Light and glare symptoms will vary depending on the degree of damage. In the later stage of RP the patients experience visual field loss, decreased central vision might lead to the macula and partial blindness. It has been reported that fifty-two percent of children in the developing countries, who complained of night blindness, had ocular signs of vitamin A deficiency.
The night blindness is significantly higher among the male children aged 25 – 59 months and found to be dysenteric and undernourished, did not consume vitamin A containing foods and were not breastfed. World Health Organization estimated that more than 124 million children are vitamin A deficient and that many young children go permanently blind because of lack of minute amounts of retinal in their diet. Also it is observed a strong association between diarrhea and vitamin A deficiency, although it is not clear whether diarrhea precipitates vitamin A deficiency or vitamin A deficiency predisposes diarrhea or other infections in marginally nourished children.
Night blindness is caused by a deficiency in vitamin A that is needed to produce the pigment found in rods (Rhodopsin). Rhodopsin is the pigment responsible for absorbing the photons of light energy. So the rods are less sensitive because they exhibit a reduced rate of regeneration of rhodopsin following exposure to light, i.e. delayed dark adaptation. However, some individuals have Congenital Stationary Night Blindness – a decreased sensitivity to light. One is born with this disorder (a genetic mutation) and it will neither improve nor get progressively worse.
PREVENTION AND CARE: Night blindness can be prevented by giving high potency vitamin A capsules to chidden or making them consume foods containing vitamin A like dark green-leafy vegetables, yellow fruits, cow milk and eggs. Night blindness may be dealt with by increasing light levels inside and outside the home. Supplemental task lighting is usually helpful to RP patients. In some cases where night travel is frequent, night scopes can be used.
These scopes are similar to those infrared systems used by the military in Operation Desert Storm. Low vision eyewear and magnifiers may be employed successfully for certain patients. Visual field awareness systems may be employed to aid loss of peripheral vision. Reverse telescope or amorphic lens work for many patients. In cases of decreased visual acuity and visual field loss, prisms may still be employed. These include the Inwave Retinitis pigmentosa lenses, the Gottlieb Visual Field Awareness System and Press-on Visual Field Prisms. Prisms can be employed earlier than trying reverse telescopes. If a patient is unable to be helped by conventional low vision systems, electronic reading machines, talking books and reading radio may also be helpful.