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Ophthalmology

Consultant ophthalmologist Mr Scott Fraser tackles questions on the latest treatments from GP Dr Melanie Wynne-Jones

Consultant ophthalmologist Mr Scott Fraser tackles questions on the latest treatments from GP Dr Melanie Wynne-Jones

1. We are hearing more about Macugen and Lucentis, the new treatments for age-related macular degeneration (AMD). How do they work, how effective are they, and should patients receive them on the NHS?

AMD is the most common cause of visual impairment in the UK. Although there are a number of sub-types there are two main forms:

• The 'dry' type which presents as a slow decline of near vision.

• The 'wet' type in which blood vessels from the choroid extend into the retina causing sudden distortion of vision. If these vessels bleed there is a rapid decrease in vision.

It is this second (less common) type that the new drugs pegaptanib (Macugen) and ranibizumab (Lucentis) target. They are monoclonal antibodies against the vascular endothelial growth factor and blocking this growth factor can cause the abnormal vessels to retract. Early studies have suggested a significant role for treating patients with wet AMD with larger studies ongoing.Treatment of wet AMD poses a problem for those responsible for the allocation of healthcare resources. On one hand the new treatments appear to halt or slow a blinding disease in a number of patients, so preserving their vision and independence.On the other hand both Macugen and Lucentis need to be administered by intravitreal injection (therefore requiring trained practitioners and appropriate facilities) every four to six weeks for life. Therefore the financial challenge is not only the cost of the drugs but paying for the expertise and infrastructure.

2. Ophthalmologists are starting to recommend supplements such as I-Caps for AMD. They're quite expensive – is there any evidence that they are any better than eating a healthy diet?

Clinical trials have suggested that zinc and various antioxidant supplements slow the development of AMD, especially the 'dry' type mentioned above. The studies actually suggest the benefits are quite small and only observed for certain sub-types of dry AMD.

However, the fact there are no other treatments for dry AMD and the relatively harmless nature of the supplements has led to the commercial development of supplements specifically aimed at patients with AMD and I-Caps are one of these.These products are not prescribable on the NHS as they are classified as food supplements. All of the antioxidants are available in many fruits and vegetables, but you would have to consume very large quantities to reach the levels used in the studies. Most ophthalmologists advise AMD patients to have a healthy diet with plenty of fruit and vegetables and most importantly not to smoke (see below). They might also suggest commercial supplements but often leave the decision to the patient.

3. How should we counsel smokers about the effect of smoking on various parts of the eye?

Smoking can have an effect on almost any part of the eye. These can be direct effects such as an increased risk of AMD, cataracts or toxic optic neuropathy. Indirect effects (ie worsening of an already established condition) include worsening of diabetic retinopathy, thyroid eye disease and central retinal artery or vein occlusion.

There is little doubt that smoking increases the risk of blindness. Many smokers seem unaware of this link and it can be a strong motivation to stop.

4. How is ocular hypertension defined, what are the risks to sight and how should it be treated?

Ocular hypertension is a generic term that indicates the intraocular pressure (IOP) is above 21mmHg. This figure is two standard deviations above the population mean and was taken for many years as the cut-off between 'normal' and 'raised pressure'.

Our understanding of the relationship between IOP and glaucoma is now more sophisticated. It is well-recognised that many patients with IOPs above 21mmHg never develop glaucoma while many who never have 'raised' IOP do. This has led to the modern concept that raised IOP is not a diagnostic criteria for glaucoma but rather a (very important) risk factor. Large studies have shown the conversion rate of ocular hypertension (ie raised IOP only) to glaucoma (ie optic nerve and visual field loss) is around 10 per cent over 10 years. In other words, 90 per cent of patients with raised IOP will not sustain glaucoma over this time. To some extent the IOP/glaucoma relationship is analogous to the BP/stroke one in that both are asymptomatic risk factors that can cause neural tissue damage. The calculation of the risk of visual field loss is used to decide if a patient with ocular hypertension needs treatment.

5. What is nerve fibre analysis and would everyone with glaucoma benefit from testing? How often?

Glaucoma is a progressive optic neuropathy clinically seen as excavation of the optic disc and visual field loss consistent with this loss. The excavation is actually caused by the death of the ganglion cells which cover the retina and converge to exit the eye at the optic nerve. It would appear that damage and death of these ganglion cells at the optic nerve is the basic pathological mechanism of glaucoma.

Very careful observation of the surface of the retina can sometimes reveal loss of these bundles of ganglion cell loss. This technique is called nerve fibre layer analysis and is highly suggestive of glaucoma. As it is objective (unlike visual field analysis which is subjective) it can also be used to monitor progression of the disease. Although all this sounds ideal, the technique is prone to artefacts, especially if the patient has cataracts, as many do. The machinery is relatively expensive and for these two reasons it is only really a tool used in specialist glaucoma practice.

6. What is the rationale for choosing one type of drug for glaucoma over another?

There are a number of eye drops that reduce the IOP with differing modes of actions and therefore side-effect profiles. The decision to use one particular drug depends on the type of glaucoma, IOP reduction needed and the possibility of local or systemic side-effects.

Topical ß-blockers are used less because of the possibility of systemic side-effects. In most eye units topical prostaglandins are first-line therapy because of their efficacy and lack of systemic side-effects. Unfortunately, a small number of patients do find these drops sting or cause red eyes and discontinue them because of this. As with any treatment, what suits one person does not suit another and it may be necessary to alter medications, sometimes within the same class, to find one better tolerated. It is rare to find any eye drop that does not cause at least a minor degree of discomfort on instillation and this may be related to the active ingredient or the preservative. Usually this is tolerated and not a reason to stop medication. If you see a patient on glaucoma treatment who is having problems with their drops it is best to ask them to ring their local eye unit for advice.

7. How should we manage the patient presenting with shingles affecting the upper face?

A patient presenting with 'fresh' shingles, ie with vesicles still present, should be treated as normal with oral antivirals. If the upper or mid dermatome of the face are involved then the eye can be affected in a number of ways.

However, ocular involvement is obvious either as symptoms such as pain, photophobia or reduced vision or as signs such as a red eye or reduced vision on testing. If there is ocular involvement the patient should be referred within 24 hours to the local eye unit. If the eye is quiet and the patient has no eye symptoms then referral is not required.

8. Can patients with recurrent uveitis be given steroid drops without urgent reassessment? When should they be re-referred?

Patients with recurrent anterior uveitis often need intermittent topical steroids, but to give these without the ability to monitor with specialist equipment is unwise. As well as the possibility of incorrect diagnosis, for example, herpes simplex keratitis, there are the side-effects from steroids such as raised IOP and cataract.

Patients with previous uveitis who feel they are getting a further attack, even if there are no signs, should be referred to an eye department within 24 hours. I would not suggest prescribing topical steroids for a patient unless told to by an ophthalmologist.

9. How does Charles Bonnet syndrome produce complex visual hallucinations? How can we recognise it, and should patients be referred?

Charles Bonnet syndrome is a condition of unknown aetiology in which visually impaired people experience visual hallucinations. The hallucinations can range from simple patterns of straight lines to complex, detailed pictures of people or buildings. Patients can be upset by the condition and are often very relieved when their benign nature is explained.

Charles Bonnet-type hallucinations do not need investigation or psychiatric referral. The distinguishing features are the lack of other physical or psychiatric findings and the fact patients with Charles Bonnet do not confuse the images they see with reality.There is no specific treatment but discussion of its benign nature is often reassuring.

10. How should we advise patients who ask about laser refractive surgery? How safe are they, and who should not risk it?

Refractive surgery, of which laser is one type, is conducted with the intention of eliminating or reducing a person's need for optical correction. It is not suitable for everyone and like any surgery has a small risk of leaving recipients worse off. Laser refractive surgery is not available on the NHS and those considering it need to approach a private practitioner specialising in it.

Anyone considering surgery needs to be fully aware of the risks and benefits and before embarking on this treatment, patients need to be happy that they understand any risks. Any reputable practice will be happy to answer questions about these risks, the surgeon's expertise and what will happen if something does go wrong. The Royal College of Ophthalmologists provides some guidance to patients which can be found at:

www.rcophth.ac.uk/about/public/laser

11. How soon should someone with symptoms of retinal detachment be seen by an ophthalmologist?

The first symptoms of retinal detachment may be the sudden onset of floaters as the vitreous changes, and intermittent flashing lights as the vitreous pulls on the retina. If the retina itself detaches the sufferer usually notes a peripheral shadow or curtain slowly moving towards the centre of their vision over days or weeks.

Patients with symptoms of vitreous changes (flashes, floaters) should be seen within 24 hours while those with retinal detachment (shadow coming over vision) need seeing the same day by an ophthalmologist.

12. Chloroquine is known to threaten sight – what other drugs have ocular side-effects?

Many systemic drugs have ocular side-effects, most of which are not serious or are reversible. But there are certain drugs that can permanently harm vision and patients need regular eye examinations, although not necessarily by an ophthalmologist. These include chloroquine and hydroxychloroquine, ethambutol, vigabatrin and tamoxifen.

A number of drugs, including some antidepressants, can, in susceptible individuals, precipitate angle closure glaucoma. In the UK this is the less common type of glaucoma, but if a patient is known to have glaucoma it is best to check with their eye department which type they have prior to prescribing. If a patient has symptoms of haloes or pain after initiating a drug then they should see a good optometrist for assessment of their anterior chamber drainage angles.

Scott Fraser is a consultant ophthalmologist at Sunderland Eye Infirmary

Competing interests None declared

Take-home points

• Monoclonal antibodies against vascular endothelial growth factor can have a role in wet AMD but it is an expensive lifelong treatment.

• Dry AMD is slowed by antioxidants but the benefits are small and apply to sub-types. A good diet and not smoking are important.

• There is little doubt that smoking increases the risk of blindness.

• Many patients with an IOP>21mmHg never develop glaucoma while many without raised IOP do; IOP is a risk factor for glaucoma analogous to raised BP and stroke.

• Most eye drops cause at least a minor degree of discomfort on instillation related to the drug or preservative.

• A patient with previous uveitis who feels an attack is coming should be referred to an eye department within 24 hours.

What I will do now

Dr Melanie Wynne-Jones comments on the answers

• We have already been asked by patients to prescribe I-Caps and now I know why I couldn't find it in the BNF. This will enable me to suggest patients buy their own if they don't want to eat more fruit and veg.

• With emergency appointments in short supply and commissioning pressures, I sometimes wonder if I am being over-cautious by referring patients with their 'usual' uveitis. I will feel more justified in future.

• I will also feel confident to insist that people with flashes and floaters are seen within 24 hours; I get worried that I may have missed a retinal detachment in these patients.

• I'm pleased to see more arguments for advising patients to stop smoking – I think health promotion advice usually works better when it's relevant to the patient's particular problem or fears.

• I didn't realise that Charles Bonnet syndrome could produce such complex hallucinations.

Melanie Wynne-Jones is a GP trainer in Marple, Stockport

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