A D V A N C E L O W V I S I O N A N D R E H A B I L I T A T I O N

Eccentric viewing

What is Eccentric viewing ?

Eccentric viewing is a technique used by people with central vision loss.

Also called Preferred Retinal Loci (PRL),

it is a method by which the person looks slightly away from the subject in order to view it peripherally with another area of the visual field.

By using the ( Best Retinal Area ) BRA

What is central scotoma?

Most prevalent field defect in low vision patients due to age related -maculapathy

You have a central vision loss when your visual acuity is less than 0.1.

Ten degrees out, the visual acuity is 0.05.

You cannot see straight ahead, and when you are unable to use your direct vision,

you are unable to fixate and then you have to learn to see from “sideways”. We call this method “eccentric viewing”. “Eccentric fixation” describes the skewed vision

Symptoms determine function more than diagnoses

The symptoms are more important than the diagnosis.?

Yes..

This is because, for example, different causes of macular degeneration different diagnoses can have similar symptoms and the symptom is more important when choosing the right method to read, look and see at far distance.

The definition of eccentric viewing (EV) is using non-foveal preferred retinal loci (PRL) for viewing.

The purpose of the present study was to investigate the clinical effect of EV training for low vision rehabilitation in patients with central scotomas.

This is similar to looking slightly away from an object at night in order to see it better.

By doing so, the viewer is allowing the rod cells in the peripheral field to take over for the cone cells in the central field. Rod cells are better for viewing in dim light than are cone cells.

The biological task

It requires the eyes and the brain to learn a new method of seeing, which means developing new habits and skills.

Training

The question is if eccentric viewing is something you teach yourself or if it is a method that you need help practicing ?

It is important to remember that training in eccentric viewing will not improve the condition of the retina.

The patient may feel that vision has improved as a result, but that is simply because existing vision has been maximized.

The answer is quite simple.

It depends on how easy it is for you to learn and the factors that come into play in your individual case.

Some people find it difficult to adapt to the new situation and technology.

In any case, it is necessary to practice reading with eccentric viewing because it requires a new behavior other than just seeing in the periphery of the retina where the density of cones are much lower than

Step by step

Is visual acuity lower than 0.1 with the best-corrected visual acuity (BCVA)?

Computerized eye test charts are frequently used, such as Text Chart Xpert,

where it is possible to use larger optotypes at a shorter distance and calibrate the distance in relation to the size of the optotype.

Measure the visual field according to Goldmann (Figure 2) and ensure that the central vision loss – the scotoma – is carefully measured with different isopters (light points of different intensities) so that you can see where the patient sees and does not see in relation to different degrees and sizes of texts and images.

It is also possible with the patient to measure the central loss using the Amsler grid.

The BRA test is made of plastic and you can fill in and erase the areas of loss that the patient produces when he or shedescribes what is in the middle

Ask the patient to look at your face using the new gaze direction. Check if the direction is as good for identification/recognition as it is for reading.

Ask the patient to look at your hair, chin and both ears by focusing on these with his or her central vision, namely, placing the scotoma there and then asking: Where do you see my eyes the best?

When do you see my hair? My chin? Right or left ear? This is something you can do both before and after the BRA testing.

Measure the need for magnification

Check if the estimated magnification is sufficient by putting the lenses in a test eyeglass frame and using the near vision chart. It is often appropriate to over correct so that the patient can read fluently and not have to stumble through the text. Usually, a person needs different magnifications for different text sizes.

Measure the number of letters per fixation in Read More (2008) or other materials where you can also practice reading with fixations or help lines and texts with different amount of magnification

These techniques include

tracing,

identifying cards, and other methods used to improve reading and writing skills.

Example device: Telescope scanning – a technique is a relatively simple method of enabling the partially sighted

procedure

Patient wear low power telescope

Look a small object and signed at the far end of the room not less than 15ft or 4cm

Object have an angle of 10 min arc.

The patient is move his or her eyes around until the area of the retina that provides the best resolution is found.

Advantage

The patient helps to locate the retinal area with best acuity.

Remember ... The amount of the eccentrically is dependent on the location of the island of seeing.

Mirror

Patients with right hemainopsia have been prescribe a mirror attached to the nasal eye wires and angled before the right eye

Mirror –blocked the out most of the left visual field of the right eye.

Replacing the with a view of the right VF.

Effect: a. Patients learn to suppress mirror image

b. The patients must make gross eye and head movements to actually look at an object of interest in the blind spot.

Mirror and prism

Are also use in the field enhancement devices . Bilateral hemianopic patients who read Chinese.

Example : clip on dental mirror – use for the right spectacle lens for right homonymous hemianposia

“If you have a problem and deny it, you REALLY do have a problem. . . . But when you get around to accepting your situation, you can accomplish almost anything – just like anybody else.”

From Täppas Fogelberg’s preface to See Bad Feel Good (2003).

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