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Author: Dr. Sherman Tung

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. Sherman Tung

How do my eyes adjust to different lighting?

Photo by Agence Olloweb on Unsplash

Our eyes are incredible at adapting to different lighting conditions. This is done through the iris and pupil of the eye. Our pupils are the dark hole at the front of the eye which allows light to enter and form an image on the back portion of our eye. This pupil size is controlled by muscles found on the iris, which is the coloured portion surrounding the pupil. In bright sunlight, our pupils will begin to constrict, allowing less light to enter into the eye. On the other hand, when we are in a dark room our pupils will become bigger and increase the amount of light getting into the eye.

credit: https://www.sciencelearn.org.nz/resources/50-how-the-eye-focuses-light

Once the light enters through our pupil, it hits the back of our eye called the retina. The retina has two types of photoreceptors called rods and cones. Rods are responsible for night time vision and cones are responsible for day time vision. When we are in a dark room, rods are the ones that let us see.

Dark adaptation

The reason you are momentarily blind in the dark when going from a well-lit room is because it takes some time for our eyes to adjust. This is referred to as dark adaptation. During this period, the rod receptors are the key players to fully adapt and return vision to normal.

Posted on by Dr. Sherman Tung

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

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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. Sherman Tung

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

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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. Sherman Tung

Interested in Refractive Eye Surgery?

Photo credit: iris.ca

In the case of nearsightedness, farsightedness, astigmatism, or presbyopia refractive surgery can help either reduce or eliminate the need for glasses/contacts and improve vision. Good candidates include:

  • Patients with stable unchanging refractive errors
  • Patients with thick healthy corneas and good overall ocular health
  • Patients whose lifestyle/expectations match the surgery they choose

Candidates may have limited options or should avoid refractive surgery if they have:

  • thin corneas
  • severe dry eye
  • extreme levels of myopia, hyperopia, or astigmatism
  • corneal scars
  • cataracts
  • history of eye infections or an active eye infection
  • diabetes
  • glaucoma

What to expect with refractive eye surgery

Before your surgery, your optometrist will:

  • Discuss options and expectations associated with the different types of refractive eye surgery
  • Test your vision
  • Measure the surface and thickness of your cornea
  • Double check if any other existing conditions may complicate or prevent a successful outcome

During your surgery, your doctor will:

  • Instill numbing eye drops
  • Instill devices around your eyelids to prevent blinking
  • Have the patient will stare at a target light to prevent from moving
  • Clicking sounds, duration, other details may vary between different types of surgeries

After your surgery, you will:

  • Use a see through shield to protect your eye while it heals for a few days
  • Apply eye drops to reduce dryness and promote healing
  • Experience varying amounts of scratchy/burning sensations temporarily

Be sure to discuss with your eye care provider about the varying types of refractive surgery options and if they are right for you. Some of these include: LASIK, PRK, ICL, LRI, SMILE etc.

Posted on by Dr. Sherman Tung

Ever Heard of Computer Vision Syndrome?

Photo credit: healthjade.net

Almost everyone is guilty of spending an excessive amount of time on a screen and it is very common to feel symptoms of eyestrain and fatigue associated with digital use; this is known as Computer Vision Syndrome (CVS) or digital eye strain. As the name implies, excessive screen use causes stress on your eyes after reading or staring at a digital device for hours at a time. Some common symptoms of computer vision syndrome include eyestrain, headaches, dryness of the eyes, neck pain, and blurred vision over time.

Since it is unrealistic for us as optometrists to expect patients to avoid computers or excessive screen time, what are some ways to alleviate symptoms and avoid exacerbation of CVS? It is helpful to assess your desk or workstation for proper lighting and working distances. It is also important to be mindful of one’s posture throughout the day and ensure you are wearing proper visual correction such as glasses or contacts to avoid further eyestrain.

Photo credit: Ergomaker.com

Tips for avoiding eye strain

  1. Decrease the brightness of your screen
  2. Avoid letting yourself get closer to the screen throughout the day
  3. Take breaks (every 20 minutes look at something 20 feet away for 20 seconds)
  4. Wear an office or anti-fatigue lens while working
  5. Remember to blink consistently
  6. Stay hydrated

Following these simple tips will not only improve the way your eyes feel, but will naturally improve productivity, efficiency, and well-being throughout the day.

Posted on by Dr. Sherman Tung

Do I Need a Contact Lens Fitting?

Image by rawpixel.com on Freepik

Why do I need to be fitted for contact lenses? Did you know your glasses prescription is different from your contact lens prescription? When an optometrist fits you for contact lenses, they are ensuring several things:

  • Your eye is healthy enough to be wearing contact lenses. Conditions such as dry eyes and allergic conjunctivitis need to be treated before you can wear contact lenses. Eye conditions such as corneal scars, dystrophies, and/or irregular surfaces may require a fitting with specialty lenses.
  • The contact lens is the right type for your life style. Based on your occupation, extracurricular activities, and other needs, we can help you determine whether dailies, bi-weekly, or monthly contact lenses will meet your needs.
  • Finding a comfortable fit with good vision. We take measurements of your eyes to fit you in a comfortable lens. Many companies make contact lenses, and each have a set of parameters they work with. We can check if a lens is too tight or too loose on your eyes, how the contact lens moves when you blink, and whether it is centered on your eye. We also ensure each eye sees well both at a distance and near.

In addition, we first train new contact lens wearers on how to safety insert and remove contact lenses. We will go over the cleaning process, to ensure that lenses are handled safely because any buildup of proteins and debris on the lenses can cause damage to the cornea.

Posted on by Dr. Sherman Tung

Blink-A-Boo!

Photo by Taylor Sondgeroth on Unsplash

Blinking is an involuntary reflex which does not require much thought throughout our day. Even though blinking seems simple, it is very important. And believe it or not, there is a correct way to blink.

Why is blinking so important?

  • Protects our eyes from debris and foreign objects
  • Creates a smooth surface for light to enter our eye and land on our retina for clear vision
  • Keeps our eyes moist and spreads tear film evenly

The 20/20/20 Rule

Our blinking pattern can be disrupted throughout the day when we are staring at a screen for too long and doing continuous near work. Optometrists recommend the 20/20/20 rule for everyone, especially those with too much screen time. The 20/20/20 rule means taking a break every 20 minutes to look 20 feet away for 20 seconds.

There is a right way to blink

We want to ensure that when we blink, it is a complete blink. This means that our top eyelid should touch our bottom eyelid. It is very common for people to blink only halfway or not close their eyes completely while asleep. This can be a problem since it exposes the bottom half of our eye and does not allow our tears to be expressed as efficiently. As you may guess, this leads to dry eye symptoms.

Incorporating the 20/20/20 rule and being more conscious about the way we blink can go a long way in helping our eyes feel less dry throughout the day.

Posted on by Dr. Sherman Tung

What’s That Floating In My Vision?

Photo by Al Soot on Unsplash

Many patients are concerned about a constant “black dot” floating in their line of sight. Most tend to notice that it worsens when looking at a blank wall, bright lights, or the sky. Although quite bothersome, it is a very common complaint.

The eye is filled with a gel-like substance called vitreous, which allows the eye to keep its shape. Over time, the proteins within this gel begin to clump up and solidify, leading to formation of “floaters”.

Floaters can occur in one eye or both eyes. Typically, floaters are a benign finding. However, it becomes worrisome when the vitreous is strongly adhered to and pulls on the retinal layers. It could potentially lead to retinal holes, tears, or potentially a retinal detachment. These occurrences could be detrimental to vision, so it is important to see your optometrist immediately if these symptoms arise.

Symptoms to look out for:

  • A sudden increase in the number of floaters
  • Flashes of light
  • Curtain over vision

How are floaters treated?

Unfortunately, there is no way to remove floaters unless you surgically remove the entire vitreous. This procedure has more risks than benefits and it typically not done to treat this condition. The good news is that, with time, the brain gets accustomed to the floaters and is able to ignore them, allowing them to become less bothersome and noticeable.