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Presbyopia

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What is Presbyopia?

The human eye is one of the most fascinating optical instruments in the world. It is the organ of sight in the human body. The eyeball is spherical in shape. It is a wonderful and self-adjusting organ because it can control the amount of light entering it by decreasing or increasing the size of the pupil. The eye lens can also change its thickness to alter the focal length, depending on the distance at which the object is situated. This is known as the power of accommodation. 

However, an eye can develop certain defects depending upon a variety of factors such as age, nutrition, genetics etc. 

Presbyopia is a condition in which the eye loses its ability to focus on nearby objects. It is usually a result of ageing. People can develop symptoms of presbyopia at around 40 years of age or so. The simplest indication of this is the inability to read newspapers, or facing problem in using mobile phones or reading text messages. Presbyopia is not a disease, it is a condition which is almost inevitable. It can affect people who have never faced any sight-related problems in their entire life. In fact, even those who suffer from myopia (short-sightedness) may have to deal with a blurring vision even after using lenses or glasses. 

Causes of Presbyopia 

As mentioned above, presbyopia is essentially an age-related change. In this condition, the natural eye lens becomes stiffer and loses its flexibility. 

The protein of which the eye lens is composed undergoes changes, because of which the lens begins to lose its elasticity. Changes also take place in the muscle fibres that are present around the lens. As the elasticity and flexibility of the lens diminish, it becomes increasingly difficult for the eye to focus on nearby objects. 

Presbyopia Diagram 

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Presbyopia Symptoms 

A presbyopic person has to hold objects, books or other materials at a suitable distance from their eyes in order to have a clear look at them. However, as the distance between the eye and the object is increased, its size also reduces. Therefore, this is not the solution. 

In certain cases, it may be possible to clearly see nearby objects, but being presbyopic can cause headaches, strain the eyes and lead to fatigue. These symptoms make reading and writing a very arduous task.

Correction of Presbyopia 

  1. For people over the age of 40, eyewear fitted with progressive lenses are used to help with the condition of presbyopia. These lenses are multifocal and provide nearly a clear vision. 

  2. As an alternative, people can also use glasses fitted with bifocal lenses. However, these are not very useful as they limit the range of vision for people suffering from presbyopia. 

The only difference between progressive lenses and bifocal lenses is that bifocal lenses have a line separating the concave and convex parts. No such visible differentiating line is present in progressive lenses. 

  1. The ageing process causes certain changes in the eyes. Presbyopic people may become more sensitive to light. Glare can cause discomfort to them. For this reason, photochromic lenses may be used, as they automatically become dark when exposed to sunlight. 

  2. Reading glasses can also be used, however, they cannot be worn all day long. On the other hand, bifocal lenses and progressive lenses can we wear throughout the day without any inconvenience. Reading glasses can only help when the person wants to read something, or wants to see a print clearly. 

There are many lenses available to deal with presbyopia. However, one must ensure that the lenses they are using should have an anti-reflective coating. This coating removes reflections that can produce glare. 

  1. Apart from lenses being used in glasses, contact lenses are also available. People suffering from presbyopia can make use of multifocal contact lenses. Monovision is a contact lens correction technique. In this, one eye wears a contact lens with a distant prescription while the other one has a lens with a near vision prescription. 

  2. There are people who do not like to wear eyeglasses or contact lenses. For them, a number of surgeries are also available to treat presbyopia. Corneal inlay implantation is an example of such a procedure in which the depth of vision is enhanced, the requirement of glasses is eliminated without causing any damage to the quality of distant vision. 

FAQs on Presbyopia

Q1: Which Lens is Used to Correct Presbyopia?

Solution: The problem that one faces in presbyopia are similar to the one faced by a hypermetropic eye. To correct this defect of vision, people can use simple eyewear fitted with convex lenses. A convex lens is a converging lens. It bends the incoming light rays by a greater degree, so as to enable them to form the image on the retina. Some people may also prefer to wear contact lenses in places of eyeglasses. However, there are cases in which a person suffers from both presbyopia and myopia. In such a situation, bifocal lenses should be used instead of a convex lens. A bifocal lens has two surfaces- one of which is concave while the other is convex while the other is concave.  Convex is present in the lower part and concave is present in the upper part. 

Q2: How to Cure Presbyopia?

Solution: Apart from the wide range of lenses and glasses available in the market, there is an option to undergo surgery to cure presbyopia. The basic aim of the treatment is to restore the lost flexibility and elasticity of the eye lens. 

The following surgical procedures can be adopted to permanently cure presbyopia:

  1. Conductive keratoplasty: Heat is applied to spots near the cornea. As the edge of the cornea shrinks, its curvature increases, thereby increasing the focusing ability.

  2. LASIK: The inner layer of the cornea is removed to enhance the curvature of the cornea. 

  3. LASEK: A flap is created in the outer epithelium of the cornea. Then, lasers are used for enhancing the curvature.

  4. PRK: the epithelium is completely detached from the cornea, and then lasers are used for reshaping it.