Excellent toric contact lenses are now available to optometry. So why is toric contact lens penetration low when compared against the penetration achieved by astigmatism correcting spectacles? Is it time to bring back the science?
“Optometry wouldn’t exist without astigmatism.” What a grandiose statement, but if you delve deep enough into the history of our profession, it was really on the back of astigmatism that optometry was born.
Let’s go back in time… Hop in the DeLorean with Doc and go back to the 1800s.
Thomas Young was the first person to measure astigmatism in 1801. It took another 24 years before the first sphero-cylindrical spectacle lens was made, its pioneer being George Bidell Airy who corrected his own astigmatism. Upon putting on his sphero-cylindrical spectacle lenses he stated, “I have found that the eye which I once feared would become quite useless can now be used in almost every respect as well as the other.”
Our profession is built upon correcting astigmatism in spectacles, why then are we not as proactive in correcting astigmatism in contact lenses?
Let’s think about this for a moment. Anyone born before 1825 that had astigmatism simply had to mask their astigmatism with spherical spectacles lenses. Even though Airy had made this discovery in 1825, astigmatism wasn’t widely corrected until the late 19th century when techniques developed for its objective measurement.
The first of these discoveries was the ophthalmometer, which we know today as the keratometer. Invented by Herman Von Helmholtz in 1854, the keratometer allowed practitioners the ability to measure the curvature of the corneal surface. Von Helmholtz was a talented fellow, just three years earlier he had revolutionised ophthalmology by inventing the ophthalmoscope, which for the first time in history allowed practitioners to look into a living eye. In 1859 Sir William Bowman realised that the ophthalmoscope could be used to detect astigmatism and in 1880 H. Parent coined the term ‘retinoscopie’ to describe the technique to quantitatively measure the error of refraction with lenses.
The period between 1850 and 1890 was a golden period in ophthalmology and physiological optics; names such as Von Graefe, Snellen and Donders pioneered an optical renaissance. Franz Donders became the father of clinical refraction when, in 1864, he wrote his book The Anomalies of Accommodation and Refraction of the Eye in which he described the theory of optical conditions, the methods to determine their measurement and the employment of prescription lenses to correct them. Up until this point people who required spectacles bought mass-produced ready-made spectacles from pharmacists, jewellers and watchmakers.
There are 48 powers between +6.00 and -6.00 and a person, through trial and error, would select the spectacles, which gave them the best vision. Astigmatism all of a sudden increased the number of those parameters into the thousands and opticians became highly skilled craftsmen, the profession booming to satisfy this unmet clinical need. Anybody could call themselves an optician, which as you can imagine, spawned many charlatans.
Astigmatism found its birth in Europe but it was in the New World that optometry was born. A booming, rapidly spreading population required access to vision care and it was opticians who provided this service. Many opticians began to test patients, and so a division between dispensing and refracting opticians developed.
Have you ever wondered where the term ‘optometry’ originated? It was first mentioned by Edmund Landolt in his 1886 book Refraction and Accommodation of the Eye and their Anomalies, in which he used the word ‘optometry’ to describe refractive procedures. The term optometry gained traction in the USA, quickly followed by Australia and by 1905 refracting opticians were calling themselves optometrists and so, from a need to correct astigmatism, we see the birth of our profession.
Contact lenses follow a more recent timeline starting from Adolf Fick who fitted brown glass haptic lenses in 1887. It wasn’t until Otto Wichterle’s development of soft lenses in 1961 that contact lenses became more widely available. Soft toric lenses reached the market in the mid 70s yet were fraught with problems, excessive rotation and poor reproducibility such that lenses were given the nickname ‘snowflakes’, since no two lenses even of the same prescription were the same. It wasn’t until the advent of cast molding in the 80s and later production technologies such as CIBA Vision’s Lightstream technology in 1997 that soft toric lenses achieved a high level of reproducibility.
In 2016 we have some excellent toric contact lens options which makes it surprising that toric contact lens penetration is falling short. Approximately 45 per cent of the spectacle wearing population has clinically significant astigmatism in at least one eye (≥0.75D) yet only 23 per cent of all new contact lens fits are torics.1
Optometrists are in the business of selling astigmatism
Our profession is built upon correcting astigmatism in spectacles, why then are we not as proactive in correcting astigmatism in contact lenses? I’m sure there is a hangover from the old days and cost is a factor, but have disposables dumbed down astigmatism? Do we need to bring back the science? The following case is an illustration of how we can utilise the tools commonly available to us to better manage our patient’s needs.
Karen is a 34-year-old professional golfer with a simple astigmatic prescription:
R/X R. Plano/-1.25 x 102 (6/6+) L. Plano/-1.50 x 67 (6/4.8).
K’s R. 43.62D @ 122 L. 43.59D @ 49
44.99D @ 32 45.45D @ 139
ΔK=1.38D ΔK=1.86D
This looks like a simple case. Yet if we look a little closer at Karen’s corneal topography, we come to realise that her corneal astigmatism is approximately 20 degrees different to her refractive astigmatism. Oblique cyls can often be more difficult to correct than with-the-rule or against-the-rule astigmatism.
The left plot also has a slightly skewed radial axis and the Surface Asymmetry Index (SAI) demonstrates some corneal irregularity, RE 0.90 LE 1.13. A figure over 1.0 indicates a moderate degree of corneal irregularity. Karen has quite tight upper eyelids and her lateral canthi are a little higher than her nasal canthi, which can impart temporal rotation on a contact lens. It would appear that fitting toric lenses on Karen might not be as easy as first expected. I fitted her with Air Optix for Astigmatism, a lens, which I feel, offers exceptional rotational stability. On inspection the right lens did not rotate at all and the left lens rotated seven to eight degrees (to the left) while looking in the primary position, which can be attributed to her corneal irregularity and skewed radial axis. But our patients don’t always look straight ahead; head rotations and oblique versions can have quite a negative impact upon visual performance.
I held a near point letter chart at a 45-degree angle upon which Karen was forced to rotate her head to read, which caused her acuity to drop from N4 to N5. Measuring the decrease in near acuity in this head position can be a great way of measuring rotational stability. Also, have the patient make versional eye movements in 45-degree angles before returning to the primary position.
Upon 45-degree version movements, the right lens rotated two to three degrees to the left while the left lens rotated up to four degrees further to the left, meaning that the left lens had moved as much as 12 degrees off her refractive axis. Upon returning to primary position, both lenses recovered to their original positions within seconds. I simply employed the LARS rule and increased the left axis to 80 degrees and her left rotational problem was solved.
All contact lens practitioners know that vision correction is only half the battle. Since the first contact lens was ever fitted, comfort has always been the number one issue as evidenced by the following case.
Cathy, a 43-year-old dry eye sufferer, entered my practice interested in trialling contact lenses. She had previously trialled two-weekly lenses but found them intolerable, particularly towards the end of the day.
Cathy’s refraction was:
R/X R. +1.75/-0.25 x 75 (6/4.8) L. +2.75/-1.00 x 85 (6/3.8-) Add: +0.75 (N3)
SAI R. 0.71 L 0.46
Topography revealed mild irregularity, particularly on the right plot, which can be attributed to tear film instability, which was supported by a quick tear film break up time (TFBUT) of approximately five seconds. There was minimal to no sign of fluorescein or lissamine green staining yet the Schirmer scores were mildly reduced (R. 10mm L. 8mm).
On further questioning, Cathy confirmed symptoms of allergic conjunctivitis, namely itchy and watery eyes. Cathy presented a number of challenges; I needed to correct her left astigmatism, presbyopia, dry eye and allergies.
I like to start early presbyopes with multifocal lenses. I thought with Cathy I might get away with multifocal lenses without correcting the left astigmatism, yet even though she was right eye dominant by sighting techniques, she had left sensory dominance. Cathy couldn’t tolerate the astigmatism in the left eye being un-corrected; also she was more sensitive to extra plus being added to the left eye even when the astigmatism was corrected.
Taking this into consideration, I decided to fit her with a multifocal lens in the right eye and a toric lens in the left. Dailies Aqua Comfort Plus was a logical choice for lens material. Daily lenses are an excellent option for allergic conjunctivitis sufferers, decreasing overall symptoms of the condition.2 Nelfilcon-A has unique and quite novel biochemistry. It is based upon Polyvinyl Alcohol (PVA), which is used in many commonly available lubricating drops. A team at Aston University discovered that not all of the PVA in Nelfilcon-A was polymerised in the manufacturing process, leaving 0.5 per cent of the PVA remaining unbound. The unbound fraction was found to gradually seep from the matrix of the lens into the tear film throughout the day, thus offering contact lens wearers the benefit of lubrication of the lens surface.3
I fitted Cathy with Dailies Aqua Comfort Plus Multifocal in the right eye and Dailies Aqua Comfort Plus Toric in the left.
CL R/X BC: 8.7mm Diameter: 14.0mm R. +1.75 low add L. +2.50/-0.75×90
The lenses gave Cathy 6/6 acuity in both eyes and N3- near acuity. I prescribed a fish oil and flaxseed oil vitamin supplement and Optifree-Pro Moisturising Lens drops. She was very happy with the vision and continues to wear the lenses comfortably all day.
Sell Them the Science
Using your tools and educating your patients allows them to appreciate the complexities of fitting toric contact lenses and gets them invested in the result. A great quote I heard recently is that price is only a factor when there is an absence of value. In an era of decreasing contact lens margins it is more important than ever to make sure we are receiving adequate reimbursement for our clinical time and one of the easiest ways to add value is to incorporate technology into the exam room.
In summary, optometry may not exist without astigmatism. Optometrists are in the business of selling astigmatism and the astigmatic correction is no less important in contact lenses than it is in spectacles. In this age of simplification, it’s as important as ever that we sell our patients the science, so they leave our consultation rooms with a sense of value.
Mark Koszek B.Optom, M.Optom, Grad Cert Oc.Ther, completed his Bachelor of Optometry from the University NSW in 1995, his Master of Optometry in 2002 and Ocular Therapeutics in 2012. He is a founding partner of EyeQ Optometrists and has a large full scope practice in the southern Sydney suburb of Ramsgate. He is a councillor for the Optometry Association (NSW division) and is a Board Member of the Cornea and Contact Lens Society (CCLSA). Mark has been a fourth year clinic supervisor at the University of NSW since 2002 and has lectured extensively throughout Australia and internationally on contact lenses and dry eye management.
Mark Koszek was sponsored to write this article by Alcon. The views expressed in the article do not necessarily represent the views of Alcon or mivision.
NP4 Number # :A21605479154
References
1. Young G, Sulley A, Hunt C. Prevalence of astigmatism in relation to soft contact lens usage. Eye and Contact Lens, 2011; 37: 20-25
2. Wolffsohn JS, Emberlin JC. Role of contact lenses in relieving ocular allergy. Cont Lens Anterior Eye 2011 Aug;34(4):169-72. doi: 10.1016/j.clae.2011.03.004. Epub 2011 May 6.
3. Pruitt J. Triple action moisturisers for increased comfort in daily disposable lenses. OpticianOnline Nov 16. 2007, 27-28
