A Cataract is a clouding or opacity of the natural internal lens of the eye which causes a visual impairment. The natural lens is located behind the iris, or "colored part" of the eye. The opacity may be a small dot or may involve the entire lens.
The opacity in the lens causes the light entering the eye to be scattered, causing images to appear hazy or blurred.
Classification of Cataracts:
- Late Onset (Senile) Cataracts: Late Onset, or Senile, cataracts develop later in life and accounts for 90% of all cataracts. They may sometimes have contributing factors such as diabetes, ocular trauma, glaucoma or the metabolic effects of aging.
- Nuclear Cataract: Nuclear Cataracts are the most common. These are frequently related to aging. The appearance ranges from a faint haze in the pupil to a deep burnished yellow, similar to a smoky fog. As a result, the individual reports a "yellowing" of vision. Frequently, there is a shift in glasses prescription to become less hyperopic ("far sighted") or more myopic ("near sighted"). For those that are hyperopic, the vision improves and is said to have temporary "second sight". As the cataract progresses, the shift continues into myopia with resulting higher lens prescription. Individuals who are developing nuclear cataracts, in the early stages, frequently complain of lens prescriptions that do not seem quite right. Another frequent complaint is "fluctuating vision", where vision becomes less clear for brief periods. Occasionally, in the early stages there will be "sharp pains" in the eye which last for only a fraction of a second. These are the result of the eyes musculature frustration trying to correct itself. Individuals often complain of poor night vision and "blinding" headlights.
- Posterior Subcapsular Cataract: Posterior Subcapsular cataracts appear in the center of the lens of the eye. Most frequently, they occur on the posterior (back) part of the lens. There is not any usual shift in lens prescription such as is found in nuclear cataracts. Because they appear more in the center of the lens, if the pupil is small, such as in bright light, the vision is reduced. In contrast, in reduced light, such as at night, the pupil is open, allowing light to go around the cataract. As such, vision at night may be better. Or, the individual may feel driving at night is easier than sunny days. This type of cataract can also be related to a systemic disease or prolonged steroid use.
- Cortical Cataract: The appearance of cortical cataracts show up as "spokes of a wheel". The location of this lens opacity is in the cortex of the lens. The opacity tends to be most pronounced in the periphery of the pupil. This means that in bright daylight and normal room lighting, the vision is not as affected as when the pupil is more dilated at night.
- Morgagnian (Mature) Cataract: The Mature Cataract is diffusely opaque or white. When the nucleus of the lens has turned yellow, and has fallen by gravity to the lower part of the lens, it is said to be a "Morgagnian Cataract". Cataract surgery is hightly recommended when this type of cataract develops due to the fact that damage will ultimately occur to the inside of the eye. Secondary Glaucoma is a frequent complication.
- Congenital Cataracts: In congenital cataracts the lens opacity is present at birth. These type cataracts can be caused from genetic or maternal reasons. There are many different morphological shapes. In infants, congenital cataracts are usually bilateral and recognized by the appearance of a white pupil, which is detected during a routine eye examination in the baby's first six months of life. Maternal reasons for the development of cataracts may include: syphilis, rubella or secondary to amniocentesis. There are various types of congenital cataracts. The specific treatment depends on the type and severity.
- Infantile or Juvenile Cataracts: Infantile or Juvenile Onset cataracts have a definite genetic origin and tend to co-exist with other abnormalities such as inborn errors of metabolism, identified chromosomal abnormalities, and other eye conditions. Causes for these type of cataracts include: diabetes, galactosemia, hyperlysinemia, homocystinuria, Down Syndrome, Turners Syndrome, Muscular Dystrophy, Idiopathic Hypoparathyroidism, Rieger's anomaly, aniridia and retinitis pigmentosa.
- Traumatic Cataract: Traumatic cataracts can result from two major types of injuries:
- Perforating Eye Injuries: If a sharp object penetrates the eye (ex. wire) and penetrates the capsule of the lens in the eye, a cataract will frequently develop. These usually will develop at a fast rate.
- Blunt Eye Injuries: If the eye is injured by a blunt compression type injury, a cataract may develop up to several years after the injury. Additionally, with this type of injury, the zonules attaching to the lens capsule may be torn or injured, which may impair the "near point" focusing ability for the individual.
- Secondary Cataract: A secondary cataract, or Capsular Fibrosis, is directly related to a specific disease, systemic disorder or chemical agent such as prescription medications. The physical appearance and manifestation of these different types of cataracts varies. For example, long term use of prednisone (steroid) frequently will result in cataracts. Many other medications have been found to cause cataracts. The decision as to the use of these medications should always be considered in light of this possiblity. Additionally, cataracts can form secondarily to some type of systemic disease. One disease that has frequently been shown to result in secondary cataracts is diabetes.
Answers To Your Questions About Cataracts:
- Why do cataracts form?:
Scientists do not know the exact cause of cataract formation. They do know that a chemical change takes place within the natural lens of the eye causing it to become clouded. This clouding progresses with age, and if left untreated, can cause severe visual impairment.
- Who gets cataracts?:
90% of cataracts are due to the normal aging process, affecting people over the age of 50. Not all cataracts, however, are due to age. Lens opacities can be present at birth, while others develop by another cause. Some factors that have been found to contribute to the formation of cataracts are: Age, Genetics, Injury, Nutritional deficiencies, Ultra-violet (UV) radiation, Chemotherapy, Steroid Therapy, Diabetes, or Renal Failure.
- What are some symptoms of cataracts?:
- Blurred, fuzzy or hazy vision
- Seeing as though looking through a cobweb, or having a film over the eye
- Frequent changing of glasses prescriptions, or seeing better without glasses
- Rings or halos around lights
- Severe decrease in vision with glare or bright lights in the eye
Misconceptions About Cataracts:
- Blindness: Early cataracts may impair sight, but fortunately the "blindness" is only temporary. After the lens is removed and replaced with a new lens, sight is restored. See cataract surgery for a more detailed explanation.
- Skin growing over the eye: Cataracts are often confused with a pterygium, which is a connective tissue growing over the cornea.
- Spreading of cataracts: An individual usually does have cataracts in both eyes, but this is not due to a spreading from one eye to the other, as in an infectious process.
Tests To Evaluate A Cataract:
- Visual Acuity: When the vision cannot be corrected to better than 20/50, surgery is recommended.
- Biomicroscopy: This examination enables the doctor to look at the cataract's shape and density in order to evaluate the degree of expected vision loss.
- Extended Ophthalmoscopy: Dilating drops are placed in the eye so as to allow the doctor a direct view of the back of the eye. This is important to assess the blood circulation and any abnormalities that may contraindicate surgery. See ophthalmoscopy for more detailed information.
- Visual Fields: The visual fields test measures the neurological sensitivity of the retinal nerves in the back of the eye.
- A-Scan: The A-Scan is a device to measure the length of the eye by ultrasonography. The A-Scan's computer is then able to calculate what the best IOL (intraocular lens) power should be to achieve the best possible vision after surgery.
Treatment Of Cataracts:
See "Cataract Surgery" For A Detailed Explanation On The Treatment Of Cataracts.
Additional Keywords And Misspellings:
Catract, Catarct, Catarakt
Once Cataracts have been diagnosed, the next question is, "When should cataract surgery be performed?" To answer this question, it is important to understand the progression of the cataract. Keep in mind that cataracts are not an emergency. In most cases they develop over a period of months or even years. During this period of time the patient is often frustrated with his or her vision. They know it could be better, so why wait? The real heart of the decision is lies within the question of surgical risk. For example, let us say that a person has visual acuity of 20/30. They can still read the paper, see most street signs, and carry on a normal life. If surgery is elected at that point, there may be only a small improvement in vision. On the other hand, if the person's vision is 20/70, they now are really borderline for driving. Newsprint is impossible to see except the headlines. The quality of life is now very much affected. Issues like personal safety are now being raised. At this point cataract surgery may, very well, be indicated. The surgical outcome may be a significant improvement in the individuals quality of life, and personal safety. Other aspects of the decision center around the individuals habits and hobbies. As an example, consider an issue such as color vision. Since some types of cataracts are yellow, an individual with this type of cataract and who is a painter may see colors shifted more to the yellow. Surgery might be well advised for a painter whose life depends on accurate color perception. Further examples of issues that affect the decision include questions about the individuals health, mobility, responsibilities, employment, recreation and relaxation activities. All of these issues should be discussed with your doctor so that the right decision is made that address yours specific circumstances. Eyesight is a basic foundation for your quality of life. Make sure that this decision is carefully researched.
- Lasers: One of the most common misconceptions about cataract surgery is found in the issue of lasers. Many people think that cataract surgery is performed with lasers. This is never true. Lasers are used for many eye conditions and eye surgical procedures, but never in cataract surgery. There is a condition called: secondary cataract where a laser, referred to as a YAG laser, is employed, but this is never used on a regular cataract.
- Phacoemulsification:Phacoemulsification is the most common surgical procedure now used in cataract surgery. This technique employs a very high frequency (ultrasound) device which literally breaks up the cataract, and vacuums it out of the eye in small pieces. Once the cataract is removed, a Intraocular Lens Implant (IOL) is inserted into the eye, in the place of the cloudy natural lens, which was extracted.
Cataract surgery has been noted as the single most common surgical procedure in the United States. Because of this, both Eye Surgeons (Ophthalmologists) and Optometric Physicians (Optometrists) are well trained in the management of this condition. Optometric physicians frequently will monitor a patient for years until he or she is ready for cataract surgery. Under a common protocol referred to as co-management, the Optometric physician and the Eye surgeon (Ophthalmologist) will work together to provide the patient with a combined program where the historical information is offered by the Optometrist to help facilitate a more favorable surgical outcome. With this combined information the the best eye surgeons are able to concentrate on providing the highest level of eye surgery known today. Post-op care can be provided by the surgeon or the optometrist, depending on their combined working relationship. For further information see: Aphakia, Pseudophakia and Intraocular lens Implant (IOL).
surgery catract aphakea sudophakia lens implant
The blockage of the main blood supply to the eye, causing blindness.
Additional keywords and misspellings:
retinal oclusion occlution cornial korneal
Central serous chorioretinopathy (CSCR) is the spontaneous leakage of fluid into the retina, often in young, healthy people between the ages of 25 and 50. The cause is unknown, although stress is believed to be linked to the problem.
How does it happen?
CSCR occurs when a small break forms in the blood vessels that form the pigment layer of the retina, causing fluid to seep up through the break and creating a retinal detachment. CSCR typically resolves on its own, but it can recur and in some cases, it may lead to moderate but permanent loss of central vision.
What are the signs?
Blurred, wavy, or distorted vision ; a central blind spot
How is it treated?
Ophthalmoscopy to examine the retina is typically used to diagnose CSCR. Fluorescein angiography is often used to gather additional information about the extent and severity of the problem. Most patients with CSCR do not require treatment since it usually resolves itself. The fluid usually absorbs gradually over a period of months, often like a water blister on the skin. Steroidal and non-steroidal anti-inflammatory eye drops may be prescribed and in some cases, laser treatment may be required to stop the leak.
Additional keywords and misspellings:
serrus serious retinapathy retinopothy
A Central Vision Test is a simple screening test used to assess the macula (the center of the retina). The Amsler Grid, which tests the central vision, consists of evenly spaced horizontal and vertical lines printed on black or white paper with a small dot in the center of the grid for fixation. The presence of wavy lines and missing areas of the grid is helpful for determining vision problems.
If the lines of grid do not appear straight and parallel or there are missing areas, the doctor will examine the back of the eye (the macula) very closely. This test is frequently given to patients to monitor macular degeneration.
A bump in the eyelid caused by a clogged oil gland. Some chalazions require surgical removal.
Additional keywords and misspellings:
calazion chalazyon kalazion kallazion callazion
The thin, blood-rich membrane that covers the white of the eyeball, responsible for supplying blood to the retina.
Additional keywords and misspellings:
coroid koroid chorod chorid membrane retina
The part of the eye that produces aqueous humor, which fills the orbit and lends shape to the cornea.
Additional keywords and misspellings:
ciliry silliary scilliary liquid fluid cilary
Cogan's Dystrophy (or Map-Dot-Fingerprint Dystrophy) is a disease affecting the cornea. It is characterized by microscopic dot and fingerprint-like patterns that form within the cornea.
The superficial layer of the cornea, also called the epithelium, is what is affected by Cogan's Dystrophy. The epithelium's bottom cells become thickened and uneven, which weakens the cell bonds and may cause the epithelium to loosen and "slough off" in areas, a condition called corneal erosion.
How do I get it?
Cogan's is not genetic so it isn't inherited. It typically affects both eyes and is diagnosed after the age of 30. Cogan's usually becomes progressively worse with age.
What are the Symptoms?
Cogan's is often silent and therefore, there may be no symptoms. The symptoms among patients may vary widely in severity and include:
- Mild to extreme irritation and discomfort that is worse in the morning
- Light sensitivity
- Fluctuating vision
- Blurred vision
- Irregular astigmatism (uneven corneal surface) The doctor may detect the disease by examining the layers of the cornea with a slit lamp microscope.
How is it treated?
The treatment for Cogan's depends on the severity of the problem. In some cases, corneal topography may be needed to evaluate and monitor astigmatism resulting from the disease. Artificial tears are used to lubricate the cornea and keep the surface smooth and comfortable. Lubricating ointments may be used at bedtime so the eyes are more comfortable in the morning. Saline solution drops or ointments are often prescribed to reduce swelling and improve vision. Gas permeable contacts may be fit for patients with irregular astigmatism to create a smooth, even corneal surface and improve vision.
For patients with recurrent corneal erosion, a soft contact lens may be used as a bandage to keep the eye comfortable and allow the cornea to heal. In some cases, laser treatment may beneficial. The surgeon removes the epithelium with an Excimer laser, creating a regular, smooth surface. The epithelium quickly regenerates, usually within a matter of days, forming a better bond with the underlying cell layer.
Color Deficiency is frequently referred to as "color blindness". In reality, rarely is anyone ever totally color blind. In most cases there are only varied reductions in the individuals color perception. Each individual is totally different. Color deficiency occurs when one is not able to distinguish the differences between certain shades of color. The cause of color deficiency is often inherited, but can be the result of disease, medications, or trauma. In the color deficient eye, the cone cells, which are found in the retina on the back of the eye, are not transmitting the color message to the brain correctly.
The human eye is sensitive to wavelengths in the electromagnetic (EM) frequency spectrum from 400 nm to 700nm. The central 30 degree part of the back of the eye, predominently contains the "cones", which are the color nerve ending receptors. There are three different types of cones which are sensitive to three different ranges of wave lengths:
- The "Blue" cones pick up wavelengths from 400nm to 540nm.
- The "Green" cones pick up on 500nm to 630nm.
- "Red" cones pick up wavelengths from 500nm to 690nm. Below 400nm is classified as "Ultra-violet", while above 700nm is classified as "Infra-red". Both of those regions of the EM spectrum are invisible to the human eye without special electronic devices. (see: Ultraviolet Protection (UV), and Night Scopes, for more information about dealing with these issues.)
Effects From Color Deficiency
For many individuals, a mild color deficiency may have very little significance on their life. They may find that selection of wallpaper or the right dress or tie in the morning to be a minor a slight inconvenience. It is, however, of value for the individual to know what the status of their color vision is so that they can take that into account in the normal transactions of their daily life. For others, it may be very important. The selection of ones occupation or even their elegability to a field of work may be limited, if a color deficiency is present. For example, a young person contemplating a carrier as a "miltary pilot" would find it difficult or impossible to reach that goal, since many items in aviation are classified by their color. Examples of color classifications include: electronic wiring, smoke flares and aviation fuel. Another example would be someone who is interested in the field of painting. While a color deficiency might not prevent this field of work, it would certainly be important for the individual to be aware of the exact wavelengths (color) that they are deficient in.
Classification Of Color Deficiency:
- Protanomaly: Reduced sensitivity to RED colors
- Deutanomaly: Reduced sensitivity to GREEN colors
- Tritanomaly: Reduced sensitivity to BLUE / YELLOW colors
- Protanopia: Total loss of RED colors
- Deutanopia: Total loss of GREEN colors
- Tritanopia: Total loss of BLUE / YELLOW colors
Color Vision Testing
There are many different types of color vision testing equipment. The following are commonly used tests:
- Pseudo-Isochromatic Plates (Ishahira)
These are a series of plates which have a matrix of dots arranged to show a number. To those who have normal color vision, the number is easy to see. For those who do not have normal color vision, the numbers blend into background of dots and therefore the number may not be able to be identified.
- Farnsworth Munsell Test
This test is more clinically useful due to a somewhat more quantitative evaluation of the color deficiency. In this test there is a tray of colored caps.They are presented in random order. The individual is instructed to arrange the caps in chromatic order between the two reference caps at each end of the 4 trays. The misalignment of these colored caps from their correct position in the series is then scored. The greater the displacement the higher the score.
Conjunctivitis is an inflammation of the thin, transparent layer covering the front of the eye and the inner surface of the eyelid. The eye will appear red, irritated and sometimes swollen.
There are three types of conjunctivitis:
- The most common is the INFECTIOUS form, which is commonly referred to as "pink eye". This form is caused by contagious bacteria or viruses and causes the eyes to become red, swollen, inflamed, blurry and itchy. Chlamydial (inclusion) and gonococcal conjunctivitis typically affects sexually active teens and young adults, and can infect an unborn baby. Antibiotics are usually prescribed.
- The second form, ALLERGIC conjunctivitis, can be brought on by common irritants such as pets or pollen, and other allergens. Seasonal allergies typically produce a thin, watery discharge and do not involve the cornea. If there is a thick, ropy discharge with severe itching and corneal involvement, it is most likely Vernal Keratoconjunctivitis and not a seasonal allergy. VKC is more common in the warmer climates and strikes men mostly between the ages of three and 25 years.
- CHEMICAL conjunctivitis can be triggered by chlorine and air pollution.
Chemical and allergic conjunctivitis usually is best treated by avoiding or removing the cause of the irritation and allowing the eye to heal naturally. Over-the-counter artifical tears often help to relieve the discomfort while it heals, along with cool compresses. Sometimes topical antihistamines or decongestants are prescribed to reduce swelling and aid in the healing process.
Additional keywords and misspellings:
viral conjunctivitis bacterial conjunctivitis chlamydial gonococcal vernal keratoconjunctivitis
Contact Lens Conjunctivitis, or GPC ( Giant Papillary Conjunctivitis) occurs as a result of contact lens usage. It is an allergic reaction to the lens, protein deposits on the lens, or certain preservatives in the contact lens solution itself.
Who can get it?
Contact Lens users, especially those who sleep in their lenses or don't clean their lenses often enough.
What are the symptoms?
Tearing of the eye, a thick mucous discharge upon awakening, itching, burning, and an inability to tolerate the contact lenses. Often blurring of the vision may occur after only a few hours of wearing time. Giant papillae may appear under the upper lid.
What is the treatment?
Treatment to relieve the itching, burning and discharge usually involves a prescription antibiotic. Since contact lenses can't be worn while prescription medications are being used, you may have to temporarily discontinue your contact lens wearing until the eyes have had a chance to heal and recover. Long-term prevention includes improving of ocular hygiene, avoiding sleeping in your lenses, changing contact lens or solution, or simply reducing wearing time.
- Soft Disposable Contact Lenses
- These lenses can be worn either as an Extended Wear Lens or a Daily Wear Lens.
- The main advantage of disposable lenses is that you always have fresh, clean lenses on your eyes. Most of the complications we see with soft contact lenses are related to "dirty" lenses.
- After two weeks of wearing the lenses, they are simply discarded.
- No time is spent cleaning, enzyming, or disinfecting lenses.
- If a lens is lost or damaged, you always have a new lens at home for immediate use.
- The use of solutions are minimal.
- These lenses can remain on the eyes for one week at a time.
- These lenses require less solutions than Daily Wear Lenses because they are removed from the eyes only once per week.
- When these lenses are removed from the eyes, they must be cleaned with Daily Cleaner and Enzymatic Cleaner, and placed in a Disinfecting Solution.
- Generally these lenses need to be replaced about every two years because of a build-up of protein and lipid deposits on the lens surface which can not be removed. A few patients need to replace these lenses more often.
Astigmatism is the result of having a cornea that is irregular in shape. The cornea is normally round. An astigmatic cornea is oblong or "football" shaped, resulting in a condition that generally causes eyestrain, headaches and blurry vision. Astigmatism is often associated with nearsightedness and farsightedness.
Contact lens research over the last several years has resulted in the development of a high performance, comfortable and easy to care for contact lens that corrects astigmatism. It is called a "soft toric lens". The Toric lens is specially designed to accomodate the irregularly-shaped cornea and provide crisp, clear vision. What's more, as a soft lens, the Toric is more comfortable, easier to wear, and easier to adjust to than the rigid lenses which had previously been prescribed for astigmatism.
- These are soft contact lenses that correct vision for individuals who require a different lens correction for their near vision and their far vision. Basically, if you wear bifocal glasses, then this is an option you could consider.
- There are now several different types of soft bifocal contacts available. We find that different brands work for different individuals. We put the contacts on your eyes to determine how well they fit the eye, and how well you see with the lenses. If one type does not work, we try a different brand.
- There are disposable brands available. Also, some are designed for "extended wear" so you can leave them on at night.
- Gas Permeable contact lenses are rigid lenses that allow oxygen to pass through them. Most brands today have an oxygen permeable between 60 to 90%. Also, they "wet" much better than the first generation gas permeable so they are much more comfortable.
- These lenses are used when the patient has astigmatism that cannot be corrected with a toric soft lens. Also, if the cornea is irregular, these lenses allow sharper vision.
- The main disadvantage of this type of lens is that it takes a longer period of time for the patient to adapt to wearing the lenses.
(contributed by H. Frank Storey, OD)
Contrast sensitivity testing is used to assess the quality of one's vision under "real-world" circumstances as opposed to the standard visual acuity testing, which measures eyesight under ideal conditions.
How its performed:
The contrast sensitivity test is done by displaying a series of stripes or bars that slant in different directions. The patient indicates which way the stripes are angled. As the test progresses, the stripes or bars become thinner and fainter.
The test gives the doctor a much more complete picture of your vision and is particularly useful for patients who see well on a conventional eye chart but still seem to have visual difficulties.
The front surface of the eye; the clear transparent tissue that covers the iris.
The spontaneous loss of a part of the surface "skin" of the eye, causing pain, light sensitivity and occasionally blurriness. The symptom often occurs on awakening.
Additional keywords and misspellings:
erosoin, erotion, cornael, korneal
kohr-nee-yahl TRANZ-plant SIRr-ja-ree
A surgical procedure in which the damaged or diseased cornea of the eye is removed and replaced with a donor cornea.
An ulcer or infection of the cornea extending beneath the surface layer. Usually bacterial in nature.
Corneal ulcers must be treated immediately to prevent permanent scarring of the cornea.
Additional keywords and misspellings:
cornial korneal conreal
An anti-reflective coating to reduce glare in either daytime or nighttime conditions. Combined with TD-2, Crizal lenses are anti-glare, scratch-resistant and easy to clean.