Glaucoma - Referral Flashcards

1
Q

What are the components of glaucoma referral?

A
  • Hx
  • IOP
  • Central Corneal Thickness
  • Anterior chamber assessment
  • Visual Fields
  • Disc Assessment
  • Imaging
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2
Q

Describe history in glaucoma and what to enquire about?

A
  • Age and ethnic origin
    o Pxs of Afro-Caribbean decent are at more risk of developing POAG
    o Pxs of South East Asian decent are at more risk of developing PCAG
  • Previous hx of OHT or glaucoma
  • Previous OH:
    o Uveitis
    o Pseudoexfoliation
    o Pigment dispersion
    o Myopia - >6D more at risk
  • General Health:
    o Diabetes
    o High blood pressure
    o Peripheral vascular disease – risk of POAG
    o Migraine – risk of NTG
    o Raynauds phenomenon – risk of NTG
    o Sleep apnoea – risk of NTG
  • Previous medications:
    o Steroid use
  • Family history of glaucoma -> who? V important if 1st degree relative – if family member was very young when diagnosed and was very severe then higher risk for px
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3
Q

What are the risk factors of POAG?

A

Age – prevalence increases w/ every decade
Black ethnicity – relative risk for developing POAG
Diabetes – slightly increased risk but not as strong a link – same with hypertension & peripheral vascular disease

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4
Q

What are the risk factors of ACG?

A

Prevalence lower of ACG – does increase with age
Increase risk of ACG in females
Hyperopic pxs often also more at risk
South East Asian ethnicity – more anterior positioned lens and shallower anterior chamber angle – increased risk of ACG

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5
Q

Describe IOP and glaucoma and when to consider referral?

A
  • Measure using applanation tonometry – Goldmann is gold standard
  • Protocol in place to ensure regular calibration – once a month
  • Establish a baseline – using Goldmann
    o Required for all suspect OHT and suspect glaucoma
  • Minimum of 2 readings on a single occasion
  • Record time, reading & instrument
  • Should consider for referral if:
    o IOP > 25mmHg irrespective of CCT
    o IOP 21-25 AND CCT <555µm AND aged ≤65
  • Monitor in community if IOP <26 and CCT ≥555µm & no signs of glaucoma
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6
Q

Describe CCT and glaucoma?

A
  • Important independent risk factor for glaucoma
  • At increased risk or glaucoma if CCT <555µm
  • Measured using pachymeter
  • Record CCT mean, SD and pachymeter used
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7
Q

When should you refer based on IOP and CCT?

A
  • Irrespective of other signs of glaucoma SIGN guidelines recommend referral when:
    o IOP > 25mmHg irrespective of CCT
    o IOP 21-25 AND CCT <555µm AND aged ≤65
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8
Q

Describe anterior chamber assessment?

A
  • Van Herick’s or Gonioscopy acceptable when referring
    o Refer irrespective of other signs refer if:
     Van Hericks technique shows a peripheral anterior chamber angle which is less than a quarter of corneal width
  • Technically under SIGN grade 2 on VH should also be referred but in west of Scotland this isn’t always feasible as many older hyperopic patient with patent angles will be grade 2 - up to your clinical judgement, consider gonio on grade 2’s
    o Certainly refer grade 1/0 for prophylactic PI’s
  • Van Herick’s: take measurement from as far out as possible, just where beam splits
    o Left Pic: grade 2 – referrable under SIGN guidelines
    o Right pic: grade 4 – open angle
  • Gonioscopy:
    o Refer irrespective of other signs refer if:
     Gonioscopy shows 270° or more of the angle where posterior pigmented trabecular meshwork is not visible – this means that more than ¾ of angle is functioning normally
    o Only for use when practitioner is confident in their abilities
    o Gonioscopy only way to see abnormalities in the angle such as peripheral anterior synechaie and only way to tell for sure if the angle is open by visualising the posterior pigmented trab meshwork
  • Referral for narrow angles should not be based on OCT
    o Low specificity for identifying narrow angles
    o Gonioscopy only way to see abnormalities in the angle such as peripheral anterior synechaie
    o No standardised anterior chamber assessment protocol for OCT
    o Variability between examiners when identifying scleral spur
    o OCT can be used as an adjunct to examine angle configuration
     Plateau iris
     Angle recession
     Pupil block
  • Check anterior chamber angle for:
    o Pseudoexfoliation – present on anterior lens capsule, seen when dilated
    o Pigment Dispersion – look for Krukenberg spindle
     Look for iris transillumination – best looked before dilation
    o Iridotomy – laser procedure to create another route to help aqueous escape more freely
    o All require lifelong monitoring as they are at increased risk of developing glaucoma – monitoring should include disc assessment, IOP and visual fields
     These pxs should not leave more than 2 yrs between eye examinations
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9
Q

When should you refer based on anterior chamber angle?

A
  • Irrespective of other signs of glaucoma SIGN guidelines recommend referral when:
    o Risk of angle closure:
     Using Van Herick’s technique, peripheral angle width of less than a quarter of corneal thickness
     using Gonioscopy, when posterior trab meshwork is not visible for ≥270°
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10
Q

Describe visual fields in glaucoma?

A
  • SIGN recommendation:
    o Minimum of 2 VF tests with consistent findings is recommended before referral to secondary eyecare services. One test may suffice is result is unequivocal (if px had not have eye exam in 10yrs and signs show severe glaucoma then can refer without repeating)
  • Ideally should be same VF instrument in primary & secondary care – Humphrey Field Analyser
  • Frequency doubling perimetry may also be used as an alternative to standard automated perimetry
  • No recommendations in SIGN about level of loss at which referral should be considered - if repeatable and you judge it to be clinically appropriate then refer - cluster of 3 or more points on the PSD with a probability of 99% or more might be a reasonable time to refer
  • Test should be 24-2 SITA Fast
  • Important things to consider:
    o If there is a defect – is it changing?
     Progression could be glaucoma
     Stable could be defect due to tilted disc or another longstanding defect
     Has mean defect changed by more than 2dB?
    o Does VF defect match appearance of disc?
     If a superior visual field defect is present in RE is there also loss of inferior neuroretinal rim in RE?
     In glaucoma shouldn’t expect field defects to cross the midline
    o Px reliability:
     If poor reliability on repeated occasions then VFs are less helpful for diagnosis & disc assessment & glaucoma becomes more important tools
     Make use of VF indices:
  • 20% false positives
  • 20% false negatives
  • Enlargement of blind spot is not a good glaucomatous sign, most common glaucomatous defects in order paracentral, arcuate, nasal step, temporal wedge
    o Usually in glaucoma should expect to a glaucomatous defect to have a cluster of more than 3 points before considering referral
    Typical Patterns:
    o A typical early paracentral defect is often the first VF defect – often seen in superior quadrant
     This superior paracentral defect tends to be a small cluster of points in the paracentral area
    o Arcuate defect may then become visible
    o The more established the glaucoma becomes, paracentral defects move into becoming arcuate defects
    o Pxs may also present with a nasal step or with a temporal wedge – slightly more uncommon
    o Unless there is extreme glaucomatous loss affecting both superior & inferior NRR – should find that defect you are finding respects the midline because of the distribution of the nerve fibres
     If defect is not respecting the midline, question if it is neurological loss or some other retinal condition that is causing VF loss
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11
Q

Describe disc assessment in glaucoma?

A
  • Irrespective of IOP, pxs with one or more of following findings should be referred to secondary eye care services
    o Pxs with optic disc haemorrhage should be referred irrespective of other signs of glaucoma  almost pathognomonic
    o Pxs with cup to disc asymmetry – difference in C:D of 0.2 or greater consider referral?
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12
Q

Describe imaging in glaucoma?

A
  • Fundus photos – if have baseline fundus photos as well as those taking at time of referral
  • OCT Scan
  • GDx
  • If available add to referral
  • Serial analysis to assess change – from pic, superior VF defect due to inferior thinning
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13
Q

When should you monitor the disc more closely?

A
  • At risk groups:
    o PDS - ~15% in 15yrs or 50% develop glaucoma in 4yr period – definitely high risk
    o Pseudoexfoliation – high risk of conversion to glaucoma 30-50% develop glaucoma
    o Myopic discs – increased risk of glaucoma
    o Tilted discs – not increased risk but VF can mimic glaucoma so need to monitor to ensure no progression
    o Optic disc drusen – if all else normal can monitor – if VF defect or OHT refer to secondary care as increased risk of progressive glaucoma
    o Pxs with hx of primary angle closure who have had an iridotomy
    o FHG – at least every 2 years if no other risk factors – at least annually if other risk factors present
    o OHT – record baseline disc appearance, VF and IOP – review every two years
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14
Q

When should you refer for glaucoma?

A
  • Irrespective of IOP, pxs with one or more of following findings should be referred to secondary eyecare services
    o Optic disc signs consistent with glaucoma in either eye
    o A reproducible VF defect consistent with glaucoma
    o Risk of angle closure:
     Using Van Herick’s technique, a peripheral angle width of less than a quarter of the corneal thickness
     Using Gonioscopy, when posterior trab meshwork is not visible for ≥270°
  • IOP is >26mmHg – irrespective of CCT
  • IOP 21-26, Central Corneal Thickness is <555µm & px is aged under 65
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15
Q

Which pxs would be discharged back to community practice?

A
  • Pxs with untreated ocular hypertension where IOP is < 26mmHg & ocular examination is otherwise normal
  • Pxs with untreated ocular hypertension where IOP is >25mmHg, ocular examination is otherwise normal & a low lifetime risk of glaucomatous visual disability
  • Treated ocular hypertension where re-referral criteria are documented
  • Pxs who have had an iridotomy & have open angle, are not on topical medication & have no evidence of glaucoma
  • Pxs may be reviewed by named accredited optometrist at discretion of a consultant ophthalmologist
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16
Q

What are the common mistakes in glaucoma referral?

A
  • Poor description of reason for referral – clearly state diagnosis and sxs (if any)
  • No list of the patients risk factors
    o Ethnicity, age, ocular hx – uveitis before for e.g.?, family hx
  • Poor description of the disc
  • No/poor description of the angle
  • Not repeating pressures – particularly if bringing px back to do VFs
  • Not stating which instrument was used  for pachymetry, for IOP and for visual fields
  • VF not enclosed
  • VF not repeated
  • In advanced disease delaying referral to repeat procedures
    Depending on your presentation – may be difference between px being seen quickly or not
    Glaucoma is monitoring a progressive disease – so more evidence you can give consultant before px reaches their chair the more likely they are to treat that px in a timely manner
17
Q

Describe disc assessment and why to use slit lamp biomicroscopy?

A
  • Disc Assessment using slit lamp biomicropscopy i.e. Volk lens or equivalent
  • Why use slit lamp biomicroscopy?
    o Better field of view
    o Improved illumination – better contrast when looking at disc
    o Stereoscopic view of the fundus
    o Easier to navigate the fundus
    o Image size less affected by refractive error
    o Better view few partially opaque media e.g. cataract
    o AND can measure disc size!
  • If you can’t see properly consider dilation – e.g. if px is 55yo and you suspect glaucoma – important to get stereoscopic view and hard to get through small pupils
18
Q

What is important to assess in the disc in glaucoma?

A
  • Need to assess disc size
  • Pay attention to where the disc rim is narrowest
  • Scrutinise where the neuroretinal rim ends around the whole disc
  • Base your judgement of where edge of the cup is on bending of the vessels – NOT ON PALLOR
    o Look for vessels emerging and bending from cup – that’s where NRR is
  • Look for glaucomatous disc features (see CO Tri A notes 2022)
  • Familiarise yourself with the DDLS scale and SIGN guidelines Narrowest Rim to disc ratio
  • Need to consider which part of the neuroretinal rim is narrowest
    o Do not refer based purely on violation of the ISNT rule
  • Always refer optic disc retinal nerve fibre layer haemorrhages irrespective of other signs of glaucoma
  • Refer based on Narrowest Rim to Disc Ratio – based on Disc Damage Likelihood Scale (DDLS)
19
Q

What is the advice for the ISNT rule in glaucoma?

A
  • Whilst the INST rule is followed by most healthy discs – most discs which violate the ISNT rule are NOT glaucomatous
  • One study showed that the sensitivity of the ISNT rule for detecting glaucoma is good (95%)
    o However, the Specificity is poor 12%
  • As a result the SIGN guidelines state referral for assessment of glaucoma should NOT be made solely on violation of the ISNT rule
20
Q

Describe the disc assessment and referral for glaucoma?

A
  • Irrespective of intraocular pressure, patients with one or more of the following findings should be referred to secondary eye care services
  • Patients with an optic disc haemorrhage should be referred irrespective of other signs of glaucoma
  • Patients with cup to disc asymmetry – (difference in C:D of 0.2 or greater consider referral?)
  • Recently the DDLS has come to prominence as referral based on disc signs for glaucoma is Scotland should be made with reference to the DDLS.
  • The grading on the DDLS has been shown to have:
    o good repeatability
    o a strong correlation with glaucomatous visual field damage
    o better specificity than cup to disc for detecting glaucomatous disc damage – less false +ve referrals
    Need to measure disc size so know what real cup:disc is – DDLS accounts for this so is VITAL
21
Q

What are the 3 steps to disc assessment under SIGN guidelines?

A
  1. Measure Disc Size
  2. Assess width of Neuroretinal rim
  3. Grade using DDLS Scale
22
Q

Describe disc size measurements?

A
  • Difficult to do accurately using a photo
  • Cannot be done using ophthalmoscopy
  • Use a volk lens in combination with a slit lamp which can record the height of the slit
  • Beware of peripapillary atrophy and myopic crescents when estimating disc size – exclude that from disc size measurement
  • Use graticule on SL – Reduce the width of the beam to 1-2mm
  • Reduce the height of the beam to match the size of the disc and read of the value from the slit lamp height graticule
  • Apply lens correction factor to the value obtained from the slit lamp height graticule
  • Size:
    o Small Disc Size – less than 1.5mm
    o Medium Disc Size – 1.5-2.0mm
    o Large Disc Size – greater than 2.0mm
  • When using a 66D lens the graticule reading will be 1.5-2.0mm for a medium disc
  • When using a 78D lens the graticule reading will be 1.25-1.75mm for a medium disc
  • When using a 90D lens the graticule reading will be 1.1-1.5mm for a medium disc – if more than 1.5 is large disc, if less than 1.1 is small disc
23
Q

What are the considerations when choosing a lens in disc size measurement?

A
  • What part of the fundus are you most interested in in THIS patient?
  • Macula or Disc – higher magnification and lower field of view
    o 60D
    o 66D
     Correction factor is 1x so can just read beam height from graticule and equivalent to disc height
    o 78D
  • Peripheral fundus – lower magnification and larger field of view –
    o 90D
    o Superfield
  • Multiply reading by number listed depending on lens used
24
Q

Describe assess width of NRR: narrowest rim to disc ratio

A
  • Identify narrowest rim ratio
  • OR estimate degrees of absent rim if rim is completely lost
  • Ensure that is it the bending of the vessels you are using to judge the NRR and not the pallor
    Once know height of disc and R:D ratio can then decide if px needs referred or not
    Smaller disc – expect wider NRR as same number of nerve fibres in smaller space
25
Q

What are the limitations of DDLS?

A

No grading scale works well with these types of discs – this is where VFs become very important - get better at this the more you assess discs
* DDLS helps monitor focal loss
* However:
o Poorer at monitoring diffuse NRR loss
o Doesn’t work well with unusual discs – neither does C:D
o Monitors thinnest area of NRR but if focal loss is occurring in another location the DDLS grade may not change – pay attention to disc as a whole – narrowest area in both discs in graphic is 1o’clock/2o’clock position but has been progression occurred – THEREFORE record C:D and if there is multiple areas of NRR thinning then record that too

26
Q

Describe the Disc Damage Likelihood Scale (DDLS)?

A

Refer grade 4 or above
If the NRR size is 0.2 for example to grade under DDLS you simply add 1 (for a small disc) or take one away from the grade (for a large disc) so you only really need to know the middle column
Remember the details for a medium disc then just add 1 to the grading for small disc and take 1 away from grading for large disc

27
Q

Describe what you should include in a disc drawing?

A

scrutinise the features of disc in front of you
* Represent:
o NRR thickness & narrowest point of NRR thickness
o Blood vessel pathway as they emerge from the cup – as they travel superiorly & inferiorly
o Any unusual/glaucomatous feature
 Need to draw edge of disc/cup accurately as well as drawing any PPA – also draw edges of NRR and where it is narrowest
* Disc Drawing:
o Narrowest disc rim to disc ratio
o Cup to disc ratio
o Disc size - & converted disc size once applied correction factor
o Lens used
o Any pertinent features of disc – e.g. thinning in particular area
* Disc Photograph:
o Especially important at baseline (1st visit)
o Also when suspicious disc
o Over age 60 at each visit – due to GOS contract in Scotland
o Send disc photos with glaucoma referral – recent image and baseline image v useful