Week 8: Curvature of the Lens

Around 75% of Americans use corrective lenses to aid in fixing refractive errors such as myopia (nearsightedness), hyperopia (farsightedness), astigmatism, and presbyopia. With all of these refractive orders being unique to each individual, each corrective lens is custom made to fix the refractive error. This is the biggest reason for people with a astigmatism and myopia can not switch glasses with another individual. How are these lenses made to bend light so that the focal point is near the fovea of the eye?

Concave Lens

Myopia is corrected with what is known as a concave lens, which bends light outwards that comes through the lens. This lens is also known as a divergent lens since it spread out light rays. Examples of it's uses other than eyeglasses are binoculars, telescopes, and microscopes (these three objects also use convex lenses also). Examples of objects that are purely concave are flashlights, lasers, and peepholes. The interesting part about the flashlight is that the convex lens allows for those diverging rays so that the radius of the light is increased.

Convex Lens

Hyperopia and presbyopia are corrected with a lens that curves which is called a convex lens or a converging lens. The light is refracted so that rays bend inwards. This type of lens allows for magnification to have objects appear closer than they appear. Examples of this lenses use would be microscopes, telescopes, cameras, and binoculars.

Astigmatism

Astigmatism is corrected by a lens that have different radii of curvature to correct for the refractive error. This simply means that the lens could be convex in one place and concave in another to take multiple focal points into one on the back of the eye. This disorder is due to an incorrect curvature of the lens or cornea.

Glasses are not just designed according to the lens shapes that are mentioned above. Lenses are made using convex and concave shapes which is known as a ophthalmic lens/glasses. The front part of the glasses  that is further away from your eye has the convex shape. The back of the lens (one closer to the eye) has the concave shape. Its the difference in curvature between the from and the back the lens that provides the corrective power.

Blackboard Optics - Concave and Convex Lenses from Michael Thorpe on Vimeo.

Sources:

• Wikipedia: Lens Profile
• American Optometric Association: Astigmatism
• eHow: Concave Lens Uses
• eHow: Convex Lens Uses
• Universe Today: Concave Lenses

Week 7: History & Making of Eye Glasses

History of Eye Glasses

Making of Eye Glasses

In the present century, eyeglasses are made using plastic, due to the durability and lightweight as compared to the use of glass. Around 20% of glasses are made using actual glass in the making of eyeglasses, while the rest is polycarbonate plastic. The process of making eyeglasses is relatively the same between glass and plastic. The video below describes how polycarbonate glasses are made, the video ends at 5:21 for the description of how glasses are made. As a side note I have also found 60 minutes report about the price glasses frames and why they are so expensive: Sticker Shock: Why are glasses so expensive? This is a great video that describes why glasses are so expensive.

Week 6: Lesson 3 Eye Glasses Cont.

Once I began college I realized that I needed eyeglasses (spectacles) to get the needed notes within auditorium type classrooms. I knew for sometime that I needed glasses, but denial of my failing eyesight prevented me from visiting the optometrist. It wasn't popular culture that prevented me from getting eyeglasses, but the fact that I wanted to be the only brother without corrective lenses. Once I visited my optometrist I learned that I was nearsighted and needed corrective lenses to focus on far away objects.



Vision problems plague 60% of the population in the United States. Many vision problems like myopia, hyperopia, astigmatism, and presbyopia can be prevented with the use of corrective lenses. Through mainstream media eyeglasses were seen as the iconic symbol for the nerd, as with Steve Urkle, Peter Parker, and Leonard. The 21st century has changed the iconic symbol to a fashion statement in which many people wear glasses that don't require a prescription.




Fraser Eye Care Center: Myopia, Hyperopia, Astigmatism, & Presbyopia

Myopia (Nearsightedness): An individual is able to see objects up close, but is unable to focus on far objects. The shape of the eye is elongated compared to a normal eye.

Hyperopia (Farsightedness): An individual is able to see objects far away, but is unable to focus on near objects. The shape of the eye is shorter compared to a normal eye.

Astigmatism: An individual has blurred vision due to the cornea or lens is irregularly shaped which causes refraction problems.

Presbyopia: As individuals reach of age of 40 the supporting structures of the lens wear down, which causes similar symptoms of a farsighted individual.

CDC: National Data Vision Statistics - If you click on the National Eye Institute/Statistics and Data website it will give you charts and tables that describe vision problems from 200 to 2010.
CDC: West Virginia Vision Statistics - This site does contains the same information but focuses on 2007 West Virginia data.

Research:

Using the information that you have learned about the eye and the disorders that can affect the eye, you will need research corrective lenses and statistical data for nearsightedness and farsightedness. You will need to create a presentation (power point, prezi, and others) that covers the checklist.

1. Presentation
1. Minimum of eight slides
2. Include pictures or video
3. Slide etiquette: use pictures, limited wording, title for each slide, able to read
4. Last slide is bibliography (MLA format)
2. Content
1. Describe nearsightedness and farsightedness and provide an example
2. Describe the corrective lenses need to fix farsightedness and nearsightedness
3. Provide statistical data for vision problems

Week 6: Lesson 3 Eye Glasses

As I was searching the internet for the history of eyeglasses, I came upon an interesting article from Popular Science Magazine: Are Your Eyes Right?. Read through pages 120 to 122 and answer the questions related to the article. This article was printed during the time in which the United States was involved in World War 2.

Questions

1. Based on what you have read, how would people react to this article in 1944? 
2. Based on what you have read, how would you react to this article today?