MYORING

FOR MYOPIA

What is shortsightedness (myopia)?

Myopia is a malrelation between the length of the eye and the refractive power of the cornea (dioptres). The cornea is the transparent layer of the eye on top of the iris (black, curved line). In most cases, the eye is too long and the refractive power of the cornea too strong, so that the rays of light which reflect a distant object are bundled in a point in front of the retina (see focal point of black rays of light in pictures on the right). This produces a blurry image on the retina and results in inaccurate vision in the distance. The retina - not to be confused with the cornea - is the light-sensitive layer at the back of the eye, which takes up the optical depiction. The retina is not explicitly illustrated in the pictures, and needs to be imagined in the point where the rays of light are supposed to combine to a focal point (focal point of red rays of light). The refractive power of the eye for light depends on the curvature of the corneal surface. Specifically, the dioptres (refractive power) are determined by the radius of the corneal curvature and are reversely proportional to the radius of the cornea. A short corneal radius corresponds to a high refractive power, which means that the eye is relatively myopic. The traditional method to correct myopic vision is to place appropriate glasses in front of the eye (red rays of light, top) or contact lenses onto the eye (red rays of light, middle). This helps to correct a person’s vision by shifting the focal point backwards to the retina (blue arrow). The rays of light are already diverted before they penetrate the eye and enable the eye to produce an accurate image of an object in the distance. Another option is to modify the too long corneal radius by changing the curvature of the corneal surface accordingly (refractive surgery). This is illustrated in the bottom picture: the initially stronger curvature of the cornea (black) is flattened (red, curvature radius of the cornea is increased). In a myopic eye, the centre of the cornea needs to be flattened to neutralise the excessive refraction power of the eye for light and shift the focal point backwards towards the retina (blue arrow).

What treatment options are available?

LASIK

In addition to glasses or contact lenses, there are also other more or less invasive procedures by which the corneal curvature can be modified. The most common of these treatment methods are those where corneal tissue is ablated by laser to correct the radius of the corneal curvature as needed. For further details please read the information under Scientific Background. The most common laser method is LASIK (Laser in situ Keratomileusis), where a broad flap is cut into cornea (image on the left). This flap is folded back to expose the deeper-lying corneal tissue and direct the laser beam on this tissue for ablation (black, ablated tissue in the image on the left). After laser ablation, the flap is pulled back into its original position and the corneal surface takes on its new geometry. In the myopic eye, more corneal tissue is ablated from the centre than from the edges to flatten the corneal surface. This method has the disadvantage that the flap does not heal and therefore no longer supports corneal stability. Hence corneal stability is sustainably weakened and impaired, which may lead to a severe post-operative long-term complication called post-LASIK keratectasia. The biomechanically effective corneal thickness (d), an indicator of corneal stability, is therefore much smaller than the anatomical thickness of the cornea. A much safer method is laser ablation of the corneal surface (PRK, LASEK). While this method also weakens the cornea, namely by the amount of tissue ablated for vision correction, the destabilising effect is far less pronounced because no flap needs to be cut; hence severe long-term complications rarely occur. The disadvantage of PRK and LASEK over LASIK is that LASIK causes no or only little post-operative pain, whereas LASEK and PRK may cause the patient considerable pain. This is due to the specific alignment of nervous fibres in the cornea. A more recent but increasingly adopted method is the implantation of lenses into the eye interior (phacic IOL), where vision correction is shifted from the cornea into the inner eye. This method tends to result in severe long-term complications. On account of these long-term complications, including cataract, glaucoma and corneal decompensation, this method should actually very restrictively be applied especially in relatively young patients as the complication potential of pIOL tends to increase over time. Another possibility is to remove the natural lens from the eye and replace it by an artificial lens. Since this results in the inability of the eye to accommodate for distance and nearness, and because the risk of lens capsule turbidity is higher in younger patients, this method (lens exchange) should not be applied in patients under 50 years of age. For elderly patients, it is a good option to correct higher refractive errors by surgery.

There is also an often unrecognized group of patients who want to be rid of glasses during every day life but do not have a problem to wear weak spectacles on special occasions such as night driving as long as the treatment method is minimally invasive and easily reversible as it is with MyoRing. These patients deny to perform Laser Vision Correction and intra-ocular implantations and accept MyoRing as a kind of permanent "contact lens".

How does the MyoRing treat myopia?

CISIS gives excellent results in cases not eligible to Laser Vision Correction! Whereas laser treatment irreversibly removes corneal tissue in order to flatten the central part of the cornea and correct myopic vision, MyoRing adds Volume to the peripheral tissue. This causes the collagen lamellae of the cornea to make a “detour” around the MyoRing, which also flattens the central part of the cornea and corrects myopic vision – but without sacrificing corneal tissue. The pocket guarantees that the entire cornea can adapt into a new shape and into a new biomechanics equilibrium. The MyoRing is therefore a fully reversible method. The light-grey line in the picture represents the shape of the cornea prior to the insertion of the MyoRing, the darker line the corneal shape after the procedure. The two smaller rounded shapes are cross sections of the MyoRing.

Since the MyoRing is designed as a fully closed ring with very specific properties (rigid yet flexible with shape memory effect), it allows to correct myopic vision in the range of -1 to -16 dioptres effectively, safely, and reversibly. Given the fact that this method is a biomechanical correction of myopia where the corneal geometry needs time to adjust to a new balance around the MyoRing, it may take 3-4 weeks until final visual acuity is achieved; patients need to take this into account in their workplace. The MyoRing rests inside a fully closed corneal pocket and therefore corneal stability is not compromised like after LASIK treatment. As described in further detail under Scientific Background, the lamellar pocket inside the cornea that takes up the MyoRing has biomechanically neutral properties; inserting the MyoRing into the cornea even increases the biomechanical stability of the cornea by a factor of 2.  While in LASIK the biomechanically relevant thickness of the cornea is less than the anatomical thickness, the opposite is the case in CISIS. The MyoRing strengthens the cornea in such a way that the biomechanically relevant thickness of the cornea (d) is usually even greater than the anatomical thickness.

When to use MyoRing for myopia?

Global Myopia Market

Despite aggressive marketing campaigns at global level throughout the past two decades, refractive surgery in general and laser vision correction (LVC) in particular have not been successful in gaining a significant share in the total market volume. Around 80% of the people with defective vision still wear eyeglasses, about 20% wear contact lenses, and only some 1% resort to surgical treatment methods. Safety is obviously the key feature for the patient´s selection of the treatment methods and global discussions about post-LASIK keratectasia or the potential short-term and long-term complications of phakic IOL´s do not increase the trust in refractive surgery, the related industry and the treatment providers. Many of the patients who deny refractive surgery as it is currently offered are, however, open minded to a minimally-invasive, safe and easily reversible semi-surgical approach such as the MyoRing which can be considered as a kind of permanent "contact-lens" which is unlike a conventional contact lens not worn at the top of the cornea but 0.3 mm underneath the corneal surface inside the cornea virtually within one of the 200 naturally existing corneal pockets in between the collagen lamellae.

Considering these figures it seems that the ophthalmic industry relies too much on the informations obtained from the surgeons which are in many aspects obviously not in agreement with the patients view.

Therefore, there is an often unrecognized group of patients who want to be free of spectacles during every-day life but do not have a problem to wear weak spectacles upon special occasions such as night driving, as long as the treatment method is extremely safe, minimally invasive and easily reversible as it is with MyoRing. These patients deny to perform Laser Vision Correction and intra-ocular lens implantations and accept MyoRing as a kind of permanent "contact lens".

The ideal group of patients who is almost always very happy with the results after MyoRing treatment are high myopic patients between 6 and 16 dioptres of shortsightedness who wish to be independent from spectacles and contact lenses in every day life e.g. for sports and leishure activity and even car driving by day, but have no problem to wear weak spectacles on special occasions e.g. for night driving. According to a recent study conducted by the AAO (American Academy of Ophthalmology) this group of patients represent nearly 4% of the American population. A similar figure can be expected in Europe. In South East Asia including China this percentage (prevalence) should be, however, significantly higher since the prevalence of myopia in general is also higher. While the prevalence of myopia is some 25% in America and Europe it is more than 80% in China.

A further group of patients who are doing well are between 2 and 16 dioptres shortsighted and asking for Laser Vision Correction but are not eligible for that treatment. If these patients wish to be spectacle independent for sports and other leishure activities and do not have a problem to wear weak spectacles upon special occasions such as night driving they are also excellent candidates for MyoRing implantation. The number of patient in that group can be estimated to some 5% of those seeking after Laser Vision Correction (LVC). It allows LVC Centers to treat patients not eligible to LVC in a minimally invasive and reversible way.

Patients who tolerate their contact lenses well and wish to have maximum visual acuity all day long are not the right candidates for MyoRing treatment.

For a successful myopia treatment by means of MyoRing the right patient selection is important and the surgeon has to be trained accordingly.

Which results can be expected?

Most of the cases performed are moderate and high myopic cases (> 6 dioptres) and not eligible for Lase Vision Correction for different reasons. An excellent indicator for success is the ability to legally drive a car without any optical correction.

In a recent study with very advanced myopic cases no eye had an uncorrected visual acuity (UDVA) of 0.5 while after MyoRing implantation more than 80% had uncorrected visual acuity of 0.5 and better and were therefore legally allowed to drive a car without any spectacle correction. 40% had uncorrected vision of 0.8 and better and even 20% had uncorrected vision of 1.0 and better.

The corrected vision (CDVA) did not change which is an important safety feature of the treatment. Only the dioptres needed to achieve that corrected vision were reduced in average from -11 dioptres preoperatively to -1 dioptres postoperatively (Daxer A. Corneal intrastromal implantation surgery for the treatment of moderate and high myopia. J Cataract Refract Surg 2008;34:194-198, Daxer A. MyoRing treatment of myopia. J Optometry 2016 (in press)).

In another study presented at the ESCRS 2015 in Barcelona which included less advanced cases some 10% were legally allowed to drive a car without optical aids  preoperatively while after surgery even 95% reached that improved uncorrected vision (see Figure). The remaining 5% required  a low dioptre correction only.

Case studies

In the following we report typical individual results which can be expected after MyoRing implantation. UDVA…uncorrected visual acuity, CDVA…corrected visual acuity

Patient ID 2396

A 26-year-old female patient with severe myopia of approximately 10 dioptres in both eyes underwent a MyoRing treatment in the left eye. She had been wearing contact lenses, but had not tolerated them well, and had been repeatedly suffering from severe inflammatory conditions in the eyes. Prior to MyoRing treatment, the patient had the following refractory power and vision accuracy:

CDVA           1.0         with         -10.5 s -0.25 c x 145°      I              UDVA           counting fingers

One year following her MyoRing treatment, the patient’s refractory power and visual acuity was:

CDVA           1.0         with         -0.5s -1.25 c x 150°          I             UDVA           0.7

The patient is highly satisfied and plans to undergo the same treatment in her right eye soon, where she is still wearing a contact lens. She manages most of her daily activities without any vision aids. When she takes out the contact lens from her right eye, the vision of her left eye is very good without a vision aid.

Patient ID 3884

A 25-year-old female patient with severe myopia and high-grade regular astigmatism in both eyes underwent MyoRing treatment in both eyes. She had been using contact lenses, which she hadn’t tolerated well; she had occasionally switched to relatively strong eyeglasses, but these had caused her great cosmetic problems. Prior to MyoRing treatment, the patient had the following refractive power and visual acuity:

Right eye CDVA           1.0         with         -7.25 s – 4.0 c x 5°           I             UDVA           counting fingers

Left eye CDVA           1.0         with         -9.25 s -2.75 c x 175°      I             UDVA           counting fingers

One year after MyoRing treatment, the patient had the following refractive power and visual acuity:

Right eye CDVA           1.0         with         +1.25 s – 2.75 c x 25°      I           UDVA           0.6

Left eye  CDVA           1.0         with         +0.25 s -1.25 c x 0°          I            UDVA           0.8

In the first months following initial MyoRing treatment, the MyoRing in the right eye was modified twice to optimise the result. Changing the MyoRing is almost as easy as changing a contact lens; it is 100% pain-free and usually takes less than a minute. The patient is satisfied and spends nearly the whole day without vision aids. In special situations, such as driving the car at night, she wears light and comfortable glasses.

Patient ID 5477

A 48-year-old female patient was extremely myopic and underwent a CISIS procedure. Prior to CISIS, the patient had the following findings:

Right eye CDVA           0.6         with         -16.50 s -0.5 c x 55°         I             UDVA           counting fingers

Left eye CDVA           0.6         with         -16.00 s – 0.5 c x 55°       I             UDVA           counting fingers

One year after CISIS, the patient had the following refractive power and visual acuity:

Right eye CDVA           0.6         with         -1.0 s                                  I             UDVA           0.5

Left eye CDVA           0.6         with         -1.5 s                                  I             UDVA           0.4

The patient basically needs no vision aids during her daily activities.

Patient ID 2949

A 22-year-old female patient was suffering from myopia and did not tolerate her contact lenses well. This is why she presented for a preliminary exam to undergo laser treatment. Since the exam revealed a suspicious corneal topography, the patient was recommended not to undergo laser treatment due to the risk of post-operative keratectasia following laser treatment. Initially, CISIS was performed in the left eye. Prior to CISIS, the patient had the following refractive power and visual acuity:

Right eye CDVA           1.0         with         -6.0 s -0.75 c x 175°         I             UDVA           0.05

Left eye CDVA           1.0         with         -7.25 s – 0.75c x 165°      I             UDVA           0.05

One month after CISIS, the MyoRing was replaced by another one with a different size because the patient was not fully satisfied with the result. After a further month, the patient’s treated left eye showed the following finding:

Left eye     CDVA           1.0         with         -0.5 s – 1.0 c x 5°              I             UDVA           0.8

The patient was still dissatisfied and complained in particular about halos around sources of light and glare phenomena. Upon the patient’s request, the MyoRing was removed. MyoRing removal is a harmless and pain-free procedure which only takes roughly one minute. One week after MyoRing removal, the patient had the following refractive power and visual acuity:

Right eye CDVA           1.0         with         -6.0 s -1.0 c x 5°               I             UDVA           0.05

Left eye CDVA           1.0         with         -7.25 s – 1.25 c x 170°     I             UDVA           0.05

Today, the patient wears her old eyeglasses again. She has no complaints whatsoever, except for the fact of having to wear eyeglasses.

Patient ID 3844

A 23-year-old female patient with contact lens intolerability presented at my practice to undergo a preliminary exam for laser treatment of her myopia. It turned out that laser treatment was contraindicated because the patient was suffering from rheumatic disease, a condition which may lead to irreversible turbidity of the central cornea. The patient’s wellbeing was severely compromised by the fact that she had to wear eyeglasses. Initially, I was apprehensive about performing CISIS as there is no scientific evidence to confirm the potential of rheumatic disease causing the corneal tissue to negatively respond to the MyoRing and leading to corneal turbidity. After an in-depth interview we agreed to take the inherent risk of a MyoRing treatment on condition that the patient is closely monitored for a minimum period of six months and the MyoRing is removed immediately upon the very first signs of corneal turbidity.

The refractive power and visual acuity before the CISIS procedure was:

Right eye CDVA           1.0         with         -2.25 s -0.75 c x 70°                       I             UDVA           0.4

Left eye CDVA           1.0         with         -2.75 s – 0.5 c x 100°                      I             UDVA           0.3

Six months after CISIS, the patient had:

Right eye UDVA           1.0

Left eye CDVA           1.0         with         +0.25 s – 0.75c c x 150°                 I             UDVA           0.8

Until the most recent examination (4 years after treatment), there were no signs of corneal turbidity. The patient is highly satisfied and needs no additional vision aids. 

Patient ID 2853

A 24-year-old patient with myopia had the following clinical findings:

Right eye CDVA           1.0         with         -9.0 s -1.0 c x 0°               I             UDVA           counting fingers

Left eye CDVA          1.0         with         -10.0 s – 0.75 c x 170°     I             UDVA           counting fingers

She underwent a CISIS procedure.

One year after CISIS, the patient had:

Right eye CDVA           1.0         with        -0.5 s -0.5 c x 10°                           I             UDVA           0.7

Left eye CDVA           1.0         with        -0.25 s – 0.5 c x 170°                    I             UDVA           0.8

The patient is satisfied and is almost entirely independent of vision aids. Only when driving at night, she occasionally wears eyeglasses.