This video can explain what dry eye is:
http://allaboutdryeye.com/
MACULAR DEGENERATION:
There are two types of age-related macular degeneration, the "dry" type and the "wet" type.
The "dry" type usually has a slower progression. The "wet" type is a faster progressing disease. New blood vessels grow in the macular region causing leakage, bleeding, and scarring in the macular region. unfortunately there is no cure for Macular Degeneration. for further information click on the following link http://www.ahaf.org/macular/about/maabout.htm
Click on the following link to learn more about cataracts: http://www.aoa.org/patients-and-public/eye-and-vision-problems/glossary-of-eye-and-vision-conditions/cataract?sso=y&ct=52517554511f786440c4296428359ac7c67d16852c17f6220a0f0671c799c4edb98e220956455bb026fef1b862ca54679398342687463e91b137a52fbf424812
The following links can also be useful:
http://www.nei.nih.gov/healthyeyes/
http://www.nei.nih.gov/glaucoma/
http://www.nei.nih.gov/diabetes/
http://www.nei.nih.gov/lowvision/
http://www.nei.nih.gov/sports/
GLAUCOMA:
Glaucoma is a condition where the pressure in the eye increases to an unacceptably high level, thereby causing damage to the optic nerve and as a result, loss of vision. Click on the following link for more information
http://www.glaucoma.org/learn/index.php