Presbyopia, commonly known in chinese as “Lao Hua Yan”, is the gradual loss of the ability of the eyes to focus on near objects with age.
Presbyopia starts at about 40 years old. Some may experience this at a later age but everyone will have it with age.
Presbyopia is caused by the stiffening of the natural lens with age as well as weakening of the muscle fibres which support the lens. These factors together result in the reduced ability of the eyes to focus up close.
The eye focuses on close up objects through a process called “accomodation”. During this process, the muscle fibres supporting the lens get activated and changes the shape of the natural lens in the eye. This change in shape of the lens increases the focusing power of the lens and allows for the ability to focus on objects at different distances.
Presbyopia is a loss of the focusing ability that comes with age.
Myopia (short-sightedness), hyperopia (long-sightedness) and astigmatism (San Guang) are refractive errors of the eye that occur even in children.
Presbyopia will occur in the context of these various refractive errors of the eye.
Symptoms of presbyopia include:
- Difficulty reading (Books, newspapers, phone, computers): Words appear blurred at a normal reading distance
- Needing to hold these objects further away from you in order to see better
- Eye strain and headaches with prolonged reading or other forms of near work
Myopia, also known as short-sightedness, is a refractive error of the eye that commonly occurs due to the eyeball being too long. As a result, light from an object focuses in front of the retina (the film of the eyes) instead of on it.
Without glasses, a myopic patient can still see up close but will find objects in the distance blurry.
A patient with 250 degrees of myopia, objects at about 40cm from the eye remains clear.
A patient with 500 degrees of myopia, objects at about 20cm from the eye remains clear.
In Singapore, up to 70% of our population may be myopic.
A myopic patient is used to seeing near objects clearly without glasses. With the onset of presbyopia, the presence of myopia helps to compensate for this loss in ability to focus for near objects, hence some of these patients may mistakenly think they never had presbyopia because they could always read clearly by removing their glasses.
When the myopia is treated with laser vision correction, the presbyopia becomes “unmasked” and this patient would suddenly be aware of the need for reading glasses.
Hyperopia, also known as long-sightedness, is a refractive error of the eye that commonly occurs due to the eyeball being too short. As a result, light from an object focuses behind the retina (the film of the eyes) instead of on it.
Without glasses, a hyperopic patient can still see clearly for far because the muscles fibres of the eye are activated to bring the focus onto the retina. The eye is already working hard focusing while looking at a distant object when it should be in a relaxed state.
For near objects, if the amount of hyperopia is small, the eye can still work harder to focus the image on the retina. However, if the amount of hyperopia is too much, the eye is unable to focus despite its best efforts and may need glasses to see better.
A hyperopic patient’s eye is already hard at work focusing images on the retina even in the “resting state”. With the onset of presbyopia, the eye would need to work even harder to compensate for this, tapping on whatever “reserve” it has. Naturally, the onset of presbyopia seems to be earlier in these patients compared with myopic patients
Astigmatism occurs because the shape of the cornea is more curved in one direction than in the perpendicular direction. The eye is shaped more like a rugby ball rather than a soccer ball. As a result, light passing through the cornea does not focus on a single point and causes visual distortion.
Astigmatism can exist alone or together with myopia or hyperopia.
Monovision is a means to address presbyopia by utilising the concept that myopia allows a patient to see clearly for near even if the ability to focus is lost due to aging.
The dominant eye is corrected for distance vision and the non-dominant eye is corrected for near work (e.g. leaving a low amount of myopia).
Eye dominance can be assessed using the following method:
- Stretch out your hands and make a “good” sign with the thumb up
- Keeping both eyes open, find a target across the room (e.g. a cross or door knob) and place the thumb under the chosen target.
- Now, close your left eye. If the target remains above the thumb, your right eye is the dominant eye
- To confirm, repeat by centring the target with both eyes open again. Now, close your right eye. The target should “move” and is no longer nicely above your thumb.
- Conversely, if you close your right eye and the target remains above your thumb, your left eye is the dominant eye.
Advantages of monovision include:
- Freedom from reading glasses
- Enables repeated change in the range of focus without fumbling with glasses
Disadvantages of monovision include:
- Mild decreased depth perception
- Noticing blurred vision in the eye corrected for near when looking at distant objects
- Some may need a short period of adaptation for the brain to “learn” to see with the correct eye for tasks at different distances
Amblyopia, the proper term for lazy eyes, occurs only in children. It is due to the incomplete maturation of the visual system in the brain before the child reaches about 8 years old and can be caused by various factors including untreated high degrees (myopia, hyperopia or astigmatism), squint (drifting of the eyes) or anything blocking the visual pathway (e.g. congenital cataract).
“Lazy eyes” which persist past 8 years old into adulthood is usually deemed untreatable and conversely, once full maturation of the visual pathway occurs past 8 years old into adulthood, it does not deteriorate and become “lazy”.
Monovision can be achieved with glasses, contact lenses, laser vision correction, implantable contact lenses or intraocular lenses.
Various types of glasses can be used to treat presbyopia: Monofocal glasses, Bifocal glasses and multifocal glasses.
- These are reading glasses that have lenses which correct for near vision only
- With these glasses on, objects at far or intermediate ranges are out of focus
- These are good for patients who require good near vision for extended periods of time
- Non-prescription over the counter reading glasses are cheaply available but be informed of the disadvantages of these glasses:
- They do not take into account your individual IPD (Interpupillary distance)
- They do not correct for other refractive errors and astigmatism
- They can cause headache, eye strain and nausea due to the above factors
- These are good for patients who need to alternate between far and near vision
- There are 2 points of focus: The upper part is for distance correction and the lower part if for near correction
- There are various designs available e.g. D Segment, Round Segment, Ribbon Segment, Executive
- Many dislike them because the obvious segment for reading makes them look old
- These are also known as progressive addition lenses (PALs) or progressive glasses
- They allow focusing of objects at different distances through different prescriptions with a smooth transition from distance to near
- There is no visible line dividing the distance and near power
These lenses are expensive and may require some time for adaptation
Various types of contact lenses can be used to treat presbyopia: Soft contact lenses, Rigid Gas Permeable (RGP) contact lenses, Bifocal contact lenses, Multifocal contact lenses.
Soft contact lenses and Rigid Gas Permeable (RGP) contact lenses can be used to achieve monovision with the power for the dominant eye corrected for distance and the power for the non-dominant eye corrected to allow near vision.
Bifocal and Multifocal contact lenses function in a similar way to bifocal and multifocal glasses with different zones designated for distance vision and near vision. Some time may be needed for adaptation and some may experience the visual phenomena of glare and halos.
With any contact lens use, proper hygiene must be observed to avoid potentially blinding complications.
Laser vision correction comprise of various surgeries including PRK, LASIK and SMILE. These procedures together with ICL surgery are able to correct the various refractive errors in the eye and also utilise the concept of monovision to address presbyopia: The dominant eye is corrected for distance and the non-dominant eye is corrected for near.
These methods of correction are more permanent compared with use of contact lenses. They enable freedom from glasses and also avoids the potential complications from contact lens use.
Read more about these surgeries in the respective FAQ page.
Intraocular lenses (IOLs) are inserted in the eye after cataract surgery. The natural lens in the corrects about 2000 degrees in the eye and after its removal during cataract surgery, there is a need to replace it with a lens to correct this degree otherwise very thick glasses will be needed to see well after surgery.
IOLs come in various forms including: Monofocal IOL, Multifocal IOL, Extended depth of focus (EDOF) IOL.
Monofocal IOLs help the eye focus for either distance or near. The amount of myopia left in the eye can be targeted to utilise the concept of monovision and address presbyopia.
Multifocal IOLs have been specially designed to have different zones to allow for distance, intermediate and near vision. These lenses are able to correct the various refractive errors in the eye (myopia, hyperopia and astigmatism) and treat presbyopia at the same time.