Presbyopia

Last updated

Presbyopia
Other namesThe aging eye condition [1]
Pesto ingredients - blurred.jpg
Pesto ingredients.jpg
A person with presbyopia cannot easily read the small print of an ingredients list (top) compared to someone without presbyopia (bottom).
Specialty Optometry, ophthalmology
Symptoms Difficulty reading small print, having to hold reading material farther away, headaches, eyestrain [1]
Usual onsetProgressively worsening in those over 40 years old [1]
CausesAging-related hardening of the lens of the eye [1]
Diagnostic method Eye exam [1]
Treatment Eyeglasses, [1] contact lenses [2]
Frequency25% currently; [3] all eventually affected [1]

Presbyopia is physiological insufficiency of accommodation associated with the aging of the eye that results in progressively worsening ability to focus clearly on close objects. [4] Also known as age-related farsightedness [5] (or age-related long sight in the UK [6] ), it affects many adults over the age of 40. A common sign of presbyopia is difficulty reading small print which results in having to hold reading material farther away. Other symptoms associated can be headaches and eyestrain. [4] Different people will have different degrees of problems. [1] Other types of refractive errors may exist at the same time as presbyopia. [1] This condition is similar to hypermetropia or far-sightedness which starts in childhood and exhibits similar symptoms of blur in the vision for close objects.

Contents

Presbyopia is a typical part of the aging process. [4] It occurs due to age related changes in the lens (decreased elasticity and increased hardness) and ciliary muscle (decreased strength and ability to move the lens), causing the eye to focus right behind rather than on the retina when looking at close objects. [4] It is a type of refractive error along with nearsightedness, farsightedness, and astigmatism. [4] Diagnosis is by an eye examination. [4]

Presbyopia can be corrected using glasses, contact lenses, multifocal intraocular lenses, or LASIK (PresbyLASIK) surgery. [2] [7] [4] The most common treatment is glass correction using appropriate convex lens. Glasses used to correct presbyopia may be simple reading glasses, bifocals, trifocals, or progressive lenses. [4]

People over 40 are at risk for developing presbyopia and all people become affected to some degree. [1] Around 25% of people (1.8 billion globally) are currently affected. [3]

Signs and symptoms

The first symptoms most people notice are difficulty reading fine print, particularly in low light conditions, eyestrain when reading for long periods, blurring of near objects or temporarily blurred vision when changing the viewing distance. Many extreme presbyopes complain that their arms have become "too short" to hold reading material at a comfortable distance.[ citation needed ]

Presbyopia, like other focal imperfections, becomes less noticeable in bright sunlight when the pupil becomes smaller. [8] As with any lens, increasing the focal ratio of the lens increases depth of field by reducing the level of blur of out-of-focus objects (compare the effect of aperture on depth of field in photography).

The onset of presbyopia varies among those with certain professions and those with miotic pupils. [9] In particular, farmers and homemakers seek correction later, whereas service workers and construction workers seek correction earlier. Scuba divers with interest in underwater photography may notice presbyopic changes while diving before they recognize the symptoms in their normal routines due to the near focus in low light conditions. [10]

Interaction with myopia

People with low near-sightedness can read comfortably without eyeglasses or contact lenses even after age forty, but higher myopes might require two pairs of glasses (one for distance, one for near), bifocal, or progressive lenses. However, their myopia does not disappear and the long-distance visual challenges remain. Myopes considering refractive surgery are advised that surgically correcting their nearsightedness may be a disadvantage after age forty, when the eyes become presbyopic and lose their ability to accommodate or change focus, because they will then need to use glasses for reading. Myopes with low astigmatism find near vision better, though not perfect, without glasses or contact lenses when presbyopia sets in, but the more astigmatism, the poorer the uncorrected near vision.[ citation needed ]

A surgical technique offered is to create a "reading eye" and a "distance vision eye", a technique commonly used in contact lens practice, known as monovision. Monovision can be created with contact lenses, so candidates for this procedure can determine if they are prepared to have their corneas reshaped by surgery to cause this effect permanently.[ citation needed ]

Mechanism

Presbyopia Presbyopia.png
Presbyopia

The cause of presbyopia is lens hardening by decreasing levels of α-crystallin, a process which may be sped up by higher temperatures. [11] It results in a near point greater than 25 cm [12] (or equivalently, less than 4 diopters).

In optics, the closest point at which an object can be brought into focus by the eye is called the eye's near point. A standard near point distance of 25 cm is typically assumed in the design of optical instruments, and in characterizing optical devices such as magnifying glasses.[ citation needed ]

There is some confusion over how the focusing mechanism of the eye works.[ clarification needed ] In the 1977 book, Eye and Brain, [13] for example, the lens is said to be suspended by a membrane, the 'zonula', which holds it under tension. The tension is released, by contraction of the ciliary muscle, to allow the lens to become more round, for close vision. This implies the ciliary muscle, which is outside the zonula, must be circumferential, contracting like a sphincter, to slacken the tension of the zonula pulling outwards on the lens. This is consistent with the fact that our eyes seem to be in the 'relaxed' state when focusing at infinity, and also explains why no amount of effort seems to enable a myopic person to see farther away.[ citation needed ]

The ability to focus on near objects declines throughout life, from an accommodation of about 20 dioptres (ability to focus at 50 mm away) in a child, to 10 dioptres at age 25 (100 mm), and levels off at 0.5 to 1 dioptre at age 60 (ability to focus down to 1–2 m only). The expected, maximum, and minimum amplitudes of accommodation in diopters (D) for a corrected patient of a given age can be estimated using Hofstetter's formulas: expected amplitude (D) = 18.5 − 0.3 × (age in years); maximum amplitude (D) = 25 − 0.4 × (age in years); minimum amplitude (D) = 15 − 0.25 × (age in years). [14]

Diagnosis

A basic eye exam, which includes a refraction assessment and an eye health exam, is used to diagnose presbyopia.

Treatment

In the visual system, images captured by the eye are translated into electric signals that are transmitted to the brain where they are interpreted. As such, in order to overcome presbyopia, two main components of the visual system can be addressed: image capturing by the optical system of the eye and image processing in the brain.

Image capturing in the eye

Solutions for presbyopia have advanced significantly in recent years due to widened availability of optometry care and over-the-counter vision correction options.

Corrective lenses

Corrective lenses provide vision correction over a range as high as +4.0 diopters. People with presbyopia require a convex lens for reading glasses; specialized preparations of convex lenses usually require the services of an optometrist. [15]

Contact lenses can also be used to correct the focusing loss that comes along with presbyopia. Multifocal contact lenses can be used to correct vision for both the near and the far. Some people choose contact lenses to correct one eye for near and one eye for far with a method called monovision.

Surgery

Refractive surgery has been done to create multifocal corneas. [16] PresbyLASIK, a type of multifocal corneal ablation LASIK procedure may be used to correct presbyopia. Results are, however, more variable and some people have a decrease in visual acuity. [17] Concerns with refractive surgeries for presbyopia include people's eyes changing with time. [16] Other side effects of multifocal corneal ablation include postoperative glare, halos, ghost images, and monocular diplopia. [18]

Image processing in the brain

A number of studies have claimed improvements in near visual acuity by the use of training protocols based on perceptual learning and requiring the detection of briefly presented low-contrast Gabor stimuli; study participants with presbyopia were enabled to read smaller font sizes and to increase their reading speed. [19] [20] [21] [22]

Eye drops

Pilocarpine, eye drops that constrict the pupil, has been approved by the FDA for presbyopia. [23] [24] Research on other drugs is in progress. [25] Eye drops intended to restore lens elasticity are also being investigated. [26]

Etymology

The term is from Ancient Greek : πρέσβυς, romanized: presbys, lit.  'old' and ὤψ, ōps, 'sight' ( GEN ὠπός, ōpos). [27] [28]

History

The condition was mentioned as early as the writings of Aristotle in the 4th century BC. [29] Glass lenses first came into use for the problem in the late 13th century. [29]

See also

Related Research Articles

<span class="mw-page-title-main">Corrective lens</span> Type of lens to improve visual perception

A corrective lens is a transmissive optical device that is worn on the eye to improve visual perception. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia. Glasses or "spectacles" are worn on the face a short distance in front of the eye. Contact lenses are worn directly on the surface of the eye. Intraocular lenses are surgically implanted most commonly after cataract removal but can be used for purely refractive purposes.

<span class="mw-page-title-main">Myopia</span> Problem with distance vision

Myopia, also known as near-sightedness and short-sightedness, is an eye disease where light from distant objects focuses in front of, instead of on, the retina. As a result, distant objects appear blurry while close objects appear normal. Other symptoms may include headaches and eye strain. Severe myopia is associated with an increased risk of macular degeneration, retinal detachment, cataracts, and glaucoma.

<span class="mw-page-title-main">Dioptre</span> Unit of measurement of optical power

A dioptre or diopter, symbol dpt, is a unit of measurement with dimension of reciprocal length, equivalent to one reciprocal metre, 1 dpt = 1 m−1. It is normally used to express the optical power of a lens or curved mirror, which is a physical quantity equal to the reciprocal of the focal length, expressed in metres. For example, a 3-dioptre lens brings parallel rays of light to focus at 1⁄3 metre. A flat window has an optical power of zero dioptres, as it does not cause light to converge or diverge. Dioptres are also sometimes used for other reciprocals of distance, particularly radii of curvature and the vergence of optical beams.

<span class="mw-page-title-main">Farsightedness</span> Eye condition in which light is focused behind instead of on the retina

Far-sightedness, also known as long-sightedness, hypermetropia, and hyperopia, is a condition of the eye where distant objects are seen clearly but near objects appear blurred. This blur is due to incoming light being focused behind, instead of on, the retina due to insufficient accommodation by the lens. Minor hypermetropia in young patients is usually corrected by their accommodation, without any defects in vision. But, due to this accommodative effort for distant vision, people may complain of eye strain during prolonged reading. If the hypermetropia is high, there will be defective vision for both distance and near. People may also experience accommodative dysfunction, binocular dysfunction, amblyopia, and strabismus. Newborns are almost invariably hypermetropic, but it gradually decreases as the newborn gets older.

<span class="mw-page-title-main">LASIK</span> Corrective ophthalmological surgery

LASIK or Lasik, commonly referred to as laser eye surgery or laser vision correction, is a type of refractive surgery for the correction of myopia, hyperopia, and astigmatism. LASIK surgery is performed by an ophthalmologist who uses a femtosecond laser or a microkeratome to create a corneal flap to expose the corneal stroma and then an excimer laser to reshape the corneal stroma in order to improve visual acuity.

<span class="mw-page-title-main">Photorefractive keratectomy</span> Refractive eye surgery procedure

Photorefractive keratectomy (PRK) and laser-assisted sub-epithelial keratectomy (LASEK) are laser eye surgery procedures intended to correct a person's vision, reducing dependency on glasses or contact lenses. LASEK and PRK permanently change the shape of the anterior central cornea using an excimer laser to ablate a small amount of tissue from the corneal stroma at the front of the eye, just under the corneal epithelium. The outer layer of the cornea is removed prior to the ablation.

<span class="mw-page-title-main">Radial keratotomy</span> Refractive surgical procedure to correct myopia (nearsightedness

Radial keratotomy (RK) is a refractive surgical procedure to correct myopia (nearsightedness). It was developed in 1974 by Svyatoslav Fyodorov, a Russian ophthalmologist. It has been largely supplanted by newer, more accurate operations, such as photorefractive keratectomy, LASIK, Epi-LASIK and the phakic intraocular lens.

<span class="mw-page-title-main">Refractive surgery</span> Surgery to treat common vision disorders

Refractive surgery is an optional eye surgery used to improve the refractive state of the eye and decrease or eliminate dependency on glasses or contact lenses. This can include various methods of surgical remodeling of the cornea (keratomileusis), lens implantation or lens replacement. The most common methods today use excimer lasers to reshape the curvature of the cornea. Refractive eye surgeries are used to treat common vision disorders such as myopia, hyperopia, presbyopia and astigmatism.

<span class="mw-page-title-main">Intraocular lens</span> Lens implanted in the eye to treat cataracts or myopia

An intraocular lens (IOL) is a lens implanted in the eye usually as part of a treatment for cataracts or for correcting other vision problems such as short sightedness and long sightedness; a form of refractive surgery. If the natural lens is left in the eye, the IOL is known as phakic, otherwise it is a pseudophakic lens. Both kinds of IOLs are designed to provide the same light-focusing function as the natural crystalline lens. This can be an alternative to LASIK, but LASIK is not an alternative to an IOL for treatment of cataracts.

Anisometropia is a condition in which a person's eyes have substantially differing refractive power. Generally, a difference in power of one diopter (1D) is the threshold for diagnosis of the condition. Patients may have up to 3D of anisometropia before the condition becomes clinically significant due to headache, eye strain, double vision or photophobia.

<span class="mw-page-title-main">Refractive error</span> Problem with focusing light accurately on the retina due to the shape of the eye

Refractive error is a problem with focusing light accurately on the retina due to the shape of the eye and/or cornea. The most common types of refractive error are near-sightedness, far-sightedness, astigmatism, and presbyopia. Near-sightedness results in far away objects being blurry, far-sightedness and presbyopia result in close objects being blurry, and astigmatism causes objects to appear stretched out or blurry. Other symptoms may include double vision, headaches, and eye strain.

<span class="mw-page-title-main">Phakic intraocular lens</span> Lens implanted in eye in addition to the natural lens

A phakic intraocular lens (PIOL) is an intraocular lens that is implanted surgically into the eye to correct refractive errors without removing the natural lens. Intraocular lenses that are implanted into eyes after the eye's natural lens has been removed during cataract surgery are known as pseudophakic.

Aniseikonia is an ocular condition where there is a significant difference in the perceived size of images. It can occur as an overall difference between the two eyes, or as a difference in a particular meridian. If the ocular image size in both eyes are equal, the condition is known as iseikonia.

<span class="mw-page-title-main">Emmetropia</span> State of vision

Emmetropia is the state of vision in which a faraway object at infinity is in sharp focus with the ciliary muscle in a relaxed state. That condition of the normal eye is achieved when the refractive power of the cornea and eye lens and the axial length of the eye balance out, which focuses rays exactly on the retina, resulting in perfectly sharp distance vision. A human eye in a state of emmetropia requires no corrective lenses for distance; the vision scores well on a visual acuity test.

Adjustable focus eyeglasses are eyeglasses with an adjustable focal length. They compensate for refractive errors by providing variable focusing, allowing users to adjust them for desired distance or prescription, or both.

Vision of humans and other organisms depends on several organs such as the lens of the eye, and any vision correcting devices, which use optics to focus the image.

Laser blended vision is a laser eye treatment which is used to treat presbyopia or other age-related eye conditions. It can be used to help people that simply need reading glasses, and also those who have started to need bifocal or varifocal spectacle correction due to ageing changes in the eye. It can be used for people who are also short-sighted (myopia) or long-sighted (hyperopia) and who also may have astigmatism.

Multifocal and accommodating intraocular lenses are artificial intraocular lenses (IOLs) that are designed to provide focus of both distance and near objects, in contrast to monofocal intraocular lenses which only have one focal point and correct distance vision. The issue of restoring accommodation following cataract surgery or through refractive lens exchange is becoming an increasingly important topic in ophthalmology.

A corneal inlay is a device which is surgically implanted in the cornea of the eye as a treatment for presbyopia. Successful installation results in reducing dependence on reading glasses, so that the user can more easily engage in everyday tasks such as using a mobile phone, reading store shelf prices and working on a computer.

Clear lens extraction, also known as refractive lensectomy, custom lens replacement or refractive lens exchange is a surgical procedure in which clear lens of the human eye is removed. Unlike cataract surgery, where cloudy lens is removed to treat cataract, clear lens extraction is done to surgically correct refractive errors such as high myopia. It can also be done in hyperopic or presbyopic patients who wish to have a multifocal IOL implanted to avoid wearing glasses. It is also used as a treatment for diseases such as angle closure glaucoma.

References

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  22. ↑ Sterkin A, Levy Y, Pokroy R, Lev M, Levian L, Doron R, Yehezkel O, Fried M, Frenkel-Nir Y, Gordon B, Polat U (2018). "Vision improvement in pilots with presbyopia following perceptual learning". Vision Research. 152 (152): 61–73. doi: 10.1016/j.visres.2017.09.003 . PMID   29154795. S2CID   20260936.
  23. ↑ Moyer, Melinda Wenner (14 December 2021). "New Eye Drops Offer an Alternative to Reading Glasses". The New York Times. ISSN   0362-4331 . Retrieved 15 December 2021.
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  29. 1 2 Wade, Nicholas J.; Wade, Nicholas (2000). A Natural History of Vision. MIT Press. p. 50. ISBN   9780262731294. Archived from the original on 8 September 2017.
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