Keratoconus A Brighter Perspective

The last two decades have heralded significant advances in the management of keratoconus, giving patients improved choices for refractive correction and reducing the need for a penetrating keratoplasty. Increased availability of topographical imaging equipment has improved early diagnosis of mild disease, made monitoring progression easier, and resulted in earlier referrals for collagen cross-linking.

REFRACTIVE MANAGEMENT

Optical correction should always start with a careful refraction. Many patients with moderate and even advanced keratoconus can achieve reasonable vision with a pair of spectacles. Substantial over-minusing and under-correcting of cylinder is a common error.

CASE STUDY ONE: DON’T GIVE UP ON GLASSES

BP came into our clinic to explore contact lens options, as he was not achieving great vision in his new spectacles. His current spectacles measured:

R -4.00, VA 6/60

L -4.00, VA 6/60

Corneal topography confirmed advanced keratoconus in both eyes (Figure 1).

Prior to a contact lens fitting, careful subjective refraction found the following:

R -3.25/-5.00×90 VA 6/12

L -1.50/-4.00×90 VA 6/12

A contact lens fitting into mini keratoconicdesign rigid gas permeable (RGP) contact lenses improved the patient’s vision, giving him visual acuity (VA) of 6/6 in each eye.

BP was relieved to discover that not only could he achieve excellent vision using contact lenses, but that spectacles could also give him adequate acuity to work, function well in his day to day life, and even drive. This is invaluable for any patient requiring a break from contact lens wear.

Discussion 

Auto-refractors are often completely inaccurate, so subjective refraction is best performed using large steps, giving extra response time, and pushing the plus as much as possible.

The VA that spectacles can provide to patients with moderate and advanced keratoconus is often underestimated. Refraction will take up more chair time, but it is a very worthwhile exercise – especially when contact lens wear becomes contraindicated in the case of infection or inflammatory keratitis, an all too common scenario in this patient cohort.

THE LATEST AND GREATEST IN CONTACT LENSES

Contact lens designs for keratoconus continue to improve and evolve, particularly for mini-scleral or scleral contact lenses, which have experienced a resurgence in popularity over the last several years.

Scleral lenses are generally very well tolerated, provide excellent optical correction, and can generally fit on the most irregular of corneas. The use of scleral lenses has been shown to lower the risk of a keratoplasty,¹ and therefore should always be trialled before a patient chooses to undergo surgery.

Designing scleral lenses has become increasingly bespoke with the advent of profilometry or scleral-corneal mapping.

Significant scleral toricity is common, often irregular, and unrelated to corneal toricity (Figure 2). Profilometry allows for a highly customised lens periphery, providing optimal fit and comfort.

The sMap3D device is a profilometer that uses reflection off sodium fluorescein to attain images in three different gaze positions, then merges them together to provide a topography up to 18–20mm and beyond (Figure 3 and 4).

For post-graft patients, a smaller diameter RGP is always preferred to a scleral lens, however they can be extremely challenging to fit.

When a scleral lens must be used, choosing a hyper-Dk material with minimal centre thickness should always be a priority to lower the risk of hypoxia.

MANAGING PROGRESSION – TREAT THE ITCH!

Keratoconus is strongly associated with atopy, and eye rubbing with progression.^2,3 Most patients with keratoconus will not initiate a discussion about their eye rubbing behaviour, so it’s important to always ask whether or not they experience itchy eyes. Therapeutic management with a combination antihistamine/mast cell stabiliser such as non-preserved Zaditen is very effective in most cases, and should be initiated immediately. Regular use of a cool compress, particularly upon contact lens removal, is also extremely effective at relieving itch.

COLLAGEN CROSS-LINKING (CXL)

Over the last decade, corneal collagen cross-linking (CXL) has become a gamechanger for keratoconus management. Since its first introduction in the late 1990s, along with increasing use of scleral contact lenses, CXL has contributed to the reduction in the number of patients requiring a keratoplasty.

Despite a 2015 Cochrane Review⁴ concluding that there is limited evidence to show the efficacy of CXL due to a lack of randomised controlled trials, it has been widely accepted, by ophthalmologists globally, as the mainstream treatment for ectasia progression.⁵ Most studies show CXL halts or reduces progression in the majority of subjects, with a good safety profile. Long term follow-ups have shown sustained stabilisation over seven to 10 years.^6,7

Most surgeons like to see evidence of progression before performing CXL. Topographic and pachymetric monitoring for most patients at high risk of progression (eg, teenagers and young adults, atopic individuals, and pregnant women) should occur at three to six monthly intervals.

With the advance of topographical equipment, keratoconus can be detected in eyes as young as four years old. There are limited studies documenting paediatric CXL outcomes, however it has been shown to be effective,⁸ though perhaps not as effective as in adults. Young children who have advanced disease at the initial presentation, will probably benefit from immediate CXL rather than waiting for documented signs of progression.

Despite the fact that CXL flattens K readings in most patients and can improve visual acuity, it is not a refractive procedure and therefore not indicated when the condition is no longer progressing. Further, with increasing age a “natural crosslinking” occurs within corneal tissue,⁹ and it may, in fact, regress in older patients.

PATIENT EDUCATION REGARDING VISION CORRECTION

Education is critical in this patient cohort, to avoid costly treatment mistakes.

Of patients with keratoconus, 85-90% can have their vision satisfactorily corrected with spectacles or contact lenses.

Many unfortunately, elect surgical treatment options based on the misconception that surgery will always eliminate the need for glasses and/or contact lenses. This is simply not the case. Corneal ring segments are somewhat unpredictable, and good candidates need reasonable corrected acuity to attain the best outcome. They should still expect to achieve their best vision with the aid of spectacles or contact lenses. Keratoplasty – while still a very good treatment option when necessary – can also be unpredictable, is variable over time, and comes with its own unique risks.

CASE STUDY TWO

LH, a 38 year old female with keratoconus, came to the clinic looking to achieve better vision following a corneal graft on her left eye. She was disappointed to learn that given the irregularity of the graft, her only option for improving vision in that eye was a mini scleral contact lens – her decision to have the graft in the first place was to avoid wearing scleral lenses.

Thankfully, with encouragement, she was pleasantly surprised by how comfortable scleral lenses could be. She had worn mini- RGPs for many years and had great lens handling skills, so she had no trouble learning a new insertion and removal technique.

This is a frustrating, and all too common, case where a graft could have been avoided completely, had the patient been informed of the very real possibility she may still require contact lenses following surgery. After coming full circle with regard to vision correction requirements, there is now the added risk of hypoxia and corneal graft failure, which will likely be increased by contact lens wear.

PSYCHOLOGICAL MANAGEMENT

Multiple studies have shown that keratoconus can significantly impair quality of life. This unique eye disease affects people in their teens and early adult years, with patients generally perceiving their visual loss to be much worse than it is. In fact, their visual function and mental health scores are similar to those who have intermediate to advanced macular degeneration in at least one eye.¹⁰ 

These patients need hope. They need to be reminded that keratoconus rarely leads to blindness, that there are multiple options available for vision correction, and the vast majority of patients can achieve good vision without surgery.

The last two decades have seen a surge in research and new techniques; keratoconus is now being diagnosed much earlier and monitored more effectively; CXL slows or halts progression and is now publicly funded; specialty contact lenses are always improving and reducing the number of patients having transplants; surgical techniques and strategies are improving; and research aimed at ‘curing’ or regaining stromal keratocytes is well underway. The future is bright, and with the right management, patients should be aware that keratoconus doesn’t need to affect their quality of life.

CONCLUSION

In summary:

• CXL and scleral contact lenses have been associated with decreasing risk of needing a keratoplasty,
• Aggressively managing any associated allergy is imperative to minimise progression,
• A careful spectacle refraction is important, even in advanced disease, and
• All contact lens options should be explored prior to surgery.

Dr Alex Koutsokeras is a therapeutically-endorsed clinical optometrist with particular expertise in specialty contact lenses and dry eye management. She achieved her Optometry degree with first class honours from the University of Auckland. Prior to this, she completed a Psychology degree from the University of Sydney. Dr Koutsokeras has also completed advanced studies in glaucoma. 

References 

1. Ling JJ, Mian S, Stein JD, et al. Impact of scleral contact lens use on risk of requiring corneal transplantation for keratoconus. ARVO 2019, p. Abstract 4779. 
2. Rahi AH, Davies PD, Ruben M, Lobascher D, and Menon JA. Keratoconus and coexisting atopic disease. 1977, British Journal of Ophthalmology, 61(12), pp. 761-764. 
3. Bawazeer, A. M., Hodge, W. G., & Lorimer, B. Atopy and keratoconus: a multivariate analysis. 2000, British Journal of Ophthalmology, 84(8), pp. 834-836. 
4. Sykakis, Evripidis, Rushmia Karim, Jennifer R. Evans, Catey Bunce, Kwesi N. Amissah-Arthur, Showrob Patwary, Peter J. McDonnell, and Samer Hamada. Corneal collagen cross-linking for treating keratoconus. 2015, Cochrane Database of Systematic Reviews 3. 
5. Corneal collagen crosslinking for corneal ectasias: a review. O’Brart, David PS. 2017, European journal of ophthalmology 27, pp. 253-269. 
6. O’Brart DP, Patel P, Lascaratos G, et al. Corneal crosslinking to halt the progression of keratoconus and corneal ectasia: seven-year follow-up. 2015, American journal of ophthalmology, 160 (6), pp. 1154-1163. 
7. Raiskup F, Theuring A, Pillunat LE, Spoerl E. Corneal collagen cross-linking with riboflavin and ultraviolet-A light in progressive keratoconus: ten-year results. 2015, Journal of Cataract & Refractive Surgery, 41(1), pp. 41–46. 
8. Godefrooij, Daniel A., Nienke Soeters, Saskia M. Imhof, and Robert PL Wisse. Corneal cross-linking for pediatric keratoconus: long-term results. 2016, Cornea, 35(7), pp. 954-958. 
9. Cartwright, Nathaniel E. Knox, John R. Tyrer, and John Marshall. Age-related differences in the elasticity of the human cornea2011, Investigative ophthalmology & visual science, 52(7), pp. 4324-4329. 
10. Sahebjada S, Fenwick EK, Xie J, Snibson GR, Daniell MD, Baird PN. Impact of keratoconus in the better eye and the worse eye on vision-related quality of life. 2014, Investigative ophthalmology & visual science 55 (1), pp. 412-416.