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Cataract is the clouding of the eye's natural lens and it causes by multiple reasons such as aging, diabetes and atopic dermatitis. In cataract surgery, surgeon removes the natural lens in the eye and replace with a plastic and artificial lens which lasts semipermanently, requires no care, and be able to improve vision significantly. Also cataract surgery is one the most frequently performed surgical procedures in the world. It usually only takes around an hour per eye. Recently more and more intraocular lenses are introducing to the world, and which allow you to see distance and near vision as well. EDOF is one of the lens that uses in the surgery.  

Description of EDOF lens and its development

EDOF lens is one of the multifocal intraocular lens and it stands for “Extended depth of focus Intraocular lens”. EDOF technique fixes the problems that conventional lenses have and make possible to simplify and miniaturize the design of those lenses.

The reasons of EDOF lenses developed was due to the huge increased use of computers and smartphones. Therefore, the development of compact optical zoom lenses for unification in mobile devices in the aim of many companies. EDOF lenses cannot focus on all three distances(cloth, mid, and far) perfectly like tri focus lens, however, it is possible to focul more than two distances and prevents glare and halos symptoms at the same time.

Mono focus lens vs. multi focus lens

Mono-focus lens is a lens which specialized in focusing on the specific distance and it is usually either near vision( 45cm from your eyes) or distance (more 500cm from your eyes). It means that it is useful for a person who wants to watch something specific really clearly. For example, a person who loves knitted work or reads books all day. However, it is inconvenient for most of them because even though they get surgery, they might need to wear glasses to see other distances. Nevertheless the vision of specific distance is more clear than the vision of same distance with multi focus lens. Also there is no possibility of having glare and halos symptoms, which some people who got surgery with multi focus lens might experience. In addition, mono focus lens is recommended to people with weak lens capsule, which is the things cover the eye’s natural lens, because the multi focus lens sometimes tears lens capsule when they get surgery if it is weak. On the other hands, multi focus lens makes them possible to see all the distance without the glasses. But some people experience glare (blur) or halos (dassing) around bright lights, especially when driving at night. Although multi focus lens has a tendency of experiencing visual disturbances at night, it is useful for most of them daytime.

EDOF lens vs. other multi focus lens

There are various of multi focus lenses and more new lenses are coming. Some of them are bi focus and the others are tri focus whereas EDOF lens is in between these two. For example, on one hands, “FINE VISION” from PhysIOL has the strongest power to focus on all distances. And Tecnis Multifocal from AMO is more focus on the eyes to hand distance. However those lenses have a problems with using during night time. Miniwell ready from SIFI MedTech, which is one of the EDOF lens makes possible to have zero nighttime troubles. Therefore, EDOF lens is the only one lens which makes possible to avoid any glare and halos issues. Also it is possible to focus on cloth/mid distance to far distance.

Usage in cataract surgery

The eye’s natural lens is covered by lens capsule, so surgeon cuts the capsule, opens, and take out the natural lens. The IOL is placed in the lens capsule that was left in the eye.

There are two types of cataract surgeries: Small incision cataract surgery and extracapsular surgery

• Small incision cataract surgery:

This surgery makes an incision in the side of the cornea, the clear thing which cover the eye, and inserts a little probe into the eye. And the probe produces the ultrasound waves which soften and break the lens into tiny pieces, which makes it possible to suction out. It is called “phacoemulsification”.

• Extracapsular surgery:

It requires wider incision in the cornea to remove the lens core in one piece. This surgery is for people whose cataract has advanced to the point where  phacoemulsification cannot be used to break up the clouded lens.

The difference between two surgeries is the size of the incision; small incision cataract surgery does not require to use sutures to close the opening whereas the other one requires.

Different types EDOF lenses (weaknesses and strengths)

There are few EDOF lense in the world. Each lens has features.

-Miniwell ready  (SIFI MedTech) : It is only one lens which has no glare and halos symptoms.

-TECNIS Symfony OptiBlue (AMO) : It is skilled in focusing at mid and far distance, but it is not good at cloth distance, so it is not useful for people

-Lentis (Oculentis) : It is possible to custom own lenses. Therefore, it prevents misfitting of frequency of intraocular lens.

-Acriva Trinova（VSY Biotechnology) : This lens is skilful at focusing on eyes to hands distance, so the vision of cloth distance is more clear than others.

Side effects of cataracts surgery

-inflammation or infection of the eye

-bleeding in the eye

-swelling of the cornea

-detachment of the retina

-increased pressure inside the eye

-dislocation of the implanted lens

-accumulation of fluid in the retina

-drooping eyelid

However, the potential of having those risks are higher for people who have other eye diseases or other medical problems.  

Also, cataracts might mask additional eye issues, such as retinal damage, and those problem is difficult to be found before surgery, soin these case, the success of the cataract surgery will depend on the treatment of the other problems.

References

American Optometric Association. (2019). Cataract Surgery. Retrieved from

https://www.aoa.org/patients-and-public/eye-and-vision-problems/glossary-of-eye-and-vision-

conditions/cataract/cataract-surgery

Clin O. (2017) ”Comparison of visual outcomes after bilateral implantation of a diffractive trifocal intraocular lens and blended

implantation of an extended depth of focus intraocular lens with a diffractive bifocal intraocular lens”. National

	Institutes of Health. doi: 10.2147/OPTH.S145945

Jeffrey M. (2019) "Extended Depth of Focus IOLs”.AMERICAN ACADEMY OF OPHTHALMOLOGY.

https://eyewiki.aao.org/Extended_Depth_of_Focus_IOLs

Mads D. (2012) "Development of compact optical zoom lenses with extended-depth-of-field", Proc. SPIE 8488, Zoom

Lenses IV, 84880C ; doi: 10.1117/12.927860; https://doi.org/10.1117/12.927860

Mary. A., Gerd U., Florian K., Tamer T., Tanja M., Mike P.,and Ramin. (2017). “Clinical Evaluation of an

Extended Depth of Focus Intraocular Lens With the Salzburg Reading Desk”. International Vision

	Correction Research Centre. doi:10.3928/1081597X-20170621-08

Liu, Z., (2007) "Diffractive lens with extended depth of focus and its applications" (2007). Dissertations from 　

ProQuest. 2581. https://scholarlyrepository.miami.edu/dissertations/2581