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Presbyopia is a natural eye defect in which the eyes gradually loses the potential to focus on objects that are close to the eyes. This eye disorder affects everyone with the natural ageing process. When seeing an object, the light from that object enters the eye, it passes through the cornea, then, it passes through the pupil. The Iris is the coloured part of the eye that opens and closes the pupil to adjust the amount of light that passes through it. Light after crossing the pupil passes through the eye lens. When the eye is in a healthy state, the lens changes its shape so it can bend the light rays further and focus them on the retina at the back of the eye. Our lens becomes less flexible as we age. Then, it can’t change or adjust its shape as easily as when we were young. Hence, the lens is unable to focus the light properly to concentrate it on the retina.
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Key Terms: Presbyopia, Eye Defect, Myopia, Hypermetropia, Eyes, Pupil, Ciliary Muscles, Convex Lens, Eye Lens, Retina, Vision, Bifocal Lens
What is Presbyopia?
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Presbyopia refers to a natural eye defect which is the gradual loss of the eye’s ability to focus on nearby objects. Presbyopia is completely a natural defect that comes with the ageing process. The effects of Presbyopia usually becomes noticeable in the early-mid-40s of people and continue to worsen until around age 65.
Presbyopia can be confirmed easily with an eye test and can be corrected with eyeglasses or contact lenses.
Presbyopia
The video below explains this:
Human Eye One Shot Detailed Video Explanation:
Also Read: The Human Eye and The Colourful World
Types of Presbyopia
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There are five different types of presbyopia for which are details are as follows:
- Incipient Presbyopia: Incipient presbyopia is a type of presbyopia that happens in the early stage in which symptoms are noted. In this stage usually, the patient has trouble reading small prints, but the patient may perform well on testing and may reject near vision notes.
- Functional Presbyopia: Functional presbyopia is a type of presbyopia in which patients usually faces difficulties with near vision. The age at which this occurs varies and depends on environment, task requirements, nutrition, or general health.
- Absolute Presbyopia: Absolute presbyopia is a problem where there is a gradual and continued decline in accommodation and it is the next stage after functional presbyopia. At this stage, little accommodative ability of eyes remains.
- Premature Presbyopia: Premature presbyopia is the appearance of the disease at an earlier age than expected because of nutrition deficiency, environmental cause, or disease-related pattern. Pharmaceuticals can also be one of the causes of early presbyopia.
- Nocturnal Presbyopia: Nocturnal presbyopia happens when accommodation power decreases in low-light conditions.
Also Read: Myopia
Causes of Presbyopia
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In our eye, the crystalline lens is located just behind the iris and the pupil. There are tiny ciliary muscles in our eyes that pull and push the lens, adjusting its curvature, and hence adjusting the eye's power to bring objects into the focus area.
As a person starts growing old, the lens becomes less flexible and elastic, and the muscles become less powerful. Because these changes result in a lesser adjustment of the lens of the eye for various distances, close objects will appear blurred.
In presbyopia patients loses the elasticity of the lens of the eye. There is also a loss of adjustment power of ciliary muscle and loss of elasticity of the zonules that connect the ciliary muscle to the lens, however, is also believed to contribute to the problem. One of the major symptoms of presbyopia causes the inability to focus on objects close to one hand.
Causes of Presbyopia
Symptoms of Presbyopia
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The advanced symptoms of presbyopia start occurring around the age of 40 for most people. The symptoms of presbyopia typically involve a gradual reduction in the ability to read or do work up close.
Common symptoms of presbyopia are:
- People face eye strain or headaches after reading or doing close work
- Facing difficulty in reading small print
- feels fatigued from doing close work with screen
- People need brighter lighting when reading or doing close work
- These people hold reading material at an arm’s distance to focus properly on it
- overall problem in seeing and focusing on objects that are close to you
- Squinting issue
Blurred Near Vision- A Symptom of Presbyopia
Hypermetropia, or farsightedness, is also a situation that has symptoms that are very similar to presbyopia. However, they’re two different disorders. In both cases, objects at distance are clear, but objects closer to eyes appear blurred. Hyperopia occurs when the eye size is shorter than normal people or the cornea is too flat to adjust the lights. With these malformations, the light rays focus behind the retina, as in presbyopia.
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Treatment of Presbyopia
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Presbyopia cannot be cured through surgery, but physicians can guide patients by prescribing them reading glasses like bifocal, or trifocal eyeglasses. A convex lens can be used to focus the light coming from far to get focus in front of the eye. Glasses divided in half can be a problem, which leaves the top open and uncorrected for distance vision. Bifocals lens can give the same output by allowing correction of other refractive errors (improper focusing of images on the retina of the eye).
Together with glasses, contact lenses can be useful in the treatment of presbyopia. Technicians of contact lens makers need to take a look at the patient's medical history to ensure the patient has received the right contact lenses. Some lenses require great care, so each patient's expectations need to be resolved before any lens is prescribed to them.
The two common types of contact lenses prescribed by doctors for presbyopia are bifocal and monovision contact lenses.
Lenses Used For Treatment of Presbyopia
Things to Remember
- Presbyopia is an eye defect that involves a gradual loss of the eye’s ability to focus on nearby objects.
- With the growing age, the eye lens becomes less flexible and elastic, and the muscles become less powerful resulting in a lesser adjustment of the lens of the eye for various distances, thus, the close objects will appear blurred.
- The major symptoms of presbyopia include the inability to focus on objects close to one hand and difficulty in reading small prints.
- For the treatment of Presbyopia, reading glasses like bifocal, or trifocal eyeglasses are used by the affected person.
Sample Questions
Ques. What are the defects of presbyopia? (3 Marks)
Ans. Presbyopia is caused by changes in the focusing and adjustment power of the lens in the eye. With age, the elasticity of the lens becomes less flexible and hard, making it more difficult for the eye to focus on close objects. Presbyopia is a vision defect that occurs due to the weakening of the ciliary muscles of the eye lens
Ques. What are the three types of eye defects? (3 Marks)
Ans. There are mainly three common refractive defects of vision. We classify them as:
- Myopia or Near-Sightedness: One can not see far objects clearly in this condition.
- Hypermetropia or Farsightedness: One is not able to see nearby objects properly in Hypermetropia.
- Presbyopia: The flexibility of the eye lens reduces thus causing the near point to move away.
Ques. How does presbyopia affect the eye? (3 Marks)
Ans. If you have presbyopia, the lens will get inflexible and will not be able to adjust to focus light properly, so the point of focus falls behind the retina (bottom image). This makes close-up objects appear blurred. To form an image of an object properly, the eye depends on the cornea and the lens to focus the light reflected from objects.
Ques. What is presbyopia and how is it corrected? (3 Marks)
Ans. A person with a presbyopia problem will not be able to read letters without glasses. It may also be possible that a person suffers from both myopia and hypermetropia. This type of defect can be treated by using bi-focal lenses. A bifocal lens consists of both a convex lens (to correct hypermetropia) and a concave lens (to correct myopia).
Ques. How to correct the eye defect presbyopia? (3 Marks)
Ans. Presbyopia eye defects can be treated using options including wearing corrective eyeglasses (spectacle lenses) or contact lenses, undergoing refractive surgery, or getting lens implants for presbyopia. Some of the prescribed glasses are:
- Prescription reading glasses
- Bifocals
- Trifocals
- Progressive multifocal
- Office progressives
Ques. How can I prevent presbyopia naturally? (3 Marks)
Ans. We can follow the following steps to avoid the defect of presbyopia:
- Eating balanced meals.
- Should drink enough water around 7-8 glasses every day.
- One should protect his/her eyes from UV rays.
- After working, take a break from work and rest the eyes.
- Whenever you feel strain in the eyes, take a break.
Ques. Which lens is used for presbyopia? (3 Marks)
Ans. People suffering from presbyopia need a convex lens for reading purposes. The convex lens needs the service of an optometrist specialised in its preparation. A convex lens can be used to focus the light coming from far to get focus in front of the eye. Bifocals lens can give the same output by allowing correction of other refractive errors (improper focusing of images on the retina of the eye).
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