The intensity of the illumination is different in all countries due to geographical nature, proximity or distance from the equator and time zone, which will require from the designers to have more study about illumination in interior spaces. High different illumination will effect human eye and retina with severe damage, which might lead to vision loss after expose to large period of lighting might lead to injury of many different diseases. Therefore, designers should consider the lighting gradient (high/low-light in spaces) by studying how to use lighting designs to overcome this gradient. The Problem : The shortage in interior designer's study that appeared in the designs like high contrast illumination and its relationship with regional priority that impact on humans. Objectives : Reaching to specific criteria for regional priority. Arrange design study to provide a graduation between high/low-light spaces.  Methodology : analytical descriptive approach.    Results: The designer should provide a design study to identify the proper distribution of illumination intensity in different spaces. according to the activity of each space and users to achieve a comfortable sense for the eyes without any stress due to varying variations in the values of light surfaces, where the eye require a period of time to absorb and respond to the vision. When using a natural light in spaces the designer should study the long-term expose to UV radiation from the sun, as it might damage cornea and cause cataracts (white water). Therefore, must be installed suitable glass panel to control the natural illumination intensity or installed suitable curtains with transparency in the spaces. The lighting ratio between the activity space and around space should (not less than 10%). Even does not happen any temporary vision for a time up to a few seconds until the eye meets the new illumination conditions. The lighting systems contain different degrees of illumination that help the designer to control the illumination effect and provide proper distribution of illumination intensity in different spaces. Also, will help to save energy according to the Leadership in Energy and Environmental Design (LEED) system. In hot countries, the outside illumination intensity is high, when people moving from outside to inside spaces, the high different illumination intensity between spaces will affect the eye and retina with severe damage which might lead to vision loss after expose to large period of illumination. Also, might lead to injury of many different diseases. This case occurs as usual in the hotter countries.