Introduction and Symptoms
Presbyopia, also known as laohua (老花) or old flower, is a condition where the eye loses the ability to adjust its focus.
The first symptoms of presbyopia usually occurs at about 40 years old, where near work or reading starts to get difficult, either by being blur, having to strain to see clearly, or holding near objects like your mobile phone further away in order to see clearly and comfortably.
While it can be unnerving at first, this is a normal process of ageing - something that we all go through.
Presbyopia affects us differently - which is why some of us seem to be more affected (or as some claim, "don't have presbyopia at all"). Read on and we will make it clear for you.
Vision Simulation for your easy understanding
If you currently wear single-vision spectacles to correct your distant, far, or driving vision, this simulates your vision with the glasses:
If you don't wear any glasses and distance vision is clear, this also simulates your vision:
Note that distance vision is clear, but near vision is blur.
We can correct the blur at near using single-vision reading glasses - spectacles with lenses that are made just for reading purposes. The following simulates such a pair of glasses:
Note that the distance vision is blur, while the near vision is clear.
For people with myopia of about -2.00 (200 degrees) or so, this would also be the vision when no spectacles are worn, i.e. by removing the single-vision distance glasses, you will be able to see near clearly. This is why myopia is also known as short-sightedness - the ability to see short distances well.
Besides reading glasses, you can also opt for progressives, also known as multifocals or varifocals. These lenses incorporate both the distance and near prescriptions, blending them seamlessly into one pair of spectacles.
This is the simulation of a progressive lens:
Note that both far and near vision is corrected, however, there is blur (sometimes we refer to it as unwanted astigmatism or distortions) towards the sides of the lenses. This blur increases the further one views towards the sides.
This periphery (side) blur is normal for progressives, and is the result of putting different kinds of prescriptions into one lens. The central vertical area remains clear, with the upper portion for viewing distant objects, and the lower portion for viewing near objects.
We often call the central vertical area the "corridor" of the lens.
Hence, you may hear of terms such as short corridor or long corridor, where the change of prescription from distance to near (top to bottom of the lens) is quicker or slower respectively. You may also hear of wide-corridor or corridor optimisation - this is where more parameters of the prescription, frame choice, purpose of use, and wearer feedback can be used to adjust the way the lenses are made, to allow for a wider or more comfortable viewing area and angle.
One less common term you might hear is "freeform", which means that the lenses are made-to-order rather than being pre-molded, which gives us more options in personalising or customising the lenses to the wearer, resulting in better vision, comfort, and a higher success rate.
Here is a graphic simulation of the difference in corridor width between a basic progressives and a freeform or optimised progressives.
Do note that this is just for illustration purposes. The blur area comes on gradually and is not opaque (or grey), and can differ depending on the prescription, corridor length, and other factors. Also, different wearers will have different visual expectations and therefore will not have the same comfortable viewing area, i.e. a wearer who expects very sharp vision may feel that the corridor is narrower, and vice versa.
Your experience here
At Otago Optical, we will give you advice according to your vision and lifestyle needs, and you can make the decision on which type of progressive lenses you prefer, as well as any optional add-ons that you may prefer. It is our founding principle to not unnecessarily upsell pricey products. We have always maintained fair and transparent prices, and will continue to do so.
Before you run away, how about checking out some of our frames, or go on ahead to read more informative posts? We do trendy quality glasses at affordable prices, and we're always happy to post useful stuff to help you make an informed decision when it comes to your spectacles and vision. Thanks for your support!
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