Corneal inlay

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A corneal inlay (also called an intracorneal implant) [1] is a device which is surgically implanted in the cornea of the eye as a treatment for presbyopia. [2] 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.

Contents

Corneal inlays are small, thin, and permeable. Typically one is implanted in the non-dominant eye.

Jose Barraquer created the first corneal inlay prototype in 1949 in Barcelona, Spain. The flint glass material which he used, however, was found to be unsuitable because of biocompatibility issues. [3] Other transparent, permeable materials were tested, including hydrogel polymers in the 1960s. [3]

Some early corneal inlay recipients experienced complications, such as corneal opacification, thinning and melting. Researchers soon found that, as well as the material, the thickness of the inlay and the depth at which it was implanted were important, as well as permeability and centration. There was a delay in the general introduction of the treatment while considerable research was done to find safe and reliable combinations of these factors. [1]

The US FDA approved the KAMRA corneal inlay in April 2015. [4] The inlays are in commercial use in US, some countries in Europe, Asia-Pacific, the Americas and the Middle East. [5] The inlays are implanted into the cornea either in a laser-created corneal pocket or lamellar corneal flap (similar to LASIK). [6] [7] The inlays can be removed should the patient develop another condition requiring medical treatment. [3]

Types

By 2020, there are five corneal inlays in use and under development:

KAMRA

The KAMRAinlay (AcuFocus, Inc.) is a biocompatible ring that increases the visual depth of field using the physical principle of a small aperture. This design only allows focused light to enter the eye resulting in an improvement in near and intermediate vision while maintaining distance vision. [3] [8] The KAMRA is the first small aperture corneal inlay approved by the US FDA. [4]

FlexivueMicrolens

The FlexivueMicrolens (PresbiaCoöperatief U.A.) is a refractive hydrophilic polymer lens. The central zone of the lens is free of refractive power and the peripheral zone has a standard positive refractive power. This inlay works on a similar principle to bifocal glasses. The bifocal design provides two images to the retina simultaneously. Each specific point of focus is delivered as both a sharp and a blurred image. The FlexivueMicrolens is available in a variety of powers, and can be exchanged as presbyopia progresses. [9]

Raindrop

The Raindrop Near Vision Inlay, formerly known as the PresbyLens or Vue+ lens (ReVision Optics, Inc) is a thin transparent biocompatible hydrogel implant. It is 2 mm in diameter and varies in thickness from 10 microns in the periphery to ~30 microns in the center. It is implanted under a femtosecond laser flap onto the stromal bed of the cornea, centered over a light-constricted pupil. The Raindrop Near Vision Inlay reshapes the central region of the cornea to provide a zone of increased power for focusing on near objects. [9]

Icolens

The Icolens System (Neoptics AG) is another refractive hydrophilic polymer lens, similar to the Flexivue Microlens, with no power in the center and the peripheral zone has positive refractive power. This inlay is also available in assorted powers, which may be exchanged as required due to the progression of presbyopia. [10] [11]

Diffractive Corneal Inlay

The Diffractive Corneal Inlay is a novel type of corneal implant for the treatment of presbyopia, which based on the diffraction phenomena. [12] It was developed by de Diffractive Optics Group (DiOG, Spain) and its working principle combines the pinhole and photon sieve effects. Using diffraction, the inlay is able to generate a diffractive focus in near vision. There are several scientific studies that compare the optical properties of Diffractive Corneal Inlay with the Kamra Inlay, demonstrating that the former obtains a better performance in near vision. [13] [14] [15] [16]

Related Research Articles

<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">Keratoconus</span> Medical condition involving the eye

Keratoconus (KC) is a disorder of the eye that results in progressive thinning of the cornea. This may result in blurry vision, double vision, nearsightedness, irregular astigmatism, and light sensitivity leading to poor quality-of-life. Usually both eyes are affected. In more severe cases a scarring or a circle may be seen within the cornea.

<span class="mw-page-title-main">Cornea</span> Transparent front layer of the eye

The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is approximately 43 dioptres. The cornea can be reshaped by surgical procedures such as LASIK.

<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 an actual cure for astigmatism, since it is in the cornea. LASIK surgery is performed by an ophthalmologist who uses a laser or microkeratome to reshape the eye's cornea in order to improve visual acuity.

<span class="mw-page-title-main">Presbyopia</span> Medical condition associated with aging of the eye

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. Also known as age-related farsightedness, 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. Different people will have different degrees of problems. Other types of refractive errors may exist at the same time as presbyopia. 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.

<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 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.

<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">Orthokeratology</span> Corrective contact lenses

Orthokeratology, also referred to as Night lenses, Ortho-K, OK, Overnight Vision Correction, Corneal Refractive Therapy (CRT), Accelerated Orthokeretology, Cornea Corrective Contacts, Eccentricity Zero Molding, and Gentle Vision Shaping System (GVSS), is the use of gas-permeable contact lenses that temporarily reshape the cornea to reduce refractive errors such as myopia, hyperopia, and astigmatism.

<span class="mw-page-title-main">Astigmatism</span> Type of eye defect

Astigmatism is a type of refractive error due to rotational asymmetry in the eye's refractive power. This results in distorted or blurred vision at any distance. Other symptoms can include eyestrain, headaches, and trouble driving at night. Astigmatism often occurs at birth and can change or develop later in life. If it occurs in early life and is left untreated, it may result in amblyopia.

Ioannis G. Pallikaris is a Greek ophthalmologist who in 1989 performed the first LASIK procedure on a human eye. Pallikaris also developed Epi-LASIK.

<span class="mw-page-title-main">Pellucid marginal degeneration</span> Degenerative corneal condition

Pellucid marginal degeneration (PMD) is a degenerative corneal condition, often confused with keratoconus. It typically presents with painless vision loss affecting both eyes. Rarely, it may cause acute vision loss with severe pain due to perforation of the cornea. It is typically characterized by a clear, bilateral thinning (ectasia) in the inferior and peripheral region of the cornea, although some cases affect only one eye. The cause of the disease remains unclear.

<span class="mw-page-title-main">Gholam A. Peyman</span> Iranian-American ophthalmologist and retina surgeon known for inventing LASIK eye surgery

Gholam A. Peyman is an Iranian American ophthalmologist, retina surgeon, and inventor. He is best known for his invention of LASIK eye surgery, a vision correction procedure designed to allow people to see clearly without glasses. He was awarded the first US patent for the procedure in 1989.

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.

Peter S. Hersh is an American ophthalmologist and specialist in LASIK eye surgery, keratoconus, and diseases of the cornea. He co-authored the article in the journal Ophthalmology that presented the results of the study that led to the first approval by the U.S. Food and Drug Administration (FDA) of the excimer laser for the correction of nearsightedness in the United States. Hersh was also medical monitor of the study that led to approval of corneal collagen crosslinking for the treatment of keratoconus.

The eye, like any other optical system, suffers from a number of specific optical aberrations. The optical quality of the eye is limited by optical aberrations, diffraction and scatter. Correction of spherocylindrical refractive errors has been possible for nearly two centuries following Airy's development of methods to measure and correct ocular astigmatism. It has only recently become possible to measure the aberrations of the eye and with the advent of refractive surgery it might be possible to correct certain types of irregular 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.

Clear lens extraction (CLE), also known as refractive lensectomy or refractive lens exchange (RLE) 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

  1. 1 2 Ashok Garg; Jorge L. Alió (2010). Refractive Surgery. Jaypee Brothers Publishers. pp. 330–. ISBN   978-81-8448-777-0.[ permanent dead link ]
  2. ↑ Frank Joseph Goes (1 January 2013). The Eye in History. JP Medical Ltd. pp. 439–. ISBN   978-93-5090-274-5.
  3. 1 2 3 4 Whitman, Jeffrey. "Corneal inlays provide safe, reversible option for presbyopia treatment." Ocular Surgery News U.S. Edition 2012 Aug.
  4. 1 2 "Corneal Inlays: A Surgical Alternative to Reading Glasses". American Academy of Ophthalmology. 2021-03-24.
  5. ↑ "Corneal Inlays - EyeWiki". eyewiki.aao.org.
  6. ↑ Lucio Buratto (2003). Phacoemulsification: Principles and Techniques. SLACK Incorporated. pp. 536–. ISBN   978-1-55642-604-9.
  7. ↑ Ashok Garg; Jorge L. Alió; Eric D. Donnenfeld (2012). Femtosecond Laser: Techniques and Technology. JP Medical Ltd. pp. 40–. ISBN   978-93-5025-876-7.
  8. ↑ Myron Yanoff; Jay S. Duker (13 December 2013). Ophthalmology: Expert Consult: Online and Print. Elsevier Health Sciences. pp. 156–. ISBN   978-1-4557-3984-4.
  9. 1 2 José L. Güell; J. L. Güell (2013). Cataract. Karger Medical and Scientific Publishers. pp. 139–. ISBN   978-3-318-02410-4.
  10. ↑ "Advances in the Surgical Correction of Presbyopia". Medscape (free account needed for access)
  11. ↑ "CRSToday.com> June 2013> Corneal Inlays: Current and Future Designs". bmctoday.net. Archived from the original on 18 July 2013. Retrieved 24 September 2014.
  12. ↑ Furlan, Walter D.; García-Delpech, Salvador; Udaondo, Patricia; Remón, Laura; Ferrando, Vicente; Monsoriu, Juan A. (September 2017). "Diffractive corneal inlay for presbyopia". Journal of Biophotonics. 10 (9): 1110–1114. doi:10.1002/jbio.201600320. PMID   28635120. S2CID   8753610.
  13. ↑ Montagud-Martínez, Diego; Ferrando, Vicente; Monsoriu, Juan A.; Furlan, Walter D. (11 November 2019). "Optical Evaluation of New Designs of Multifocal Diffractive Corneal Inlays". Journal of Ophthalmology. 2019: 1–6. doi: 10.1155/2019/9382467 . PMC   6885268 . PMID   31827914.
  14. ↑ Montagud-Martinez, Diego; Ferrando, Vicente; Machado, Federico; Monsoriu, Juan A.; Furlan, Walter D. (2019). "Imaging Performance of a Diffractive Corneal Inlay for Presbyopia in a Model Eye". IEEE Access. 7: 163933–163938. doi: 10.1109/ACCESS.2019.2949223 . S2CID   208101199.
  15. ↑ Montagud-Martínez, Diego; Ferrando, Vicente; Garcia-Delpech, Salvador; Monsoriu, Juan A.; D. Furlan, Walter (9 September 2020). "Diffractive Corneal Inlays: A New Concept for Correction of Presbyopia". Visual Impairment and Blindness - What We Know and What We Have to Know. doi: 10.5772/intechopen.89265 . ISBN   978-1-83880-257-8.
  16. ↑ Montagud-Martínez, Diego; Ferrando, Vicente; Monsoriu, Juan A.; Furlan, Walter D. (1 May 2020). "Proposal of a new diffractive corneal inlay to improve near vision in a presbyopic eye". Applied Optics. 59 (13): D54–D58. Bibcode:2020ApOpt..59D..54M. doi:10.1364/AO.383581. hdl: 10251/153225 . PMID   32400623. S2CID   212904915.
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