Irregular corneas include a wide range of corneal shapes and conditions that usually affect a patient’s vision adversely. A few microns of irregularity in the corneal surface can have severe effects on the quality of vision, with serious consequences for the quality of life of the person affected.¹
Keratoconus is a corneal condition that can have this type of detrimental impact. It is a degenerative disease that occurs when the central part of the cornea becomes thinner and tends to curve outwards, giving it an irregular, conical shape. The resulting curvature alters the refractive power of the cornea, and ultimately the patient’s vision. It is the most common primary ectasia (corneal thinning).²
The potential negative impact on patients was something that was recognized by Paul Rose, an optometrist from Hamilton, New Zealand, over 30 years ago. He was concerned about what could be done for patients with keratoconus and decided to take up the challenge of correcting irregular cornea in 1987.
Understanding that the problem with traditional contact lenses was that they did not fit unusual corneal shapes or mimic the shape of the eye well, Paul Rose began developing the ROSE K keratoconus lens. He wanted this contact lens to be more comfortable for patients, easier to fit, and provide better vision for those suffering from this condition. After testing 700 lenses and 12 different designs, he produced an initial set of 26 lenses from which all keratoconus patients could be fitted.
Since then, advances in technology have led to the introduction of other ROSE K lens designs to address a wider spectrum of irregular corneas.³
But let’s take a closer look at keratoconus and discover the strengths of the ROSE K family of lenses, which has now become the most frequently prescribed brand of lenses for irregular corneas in the world.
Irregular cornea and keratoconus
Keratoconus is a progressive, bilateral corneal ectatic disorder characterized by steepening of the cornea associated with irregular stromal thinning, resulting in a cone-like bulge (protrusion) and significant loss of vision.
The incidence of keratoconus is estimated to be between 1 to 5 persons per 1,000 in the general population.⁴
Although the exact etiology of keratoconus is still unknown, we know the disease is multifactorial and can be influenced by genetic, environmental, and biochemical factors. People with a genetic predisposition to keratoconus tend to also be affected by environmental factors.⁵
The onset of symptoms can be during adolescence and young adulthood, and it may manifest as reduced vision, corneal astigmatism, increasing higher-order aberrations, and fluctuating vision. There is severe vision reduction in the advanced stages of the disease due to high myopia, irregular astigmatism and corneal scarring. In 12-20% of cases, the disease may lead to corneal transplantation.⁶
The treatment for irregular cornea and keratoconus
The available options for the management of keratoconus are highly dependent on the stage of the disease and its stage of progression.
If the disease is progressing, the main focus should be on slowing or stopping (arresting) the progression so the cornea is stable and does not get worse. Corneal collagen cross-linking (CXL) is a minimally invasive outpatient procedure that leads to an increase in stromal rigidity and it is the procedure of choice to slow and stabilize keratoconus that is progressing. A corneal transplant is considered the last option when the cornea is too thin to receive CXL, and the symptoms are severe. The cornea is replaced entirely (penetrating keratoplasty) or partially (lamellar keratoplasty) with healthy donor corneal tissue.⁷
If the disease is stabilized (no progression), the emphasis is on correcting and optimizing vision. Providing optimal vision correction for keratoconic patients can be challenging. The corneal shape distortion and associated stromal thinning are highly asymmetric. This makes good vision correction with spectacles and conventional soft contact lenses difficult to achieve and limiting their effective use to only early stages of the disease.
Custom-designed soft contact lenses that incorporate aberration-controlled designs may provide some control of the primary aberrations associated with keratoconus.
Corneal and scleral rigid gas permeable (RGP) contact lenses are the mainstays for vision correction in moderate to advanced keratoconus. Their main advantage is the creation of a tear pool between the lens and the cornea, which naturally neutralizes the ocular aberrations associated with the ectasia, and generally providing excellent corrected vision.
The decision to choose corneal or scleral lenses requires consideration of several different factors. While corneal designs may not be tolerated well by the patient (usually in the first weeks of wear), larger diameter designs (semi-scleral, scleral) can provide better comfort results. On the other hand, handling may be easier with smaller designs for neophyte wearers especially during the first weeks of wear. The stage of the disease can also determine whether to use one design over the other with more advanced keratoconus usually addressed with larger designs.
ROSE K family
ROSE K adheres to the core philosophy that each type of irregular cornea is unique with both its optical (vision) and physiological (corneal health) needs. Thus it is not ideal to fit all types of corneal irregularities with just one design, rather each eye should be treated uniquely. This is why corneal profile analysis plays an essential role in fitting the irregular cornea as it helps define the most suitable lens design to be used for each cornea. For example, a hyper-prolate corneal profile like in keratoconus will be approached differently than a prolate or an oblate profile like in corneal grafts. It is therefore essential to have different designs to optimize the final lens fit which is how the ROSE K family of lenses was designed.
The features that make the ROSE K lens so effective at correcting vision when there are irregularities of the cornea are numerous. First, the complex lens geometry can be customized to fit each eye, providing the patient with clear vision. In addition, the design is highly breathable, helping to keep the eye healthy while correcting vision and providing all day comfort. Finally, these lenses are incredibly easy to insert, wear, remove and maintain.
The ROSE K family of lenses includes several designs: ROSE K2 lenses, ROSE K2 Irregular Cornea (IC) lenses, ROSE K2 Post Graft (PG) lenses for post-surgical cases, ROSE K2 Nipple Cone (NC) lenses, ROSE K2 XL semi-scleral lenses and ROSE K2 Soft. Each of the lenses in the ROSE K2 family includes aberration control aspheric optics, resulting in outstanding visual acuity and reduced flare and glare.
Furthermore, all ROSE K designs follow the same simple, systematic, five-step fitting process to ensure that practitioners can learn to fit all the designs easily:
1.Base Curve Selection
The ROSE K trial set and fitting system has been optimized over the years with an over 80% first-fit success rate achieved in patients fitting internationally.⁸
Keratoconus is a disease of relatively low prevalence that rarely results in blindness. However, because it affects young adults, the magnitude of its public health impact is disproportionate to its prevalence and clinical severity.⁹ Various options are available for the treatment of keratoconus, depending on the stage of the disease. In order to achieve optimum results, it is essential to choose the best option for each patient considering their condition, needs and preferences.
Contact lenses are the mainstay therapy for keratoconus and are the treatment modality of choice in 90% of patients because they can mask the corneal surface irregularity to provide good vision. However, due to irregular corneal topography, achieving an optimal lens fit can be a long and complicated process.
Despite this, contact lens fitting in irregular corneas is a challenge that every practitioner should embrace as it may be the only way to provide these patients with a clearer future in what is a blurred and sometimes hopeless world. The beauty of prescribing specialty contact lenses for irregular corneas is that clinical success comes from the knowledge and skill of the practitioner. Fitting and prescribing contact lenses for irregular corneas is a unique skill within the eyecare profession, it is a process that takes time, but can be very rewarding as it can have a profound impact on patients.
Throughout its 70-year history of challenges, successes, and innovation in the contact lens industry, Menicon has always been at the side of ECPs to offer them high quality, safe products and comprehensive service and training, with the ultimate goal of ensuring good vision for all their patients. Continuous research in the field of keratoconus contact lenses is part of this approach.
Heralded as "a quantum leap forward in the evolution of lens design for the condition"⁸ of keratoconus, ROSE K has become one of the world's most popular and frequently prescribed gas permeable contact lenses for keratoconus. Unlike traditional contact lenses, the complex geometry built into every ROSE K contact lens closely mimics the cone-like shape of the cornea for every stage of the condition. The result is a more comfortable fitting lens for patients and better vision (visual acuity).
The ROSE K family of contact lenses by Menicon: meeting the challenge of the irregular cornea together.
Kymes SM, Walline JJ, Zadnik K, Gordon MO. Quality of life in Keratoconus. Am J Ophthalmol. 2004; 138: 527–535. Romero-Jiménez M, Santodomingo-Rubido J, Wolffsohn JS. Keratoconus: a review. Cont Lens Anterior Eye. 2010;33(4):157-205.https://www.roseklens.com/about/ https://www.roseklens.com/about-keratoconus/what-is-keratoconus/ The Genetic and Environmental Factors for Keratoconus. Ariela Gordon-Shaag, Michel Millodot, Einat Shneor, Yutao Liu Biomed Res Int. 2015; 2015: 795738 Mohammadpour M, Heidari Z, Hashemi H. Updates on managements for Keratoconus. J Curr Ophthalmol. 2018;30(2):110–124. Asimellis G, Kaufman EJ. Keratoconus. StatPearls Publishing; 2021 Jan.2020 Dec 28 https://www.roseklens.com/practitioners/lens-types/ Kymes SM, Walline JJ, Zadnik K, Gordon MO; Collaborative Longitudinal Evaluation of Keratoconus study group. Quality of life in keratoconus. Am J Ophthalmol. 2004 Oct;138(4):527-35.
Francesca Cacciamani, Marketing Professional, Soleko Menicon Group
Francesca Cacciamani has been working as a Marketing Professional in Soleko for 4 years.
She has a scientific background (Biology) and has been dealing with sales and Regulatory Affairs in the optical industry for 11 years.