Slit lamp technique in glaucoma
narrow angle glaucoma ..how to examine
By using the same examination technique
each time, you are less likely to forget what to look for. An idea
(Prof Peter Shah)
- look for stromal atrophy
- glaucomaflecken/central depth
- corneal oedema
- Van Herrick test (diagram)
- convex iris configuration
The normal lens/axial length ratio
=15%. Such eyes rarely develop acute glaucoma or need laser PIs.
the lens/axial length ratio >20%, and gonioscopy
shows narrow angles, there may be a risk and such a patient may need
laser. An axial length measurement (A scan)
will give these figures.
|anterior corneal curve
|anterior chamber depth (ACD)
|anterior lens curve
lens thickness /
- Check history, family
history, refraction (high hypermetropia contributes).
- Axial length
- Anterior chamber depth < 2.2mm.
- Lens thickness >4.0mm.
- Lens thickness/axial length ratio LT/AL >
20% is very suspect.
- if there is pigment in the superior angle
- earlier if there is a family history of angle
- earlier if there is diabetes require dilating
- patient choice if clinically borderline
- use the Van
Herrick test (diagram) and look at the
- the pressure rise may be due to pupil block,
aqueous mis-direction, or ITC (irido-trabeular contact)
- measure the horizontal corneal diameter
with a plastic ruler
- average 12mm
- megacornea 13mm
- microcornea <11mm
- suspect angle closure attacks with iris atrophy, pigmentation
on trabecular meshwork,
- always carry our gonioscopy in the DARK as the angle will be
Use the view below to identify Schwalbe's line.
- very dim room illumination
- slit lamp angle at 10 degrees...the first notch
- very narrow beam
- short beam....angle opens if pupil goes small
(if light goes in pupil)
- look for the inverted 'Y' pattern as below...Schwalbe's line
is at the join
- don't press, assess in primary position, don't tilt to start
Grading gonioscopy appearance ..does the patient
need a PI
Angle becomes narrower over the years in some people
- anda...anatomically narrow drainage angle
(ANDA: can see pigmented trabecular meshwork all round, safe)
- 2 years later progresses in 33%
ITC: iridotrabecular contact: cannot see pigmented angle in places
- 2 years later progresses in 33%
PAS...peripheral anterior synechiae
- 2 years later...
PAC: primary angle closure= ITC + IOP (high pressure) + PAS +
- ANDA...patient can be discharged
- ITC <180 degrees, no need to watch carefully (yearly
exam at optometrist)
- ITC >180 degrees, generally needs a PI
- PAC/PACG needs PI
- Concerning when to carry out laser PI: make decisions in pirmary position
Documenting gonioscopy appearance
Abbreviations, for example (in the direction of the mirror..12
o'clock on the drawing is 12
o'clock in the patient's eye)
- ITC: iridotrabecular contact
- llNP ....see non-pigmented trabecular meshwork only
- llP ....see pigmented trabecular meshwork
drawing gonisocopy appearance
- Once the ITC (iridotrabecular contact) exceeds 180 degrees, surgery
is indicated (laser iridotomies [PIs] or lens removal [phaco or 'cataract
- If, despite the PIs, the ITC (iridotrabecular contact) exceeds
180 degrees, the laser iridoplasty as below may be needed.
- If, despite the PIs & iridoplasty, the ITC (iridotrabecular
contact) exceeds 180 degrees, phaco may be needed.
- If the ITC reduces to, 180 degrees, the pressure
- may be normal, and regular checks over years are needed until
it is clear the angle is not starring to close again
- the pressure may be slightly high, and Xalatan drops or equivalent
may control the pressure
- If the pressure remains high, trabeculectomies will be needed.
Usually phaco is carried out first.
- If the angle closure is secondary to another condition (eg inflamation)
and recent, gonioviscolysis may help, possibly with iridectomy.
- patients with narrow angles develop PAS and high IOP at a rate
of ~20%/year, as in this diagram below:
Other slit lamp signs
- anterior chamber depth, centrally
- anterior chamber depth, peripherally (Van Herrick's test)
- stromal atrophy
- convex iris configuration
How to laser
PIs (Peripheral iridotomy)
- Explain, consent, etc
- pre-laser ..pilocarpine 2%; this makes iris more taught.
- 1% apraclonidine; dexamethasone minims>
- apraclonidine (iopidine 1%) reduces iris blood flow and helps laser
penetration at lower power: use 1 hour before and again at time of
laser Yag laser
- laser 11-1 o'clock
- 12 o'clock may be obstructed with bubbles...best 11.30 or 12.30
- try to avoid lasering where not covered with eyelid...also avoid
upper lid tear film meniscus
- if laser is not under the eyelid...patients will get ghosting or
- similarly lasering under the upper lid meniscus makes visual symptoms
of polyopia etc more likely ...these can be very troublesome.
- stop aspirin and gingo a few days before..as these increase risk
of bleeding (gingo biloba...leave a 10 day gap without)
- warfarin...ideally this would be stopped...but as it is often important
to prevent emboli, proceed with care (but check not over-anticoagulated)
- both eyes separately (this is controversial, I personally carry
out both eyes if low risk in same session)
- post-laser inflammation is related to iris pigmentation
- both eyes same day JG 17
Position of PI
position PI between 11 and 1 o'clock, peripheral iris, otherwise problems develop
Acute attack and PIs
PIs if there is advanced glaucoma
- expect a pressure rise
- add oral diamox for several days
- take pressure 1 hour after
Observations during laser
- iris should go flatter...assess 1 hour later
- procedure is more problematic if there is a corneal arcus
- if cannot get through..consider surgical PI
- Afro-Caribbeans ..higher power...eg 9mx 2 pulses (versus normal
power 6 x 2mj)
- Yag laser setting...1 pulses, about 6 mj, use an iridotomy contact lens eg
Wise 55 dioptre lens
- when lasering . iridotomy is patent when there is a rush of aqueous
and pigment, like a mushroom of pigment
- if you think you are through but are not sure proceed with 1 or
2 extra shots until a GOOD PLUME OF AQUEOUS seen
- typically 2-4 shots will get through with this good plume of aqueous
Notes related to iridectomy and angle closure
Immediately after laser
- dexamethasone (such as Maxidex) 2 hourly drops for 4 days reducing
to 4 times a day for 2 weeks post-laser (if lots of inflammation expected,
start hourly for a day, then reduce.
- extra diamox if disc is cupped or pressure rise expected, perhaps
froben if uveitis present
- review 1-2 weeks, always repeat gonioscopy to check angle has
opened. If not consider plateau iris.
How to laser
a thick iris: pre-treat dark irides
Usually Yag laser above works. Occasionally the iris is so thick surgery is needed (very unusual in the UK). However, some irisis are very thick, but can be lasered by carrying out argon laser first.
a ring or argon laser (red) is carried out before the Yag (white)
- before the YAG laser
- using the PI lens (usually a 'Wise' lens)
- using 50µ 0.1 second light burns applied to the surface of the iris (clearly visible...adjust the power so there is a visible burn)
- apply a ring of argon laser, and also laser the centre
- then change to the Yag laser and laser in the usual way.
- effectively the argon laser stretches the iris making iteasier for the Yag laser to perforate.
- this technique works for most thick irisis if the Yag laser itself does not work straight away.
Glare after PIs
If patient does get too
much glare in the weeks/months after the laser
- often this could have been prevented by lasering under the
- polarised lenses will reduce glare considerably
- corneal tattoo may help.
Topiramate and other drugs
This is a new treatment for severe epilepsy and migraine.
Unfortunately it may cause angle closure glaucoma, see.
Treatment is DIFFERENT FROM ordinary ACUTE GLAUCOMA .
- treatment with
- cyclopentolate, dilate pupil, steroids, probably NO diamox
- try and detect suprachoroidal fluid (ultrasound or OCT)
- NO MIOTICS
- this treatment works over 2-3 days..if not, some alternative
treatment is needed.
- Sympathomimetics, anticholinergics (such as tricyclic antidepressants),
anthistamines, and idiosyncratic (such as Topiramate). Stress,
the head down posture, low lighting, extreme climates, may precipitate
- Older patients, women will get more attacks. Also, Asian
women may be more prone.
Uveal Effusion in
Uveal effusion was found in 11 of 70 eyes with PACG (Kumar
in Chinese families
- shorter AL
- shorter ACDs
- thicker lenses than those
without occludable angles.
- thicker iris BJO 2010
- In multivariate analysis, increasing
age, decreasing AL, decreasing ACD, and nuclear cataract were significant
predictors of early AD. The presence of nuclear cataract per se
should raise clinical suspicion of the possibility of AD in this
Symptoms of angle closure glaucoma
to tasks such as reading
- when you get the haloes, are the eyes red?
- how does the eye feel when it is red? (an ache suggests higher
laser for iridoplasty for platueau iris
- see plateau
- use for plateau iris only, not simply angle closure
- Argon laser
- Abraham lens
- 0.2 seconds
- 2 quadrants
- 10 applicatons/quadrant
- Lim 93
This is becoming increasingly noticeable
as anterior segment imaging (OCT or ultrasound) becomes available. A
plateau iris may cause angle obstruction (and rise in pressure),
particularly in ther dark. This is a diagam of the OCT appearance.
- Lens extraction hoffer q generally best
- Anterior chamber shallow, use blade, Lots of uveitis and cmo,
- Eagle trial semiacute clear lens phaco helps... surgeon has to be familiar with surgery shallow eyes
Treatment of attack of acute glaucoma
- 1/3 angles don't open with PIs, and iop stays high
- Iridoplasty may open angle but iop may stay high
Gonio in fellow eye, may not be able to goinio attack eye
- Biometry later
- if cloaure secondary..cycloplegics..post vitrectomy, white or wobbly lens, uveitis, rg, normal size eye,
- once iop reduced iridotomy both or other eye ..fellow eye must be treated before home ,pred fort 2 hourly, and iopidine and stop both 2d before next clinic, cannot leave hospital before both treated if possible
- Refractory attack:
Use needle paracenteses if pressure does not come down, insulin needle, remove plunger, indent slightly, .1ml, then yag pi so
- Iridoplasty 180 degrees, just have to laser where not iris cornea contact, start mid periphery and spiral out, high power through hazy cornea, or if that does not work >>>cyclodiode>>may be lensectomy
- Cyclodiode very helpful
- Diamox 500mg iv, or oral ..iv 30 mins, oral 2 hours
- Iop, pilo, pred fort, timolol, stat, lie flat,
- no iopidine if heart problems
- 60 minutes after reassess, laser iridoplasty
- Allergy may be present
- sickle disease (safe if trait, not with sickle disease),
- Small eye
? Uveal effusion
- Pressure can be high,normal,low, fluctuate, ac depth changes
- develops Over hours
- Shallow ac ..think,short eye
- Reduce aqueous
- Atropine and phenylephrine, BOTH,
Iv diamox etc,
- Yag laser hyaloidotomy through patient pi, or use cyclodiode
- Vitrectomy phaco ..vit, phaco, lense, complete vitrectomy
- Nanophthalmos short eye
- Uveal effusion...b scan any length