Newsletter Summer 2013

Dear patients and friends,

I promised I would talk about cataract surgery in this newsletter, simply because patients with cataract are probably the most common cause for referral to an Ophthalmologist. From a vitreoretinal perspective, I often have to consider combining vitrectomy surgery with phacoemulsification cataract surgery because the incidence of cataract following vitrectomy is very high.

On a personal side, we had a busy summer this year as a result of a new arrival at home. Our son Raphael was born on the 11^th of July, but to my surprise, I am still getting some sleep! As usual, if you have any specific requests, please let me know. I do hope you continue to enjoy the newsletters and I look forwards to hearing from you.

Hadi Zambarakji MB ChB, FRCOphth, D.M
info@retinacare.org.uk
Spire Roding Hospital, Roding Lane South, Ilford. IG4 5PZ.

Femtosecond laser cataract surgery

Modern phaco cataract surgery is performed through a 1.6-2.8 mm corneal incision. The surgery involves several steps, which ultimately aims to removal of the cataract, and the placement of a lens implant into the capsular bag. In order to get access to the lens, a capsulotomy (also called capsulorhexis) is performed.

However, several steps of the phaco cataract procedure could be performed with the femtosecond laser. The femtolaser is therefore a pulsed laser system (pulses are delivered at a quadrillionth of a second) that can be used as an adjunct to cataract surgery through photo-disruption. The steps which can be done with the femtolaser include the capsulotomy, the nucleus fragmentation and the corneal incision (tunnel). The main advantages of the femtolaser are the repeatability of the capsulorhexis shape and size, and the reduction in phaco power therefore reducing the risk to the corneal endothelium (this is the monolayer of cells that lines the inner surface of the cornea). The importance of a regular and well-centered capsulorhexis include lens centration, refractive outcome (the ability to achieve good unaided visual acuity). Some would argue that the true advantages of femtolaser are minimal, whilst others agree that the femtolaser is another step in the refinement process of the cataract procedure. Whilst there are less than a handful of femtolasers in the UK at present, I am personally looking forward to the use of the Topcon LENSAR, which will become available at the Wellington Hospital in the very near future.

Would the patient be expected to notice a difference? It is difficult to know what to expect as a patient, unless each eye was done using a different technique (femtolaser vs. standard phaco). I think it is important to note that despite the theoretical advantages of the femtolaser, surgical outcomes are dependent on a multitude of factors. There are however, reports comparing initial experience with the femtolaser with standard phacoemulsification cataract surgery in the hands of experienced surgeons some of which show a higher incidence of complications with the femtolaser. Overall, the true benefits will most certainly not be as significant as the move from extracapsular cataract surgery (large incision) to phacoemulsification surgery some 25 years ago, but the move to using the femtolaser for cataract is a likely step that many phaco surgeons will be making during the next 5 years. For some patients however, where patient factors may make surgery more complex, femtolaser will probably not be an option. I personally feel that some surgeon will not take up the femtolaser step, to avoid the learning curve and possibly because results are pretty good already.

Lens implants and micro-monovision

Lens implants are inserted in the eye to achieve a specific refractive correction and we often aim for emmetropia, that is to achieve good unaided distance vision. For some patients, emmetropia is not an ideal solution because of the desire to have spectacle independence. For some patients, in particular those who have always used one eye for distance and one for near, we can keep the same refractive error difference at the time of cataract surgery by correcting one eye for distance (emmetropia) and one for near (myopia). However, only very few patients are good candidates for this sort of correction, also called monovision, because we leave a 2.5-3 dioptre difference between the 2 eyes. Most patients however, unless having previously had monovision, would probably not tolerate as much as 3 dioptres difference between the 2 eyes. A smaller difference in refractive outcomes is however easily tolerated (usually of about 0.75D) with the non-dominant eye for near and the dominant eye for distance. The non-dominant eye would therefore end up slightly myopic after surgery in order to achieve some degree of unaided near vision, at the expense of slightly reduced unaided distance vision. The binocular vision however would be driven by the dominant eye and would therefore be good for distance (assuming there are no other ocular factors that may contribute to reduced vision). A contact lens trial is usually but not always needed to confirm the patient will tolerate the difference. I would always let the patient know that he/she would still need reading spectacles if wishing to read small print for long periods of time. Other options to achieve unaided distance and near vision include multifocal lens implants and accommodative lens implants but the benefits and disadvantages of these implants could be discussed in another newsletter.

Phacovitrectomy

Vitrectomy is usually necessary when treating a retinal detachment, macular hole, epiretinal membrane or other forms of vitreoretinal disease that necessitates the need to remove the vitreous body. The incidence of cataract after vitrectomy is high. This is true in particular for patients over the age of 50 years and when intravitreal gas or oil are used at the time of vitrectomy. Thus the incidence of cataract or progression of pre-existing lens opacities at two years can be as high as 100% following vitrectomy for macular holes where intravitreal gas is always used to help close the macular hole. Bearing this in mind, I am very keen to propose combined phacovitrectomy when a patient has a pre-existing cataract (even if mild) as cataract progression would result in worsening of vision over the following 2-3 years and the need for a subsequent surgical procedure. One interesting offshoot of not performing phaco cataract surgery at the time of vitrecotmy is the development of index myopia as a result of mild nuclear cataract, and therefore the “index myopic eye” which had vitrectomy is then able to achieve some degree of near vision without spectacle correction thus giving the patient some degree of spectacle independence.

I will always be guided by my patients’ needs and every patient will be different. This newsletter is for you so please let me know if you would like me to address a specific topic. I would like to hear from you, and read your suggestions and feedback.

Hadi Zambarakji

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