www.diabeticretinopathy.org.uk

Laser Treatment for diabetic retinopathy

David Kinshuck

Laser..introduction

contact lens used for retinal laser

Laser light (shown in yellow) is shone into the eye through a small contact lens, and makes small burns on the retina.

 

Laser treatment was the main treatment for retinopathy, although increasingly anti-VEGF  injections are taking over.

Laser is usually carried out in a darkened room in clinic. Anaesthetic drops are dropped into your eye, a contact lens is placed on your eye, and you have to sit at a laser slit lamp. This is virtually the same machine as that used for the regular examination, but a laser has been added on. It is naturally uncomfortable having to keep still whilst a doctor flashes a very bright light into the eye.

Each treatment is slightly different, depending on the condition of the eye. Laser is simply a highly focused and powerful light, where the light rays are all of the same type.  Therefore it can be pointed at one spot on the retina very accurately. Each bright flash lasts for about 0.02 seconds. The commonest laser is Argon Green, wavelength 530nm, but other wavelengths can be used and most are equally effective. Other types of light were used before laser was introduced.

 

Laser for diabetic maculopathy

Enlarge a common type of laser for maculopathy (burns are shown white for illustration)

Anti-VEGF  injections are taking over in the treatment of maculopathy, but this treatment is still needed occasionally or when injections are not possible.

Laser for diabetic maculopathy is also discussed here. An average of 300 burns are needed. This type of laser is not particularly painful, and you notice a bright sting. You will be asked to look in a certain position at different times.

After each session your sight may be dim or blurred, and this improves over the next dew hours. After this treatment, some people, those with healthier eyes, may notice little black marks in their vision if they look at a white background, and this starts to fade months after the laser. It can take 3-6 months before for the leakage in the retina to reduce; sometimes proliferative retinopathy may develop as well, which will also need a lot more laser .

Just as important as the laser is controlling the blood pressure to below 130/80 if possible, control of the diabetes (fasting blood sugars of about 6mmol/l, HbA1c of 6.5% or below), and not smoking. See below.

Here is a patient 2006 (left photo) treated with laser the next week, who at the same time started to improve his diabetic control, lose weight, and lower his blood pressure. The right photo is after treatment in 2007. Below is same photo a little smaller.

before laser (left), and one year after laser (right)...the exudates (white areas) have disappeared

Anti-VEGF injections (and less often intravitreal steroids) are often needed in addtion or instead of laser:

 

Laser for proliferative retinopathy or severe pre-proliferative: PRP laser (peripheral laser photocoagulatioin)

enlarge laser for proliferative retinopathy (white for illustration)

The laser is applied the same way, usually through a slit lamp in the clinic. Each treatment is often 1-3000 burns or more. Much more in one session may cause inflammation of the eye, and too little too little an effect.

The side or 'peripheral' retina is lasered, not the centre; this is the main difference of laser for proliferative retinopathy as opposed to maculopathy above.  NEJM 11

The downside of PRP laser includes the discomfort. At first the treatment sessions are unpleasant, with stinging flashes.

 

After the laser

As time goes on and more laser sessions are needed, the treatment can become extremely painful. There is no entirely effective way of reducing all the pain, except a general anaesthetic.

Local anaesthetic injections in the operating theatre, or tablets that aid relaxation, may help a little. Sometimes the local anaesthetic injection takes away all the pain, sometimes it just reduces the pain slightly. The injection is not into the eye, but under it, at one side.

For patients where the treatment is extremely painful larger departments offer general anaesthetics, as these also have the advantage of allowing laser treatment to both eyes. To do this the department must have a laser that can be used in an operating theatre.

The 'up' side of this laser is that the treatment nearly always works, although several treatments may be needed, and further treatments may be needed over the following months and years. An individual laser session only has a very marginal effect on vision.

A 30 year old person with a lot of new vessels may need 18000 smaller laser burns per eye, or even more, to prevent the new vessels growing. Other people usually need less. In patients with very severe disease so much laser may be required that the side vision becomes poor and driving unsafe: the aim of the treatment is to keep good central sight, that is sight looking straight ahead, which is need to read, work, and watch television.

If the proliferation is very aggressive, intravitreal anti-VEGF will help, in addition to laser. It always shrinks the new vessels, but unless there has been a lot of laser treatment given, the new vessels always recur. We are learning how to use anti-VEGF treatment, and each ophthalmologist uses it differently. (At present at Good Hope we have no funding so cannot use it.).

Without laser proliferative retinopathy is often blinding, so both patients and doctors may be left with little alternative to enduring and carrying out this often unpleasant treatment. Again, control of diabetes as for maculopathy above is very helpful where possible in the long term.

In the short term, improving control from mediocre (say HbA1c 9%/80mmol/mol) to good (say (6.5%/48mmol/mol) may encourage unexpected growth of the new vessels, needing laser. This is discussed.

However, the improved control is still needed in the long term, and most people are advised to achieve good control even if that means extra laser in the next 2 years, because in the longer term (after 2-3 years) research has shown good control reduces eye and other problems.

 

Laser for pre-proliferative (non-proliferative) retinopathy

Sometimes laser is needed for pre-proliferative retinopathy: the treatment is similar to that of maculopathy and proliferative retinopathy. Nearly all eyes with severe pre-proliferative retinopathy needed laser, but increasingly anti-VEGF injections are taking over.

Eyes with mild pre-proliferative do not need laser; eyes in between often do need laser. Ideally laser will be carried out before there is macular oedema.

 

New treatments

The Anti=VEGF injections Avastin, Lucentis, Eylea are proving very helpful.

 

Remember the 'targets' for good control

By keeping to these levels as much as possible (or lower still) you will be doing your best to stop your eyes getting worse. Occasionally by sticking to these targets your retinopathy will improve, even without laser. Review BMJ17

 

lifestyle

blood pressure

HbA1c

sudden decrease in HbA1c

cholesterol

smoking

insulin

education

sleep apnoea

glucose level

Glitazones

hypoglycaemia

neuropathy

issues

compliance

type 2 at diagnosis

 

 

Abbreviations