
-Failure of physiological aqueous flow through the pupil leads to a pressure differential between the anterior and posterior chambers, with resultant anterior bowing of the iris (curving of the iris- which causes contact between the iris and the peripheral corneal endothelium thereby obstructing the outflow of aqueous).
What are the risk factors for PACG?
- Age: (>50 yrs)
- Gender: Females > Men
- Race: Asian Chinese > Indian > -African > Caucasian
- Family history
- Hypermetropia
What are the reasons for risk factors for PACG?
- Biometry - shorter anterior chamber depth- risk of angle closure
- Iris volume
- Lens Size- lens increases reducing anterior chamber depth and thereby reducing outflow of aqueous.
How do we asses the angle in PACG?
-Van Herick assessment- thickness of cornea to ratio of the thickness of the gap between the cornea and iris at the limbus
-Anterior Segment OCT- imaging the iris structure with the cornea thereby judging size of angle
Gonioscopy
How do we set up for Van Derick ?
- Set the slit lamp with high illumination and medium magnification (16x)
- Offset the illumination system by 60° temporal to the observation system, when assessing the temporal angle
- Use a thin, bright vertical beam directed at the temporal limbus with the beam perpendicular to the ocular surface
- Position the beam at the most peripheral point of the cornea that allows a clear view of the anterior chamber and peripheral iris
- Compare the thickness of the dark space (anterior chamber blue arrow) to the thickness of the corneal section (red arrow)
What can we see with the anterior segment OCT?
look at the insertion of the iris at the root of ciliary body
- take measurements
- ALLOW to quantify angle and see if any change
What is pentacam imaging ?
photography
-shows outline of cornea , lens and iris
What is gonioscopy ?
our gold standard method to asses fully the angle structures we see
Why is gonioscopy our preferred method?
using a mirror
allows to see around the corner - overcomes the total internal reflection of the cornea to allow us to directly see the trabecular meshwork structures within the angle.
What are the 2 common gonioscopy lenses used ?
A: corneal lens – no coupling fluid - typically 4 mirror- allowing to see all 4 quadrants of anterior chamber angle
- most comfortable for px
B. scleral lens– larger lens with requiring coupling fluid e.g. viscotears - typically 1 to 2 mirror (lens is slightly larger in diameter )
More magnified view with scleral lens
-see all 4 quadrants of
What is more commonly used in glaucoma work ?
scleral lens
What is the gonioscopy technique ?
Advise patient on the procedure Carry it own in a darkened room Anaesthetise the cornea Place lens onto cornea Patient looks straight ahead High magnification, a short wide beam Move the joystick to illuminate each mirror and view the angle (indirectly)
Care should be taken to avoid light falling on the pupil during the procedure
Why is it important to not let light to fall on the pupil ?
falsely open the angle by constricitng the pupil
What are the gonioscopy anatomical landmarks ?
check slide 19 for labelled diagram
Schwalbe’s Line (SL)
Non-pigmented (anterior) trabecular meshwork NP -PM
Pigmented (posterior) trabecular meshwork P-TM
Scleral Spur SS
Ciliary Body CB
Iris Processes
What is Schwalbe’s Line (SL) ?
marking point
- marks the peripheral termination of the decent membrane of the cornea and also of the anterior limit of the trabecular meshwork
- marks beginning of angle assessment
What are the bands of trabecular meshwork ?
Non-pigmented (anterior)
Pigmented (posterior)
What can happen to Pigmented (posterior) trabecular meshwork P-TM?
can change over life - after puberty
What is the Scleral Spur SS?
- white band
- extension of sclera into angle
- anterior projection of the sclera and this is the site of attachment of the longitudinal muscle of the ciliary body
What is Ciliary Body CB?
slightly pigmented
and width depends on the position of the iris insertion
What are iris processes ?
small extensions of the anterior surface of the iris which insert at the level of scleral spur
-thin web like structures - which still allow the aqueous to flow out of the eye and do not impede the outflow
How do we grade in gonioscopy ?
Shaffer grading system
-like van heroic grading
What is the shaffer angle linked to ?
linked to the angle of iris insertion into the ciliary body
What is grade 4 in shaffer. grading system?
can see down to ciliary body
-therefore angle is open and closure is not possible
What is grade 3 ?
less posterior structure
- can see down to scleral spur
- closure not possible
- angle still open
What is grade 2?
- can only see down to the pigmented TM
- narrow angle
- closure unlikely but could be possible
What is grade 1 ?
- can only see down to the non-pigmented TM
- narrow angle
- closure not inevitable risk is high.
What is grade 0 ?
- not able to see anything
- closed angle
How do we grade the angle ?
using gonioscopy lens
- use mirror to look at one quadrant
- then use different mirror
- grade all
- If the posterior trabecular meshwork is not visible for at least two quadrants (at least two quadrants with Shaffer Grade 0 or 1) this is an occludable eye.(risk of angle closure )
What are signs of peripheral anterior synechiae(PAS) ?
Adhesions between the peripheral iris and cornea
Obstruction of aqueous outflow - AS BANDS OF iris which are struck tot he corneal endothelium - obstructing outflow
What is the treatment for PACG ?
- Laser peripheral iridotomy - Nd/Yag laser creates a small hole in peripheral iris. Allows the aqueous humour to flow through and the iris tissue moves backward AWAY FROM angle - allowing aqueous to drain out of eye
- Peripheral iridoplasty – Argon laser (lower energy) to widen the anterior chamber angle by contraction of the peripheral iris away from the angle recess
- Lens extraction/cataract surgery- lens can come fatter over time and can cause angle narrowing hence closure
what are the symptoms of ACUTE PACG?
Haloes round lights Red eye Marked ocular pain Blurred vision Nausea, vomiting and feeling unwell
What are the signs of acute PACG? - APACG
- Decrease in VA – usually 6/60 to HM (WE check va)
- Sudden elevation in IOP >40 mm Hg or more
- Red eye – conjunctival hyperaemia with circumcorneal injection
- Unreactive semi-dilated pupil - vertically oval in shape
- Corneal oedema - hazy view
- Shallow anterior chamber – posterior synechiae and pupil block
What is the management of acute angle closure ?
An acute attack is an ocular emergency
Call an ambulance/arrange transport
Send patient straight to A+E
How to manage an acute attack of acute angle closure?
-Patient lies supine- try to break adhesion from iris and lens
-Medical therapy:
Acetazolamide is given intra-venously and/or orally (aqueous suppressants)
Mannitol (vitreous suppressant)
IOP lowering drops and steroid drops to the affected eye
Pilocarpine drops instilled (pupil constriction)
What happens once the treatment is done and pressure is down and view more clear ?
ophthalmologist can recommend– peripheral laser iridotomy to create an alternative pathway into the anterior chamber through the iris and break pupil block
What happens if laser surgery cannot be performed?
- Surgical “Iridectomy “
- Peripheral Iridoplasty
What is the main treatment for PACG?
Peripheral Laser Iridotomy
What do both open and closed angle glaucoma cause ? (POAG and PACG)
the same type of optic neuropathy and visual field damage
E.G shown in slide
-thinning of rim inferiorly and superior visual field defect
-so when examining px it is important to take full history - exam anterior and posterior eye in order to ascertain the classification of glaucoma the px may have or have risk of
What is the treatment for POAG?
- ALL TREATMENTS are aimed at lowering the IOP- only modifiable risk factor hence would or could use :
- Hypotensive Drops
- Laser Trabeculoplasty
- Surgery – trabeculectomy/tube or shunt
What are the drops used for ?
Reduce aqueous Production
Increase aqueous Outflow
What would the treatment for POAG. be if px does not respond to drops ?
-Surgery – trabeculectomy/tube or shunt
What are the side effects of drops ?
- allergic dermatitis - in and around the eyes
- growth of eyelashes
- darken iris and skin around the eye
What is an alternative to using eyedrops ?
- Laser Trabeculoplasty
- Surgery (SLT)–Delivery of laser to the trabecular meshwork with the aim of enhancing aqueous outflow and thereby lowering IOP.
- carried out now as a first line treatment - can reduce IOP of about 30%
- lens has 1x mag
What happens if laser and eyedrops doesnt work ?
-surgery : Trabecularotomy m, Glaucoma tube/shunt
How is trabecularoctomy carried out ?
creating a new channel underneath the conjunctiva to allow the aqueous to flow out from the anterior chamber into this new area under the conjunctiva which evaporates slowly
-it is a controlled outflow mechanism allowing the aqueous to be released from the eye thereby reducing the IOP
What is the new area formed under the conjunctiva called ?
BLEB
- appears like a blister
- underneath the superior lid visible if we ask px to look down
How is glaucoma tube or shunt carried out ?
whereby a tube or shunt is inserted into the anterior chamber and the aqueous flows out from the anterior chamber through this tube along the conjunctiva and then again is released into a BLEB blister area tucked under the eyelid
What is PACG responsible for ?
approximately half of all blindness caused by glaucoma
What is the treatment for PACG?
- Laser peripheral iridotomy - Nd/Yag laser creates a small hole in peripheral iris. Allows the aqueous humour to flow through and the iris tissue moves backward (BREAKING PUPIL block and allow aqueous to flow from posterior chamber into anterior chamber)
- Peripheral iridoplasty – Argon laser (lower energy) to widen the anterior chamber angle by contraction of the peripheral iris away from the angle recess
- Lens extraction/cataract surgery
What happens in lens extraction surgery ?
STUDY:
N=419. Cataract surgery (n=208) versus laser peripheral iridotomy (n=211)
- can see with lens in place anterior chamber is narrow, then when a lens is removed and an intraocualr lens is placed that anterior angle size increases thereby reducing the risk of angle closure
-Lens extraction showed greater efficacy and was more cost-effective than iridotomy
