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Posted on by Dr. Sherman Tung

20/20 Vision

When having an eye exam done you might have been told that you have 20/20 vision, but what exactly does that mean? To put it simply, having 20/20 vision indicates that at a distance of 20 feet, you are able to see the smallest letters that should be seen at 20 feet. If you have 20/40 vision, it indicates that you need to be at 20 feet to see what a person with 20/20 vision can see at 40 feet. On the other hand, if you have 20/15 vision, you can see at 20 feet what a person with 20/20 vision can see at 15 feet.

How do we measure our visual acuity?

There are many ways to measure a patient’s visual acuity, but the most common way is through using a Snellen chart that presents with numerous lines of letters above one another. Letters found at the top of the chart are larger and easier to see but become smaller and difficult to read as you move down the chart. Patients are tested by covering one eye and reading the letters from top to bottom at which point they repeat these steps while covering the other eye. Afterwards, patients will use both eyes together to determine the lowest line they are able to read clearly.

Posted on by Dr. Melody Tong

Retinal detachment? Retinal tears? Retinal holes?

Photo by Tamara Bellis on Unsplash

What is it?

The retina plays an important role in providing us our vision. Sometimes we can have a retinal detachment which results in the retina pulling away from its normal position resulting in vision loss. It is also possible to have retinal holes and tears which results in a break in the retina and the accumulation of fluid resulting in a detachment occurring. This can result in someone having symptoms of blurred vision, flashes of light, a curtain veil blocking some of their vision and floaters covering their vision.

photo credit: vistaeyeclinic.com

Who is at risk and how do you treat it?

Individuals who have had previous eye surgeries, high nearsightedness, or trauma to the eye or head will also increase the chance of a retinal detachment occurring. Age also plays a factor in this as the vitreous gel found in our eye shrinks overtime and can pull away from the retina resulting in a possible hole or tear. Yearly dilated eye exams are done to help detect and prevent retinal detachments from occurring. It is especially important that you see an optometrist if you have any symptoms of flashes of light or floaters in your vision. Different treatment options exist such as laser therapy, cryopexy and surgery which are chosen depending on the severity of the detachment, hole, or tear.

Posted on by Dr. Elisa Xiao

How can I have Dry Eye if my eyes feel watery?

Photo by Pascal Chanel on Unsplash

Tearing

Tears are needed to keep the eye’s front surface healthy and to maintain clear vision. It is
common to temporarily produce excess tears when you are emotional, laughing, coughing,
vomiting, experiencing strong taste sensations, or yawning.

Types of Tears

photo credit: allaboutvision.com

Different types of tearing consist of basal tears, emotional tears, and reflex tears. Basal tears are your basic functional tears. They are released in tiny amounts to lubricate your ocular surface and keep it clear of any dust. These are vital for good vision and comfort. Emotional tears are triggered by strong feelings such as joy or sadness. Reflex tears result from irritation in the eye by foreign bodies, or from the presence of irritant substances in the environment. They can also occur with bright lights hot or peppery stimuli to the tongue and mouth, when we yawn, cough or even vomit. These types of tears are released in larger amounts than basal tears. Their goal is to protect one’s eye.

How can I have Dry Eyes if my eyes are so watery?

The two common causes of watery eyes are blocked tears ducts and excessive production of tears. The common cause of excessive production of tears is dry eye syndrome. This occurs due to the glands around our lid margins not producing enough oil resulting the tears drying up very quick. This lack of lubrication results in our eyes producing an abundance of tears to compensate.

Posted on by Dr. Melody Tong

Is it true that eating carrots can improve my vision?

Photo by Nick Fewings on Unsplash

It is often said that eating carrots will help you see better due to the high amounts of vitamin A. Although vitamin A plays an important role in our vision, it is unable to improve the quality of our vision. Vitamin A is able to prevent diseases such as macular degeneration which can result in severe vision loss if left untreated.

What is Vitamin A?

Vitamin A is derived from beta-carotene which acts as an antioxidant. This is essential in protecting our cells against heart disease, cancer, and many other diseases. Deficiency in vitamin A is the leading cause of preventable blindness in children across the world. Due to this, it is important to have some type of source for vitamin A such as carrots, eggs, spinach, or broccoli.

What does Vitamin A do for our eyes?

Vitamin A allows us to produce pigments needed in-order for the retina to function properly. Without these pigments, it would become much more difficult to see in the dark leading to eventual night blindness. Lack of vitamin A can also lead to a lack of nourishment to the cornea resulting in the eyes not producing enough moisture to keep the cornea lubricated. This can lead to our eyes becoming dry which can result in severe complications such as ulceration of the cornea and eventual blindness if not appropriately treated.

Posted on by Dr. Elisa Xiao

Ever wonder how you’re able to perceive color?

Photo by Greyson Joralemon on Unsplash

The Basics

Color vision is an important part of human visual perception, and it is possible due to the photoreceptors in the retina. The human eye consists of two basic photoreceptor cell types, rods, and cones. Rods are responsible for vision in dim light, and cones are responsible for bright light and enable perception of color. Individuals with normal color vision have three subtypes of cones with different wavelengths corresponding to their peak absorption. Found in the central part of the retina are the cones that are sensitive to either red light (long wavelengths ~555nm), green light (medium wavelengths ~530nm) and blue light (short wavelengths ~ 426nm). Normal color processing consists of the cones registering different colors and sending information through the optic nerve to the brain. This enables us to distinguish countless shades of color.

Color Vision Deficiencies

Color vision deficiency or known as color blindness could be congenital or acquired.
Congenital color deficiencies are typically bilateral and non-progressive, and acquired is
more likely unilateral and progressive. The types of color deficiency include red-green
deficiency and blue-yellow deficiency. Individuals with severe color vision defects lack
the photopigment to see color completely while others with a mild color vision defect
have a reduced sensitivity to certain colors. The degree of dysfunction varies between
individuals, mildly affected individuals may pass some of the less sensitive color vision
tests such as Farnsworth D-15 hue test. The most common type of color deficiency is red-
green deficiency. Color vision deficiency can be diagnosed through a comprehensive eye
examination. Testing that can be performed in clinic include, pseudoisochromatic tests,
arrangement tests (ex. Farnsworth D-15) and anomaloscope.

photo credit: colorblind-test.io/ishihara-test
photo credit: color-blind-test.com/d15-color-blind-test-more

Treatment and Implications

Color vision deficiency can be frustrating and may limit participation in occupations that include being able to differentiate between colors. Few examples include pilots, truck drivers, law enforcement, and policing. There is no cure for inherited color deficiency. However, using specifically tinted eyeglasses or wearing red-tinted contact lens on one eye can increase some people’s ability to differentiate between colors.

Posted on by Dr. Sherman Tung

Is it okay to buy glasses online? Do I really need an optometrist/ optician?

Photo by wu yi on Unsplash

When considering whether to buy your glasses online, at first it may seem more convenient and likely less costly. But the prescription given to you by your optometrist is only one piece of information that will determine how effective your glasses will be in improving your vision. Let’s consider the pros and cons:

Pros of buying online:

  • Wider selection of styles and colors
  • Many choices between different websites
  • Often can save on cost (but more on that later)

Cons of buying online:

  • You miss out on having a trained professional aid you in ensuring your glasses are the right fit in
    terms of comfort and effectiveness
  • Quality control of frames may often be sacrificed to maintain that low price you see online
  • Specific measurements such as PD, finding the best optical center, and measurements for
    progressives will either often be wrong or not available for online retailers
  • Prescription issues in general occur much more commonly when ordered online as opposed to
    in person

What could initially be seen as a way to save time and money in the first place may end up more costly for both in the long run if any of the above issues occur. In addition, common complaints with improperly selected glasses may include: headaches, fatigue, nausea/dizziness, eyestrain, glasses slipping off the nose, and pain/pressure marks on your nose/around the ears. Those with high prescriptions, children, complicated prescriptions, and multifocal prescriptions should especially consider in person options as opposed to online.

Posted on by Dr. Sherman Tung

What reading under the covers does to your eyes

Image by Freepik

While it is untrue that reading in the dark will permanently damage your eyes it can cause shorter term issues. You may have to strain harder which can lead to headaches, irritated eyes, general eye fatigue. If this is coupled with other existing issues you may also experience blurry vision or even double vision temporarily. The extra strain and need to focus may also prevent you from blinking as often, leading to dry eye symptoms.

Posted on by Dr. Elisa Xiao

Will I Develop Presbyopia?

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Presbyopia is the gradual loss of your eyes’ ability to focus up close. This tends to start around your early 40s and progresses until around the age of 65. You may notice starting to hold reading material further away to keep it clear, blurry vision at previously normal reading distance, eyestrain or headaches after extended periods of reading.

Managing presbyopia

Depending on your health, lifestyle and preferences, your eye care specialist may suggest any of the following methods to correct presbyopia:

  • Eyeglasses in the form of readers, bifocals, progressives, etc.
  • Contact lenses, typically multifocal or monovision
  • Surgeries
  • Eye drops such as Vuity

Can I prevent presbyopia?

You can’t prevent presbyopia since it’s a part of the natural aging process. You can, however, take steps to protect your eye health. This includes:

  • Wearing sunglasses to shield your eyes from harmful ultraviolet (UV) rays.
  • Eat foods rich in nutrients that promote eye health, including vitamin A, vitamin C, vitamin E and lutein, and Omega-3s
  • Improve lighting in work areas
  • Increase font and change contrast in smart phones or computer devices etc.
Posted on by Dr. Sherman Tung

Can I Wear my Contact Lenses for Longer than I’m Suppose to?

Photo by Lensabl on Unsplash

If I’m careful with cleaning, can I wear my dailies for more than 1 day?

Daily disposables are thinner and are made of a material that is not made to resist bacteria and buildup. So, if you try to clean or disinfect these thin lenses you may actually create breaks instead, further increasing infection risk. Using a compatible brand of soft contact lens rewetting drops to hydrate your daily disposables for comfort is acceptable.

What happens if I wear dailies for more than 1 day?

Wearing daily disposable contact lenses more than once puts you at risk for discomfort, dryness, corneal ulceration/scarring, and eye infections.

Differences between Dailies, Bi-weeklies, and Monthlies

Dailies are worn only for one day and discarded when you remove them, these are typically very thin and have a high water content. Natural deposits from your eyes build up easily on their surface, and they cannot be reused. This could mean more convenience but also, depending on how often you replace them, more costly.

Monthly or bi-weekly contact lenses are thicker than daily disposables. The thicker composition makes them more durable and long-lasting, and they are usually more resistant to drying out. However, they must be disinfected regularly in order to ensure healthy wearing.

Posted on by Dr. Melody Tong

What does my eye prescription mean?

Photo by Josh Calabrese on Unsplash

Eyeglass and contact lenses prescriptions can contain components and abbreviations that may be harder to decipher. Here are some of the common abbreviations and what they mean:

  • OD: or oculus dexter refers to your right eye
  • OS: or oculus sinister refers to your left eye
  • SPH: is the sphere and refers to the lens power required to help correct your vision. A (-) negative
    indicates nearsightedness and (+) positive indicates farsightedness
  • CYL: is the cylinder and refers to how much astigmatism you have if any. Astigmatism is caused
    by a cornea or lens that has a different shape than normal and multiple focal points.
    Astigmatism is very common.
  • AXIS: a number between 1 and 180, indicates exactly where the astigmatism appears on your
    eye
  • ADD: stands for the additional lens power needed to make it easier for you to read. This is seen
    on prescriptions for reading glasses or the lower portion of bifocal/progressive lenses
  • BO, BI, BU, BD stand for base out, base in, base up, and base down. These refer to the position
    of the prism on eyeglasses that correct double vision

For contact lenses you may see additional information such as the brand, mode of wear, and BC +
DIA.

  • BC: The base curve is the measurement that indicates the curvature and shape of your contact
    lenses. This is taken when the steepness or flatness of your cornea is measured.
  • DIA: The diameter is the measurement of the length that your contacts need to be to
    completely cover your cornea.