Hyperopia (Farsightedness)

Hyperopia, or farsightedness, is a common vision problem, affecting about a fourth of the population. People with hyperopia can see distant objects very well, but have difficulty seeing objects that are up close.
Hyperopia Symptoms and Signs
Farsighted people sometimes have headaches or eyestrain, and may squint or feel fatigued when performing work at close range. If you get these symptoms while wearing your glasses or contact lenses, you may need an eye exam and a new prescription.
What Causes Hyperopia?
This vision problem occurs when light rays entering the eye focus behind the retina, rather than directly on it. The eyeball of a farsighted person is shorter than normal.
Many children are born with hyperopia, and some of them "outgrow" it as the eyeball lengthens with normal growth.
Sometimes people confuse hyperopia with presbyopia, which also is a difficulty in seeing up close, but has a different cause.

The treatment for hyperopia depends on several factors such as the patient’s age, activities, and occupation. Young patients may or may not require glasses or contact lenses, depending on their ability to compensate for their farsightedness with accommodation. Glasses or contact lenses are required for older patients.
Refractive surgery is an option for adults who wish to see clearly without glasses. LASIK, Clear Lens Extraction And Replacement, LTK and intraocular contact lenses are all procedures that can be performed to correct hyperopia.

Myopia (Nearsightedness)

Nearsightedness, or myopia, is a vision problem experienced by up to about one-third of the population. Nearsighted people have difficulty reading highway signs and seeing other objects at a distance, but can see for up-close tasks such as reading or sewing.
Myopia Symptoms and Signs
Nearsighted people often have headaches or eyestrain, and might squint or feel fatigued when driving or playing sports. If you experience these symptoms while wearing your glasses or contact lenses, you may need a comprehensive eye examination as well as a new prescription.
What Causes Myopia?
Myopia occurs when the eyeball is slightly longer than usual from front to back. This causes light rays to focus at a point in front of the retina, rather than directly on its surface.

The nearsighted eye is longer than normal. Incoming light focuses in front of, instead of directly on, the retina. Far objects are blurry, while closer objects are more clear.
Nearsightedness runs in families and usually appears in childhood. This vision problem may stabilize at a certain point, although sometimes it worsens with age. This is known as myopic creep.

The treatment for nearsightedness depends on several factors such as the patient’s age, activities, and occupation. Vision can corrected with glasses, contacts, or surgery. Refractive procedures such as LASIK can be considered for adults when the prescription has remained stable for at least one year.

Macular Degeneration

Sometimes the delicate cells of the macula (part of the retina) become damaged and stop working, and there are many different conditions which can cause this. If it occurs later in life, it is called “age-related macular degeneration”, also often known as AMD.
Broadly speaking, there are two types of macular degeneration or AMD, usually referred to as “wet” and “dry”. This is not a description of what the eye feels like but what the optometrist or ophthalmologist can see when looking at the macula.
“Dry” AMD is the most common form of the condition. It develops very slowly causing gradual loss of central vision. Many people find that the vision cells simply stop working like the colours fading in an old photograph. There is no medical treatment for this type. However, aids such as magnifiers can be helpful with reading and other small detailed tasks.
“Wet” AMD results in new blood vessels growing behind the retina, this causes bleeding and scarring, which can lead to sight loss. “Wet” AMD can develop quickly and sometimes responds to treatment in the early stages. It accounts for about 10 per cent of all people with AMD.
AMD usually involves both eyes, although one may be affected long before the other. This sometimes makes the condition difficult to notice at first because the sight in the “good” eye is compensating for the loss of sight in the affected eye.
You cannot wear out your sight, so do not be afraid to continue to use the “good” eye as normal.
The good news is that AMD is not painful, and almost never leads to total blindness. It is the most common cause of poor sight in people over 60 but very rarely leads to complete sight loss because only the central vision is affected. This means that almost everyone with AMD will have enough side (or peripheral) vision to get around and keep his or her independence.

http://www.nei.nih.gov/health/maculardegen/armd_facts.asp#1a

Sclera

The sclera is commonly known as "the white of the eye." It is the tough, opaque tissue that serves as the eye's protective outer coat. Six tiny muscles connect to it around the eye and control the eye's movements. The optic nerve is attached to the sclera at the very back of the eye.
In children, the sclera is thinner and more translucent, allowing the underlying tissue to show through and giving it a bluish cast. As we age, the sclera tends to become more yellow.

Conjunctiva

The conjunctiva is the thin, transparent tissue that covers the outer surface of the eye. It begins at the outer edge of the cornea, covering the visible part of the sclera, and lining the inside of the eyelids. It is nourished by tiny blood vessels that are nearly invisible to the naked eye.
The conjunctiva also secretes oils and mucous that moisten and lubricate the eye.

I Can Bite My Eye

A man walks into a bar has a few drinks and asks what his tab was. The bartender replies that it is twenty dollars plus tip. The guy says, "I'll bet you my tab double or nothing that I can bite my eye." The bartender accepts the bet, and the guy pulls out his glass eye and bites it.
He has a few more drinks and asks for his bill again. The bartender reports that his bill now is thirty dollars plus tip. He bets the bartender he can bite his other eye. The bartender accepts knowing the man can't possibly have two glass eyes. The guy then proceeds by taking out his false teeth and biting his other eye.

Seeing Eye Dog

A blind man with a seeing eye dog at his side walks into a grocery store. The man walks to the middle of the store, picks up the dog by the tail, and starts swinging the dog around in circles over his head.
The store manager, who has seen all this, thinks this is quite strange. So, he decides to find out what's going on. The store manager approaches the blind man swinging the dog and says, "Pardon me. May I help you with something."
The blind man says, "No thanks. I'm just looking around."

Iris

The colored part of the eye is called the iris. It controls light levels inside the eye similar to the aperture on a camera. The round opening in the center of the iris is called the pupil. The iris is embedded with tiny muscles that dilate (widen) and constrict (narrow) the pupil size.
The sphincter muscle lies around the very edge of the pupil. In bright light, the sphincter contracts, causing the pupil to constrict. The dilator muscle runs radially through the iris, like spokes on a wheel. This muscle dilates the eye in dim lighting.
The iris is flat and divides the front of the eye (anterior chamber) from the back of the eye (posterior chamber). Its color comes from microscopic pigment cells called melanin. The color, texture, and patterns of each person's iris are as unique as a fingerprint.

Pupil

The pupil is the variable-sized, black circular opening in the center of the iris that regulates the amount of light that enters the eye. It appears black because most of the light entering the pupil is absorbed by the tissues inside the eye.

The pupil, oddly enough, is not even a structure. It's merely a hole in the center of the colored part of your eye (the iris). Via the muscles in the iris, the pupil controls the amount of light entering the eye by getting smaller (constricting) in bright light, and getting larger (dilating) in dim light.

Crystalline Lens

The crystalline lens is located just behind the iris. Its purpose is to focus light onto the retina. The nucleus, the innermost part of the lens, is surrounded by softer material called the cortex. The lens is encased in a capsular-like bag and suspended within the eye by tiny "guy wires" called zonules.
In young people, the lens changes shape to adjust for close or distance vision. This is called accommodation. With age, the lens gradually hardens, diminishing the ability to accommodate.

Cornea

The cornea is the transparent, dome-shaped window covering the front of the eye. It is a powerful refracting surface, providing 2/3 of the eye's focusing power. Like the crystal on a watch, it gives us a clear window to look through.

Because there are no blood vessels in the cornea, it is normally clear and has a shiny surface. The cornea is extremely sensitive - there are more nerve endings in the cornea than anywhere else in the body.

The adult cornea is only about 1/2 millimeter thick and is comprised of 5 layers: epithelium, Bowman's membrane, stroma, Descemet's membrane and the endothelium.
The layers of the cornea:
The epithelium is layer of cells that cover the surface of the cornea. It is only about 5-6 cell layers thick and quickly regenerates when the cornea is injured. If the injury penetrates more deeply into the cornea, it may leave a scar. Scars leave opaque areas, causing the corneal to lose its clarity and luster.
Boman's membrane lies just beneath the epithelium. Because this layer is very tough and difficult to penetrate, it protects the cornea from injury.
The stroma is the thickest layer and lies just beneath Bowman's. It is composed of tiny collagen fibrils that run parallel to each other. This special formation of the collagen fibrils gives the cornea its clarity.
Descemet's membrane lies between the stroma and the endothelium. The endothelium is just underneath Descemet's and is only one cell layer thick. This layer pumps water from the cornea, keeping it clear. If damaged or disease, these cells will not regenerate.
Tiny vessels at the outermost edge of the cornea provide nourishment, along with the aqueous and tear film.

Glaucoma

Glaucoma refers to a group of diseases in which your optic nerve becomes damaged and causes a gradual loss of peripheral vision. There are many types of glaucoma, but the most common is primary open angle glaucoma which is characterized by increased intraocular pressure (IOP). Glaucoma is the second leading cause of blindness, and has no symptoms, hence it's well-earned nickname "the sneak thief of sight". Glaucoma can be controlled with eyedrops or surgery to lower the IOP, but cannot be cured. Long term follow up care and treatment is neccessary to minimize vision loss. For more detail see:

http://en.wikipedia.org/wiki/Glaucoma

Retina

The light sensitive part of the back of the eye that corresponds to the film in a camera.
Just like the film in a camera, the retina captures images upside down and backwards and sends them to the brain for interpretation.
The retina consists of ten layers of neural tissue that is actually considered an extension of the brain.
The center of the retina called the macula, an oval stucture of about 1.5 mm diameter. In the center of the macula is a small "pit" called the fovea. The fovea contains the most sensitive portion of our vision. It is responsible for all fine detail that we see.
For a more detailed explanation see http://en.wikipedia.org/wiki/Retina#Diagnosis_and_treatment

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Flashes and Floaters

Flashes and Floaters(Posterior Vitreous Detachment)
Overview
The space between the crystalline lens and the retina is filled with a clear, gel-like substance called the vitreous humor. In a newborn, the vitreous has an egg-white consistency and is firmly attached to the retina. With age, the vitreous thins and may separate from the back of the eye. This is called posterior vitreous detachment (PVD), a very common, usually harmless condition.
As the vitreous pulls free from the retina, it is often accompanied by light flashes or floaters. Floaters are caused by tiny bits of vitreous gel or cells that cast shadows on the retina. Flashes occur when the vitreous tugs on the sensitive retina tissue.
There are other more serious causes of flashes and floaters, however. Retinal tears, retinal detachment, infection, inflammation, hemorrhage, or an injury such as a blow to the head may also cause floaters and flashes. (Have you ever seen stars after bumping your head?) Occasionally, flashes of light are caused by neurological problems such as a migraine headache. When related to a headache, the flashes of light are seen in both eyes and usually lasts 20-30 minutes before the headache starts.

Signs and Symptoms
1. Black spots or “spider webs” that seem to float in the vision in a cluster or alone
2. Spots that move or remain suspended in one place
3. Flickering or flashing lights that are most prominent when looking at a bright background like a clear, blue sky
4. Symptoms that may indicate a more serious problem
5. Sudden decrease of vision along with flashes and floaters
6. Veil or curtain that obstructs part or all of the vision
7. Sudden increase in the number of floaters

Detection and Diagnosis
Notify your optometrist or ophthalmologist immediately if you notice a sudden shower of floaters, new light flashes, a veil or curtain obstructing your vision, or any other change. The doctor will dilate your pupils with drops and examine the vitreous and retina inside the eye with an ophthalmoscope.

Patient to the eye doctor: "Whenever I drink coffee, I have this sharp, excruciating pain."
"Try to remember to remove the spoon from the cup before drinking."

Welcome to the World of Eyecare

Welcome to the World of Eyecare. Hopefully, the reader of this blog will walk away with some knowledge regarding their eyes or eyecare that they didn't know before. This blog is not intended to be used to self-diagnose an eye problem, only an eye examination can provide that. Our purpose is to educate the reader on an aspect of eyecare they may want to know more about. If you, or someone you know has been diagnosed with an eye problem, hopefully you'll find some information here translated into common English. If you have any questions or concerns about any information provided here, please consult your own eye doctor. We can not assume any liability or responsibility for any information misused or misinterpreted from this blog.