Cataracts: The word cataract derives from the word waterfall or cloud. It's a clouding of the lens inside the eye behind the pupil so when it's significant you'll definitely notice decreased vision. The clouding is related to age and UV light so most everyone will eventually get a cataract if they live long enough. The average American gets cataract surgery in their early 70's. Cataract surgery is the most performed surgery of all surgeries. It's usually very successful including after cataract surgery you often don't need glasses.
Glaucoma: Glaucoma is damage to the optic nerve due to fluid pressure inside the eye. It causes gradual loss of peripheral vision initially but by the time it's noticeable it may be hard to stop the progression and blindness may result. Detection and treatment was not common as little as 40 years ago, but with advances in medicine most glaucoma is now detected and treatable. Basic treatment involves one drop in the eye at night. More medicine and even surgery can be used as treatment if needed. 2% of the population gets glaucoma and it does have hereditary and race (African American) associations.
Macular Degeneration: (AMD, age related macular degeneration) The retina is the screen in the back of the eye that we use to see. The macula is the center of that screen. With age and other factors, many people's macula start to degenerate. Sometimes it just gets rough and moderate vision loss occurs (dry). In others the macula will actually rupture and bleed (wet) resulting in the loss of central vision. Macular degeneration is much more common in those with fair colored skin and eyes. There also is an association with smoking and not eating healthy. Eye specific vitamins (Ocuvite, PreserVision, etc) can help. In later stages of the disease, more dramatic treatment such as medications injected into the eye can help somewhat.
Keratoconus: The cornea is the clear front part of the eye. Since it's made of keratin, terms describing disorders of the cornea usually use "kerato" in the word. Keratoconus is a disorder where the cornea is cone shaped so that's where the "conus" part of the term derives. Many people have mild keratoconus just have fluctuating eye glass prescriptions but if the cornea gets significantly cone shaped you would not see well with just glasses. Hard contacts or even surgery might be needed. Keratoconus is associated with allergies and rubbing of the eye and having it completely makes you not a candidate for LASIK.
LASIK: (laser assisted in-situ keratomileusis) Keratomileusis was a very rare surgical procedure where they basically removed a section of the clear part of the front of the eye (cornea) and froze it, reshaped it, and reinserted it, to try to fix someone's need for glasses. With the development of advanced lasers, surgeons saw that they could do a similar procedure and reshape the eye with these lasers. The "in-situ" reversed letter part of the acronym is a latin term for "in place". This laser resculpting of the front of the eye be done on the top of the eye but with LASIK a thin layer of cornea is cut and flapped over, the eye is then lasered and the flap is placed back over the area that was lasered. This results in much faster recovery and minimal discomfort. LASIK was developed in the 1990's.
RK (Radial Keratotomy):Prior to LASIK, there was a different procedure used to try to fix nearsightedness. This procedure developed in Russia involved strategically cutting multiple thin radial cuts in the front of the eye (cornea). As the cuts healed and scarred the eye would be pulled into a different shape and see better without glasses. It was generally less expensive than LASIK but never became as popular due to side effects, inaccuracy, etc.
Pterygium: (the "p" is silent) A pterygium is a red layer of fibrous tissue that develops over the front white part of the eye and then starts to grow over the clear central part of the eye (cornea). It's associated with too much dust and sun exposure. Interestingly, the "pter" part of the word derives from the word wing like the winged dinosaurs pterodactyls. Surgical removal of pterygia has advanced significantly over recent years but it is still and difficult and often not very successful procedure.
Pinguecula: A pinguecula is similar to a pterygium, it's a growth of tissue on the white part of the eye related to exposure. The main difference is a pinguecula does not grow over the cornea and therefore they are rarely surgically removed.
"pink eye": Pink eye is a non-medical term used when someone has a contagious eye infection. Usually the doctor would use a different term such as conjunctivitis which describes an inflammation of the fleshy tissue over the white part of the eye (conjunctiva). Conjunctivitis has many causes including allergy as well as infection. Usually the term "pink eye" is reserved for cases of difficult to manage viral conjunctivitis. Unfortunately it's unlikely that medications will help much with viral conjunctivitis so the infection mainly has to run it's own course.