We use cookies to give you the best experience possible. By continuing we’ll assume you’re on board with our cookie policy

Optics – The human eye and coomon defects Essay Sample

The whole doc is available only for registered users OPEN DOC

Get Full Essay

Get access to this section to get all the help you need with your essay and educational goals.

Get Access

Optics – The human eye and coomon defects Essay Sample


The mammalian eye could be regarded as a miracle of evolution. In order to produce an image the eye has to act as an Optical refracting System (to focus a sharp image) and a Photo Detector (to analyse the image and send information to the brain). At the front of the eye is the optical system, made up of the transparent curved Cornea and the adjustable biconvex Lens. The photo detector is the layer of light-sensitive cells at the back of the eye, called the Retina. The amount of light entering the eye is controlled by the Iris. Sharp focusing is achieved by altering the shape of the lens. The shape of the lens is controlled by the ring of ciliary muscle which runs round the outside of the lens.

Defects in the eye:-

1. Long Sight (Hypermetropia)

In this condition we can see distant objects more clearly that ones that are nearby. This is usually because the cornea is not curved enough, which reduces the angle of refraction, and the lens cannot accommodate sufficiently to bring the diverging rays from near objects into sharp focus on the retina.

2. Short Sight (Myopia)

In this condition near objects are clearly seen, but distant objects cannot be brought into the focus. It happens when the cornea is too curved; the light from distant objects is refracted too much and comes to a focus in front of retina.

3. Astigmatism

If the cornea is curved in an uneven manner, it will refract light that enters the eye in different planes to different extents. The eye will focus light in some planes better than others (i.e. verticals might be in focus, but horizontals not)

4. Presbyopia

This is the natural reduction in the lens’s accommodation power with the age. (Accommodation is the process of changing the shape of the lens in order to focus the sharp image on the retina.)


* Long Sight (Hypermetropia)

The situation can be corrected by placing a converging lens (convex lens) in front of the eye (by means of spectacles of contact lenses). In extreme cases laser surgery can be used to correct the shape of the cornea.

* Short Sight (Myopia)

This situation can be corrected by placing a diverging lens (concave lens) in front of the eye. In extreme cases laser surgery can be used to correct the shape of the cornea.

* Astigmatism

This situation can be corrected by using a cylindrical lens (i.e. one that only curves in one plane)

* Presbyopia

This can be corrected by using bifocal lenses, which have different curvatures in different regions. While looking at close objects we tend to look down, so the lower region of the lens is manufactured to correct for defects in short sight. When we look at distant objects we tend to look up, so the upper part of the lens caters for long-sight problems.

We can write a custom essay

According to Your Specific Requirements

Order an essay

You May Also Find These Documents Helpful

Peculiarities of various assignment types

The educational process is diverse and full of interesting writing tasks which help students develop their academic abilities. Different assignments types are created by professionals in order to enhance students’ level of analytical, critical and writing skills and to vary the learning process. As a student, you will encounter numerous tasks of diverse complexities throughout your student life. Sometimes, maybe, too complicated! They have different peculiarities, structural...

Making decisions in health and social care

Critically analyses the concepts, features, and importance of costs and accounting in making decisions in health and social care Cost accounting is a method used in accounting to capture a company’s or organisation’s production costs. It assesses the input costs of every step in production, fixed costs like depreciation of capital equipment. Cost accounting measures and records costs individually then compare the input results via...

Сhildren development

Physical development 7-12 years By the age of 7 a child enjoys things such as bike riding and rollerblading they are now able to tie and untie shoelaces without adult help, they are now starting to understand what rules are and are able to follow simple rules. At 8-12 years a child improves the physical skills that they have already developed and start to see...

Forex international trading market

Introduction Forex exchange is on the rise in Namibia; resulting in more people wanting to learn how to trade to try to increase their income so that they can enhance their standard of living. Forex Foreign exchange identifies the process of converting domestic currency into international banknotes at particular exchange rates (Bofah, 2017, para.1). As the number of foreigners in Namibia is increasing, more Namibians...

Aristotelian idea of God

This image produced in 1544 shows emerging's of the Judeo-Christians and Aristotelian's traditions. Aristotle was very interested in the idea of motion and said “The world is in a constant state of motion and change”. An example of how the world is changing is the growth of trees and plants. Aristotle believed in a prime mover, which is the being which creates change in the...

Get Access To The Full Essay
Materials Daily
100,000+ Subjects
2000+ Topics
Free Plagiarism
All Materials
are Cataloged Well

Sorry, but copying text is forbidden on this website. If you need this or any other sample, we can send it to you via email.

By clicking "SEND", you agree to our terms of service and privacy policy. We'll occasionally send you account related and promo emails.
Sorry, but only registered users have full access

How about getting this access

Become a member

Your Answer Is Very Helpful For Us
Thank You A Lot!


Emma Taylor


Hi there!
Would you like to get such a paper?
How about getting a customized one?

Can't find What you were Looking for?

Get access to our huge, continuously updated knowledge base

The next update will be in:
14 : 59 : 59
Become a Member