Month: May 2018

This blog on Intraocular lenses (IOLs) was authored by Dr. Salman Waqar, Consultant Ophthalmologist in Cataract and Glaucoma Surgery.

IOLs (intraocular lenses) are implanted into a patient’s eye during surgery to remove cataracts. During the  ‘refractive lens exchange’ procedure, the surgeon replaces the natural lens with these medical devices.
Before the 1980s and the introduction of intraocular lenses, patients who had cataracts removed had to wear very thick eyeglasses or special contact lenses to see after surgery; no medical device was available to implant in the eye to replace the focusing power of the natural lens.
Today, there is a wide variety of premium IOLs to choose from. The most suitable intraocular lens for a patient depends on many factors, including lifestyle and specific visual needs. There are ‘premium’ multifocal intraocular lenses available with advanced features beyond those found in basic single-vision IOLs.
During your preoperative examination and consultation, Dr Sohaib Mustafa can help you choose the best IOL for your needs.

Toric IOLs

The choice of IOLs includes the option of a type of lens called Toric Multifocal IOLs. These premium lenses can also correct a range of vision issues, including near/farsightedness and astigmatism. This is made possible because they contain a range of power across the lens, and the surgeon can align the lens to the patient’s cornea and correct the astigmatism very accurately during surgery.

Multifocal IOLs

Multifocal IOLs are another category of presbyopia-correcting IOLs that can decrease your need for glasses for reading or computer use after cataract surgery.
Like multifocal contact lenses, these premium IOLs have added magnification in different parts of the lens to expand your range of vision so you can see objects clearly at all distances without glasses or contact lenses. Some studies have shown multifocal IOLs tend to provide better near vision than IOLs, but they also are more likely to cause glare or mildly blurred distance vision as a tradeoff.
Dr. Mustafa can help you decide whether you are a good candidate for multifocal IOLs during your preoperative examination and consultation.

Monovision

An alternative to multifocal IOLs for correcting presbyopia is monovision, which is not an IOL.
This is the technique of fully correcting the vision in one eye and intentionally making the other eye mildly nearsighted. In this situation, the fully corrected eye sees distant objects clearly (but glasses are needed to see objects nearby), and the mildly nearsighted eye sees close objects very well without glasses (but distant objects are not so clear). This allows the patient to adapt, and to use the dominant eye for distance and the non-dominant eye for near vision. However, this option does not suit everyone. If it is considered, the patient would need a contact lens trial to simulate this combination of vision correction (although this would not be a perfect trial if there is a cataract) to allow the patient to decide whether it would be tolerable before proceeding with surgery.

This week’s blog on Refractive Errors has been contributed by Dr Osama Giledi, Consultant Ophthalmologist, Specialist in Cataract, Cornea and Refractive Vision Correction Surgery

Refractive Errors

In a normal eye, the light (the image that we see) will focus onto the retina, and the quality of this image depends on the balance between the length of the eye, corneal power and eye lens power; any change in the balance of these three factors will create a refractive error, which needs correcting.

• Myopia (nearsightedness): In an eye with Myopia, the image focuses in front of the retina and the vision is blurred, mainly when viewing objects over distance.
• Hypermetropia / Hyperopia (farsightedness): The image focuses behind the retina and the vision can be blurred, especially for objects close by.
• Astigmatism: Astigmatism occurs when the cornea is shaped more like a rugby ball than a football. If astigmatism is significant, images reaching the retina are stretched and distorted as it does not have one single point of focus and the vision is blurred, both for objects that are near or distant.
• Presbyopia: Experiencing difficulties when reading, especially over the age of 40, is called Presbyopia and this is a completely natural (and unavoidable) phenomenon. It happens because the eye gradually loses its ability to focus on objects that are nearby, as the crystalline lens becomes stiffer. This process starts at around the age of 40-45 and is normally completed by the age of 65.

Figure 1: Eye model showing the cornea (A), the iris and the pupil (B), the crystalline lens (C), the retina (D). The most common refractive errors such as myopia (M) and hypermetropia (H) are shown compared to the normal (emmetropic) eye (E) where the images form exactly on the retina.

Refractive Surgery

Most refractive errors can be corrected (or at least improved) by Refractive Surgery. This is a generic term, which comprises both Laser Refractive Surgery on the Cornea, correction by implanted lenses inside the eye called Phakic intraocular lens (IOL) surgery, or the replacement of the natural lens (either a clear lens or one with cataract ) with an intraocular implant – usually a multifocal implant to improve distance , intermediate and near vision.

Laser Refractive Surgery

We can change the shape of the cornea to correct the refractive error. In a case of myopia, the surgeon uses the laser to remove a circle of central corneal tissue to flatten the cornea, which then focuses the image onto the retina.
When the myopia is very high or when the cornea is too thin, laser may not be considered a safe option because the tissue removed may result in a weaker cornea (and a risk of developing keratoconus). In these cases, Phakic IOL surgery is a very good alternative treatment, provided that your eyes are suitable.
To treat hypermetropia, the surgeon uses the laser to change the shape of the central cornea to increase the focusing power of the eye.
To treat astigmatism, the laser removes tissue in an elliptical pattern transforming a rugby ball shaped cornea to a round football shape.

Types of Laser Refractive Surgery:

Laser refractive surgery can be divided into two broad categories: LASIK and SURFACE ABLATIONS.
In LASIK, a flap is lifted and the main laser reshaping is carried out under the flap whereas in SURFACE ABLATIONS, the reshaping is done directly on the corneal surface.
In LASIK, the vision recovers quickly and typically you should be able to resume your work and drive within 1-2 days. There may also be a mild discomfort lasting only for a few hours after surgery.
In SURFACE ABLATIONS, the epithelium (the outermost layer of the cornea which regenerates spontaneously every few days) is removed using different techniques (PRK, LASEK, Epi-LASIK, Trans-PRK). This is like creating a scratch on the eye surface but in a controlled manner. Then the laser excimer (exactly the same laser used for LASIK) reshapes the stroma, the underlying layer.
Surface ablations are initially more uncomfortable for the first two days compared to LASIK, and there is also a slower visual recovery which can take about five days but this procedure is ideal for patients with thin corneas or dry eyes and in those patients whose occupation or hobbies make it more dangerous to create a flap.
We use the latest method called Trans-PRK in which the epithelium is entirely removed by the laser and the eye is not touched by the surgeon. Trans-PRK tends to have a shorter recovery time and less discomfort than other surface laser methods (PRK, LASEK, Epi-LASIK).

Phakic Intraocular Lens (IOL) Surgery

Phakic lOLs are designed for people with high degrees of myopia that cannot be safely corrected by laser refractive surgery. These ‘Implantable contact lenses’ called Visian ICLs are implanted inside the eye in front of the crystalline lens and behind the iris. It is a very effective, safe and reliable procedure for suitable candidates.

This week’s blog on Advanced Diabetic Retinopathy has been contributed by Dr Ammar Safar, Medical Director, Consultant Ophthalmologist and Vitreoretinal Surgeon.

Advanced Diabetic Retinopathy

The effects of uncontrolled diabetes (through diet or medications) on the eye can be devastating in several ways.

The most severe effect is on the Retina, a sensitive membrane that lines the inside of the eye and creates the images that we see. In this blog, I will address some of the common and important questions people have about the impact of advanced diabetes on the eye, also known as Advanced Diabetic Retinopathy:

Can diabetes make me go completely blind?

Yes. Neglected and uncontrolled diabetes can lead to the complete loss of vision through one of three mechanisms:

• Bleeding inside the eye, which becomes completely filled with blood instead of clear liquid.
• The build-up of scar tissue on the retina, which then pulls on the retina and causes it to separate from the wall of the eye, a condition called Traction Retinal Detachment.
• Complete collapse of the normal retinal blood vessels, which leads to the death of the cells that generate the vision due to a lack of oxygen and nutrients (Retinal ischemia).

A combination of the three mechanisms is possible but the last mechanism is relatively rare.

Can vision loss due to advanced diabetes be treated?

Fortunately, yes! The advances in this area of medicine over the past decade or so have resulted in remarkable breakthroughs. In our (Moorfields?) experience, over 92% of the acute vision loss caused by the effects of the complications of advanced diabetes on the retina can now be reversed and vision can be restored.

A surgical procedure called ‘Pars Plana Vitrectomy’ can be performed to stop the bleeding in the eye and remove any possible scar tissue that can be pulling the retina. This allows restoration of vision. The procedure is performed under local anesthesia with no stiches and no need for an overnight hospital stay. New medical treatments are currently being investigated that would reverse the collapse of retinal vessels and hopefully prevent any retinal cell death.

My blood sugar level is well controlled but I am still having retinal problems. Why?

Diabetes is a very malicious disease. For years and sometimes decades, there may be no symptoms at all. Most people discover they have type 2 diabetes during a routine blood test and a regular health check up, without any complaints about symptoms.

Unfortunately, if the blood sugar level is uncontrolled over several years, damage is slowly taking place all over the body including the retina of the eye. The problems and complications appear after several years of poor control and it is at this point that most people realize they need to take this disease very seriously. At this stage, controlling the sugar is crucial to stopping the damage but unfortunately control does not result in immediate effects on the vision. Rather, good control of blood sugar levels pays off after a few years of consistent management and compliance with treatment.

The best approach to dealing with the retinal complications of diabetes is to avoid them completely by performing routine yearly eye check-ups and adhering to a strict diet and medical regimen, but the reality is that we react to how we feel. We are very fortunate to live in an era where even severe vision loss caused by the complications of diabetes can be reversed and functional vision can be restored.

Figure 1:
a: Patient with diabetic bleeding causing severe vision loss.
b: Same patient after surgical treatment with blood evacuated and vision restored.