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Tuesday, November 29, 2022
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    To see or not to see

    CNA – The prescription glasses and contact lenses that have helped you to see far are now failing you when you’re trying to decipher your Whatsapp messages. You can’t read anything without holding it at arm’s length. You’ve probably enlarged the font size of this article to read it properly. Fine print on labels? Don’t bother trying if you have your glasses or contact lenses for myopia on.

    These are confounding times because just when you thought the myopia you have been living with for the better part of your life has stabilised (your prescription may have remained unchanged for years), you now have a new vision problem to deal with: Presbyopia.

    “As presbyopia is an age-related condition, it cannot be prevented or delayed,” said Clinical Associate Professor Mohamad Rosman, a senior consultant ophthalmologist heading Singapore National Eye Centre’s Refractive Surgery Department and Laser Vision Centre.

    “Everyone will develop presbyopia once they are 40 to 45 years old. Some may experience the symptoms earlier than others,” he said.

    If you’re of east Asian descent, watch out. “Genetically, people of East Asian ethnicity may develop presbyopia at an earlier age than Caucasians,” said Dr Natasha Lim, a senior consultant and the medical director of Dr Natasha Lim Eye Centre at Royal Square Novena.

    WHAT ARE THE DIFFERENT LENSES AVAILABLE?

    For many myopic people who develop presbyopia in middle age, the vision correction required is double fold: To facilitate far and near sight. Here’s a look at the options available:

    Single vision lenses

    Pros: These single vision lenses (otherwise known as reading lenses) are designed with only one prescription to give you clear vision for a specific reading distance, said Jack Chan, an optometrist with Eyecare People.

    “The advantage of using readers is that it has a wide reading area, meaning your vision is generally clear in most directions of gaze,” said Chan.

    Cons: These lenses aren’t designed for far vision, so they aren’t helpful if you have myopia. In fact, when looking far, you’ll have to remove your readers or look over the top of the glasses. “Most wearers don’t like to constantly put on and take off their glasses,” said Chan. “Not only is it troublesome, it also reveals their age.”

    Progressive lenses

    Pros: With progressive lenses, you’ll only need one “all-day, multi-purpose pair of glasses”, said Chan – and no one can tell that you’re using presbyopia lenses. That’s because progressive lenses seamlessly incorporate “distance, intermediate (50 to 80 centimetres) and near (less than 50cm) vision zones” into a singular lens.

    Unlike bifocal lenses, progressives don’t have a distinct line or area that denotes the different powers for far and near vision.

    “Progressive lenses, multifocal lenses and varifocal lenses all refer to the same type of lenses. They are just known differently in different countries or named differently by the companies that produce them,” explained Alex Ong, an optometrist at Ong’s Optics and Contact Lens Centre.

    Cons: You may require “a short adaptation period” as your brain and eyes adjust to the new focussing points that the progressive lenses offer, said Chan. Also, compared to readers, progressive glasses have a smaller reading zone.

    Office lenses

    Pros: Office lenses – also known as occupational or deskbound lenses – are mainly for near and intermediate uses such as reading and looking at the computer screen, according to Ong. “You don’t have to tilt your chin up as with some progressive lens designs when using the computer. This greatly improves comfort for long hours of computer work, especially when a person requires more than one screen.”

    Cons: “Compared to progressive lenses, office lenses only have ‘two layers’ for intermediate and near vision only,” said Ong, and they don’t let you see further than your computer screen. So they may not work as well when you’re catching the bus or trying to read the menu on the wall.

    HOW DO YOU DECIDE AND WHAT CAN YOU EXPECT?

    You’ve got to admit, the costs of these specialised lenses aren’t low. So how do you make the right choice?

    “It depends on your lifestyle and work requirements,” said Ong. “If you are driving most of the time and only use the handphone or read the newspaper for a short while, then progressive lenses are a good choice. However, if you’re required to look at near tasks for very long hours, office lenses are a better option.”

    Even so, do your homework on the lenses, said Ong. Take, for example, progressive lenses, which are the most popular lens choice for those with presbyopia. “All progressives have a specific design and different designs can cater to different visual requirements. The main difference boils down to the size of the usable zone of the lenses.”

    Your frame choice plays a part, too, when it comes to progressives. It is important that the frame can accommodate the lens’ entire range of vision, noted the Essilor website. For that, choose frames that are at least 28 milimetres tall.

    The lens shape is just as important; aviator and cat-eye frames tend to cut off the bottom portion of the lens’ prescription and results in the loss of your reading vision. So look for frames with rounded edges such as horn-rimmed, retro wingtip, circular or oval ones.

    For first-timers to progressives, give your eyes and brain time to learn how to “drive this new car”, said Chan. “Some adaptations on how we use our eyes and head movements are required.” In the meantime, it is not uncommon for you to initially feel giddy or feel the need to “find” a clear zone in the lens, Chan said.

    If it is a matter of wrong prescription, the tell-tale sign is either blurred near or far vision, said Ong. “However, many a times, the discomfort from progressives comes from the fitting.” For instance, the lenses should be positioned in a way where, when you look straight ahead, the centre of each pupil should be in the optical centre of each lens.

    “Usually for first-time wearers, it is highly recommended to start early with a lower presbyopia power,” said Ong, to make the progressive lenses easier to adapt to. “As you age and require higher reading power, the adaptation will be faster. Also, for first-time wearers, it will be good to wear the progressives consistently for at least a week to get used to the progression of power in the lenses.”

    But if you’re still struggling after two weeks, go back to your optometrist or optician, advised Chan. “Take note of what you are experiencing, where the lenses are working and where they’re not, and explain what you are experiencing.“

    From there, we will usually be able to offer solutions to resolve the problem, which can involve the frame, prescription or lens design adjustment; others could be a case of needing more time to adapt to this new correction,” said Chan.

    What about naysayers who claim that you’ll have to choose between near and far sight because you can’t have the best of both worlds? “Generally, you can achieve good far and near vision,” said Ong, “with a pair of progressives.”

    The caveat is, there may be “some form of distortion at the peripheral parts of the lenses and those are the areas that might not be clear to a user”, said Ong. “However, one should be able to see clearly far and near with glasses, even if it means using two different pairs of single vision spectacles.”

    WHAT ARE THE OPTIONS FOR CONTACT LENSES?

    According to Dr Rosman, there are two main methods for correcting presbyopia using contact lenses: Multifocal contact lenses and monovision contact lenses. “Multifocal contact lenses have different designs, the main ones being the concentric, aspheric and segmented,” he said.

    Multifocal contact lenses are a marvel as they can correct myopia, astigmatism and presbyopia all in one lens. However, they do have a limit based on the brands and models; some brands may not have prescriptions for myopia or astigmatism beyond a certain degree, said Dr Rosman.

    “Presbyopia can increase to a maximum of about 300 degrees. Some of the lenses may be able to correct up to 200 degrees and others up to 250 degrees,” he said.

    On the other hand, “monovision means one eye (usually the dominant eye) is used for distance vision while the other eye is used for near vision”, said Dr Rosman. This is done by using monofocal contact lenses or the very contact lenses that you already use for correcting myopia.

    To create monovision, “in the dominant eye, the myopia is fully corrected while the other eye is left slightly myopic so that it can be used to see near objects”, said Dr Rosman. For those who can’t tolerate monovision, both eyes may then be under-corrected. “This will mean that there will be a reduction in your distance vision but you can still have some degree of near vision,” he said.

    As for the pros and cons of monovision contact lenses versus multifocal contact lenses, here’s the breakdown:

    Monovision contact lenses

    Pros: Usually not affected by brightness, unlike multifocal contact lenses, said Dr Rosman.

    Cons: Can reduce 3D perception and the ability to gauge distances, according to him. Patients may also experience eye strain when they use near vision (such as reading and using the computer) for long periods of time.

    Multifocal contact lenses

    Pros: Better depth perception as compared to monovision, said Rebecca Li, an optometrist and a senior manager with Johnson and Johnson Vision’s Professional Development and Education, Asia Pacific. “The general recommendation for early presbyopes is to start with multifocal contact lenses.”

    Cons: Not suitable for those with unstable prescription or astigmatism from -0.75DC onwards, said Li. Bright light helps with near vision but if you’re in a dimly lit place such as a restaurant, multifocal contact lenses may not work as well.

    Whether you’re getting monovision or multifocal contact lenses, you’ll have to undergo a refraction test to determine your distance and near prescriptions. “This is followed by a fitting using trial lenses to see how well they fit and how is your vision when wearing the contact lenses,” said Ong.

    For first-time contact lens wearers, Li recommended giving yourself a few days to adapt to them. “This is essential and to be expected, similar to how adjustment is needed for multifocal glasses. Your eyes need time to adjust to the new vision and mode of correction.”

    “If you’re already a contact lens user, you should be able to adapt to them almost immediately. However, due to the variation of power in the lenses, you might need a week to fully feel ‘natural’ wearing them,” said Ong.

    He pointed out that presbyopia contact lenses aren’t suitable for those with very dry eyes. The same goes for those who have undergone Lasik or who have their corneas reshaped.

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