Cataract Surgery

What is a cataract ?

The eye lens, consisting of fibers, can not only become less elastic with age (presbyopia) but also cloudy. A similar effect of “nuclear sclerosis” also occurs in cases with pets. Cataract disease is a kind of clouding of the vitreous body (the lens of the eye). In that case the cataract surgery is recommended.

The word cataract has been translated from Latin as a waterfall since ancient Roman times as the clouding of the lens was represented like the white foam of a waterfall 1. Although some cataracts can be congenital, caused by trauma, smoking, diseases (such as diabetes), and oxidizing drugs, age-related cataracts are considered the main ones 2. It is believed that cataracts cannot be avoided otherwise by eating and living the right way. Cataract disease may occur sooner or later. It’s just a matter of time.

The lens of the eye also acts as UV filter protecting the retina from its damage. Nutrients pass through the fibers of the lens and thus, the lens acts as an oxygen scavenger with a high concentration of antioxidants. Induced oxidative damage can accompany corneal opacity 2.

If the cataract is not “treated” (replaced eye lens) then the person can become permanently blind. The main cataract complications are increased eye pressure or glaucoma, inflammation of the choroid, but it can be seen at the initial level with the help of modern diagnostic equipment.


How is cataract surgery and lens replacement performed ?

For a long time over the centuries, the surgeon pushed an opaque lens into the vitreous cavity with a needle, thus clearing the way for the propagation of light in the eyeball. At the very least, such a method could restore hope to blind cataract patients with completely clouded lenses. Since more than 20 diopters of optical power are concentrated in the lens of the eye, appropriate glasses were required after such an operation.

Since the eighteenth century the development of implantation of artificial lenses for cataract disease (replacement of the lens) began. During World War II, it was observed1 that damage to the eyes of pilots by some materials resulted in minimal intraocular irritation. So attention was paid to this material but this did not help to avoid postoperative inflammation. Another problem was the dislocation of the lens in the eye lens capsule. There was still work to be done to improve the centering of the artificial lens when calculating the optical power of the IntraOcular Lens (IOL).

Depending on which part of the eye lens capsule becomes cloudy, that part is operated on (capsulotomy):

a) capsulotomy for cataract of the lens nucleus,

b) treatment of cataracts with clouding of the outer shell of the capsule,

c) capsulotomy of the clouded posterior lens shell.

In the first case the symptoms may be a deterioration in the clarity of vision at a distance and near. In others, it may be visual impairment in illuminated spaces.

Cataract Surgery IOL

Fig. 1. Schematic representation of the position of the IOL in the eyeball is indicated in yellow. Antennae are needed for a stable position in the capsule of the eye

FemtoSecond Laser and Phacoemulsification

The introduction of the femtosecond laser to the ophthalmic market has made it easier for surgeons to perform cataract surgery. With the help of the laser the accuracy and safety of the corneal incisions necessary for the removal of the lens, as well as for its fragmentation (fragmentation), were improved.

The native lens of the eye can also be fragmentized with an ultrasonic tip and sucked out (aspiration process) through the desired incision in the eye – phacoemulsification.

Such technologies have helped to avoid a long stay of patients in the hospital after cataract surgery.

Advantages of IOL implantation over laser correction for presbyopia

One of the biggest advantages of IOL implantation is that it can be removed if the IOL does not compensate for lost vision. The IOL can be removed from the eye and a new one put in without changing the thickness of the cornea, as would be required when correcting laser vision for presbyopia.

Future prospects of IOLs

It is known that IOL lenses can be of three types depending on the calculations and properties of the cornea (multifocal, monofocal and toric). An ideal IOL would be an accommodative IOL that could contract like the natural lens of the eye.

Attention! If you have more recent information, we will be happy to accept it. If you have any questions, put it on the forum ( or ask directly by email



  1. Krueger RR, Talamo JH, Lindstrom RL. Textbook of Refractive Laser Assisted Cataract Surgery (ReLACS). (Krueger, Ronald R. Talamo, Jonathan,H. Lindstrom RL, ed.). Springer New York Heidelberg Dordrecht London; 2013. doi:10.1007/978-1-4614-1010-2
  2. Moshirfar M, Milner D, Patel BC. Cataract Surgery. In: Treasure Island (FL); 2022.

Corneal Implants for presbyopia, corneal segments and rings

In addition to laser vision correction and intraocular lens replacement, there are also various types of corneal implants and implantable collamer (also contact) lenses (ICL) 1 2 3.

What are corneal implants?

Methods where synthetic materials (implants) are inserted into the cornea to reshape it encompass IntraCorneal Lenses (ICL for presbyopia also known as inlays), Rings (ICR) and Ring Segments (ICRS) 4. Unlike Implantable Collamer (Contact) Lenses, also abbreviated as ICL, and Intraocular Lenses (IOL), which are implanted behind the cornea or in the back chamber of the eye, respectively, the implants are inserted into the incision made in the cornea. In case of refractive error between +4 diopters and -8 diopters Implantable Contact Lenses can be used, while the IOL is preferred for cataract. The Implantable collameral (contact) lenses (ICL) have advantages for the correction of myopia and myopic astigmatism due to their predictability, stable refraction, and high efficiency. Studies have shown a low incidence of unwanted symptoms 5. In the case of presbyopia, intracorneal rings or lenses may be used. In case of keratoconus corneal segments can be used for therapeutic purposes  2.

Types of corneal implants

For the treatment of presbyopia rings and lenses are implanted into the cornea.

The meaning of the corneal ring is that it improves near vision in the non-dominant eye, but retains distance vision with two eyes 6. That is such a ring restricts the flow of light into the eye and is a kind of a narrow pupil.

Presbyopic intracorneal lenses change the curvature of the cornea in the middle, but not change it in the periphery. This creates a multi-vocal effect similar to Presby-LASIK (see Presby-LASIK).

Other intracorneal lenses may have a hole in the middle for distance vision surrounded by a neutral optical zone and refractive power at the periphery of the lens for near vision 6.

Benefits of corneal implants

The main advantage of corneal implants is the reversibility of the operation, i.e. they can always be removed if the effect is unsatisfactory 1 6.

However, central corneal opacity may occur. In turn corneal rings restrict light from entering the eye, which can reduce the contrast and quality of night vision, and may also cause optical side effects.

Studies using intrastromal (stroma – the main part of the cornea) segments (ICRS) in keratoconus to correct astigmatism have shown improvement in visual acuity and refraction of the eyes in the first three years 2.

Attention! If you have more recent information, we will be happy to accept it. If you have any questions, put it on the forum ( or ask directly by email


  1. Alio JL. Management of Complications in Refractive Surgery. (Alió JL, Azar DT, eds.). Berlin, Heidelberg: Springer Berlin Heidelberg; 2018. doi:10.1007/978-3-540-37584-5
  2. Min-Ji K, Yong-Soo B, Young-Sik Y, et al. Long-term outcome of intrastromal corneal ring segments in keratoconus: Five-year follow up. Sci Rep. 2019;9(1):1-7.
  3. Higginbotham J. Correcting Presbyopia – Modern Options Head of Clinical Affairs What is Presbyopia ? Birmingham Opt. 2016:44.
  4. Shortt AJ ABDS, Evans JR. Laser assisted in situ keratomileusis (LASIK) versus photorefractive keratectomy (PRK) for myopia. Cochrane Database Syst Rev. 2013;(1). doi:10.1002/14651858.CD005135.pub3
  5. Packer M. Meta-analysis and review: effectiveness, safety, and central port design of the intraocular collamer lens. Clin Ophthalmol. 2016;10:1059-1077. doi:10.2147/OPTH.S111620
  6. Arba Mosquera S, Alió JL. Presbyopic correction on the cornea. Eye Vis (London, England). 2014;1:5. doi:10.1186/s40662-014-0005-z