+ Read about Astigmatisms
Astigmatism is an imperfection in the curvature of your cornea-- the clear, round dome covering the eye’s iris and pupil-- or in the shape of the eye’s lens. Normally, the cornea of a normal eye is curved like a basketball, with the same degrees of roundness in all areas.
An eye with astigmatism is curved more like a football, with some areas that are steeper or more rounded than others. This can cause images to appear blurry and stretched out. Astigmatism can be corrected with eyeglasses, contact lenses or surgery. Individual lifestyles affect the way astigmatism is treated.
+ Read about Bell's Palsy
A nerve problem that affects the muscles of your face. It causes weakness or partial paralysis of the muscles on one side of your face. With Bell’s palsy, your eyelid may not close properly and your smile may seem uneven.
+ Read about Blepharochalasis
An inflammation of the eyelid that is characterized by exacerbations and remissions of eyelid edema, which results in a stretching and subsequent atrophy of the eyelid tissue, leading to the formation of redundant folds over the lid margins. This often affects the upper eyelids and usually occurs on both eyes.
+ Read about Blepharitis
A type of inflammation of the eyelids. Blepharitis usually involves the part of the eyelid where the eyelashes grow and affects both eyelids. Blepharitis commonly occurs when tiny oil glands located near the base of the eyelashes become clogged. This can lead to irritated and red eyes. In many cases, a warm washcloth used to clean and apply slight pressure on the eye can help.
+ Read about Blepharospasm
An Eyelid twitch, or Blepharospasm, is a repetitive involuntary condition usually involving both eyes, where the eyelids and, sometimes, the eyebrows close involuntarily. For most people, these spasms are very mild and feel like a tug on the eyelid. Most spams will resolve on their own without the need for treatment. However, others may experience spasms strong enough that may temporarily cause an inability to see because of the involuntary eyelid closure. These spasms are rare but can be very troublesome and incapacitating.
+ Read about Cataracts
A cataract means that your normally clear lens, located behind your eye’s colorful iris, has grown cloudy. The lens contains mostly water and proteins that are specifically organized to focus light on the retina for clear vision. In many people, the proteins begin to clump and obscure vision.
The majority of cataracts are age-related. A cataract begins as a small opacity within the lens and grows until it interferes with vision. Many people have cataracts and don’t even notice until the defect grows large. Vision might appear hazy at first and lights might give off a halo or glare. Once the cataract is beginning to affect vision for daily activities, Cataract-removal surgery is an effective option.
Chalazia & Styes
+ Read about Chalazia & Styes
The term chalazion comes from a Greek word meaning a small lump. It refers to a swelling in the eyelid caused by inflammation of one of the small oil producing glands (meibomian glands) located in the upper and lower eyelids. A Chalazion is sometimes confused with a Stye which also appears as a lump in the eyelid. A Stye is an infection of a lash follicle that forms a red, sore lump near the edge of the eyelid.
Chalazions are treated with any or a combination of the following methods: warm compresses, steroid injections, or surgical incision or excision. Often, after several days Chalazions and Styes go away on their own.
+ Read about Conjunctivitis
Conjunctivitis is the term used to describe inflammation of the conjunctiva. In ordinary terms, conjunctivitis is simply the most common cause of red or “pink” eye. The white of the eye (sclera) is called the conjunctiva which produces mucus to coat and lubricate the surface of the eye. It normally has fine blood vessels within it, which can be seen on close inspection.
When the conjunctiva becomes irritated or inflamed, the blood vessels which supply it enlarge and become much more prominent, causing the eye to turn red. Treatment depends on the whether the conjunctivitis is caused by a virus, bacteria, or allergies.
+ Read about Corneal Ulcers
A corneal ulcer, or ulcerative keratitis, is an open sore on the cornea. The cornea covers the iris and the round pupil, much like a watch crystal covers the face of a watch. A corneal ulcer usually results from an eye infection, but severe dry eye or other eye disorders can cause it.
Corneal ulcers are often extremely painful due to nerve exposure, and can cause tearing, squinting, and vision loss of the eye. Treatment is dependent on the cause of Keratitis. Often if it is the result of a scratch or extended contact lens use, you may not need any treatment. In other cases you may need to apply prescription medicine to the eye.
+ Read about Dermatochalasis
Dermatochalasis is a term used to describe the presence of loose and redundant eyelid skin, also known as “baggy eyes”. It is a common sign of periocular aging and is often seen in middle-aged and elderly people. More dramatically seen in the upper eyelids, dermatochalasis can affect lower eyelids as well. It is commonly associated with orbital fat herniation, known as steatoblepharon, and drooping of the eyelids, known as blepharoptosis.
+ Read about Diabetic Retinopathy
People with diabetes can have an eye disease called diabetic retinopathy. This is when high blood sugar levels cause damage to blood vessels in the retina. Sometimes, these blood vessels can swell and leak. Or they can close, stopping blood from passing through. In response, the body grows fragile new blood vessels (neovascularization) within the retina.
A person with diabetic retinopathy might notice symptoms only after damage is done. Therefore, regular dilated eye exams from an ophthalmologist (eye doctor) are extremely important.
Diplopia (Double Vision)
+ Read about Diplopia
Diplopia, commonly known as double vision, is the perception of two images of a single object at the same time. Typically, this vision problem is the result of an underlying condition. Identifying and treating the cause can help you recover your eyesight and stop other symptoms from occurring. There are two types of diplopia: monocular and binocular diplopia.
Monocular diplopia is double vision in only one eye. The double vision continues even when the other eye is covered. The doubling does not go away when you look in different directions. Binocular diplopia is double vision related to a misalignment of the eyes. The double vision stops if either eye is covered. Any problem that affects one or more of the muscles around the eyeball that control the direction of the gaze can cause binocular diplopia.
+ Read about Dry Eyes
Dry eyes is a common condition that occurs when your tears aren't able to provide adequate lubrication for your eyes. Tears can be inadequate for many reasons. For example, dry eyes may occur if you don't produce enough tears or if you produce poor-quality tears.
Every time you blink, your healthy eyes get a bath from a fluid that's a combination of oil, water, and mucus. This fluid, or tears, helps protect and moisturize the eyes. When something irritates your eyes or interferes with the production of tears, it can result in irritated dry eyes that are vulnerable to corneal abrasions.
Dry eyes feel uncomfortable. If you have dry eyes, your eyes may sting or burn. You may experience dry eyes in certain situations, such as on an airplane, in an air-conditioned room, while riding a bike or after looking at a computer screen for a few hours.
+ Read about Ectropion
Ectropion is a "turning out" of the eyelid. Typically occurring on the lower eyelid, the skin of the inner lid is exposed, either in one section of eye or across the entire lid. This prevents tears from draining from the eye correctly, resulting in irritation. Artificial tears and lubricating ointments can help relieve symptoms of ectropion. But usually surgery is needed to fully correct the condition.
+ Read about Entropion
Entropion is a "turning in" of the eyelid. Typically occurring on the lower eyelid, the skin and lashes rub painfully against the cornea. The condition may cause the lid to turn in constantly or only at times when the eyes are closed tightly. Artificial tears and lubricating ointments can help relieve symptoms of ectropion. But usually surgery is needed to fully correct the condition.
+ Read about Episcleritis
Episcleritis is an inflammatory condition affecting the episcleral tissue between the conjunctiva (clear mucus membrane lining the inner eyelids and sclera) and the sclera (the white part of the eye) that occurs in the absence of an infection. The red appearance looks similar to conjunctivitis (“pink” eye), but there is no discharge.
There is no apparent cause for episcleritis, but it is sometimes associated with an underlying systemic inflammatory or rheumatologic condition such as rosacea, lupus, or rheumatoid arthritis. Typical symptoms include generalized or local redness of the eyes that may be accompanied by mild soreness or discomfort but no visual problems. Episcleritis generally clears without treatment, but topical or oral anti-inflammatory agents may be prescribed to relieve pain or manage symptoms in recurring cases.
+ Learn More
Esotropia, a common type of strabismus, is the inward deviation of an eye (toward the nose). The deviation or eye turn may occur while fixating (looking at) distance objects, near objects or both. It is the opposite of exotropia.
The eye turn may occur 100% of the time and is called constant or some of the time and is called intermittent. Although glasses, exercises or prisms may reduce or help control the outward turning eye in some children, surgery is often needed, especially for adults.
+ Read about Extropia
Exotropia, a common type of strabismus, is the outward deviation of an eye (away from the nose). The deviation or eye turn may occur while fixating (looking at) distance objects, near objects or both. It is the opposite of esotropia.
The eye turn may occur 100% of the time and is called constant or some of the time and is called intermittent. Although glasses, exercises or prisms may reduce or help control the outward turning eye in some children, surgery is often needed, especially for adults.*
+ Read about Flashes/Floaters
You may sometimes see small specks or clouds moving in your field of vision. They are called floaters. You can often see them when looking at a plain background, like a blank wall or a blue sky. Floaters are actually tiny clumps of gel or cells inside the vitreous, the clear jelly-like fluid that fills the inside of your eye. These tiny clumps actually are floating inside of your eye. What you are seeing are the shadows that these floaters cast on the retina.
When the vitreous gel rubs or pulls on the retina, you may see what look like flashing lights or lightning streaks. You may have experienced this same sensation if you have ever been hit in the eye and seen “stars”. As we grow older, it is more common to experience flashes. If you notice the sudden appearance of light flashes, you should visit your ophthalmologist immediately to see if the retina is torn.
Giant Cell Arteritis
+ Read about Glaucoma
Giant cell arteritis (GCA), also known as temporal arteritis, is a chronic inflammation of the lining of medium- and large-sized arteries. The cause of giant cell arteritis is unknown. Left untreated it can lead to blindness. Treatment should be initiated as soon as the diagnosis is suspected.
Giant cell arteritis (GCA) is the most common form of vasculitis that occurs in adults. Almost all patients who develop giant cell arteritis are over the age of 50. GCA commonly causes headaches, joint pain, facial pain, fever, and difficulties with vision, and sometimes permanent visual loss in one or both eyes.
With appropriate therapy, GCA is an eminently treatable, controllable, and often curable disease. The disease used to be called “temporal arteritis” because the temporal arteries, which course along the sides of the head just in front of the ears (to the temples) can become inflamed. However, we also know that other blood vessels, namely the aorta and its branches, can also become inflammed. The term “giant cell arteritis” is often used because when one looks at biopsies of inflamed temporal arteries under a microscope, one often sees large or “giant” cells.
+ Read about Glaucoma
Glaucoma is a group of eye disorders that lead to progressive damage to the optic nerve. People with glaucoma can lose nerve tissue, resulting in vision loss.
The optic nerve is a bundle of about 1 million individual nerve fibers that transmits the visual signals from the eye to the brain. In the most common form of glaucoma, primary open-angle glaucoma, the fluid pressure inside the eye increases. This increase in pressure may cause progressive damage to the optic nerve and loss of nerve fibers. Vision loss may result. Advanced glaucoma may even cause blindness.
+ Read about Hyperopia
Hyperopia, also known as farsightedness, is a common type of refractive error where distant objects may be seen more clearly than objects that are near. However, people experience hyperopia differently. Some people may not notice any problems with their vision, especially when they are young. For people with significant hyperopia, vision can be blurry for objects at any distance, near or far.
+ Read about Iritis
Iritis is inflammation of the iris (the colored part of the eye). The iris is a part of the middle layer of the eye (uvea), so iritis is a type of uveitis, also known as anterior uveitis. Iritis, the most common type of uveitis, affects the front of your eye. The cause is often unknown. It can result from an underlying systemic condition or genetic factor. White blood cells can be seen in the front part of the eye (anterior chamber) by an ophthalmologist using a microscope known as a slit lamp.
Macular Degeneration, Age-Related Macular Degeneration
+ Read about Macular Degeneration
AMD is a common eye condition and a leading cause of vision loss among people age 50 and older. It causes damage to the macula, a small spot near the center of the retina and the part of the eye needed for sharp, central vision, which lets us see objects that are straight ahead.
In some people, AMD advances so slowly that vision loss does not occur for a long time. In others, the disease progresses faster and may lead to a loss of vision in one or both eyes. As AMD progresses, a blurred area near the center of vision is a common symptom. Over time, the blurred area may grow larger or you may develop blank spots in your central vision. Objects also may not appear to be as bright as they used to be.
AMD has two forms: “Dry” (atrophic) and “Wet” (exudative). The more common “dry’ form of AMD has no cure, and any loss in central vision cannot be restored. However, there is a link between nutrition and the progression of dry AMD. There are dietary changes, nutritional supplements, and injections that can be taken to help slow the progression of “dry” AMD. If detected early, wet AMD can be treated with laser treatment, which is often called photocoagulation.
+ Read about Macular Hole
A macular hole is a small break in the macula, located in the center of the eye’s light-sensitive tissue called the retina. The macula provides the sharp, central vision we need for reading, driving, and seeing fine detail. Macular holes often begin gradually.
In the early stage of a macular hole, people may notice a slight distortion or blurriness in their straight-ahead vision. Straight lines or objects can begin to look bent or wavy. Reading and performing other routine tasks with the affected eye become difficult. A macular hole can cause blurred and distorted central vision. Macular holes are related to aging and usually occur in people over age 60.
Although some macular holes can seal themselves and require no treatment, surgery is necessary in many cases to help improve vision. In this surgical procedure–called a vitrectomy–the vitreous gel is removed to prevent it from pulling on the retina and replaced with a bubble containing a mixture of air and gas. The bubble acts as an internal, temporary bandage that holds the edge of the macular hole in place as it heals. An eye care professional who has examined the patient’s eyes and is familiar with his or her medical history is the best person to answer specific questions.
+ Read about Macular Pucker
A macular pucker can cause blurred and distorted central vision. It is usually related to aging, and happens in people over age 50. A macular pucker is an extra layer of tissue that has formed on the eye's macula. The macula is located in the center of the retina, an area of light-sensitive cells at the back of the eye. The macula is responsible for central vision, which is the sharp, straight-ahead vision we need for reading, driving, and seeing fine detail.
If your symptoms are mild, you might not need any treatment. Instead, your ophthalmologist may change your glasses or contact lens prescription to improve your vision.
If your symptoms are more serious, your ophthalmologist may recommend a surgery called vitrectomy. Your ophthalmologist will remove some of the vitreous and scar tissue on your macula. This flattens the macula, returning it to its proper position.
+ Read about Myopia
Nearsightedness, or Myopia, is a refractive error where close objects look clear, but distant objects appear blurred. Nearsightedness is caused when light comes to focus in front of the retina instead of directly onto the retina. This is a common condition that affects an estimated 25% of Americans.
If you are nearsighted, you typically will have difficulty reading road signs and seeing distant objects clearly, but will be able to see well for close-up tasks such as reading and computer use. Nearsightedness may develop gradually or rapidly, often worsening during childhood and adolescence. Nearsightedness tends to run in families.
Myopia is commonly treated using corrective lenses, such as eyeglasses or contact lenses. Refractive surgery may be able to correct some forms of myopia.
Nasal Lacrimal Duct Obstruction
+ Read about Nasal Lacrimal Duct Obstruction
An obstruction occurs in approximately 5% of normal newborn infants. Tears normally drain through small openings in the corners of the upper and lower eyelids called puncta and enter the nose through the nasolacrimal duct.
Tear duct obstruction prevents tears from draining through this system normally. If the tear duct is blocked, there will be backflow of tears and discharge from the eye. The blockage occurs most commonly at the valve of Hasner at the distal end of the duct.
+ Read about Ocular Rosacea
Ocular rosacea is inflammation that causes redness, burning and itching of the eyes. It often develops in people who have rosacea, a chronic skin condition that affects the face. Sometimes ocular, or eye, rosacea is the first sign that you may later develop the facial type.
Ocular rosacea primarily affects adults between the ages of 30 and 50. It seems to develop in people who tend to blush and flush easily.
When treating ocular rosacea, a stepwise approach can be undertaken, using first lid hygiene and artificial tears, followed by topical and oral anti-inflammatory medications, with late surgical intervention as required.
Optic Neuritis (MS)
+ Read about Optic Neuritis
Optic neuritis is swelling of the eye’s optic nerve. The optic nerve carries light signals from the back of your eye to your brain so you can see. If the optic nerve is swollen, damaged or infected, you cannot see clearly.
Doctors do not know for sure what causes optic neuritis. This condition may be caused by the body’s immune system attacking optic nerve tissue by mistake. It seems more likely to happen in people who have had viral problems like mumps, measles, flu or multiple sclerosis, among others.
Most people who have a single episode of optic neuritis eventually recover their vision. Treatment with steroid medications may speed up vision recovery after optic neuritis.
+ Read about Pinguecula
A pinguecula is a yellowish patch or bump on the white of the eye, most often on the side closest to the nose. It is not a tumor, but an alteration of normal tissue resulting in a deposit of protein and fat. Unlike a pterygium, a pinguecula does not actually grow onto the cornea. A pinguecula may also be a response to chronic eye irritation or sunlight.
Treatment is often unneeded with a pinguecula, as it does not grow onto the cornea. If it is inflamed, topical eyedrops or ointments may be used. On rare occasions, a pinguecula can be surgically removed, but the postoperative scar may be as cosmetically objectionable as the pinguecula.
Plaquenil (Hydroxychloroquine-Induced) Ocular Toxicity
+ Read about Plaquenil Ocular Toxicity
Many systemic medications may cause retinal toxicity. One such commonly used medication for dermatologic and rheumatologic inflammatory conditions is hydroxychloroquine (Plaquenil), a chloroquine derivative. It is used to treat many diseases including malaria, rheumatoid arthritis and systemic lupus erythematosus.
Chloroquine was originally used as an anti-malarial therapeutic. Chloroquine is now uncommonly used in favor of its derivative hydroxychloroquine. In the United States, hydroxychloroquine is most often used for its anti-inflammatory effects in rheumatology and dermatology.
Its toxic effects on the retina are seen in the macula. While early toxicity may be asymptomatic, patients with more advanced stage of toxicity may complain of color vision changes or paracentral scotomas. Advanced hydroxychloroquine toxicity presents as a bull’s eye maculopathy. Since retinal toxicity is usually irreversible, early detection of retinal toxicity and cessation of the offending agent is the best treatment.
Posterior Vitreous Detachment
+ Read about Posterior Vitreous Detachment
Most of the eye’s interior is filled with vitreous, a gel-like substance that helps the eye maintain a round shape. There are millions of fine fibers intertwined within the vitreous that are attached to the surface of the retina, the eye’s light-sensitive tissue.
As we age, the vitreous slowly shrinks, and these fine fibers pull on the retinal surface. Usually the fibers break, allowing the vitreous to separate and shrink from the retina. This is a vitreous detachment.
In most cases, a vitreous detachment, also known as a posterior vitreous detachment, is not sight-threatening and requires no treatment. lthough a vitreous detachment does not threaten sight, once in a while some of the vitreous fibers pull so hard on the retina that they create a macular hole to or lead to a retinal detachment. Both of these conditions are sight-threatening and should be treated immediately.
If left untreated, a macular hole or detached retina can lead to permanent vision loss in the affected eye. Those who experience a sudden increase in floaters or an increase in flashes of light in peripheral vision should have an eye care professional examine their eyes as soon as possible.
+ Read about Presbyopia
Presbyopia is the gradual loss of your eyes' ability to focus on nearby objects. It's a natural, often annoying part of aging. Presbyopia usually becomes noticeable in your early to mid-40s and continues to worsen until around age 65.
You may become aware of presbyopia when you start holding books and newspapers at arm's length to be able to read them. A basic eye exam can confirm presbyopia. You can correct the condition with eyeglasses or contact lenses. You might also consider surgery.
+ Read about Pterygium
A pterygium is a fleshy growth that invades the cornea (the clear front window of the eye). It is an abnormal process in which the conjunctiva (a membrane that covers the white of the eye) grows into the cornea. A pterygium may be small or grow large enough to interfere with vision and commonly occurs on the inner corner of the eye.
A pterygium occurs more often in people who spend a great deal of time outdoors, especially in sunny climates. When a pterygium becomes red and irritated, topical eyedrops or ointments may be used. If the pterygium is large enough, it can be removed surgically.
+ Read about Ptosis
Ptosis (pronounced “toe-sis”) is the medical term for drooping of the upper eyelid(s). The eyelid may droop just a little, or so much that it covers the pupil (the black dot at the center of your eye that lets light in).
A drooping eyelid or ptosis can be present at birth (congenital) or can occur later in life (acquired). Poor development of the levator palpebrae superioris muscle in the upper eyelid can lead to an inability to properly open the eye. Patients with ptosis often have difficulty keeping their eyelids open. To compensate, they will often arch their eyebrows in an effort to raise the drooping eyelids.
In severe cases, people with ptosis may need to lift their eyelids with their fingers in order to see. Children with ptosis may develop amblyopia (“lazy eye”) or developmental delay from limitation of their vision.
Ptosis can be corrected surgically and usually involves tightening the levator muscle to elevate the eyelid. In severe ptosis, when the levator muscle is extremely weak, a “sling” operation may be performed, enabling the forehead muscles to elevate the eyelid(s). Other types of repair may include surgery on the muscle on the inside of the lid in cases of small amounts of ptosis.
+ Read about Refractive Problems
The cornea and lens of your eye helps you focus. Refractive errors are vision problems that happen when the shape of the eye keeps you from focusing well. The cause could be the length of the eyeball (longer or shorter), changes in the shape of the cornea, or aging of the lens. Four common refractive errors are
- Myopia, or nearsightedness - clear vision close up but blurry in the distance
- Hyperopia, or farsightedness - clear vision in the distance but blurry close up
- Presbyopia - inability to focus close up as a result of aging
- Astigmatism - focus problems caused by the cornea
The most common symptom is blurred vision. Other symptoms may include double vision, haziness, glare or halos around bright lights, squinting, headaches, or eye strain.
Glasses or contact lenses can usually correct refractive errors. Laser eye surgery may also be a possibility.
+ Read about Retinal Detachment
Retinal detachment describes an emergency situation in which a thin layer of tissue (the retina) at the back of the eye pulls away from its normal position.
Retinal detachment separates the retinal cells from the layer of blood vessels that provides oxygen and nourishment. The longer retinal detachment goes untreated, the greater your risk of permanent vision loss in the affected eye. Warning signs of retinal detachment include the sudden appearance of floaters and flashes and reduced vision. Contacting an eye specialist (ophthalmologist) right away can help save your vision.
Symptoms include a sudden or gradual increase in either the number of floaters, which are little “cobwebs” or specks that float about in your field of vision, and/or light flashes in the eye. Another symptom is the appearance of a curtain over the field of vision. A retinal detachment is a medical emergency. Anyone experiencing the symptoms of a retinal detachment should see an eye care professional immediately.
Most retinal tears need to be treated by sealing the retina to the back wall of the eye with laser surgery. With laser surgery, your ophthalmologist uses a laser to make small burns around the retinal tear. The scarring that results seals the retina to the underlying tissue, helping to prevent a retinal detachment.
Retinal Vein Occlusions
+ Read about Vein Occlusions
A retinal vein occlusion means that a vein in the retina of the eye has become blocked. The retina is the light sensing tissue at the back of our eye. The veins drain blood out of the retina and return it to the heart. Blockage or occlusion in the vein, commonly known as a stroke, prevents adequate blood flow in the affected area.
When a retinal vein is blocked, it cannot drain blood from the retina. This leads to hemorrhages (bleeding) and leakage of fluid from the blocked blood vessels. Nerve cells need a constant supply of blood to deliver oxygen and nutrients and blood vessels provide this supply. When the retinal blood supply is blocked or slowed, the retina can be affected, impacting your vision.
Sixth Nerve Palsy
+ Read about Sixth Nerve Palsy
Abducens nerve palsy is the most common ocular motor paralysis. The abducens (sixth) cranial nerve controls the lateral rectus muscle, which abducts (move away from) the eye. Abducens nerve palsy causes an esotropia (eye looking inwards) due to the unopposed action of the antagonistic medial rectus muscle. The affected eye turns in toward the nose and is unable to abduct properly. The deviation is constant and is usually greater at distance fixation than at near. The esotropia is also worse when the patient is looking toward the affected side.
+ Read about Strabismus
Strabismus is a visual defect in which the eyes are misaligned and point in different directions. One eye may look straight ahead, while the other eye turns inward, outward, upward or downward. You may always notice the misalignment, or it may come and go. The turned eye may straighten at times and the straight eye may turn.
Strabismus is a common condition among children. About 4% of all children in the United States have strabismus. It can also occur later in life. Adults who develop strabismus often have double vision because the brain is already trained to receive images from both eyes and cannot ignore the image from the turned eye.
+ Read about Subconjunctival Hemorrhage
Subconjunctival Hemorrhage is bleeding underneath the conjunctiva. It can occur after a sudden or severe sneeze or cough, heavy lifting, straining, vomiting, or even rubbing one's eyes too roughly. It can also occur as a side effect of eye surgery or blood thinners.
The conjunctiva can't absorb blood very quickly, so the blood gets trapped. You may not even realize you have a subconjunctival hemorrhage until you look in the mirror and notice the white part of your eye is bright red.