Dry and wet

macular degeneration differences

The macula is a small, central area of the retina that is responsible for your detailed vision (visual acuity).

The condition of the macula contributes to our ability to read, drive, watch television, and perform many other daily tasks. Age-related macular degeneration (AMD), also known as just macular degeneration, however, is a common eye condition among the elderly and has been identified as the most common cause of adult blind registration in many developed countries, 1 2 including the UK34.

In some cases of AMD, the condition can advance slowly and reduction in vision may not occur for many years.

Conversely, the disease can progress quickly and may lead to loss of vision in one or both eyes. However, during the progression, a blurred area near your central line of vision commonly forms. This may grow larger over time and cause objects to appear dimmer and out of focus.

AMD is diagnosed as either dry (non-neovascular) or wet (neovascular), with the former being the more common of the two. Roughly 90% of AMD patients are diagnosed with dry AMD. The wet form of the disease, however, usually has a sudden onset and can lead to more serious vision loss.

What is dry macular degeneration?

Dry AMD is classed as an early stage of the disease and may result from the aging or thinning of macular tissues. It’s diagnosed by the presence of yellowish spots, called drusen, that begin to accumulate in and around the macula. This tends to occur due to a build-up of debris from deteriorating tissue.

Dry macular degeneration risk factors and causes

Several risk factors for dry AMD have been recognised. The strongest, as alluded to, is age.

The exact causes of dry AMD are unconfirmed, however systemic (relating to the whole body) risk factors may include:

Hypertension

Smoking

Family history5

Dry macular degeneration symptoms

Dry AMD symptoms tend to develop gradually. These can include:

Visual distortions

Reduced central vision in one or both eyes

Dim vision

Difficulty in adapting to low light levels

Increased blurriness

Decreased intensity or brightness of colours

Dry AMD usually affects both eyes. If only one eye is affected, however, you may not notice any changes in vision due to compensation by the other eye. Thankfully, since the condition doesn't affect peripheral vision, it rarely causes total blindness.

Through a period of several years, dry AMD may also progress to what’s known as late-stage geographic atrophy (GA). This is characterised by a gradual degradation of retinal cells that can cause severe vision loss. This is the most advanced form of dry AMD.

What is wet macular degeneration?

Roughly 10% of dry AMD cases can progress to wet macular degeneration. In wet AMD, new blood vessels grow beneath the retina which can cause blood and fluid to leak (hence the ‘wet’).

This unwanted new blood vessel growth may cause permanent damage to light-sensitive retinal cells, or cause a fluid build-up in the back of the eye, causing swelling within the macula. In turn, this can lead to the creation of blind spots in central vision

Wet macular degeneration risk factors and causes

The exact causes of wet macular degeneration are not yet known, however clinical research is currently underway to try and remedy this. As we have established though, wet AMD tends to develop in people who already have dry AMD.

Other factors that may increase the risk of wet AMD are similar to dry AMD, and include:

Family history

Age

Race

Obesity

Cardiovascular disease

Smoking

Wet macular degeneration symptoms

The symptoms of wet macular degeneration again are similar to those of dry AMD. However, the onset of symptoms for wet AMD can be much more abrupt and may worsen rapidly, so tend to be more pronounced.

Are dry and wet macular degeneration diagnosed differently?

Both the dry and wet forms of macular degeneration are detected using the same eye exam.

Early and intermediate stages of AMD, however, tend to show minimal signs and symptoms. As such, a comprehensive eye examination, sometimes using dilating eye drops, and a visual acuity test is normally required to detect the condition.

Here is a brief breakdown of the tests you might expect to receive with your optometrist should they suspect you are symptomatic of AMD:

Visual acuity test

This eye chart measures how well you can see at various distances.

Eye examination

Your optometrist may put drops in your eyes to dilate them and use a special instrument to examine the back of your eye for drusen — waste deposits that form under the retina and tend to appear as yellowish spots when retinal photography is carried out. The optometrist will also look for signs of fluid, blood, or disturbance to the normal retinal pigment.

Amsler grid

Your optometrist may check for changes in your central vision as a result of macular damage using an Amsler grid. Disappearance or wavy appearance of lines in the Amsler grid can indicate an onset of AMD.

Optical coherence tomography (OCT)

OCT is similar to ultrasound, except that it uses light waves, and can achieve very high-resolution images of any tissues that can be penetrated by light, such as the eyes. The images are then examined for signs of macular degeneration. OCT is especially useful in cases of AMD, or suspect AMD, as it allows the deeper layers of retinal tissue to be examined – something not possible with a traditional eye test alone.

Want to learn more? Check out our comprehensive overview on what to expect from a macular degeneration test.

Are there any tests only available at hospital?

Fluorescein angiogram

In this test, a fluorescent dye is injected into the bloodstream. Pictures are taken as the dye passes through blood vessels in the eye to diagnose any that are leaking, which might indicate wet AMD.

How is macular degeneration treated?

Currently, there is no cure for macular degeneration. If the condition is diagnosed early, however, a healthy, balanced lifestyle may help slow its progression.

Advanced dry macular degeneration treatment

For advanced dry macular degeneration in both eyes, one option to improve vision is surgery. Implanting a telescopic lens in one eye may improve both far and near vision, but with a very narrow field of view; there are some benefits such as helping to identify street signs.

Slowing wet macular degeneration progression

The following treatment options are available for wet AMD, and may help slow disease progression. If these are started early enough, however, they may go some way to actually preserving existing vision and you may even regain some lost vision.

Anti-VEGF injections

Treatment options such as injections (your eye doctor will discuss with you the different injection medications) may help stop the growth of new blood vessels by blocking the effects of growth signals. These drugs are called anti-VEGF (anti–vascular endothelial growth factor therapy) and, for each stage of wet macular degeneration, are usually prescribed as the first treatment option.

The injections are administered to the back of the eye. However, while this may seem disconcerting, the NHS have reported that in 90% of eyes treated, the injections have been highly effective6. In fact, further vision loss can be prevented if the treatment is successful and, in some cases, may support some vision recovery7.

Anti-VEGF injections are, typically, needed every four weeks. For further information check out our page on how anti-VEGF injections can help treat wet AMD and the risk factors involved.

Photodynamic therapy

In photodynamic therapy, a medication is injected into the bloodstream. A focused light from a special laser is then projected onto the eye, which activates the drug. This causes any abnormal blood vessels to close, which helps stop any leakage.

As with anti-VEGF injections, repeated treatments may be needed as the treated blood vessels may reopen over time. However, this is down to the success of the treatment.

Photocoagulation therapy

During photocoagulation therapy, a laser beam is used to seal off any abnormal blood vessels underneath the macula. However, photocoagulation therapy is generally not advised to seal abnormal blood vessels that are directly underneath the central part of the macula, or if the macula is severely damaged. This is due to the potential risk factor of further damaging the centre of the macula during the process.

Since macular degeneration doesn’t affect peripheral vision, and usually doesn’t cause total blindness, it can be beneficial to work with low-vision rehabilitation specialists to help you find ways of successfully managing your changing vision.

For more information on macular degeneration, please visit our dedicated resource. Alternatively, you can book an appointment with a Specsavers optometrist.

References

1. Leibowitz HM, Krueger DE, Maunder LR, et al. The Framingham Eye Study monograph: An ophthalmological and epidemiological study of cataract, glaucoma, diabetic retinopathy, macular degeneration, and visual acuity in a general population of 2631 adults, 1973–1975. Surv Ophthalmol 1980;24:335–610.
2. Rosenberg T, Klie F. The incidence of registered blindness caused by age-related macular degeneration. Acta Ophthalmol Scand 1996;74:399–402.
3. Evans J. Causes of blindness and partial sight in England and Wales 1990–1991: studies on medical and population subjects. No 57. London: HMSO, 1995.
4. Balatsoukas DD, Sioulis C, Parisi A, et al. Visual handicap in south-east Scotland. J R Coll Surg Edinb 1995;40:49–51.
5. Evans JR. Risk factors for age-related macular degeneration. Prog Retin Eye Res 2001;20:227-53.
6. Patient Information Factsheet, Anti-VEGF Injection Treatment. www.uhs.nhs.uk. University Hospital Southampton. 2016.
https://www.uhs.nhs.uk/Media/Controlleddocuments/Patientinformation/Eyes/Anti-VEGF-injection-treatment-patient-information.pdf (Accessed 1st October 2019).
7. Anti-VEGF Treatment. www.rnib.org.uk. Royal National Institute of Blind People.
https://www.rnib.org.uk/eye-health/eye-conditions/anti-vegf-treatment (Accessed 1st October 2019).

Ross Campbell
BSc (Hons) MCOptom Prof Cert Glauc. Prof Cert Med Ret.

Ross is an experienced optometrist, pre-registration optometrist supervisor, and lead assessor for the Wales Optometry Postgraduate Education Centre (WOPEC)… Read more