Cataract

Symptoms

Patients with Cataracts can expect common symptoms that include:

• Cloudy or blurry vision.
• Fading of colours
• Glare from light sources (such as headlights, lamps)
• Sunlight may also appear too bright
• Halos may appear around light sources.
• Poor night vision (especially when driving).
• Double vision or multiple images in one eye. (This symptom may clear as the cataract gets larger.)
• Frequent prescription changes in your eyeglasses or contact lenses.

Treatment

Depending on the visual impairment and progression of the patient’s Cataracts, there are a few choices to improve visual acuity.

Prescription Glasses

Patients with cataracts can update their spectacles at the first instance to avoid surgical intervention. Once the cataract progresses, it will impede the distance visual acuity and the law of diminishing return applies with respect to the benefit of further spectacle updates.

Cataract surgery

This procedure is the removal of the cloudy lens along with the insertion of an artificial intra-ocular lens to take its place. There are several different types of procedures to remove the cataract. The most commonly utilized technique is Phacoemulsification with Insertion of an Intra-Ocular Lens.

Related Video: Cataract: Surgery

Phacoemulsification and Intra-ocular Lens implant

The purpose of surgery is to replace the cloudy lens with a clear lens implant inside the eye. Phacoemulsification is the procedure where the cloud lens is removed through a small incision (@2mm) in the cornea. The thin clear membrane (capsule) holding the cataract is left intact to support the new lens implant. A thin ultrasound probe is inserted into the eye that uses ultrasonic vibrations to dissolve the lens. These tiny fragmented pieces are then suctioned out using the same probe. Once the cataract is removed, an artificial lens is placed into the same thin capsular bag that the cataract occupied. This intraocular lens is essential to help your eye focus after surgery.

It is unusual to require a stitch in the eye at the end of the operation because the incision is so small it is nearly always self-sealing. Eyes that have a thin corneal wall ( keratoconus ) tend to be floppy and these do require a stitch to avoid wound sag and degradation of the expected visual outcome.

This procedure requires the use of anaesthetic. Topical anaesthetic drops, such as eye drops and sedation work well. Although eye drop anaesthesia does not numb the eye completely it does provide very effective numbness. Occasional pressure on the eye is all that is likely to be felt at certain points during the operation but sharp pain is very uncommonly reported by most patients. Larger volumes of anaesthetic can be deposited around the eye and can stop the eye moving as well as feeling anything at all ( peribulbar or subtenons )

Lens Selection: What sort of vision do you want after the operation?

Depending on an individual’s needs, there are several different intra-ocular lens options available to suit a various ranges of demands. The information below is a brief insight to options available to a patient. Consultation with a specialist Cataract & Refractive surgeon is always required to ensure the patient is suitable for a specific lens type.

Single distance vision ( SDV ) lens Implants

This utilises a lens with a single focal point, usually set for distance in each eye. It gives good binocular vision over a useful range. If a patient is happy to wear intermediate and reading glasses, then this is the most common option and is usually the only option offered in the public health system.

Monovision

Two different standard lenses (one eye set for distance vision, the other set for intermediate distance vision), then this is a suitable option for those patients who may have had prior experience of it in spectacles or contact lenses. It breaks down stereopsis (3D perception) and you will still need reading glasses for fine print. If you have not tried it before then doing so for the first time at cataract surgery is not the wisest choice. In my practice I reserve this for those who have had experience of this naturally or in contact lenses, for most others tolerance is untested and cataract surgery is not the best place to first try it.

Micro-monovision

One eye is set for distance the other for an intermediate focus point. This is well tolerated as still provides some stereopsis (3D perception) useful range of vision but you will still need readers for all near tasks and occasionally for visual tasks performed at an intermediate distance. This is another very common choice and if the patient is happy to wear readers, you have very happy patient indeed.

Accommodating lens implants

These are lenses that move when implanted in the eye and try to mimic the body’s own natural lens movements. They aim to give good vision over a range of distances. In reality because they move their resting point in the eye is more unpredictable and more people end up a little more short or long sighted than they bargained for. Also most do not move enough and so you still need reading glasses for near and move too slowly so there is a significant lag time ( speed of accommodation ) when you look from the distance to focus on something up close which can be quite frustrating. Others accommodating lenses move too easily in a bid to obtain more near vision and there are a few anecdotes that with a good sneeze one can apparently be left short sighted unexpectedly.

Multifocal Lens Implants

This lens type has both a distance component and reading component. This work in a similar manner to bi-focal prescription glasses except that in glasses the patient looks from the distance into the near add and thus the whole vision sees only one in focus image. With multifocal lens implants both the distance and the near vision are in focus at the same time. When one looks in the distance there is usually nothing obstructing the view at near. When looking at book for near vision, the book blocks the distance image. Multifocal implants offer patients relative spectacle independence and the same operation is offered as a life style choice to patients without cataract who simply want the greater freedom from wearing glasses. They are often referred to as a premium lenses ( a marketing term ) but they truly are more expensive. A period of adaption is required and the compromise with this lens is often noted at night with ghosting, halos and excess stray scattered light. This is most notable when viewing a point source of light at night (e.g. a car headlight).

Not all multifocal implants are the same. Some of the cheaper versions are based on simple prism technology with concentric rings of distance and near which have been around for 25 years and the technology has not changed significantly in that time in my opinion. These diffractive multifocals produce marked halos and light scatter particularly troublesome when night driving. So much so I refuse to offer this particular type of implant as the adaption phase is typically 6-12 months and a significant percentage of individuals remain dissatisfied and less confident with night driving. It also can have a significant explant rate when advocated to the wrong type of patient.

Personally I prefer the segmental multifocal implants. The adaption phase is 4-8 weeks typically and the impact on night driving confidence is consistently reported as much less. Here the near vision is inferior to the distance segment. The aberrations in the vision happens in the vertical meridian (inferiorly) as opposed to the diffractive multifocal implants that produce the 360 degree multiple ring halo effects.

Extended depth of focus and Extended range of vision implants

Here the discussion on optics ranges to the blending of technologies between diffractive IOLS with their course transition and the segmental IOLs with their slow transition from distance to near. Others describe the effect an oil droplet on the lens. A dog with a different tail is my preference. While EDV is the new black on the marketing scene. Reasonably well tolerated….apart that is with the 7% with significant Halos in the FDA trials make this lens like vegemite. You love or you hate it. A potential explant rate approaching in in ten in not my idea of sleeping well. My perception of its relative unpredictability means it has no place in my practice.

Toric lens implants

Patients with high levels of astigmatism can utilise Toric Lens technology, which is designed to counter-act this refractive disorder. Toric lenses correct distortions in one particular meridian/ axis. They can be found in single distance vision lenses and in multifocal implants. Correcting astigmatism is the second most important optical correction, impacting the quality of the unaided visual outcome after correcting defocus, (how long or short sighted a patient is).