What is Presbyopia?
Presbyopia, a condition causing difficulty in seeing up close, is one of the major reasons for vision problems, especially in older adults. In a study conducted in the Brazilian Amazon area, presbyopia was responsible for nearly 72% of all reported vision issues related to seeing things up close, while cataracts and a condition called pterygium accounted for 16.5% and 2.5% respectively. This observation is not just limited to this region but reflects a global trend.
Presbyopia is impacting over a billion people worldwide and with an increase in the aging population, this problem is growing rapidly. Health care professionals worldwide are working hard to effectively manage this situation using various non-surgical and surgical methods. The following report will talk about these various ways of correcting presbyopia.
What Causes Presbyopia?
Presbyopia is mostly caused by a gradual decrease in the ability of the eye’s lens to focus on near objects. Several theories have been suggested that describe how presbyopia works, including the Helmholtz’s theory, Schachar’s theory, and the Catenary theory of Coleman.
According to the Helmholtz’s theory, when the ciliary muscle (a ring of muscle in the eye) tightens, the fibers (called zonules) that connect the ciliary muscle to the lens relax. This causes the front surface of the lens to become more curved, helping us focus on close objects.
Schachar’s theory, on the other hand, believes that when the ciliary muscle tightens, the fibers around the middle of the lens are pulled tight, but the fibers at the front and back relax. This makes the middle part of the lens bulge out, while the edges become flatter.
The Catenary theory of Coleman suggests that when the ciliary muscle tightens, it creates a shift in pressure from the back of the eye (vitreous compartment) to the front (aqueous compartment). This makes the front surface of the lens curve.
Other theories also exist, like Tscherning’s theory and Baikoff’s theory.
In short, all these theories explain that the front central part of the lens becomes more curved when our eyes focus on something close, which is a process called accommodation.
Risk Factors and Frequency for Presbyopia
People generally start dealing with presbyopia, a condition that affects your eyes’ ability to focus on near objects, once they hit 40. This is a condition that primarily impacts individuals who are economically active. Unfortunately, the majority of people suffering from this condition in developing nations don’t have access to corrective measures such as reading glasses. This is due to a lack of knowledge about the condition and financial limitations. The problem exists even in developed countries, where many people who have presbyopia do not use glasses to help with their vision.
- In a study conducted in the United States, it was found that 13.6% of participants presented near visual impairment (difficulty in seeing objects up close), and nearly 26% experienced significant issues with their near vision.
- An Australian survey revealed that about 21.6% of non-indigenous Australians and 34.7% of indigenous Australians had difficulty with near vision tasks.
Signs and Symptoms of Presbyopia
People around the age of 40 may find it harder to read small print at a normal reading distance. They often find that they can see better if they hold the material a bit further away than usual. Headaches are a common complaint when these symptoms start. In people who look at screens for long periods, these symptoms, called asthenopic symptoms, can show up earlier because of problems with eye focusing.
- Trouble focusing on close-up and distant objects
- Squinting
- Feeling sleepy while doing close-up work
- Needing brighter light for reading
For example, people who sew a lot for their work may find it difficult to thread a needle.
Testing for Presbyopia
Presbyopia is a condition that affects your ability to focus on things that are close up. This condition is common as we age. In this case, the closest point at which you can focus clearly (this is known as the near point of accommodation or NPA) moves further away than the typical reading distance. The NPA is measured using a tool called the Royal Air Force (RAF) rule, which also helps to determine the range of focus or “amplitude of accommodation.” As you age, this range decreases, making it harder to focus on close up objects.
To check for presbyopia, your doctor will ask you to try to read at your normal reading distance. Then they will add special lenses to help you see better. The lens that gives you just enough power to clearly read the last line on a reading chart at your regular reading distance is the strength of eyeglasses prescription you will need. This process is how your doctor determines which glasses you need for presbyopia.
Treatment Options for Presbyopia
If you’re having difficulty seeing clearly due to aging, there are several options for eye treatment available to you. Two categories exist in general: non-surgical options like glasses and contact lenses, and surgical methods.
Non-surgical options:
One simple solution to presbyopia (the inability to focus on nearby objects as you get older) is wearing spectacles. Single vision lenses are cost-effective and allow you to read close-by objects. However, if your vision is blurred even at a distance, you might have to switch between two different glasses. An expensive but more convenient alternative is bifocal lenses, which correct both close and distance vision problems. But bear in mind that with bifocal glasses, your intermediate vision might still be blurry. To solve this, you can consider progressive lenses, which provide a clearer view for all distances, but these are usually the most expensive. Note that both bifocal and progressive glasses might initially cause nausea and dizziness, but these side effects often disappear after 2 to 3 weeks of use.
Bifocal lenses come in various types based on their make (how they’re constructed) and design. Some bifocal lenses are fused, solid, or cemented, and others consisting of two separate lenses held together in a frame. Designs can be straight-top, round-segmented, executive, or Kryptok in which the transition is not visible from outside, making it aesthetically pleasing. However, image distortion can happen with all these designs.
Another option is contact lenses. Two approaches are available: monofocal lenses, which correct one eye for close vision and the other for distance (this is called monovision), and multifocal lenses. The latter are specially designed to correct distance, intermediate, and near vision.
Surgical options:
There are various surgical procedures performed on the cornea (the clear front surface of the eye) to treat presbyopia. One such procedure involves using a laser to reshape the cornea for clear vision at all distances. But this may cause slight degradation in the quality of vision. Other viable options include conductive keratoplasty, where heat is used to reshape the cornea, and corneal inlays – tiny devices inserted into the cornea to improve near vision. However, certain corneal treatments can be difficult to reverse.
Another surgical approach involves altering the sclera, the white part of the eye. Implants can be inserted into the sclera to improve focus. However, the scientific data supporting the effectiveness of these methods is limited.
For patients with severe vision problems, intraocular lens implants are an option. Certain intraocular lenses can correct both near and distance vision. Some people may choose to get a clear lens extraction, where their natural lens is removed and replaced with an artificial one. An implanted artificial lens can correct both presbyopia (trouble seeing near) and ametropia (errors in refraction).
There are even multifocal lens implants that can improve your visual acuity at different distances. However, these can potentially cause loss of light and may affect visual clarity. Recently, lenses that provide extended depth focus or quadrifocal lenses have also been developed to improve vision quality for varying distances.
What else can Presbyopia be?
The conditions that can impact your close-up vision include:
- Macular/retinal diseases – You may still have impaired vision even with corrective glasses. Scanning the retina may show any irregularities.
- Diseases of the optic nerve
- Posterior subcapsular cataract – Unlike with the age-related eye condition presbyopia, bright light can make your near vision even worse.
- Hypermetropia, also known as farsightedness
- Astigmatism, which is when your eye isn’t completely round, causing blurred or distorted vision
What to expect with Presbyopia
Presbyopia is a common eye condition that typically begins around 40 years of age. It’s a normal part of ageing that everyone experiences. Those affected by it usually find it easier to see clearly by using glasses or contact lenses. There are also surgical options for presbyopia that have been generally well-received.
Possible Complications When Diagnosed with Presbyopia
If presbyopia isn’t corrected, it can lead to more than just a hard time reading things up close. It can also cause fatigue and headaches. Luckily, these symptoms typically go away once the presbyopia is treated.
Common Symptoms of Unfixed Presbyopia:
- Difficulty reading at close range
- Tiredness
- Headaches
Preventing Presbyopia
If you’re having trouble reading things up close, it might be best to start using aids for presbyopia, a condition often related to age that makes close-up tasks like reading difficult. Using these aids early can help you avoid symptoms of eye strain. However, it’s not recommended to opt for very high-level corrections immediately. By using moderate aids, you’re actually helping your eyes to use some of their remaining flexible focusing ability for a longer period of time.
