The Cathedral Eye Clinic

If you are not a good candidate for Lasik / Lasek surgery due to the cornea being too thin or refractive error too high we can offer you the option of phakic IOLs.

Phakic IOLs are lenses that are surgically implanted in the eye. These implants, which resemble contact lenses, are placed between the clear front covering of the eye (the cornea) and the iris (this space is called the anterior chamber) or just behind the iris (the posterior chamber).

There are two types of anterior chamber phakic IOLs: Iris Fixated or angle fixated. The iris fixated IOL is attached to the iris while the angle fixated IOL is held in position within the anterior chamber angle.

The Posterior chamber phakic IOLs sit in close proximity to the natural lens behind the iris.

Several factors dictate whether phakic IOLs can be used:

There must be sufficient physical space within the eye to safely place the lens in the relevant chamber. This is measured preoperatively.

It is also important to carefully assess the level and health of the cells on the back of the cornea using a special type of microscope. These cells (called endothelial cells) are delicate cells required to keep the cornea clear and healthy. If these cells are not sufficiently numerous or they are not appropriately shaped then phakic IOL’s should not be used.

When you choose to undergo any surgical procedure, it is important for you to understand the potential risks as well as the benefits of the treatment so that you are able to make an informed decision as to whether to proceed.

IOL Types

The Monofocal IOLs

Monofocal IOLs have one single focus, this means that near object may not be completely focused without the possible need for reading spectacles. To enable a person to see over a greater range without the need for glasses or contact lenses there are several other types of intraocular lenses.

The Multifocal IOL

Multifocal IOLs work by having various fixed areas of focus within the one lens. This means that a person can choose to concentrate on either a distant object or a near object. The brain has to learn to select the visual information it needs to make an image for either near or distant objects. This means that multifocal IOLs do require some adjustment. A person may adjust better to multifocal IOLs if they are placed in both eyes. These types of intraocular contact lenses work in a similar way to multifocal glasses.

The Accommodating IOL

Accommodating IOLs work by using the natural focusing mechanism of the eye. There are various designs but they all tend to work on the principal that as a person tries to focus on a near object the ciliary muscle in the eye contracts and causes the accommodating IOL to either shift forwards or change shape allowing the eye to change its focus.

What is keratoconus?

Keratoconus is a non-inflammatory, progressive disorder of the cornea. The cornea is the transparent front surface of the eye that provides most of the eyes optical power. Together with the lens, the cornea refracts light, and as a result helps the eye to focus. With keratoconus, the cornea becomes thinner and irregular in shape. The diseased area bulges outwards causing an increase in myopia (short-sightedness) and astigmatism (abnormal corneal curvature) leading to poor vision. Symptoms include blurred vision, distortion, glare and possibly double vision. Frequent changes in spectacle prescription may be noticed. Keratoconus usually starts around puberty with a slow progression; however the rate of progression varies between patients. It usually affects both eyes but one eye may be affected more than the other.

How is it diagnosed?

Most cases of keratoconus are detected during an eye examination. There are visible signs in the cornea and these can be seen with a slit-lamp (a type of microscope). A scan of the eye with a corneal topographer (a device that measures the curvature of the cornea) is often used in the diagnosis of the disease and to monitor the disease progression.

How many people are affected?

Keratoconus is a rare condition. The number of patients affected varies between 1 in 3,000 and 1 in 10,000 depending on geographic location.

What causes keratoconus?

The cause is unknown. However keratoconus has both systemic and ocular associations. Some of the systemic associations include Downs, Turner, Ehlers-Danlos and Marfan syndromes, atopy, osteogenesis imperfecta and mitral valve prolapse. Ocular associations include vernal keratoconjunctivitis, blue sclera, aniridia, ectopia lentis, Leber congenital amaurosis and retinitis pigmentosa.

What are the treatments available?

• Spectacles and soft contact lenses:
  At the very early stages of the condition, spectacles or soft contact lenses may correct the induced myopia and astigmatism. However small changes in the disease will have a dramatic effect on your spectacle prescription.
• Rigid contact lenses:
  As the condition progresses and the cornea continues to thin and change shape, rigid contact lenses can be used to correct the vision more adequately. These contact lenses must be carefully fitted and require frequent checkups. Lens changes may be required to maintain good vision. Unfortunately contact lenses do not stop nor slow the progression of the disease.
• Corneal collagen cross linking with riboflavin (C3-R®):
  The cornea is made of collagen (connective tissue) and in keratoconus the anchors between collagen fibres are weak. This treatment strengthens the collagen structure in the cornea preventing the cornea from bulging out. The treatment is relatively non-invasive and involves application of a custom-made riboflavin eye drop and then exposure of the eye to UV light. The result is increased cross linking of the collagen fibres in the cornea.
• Intrastromal corneal rings (Intacs™):
  Intacs prescription inserts are particularly useful for patients who are contact lens intolerant or to defer the need for corneal graft/transplant surgery. It is a good surgical option as it has a lower rate of complications compared with corneal transplant surgery. The corneal implants are flexible, crescent-shaped rings that are made of PMMA (polymethylmethacrylate). Placement around the periphery (sides) of the cornea causes gentle re-shaping and flattening of the central cornea. The surgical procedure is usually preformed under local anaesthesia but this depends on the patient. There are various implants available with a range of thicknesses for different degrees of correction. An incision is made in the cornea with a special probe or a laser to create a channel and the plastic implants are then inserted into the channels. Some patients may require contact lenses following this surgery; however the tolerance to the lenses should be better. The implants can be removed or exchanged if necessary without affecting the central cornea. The Intacs cannot be felt, are no more visible than a contact lens and require no maintenance. Based on the results of a large scale European study, Intacs received regulatory approval (CE Mark) for use in the treatment of keratoconus. They are supported by more than ten years of clinical studies and have received NICE approval in the UK and FDA approval in the US.
  C3-R treatments can be combined with Intacs to flatten the cornea more so than with Intacs alone. The C3-R treatment aims to stabilize keratoconus from progression and the Intacs reverse the keratoconus steepening that has already occurred.
• Keratoplasty:
  In approximately 10%-20% of keratoconus patients the cornea may become extremely steep, thin and irregular and the vision cannot be improved sufficiently with the above techniques. In these severe cases, a corneal transplant may be required. This is a surgical procedure that replaces the diseased cornea with healthy donor tissue. Where previously keratoplasty was carried out as a full thickness corneal transplant, where possible the endothelial surface is retained and only the anterior (front) surface of the cornea is replaced as a lamellar or deep lamellar graft. Visual recovery after a full thickness transplant takes a long time and complications such as rejection can occur. Lamellar grafts have quicker visual recovery times but with either operation there is a significant possibility that the eye may still need to be fitted with a contact lens.

For more information regarding keratoconus:

UK Keratoconus Self Help and Support Group
The National Keratoconus Foundation
The Keratoconus Center

References:

Mencucci, R., Mazzotta, C., Rossi, F., Ponchietti, C., Pini, R., Baiocchi, S., Caporossi, A. and Menchini, U., 2007. Riboflavin and ultraviolet A collagen crosslinking: in vivo thermographic analysis of the corneal surface. Journal of Cataract & Refractive Surgery, 33 (6), 1005-8. Wollensak, G., Aurich, H., Pham, D.T. and Wirbelauer, C., 2007. Hydration behavior of porcine cornea crosslinked with riboflavin and ultraviolet A. Journal of Cataract & Refractive Surgery, 33 (3), 516-21. Kymionis, G. and Portaliou, D., 2007. Corneal crosslinking with riboflavin and UVA for the treatment of keratoconus. Journal of Cataract & Refractive Surgery, 33 (7), 1143-4. Colin, J., 2006. European clinical evaluation: use of Intacs for the treatment of keratoconus. Journal of Cataract & Refractive Surgery, 32, 747-755. Hustler, A., Manna, A., Morris, S., Obi, A. and Horgan, S., 2007. Intacs for the correction of keratoconus.Journal of Cataract and Refractive Surgery, 33 (8),1354. Rabinowitz, Y.S., 2007. Intacs for keratoconus. Current Opinion in Ophthalmology, 18 (4), 279-283. Kymionis, G.D., Siganos, C.S., Tsiklis, N.S., Anastasakis, A., Yoo, S.H., Pallikaris, A.I., Astyrakakis, N. and Pallikaris, I.G., 2007 Long-term Follow-up of Intacs in Keratoconus. American Journal of Ophthalmology, 143 (2) 236-244. Mohammadpour, M., 2007. Penetrating Keratoplasty for Keratoconus. Ophthalmology, 114 (10) 1952. Paula Grigorian A., 2007. Extended long-term outcomes of penetrating keratoplasty for keratoconus. Evidence-Based Ophthalmology,8 (1) 12-13. Watson SL, Ramsay A, Dart JK, Bunce C, Craig E. Comparison of deep lamellar keratoplasty and penetrating keratoplasty in patients with keratoconus. Ophthalmology. 2004 Sep;111(9):1676-82.

Dry Eyes are one of the most common ocular surface problems seen by ophthalmologists today with over 4 million people in the UK estimated to suffer from this condition.

It occurs when an individual does not produce enough tears or the composition of the tears is abnormal and cannot adequately cover the surface of the eye. The tear film is an essential part for ensuring the overall health of the ocular surface. It cleanses, lubricates, and nourishes the surface of the eye as well as protecting it against infection. Both the quality and quantity of the tears must be maintained within certain levels to ensure a healthy and clear refractive surface essential for good vision.

Symptoms

There are many symptoms associated with dry eye, the most common being:

• Grittiness or Sandy Feeling in the eyes
• Burning or Stinging sensation
• Itching and Scratchiness
• Soreness or Painful
• Foreign body sensation
• A feeling of Dryness
• Sensitivity to light

There are many different causes of dry eye. Some of the most common causes are shown here.

• Adverse Environmental Conditions : Air conditioning, low humidity in aeroplanes, central heating, car heaters, windy weather and smoky environments can all cause tears to evaporate more quickly resulting in a feeling of irritated eyes.
• Contact Lenses, Watching TV and looking at a Computer Screen for long periods of time can all result in a decrease in your rate of blinking which adversely affects your tearfilm.
• Hormones: Many women find that they experience dry eye symptoms on reaching the menopause.
• Medications such as anti-depressants and anti-histamines
• Age :The incidence of dry eye increases with age due to the natural aging process.
• Blepharitis – Bacteria and inflammation of the lids can restrict the proper functioning of the meibomian glands that are involved in producing lipids essential for a healthy tear film.
• Sjögren’s Syndrome :This is an autoimmune disorder that affects the lacrimal gland that is responsible for normal tear production.
• Other causes of dry eye include chronic allergies and conditions such as rheumatoid arthritis and lupus.

Diagnosis

The criterion for the accurate diagnosis of Dry Eye can be complicated and is often controversial amongst clinicians and researchers. This is because there is a wide variety of ocular surface assessments and clinical diagnostic tests currently available some of which do not always correlate with patient symptoms.

Some of the most common tests are:

• Dry Eye Questionnaire :this helps the ophthalmologist to assess patient symptoms and correlate them with signs of tear film disorders. Free online dry eye questionnaire to find out immediately if you may have dry eye.
• Physical Examination :The ophthalmologist will perform an assessment of the whole surface of the eye looking for signs of inflammation and meibomian gland disorders, which are often connected to tear film abnormalities.
• Phenol Red Thread Test :A small thread which changes colour from yellow to red when wet is placed into the lower conjunctival sac for 15 seconds to measure tear volume.
• Schirmer Test :this is a simple test to measure tear production and is performed by placing a filter paper strip over lower eyelid for 5 minutes. The amount of tears absorbed into the paper in this time indicates whether there are enough or too little tears being produced.
• Assessment of Tear Film Stability :Evaluation of the stability of the tear film is considered to be one of the most useful tools for the diagnosis of dry eye since an unstable and unrefreshed tear film is one of the most indicative signs of the presence of dry eye. The measurement of tear stability can be carried out by measuring the time in seconds between one complete blink and the first appearance of a discontinuity or dry spot in the fluorescein stained tear film. Many ophthalmologists consider the assessment of tear film stability by use of fluorescein to be the most important clinical diagnostic test available today.
• Impression cytology to look at goblet cell numbers in the conjunctiva: The ophthalmologist takes a small sample of cells from the surface of the eye using a small piece of specialised filter paper. These cells that are collected on the paper can stained so the number of goblet cells can be counted. People with only a small number or even none of these cells usually have Dry Eye.

Treatments

Management of dry eye is usually a combination of treatments and lifestyle changes that are tailored to the needs of an individual patient. Professor Moore believes that there are two main goals when addressing the treatment of his dry eye patients. “My primary aim is to alleviate symptomatic discomfort and then secondary to prevent or reverse complications and further ocular surface damage that may cause a deterioration of their vision.”

• Artificial Tears :“While many find rapid relief using artificial tears, often this reprieve short-lived with the patient having to use them up to eight to ten times per day,” explains Dr Moore. Indeed some artificial tears contain preservatives that may in fact exacerbate the problem and therefore it is often recommended that non-preservative tear supplements should be the first choice.
• Warm Compresses: Some patients’ symptoms can be alleviated by applying warm moist compresses to the skin of closed eyelids which allows easier release of lipids from the meibomian glands.
• Surgery : blocking of the tear duct with a permanent or semi-permanent plug (usually silicone, collagen or plastic) often helps those with severe dry eye by preventing the drainage of the tears.