Retinitis Pigmentosa

Retinitis pigmentosa is a disease in which the photoreceptor cells of the retina, which are important tissues for “seeing,” leading to loss of vision and even blindness. Retinitis pigmentosa is designated intractable diseases in Japan, and there is no established treatment as yet, it requires measures to minimize its influences as much as possible through the use of assistive devices and white canes.

This article describes following topics.

・Symptoms of Retinitis Pigmentosa
・Methods of examination
・Measures against low vision and the importance of follow-up observation

It is important to visit an ophthalmologist regularly so that you and your family can understand the condition and take appropriate measures.

The retina is responsible for receiving light entering the eye as a stimulus and transmitting it to the brain. It is one of the key processes by which we use our eyes to see.
Retinitis pigmentosa is an inherited disease that affects the photoreceptor cells in the retina and is designated intractable diseases in Japan. It is estimated to occur in approximately 1 in 5,000 people, with an estimated 20,000 or more patients nationwide.
The disease progresses slowly over several years to several decades and is one of the leading causes of blindness in Japan.

Pigmentation is seen as a salt and pepper pattern that appears on the fundus

Retinitis pigmentosa is characterized by the following three symptoms:

・Night blindness (difficulty seeing in the dark)
・Narrowing of the visual field
・Decreased visual acuity

The retina is able to detect light due to the action of rod cells, which detect light in the dark. Cone cells affect visual acuity and color vision. Cone cells are found in the macula, which is in the center of the retina, and there are many rod cells around the macula.
In retinitis pigmentosa, rod cells are damaged first, so night blindness is often the first noticeable symptom. As the disease progresses, peripheral vision narrows, making it easier to bump into things.
As the disease progresses and damage extends to the cone cells, vision loss becomes more noticeable.
However, the order in which symptoms appear and the rate at which they progress vary from person to person, so some people only realize they have night blindness once their vision starts to deteriorate. The time of onset varies, and although it can occur in childhood, it generally begins between the ages of 20 and 40.

Because the disease progresses slowly, it is important to have regular checkups to monitor the progress of retinitis pigmentosa.

Funduscopic examination

Funduscopic examination is a method of assessment used to examine the fundus of the eye in detail by using eye drops to dilate the pupil.
In the early stages of the disease, the retina becomes discoloured.
In the middle stage, characteristic pigmentation appears in the peripheral area, and as the disease progresses, the degeneration of the retina spreads to the central part of the retina. Eventually, the macula also degenerates, and the optic disc has atrophy and turns pale.

Fluorescein angiography

Fluorescein angiography is a procedure that uses fluorescein to take pictures of the fundus of the eye. A yellow dye that fluoresces under cobalt blue light is injected intravenously. The fluorescence is more intense in areas with advanced retinal atrophy and is used to monitor the progression of the disease.

Visual field test

To check how much your field of vision has narrowed, you can take a test in which you press a button when you see a small light. With retinitis pigmentosa, your field of vision may become ring-shaped or partially lost. As the disease progresses, your field of vision narrows toward the center, as shown in the image below. This is called centripetal visual field constriction.

Electroretinogram

When light is absorbed in the retina, an electrical signal is generated, and an electroretinogram is a test that examines the response of electrical signal using electrodes placed on the cornea.
In the early stages of the disease, the response of electrical signals is weak, and in the middle or later stages, there is almost no response at all.
The test is performed under ophthalmic anesthesia and with contact lenses specially designed for the test, so it is principally painless.

Fundus autofluorescence

When there is a lot of a pigment called lipofuscin in the retina (retinal pigment epithelium), images appear brighter. However, as the disease progresses and the retinal pigment epithelium becomes damaged, the amount of lipofuscin decreases and images become darker.
While fluorescein angiography requires the injection of a contrast agent, fundus autofluorescence is a noninvasive procedure that is less stressful on the patient’s body.

There is no established treatment to restore retinal function once lost or to halt the progression of the disease.
Symptomatic treatments for retinitis pigmentosa include light-blocking glasses and a variety of assistive devices designed for people with low vision.

Low Vision Care

Low vision is a condition in which a person is not blind, but has extremely poor vision. First of all, it is important to understand the characteristics of retinitis pigmentosa, in which the field of vision gradually narrows and vision deteriorates, and to understand the progression of the disease yourself.
Then, in order to make effective use of remaining vision and visual field, measures are taken such as using various assistive devices or white canes.
Even if vision has deteriorated significantly, it may be possible to read and write by using a loupe or magnifying glass. Using voice software to access the Internet and e-mail is also effective.

Night vision support glasses are effective in improving night blindness symptoms

Regular visits to the ophthalmologist

Even if no established treatment is available, regular visits to an ophthalmologist once or twice a year are still recommended.
This is a good opportunity for you and your family to be aware of your current vision, monitor the progression of the disease, and check for complications. Retinitis pigmentosa is easily combined with cataracts and diseases of the macula (center of the eye). If complications are detected early, regular checkups can prevent vision loss.
It also allows you to ensure that you are properly applying for disability benefits in Japan.

Retinitis pigmentosa is known to be caused by a genetic defect, but there are over 50 different types of defects that can cause the disease.
Approximately half of patients develop the disease due to heredity, so if there are multiple family members with retinitis pigmentosa, it is best to assume that there is a high possibility of developing the disease.
However, it is not necessarily inherited, and approximately half of patients have no known family members with the same disease.

Retinitis pigmentosa is designated intractable diseases and is covered by the medical expense subsidy system established by the Ministry of Health, Labor and Welfare, Japan.
Depending on the degree of visual acuity and visual field impairment, it may be possible to be certified as a person with a physical disability and receive various types of support, so it is advisable to consult with an ophthalmologist.

How does retinitis pigmentosa affect my vision?

Usually, the first symptom is night blindness, which makes it difficult to see things at night or in dimly lit indoor places. This is followed by a gradual narrowing of the visual field, with the area of vision decreasing from the periphery to the center.

What are the latest treatments for retinitis pigmentosa?

Gene therapy, retinal regenerative medicine, and retinal implant are being studied as promising future treatments.
In Japan, research has also begun to supplement genes to produce more neuroprotective factors in the eye so that photoreceptor cells in the retina can live as long as possible. Clinical trials of retinal implants or regenerative medicine to photoreceptor cells that have atrophied or degenerated retinal pigment epithelial cells have also begun, and the results of this research are expected to be significant.