According to the Oxford Dictionary, the term ‘technology’ can be defined as ‘the application of scientific knowledge for practical purposes’. The Second Industrial Revolution (1870-1914) introduced a rapid development in technology and today we are constantly surrounded by it. Due to a wide scope of technology available, our society has become greatly dependent on it for communication, safety, efficiency and entertainment.
Children used to spend their leisure time outdoors; with friends or playing sport. But this exponential boost in technology has culminated a new generation of children and young adults who have grown with updated gadgets and devices. Today, the television ...view middle of the document...
But many scientists and experts are unclear whether it really causes damage to the eyes. But it is known to us that focusing on objects for prolonged periods of time can cause eyestrain.
Eyestrain is a temporary problem caused by extensive use of the eye muscles often from staring at an object of a short distance for too long. Activities which can easily induce eye strain are driving, reading, watching television and more. The symptoms which follow include:
¬ Watery itchy eyes
¬ Blurred or double vision
¬ Increased sensitivity towards light
¬ Focusing difficulties
Our eyes are able to focus on both long and short distance objects from the use of the ciliary muscles contracting and relaxing. When light from a close range hits the eye and refracts; the ciliary muscles tighten the lens, rounding the shape. If the ciliary muscle is kept tense, the inner eye muscle tightens and this leads to eye discomfort and irritation (eye strain).
Snellen Eye Chart
The Snellen Chart was created by Dr. Hermann Snellen in 1862 and today is used by eye care professionals to measure visual performance. The chart is constructed of eleven lines of block letters, each subsequent line has letters which decreases in size. The letters are intended to be read with one eye open and the smallest row that can be read correctly demonstrates the eyes acuity.
The ‘letters’ on the eye chart are properly known as ‘optotypes’ and are not letters from an ordinary typography font. These symbols or optotypes hold certain characteristics including:
¬ Thickness of the line equals the thickness of the white spaces between the lines
¬ Height and width of the optotype is five times greater than the thickness of the line
The Snellen Chart also only Sloan letters (C, D, E, F, L, N, O, P, T and Z). To measure one’s visual acuity, with the Snellen Chart, one must stand six metres from it.
Visual acuity is measured in a fraction, the numerator is the distance from the chart (in metres) while the denominator stands for the size of the font (in M-units). Standard vision is also known as 20/20 vision, this shows what a normal human should be able to see 20 feet from the eye chart.
Pelli-Robson Contrast Sensitivity Chart
The Pelli-Robson Chart was developed by Denis...