Cataract and Femtosecond Laser Assisted Cataract Surgery

Introduction

What is Cataracts and Cataract Surgery?

Cataracts occur when changes in the lens of the eye cause it to become less transparent. This results in cloudy or misty vision. The lens is the crystalline structure that sits just behind your pupil. When light enters your eye, it passes through the cornea (the transparent layer of tissue at the front of the eye) and the lens, which focuses it on the light-sensitive layer of cells at the back of your eye (the retina). Cataracts sometimes start to develop in a person’s lens as they get older, stopping some of the light from reaching the back of the eye. Over time, cataracts become worse and start to affect vision. Eventually, surgery will be needed to remove and replace the affected lens.

Cataract surgery is performed over 400.000 times annually in the UK and millions of happy patients worldwide and is considered by the WHO as the safest surgical procedure of the mankind. Cataract surgery works by exchanging the misty natural and increasingly dysfunctional lens of the eye for a permanent plastic one that depending on it’s type and optical quality can give some form of spectacle independence or just clear distance vision. The general result is a more natural vision for many years to come.

What types of IOLs exist?

RLE employ a wide array of IOLs depending on the patient requirements: level of prescription, the presence of corneal scars, previous eye surgery, pupil size, age of patient, occupation, lifestyle, presence of medical condition like Diabetes, Glaucoma, Macular degeneration etc. Some of the common IOL types are listed below.

• Monofocal: A monofocal lens uses a high precision optic to focus all light passing through the pupil to one focal point, this can be either near or distance or in between depending on Px requirements. (Tecnis ZA, ZCB, Sensar AR40e)
• Multifocal (bifocal, trifocal, sectoral, refractive, diffractive): To be a good candidate you need to already have a significant visual handicap and be a positive person seeing a glass half full as opposed to half empty and do not suffer from diabetes, macular pathologies or states like anxiety, depression, OCD or bipolar. These lenses can be viewed in lay terms as light splitters that some light does the distance and the rest does the near and/or intermediate vision. So, a weak MF lens vs intermediate vs strong lens would split the light to 80-20% vs 75-25% vs 55-45% for distance and near vision respectively. This is the only lens type that induces many images simultaneously and requires a significant brain adaptation that more than 90% of the general population can manage, especially the younger patients. Examples: Tecnis Symfony, ZLB, ZKB, SBL-3, PhysIOL, Zeiss trifocal, Lentis M+ or Mx
• Accommodating:  This is the only lens type that tries to utilise the function of the eye as a focusing apparatus. On principle this is a monofocal lens that has the ability due to it’s design to move a bit inside the eye thus improving the depth of focus however, such movement is not sufficient for full spectacle independence and may wean over time. It will require yag laser well before other lens types. Examples: Tetraflex HD (by Lenstec)
• Toric IOL This incorporates a special correction for astigmatism at the top of what is needed for good focus for distance. It can be used on both monofocal and multifocal lenses but not on accommodating lenses
• Monovision or Blended vision: This is not a lens but a method of using monofocal lenses to increase depth of focus.  Around 50% of the general population can tolerate a moderate imbalance of focus between the two eyes (Rx imbalance of -1.50D) when one eye doing near vision and the other distance and almost 95% can tolerate a relative imbalance with a mini-monovision (Rx imbalance of -0.75). This results in some imbalance and impaired 3D perception but improves functional spectacle independence in a natural way without the introduction of many aberration and glare and can easily be enhanced for better near or distance by the use of special spectacles.
• Piggy-bag IOL (Sulcoflex): This is a plane simple monofocal or multifocal lens like a contact lens very thin and elastic used to correct refractive surprise or to introduce mutlifocality after an otherwise successful cataract RLE surgery or a monofocal lens.
• Aphakic (Artisan): This is an Iris haptic IOL (iris claw) very much like the p-IOLs however much thicker and placed behind the pupil. It is used exclusively for Px that had a complicated cataract surgery

Am i a Good Candidate for Cataract Surgery?

If you are experiencing increasingly blurry vision, increased glare at nigh, changing eyeglasses every year or even glasses cannot help you see clearly for the majority of your activities then yes you could be. The procedure is generally safe for all eye types though patients with denser, white cataracts or higher prescriptions should take precaution.

How it Works to Get Younger Vision?

IOLs through a cataract surgery refresh and rejuvenate the vision by removing an ageing dysfunctional lens and replacing it with a clear more optically perfect lens thus turning back the clock. The majority of over 70s feel that their vision is like it was on their 40s.

How many Treatments will You Need?

Usually one but if you have a refractive surprise (5-10%) then you will likely need an enhancement with wither LVC or piggybag lens. It is likely (5% per year) that you will need yag laser posterior capsulotomy to clear the skin that contains the lens, this will not need to be repeated, it is minimally invasive and you can return back to work a few hours later. Additionally, if you had a multifocal lens and failed to adapt to its’ side-effects (0.5%) then you may need to exchange your IOL to a weaker multifocal lens or to a monofocal.