A sodium-vapor lamp is a gas-discharge lamp that uses sodium in an excited state to produce light, which has two varieties of such lamps: low pressure and high pressure. High-pressure sodium lamps have a broader spectrum of light but poorer color rendering than other types. High-pressure sodium (HPS) lamps are smaller and contain additional elements such as mercury, and produce a dark pink glow when first struck, and an intense pinkish orange light when warmed. High pressure lights can affect the first layer in eyes and the back of eyes. All these may be easy to cause astigmatism, double vision and blurry vision. So you need to leave HP lights alone and read in a soft but bright light. HP lights has a deep effect on eye sight. Be careful.
Yes, the HPS light is bad for eyes. HPS is the short term of high pressure sodium. It is popular used as street light for its efficient brightness. It emits a lot of heat at the same time. If staring at the HPS lights for a few seconds, in a close proximity, it could cause permanent damages to eyes, like bleaching retina. So if you could avoid, you should not to look straightly at these bulbs. If you do need to do so, wearing protection like sunglasses is better.