Presbyopia

A Brief Overview

What is it?

Presbyopia is an eye condition associated with age which results in the inability to focus up close. This condition occurs naturally due to the hardening of the natural lens and the effects aging have on the muscle fibers in the eye making it difficult to focus on close objects (nei.nih.gov, 2010, p.1, para. 4). The image below illustrates the difference between a normal eye and an eye with presbyopia. We can see that the image of the presbyopia eye is formed behind the retina which causes the inability to focus on close objects.

Presbyopia of the Eye

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Normal Vision VS. Presbyopia

The structure of a human eye consists of the pupil, iris, lens, cornea, ciliary muscle, sclera, choroid, fovea, retina, optic disc, and optic nerve (Breedlove & Watson, 2013, p. 292). Visual processing starts in the retina and then the optic nerve sends information via the thalamus to the cerebral cortex and visual perception occurs. In those with presbyopia, visual processing occurs behind the retina, the lens hardens, and the ciliary muscles become weaker (Goldstein, 2014, p. 25). This causes images far away to appear clear and images closer to appear blurry as shown in the photo below.

Vision with Presbyopia

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How Vision is Processed

As previously mentioned, visual-information processing starts in the retina. Photoreceptors within the retina then release neurotransmitter molecules that will later connect with ganglion cells in the optic nerve (Breedlove & Watson, 2013, p. 292). But before visual-information processing can begin, there must be a stimuli. Light reflected from the stimuli enters the eye through the pupil and is focused by the cornea and lens and the image of the stimuli is then formed in the retina. Below is a diagram that illustrates the process of forming an image of the stimulus in the retina.

How the Eye Sees

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Gestalt Principles


How vision is processed is quite different than how we perceive images. The perceptual system does not determine an object’s image on the retina but rather to determine the object that created the image.


1. Good continuation: points seem to belong together and are seen as a smooth line or curve.

2. Good simplicity: a stimulus pattern is seen in a way that the resulting image is as simple as possible.

3. Simplicity: similar things are grouped together.

4. Proximity: things that are close to each other appear to be grouped together.

5. Common region: things that are within the same region of space appear to be grouped together.

6. Uniform connectedness: a connected region of the same visual

properties, such as lightness, color, texture, or motion, is perceived as a

single unit.


Presbyopia distorts our perception of objects as it causes closer objects to become blurry while objects further away are clearer.


(Goldstein, 2014, pp. 102-104).

Treatment for Presbyopia

The easiest form of treatment is prescription glasses which higher focusing power in the lower portion of the lens (nei.nih.gov, 2010, p. 1, para. 8). Reading glasses are also available to purchase without a prescription.You can also opt for prescription contact lenses or surgery such has Lasik, the Kamra inlay, or conductive keratoplasty.

References

Breedlove, S.M., & Watson, N.V. (2013). Biological psychology: An introduction to behavioral, cognitive, and clinical neuroscience (7th ed.). Sunderland, MA: Sinauer Associates, Inc.


Goldstein, E. B. (2014). Sensation and Perception (9th ed.). Belmont, CA: Wadsworth.


Facts Bout Presbyopia. (2010). Retrieved April 6, 2016 from: https://nei.nih.gov/health/errors/presbyopia