How Diet Can Be Used as a Tool to Reduce Risk of Macular Degeneration

The macula is the area of the eye responsible for our sharp, central vision.  Everything we look directly at, be it a face or print on a written page is identified by the macula of the eye.  The macula consists of densely packed cells called photoreceptors. When light hits these photoreceptors, the signal is transmitted through to nerves that lead to the vision center of the brain.  In macular degeneration or other disease of the macula, the photoreceptors are damaged and unable to transmit the image to the brain. Healthy photoreceptors mean a healthy macula.

The macula serves your keenest central vision, so damage to this area is responsible for loss of detail, like face recognition or difficulty discerning print on a page.

Damage to the macula occurs when molecules in and around the area of the macula are “oxidized”, or broken down.   UV light is one of the culprits – the eye focuses much of the incoming light onto the macula and a such, the macula is exposed to more UV than other parts of the internal eye.  UV light is an “oxidant” and can cause breakdown of integral components in and near the macula.  Another major cause of oxidation in the macula is the blood stream, which contacts the macula from below.  Smokers and people with poor diets are exposed to more oxidants through the blood stream than non-smokers and people with healthy diets, leading to greater risk of macular degeneration.  There is also a strong genetic component in some people, so they may smoke and have a poor diet and never develop macular degeneration while their spouse may have the same habits and develop it.

Diets high in antioxidants have been shown to reduce risk of developing macular degeneration (AREDS study).

Specific antioxidants that help reduce risk of Macular degeneration include Lutein, Zeaxanthin and meso-Zeaxanthin.  Intake of Omega 3 fatty acids has also been suggested to benefit the macula, specifically Olive oil.  While vitamins are available to supplement the intake of these micronutrients, the body best absorbs them by eating fresh fruits and vegetables, specifically fresh spinach.   Spinach is the new “carrots” for the eye – extremely beneficial in people with family histories of macular degeneration.  Be careful when taking fish oil supplements if you are male, as some supplements and the vehicles in which they are ingested have been tied to prostate problems.  The National Eye Institute sponsored a the Age Related Eye Disease Study (AREDS) which determined the benefit of specific nutrients that may help to reduce the risk of progression of macular degeneration.

I try to eat a fresh spinach salad with a teaspoon of olive oil on it everyday to reduce my risk as we have a family history of macular degeneration and I recommend my patients do the same

Anatomical position of the macula of the eye

Anatomical position of the macula of the eye

Courtesy of the Doctors at Shady Grove Eye and Vision Care; Optometrists, Ophthalmologists and Opticians serving Rockville, Gaithersburg and Potomac Maryland suburbs of Washington DC for over 40 years.

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Why Close Work Can Cause Vision Change

Difficulty attempting to view distance objects is cause for most visits to the eye doctor. Road signs may seem a little blurry at first, then it becomes difficult to see the TV set or the jersey numbers on the basketball players at the arena. Examination by an eyecare professional usually results in a prescription change that corrects the blur. The blur may return over time. The person watches their prescription numbers increase year after year as lens thickness increases, dreading the day the doctor prescribes “coke-bottle” thick eyeglasses. The patient feels helpless in the wake of these increases. Many doctors discuss the vision change to the patient, insinuating prescription increases are normal and to be expected over time. The problem with this scenario is the development of the visual system (including the eye) is complete by adulthood. Then why is the vision changing? Genetic influences are the most likely cause of vision changes before adulthood and can be expected. Changes in distance vision should not continue to progress on a regular basis (excluding astigmatism) after the development of the visual system is completed through natural growth. The progression of Myopia (nearsightedness) during development of the visual system can be compounded by a dysfunction in the focusing mechanism (lens) of the eye, making the changes greater than they would have been through genetics alone. Any changes in vision after the complete development of the visual system is likely to have been brought about by problems causing over-focus (locking in of focus when viewing near objects) when looking at distance objects. Over-focus and failure to release focus to look at distance is a cause of progressive vision changes in adults. There are many ways to manage progression of distance blur.

THE NEAR TRIAD

The eye receives light and processes it as described in the section Anatomy of the Eye. This process is similar for viewing near and distant objects. Looking at distance objects differs from looking at near objects in how the musculature of the eye adjusts the focus mechanism, the Lens. Adjustment of focus for viewing near objects is termed Accomodation. When viewing distance objects (objects greater than 20 feet or 6 meters from our eyes), the eyes are aligned straight ahead and the line of sight of each eye is approximately parallel to one another. Light from the distance target enters the eye and is focused on the Retina, or light -sensitive tissue on the back of the eye. When looking from a distance target to a near target, the eyes must change focus. The eyes must also turn in towards each other to bring proper focus onto the near object (Convergence). This change in focus only occurs when looking from Distance to near. When looking up from near work, or near to distance, the eye un-focuses (releases accomodation) and the eyes straighten and the lines of sight go from being converged on a near target to being parallel again. The process of going from a position of convergence (looking at near) and accomodation (focusing at near) to being straight and unaccomodated for distance viewing is called divergence. The processes of convergence and divergence are controlled by the musculature surrounding the eye. These muscle actions for convergence and divergence are intertwined with the muscle that controls the focus for the lens of the eye so when the eye converges, the eye muscle focuses the lens for near and when the eye diverges, the eye muscle unfocuses the lens for distance. The eye muscles receive information for when to converge or diverge, direct the eyes to the left, the right, up or down based on information shared between the retina (image positioning information) and the nuclei (eye movement information). If an object passes to the left of you, the image of the object will fall on an area of the retina that corresponds to your left side. The nuclei will receive this signal and relay another signal to the eye muscles to look left in order to move the image of the object towards the area of the retina where the image is best viewed (the Fovea). Muscles inside the eye then control the process of accomodation and unaccomodation. When the act of focusing occurs, the mind assumes that a near object is to be viewed and convergence action kicks in. How does the mind know you are viewing a near target? When an object directly in front of you is brought closer to you, the image size of the object projected on the retina increases and the retinal image blurs. This slight amount of blur is the stimulus for the focus mechanism to kick in. Proximity of the object and blur are stimuli that activate the convergence/accomodation nuclei in the brain. The visual system transfers information about object proximity and blur to nuclei responsible for accomodation. Impulses are sent through the accomodation/convergence pathway. The impulses cause muscles inside the eye to increase the convexity of the lens of the eye. The increase in convexity increases focusing power, enabling focus at near. These stimuli cause accomodation for near and the eyes converge. When the object moves away from you, the image magnification on the retina decreases, the stimulus to converge and focus for near decreases as the eyes diverge to see the object at distance. The muscles in the eye cause the convexity of the lens to decrease, decreasing focusing power. This moves the point of focus out to distance. There is no convergence without accomodation and no accomodation without convergence. There is no divergence without unaccomodation and vice-versa.

A brief synopsis before continuing: To view objects at distance (greater than 20 feet or 6 meters), the visual system causes the focus mechanism to un-focus or relax. When looking at near, the vision system causes the lens of the eye to accommodate to focus on a near point. This accomodation is achieved by increasing the convexity of the lens of the eye. Accomodation is the process of moving the distance point of focus on the retina to the near point of focus by increasing or decreasing the convexity of the lens of the eye. To look at it in a different light (no pun intended) accomodation is the process of moving a distance point of focus to a near point of focus by increasing convexity of the lens. Spasm of accomodation, or pseudo-myopia occurs when the convexity achieved for the near point of focus “locks in” and won’t release again to view distance objects clearly. An example of “locking in” is seen in college students. Many patients in the late 20′s and early 30′s report having had perfect vision until sometime during or immediately after their college years. The first change they note in vision was blur at distance after reading, studying or hours of computer work. They report looking up from a book after a study session, then blinking a few times or squinting to see far away again. There far away vision gradually returned, but slower and slower until the distance vision was slightly blurry permanently. Then, going for an eye exam where the chief complaint they tell the doctor is distance blur, they are prescribed eyeglasses for distance, see better and become dependent on the glasses, but the whole time the near problem was never addressed. So, their vision blurs at distance, is tweeked in an eye exam and the problem continues. If the student had only told the doctor that the problem was the change in focus from distance to near, they may have been prescribed glasses to help them focus at near (reading or computer glasses). That may have solved the problem and halted a problem that gradually leads to a need for glasses at distance full time. Clearing someone’s distance vision is no-brainer for your eye-care professional. You could leave a patient alone in the examination room with the ‘better #1 or better #2 machine and within 5 minutes they could find a prescription that could clear the bottom line of the eye chart. The person determines whether 1 or 2 is better at distance, gets shown to the optical and another nearsighted person is created. The problem was not at distance, but at near. The blur is not the consequence of continued development of the visual system. It is the first sign of visual change secondary to false distance blur, or Pseudo-myopia. People concentrate on print or virtual pixel images 16 to 19 inches in front of their nose for hours on end. After focusing at near for extended periods of time, the focusing system may lock in on the near image. When the person looks up, the distance image appears blurry. The neurological signal to focus for near is not letting go and blur is caused by looking at the distance object through the near focus. The person is looking far away, but their eye hasn’t let go the focus from the book or computer screen! The person is unable to relax accomodation for near back to distance. When they go for an eye exam, often distance glasses are prescribed. Distance glasses clear blur, but the problem of near over-focus remains and the cycle of annual prescription changes and increases continues. If the near point vision problem is not addressed, the progression of pseudo-myopia will eventually lead to more dependence on the distance prescription. Real doctoring involves identifying the cause of the changing vision and making recommendations to slow the vision changes down, stop them or reverse them.

The latest research on myopia is showing that depriving someone of peripheral vision might be another cause of increase in myopic prescriptions. When we look out at a distance, we use our central and peripheral vision. When we look close to read or do computer work, we use less of our peripheral vision. Lack of stimulation of the periphery over long periods of time can lead to prescription “creep” if one is genetically geared towards myopia. In order to minimize the effect one should increase their reading distance or computer working distance.

Human beings are highly adaptable organisms. The body will alter function to accommodate needs for which the system isn’t able to compensate for. After enough use, the adaptation, if successful, may become part of the system for which it was meant to modify. Incipient nearsightedness brought on by focus problems is an adaptation our technological society is adopting. Most people in school or in white-collar occupations spend 6 to 10 hours of their waking day involved in near activities. Pseudo myopia, or false near focus is the bodies’ modification for increased need to see at near. For many of my patients, clear distance vision is needed only for driving to and from work and going to the movies. If we continue to evolve in this manner, our descendents will find no need for glasses continuously perched on the bridge of their noses anymore. People will be buying cars with prescription windshields. Of course, this is an exaggeration. In this day and age, the need for clear, comfortable, functional vision at distance is not as great as that at near. The old paradigm for prescribing glasses may need to be tossed out the window if we, as doctors, are to truly manage patients vision problems. As an eye care provider I feel a responsibility to identify and solve problems, instead of offering crutches (eyeglasses/contact lenses) for patients to become more and more dependent on. I’m talking about solid management of the underlying vision problem, not the symptoms alone.

Courtesy of the Doctors at Shady Grove Eye and Vision Care; Optometrists, Ophthalmologists and Opticians serving Rockville, Gaithersburg and Potomac Maryland suburbs of Washington DC.  For more information visit youreyesite.com.  Follow us @EyeInfo

NOT a patient of Shady Grove Eye and Vision Care

NOT a patient of Shady Grove Eye and Vision Care

 

 

Nutrition and Eye Health

Lycopene May Protect Against Eye Disorders

University of Maryland researchers suggest that carotenoids, particularly lycopene may protect the eye against oxidative damage and play a critical role in visual function. The identification of lycopene and a diverse range of dietary carotenoids in ocular tissues suggest that these carotenoids, as well as other nutrients found in tomato-based foods, may work in concert with lutein and zeaxanthin to provide protection against age related macular degeneration and other visual disorders.
Evidently, cooking and processing of tomato products makes lycopene more readily available to the body, indicating that there may be an added health benefit to eating processed tomato foods like tomato soup, pasta sauce and vegetable juices. Ohio State University researchers found that standard daily servings of tomato sauce, tomato soup, and V8 vegetable juice were each effective interventions to significantly increase blood concentrations of lycopene. Lycopene levels increased among study participants by 192% (pasta sauce), 122% (soup) and 92% (vegetable juice) respectively, and plateaued at a new baseline after only 14 days of consumption.

Eye itch and allergy*

Vitamin C (preferably as mineral ascorbates or ester C) 1000 mg (2 X day)
Quercetin 200 mg (3 X day)
Omega-3 Oils (EPA from fish or ALA from flaxseed) 1000 mg (3 X day)
GLA (borage oil or evening primrose oil) 300 mg (3 X day)
Catechins 2-3 cups of green tea every day
Vitamin A (in multivitamin) 5000 IU every day
Vitamin B6 (in B-complex vitamin) 50 mg every day
Zinc (usually in multivitamin) 15 mg every day
N-acetylcysteine (NAC-potent mucolytic agent) 500 twice a day.
Turmeric Extract (95% curcumin) 400 mg (3 X day)
Rosemary Extract (Rose Ox) 125 mg twice/day
*courtesy of Optometric Management, June 1999

Macular Degeneration

The AREDS study (Age Related Eye Disease Study) was designed to:learn more about the natural history and risk factors of age-related macular degeneration (AMD) and cataract and evaluate the effect of high doses of antioxidants and zinc on the progression of AMD and cataract. Results from the AREDS showed that high levels of antioxidants and zinc significantly reduce the risk of advanced age-related macular degeneration (AMD) and its associated vision loss. These same nutrients had no significant effect on the development or progression of cataract.

Vitamin Supplements for Macular degeneration Patients

AREDS Formula
(FAQ)
Note: AREDS formula contains beta-carotene which can increase the risk of lung cancer in smokers or ex-smokers.

Ocuvite PreserVision by
Bausch & Lomb
Icaps AREDS Formula by
Alcon
ProtectRx by
ScienceBased Health
VisiVite Original Formula by VisiVite
Viteyes Original Formula by Vitamin Health, LLC

AREDS Formula minus beta-carotene
(This formula is safe for smokers or ex-smokers. It provides all AREDS vitamins except beta-carotene)

Retinavites Smoker’s Formula
VisiVite Smoker’s Formula (has lutein)
Viteyes Smoker’s Formula (has lutein & zeaxanthin)
MaculaRx Plus (has 1/10th AREDS beta-carotene dose)

Lutein and/or Zeaxanthin Formulas
(AREDS formula does not have carotenoids as the study did not evaluate them.

Ocuvite Lutein
ICaps Lutein & Zeaxanthin Formula
ZeaVision (3 mg or 10 mg)

Information Courtesy of Illinois Eye and Ear Infirmary, University of Illinois

Vitamin C, Vitamin E, beta-Carotene (pro-Vitamin A) and Carotenoids (Lutein & Zeaxanthin) are strong antioxidants i.e. they protect the eye against free radical damage. It seems reasonable to assume that strengthening of the eye defences by increasing the intake of these vitamins would be helpful in preventing the chronic AgingEye diseases. Recent well designed and controlled studies seem to support this assumption. Lycopene (a different type of carotenoid found in tomatoes) protects against prostate cancer and heart disease – therefore the protective effect of these vitamins is not just restricted to the eye.

Courtesy of the Doctors at Shady Grove Eye and Vision Care; Optometrists, Ophthalmologists and Opticians working together to help you see better.  Serving the Rockville, Potomac and Gaithersburg Maryland suburbs of Washington, DC for over 45 years. For more information visit youreyesite.com or call (301) 670-1212 begin_of_the_skype_highlighting              (301) 670-1212      end_of_the_skype_highlighting

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Red, Dry Eyes – causes and treatments

Patients with dry eye, either from decreased tear production or increased evaporation of tears, most frequently complain of chronic sandy-gritty irritation in their eyes. Also, patients with dry eye typically note that their symptoms get worse as the day goes on. This is because eye closure during sleep forms a watertight seal over the tear film and gives the ocular surface a chance to recover. When the eyes open, evaporation begins, which increases tear-film osmolarity as the day goes on. If a person has these symptoms for more than 3 months and if the onset was gradual, the patient has dry eye unless the physician proves otherwise.

People with Meibomitis (known also as Posterior Blepharitis) also complain of chronic sandy-gritty eye irritation. But in these people, the irritation is worse upon awakening because the inflammation is in the eyelids. During sleep, tear production decreases, eye closure brings the inflamed lids right up against the eye, and the released inflammatory mediators act on the cornea all night, creating a symptom peak upon eye opening. When these people awake, tear flow increases, the lids pull away from the cornea, and their symptoms improve as the day goes on.

Eventually the chronic meibomian gland inflammation leads to meibomian gland dysfunction. When that happens, these patients develop a second peak in symptoms from dryness toward the end of the day. Finally, when the meibomian gland inflammation and secondary healing obliterate the meibomian glands, the morning symptoms resolve and patients are left with symptoms from dryness alone, with sandy-gritty irritation that gets worse as the day goes on.

Treatment of Meibomitis (Meibomian Dysfunction) and Dry Eye Syndrome

Many years ago, demulcents (polymers) were added to artificial tear solutions to improve their lubricant properties and change their viscosity. In 1975, a classic study demonstrated that demulcent solutions (all containing a preservative at the time) transiently increased tear-film stability in normal subjects. These solutions, whether of high or low viscosities, act by temporarily mimicking cell-surface glycoproteins, which are lost late in the disease. Solutions of higher viscosity remain in the eye longer. The effectiveness of preserved demulcent solutions hinges on their ability to temporarily stabilize the cornea-tear interface.

The next treatment advance – preservative-free demulcent solutions- occurred about 15 years ago, shortly after researchers recognized that preservatives increase corneal desquamation. A recent study showed that traditional preservative-free demulcent solutions improve but don’t normalize corneal barrier function in dry-eye patients. Improved corneal barrier function reflects decreased corneal epithelial desquamation and improved corneal cell junctions. Treatment with a preserved demulcent solution, while briefly increasing tear-film stability, actually diminished corneal barrier function. Preservative-free solutions established a new benchmark in artificial tear solution treatment.

Knowing what we know now about the mechanism and natural history of dry eye, we can anticipate that the next advance in treatment would address decreased conjunctival goblet cells, decreased corneal glycogen and elevated tear film osmolarity.  Thera tears is the first eye drop shown in preclinical studies to restore conjunctival goblet-cell density and corneal glycogen with four-times-a-day dosing for 12 weeks. A preservative-free demulcent solution the product accomplishes this effect through two mechanisms.   Reprinted From Optometric Management Magazine, February, 2002 Article written by Jeffrey P. Gilbard, M.D., N. Andover, Mass.

WHAT CAUSES CHRONIC EYE IRRITATION?

ANTERIOR BLEPHARITIS

Patients have crusting irritation at the base of lashes without variation throughout the day– onset is insidious.

MEDICAMENTOSA

Patients complain of burning and irritation without variation throughout the day. Symptoms are equivalent throughout the day because overuse of topical medications promotes damage. You should suspect this condition in all those who use traditional artificial tears more than four times a day. People generally have a history of escalating tear use.

LACRIMAL DRAINAGE OBSTRUCTION

Patients often have symptoms of tearing with actual and demonstrable tear overflow. Patients with meibomian gland dysfunction may feel like their eyes are tearing, but these patients have frank epiphora (overtearing).

ALLERGIC CONJUNCTIVITIS

The primary symptom for this condition is itchy eyes. Patients’ eyes may also exhibit increased mucus production. Onset of this condition is commonly seasonal, and it may be associated with hay fever, asthma and eczema.

NOCTURNAL LAGOPHTHALMOS

Patients’ eyes may burn upon awakening. Patients frequently have a history of lid surgery or thyroid eye disease.

SUPERIOR LIMBIC KERATOCONJUNCTIVITIS

Symptoms include burning and irritation without daily variation. Abrupt onset and remissions characterize this condition. Patients often have a history of thyroid dysfunction.

SUPERFICIAL PUNCTATE KERATITIS (THYGESON’S)

Patients with this condition experience insidious onset of photophobia, eye irritation and decreased vision. The condition is episodic and recurring.

DRY EYELID SKIN

Patients complain of “dry eyes.” This condition underscores the importance of accurate localization of symptoms.

TARSAL FOREIGN BODY

Patients experience a chronic sensation of having a foreign body in their eye. This sensation results from exogenous material or an exposed meibomian-gland derived conjunctival concretion (calcium deposit just beneath the conjunctiva that acts as a foreign body)

MUCOUS FISHING SYNDROME

Symptoms include chronic eye irritation, redness (particularly inferior) and increased mucus production. Patients who reach into their eye to remove mucus strands caused by conjunctival trauma (eye rubbing) initiate the condition. A vicious cycle can develop.

BLEPHAROSPASM

Patients may complain that their eyes feel “tired.” Careful questioning reveals that patients are experiencing an involuntary closure of the eyes, rather than eye irritation. Driving, reading and exposure to sunlight worsen symptoms.

NON-SPECIFIC OCULAR IRRITATION

Normal eyes, abnormal environment. Eye irritation in response to smoke would be a typical example.

NORMAL EYES WITH HYPOCHONDRIASIS

This condition is uncommon. A careful history that fails to mesh with the examination can provide the first clue to its presence.

DEMODICOSIS

An inflammation of the lids attributed to a common mite that inhabits the follicle of the lash, especially in the elderly. It has the potential to destroy the glandular cells, produce granulomas and plug meibomian glands. Symptoms include itching and burning, possible lid margin crusting and loss of lashes, along with the classic lash cuffing.
Reprinted from Optometric Management Magazine, February, 2002

 

 

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Shady Grove Eye and Vision Care; Optometrists, Ophthalmologists and Opticians serving the Rockville, Potomac, Gaithersburg suburbs of Washington, DC for eye exams and comprehensive family eye care for over 40 years. Fashion optical and veteran optician services available. The areas leadiong orthokeratology (orthoK) providers

Research Shows Sunlight Prevents Myopia

A recent study from Australia shows that around 10-14 hours of sunlight can reduce the risk of nearsightedness in children. Previous belief had held that the risk of myopia (nearsightedness) increased the more a child played with video games but research has never conclusively backed that up. Instead an indirect link may be found because those children who play with video games are at a higher risk of developing myopia merely because they are not getting enough sunlight.

The question was broached to the leader of this study, whether or not wearing sunglasses hindered the light from coming to the eye. According to Kathryn Rose, a leading international researcher of visual disorders “There is no evidence either way that wearing glasses has no effect or hinders the protective effect of sunlight, but this has not been studied systematically. Young children tend not to routinely wear sunglasses, possibly due to high rates of breakage and general intolerance to wearing glasses.” (Special thanks to CNN for that quote)

Courtesy of the doctors at Shady Grove Eye and Vision Care; Optometrists, Ophthalmologists and Opticians serving the Rockville, Potomac and Gaithersburg Maryland suburbs of Washington, DC for over 43 years. Visit our website at youreyesite.com. Connect with us on twitter @EyeInfo and “Like” us on facebook Connect with us on Twitter @EyeInfo and subscribe (free subscription) to this blog. Call (301) 670-1212 for office information and appointment scheduling.

FDA Recommends Sunglasses With 100% UVA/UVB Rating.

The Louisville (KY) Courier-Journal Share to FacebookShare to Twitter (7/28, Carter) reported that the Food and Drug Administration “recommends selecting sunglasses that are labeled with a UVA/UVB rating of 100 percent to get the most protection” from the sun’s harmful rays. The agency said consumers should also “try to find a wraparound style” that covers the eye socket completely. Children also need sunglasses; and parents should “check the label, remembering that toy sunglasses may not have any UV protection,” according to the FDA.

Courtesy of the doctors at Shady Grove Eye and Vision Care; Optometrists, Ophthalmologists and Opticians serving the Rockville, Potomac and Gaithersburg Maryland suburbs of Washington, DC for over 43 years. Visit our website at youreyesite.com.  Connect with us on twitter @EyeInfo and “Like” us on facebook Connect with us on Twitter @EyeInfo and subscribe (free subscription) to this blog.  Call (301) 670-1212 for office information and appointment scheduling

 

With My Family History, What Can I Do to Protect My Eyes?

Several blinding eye diseases have strong genetic ties. Knowing your family history is an advantage as there are several things one can do to reduce risk from an inherited eye disease. A common eye diseases with serious consequences that may be prevented to some degree by lifestyle changes is Macular Degeneration. Here are lifestyle changes you should consider if you have a relative with a history of macular degeneration:

UV Protection – UV exposure may increase risk of developing macular degeneration and may be a stimulus involved in the onset of the disease. Be sure your eyeglasses and sunwear is 98% or more UV protective and wear your sunglasses whenever you are outside. Blue light also has been implicated, so reducing the amount of light that reaches the back of the eye by wearing polarized UV sunwear is recommended by most eye doctor associations

Nutrition – Diets high in antioxidants, specifically the nutrients Lutein, Zeaxanthin and vitamins A, C and E help to reduce the risk of developing macular degeneration as determined by the AREDS study. Omega 3 fatty acids also are helpful in reducing risk of macular degeneration.

Regular Eye Care – Most of these diseases are detectable in their early stages through an eye exam by a state licensed optometrist or ophthalmologist. Early diagnosis and intervention is possibly the most important factor in how much vision you retain ultimately, so be sure to see your eye doctor regularly.

Courtesy of the eye doctors at Shady Grove Eye and Vision Care; Optometrists, Ophthalmologists and Opticians working together to serve you better.  Serving the Rockville, Potomac, Gaithersburg and Germantown Maryland suburbs of Washington DC for over 40 years.  Call (301) 670-1212 for appointment or visit our optical without an appointment.  Connect on twitter @EyeInfo.  Visit our website youreyesite.com for more information

Refractive Errors Most Common Vision Problems In Children

Medscape (10/11, Waknine) reports, “About 4% of preschoolers have myopia, 21% have hyperopia, and 10% have astigmatism, according to data from two studies supported by the National Institutes of Health and published in the October issue of Ophthalmology.” According to the studies, “refractive errors, such as myopia, hyperopia, and astigmatism, are the most common vision problems in children and are correctable with eyeglasses.” The first study was performed by researchers from the Doheny Eye Institute and the Department of Ophthalmology, Keck School of Medicine, University of Southern California-Los Angeles, and the Division of Ophthalmology, Children’s Hospital Los Angeles. The second study was conducted by investigators from the Doheny Eye Institute.

Courtesy of the doctors at Shady Grove Eye and Vision Care.  Optometrists, Ophthalmologists and Opticians serving the Rockville, Potomac, Gaithersburg and Germantown Maryland suburbs of Washington DC for over 50 years.  Connect with us on facebook and twitter.  Office hours by appointment (301) 670-1212.  Visit our virtual practice at youreyesite.com

How The Eye Works – A Fantastic Voyage Through The Eye

Vision is the product of sight. It is our interpretation of the world around us as seen through the eyes. Sight occurs when light reflected off an object travels through the various refractive elements of our eye and reaches cells of the retina which covers the back of the eye. The optics of the eye have shifted the original image upside down, so the picture of the image is actually inverted by the time it rests on the retina.  The retina is similar to the film in a camera. When light reaches the film, the image changes the molecular makeup of this film, creating a picture. The change of the molecules within the retinal “film” causes the nerve fibers attached to send the information through various channels deep within the brain. These channel signals interact with one another and interact with the retina in the other direction (channel to nerve fibers to retina). The criss-crossing of signals back and forth act to orient the eyes toward what you are looking at so the retina can receive the proper information and send it back to the brain. The signals finally reach an area of the brain called the cortex. The cortex is responsible for our interpretation of what we see. The cortex helps us to convert the light-image into a meaningful experience. As newborns, we start with only sight and no experience. It is not until we are able to interpret what we see that true vision takes place and it takes place in the cortex.

Prepare for a “fantastic voyage” through the eye. The journey is the same journey light rays that enter your eye from the computer screen take. Picture yourself as you read this hitching a ride on a light ray from a light source such as the sun or a light bulb. The light beam leaves the source as the journey begins. The light beam is reflected off your computer screen. The light reflected from the screen first encounters the tear layers that cover the front surface of the eye. The tears are composed of three layers. The first layer our light ray encounters is the exterior oily layer of tears. Small glands that line the eyelid margins are responsible for secretion of the oil layer. They are stimulated to secrete oil by blinking and when the two lid margins touch during a blink, they spread the oil over the surface of the eyes. The next layer our ray travels through is the water layer of tears directly beneath the oil layer. The purpose of the oil layer is to prevent the water layer from evaporation.  Traveling on, our light ray passes through the third and most posterior layer of the tears, the mucous layer. The mucous layer is a sticky layer that help the water layer adhere to the eye surface. Traveling beyond the mucous layer we encounter the front of the Cornea. The Cornea is the dome-shaped clear covering over the colored part, or Iris of the eye. The Cornea resembles a contact lens in appearance. The Cornea is responsible for most of the light bending (refractive power) of the eye. The light ray is bent more by the Cornea than any other structure in the eye. The Cornea is made of several layers. The first layer of the Cornea we travel through is the Corneal Epithelium, analogous to a thin transparent layer of skin on the surface of the Cornea. The Corneal Epithelium is a very thin layer, only about 5 cell layers thick. Next we encounter a very thin membrane called Bowman’s Membrane. The function of Bowman’s Membrane is unknown but is believed to be related to adhesion of the Corneal Epithelium. Much of Bowman’s membrane is destroyed in certain laser refractive surgeries without much consequence. Bowman’s membrane delineates the surface of the center of the Cornea, the Corneal Stroma. After squeezing by Bowman’s Membrane we enter the Stroma. The Stroma is made up of a matrix of collagen protein organized in structures called Beta-pleated sheets. The sheets are stacked so close and tight on top of one another, that light passes through the stroma unimpeded. The structure of the collagen sheets is why the Cornea is transparent to light. If the packing of cells is disrupted by fluid, trauma or infection, the Stroma may lose some of its transparency and this may cause our light ray to scatter. Exiting the Stroma our ray passes through another more posterior membrane similar to Bowman’s. This is Descemet’s membrane. Descemet’s membrane delineates a boundary between the Corneal Stroma and the next structure, the Corneal Endothelium. We pass through Descemet’s, into the Endothelium, which is composed of 1 thin layer of specialized cells responsible for pumping fluid out of the Cornea in order to maintain clarity. Osmosis is the tendency of fluid to move from areas of greater concentration to areas of lesser concentration. Since the back of the Cornea is bathed in fluid from inside of the eye (the Aqueous fluid, which we haven’t traveled through yet) there is a tendency of fluid to move into the Cornea. The Corneal Endothelium maintains the integrity of the Corneal Stroma by controlling osmotic influx of fluid into the Stroma from the Aqueous, keeping the Corneal Stroma clear and free of fluid. We pass through the Endothelium in to the Anterior Chamber of the Eye. The Chamber is filled with the Aqueous fluid that bathes the Endothelium, or back surface, of the cornea. The Aqueous fluid helps nourish the Corneal Stroma. Our light ray passes through the Aqueous humor. Directly in front of us it the Iris, or colored part, of the eye. The Iris is donut-shaped, with the hole being the Pupil of the eye. A lot of people are surprised to find out that the pupil is a hole and not a black spot. Our light ray will not touch the Iris, but go past it, through the pupil. The color of the Iris is a function of the amount of pigment deposited on its surface. The natural color of all Irises is blue. Green eyes have just enough brown pigment mixed in with the blue to give the appearance of green. The more brown the eye appears, the more pigment has been laid down on the iris. The Iris acts as a light regulator by manipulating the pupil size. The fibrous matrix that makes up the Iris is muscular and can expand, which enlarges the pupil to let more of our light ray into the eye or contract to let less light into the eye. In dim illumination such as nighttime, the Iris will expand so that more light can enter and we can see better. In bright illumination, the Iris contracts, making the pupil smaller so less light can get in and things won’t appear too bright. The Iris is analogous to the sphincter of a camera. We pass through the pupil on our light ray and the next structure we encounter head-on is the lens of the eye. The lens is a clear, convex structure located directly behind the iris. As our light ray passes through the lens, the shape of the lens changes by becoming more convex or less convex, adjusting to aim our light ray for focus on the back of the eye (Retina). The change in convexity is what is known as “focus”. The cornea provides the majority of focus for the eye, but corneal focus is fixed, that is, the cornea does not alter in curvature or convexity. Lens focusing is like a fine tuning mechanism and is what helps us bring blurry objects into focus. As our light ray leaves the lens of the eye, it enters the posterior chamber of the eye. The posterior chamber is filled with a gel-like substance called Vitreous Humor, or Vitreous. The Vitreous maintains the shape of the eyeball and holds the thin, sensitive nervous tissue in the back of the eye, the Retina, in place against the back wall of the eyeball. Assuming proper focus adjustment of the lens, our light ray travels through the Vitreous and heads directly for a part of the Retina called the Macula. The Macula comprises 10% of the Retina and is the area of the Retina light focuses on where we achieve our sharpest, most central vision. The Fovea is the center of the Macula. The fovea is analogous to the cross hairs of a tracking system. It helps the eye to move to lock object images onto the center of the macula. If the Fovea or Macula is damaged, anything we look directly at will appear blurry or rubbed-out. The Fovea is where the specialized cells that allow us to see in color are located. These cells are the Cone cells. The Fovea is tightly packed with cone cells. Most of the rest of the Retina is made up of Rod Cells. Rod cells help us differentiate shades of white and black. Images of objects in our side vision (peripheral vision) or objects viewed under poor lighting conditions are also transmitted through the Rod cells. Rod cells are responsible for our night vision. Our light ray has emanated from something we are looking directly at (the computer screen) the ray is focused on the Cone cells. Rod cells and cone cells represent a class of cells known as Photoreceptor cells. Photoreceptor means “receiver of light”. The Photoreceptors of the retina house molecules of visual pigment. When light is focused on a Photoreceptor, the energy of the light breaks down the visual pigment molecules within the Photoreceptor into simpler molecules. The breakdown of the molecules triggers an impulse. The Rod and Cone cells are attached to nerve cells. The light of the ray has triggered a chemical change that initiates an electrical signal within a nerve cell attached to the photoreceptor. The nerve cell transmits information from the Retina throughout the visual system. All the nerve cells of the retina converge to form a single nerve, the Optic Nerve. All visual impulses travel through the optic nerve in a highly organized fashion towards the brain. At some point along the voyage, the nerve from the right eye joins the nerve from the left eye. The point where the nerve fibers from the 2 eyes mesh together is called the Optic Chiasm. The nerve fibers traveling posterior to the Chiasm carry images from the retina of both eyes. The visual signals collated in the Chiasm are sent posteriorly through structures called Optic Radiations. Some visual information from both eyes travels to structures in the brainstem called Nuclei. The nuclei of the brain are responsible for chores such as eye movements to ensure images fall onto the fovea, balance and reflexes related to orientation as your eyes see it and many other things, including breathing! Coordination of vision with balance, reflex or motion is termed Motor Coordination. An example of Motor coordination is picking up a cup of coffee. The nuclei of the brain use visual information received from the cells in the retina about the location of the coffee cup and send out impulses. The impulses travel to the appropriate shoulder/arm/hand and an adjustment is made to coordinate the visual and motor systems together to achieve the desired goal, in this instance picking up the cup. Information on location is used from the Retina throughout the process as the hand travels toward its goal to fine-tune the reaching-for-the-cup process. If a target we need to see is off to the left, the light reflected from that object will land to the right of the Fovea. Images landing on the retina to the right of the fovea travel through nuclei responsive to stimuli for that area of the retina. The nuclei get directions on the location of the coffee cup from the Retina and guide the hand to reach for the cup. Information is exchanged from Retina to Nuclei and back as the hand reaches in order to accurately locate and grab for the cup. Imagine being on a platform slowly moving left to right past the coffee cup. As you reach for the cup, your arm would have to continually adjust to counteract the motion of your body in order to grab the cup. Information about movement of the image of the coffee cup on your Retina is transmitted to the motor system nuclei, which direct impulses to the arm and the hand to help make fine-tuning adjustments to grab the cup. Other visual signals are sent to the very back of the brain, the occipital lobe, where sight information is processed into units that are meaningful to us and are used for perception, or our interpretation of what we see. One image can be made of hundreds and thousands of these units, and the combination of these units provides us with the perceptual experience of what we view with sight. The information processed in the back of the brain allows us to understand that the object we are thinking about grabbing for is a coffee cup and not a sharp or dangerous object or something else.

Our light ray has traveled from the computer screen, through tear layers, through cornea, anterior chamber of aqueous, pupil, lens, vitreous humor and to the photoreceptors where the information reflected from the page was broken down into nerve signals and processed in the brain into meaningful units. Sight has been transformed from a mechanical process into a perceptual experience through the complexities of the brain and visual system.

Courtesy of the Doctors at Shady Grove Eye and Vision Care; Optometrists, Ophthalmologists and Opticians serving Rockville, Potomac and Gaithersburg Maryland suburbs of Washington DC. For more information visit youreyesite.com

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