Nature has created a very useful and balanced environment for all the living things to live in a peaceful and joyful world ensuring their health at the maximum. Natural environment is the key to the survival of the various species and a slight change in any of the components of an environment proves fatal to the organisms living in it. In biological terms a natural befitting environment in which a number of species live together while co-operating and coordinating with one another is called an ecosystem and the study of relationship between an organism and its environment is called Ecology.

Composition and working of Human Environment

Same is the case with man whose natural environment is “the earth” and its surroundings where he lives. Human ecosystem or environment has two main factors; i.e. biotic factors and Abiotic factors. Biotic factors involve only the living factors whereas Abiotic factors are the non living factors both of which are responsible for the normal working of an ecosystem. If there keeps a fine natural balance between the two types of factors, all goes well for the organisms and they live on happily. But on the other hand, if any of the components is not working properly, the whole ecosystem gets disturbed and the organisms can never lead a normal happy life in such an abnormal ecosystem. Then it becomes very much important to set right the ecosystem as early as possible by removing the causes of disturbance so that the normal living of the organisms may be ensured. Such is the importance of an environment for a species.

continue reading Guide to Environmental Health and Safety

WHAT IS LASER EYE SURGERY?

Refractive or Laser Eye Surgery (LES) is a laser reshaping of cornea thus changing its focusing power (1), (pictures 1,2). For patients with moderate refractive errors this ambulatory procedure is a quick way to get free of glasses or contact lenses.

Picture 1. Eye doctor performing laser eye surgery
(source: whmc.af.mil)

COST OF LASER EYE SURGERY 

The cost of LES can vary widely but it is rarely under $1,000 per eye (2).

REFRACTIVE ERRORS TO CORRECT WITH LES

The light from an observed object penetrates through the cornea, lens and viscose liquid of the eye globe, refracts, and focuses on retina as an image. In farsightedness - hyperopia the eye globe is too short, and since the lens cannot refract the light from near objects enough, the light will fall behind retina and give a blurred image. In presbyopia (farsightedness of the aged) the lens becomes rigid and cannot refract the light from near objects efficiently, so it will  again focus behind the retina. In nearsightedness (myopia), the eye globe is too long and light from distant objects will focus in front of the retina, so images of distant objects will be blurred. In astigmatism blurred vision is caused by irregularities in the corneal or lens shape (3). All mentioned refractive errors can be corrected with laser eye surgery.

continue reading Corrective Laser Eye Surgery