Keratoconus is a chronic condition that affects the cornea; the transparent, dome like tissue located at the front of the eye. Keratoconus is characterised by progressive thinning and protrusion of the cornea. As a result, the cornea increases in curvature, protruding and taking up an irregular, conical shape (like a traffic cone), as opposed to a regular, spherical shape (like a soccer ball) leading to reduced vision.
Keratoconus is relatively common in New Zealand, estimated to occur in between 1/500 and 1/1000 of the general population. The condition usually develops in the early teenage years, followed by the disease getting progressively worse until age 30-40. The symptoms of keratoconus are non-specific; most patients simply experience blurry or fuzzy vision. In the earliest stages of keratoconus there may be no or minimal symptoms at all; fortunately, a specialised imaging device called a corneal topographer, which maps the shape of the cornea, is used by the optometrists at Mortimer Hirst to detect keratoconus in these early stages.
In the early stages of keratoconus, when the shape of the cornea is relatively normal, spectacles or soft contact lenses provide adequate vision; however, as the disease progresses and the corneal shape becomes more irregular, rigid (hard) therapeutic contact lenses are required to adequately compensate for the abnormal shape of the cornea. With proper care, regular replacement of the lenses as they degrade and regular eye exams to ensure the contact lenses do not compromise the health of your eyes, well-fitting contact lenses can provide lifelong visual rehabilitation for keratoconus.
All the members of the clinical team at Mortimer Hirst are highly experienced in fitting and maintaining the specialty contact lenses required for keratoconus. As you may have read on our home page; in 1943 Gene Hirst accepted, with great success, a challenge made by an Auckland ophthalmologist to manufacture the first contact lenses in New Zealand for a keratoconic patient. You can read more about the fascinating history of contact lens manufacturing at Mortimer Hirst on our about us page. The technology used to fit and manufacture contact lenses has changed substantially since 1943, but one thing that has not changed is Mortimer Hirst’s commitment to being at the forefront of the developments in the assessment and management of keratoconus, using the latest technology and research to provide you with the best possible eye care. These commitments from the clinical team include post-graduate study and research into keratoconus.
The Mortimer Hirst clinical team are optometrists and contact lens specialists; they are involved in teaching contact lens fitting for keratoconus in the Bachelor of Optometry programme at the University of Auckland. Dr Aki Gokul completed his PhD in keratoconus in 2016, a large portion of which involved a study conducted through Mortimer Hirst. Dr Gokul continues to be actively involved in research into keratoconus and its management with contact lenses and surgery at a Post-Doctoral level, through Mortimer Hirst, the University of Auckland and the Auckland District Health Board. Dr Gokul lectures globally on ground breaking research into keratoconus and its management, including the use of the latest contact lens technology and is regarded as one of New Zealand’s leading keratoconic experts.
The clinical team at Mortimer Hirst can diagnose keratoconus, assess its severity and determine if it is progressing using the latest technology, and based on this, formulate a customised treatment plan that will provide visual rehabilitation so that keratoconus does not prevent you from doing the things you want to do.
Early detection of keratoconus is vital as if the condition is allowed to progress unchecked, the corneal shape can become too irregular for contact lenses to be worn safely and comfortably and corneal scarring can limit vision (often to the level of legal blindness). In these cases, transplantation of a human donor cornea is necessary and this occurs in about 20% of cases. Fortunately, a recently developed, relatively simple surgical procedure called corneal collagen cross-linking has been shown to stop or slow down disease progression and dramatically reduce the risk that a corneal transplantation is required. The clinical team at Mortimer Hirst work closely with eye specialists in the public and private sector that perform corneal collagen cross-linking and corneal transplantation, so you can be assured that surgical options will be explored if required.
A variety of different contact lens technologies can be used to provide visual rehabilitation for keratoconus. Below is a brief description of the different types of contact lenses commonly utilized but it is best to discuss the ideal option for you with your optometrist. The Ministry of Health provides a contact lens subsidy for those with keratoconus and the clinical team at Mortimer Hirst will apply for this subsidy on your behalf if you are eligible.
Soft Contact Lenses
Soft contact lenses are the simplest and often most comfortable contact lens option. However, being “soft” means that they take up the same shape as the cornea so these lenses are generally only an option when keratoconus is in the mild/moderate stages. Newer, specialized soft contact lens options may provide visual rehabilitation for more advanced keratoconus.
Corneal Rigid Gas Permeable Contact Lenses
Corneal rigid (hard) contact lenses are the most common form of contact lens used to provide visual rehabilitation in keratoconus. Being rigid in nature means that these lenses maintain their shape on the cornea so they mask the unusual shape of the cornea, meaning the eye operates essentially like a “normal” eye with the lenses in place. Rigid lenses are often a little uncomfortable to start out but most patients adapt to them in a week or so.
Hybrid Contact Lenses
Hybrid contact lenses are composed of a combination of a rigid center and a soft skirt, thus hybrid contact lenses are intended to provide comfort similar to a soft contact lens but vision similar to a corneal rigid gas permeable lens. Hybrid contact lenses are an option when corneal rigid gas permeable lenses are too uncomfortable to wear.
Semi-Scleral and scleral Contact Lenses
When keratoconus reaches the more severe stages, soft, corneal rigid or hybrid contact lenses often do not work well as all of these lenses sit on the cornea and as the corneal shape is too distorted, these lenses do not fit well and either do not provide good vision, are uncomfortable or do not stay on the eye. When this is the case, the cornea is vaulted entirely by a larger rigid contact lens known as a semi-scleral or scleral contact lens, depending on its size. Semi-scleral and scleral contact lenses arch over the cornea and sit on the conjunctiva (the white part of your eye), this way the distorted corneal shape is masked, providing good vision as with other rigid lenses, and since they do not touch the cornea, they are very comfortable.
Corneal Collagen Cross-Linking
Corneal collagen cross-linking is a relatively simple surgical procedure that involves removing the protective layer of the cornea, soaking the cornea in riboflavin (Vitamin B2) then exposing the cornea to ultraviolet light. Corneal collagen cross-linking acts to strengthen the collagen of the cornea, which is responsible for giving the cornea its shape, thus the strengthened collagen prevents disease progression and essentially “freezes” the cornea in its current shape.
Corneal transplantation is a major operation; it is similar to a heart or kidney transplant. The cornea from someone who has passed away is removed from their eye and part of the cornea is transplanted to your eye. Once a corneal transplant has completely healed, its shape is generally more regular but it is often still not quite the “right” shape for your eye so spectacles or contact lenses may still be required to achieve the best vision following a transplant.