Interventions to slow the progression of myopia in children

Introduction

Myopia is also referred to as nearsightedness. It is a condition where a child can clearly see the objects that are near, but all the distant objects appear blurred. In this state, the objects that are at a distant are focused in front of the retina rather on it as is the case in the non-myopic persons. Studies have established that myopia often occurs in a situation where the cornea or the lenses are very powerful, or the eyeball seems longer than normal. Research has confirmed that about 33 percent of the children are nearsighted (Cho, Cheung & Edwards, 2005). Myopia has recently become a severe and the most prevalent eye disorder. It is further believed to be the consequence of a complex interaction between the environmental factors and the genetic predisposition. Besides being an ametropic, a child with the myopic condition has the disadvantage of a severe complication like dense cataract, retinal detachment, glaucoma and even macular neovascularization which might further cause an irreversible blindness or even a visual impairment (Walline et all, 2011). In the modern day, there has been an increasing prevalence of myopic cases throughout the world to the extent that it has become one of the major alarming challenges to both the vision and the development of a child with effects on the life quality and economic burden due to the huge cost of treatment. According to Gwiazda et al., (2004), due to this, studies have extensively been focused on the prevention of the condition or even slowing down the progression of myopia. Based on the modern research accommodation has been proven to have a minor impact on the induction in addition to the progress of myopia contrary to the majority of the previous knowledge. In the recent times, the non-accommodative intervention likes the creation of myopic shift within the peripheral retina and changing the corneal shape by the optical intervention have substantially gained massive popularity in the control of myopic (Shih et al., 2001).

According to Gwiazda et al., (2004), myopia is thus the primary cause of reduced vision among the population all over the world and has been included as part of the five core priorities in vision 2020’ initiative by the WHO. Two percent of the US population has been shown to be myopic particularly at the school entry, and approximately 15 percent of the individuals entering high school are believed to be myopic. In addition to this, through research, racial and ethnic differences in the overall prevalence and magnitude of myopia have further been observed where both are greater in Asia and various parts of the world. Research has further established that juvenile-onset myopia in most occasions developed at about the between 6-8 and further progresses at a rate of 0.50 D (diopters) per year through 15 to 16 years (Shih et al., 2001). It progression is faster among children of younger ages; however, the onset, progression and even the stabilisation tend to vary significantly from one individual to another. Both boys and girls are affected by myopia in a similar proportion, and at the same time, the degree of the condition is also similar between both genders (Rose et al., 2008).

Etiology, prevalence and risk factors

Numerous factors play a significant role in the development of myopia. Most models have estimated a greater genetic effect when compared to the environmental effects for myopia. Those children whose both parents are myopic tend to have a greater axial length indicating a higher risk of myopia than those children with only one one or no myopic parents. Myopic persons often will exhibit a greater level of accommodation lag where they experience poor focusing accuracy when looking at the near objects than emmetropes those who might not need a spectacle to see both distant or near object clearly. Further, it has been established through research that the high accommodation lag in most instances will lead to blur that might further stimulate the growth of the myopic eye. There are also cases where few hours spend outdoors often might result to myopia (Cho, Cheung & Edwards, 2005).

Myopia as a common human disorder globally affects about 85 to 90 percent of the children in several Asian states including Taiwan and Singapore and between 25 and 50 percent of the older adults throughout the Europe and US. In Western population, the myopia prevalence has been reported to be low among children of age eight years and below. In the Asian children, it has been indicated that there is a higher prevalence of myopia that affects children between 9 to 15 percent of the preschool children, 24.7 percent of the seven years old and 49.7 percent of 9 years old primary school; children throughout Singapore (Rose et al., 2008). Further, research has shown that among 12 years old children, myopia prevalence is approximately 62.0 percent in Singapore and about 49.7 percent in Guangzhou compared to 11.9 percent Australia, 9.7 percent in the urban India, 20 percent in the US and 16.5 percent in Nepal. Research has confirmed that the overall economic cost of myopia condition was about US$268 billion globally. In the United States, an estimated 42 percent of the population is myopic, up from 25 percent in the 1970s. Developed Asian countries report myopia rates of 80 to 90 percent of young adults.

Presentation and diagnosis

The primary symptom of myopia is the blurred distance vision. Those children with the myopic condition tend to present an eye care practitioner after they failed a vision screening at the school or even after the parent and teacher notice a child either having problems seeing distant objects or squinting. According to Gwiazda et al., (2004), through the use of autorefraction or retinoscopy the eye practitioner can confirm myopia diagnosis in the most object way. There is the occasion where myopia could be established through carrying out a subjective refraction, and this method would demand the child’s responses. In conducting a child’s myopic diagnosis, a cycloplegic drop is placed in the child’s eyes which then hinder his or her capability to focus the eyes on determining and proper prescription efficiently.

Interventions to slow progression of nearsightedness in children

Laser refractive surgery-

The standard methods used in this approach include Photorefractive Keratectomy (PRK) and Laser In Situ Keratomileusis (LASIK) which can be utilised causing an everlasting central corneal curvature’s flattening through the removal of the stromal tissue using a laser (Hasebe et al., 2008). However, this intervention is commonly used among adults and might not be suitable for children because the child’s eye are still growing and the myopic condition continue to vary throughout the adolescent stage; therefore, a surgical procedure is often not regularly used in children. Refractive surgery has been sued for a long time to correct or even improve a child’s vision. Many surgical procedures can be applied to correct and adjust the eye’s focusing capability through shaping the cornea. A common type of procedure often used is the implanting of a lens in the eye. A conventional refractive performed on most patients is the LASIK, and it is used to reshape the cornea. For the children with myopia, a refractive surgery used will help reduce the cornea’s curvature which is believed to be steep to lessen the focusing power of the eye (Cho, Cheung & Edwards, 2005).

It is important that a type of refractive surgery to be used in correcting myopia should be arrived at after an exhaustive evaluation and discussion with a competent ophthalmologist. Keratomileusis was used for in the early 1970s in the US, and it adopted both the non-freeze and freeze technique. The method was later followed by the utilisation of an automated lamellar keratoplasty (ALK), where the medical practitioners used microkeratome to develop a hinged corneal flap or even a free cap. Research has however established that both ALK and Keratomileusis are considered as the imprecise approach in controlling myopia progression. The methods are highly advantageous in that they are associated with a faster visual acuity improvement and low postoperative medication use (Hasebe et al., 2008).

Progressive Addition Lenses

Based on the vast improvement that the progressive additional lenses (PALS) offer most adults suffering from presbyopia, research has shown that PALs for children could also be used efficiently to reduce the overall accommodative issues and decrease the progression of myopia. Evidently, PALs has been established to have numerous advantages to the patients. The adoption of progressive addition lenses (PALs) has shown significant treatment effects. However, it might be critical not to overstate its appearance among the children and the adolescents (Rose et al., 2008). Often the patients tend to enjoy a smooth vision’s transition from a far distant to a nearer vision without a definite distinction. Research has however identified one of the greatest drawbacks with the adoption of PALS which is related to the fact that there might be a period of adjustment when the patient would experience a peripheral distortion while in most instances some patients might not adequately adapt to PALs. 

The Correction of Myopia Evaluation Trial (COMET) to determine the impact of PALs as contrasted to single vision lenses was conducted on the progression nearsightedness. To complete the study, 11 investigators enrolled about 469 subjects of ages between 6 and 11 with the prescription for myopic between-1.25 and -4.50 spherical equivalents. One side of the study entailed a single a vision distance intervention and the second one had PAL lenses with approximately +2.00 add. The progression of myopic was looked at through cycloplegic refraction within a period of three years and established difference single vision lenses of about 0.20 D and PAL. Despite the fact that the study resulted in a similar outcome as determined by the researcher, the two were statistically significant; the researchers came to a conclusion that the utilisation of PALs as a clinical intervention alternative is often not suitable for the children and are not administered routinely (Rose et al., 2008).

Contact Lenses

Today, optometrists have begun fitting children with contact lenses and have been proven to be a highly viable option when it comes to the treatment of the progression of myopia among children. Studies have shown that majority of the children often feel very uncomfortable wearing glasses; therefore, contact lenses have gained massive preference from children since it enables them to see and at the same time feel better. Even though contact lenses have been shown to be effective, it has been associated with numerous disadvantages including, the likelihood of infection and increased chair time (Rose et al., 2008). However, there are ranges of contact lenses that can easily be accessed in the glasses market which provides a child with different alternatives in finding the correct fit for them. Randomised clinic trials confirmed that the soft contact lenses in addition to the rigid gas permeable lenses were less appropriate when it comes to retarding the progression of myopia.

In a Contact Lens and Myopia Progression (CLAMP) research, it was established that there existed a statistically significant variation in myopia progression in RGP vs. soft lens group. The slowed progression of myopia was a result of the corneal flattening but not a right slowing of myopia, and this might be reversible with RGP lenses wear discontinuation. The contact lenses, on the other hand, are considered an effective secondary management alternative for the myopic kids since they need a higher responsibility and dexterity to cater for their needs than a spectacle. However, research has shown that the lenses tend to bear a greater degree of risk ranging from the eye’s innocuous redness to a highly constant pain and the loss of vision as a result of corneal ulcers (Cho, Cheung & Edwards, 2005).

Gas Permeable Contact Lenses

They have widely been adopted over the years with an aim to slow down myopia progression. Research has found out that the probable mechanism for the effectiveness of GP in reducing and controlling myopia lies in the method’s ability to improve the retinal image than the rest of the control interventions available in the market (Rose et al., 2008). Several studies have been conducted to determine the effectiveness of GPs to the progression of myopic and one of the most current research established that the rigid GPs did not efficiently slow the overall progress level of myopic particularly among kids who were using the method routinely. In the research, the kids who were subjected to GP contact lens had remained highly myopic by 0.20D compared to those children with spectacle groups. The researchers thus came to a conclusion that GP contact failed to efficiently reduce myopic progression completely and hold very minimal promise for slowing the overall progression of myopia among children. GP lenses are, however, an effective solution when it comes to the correction of the vision and thus offers a highly and efficient alternative for kids that have been using the lenses; however, the method has not been entirely proven as the best alternative to control myopia.

Soft Spherical Contact Lenses 

Throughout the US, soft contact lenses have been widely used among the patients with myopia. These treatment methods are among the popular options for the correction of vision and have often been discussed by patients during the myopic progression evaluation. A study conducted by, the Adolescent and Child Health Initiative to Encourage Vision Empowerment (ACHIEVE) established that the use of soft contact lenses often does not result in a clinically appropriate rise of nearsightedness. The overall change rate annually was about 0.06D higher in those wearing soft contact lens compared to those wearing spectacles, but this was not a statistically significant difference even a period of three years. More often, a single-use disposable lens is often used to children to lay much emphasis on compliance and lower maintenance (Rose et al., 2008).

Multifocal Soft Contact Lenses

Multifocal contacts, on the other hand, can be considered as unique lenses that have different powers in various lenses’ zone used to control presbyopia and myopia. Medical practitioners found out that modified and the conventional multifocal soft contact lenses are appropriate for controlling myopia. Multifocal eyeglasses have extensively been tested for the correction and reduction of myopia progression among children; however, the outcome has been shown to be significantly less impressive compared to that produced by the multifocal contact (Rose et al., 2008). Studies published in the year 2000 and 2011 established that when a patient wears a multifocal eyeglass, it does not offer the significant level of reduction in progressive myopia among children. Multifocal and Bifocal soft contact lenses recently have emerged and become very familiar with suitable alternatives for the progression of nearsightedness. Spectacles in most instances are the first myopic child’s treatment since they offer a clear vision and further, they have been associated with a very minimal level of side effects. These spectacles are effective in correcting nearsightedness through the use of a concave lens that focuses light posteriorly which results in a clear image that will be focused on the retina. The typical example of multifocal spectacles includes the PALs and the bifocal spectacle; however, they have been shown to result in a minimal effect regarding slowing down the nearsightedness of myopia. 

In one of the studies, myopia progression in addition to the eye elongation was lowered considerably through the adoption of bifocal contact lenses. In a study, with forty children of ages between 11 and 14, they were provided with a dual-focus and single vision distance lenses for ten months. These lenses were later on changed between the eyes, and then the participant put them on for the following ten months. The outcome of the study established that among the 70 percent of all the kids, the progression of myopia was significantly lower by approximately 30 percent in the eyes wearing bifocal lens than to the single vision lenses. Therefore, research has shown that with the use of the bifocal lens, sustained myopic defocus can significantly lower the progression of myopia without necessarily compromising the visual function. However, there is the need for a better understanding f the type of design to be used in addition to the added power to offer suitable retinal images and blur to obtain excellent outcome (Shih et al., 2001). In another identical twin study, it was shown that a distance centre lens attained a higher level of improvement in the participants’ eyes that wore multifocal lens. In such a case, a multifocal lens was adopted as an off-label intervention for that individual who might be experiencing nearsightedness progression. However, despite its usefulness, multifocal lenses are currently not used widely as a first line treatment (Rose et al., 2008). A randomised clinical study throughout Denmark, US and Finland has established there is no significant slowing down of myopia using bifocals. One of the likely outcomes showed a 40 percent reduction in a study on a group of the Chinese Canadian children.

In the year, 2014, China and Australia researchers carried out a clinical trial that ran for three years evaluating the nearsightedness progression among a sample of 128 children with the condition of ages 8 to 13 years. The participants in this study confirmed to have experienced about -0.50 D of progression of myopia condition. One of the groups under study wore single vision eyeglass while the second one wore the bifocals while the third wore bifocal lenses with the prism. Within a period of three years, those children wearing the bifocal eyeglasses showed less mean progression of the nearsightedness of approximately (-1.01 D to -1.25 D) compared to those kids who had worn single vision lenses (-2.06 D).

Anti-Muscarinic Therapy-Atropine

The intervention method has been shown to cause light sensitivity or even a blurred near vision. In addition to this, they are not easily available for use. In a study with 23 clinical investigations of treatment of myopia among children, it was established that the use of antimuscarinic medication particularly eye drop had the most significant positive impact on controlling the nearsightedness progression (Fan et al., 2004). At the age of one year, those children who receive cyclopentolate eye drops, pirenzepine gel, or even atropine eye drops indicated a lower nearsightedness progression when compared to those kids who had received placebo. In Singapore, researchers adopted the use of topical atropine on approximately 400 myopic children of ages between 6 and 12 years. Topical atropine treatment was established to greatly tolerated and highly effective when it come to slowing down the progression of moderate and low nearsightedness in addition to ocular elongation among the Asian children. In the study, the overall mean myopia reduction in the atropine-treated eyes was about 0.03 +/- 0.50D, and in addition to this, there was myopia progression of -0.76 +/- 0.44D in placebo-treated eyes. Despite the fact that the method seems very efficient; studies have shown that it is not a first line treatment as a result of potential significant side effect often encountered by the antimuscarinic medication.

About half of the myopia school children in Taiwan often are prescribed atropine to control myopia (Shih et al., 2001). Studies have shown that eye doctors throughout Taiwan routinely prescribed atropine eye drop to correct myopia among the school children in the hope that the treatment will gradually slow myopia progression among these kids. Topical atropine is simply a type of therapy that is used to dilate the pupil of the patients and at the same time paralyse the accommodation while relaxing the eye’s focusing mechanism. It is, however, worth noting that atropine is often not employed for consistently dilated eyes since its action is often long lasting permanent used to reduce eye pain that is often connected to various types of uveitis. Research has shown that myopia is often linked to focusing fatigue hence atropine is suitable in disabling the eye focusing mechanism to control myopia (Rose et al., 2008).

Atropine Eye Drops has been established to have the potential of blocking the muscarinic receptors non-selectively. In addition to this, muscarinic receptors are common in the ciliary muscles, sclera and even in the retina (Saw et al., 2002). However, studies have not confirmed the exact mechanism of the atropine in the nearsightedness control. It is however believed that the atropine acts either indirectly or directly on the sclera or even retina which helps in thinning or stretching the scleral resulting to the growth of the eye. Several types of research have further shown the significant clinical effect of atropine in slowing down the myopia progression among children. The Atropine for the Treatment of Myopia studies (ATOM 1 and 2) was randomised, double-masked, placebo-controlled trials each with about 400 Singapore children. In the ATOM1 research, it was established that 1 percent atropine eye drop every night in one eye within a period of 2 years significantly slowed down the progression of myopia by about 77 percent and at the same time reduced axial elongation. The ATOM2 study, on the other hand, established dose-related responses with 0.5%, 0.1% and 0.01% atropine controlling the progression of nearsightedness by approximately 75%, 70% and 60% respectively over a period of 2-years. In a general view, atropine, 0.01 percent dose tend to offer an efficient risk-benefit ratio with no possible clinically visual side effect.

According to Gwiazda et al., (2003), the control effect of myopia control with the use of atropine is not long-term particularly after a year of intervention and at the same time. The short-term adoption of atropine might not adequately control myopia in the long run. It is evident that majority of the doctors seem to be reluctant when it comes to prescribing atropine for the children and this is because the long-term impact of the sustained used of atropine is not known. Other forms of problems associated with atropine intervention entail restlessness and higher level light sensitivity that result from the prolonged pupil dilation. Further, there are instances of blurred near vision in addition to increasing expenses where these children will demand progressive eyeglass lenses in addition to the bifocals throughout the treatment process to ensure that they apparently read because it tends to affect the child’s near focusing capability. Atropine is useful because it can help to inhibit the axial growth of eye that is associated with myopia; however, the medication works has largely remained unknown. Further, atropine has been associated with numerous side effects especially when provided in a higher level of concentration (Leung & Brown, 1999). 

Further, at the level that is often used for the treatment of lazy eye, the atropine tends to dilate the pupil. However, this often leads to light sensitivity and a blurry vision especially when the child looks at the objects that are closer. For those children who take a higher level of concentration, they are often required to wear sunglasses and bifocals. Further, the higher concentration has been shown to cause allergic conductivities and even dermatitis. Such drawbacks associated with the use of atropine. Apparently, explains why the treatment is often adopted for the treatment and control of myopic progression has remained uncommon throughout the US.

Orthokeratology

According to Gwiazda et al., (2003), orthokeratology entails the adoption and use of special designed gas permeable contact lenses which in most instances are inserted in the eyes when the patient is going to sleep especially at night to control myopia. However, this often is experienced for a temporary period in addition to various types of vision problems thus contact lenses and glasses are not required during waking time. Doctors have extensively adopted the use of ortho-k lenses in regulating the progression of myopia among children (Shih et al., 2001). Research has shown that myopic kids were undergoing some years of orthokeratology intervention; they end up with minimal myopic adults. Most eye care doctors often have referred to such lenses as the corneal refractive therapy. In overnight orthokeratology, a patient wearing a reverse geometry contact lenses temporarily flatten the cornea and offer a clear vision throughout the day without the adoption of glass or contact lenses. The reduction of myopia seems to be attained by the central corneal epithelial thinning, stromal thickening and even mid-peripheral epithelial (Rose et al., 2008). Since the year 2001, there have been about one hundred cases of severing microbial keratitis associated with orthokeratology. Several randomised clinical trials of orthokeratology myopia control have shown a slower axial elongation among kids wearing orthokeratology lenses than the kids wearing single vision spectacles. Orthokeratology contact lenses are effective in correcting the central refractive error while at the same time leaving the peripheral myopic blur that acts as a putative cue that helps in slowing down the myopia progression (Fan et al., 2004).

The intervention has been used for a long time in the treatment of myopia among both adults and children. It has been associated with higher level of improvement for the day-to-day vision without necessarily the help of glasses or even the daytime contact lenses. For many years, medical experts have realised that children have had a significant reduction in the progression of nearsightedness due to using orthokeratology lenses. Further, in a Longitudinal Orthokeratology Research in Children (LORIC), sample sizes of 35 children were followed for two years. Kids who had worn ortho-k lenses were looked at and then contrasted to a past number of kids who had worn a single vision lens. The LORIC studies focused on evaluating the axial length variation. From the research, the ortho-k group experienced a significant rise in overall myopia by approximately 0.29mm compared to 0.54mm in a controlled group. The same study further confirmed a similar level of reduction in the axial length elongation progression. Ortho-k has shown to result in the overall decline in myopic progression (Shih et al., 2001).

In the year 2011, research in Japan evaluated the impacts of ortho-lenses on the eyeball elongation among children a major factor linked to the progression of myopia. About 92 myopic children of ages 12 years were involved research that ran for two years where 42 of the participants had worn overnight ortho-k lenses while 50 had worn conventional eyeglasses throughout the day. By the end of the study, those kids with glasses showed the significant rise in the overall mean axial length of their eye compared to those with ortho-k contact lenses (Fan et al., 2004). The research thus came to a conclusion that the overnight orthokeratology greatly played a significant role in the suppression of the elongation of the eyes among kids. Ortho-k is thus suitable in slowing down the myopic progression contrasted to those who had worn eyeglasses. In the year 2012, research that ran for five years on about 43 myopic children which established that wearing ortho-k contact lenses overnight help in suppressing the eye’s axial elongation, than using conventional eyeglasses for controlling nearsightedness among children. In addition to this, a study carried out in Spain revealed that children of ages between 6 to 12 years of age with approximately 0.75 to -4.00 D of nearsightedness wearing ortho-k contact lenses for a period of two years had less progression of myopia. Further, they experienced a less axial elongation of their eyes compared to kids with myopia using eyeglasses for myopia correction (Leung & Brown, 1999). 

In the year 2012, another study carried out by researchers in Hong Kong to evaluate the impact of ortho-k contact lenses on regulating the progression of myopia among kids. It comprised of about 78 children with the myopic condition of ages between 6 and ten years at the onset of an investigation that was completed within a period of two years. The myopic children with ortho-l lenses showed a slower increase in the axial length of the eyeball by about 43 percent than those children who won an eyeglass. In addition to this, those children who were fitted with corneal reshaping GP lenses showed a significant control of the progression of myopia compared to the older kids.

Conclusion and Recommendation

Research has shown that the best way for the patient to take advantage of the available intervention strategies to regulate nearsightedness is having an early detection of the nearsightedness. Even in an instance where the child might not be complaining of vision problems it is important that they schedule a routine eye examination for the child before entering preschool. Further, early childhood eye exams are critical if either of the parents is nearsighted or when an older sibling has myopia or any form visual problem. Research has established that exercises in addition to under correction of myopia will lower nearsightedness thus an individual will demand less vision correction with time. Eye exercise programs require that one visits a doctor who will recommend an eyeglass prescription that will intentionally undercorrect the condition of myopia for a full-time wear. However, it is important to note that research has established that under correction of myopia might not be effective at slowing the overall progression of myopia rather it might increase the risk of nearsightedness hence making the condition worse. In addition to this, the intentional under correction of myopia often results in a blurred distance vision that might subject a kid at higher disadvantages in the classroom and sports hence generally affecting their overall safety. 

A suitable method of intervention that should be adopted in correcting myopia among children is orthokeratology lenses. Orthokeratology lenses are often worn only during the night when the patient is sleeping; therefore, there is very minimal or no discomfort that might arise from the lens-lid interaction. Overnight Orthokeratology lenses seem to be the most preferred option. They produce a corneal shape which is ideal for the prevention of axial length progression. It is suitable because it often makes use of a reverse geometry lenses which are flat in the centre with a steeping mid-peripheral curve hence allows the epithelium to move into a region and thicken at the mid-periphery. Therefore, when a patient wears the cornea at night, it will help to produce a focused image on the macula. Further, corneal shape induced by orthokeratology offers the mid-peripheral retina with a well-focused image which is a full productive impact that turns out to be important in controlling the progression of myopia.

In most instances, they are large lenses that do not move in the eyes and provoke sensation. Further, research has shown that the materials used are highly oxygen permeable. However, a group of US ophthalmologists have been very slow when it comes to embracing orthokeratology. Despite the fact that orthokeratology had been shown to have little value, the current procedures are radically different, and today, there is a vast body of scientific literature that primarily supports the adoption of overnight orthokeratology and its adoption in the progression control of myopia. Evidently, the technique has been proven to work hence can be used as the optional intervention to control myopia. Orthokeratology has further been highly satisfying for the practitioners. For the majority of the children, getting out of the eyeglasses often improves and boosts their self-esteem, and at the same time, the parents are highly gratified to be able to do something considered as positive for the child through reducing myopic progression. Further, for those children who are believed to be active particularly in sports, orthokeratology has been established to be very safe compared to glasses and more secure compared to the conventional contact lenses for swimmers. Therefore, it can be argued that myopia control is among the many compelling reasons why orthokeratology is often added to practice.

References

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