What is the proper procedure for testing visual acuity?

The visual acuity test refers to a routine part of a general eye examination, mainly to observe if there is an issue with vision or a change in vision. The test can be performed in a school, in a health care provider's office, workplace, or somewhere else.  

For the commencement of the test, the individual is instructed to remove the contact lenses or glasses and sit or stand 6 meters from the eye chart, and he or she is instructed to open both the eyes. Then the individual is asked to cover one eye with a piece of paper, with the palm of the hand, or with a small paddle while one reads out loud the smallest line of letters, which he or she can witness on the chart.  

This test is done on each eye, that is, each at a time. If required, it is repeated while one wears the contact lenses or glasses. One may also be instructed to read the numbers of letters from a card held 14 inches from the face, this will test the near vision.  

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.