Laser Treatment for diabetic retinopathy for professionals
These are giving better resutls than laser for both diabetic maculopathy and proliferative retinopathy!
Laser ..types...Pascal, subthreshold
The commonest laser is Argon Green, wavelength 530nm, but
other wavelengths can be used. Other types of light were
used before laser was introduced. There are two new types of laser that seem very helpful. First, the PASCAL
laser, which can apply several hundred burns quickly, and seems ideal BJO
2010. It is also much less painful BJO
2010. Pascal macular
grids. Pascal, fewer sessions for PRP BJO 2011 Nerve fibre Retina 3011.
Secondly, a subthreshold diode
laser with a longer wavelength may be best for both macular and PRP laser.
There are an increasing number of reports that subthreshold laser is safer
for macular oedema. The benefit is from the lower power used, not the different wavelength difference.
Burns of shorter duration certainly produce less retinal damage are are probably
more effective (2010),
but need more burns. Less damage subthreshold Retina 2012. Subthreshld laser, even PRP, is recommended for milder retinopathy, but if the retinopathy is severe heavier laser burns will be needed.
Subthreshold is safe Retina14. Equally effective Eye15 Eye10. Subthreshold PRP laser is unllikely to cause macular oedema or severe epiretinal embrane formation. Heavier burns (greyish white), which are needed for more aggressive proliferation, cause macular oedema in 20% of eyes.
Inadequate diabetic control (HbA1c & BP)
It is absolutely vital that diabetic control is addressed. If a patient
is under the care of an very experienced diabetes specialist nurse/doctor,
there may be no improvements that can be made. But almost by definition,
patients must have had control that is less than perfect, as it is rare with good control to develop
retinopathy. These are the standard targets (HbA1c,
blood pressure (BP), exercise, healthy diet, exercise, good mental health
Why is HbA1c/BP control poor?
Certain clinical situations are common.
For good results, as far as possible these issues have to be addressed.
- patients have too much else going on their lives, , who are struggling with day to day problems, so they have not
bothered with diabetic control (this may be very busy at work, someone
else ill at home, etc)
- patients with inadequate diabetes care support from professionals
- patients whose professionals are ill themselves, with locums filling
- type 2 diabetes diagnosed late..complications
are present at time of diagnosis
- patients with psychological
problems, such as anxiety or depression or schizophrenia
- patients moving from one practice to another (who are not really
- disorganised diabetes care
- patients who have not accepted their
diabetes, and do not test glucose levels and adjust insulin
- eating disorders/omitting
insulin to lose weight
- patients with very poor education
Ideas that may help to improve control
- ASAP liaison with the diabetic team..whoever is providing the care
- For all patients using multiple insulin injectoins and wo test their glucose regularly, the new glucose sensor is highly recommended here.
- if HbA1c is high, a gradual drop may be best (current advice, limited evidence,
this may change). Hovwever, it is more practical just to lower it the easiest ppossible way, accepting it may drop quicker than ideal for the eyes.
- 3-12 months, diabetes
- such as DAFNE for
type 1 patients,
- XPERT for
type 2 patients,
- DESMOND for
newly diagnosed type 2.
- 3-6 months after starting laser, a
modern insulin regime
- if the BP is
higher than target, increase medication every 2-4 weeks until controlled
- psychologist/psychiatrist if problems severe
help best; low self-esteem plays a significant role
patients their retinal photos (or another very similar)
- whilst people may not be receptive certain times, at other times,
perhaps a year or two later, they may be
- address smoking
steps for success
- patients need baby steps: perhaps 1-2 weekly visit to their diabetes
doctor/nurse, making small changes each visit. This may need to be
carried out over 6-12 months.
- Use stories to illustrate ways forward
- when a problem is found (e.g. poor control, smoking) compliance
is likely to be ~3
x higher if an appointment is made there and then,
and give the appointment to the patient.
Often this is not possible,
but merely mentioning the problem is much less effective. Thus we
should be making appointments with the diabetes specialist nurse or
the Stop Smoking clinic during our retinopathy consultation, is we
want good compliance.
Planning treatment...taking account of diabetic control
We need to consider the rate of progression of retinopathy. With perfect
control, there should be no/very little retinopathy progression. We can
use UKPDS and DCCT data
(and other papers) to calculate progression rate as opposite. But progression
rate may change:
- if the HbA1c drops 3%, the
retinopathy will progress much more quickly. This applies to the
3-4 years after starting good diabetic control, but after this
time progression rate will reduce considerably.
- Pregnancy tends to lead to more rapid
- sudden increases in blood
pressure (usually due to decreased renal function), may also
lead to more rapid progression.
- on the other hand, a type 1 patient diabetic for 40 years with
reasonable control, should have more slowly progressive retinopathy
- anyone with good BP/HbA1c for 3-4 years: progression should be
very slow and most patients with 4y of good glucose control, low
BP, and not smoking will not have active retinopathy. It
takes 3-4 years of such good control to stabilise the condition...such
patients can be discharged from the laser clinic and just monitored
by screening programs
- a certain degree of retinopathy may have developed in a patient
- a long duration of diabetes (e.g. 40y) (will progress slowly)
- with newly diagnosed diabetes (and recently high HbA1c) (will
progress rapidly as HbA1c drops)
- poor control for a few years
- poor control for years, even is this was may years ago: 'legacy' effect
- good control...but was poor in the last 3 years
- For the same degree of retinopathy, progression rates may be
very different, and laser should be increased in eyes expected
to deteriorate rapidly, as in the table below.
- Shorter pulses produce less retinal damage, Muqit
Progression rates of microvascular disease
Eyes, kidneys, neuropathy etc
- 1% HbA1c rise= ~37%
blood pressure >115mmHg systolic =1.1%
- Smoking...each cigarette = ~20% increase
- sleep apnoea plays a significant role
Progression rate varies despite patients having similar retinopathy
appearance at any one time
|40y reasonable control
| newly diagnosed
diabetes now well controlled HbA1c was 10, now 7
for a few years (HbA1c 9%)
was poor in the last 3 years
was poor in the last 3 years..started insulin recently
in last 3-4 years HbA1c 7%, BP 130/75, non-smoker
control before conception)
||may be rapid
control before conception and control better now
the amount of laser: increase if the retinopathy is progressing rapidly
(Good HbA1c control is essential in the long term, but may increase the
progression rate for 1-3 years. Retinopathy will generally stop progressing
completely in non-smokers after 3-4 years of good control.)
Planning PRP laser (peripheral laser photocoagulation)
PRP laser treatment was the main treatment for proliferative retinopathy (new vessels) or moderately severe pre-proliferative retinopathy, although increasingly anti-VEGF injections are taking over.
It helps to think ahead....how much treatment is needed in the short
(and long) term. Rather than carry out 1200 burns or anti-VEGF and see the result,
best results are likely if the treatment is carried
out early. Some patients need a lot of laser or anti-VEGF, some a little. This summarised in this paper, Eye 2011
"Following top-up PRP treatment, regression rates varied according to severity: 75% for mild PDR (n=6), 67% for moderate PDR (n=14), and 43% in severe PDR (n=3).
is maximum laser?
In descriptions on this
page, 5000 large or 18000 smaller lighter burns are given as the estimate for treatment of most
of the peripheral retina (with laser carried out in multiple sessions as on this page). But this is a very approximate figure..some
patients may have 5000 burns and a lot of space is left (and
they may need more laser), some may have no space after fewer. Please take this into account when interpreting the examples
These figures are for the transequator lens, the easiest to
use for PRP laser. Each lens has different magnification (Scanlon,
p121). The Mainster 165 is reported to be the ideal lens now.
To achieve complete disease regression, mild PDR required a mean of 2187 PRP burns and 264 mm ablation area, moderate PDR required 3998 PRP burns and area 456 mm), and severe PDR needed 6924 PRP laser burns (836 mm;).
Multiple 20-ms PRP treatments applied over time does not adversely affect visual outcomes, with favourable PDR regression rates and minimal laser burn expansion over 18 months. The average laser dosimetry and retinal ablation areas to achieve complete regression increased significantly with worsening PDR." (DK now uses a lot more much smaller lighter burns. )
In an excellent review, essential reading for professionals, Eye 2011, the amount of laser can be calculated. The study was based on patients with an HbA1c current and recent <10%. Higher HbA1c patients may be expected to need a lot more laser. The paper describes laser in terms of retinal area that needs treatment, but this difficult to judge clinically. However, for significant nvd/e, most of the peripheral retina needs laser.
For the <10% HbA1c patients, in the Manchester study,
- early mild proliferation...2000 pascal burns 1-2 session, subthreshold
- moderate nv...4000 burns in 4 sessions, subthreshold
- more aggressive nv...6000 burns in ~6 sessions, moderate burns but heavier than subhreshold, mild grey-white. Theses heavier burns (greyish white) cause macular oedema in 20% of eyes.
But remember, patients in higher risk groups e.g. recent HbA1c> 10, smokers will need relatively more. patients with very good control as discussed below need less.
Once there are retinal complications, such as haemorrhage and traciton , vitrectomy is more likely to be needed Retina14.
Consider certain clinical situations
A patient with
very active new vessels...generally needs ~15000 smaller lighter burns/eye, soon…1st
3 sessions in 1st week. Laser is needed quickly as it is very likely
there will be a vitreous haemorrhage soon. (3000/eye/session, both eyes same session). Probably needs 18000 burns/eye (much
of peripheral retinal lasered) over the nexct 2-4 weeks.
Examine monthly after this. Even
this may not be enough and new vessels may continue to grow. If so,
we believe anti-VEGF may be ideal for such patients. At present we
laser 3-5 sessions and examine the result, but it is probably best
to try and calculate how much is needed at the onset, and carry
Vitreous haemorrhage with new
vessels..similar treatment to patient 1. Vitrectomy if you cannot
laser through the haemorrhage (vitrectomy with endo laser).
Disc new vessels, poor control.
Retinopathy will progress reasonably quickly, laser needed over ~4weeks..similar
treatment to patient 1.
Disc new vessels, poor control.
But will start to improve diabetic control. Retinopathy will progress
even quicker with the improving control, laser needed over ~4weeks,
similar treatment to patient 1. Good control helps in the long term,
sometimes not in the short term.
Disc new vessels, good control
for the last 4 years. Retinopathy will progress slower, may manage
with 10000 burns/eye, over ~8weeks. Examine in 2-4 months to
see benefit, may need more laser over next 2 years.
poor control. But will start to improve diabetic control. Retinopathy
will progress quickly, may manage with 12000 burns/eye, over ~8weeks. Examine
in 2-4 months to see benefit, may need more laser over next 2 years.
Difficult to predict outcome. Many type 2 patients starting insulin are in this position.
Best to laser early in my opinion.
poor control. Won't improve HbA1c, blood pressure 130 systolic.
Difficult to predict, controversial. I prefer laser: 9000 burns/eye,
over ~8weeks. Examine
in 2-4 months to see benefit, may need more laser over next 2 years.
If no laser, examine every 3-4 months.
Reasonable control, already had
new vessels treated with 12000 burns, but new vessels remain. Need
Reasonable control, already had
12000 burns, not much room for more laser, but new vessels persist...?
Avastin. Check the peripheral retina carefully...certainly more laser
if there is lots of space.
Poor control (or control poor
in the last 1-3 years), active new vessels, vitreous haemorrhage,
only had 9000 burns. Needs more laser. ?Avastin then laser. ?Vitrectomy ?Avastin
then vitrectomy the next week. Laser other eye.
New vessels 2002, laser PRP,
3000 larger burns both eyes (euqivalent to 12000 smaller lighter burns), vessels regressed. Mediocre control at this
2008 presents with vitreous haemorrhage. Hard to see new vessels,
but there are a number of blot haemorrhages. Also, lots of unlaserd
Blot haemorrhages suggest continuing ischaemia and probable
new vessels..therefore laser remaining peripheral retinal until
patient as patient 11 but no blot/retinal haemorrhages...could
be a simple PVD pulling some 'older' new vessels...this is more
likely if there are no retinal haemorrhages at all. Probably
safe to watch in this case.
Age 80y, had macula laser 2 years
ago. Poor control, very overweight. New vessels now....continue with
peripheral laser..until most periphery lasered.
New vessels elsewhere just in
one area of retina, not many haemorrhages. May manage with
laser to the appropriate sector e.g. superior temporal quadrant. But
all sectors with ischaemic blot haemorrhages should be lasered.
Same patient as patient 14 with
good control/non-smoker for the last 20 years..generally not much
Laser PRP..how much, some ideas
- Increasingly anti-VEGF injections are taking over as the main treatment in many countries.
- In all the examples above, normally.....each
eye each session: 2-3000 burns/eye...normally both eyes lasered same
session: these are light small subthreshold burns, my current policy...
0.01 second, 2-300µ, fast repeat, Pascal ideal
- very active new vessels...~5 sessions, much of the
peripheral retina needs laser, urgent (more for lighter smaller burns) with heavier laser.
- a few new vessels, reasonable & stable control (HbA1c & BP),
no previous laser, 3 sessions, subthreshold.
- a few new vessels, lots of previous laser, 1-2 sessions
- severe pre-proliferative, very good control (and good for previous
3-4 years), difficult decision, 3 sessions smaller lighter burns (but
generally new vessels will develop and a lot more laser will be needed
perhaps 1-2years). Anti-VEGF injections are needed if available.
- severe pre-proliferative, good control, smokes 20/day, ~5 sessions
- severe pre-proliferative, poor control, ~5 sessions; Anti-VEGF injections
- pre-proliferative, other eye proliferative, ~3 sessions
- severe pre-proliferative: most people in Europe now treat with Anti-VEGF injections, or laser if they are not available.
- if the new vessels are very active most peripheral retina needs to
be lasered in the next few weeks, (Anti-VEGF injections instead or inaddition)
Laser settings for PRP...proliferative retinopathy
- the same settings are used for PRP laser of pre-proliferative retinopathy...see
planning laser above.
- The transequator lens is an excellent lens for peripheral laser
- Mainster 165 lens is useful for more peripheral retina, but is harder
- 0.01seconds (quite a short duration): these
short burns are less painful but if ~300µ more burns will
be needed than longer or bigger burns. Essentially this is copying
the Pascal laser technique.
- 300mw ~300µ for PRP, short light just visible burns (or just
invisible...that is visible and turn the power down a little). More
of these light burns will be required than the previous policy of
- consider using 300mw and adjust spot size according to the burn
intensity...use the size that gives the correct intensity. Aim for
slight blanching, then turn power a little lower so burns are hardly
visible. Very important paper, calculate the number of burns: Retina 2011 'To maintain the same total area as in 1,000 standard burns (100 ms, moderate) with a 400-μm beam, a larger number of 20-ms lesions are required: 1,464, 1,979, and 3,520 for moderate, light, and barely visible grades, respectively. Because of stronger relative effect of heat diffusion with a smaller beam, with 200 μm this ratio increases: 1,932, 2,783, and 5,017 lesions of 20 ms with moderate, light, and barely visible grades correspond to the area of 1,000 standard burns.'
- if power is kept unchanged: smaller burns if there is a cataract
(these will be more intense), larger if the retina is pigmented or
the patient pseudophakic (these will be less intense).
- Larger burns can be used, with even higher power, but they should
still be light burns as below.
- 3000 burns/session/eye (lighter 3-500µ burns) both eyes each
session can save time
- Pascal laser seems to give a better results, with fewer sessions needed, Retina 2011. Is this because laser burns are shorter pulses or lighter? ..I think this is likely, which is why shorter lighter burns are suggested here.
- Light burns (just lighter than blanching): for these rapid
0.01 second burns, 'light' burns are best, hardly visible when first
burnt but may be just visible minutes later ...see here
for Bandello's paper; a few more burns may be required, but complications
are significantly less.
- remember if you use a longer duration of burn, use a lower power
- If you suspect macular oedema is present, even if mild, carry out
a light macular grid first and wait 2 weeks unless treatment is urgent.
- In all except young type 1 patients with healthy maculae many ophthalmologists
prefer to carry out a light grid macular laser before the PRP, to prevent
macular oedema. If starting laser early, this may not be necessary.
- Heavy burns produce more epiretinal membrane, and there is no benefit.
Laser too light has too little an effect.
- But in severe cases, I tend
to carry out 4 sessions treating both eyes each session in the first
week (still 3000 burns/eye/session, very light invisable/just visible
burns, with more the next week. Delaying laser makes
vitreous haemorrhage likely. Lasering quickly, that is ~6 sessions
over 1-2 weeks, lighter 300µ burns,
means that most of the retina will have had a lot of laser before
the view is obscured by the haemorrhage.
- Most routine cases without severe retinal ischaemia can have the
laser applied over 5 weeks.
- Transequator for the first 2 sessions, after that use the Mainster 165
or other wide angle lens for a couple of sessions...this will reach
more peripheral laser than can be reached with the transequator lens.
- After 5-6 sessions/eye with a transequator lens (or even before)
the laser may become very painful...try smaller burns, with less power,
still using 0.02 seconds.
- Auditing recent work two patients developed vitreous haemorrhages.
In retrospect it was clear the patients did not have as much as laser
as they needed, or as much in Shimura's protocol as above. In one
this was prevented by cataracts....earlier indirect laser or cataract
surgery and immediate laser probably should have been carried out.
In the other, there was too long a gap between treatments...the patient
insisted on going on a long holiday. A 6 week gap instead of a 2
week gap lead to a serious vitreous haemorrhage. Other patients have
even more aggressive disease...some need daily laser, 3000 burns/session,
very light 300µ burns,
even in hospital if they are at risk of 'absconding', but with better
screening we get very few such patients.
- Another observation...some patients are seen for follow up and everything
is reported 'OK'. They then 'bleed' few weeks later. Generally these
patients will have had new vessels...so if this is happening in your
department, start looking for new vessels more carefully. I find a
very bright Welch Allyn ophthalmoscope with a green filter picks up
more new vessels than a 60d lens on a slit lamp.
- subthreshold laser: use high powers in a very brief pulse...people
are trying to copy this with their argon laser...high power, short
times, light burns, hence the 0.01 second pulse
- More laser is needed until the new vessels regress (DRS 89).
- Start lasering the inferior retina more heavily that the superior
retina, as this will be obstructed if a vitreous haemorrhage and the
superior retina is more important in preventing falls. In severe cases
the superior retina will still need heavy laser.
- Except in the mildest cases do not delay by waiting weeks for a fluorescein
- PRP laser...keep outside the macular arcade, at least 2 disc diameters
from the disc. Laser within this area..see macular
with much smaller burns.
- See pregnancy
- Use Avastin in severe cases.
PRP laser..preventing macular oedema
- this is usually unavoidable in sevee cases...aggressive new vessels need lots of
PRP laser quickly.
- subthreshold burns..lighter burns (more light burns versus fewer heavier)
are unlikely to porduce macular oedema or epiretinal membranes, and are ideal in the none-severe cases.
- start with grid macular laser unless young type 1 with healthy macula (if Anti-VEGF injections are nto available)
- A number
of patients seem to develop macular oedema even with lightish burns,
but fewer than with heavier laser, ....no hard evidence. OCT examination
shows that unfortunately most patients seem to develop increase retinal
thickness after PRP laser, and some loss of vision.
- Anti-VEGF is taking over as the main treatment, with half the amount of macular oedema and
- The Restore
study indicated anti-VEGF injections (Avastin/Lucentis etc)
will help reduce macular oedema more than laser (laser probably helps
in the long term).
- Anti-VEGF injections will help in most cases of active proliferation.
If there is macular oedema before starting laser, this is likely to
increase with PRP laser, which is one of the main reason anti-VEGF injections are taking over as the main treatment. This
paper is important, indicating that oedema of para-foveal areas
makes post-PRP laser loss of vision much more likely, and sometimes
this is permanent. This may mean we should carry out a macular grid
first, and wait for the oedema to reduce...but very often there is no
time to do this (active proliferation requires laser soon). This paper,
to my mind, implies that it is important to grid laser anyone with para-foveal
macular oedema, in the pre-proliferative stage, so that the macular
oedema has time to settle by the time full PRP laser is essential.
Macular oedema is very common after PRP, even after macular grid laser.
Sometimes this is because the PRP was too heavy, as Bandello above.
(Low blood pressure will help a little...even <130mmHg systolic.
Lighter burns as above have further reduced this problem substantially
clinically (no hard evidence for this..and as above OCT does demonstrate
oedema/increased retinal thickness in many patients).
As above, in all except young type 1 patients with healthy maculae
many ophthalmologists prefer to carry out a light grid laser before
the PRP, to prevent macular oedema. Carry out the grid and PRP laser
at the same session in very severe cases or if you think the patient
is not likely to come back again.
Eyes with considerable ischaemia are far more prone to
macular oedema. If macular oedema is presnt anti-VEGF ijections are really essential.
Laser PRP and visual field loss
Laser burns enlarge. If there is active proliferation, there is absolutely
no choice but to laser. But once much of the retina is lasered, the
patient will have lost a fair amount of visual field.
At this stage, further laser will cause much more significant field
loss: if 60% of the retina is lasered, lasering 10% of the the remaining
unlaserd retina will cause 25% more field loss.
For this reason, a number of our patients have had to stop driving,
and have great difficulty with their side vision. To prevent this, we
are starting to use Avastin. We hope 3 injections (after much of the
retina has been lasered) will stop proliferation indefinitely. We are
waiting to confirm this! All our Avastin patients get new vessel regression
for a while, but unless they are well lasered the proliferation occurs
later...the Avastin only delays progression.
Everyone is hoping subthreshold laser PRP will enable lighter burns
and hence maintain a better visual field. The PASCAL laser produces
quicker burns...may be this will be helpful. PASCAL laser seems to be
a big step forward, but the laser costs 3 times as much as a regular
laser, and inadvertent macular laser is a possibility with the current
Lasering through a cataract or vitreous haemorrhage
When lasering through a vitreous haemorrhage or cataract
- make the spot size smaller
- if this does not work, increase the duration of the burn, to 0.05
- Using the very short pulses of 0.01 seconds may produce very intense
burns...one moment you are lasering through blood using the correct
power, but the next moment when there is less blood the burn becomes
too intense. so care is needed.
- See "One
or 2 intravitreal injections of 1.25 mg Bevacizumab with PRP are associated
with rapid regression of VH and may reduce the need for vitrectomy."
- For some reason laser at a slit lamp may not be possible
- after a lot of PRP laser the retina becomes very sensitive and further
laser becomes extremely painful
- Also for some patients, proliferation may be remain very active despite
lots of laser...consider indirect laser with an anaesthetic. However,
as above, we would like to use Avastin rather than extremely heavy laser.
- If laser extremely painful, indirect laser, may be 2/3 occasions/eye
will be much less painful.
- We use general anaesthetic for bilateral indirect laser, peribulbar
- routine more
Retinopathy is symmetrical
When carrying out PRP laser it is very important to treat the fellow
important paper suggests. Unless the retinopathy is highly asymmetrical,
which is most unusual, laser is important. Furthermore, the same paper
suggests that 4-6000 3-500μ burns are needed to prevent
retinopathy developing to maintain vision in the long term. This is because
the worst visual results were in the second eye to be treated.
retinopathy is very asymmetric suspect carotid
Planning treatment for diabetic maculopathy
Remember to address diabetic control. Anti-VEGF injections are the main treatment, but if not available laser as here (as previously regularly used):
- If there is diffuse macular oedema, or extensive oedema, grid laser is
- Follow up for the average case 2 months.
- At 2 months, if there is a poor laser response as seen clinically, and
the macula oedema has not reduced, repeat the grid laser. Do not repeat
if plenty of burns visible.
- At 2 months, if the macular oedema has not responded at all AND there
is a good laser response with are enough burns, consider an FFA to identify
if more laser is needed (or intravitreal steroid etc). If the laser is
going to work, the oedema should be reducing at 3 months.
- Exudates take much longer to go (statins/fibrates are
important), but start to reduce if treatment adequate.
- Macula oedema is best measured by OCT.
Clinical judgment is helpful; FFA can help.
- If the leakage just affects a small part of the macula, as in circinate
retinopathy, 'focal' laser is applied. The same settings (as
below) are used, but the laser confined to the circinate/affected area.....for
focal laser...similar settings, fewer burns. Focal laser is used, for example,
on an area of circinate retinopathy: this is essentially the same as a
grid but only a sector of macular laser is carried out, but again no laser
within one disc diameter of the fovea.
- 2-3 sessions may be needed over a year; after 3 sessions little further
macular grid laser is needed in the years to come, whether or not there
is oedema. FFA is carried out if there is a poor response to laser after
2 grid laser treatments.
- As with any retinopathy, control of the diabetes (sugar, HbA1c, blood
pressure, cholesterol) is essential for success of this treatment.
- Pan-retinal photocoagulation (PRP) may be needed as as part of the treatment
for severe or diffuse macular oedema. If there are no ischaemic haemorrhages,
and the maculopathy is the only retinopathy present, it is not likely to
help. Eyes with a lot of ischaemic blot haemorrhages have very ischaemic
central retinae, and often have new vessels that are not obvious clinically,
or often develop them over the next two years, and PRP laser helps to prevent
At present I would recommend the PRP is carried out 2-4 weeks after grid
laser, whether of the heavier, as sometimes pan-retinal laser can increase
oedema. In theory, if carried out in this manner, oedema should not increase,
with provisos such as (poor control).
- No laser is needed within 1 disc diameter of the fovea , except
for lasering the occasional microaneurysm
>500 µ from fovea.
- Very severe macular oedema...grid laser does not help. IVT had
not proved helpful overall. Avastin for
persistent macular oedema; resistant cases intravitreal
- After laser, burn size enlarges.
This is called burn creep. Over the years, the creep can spread in towards
the fovea. For patients years ago this did not matter as they were very
ill, but patients who improve their diabetic control have a longer life
expectancy, and this 'enlargement of burns' or burn creep may threaten
their sight many years after laser.
- Many doctors laser outside the macular area if there is considerable
ischaemia (shown by blot haemorrhages). In a way this distinction is
academic: any eye with a lot of retinal ischaemia will develop proliferative
changes in 3-18 months, and this will need laser. Many ophthalmologists
carry out PRP laser if there is substantial peripheral
ischaemia (my preferred policy).
- OCT is very useful. Previously we waited for obvious maculopathy as
seen on a slit lamp before recommending laser. But we know laser seldom
improves sight. So logically we should laser earlier, as soon as there
in ANY (except the mildest) thickening as seen with OCT. With very slight
OCT thickening (macular oedema), show the patient the scan. Offer laser;
encourage the best glucose and blood pressure control (& no smoking,
weight loss, physical exercise). Laser if the patients wants.
4 months later review ...if the retina is thicker, and no laser was carried
out, then obviously laser is now needed. Outcomes in macular oedema are
best with anti-VEGF treatment
- See results of laser Eye 2011
Laser for diabetic maculopathy: settings
Remember to address diabetic control. Anti-VEGF injections are the main treatment, but if not available laser as here (as previously regularly used):
- Subthreshold diode laser, with nearly confluent very light burns, probably produces the best results. This is seldom available in the UK. Venkatesh 2011 Lavinsky 2011 best; Nakamura
2010, see above Kumar
2010 Retina 11
- Area-centralis lens is an excellent lens for diabetic maculopathy, Mainster
- 200-300 x 50µ burns for a maculopathy grid, less for focal
- 0.01 seconds
- see techniques
- light burns, subthreshold. Laser first to see a visible impact, then
turn the power lower so the burns are invisible. The subthreshold diode
laser uses infrared laser with very short burns....it is not clear clear
whether it is the wavelength that helps, or using a shorter pulse time,
or using lighter burns. Most lasers can be adjusted to provide a very
short pulse eg 0.01 seconds (my current time) and a low power (subthreshold):
few departments have access to a diode laser.
study suggests that it is important to laser/laser around microaneurysms
- No laser within 1 disc diameter from the fovea.
study suggests that lasering microaneurysms a little closer than
this (but still greater than ~500µ from the fovea) may be helpful.
- Autofluorescence is seldom available but may help ?identify the FAZ (foveal avascular zone)
- Include laser to adjacent non-perfused areas (outside the grid laser
area, that is above, below, and temporal).
- Light invisible subthreshold burns.... one of the reasons for using
lighter burns is that they cause less atrophy in the much longer term.
It is difficult to know how heavy to make the laser...but burns that
do not show on a fluorescein angiogram later were probably too light,
so you can tell retrospectively. Burns that were too heavy cause significant
atrophy. Even 'perfect' burns may produce very slight pigmentation, but
significant pigmentation indicates excessive power. Burs at the most
intense should be only just visible, they may still need to
be a little lighter (invisible). Planning laser is more important...the
same area should not be treated twice.
Some experts recommend subthreshold diode laser burns that are nearly confluent
(but at present I still leave one burn space gap between such invisible
- Low power for pigmented retina (often 50mw), especially if pseudophakic
and media is clear; higher power if there is a cataract or macular oedema
(usually <180mw). Average power 60mw. More power needed according
to the amount of oedema present. Thus the power (milliwatts): an Afro-Caribbeans
retina in a pseudophakic eye with mild oedema needs a low power; a Caucasian
retina with a cataract and considerable oedema needs a much higher power.
- The laser power used now is lighter than originally described in the
laser with Avastin
treatment plan for diabetic maculopathy
modified after Simon Harding, 2007 and Olk, (Now replaced with anti-VEGF injections):
information sheet and record this in notes
or diffuse maculopathy?
area of oedema
Anti-VEGF main treatment, laser may be needed addtionally: grid laser
laser shots to microaneurysms if >1 disc diameter from fovea
scatter laser to non-foveal areas of non-perfusion/IRMAs
Reassess 2 months.
If poor laser response as seen clinically, repeat (i.e. if laser burns
not visible and maculopathy no better;) do not repeat if plenty
of burns visible. Anti-VEGF main treatment always needed at this stage.
4 months later,
consider repeating laser if oedema/thickening remains or not reduced
with OCT, otherwise FFA.
treat leaky areas
as identified with FFA;
consider anti-VEGF drugs;
very ischaemic macula with very large avascular foveal zone...very difficult
to achieve improvement..consider PRP
all patients for deterioration/proliferation.
Macuopathy grid laser technique
Create boundaries for the laser....muct keep away from the fovea.
Some exceptions..may need a little laser to micornaeurysms slightly within this are..but only a few shots of laser , and not near the fovea.
Extend the boundary a little horizonatally
Laser always moving from the fovea (again, this is to preent foveal laser). SUbthreshold laser is invisble so you need to remember which area has been treated.
Standard grid laser, with extra shots further out, more laser in ischaemic area ... areas of microaneurysms and haemorrhages
PRP Laser is traumatic and painful
Having laser is a very traumatic experience, especially PRP laser. Trento
and others investigated this (EASDec 2003) and found
- it is not so much as that the laser is distressing, but knowing that
the eyes are seriously affected by diabetes. A good explanation and
counselling may help, but this is often a very serious development for
- the laser itself is not that painful for the first few sessions (I would
add that lower powers are used now, as above).
burns are less painful ....0.02 seconds for PRP as above.
The Pascal laser is much less painful BJO
does not help. Diclofenac did work (but not when I tried it).
- laser can become very painful after the first 5 sessions. In
my experience no pain relief helps, but small burns and a lower power
- Indirect laser is very helpful when the laser has
become very painful, perhaps after 6 sessions. Should we use subtenons: Richardson
- Smaller lighter burns can be used instead of indirect laser...though
obviously a lot of the retinal periphery must be lasered as above.
- PRP laser thins the retina Retina 2013
- PRP well tolerated Retina 2013
- visual field loss as above
- inadvertent foveal laser
- macular oedema as above
- laser too heavy...this can be avoided....choroidal detachment (and
this may lead to complications such as angle closure glaucoma).
- Macular laser can lead to CNV, but this is unlikely with the lower power
settings used now.
Read this book
Retinopathy and poorer quality of life
Can be very helpful