Hereditary disease, characterized by night blindness and tunnel vision

RETINITIS PIGMENTOSA ("RP")

 
INTRODUCTION: HOW DOES AN EYE WORK?

The retina is the most light sensitive zone in the eye. It can be compared with a film in a camera. In the retina are the light sensitive cones and rods. The cones see contrast and colors. We use them while reading ; they determine the acuity. The rods provide opportunities to see in the dark. They don't give sharp contrast, color or sharp vision.
The cones are located in the central part of the retina and reduce towards the sides of the retina. The rods are divided over the whole retina, but less in the centre.
When your read a book or look at something, this happens with the cones. A star or recognize light in the dark happens with the rods. Problems with the side vision ("visual field"), indicate problems with the rods. The visual field of a healty person is 180° (while using both eyes) and 120° (while using only one eye).

COMPLAINS BY RETINITIS PIGMENTOSA

 NIGHT BLINDNESS 

 By RP the rods gets affected, those who serve to see in the dark.So RP patients suffers to get orientaded in the dark.
This means that you only see lighting + that you only slowly get used to the weak light while entering a dark room.
You will need good allumination for reading.

RESTRICTION OF VISUAL FIIELD

there occurs a degeneration of the rods. The side vision get attacked as first and reduce progressive: in the end fase can the visual field can significantly be reduced (still 5 a 10 degrees left, where 180 degrees is normal). The central part stays longer unattached, in some patients a whole lifetime. The central part is needed for details, colors, reading,... The side vision is neede to get orientated in space. The degeneration can occur in a further fase also in the cones. This leads to malfunctioning of seeing contrast.
If the sharp sight reduces, you'll expierence trouble while reading (these can not be solved with normal reading glasses).

This means that :
- You see just a part of the environment
- You can only compose a total image by turning your head and moving your eyes
- You slowly read and you can see little characters at the same time
 
GLARE 

A RP-patient expierence that it takes a while before he/she can see normal again after glare. RP-patienten wear mostly very dark sunglasses (even they can see well in the dark !). In this way you avoid glare by strong light.

This means that :
- You wear sunglasses very often, even when it's rainy
- You can see contours by normal illumination
- You have trouble reading texts on shiny paper or paper with low contrast (pencil)

Special sunglasses with a blue filter can help this. If that's so, it gets refunded. Yellow glasses can give a better night vision!

REM: Beside, an RP patient can be “myopic”,  “hypermetropic” or “astigmatic” like everbody else and therefore need to wear their glasses.
Cataract (=cloudy lens), wich everybody gets at an higher age, occurs earlier in RP-patients (sometimes before 3O to 40 years !!) and can give extra blinding. This can be resolved relativly easy (cfr infra).


DIAGNOSE

The ophtalmologist can diagnose easily, by looking in the eye and examine the retina: he sees a lot of black spots at the side of the eye, narrow arteries and a orange/yellow optic nerve (optic nerve is normally yellow). To confirm the diagnose the electric efficiency of the eye may be controlled in a university hospital ("elektrofysiologic examination): It's a clear diagnose when the eye works normal in light, but significantly worsened in a dark environment. ("the photopic ERG is spared, while the EOG and scotopic ERG is affected"). Also the adaptation to the dark can be measured and is very disturbed in RP-patients.

CAUSE

RP is the most frequent form in the group of retinal dystrophies (= early degeneration). There exsist two hereditary forms:
a common sporadic form ("autosomal recessive"), who is worst (faster and stronger vision deorientation) and a family occuring form ("autosomal dominant") who is less worse. What exactly goes wrong is well known:  with aging, cells get replaced, like thosewho peels from the skin. In the retina and brain cells get also replaced ; in RP the cells becoming smaller in number and they don't get replaced anymore. In many cases of RP, the cones remains the longest.. Eventually the cones can degenerate also and can lead to full blindness.

THERAPY?

RETINITIS

There is untill today no recognized medical method, who can stop the worsen of RP or can cure the disease. A few tools can be tried, bvb. contrast-enhacing sunglasses (refunded by health care) / yellow night glasses to avoid blindness / loupes / reading with good light / sitting closer to your TV (this can't harm the eyes!!)

REFRACTION-FAULT (myopia / hyperopia / astigmatism) : glasses can help

EVENTUAL CATARACT
   
Retinitis pigmentosa can give acceleration in cataract (= cloudy lens), with additional foggy vision as result.
A cataract operation can solve this, but doesn't change anything about RP itself!


DRIVERS CAPABILITY

You may drive with the car, for private transport, if your vision is more than 7/10 and your visual field is over 120°. 
The ophtalmologist will write you a certificate that your riding is limited from one hour after sunrise untill one hour before sunset, because of dark adaptation disorders!

ADRESSES  

Secretary of the Flemisch departement /redactieadres"RP VANDAAG" en contactadress for  
parents of children with RP
Luc en Greet Vandevenne-Wouters
Kattelijnestr 39
3350 Linter
tel 016/789904

 
Nationaal voorzitter van de Belgische Retinitis Pigmentosa Vereniging 
Luc Hendericks
Stefaniestr 25
2018 Antwerpen
tel 03/2381802

Voorzitter van de Vlaamse afdeling van de Belgische Retinitis Pigmentosa Vereniging  
Christa Huysentryt
Kortrijksestr 168
5801 Heule
tel 056/352846    

Retinitis Pigmenosa vereniging Nederland 
Secretariaat:Valreep 15
1186 ZH Amstelveen
tel 020-641759