A Personal Work Sample

I have decided to put in one of my ACE assignments as my personal work sample and improve it. Although I was awarded marks that were satisfactory, I thought that I could further improve this ACE in many other ways. So, this is one of the ACE I embarked on, "Refraction in our eyes".


Firstly, I explained how our eyes work. As light from the object we are looking travels from air to our cornea, it refracts, and actually, the largest percentage of refraction is done by the cornea, 80%. The other 20% is done by our lenses. After this, the refracted light is focused on the retina, which is the tissue that lines the inside of the back of the eye. In the retina, there are photoreceptors, which consists of cones and rods. Cones are sensitive to colour while rods control our black and white vision in low-light conditions. Finally, these images are transmitted through the optic nerves to our brain for interpretation.

Now, I will explain the refractive errors our eyes may have, one of which is far-sightedness. As usual, the light is refracted as it passes through our cornea and lenses, and is focused on the retina but in the case of people with far-sightedness, the light that is refracted is not focused before it reaches the retina, which causes a blurred image.


In other cases, there are people with near-sightedness. Instead of the light focusing on the retina, or focused only after it reaches the retina, the light is focused even before it reaches the retina. This causes a blurred image as well and is what we call near-sightedness.


Reasons for refractive errors

Far-sightedness

The three reasons for far-sightedness are short eyes, flat curvature of lens and irregular shape of our cornea. Short eyes will result in the light being unable to be focused on the retina by the time it reaches it. Flat lenses and irregular shape of corneas will distort the angle of refraction of the light that enters our eyes, causing the same effect of having short eyes.

Near-sightedness

The three reasons for near-sightedness are long eyes, steep curvature of lens and irregular shape of cornea. Conversely, long eyes will result in the light being focused before it reaches the retina. Similarly, steep lenses and irregular shape of corneas will distort the angle of refraction of the light that enters our eyes, causing the same effect of having long eyes.

As we evaluate the causes of refractive errors, we can conclude that there are 3 factors that causes these problems, our eye length, the curvature of our cornea and the curvature of our lenses.


Solutions to these problems

A very advanced way of solving these eye problems is undergoing LASIK surgery, which stands for LAser in SItu Keratomileusis. It consists of five steps.

Firstly, a suction ring is placed on the eye. Then after, a microkeratome is used to cut a partial flap in the cornea with uniform thickness. The flap is then folded back, exposing the middle area of the cornea. Laser pulses are then sent through the excimer laser onto the middle area of the cornea. After this is done, the flap is then replaced and the surgery is completed.

What the LASIK surgery actually does is to correct the shape of our lens, in relation to the refractive errors we are facing, so that our lens will not cause these problems anymore.

Another solution to this problem is using contact lenses. Concave lenses would solve the problem of near-sightedness while convex lenses would solve the problem of far-sightedness.

Near-sightedness (Note that the dotted rays are the rays that causes refractive errors while the non-dotted ones are the rays that undergo refraction through the lenses.)


Far-sightedness (Note that the dotted rays are the rays that causes refractive errors while the non-dotted ones are the rays that undergo refraction through the lenses.)




Reflections
This ace has reminded me of the importance of not leaving out any single detail when I am doing a project or an assignment, for they may mean a lot. For example, while doing this ACE project initally, I left out the explanation of how does LASIK surgery and contact lenses actually work, and this are actually the areas I can work on. I hope that I can learn from this ACE project and carry this attitude whenever I am doing ACE projects or assignments.

Sources --> Google Images
--> http://www.lasersite.com/lasik/index.htm
--> http://www.allaboutvision.com/eye-exam/refraction.htm