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Dr. Shrikant Waikar, W06753

ABSTRACT

The success of overnight orthokeratology and 0.01 % Atropine in controlling progression of Myopia has put the step forward towards a major intervention in childhood myopia. The focus till today was on refractive surgery once myopia stabilsed . Control of myopia progression in growing age group has led the way to evolution of a new field of Refractive ophthalmology from refractive surgery. 40 children with myopia from -1 D to -8 D including astigmatism , undergoing treatment with overnight orthokeratology or 0.01 % Atropine in age group of 7 to 14 were followed up for a period of one year. Unaided and best corrected visual acuity, refraction , slit lamp examination and any undesirable symptoms were recorded. Both the techniques were found to significantly slow down the progression of myopia. Overnight orthokeratology in addition also significantly reversed the myopia and maintained the refractive correction with weekly application of lens in most cases.

Introduction

Myopia is known to mankind since ages. A number of methods have been tried for controlling myopia. Ancient Chinese used sand bags for flattening cornea. Spectacles and conventional contact lens have been used since  long time for correction of myopia. Then came the era of refractive surgery – Keratophakia , keratomileusis [1], Radial keratotomy [2], LASIK and its variants , Femtosecond laser assisted procedures , Small incision lenticule extraction ( SMILE ) etc. Refractive surgery became a subspeciality  in itself . Procedures came and became obsolete. As more and more research went into refractive surgery it became more and more equipment intensive. But Refractive surgery has its limitations. It can be performed  only beyond 20 years of age ie once myopia stabilises. A very significant part of life history of myopia has remained untouched. Myopia starts in childhood and progressively increases in magnitude . Rapid increase occurs around puberty when growth spurt occurs. Despite having known these facts ophthalmologists have remained mute spectators thinking that nothing can be done to prevent this increase in refractive power in Myopia. But the success of overnight orthokeratology and 0.01 % Atropine in controlling progression of Myopia has put the step forward towards a major intervention in childhood myopia. The focus till today was on refractive surgery once myopia stabilsed . Control of myopia progression in growing age group has led the way to evolution of a new field of Refractive ophthalmology from the shadows of refractive surgery. This paper evaluates Overnight orthokeratology and 0.01% Atropine eye drops as an intervention in childhood myopia .

MATERIAL AND METHODS

80 eyes of 40 children in the age group 7 – 14 years were evaluated .

Children with myopia from -1 D to -8 D including astigmatism , undergoing treatment with overnight orthokeratology or 0.01 % Atropine  were followed up for a period of one year.

INCLUSION CRITERIA

–   Age group between 7 yrs to 14 yrs.

  • Myopia (Spherical equivalent) -1.00 D to – 8.00 D.

 

EXCLUSION CRITERIA 

– Corneal dystrophies.

– Dry eyes.

– Any other associated ocular disease.

– Any ocular Surgery in the past.

  • Any ocular surface pathology.

 

The study was divided into two parts . A combined retrospective and prospective study was carried out. Overnight orthokeratology was studied retrospectively while 0.01 % Atropine was evaluated prospectively. The documents of 40 eyes of 20 patients who were under follow up for overnight orthokeratology for over one year were analysed. These patients were prescribed orthokeratology lens. These patients   wore the lens every night for 21 days and then wore the lens regularly at 2 -7 days interval based on the maximum lens free duration required to maintain the visual acuity . Outcome measure was change in refraction or  requirement of change in orthokeratology lens.

40 eyes of 20 patients were treated with 0.01% atropine once a day . Monthly follow up was done for one year. Outcome  measure was change in refraction .

Pretreatment and post treatment unaided visual acuity, Objective and subjective refraction, slit lamp examination was carried out at every visit.

Any untoward effects were recorded. Difference in refraction between onset of treatment and at the end of one year was noted and analysed.

RESULTS

In the orthokeratology group 40 eyes of 20 patients were included .

The youngest patient was 7 year old and the oldest was 14 years of age. There were 6 patients in 7 to 9 years age group, 8 between 10 to 12 years and 6 were  from 13 to 14 years  [Table-1]. There were 8 males and 12 females [Table-2]. 18 eyes had simple myopia and 22 had compound myopic astigmatism [Table-3]. Eight eyes had against the rule astigmatism of -0.50 D to -1.00 D. 14 eyes had with the rule astigmatism ranging between -0.50 D to -1.00 D.  The spherical equivalent refraction was calculated and the effect of overnight orthokeratology with 5 curve reverse geometry corneal reshaping lens was assessed. 32 eyes had myopia (spherical equivalent) of -1.00 D to -3.00 D . 6 eyes had myopia (spherical equivalent) between -3.00 to -6.00 D .  Two eyes had myopia (spherical equivalent) of -6.00 D to – 8 D.  The only side effect observed was punctate staining of central cornea in 2 eyes which improved with application of ocular lubricants.

In the 0.01% Atropine group the youngest patient was 7 year old and the oldest was 14 years of age. There were 8 patients in 7 to 9 years age group,  6 between 10 to 12 years and 6 were  from 13 to 14 years  [Table-1]. There were 11 males and 9 females [Table-2]. 23 eyes had simple myopia and 17 had compound myopic astigmatism [Table-3]. 9 eyes had against the rule astigmatism of -0.50 D to -1.00 D. 8 eyes had with the rule astigmatism ranging between -0.50 D to -1.00 D. 26 eyes  had myopia (spherical equivalent) of -1.00 D to -3.00 D . 10 eyes had myopia (spherical equivalent) between -3.00 to -6.00 D .  4 eyes had myopia (spherical equivalent) of -6.00 D to – 8 D. The only side effect in some patients was mild photophobia. There was no requirement of change in othokeratology lens in any of the eyes. All children with Myopia remained spectacle free with those upto 3 dioptres requiring a weekly application while those upto 6 Dioptres required every third day application. One child with Myopia of 6.5 D required an alternate day application to remain free of glasses. There was no increase in refractive power of eyes in the age group up to 12 years in both the groups.The mean increase in spherical equivalent at the end of one year in the age group of 13 – 14 yrs was 0.025 D in Orthokeratology group  and 0.050 D in Atropine group  .

Discussion

A number of methods have been tried in the past for controlling myopia. Ancient Chinese used sand bags for flattening cornea. Spectacles and conventional contact lens have been used since  long time for correction of myopia. But myopia management has largely been overshadowed  by refractive surgery.The era of refractive surgery started with  Keratophakia , Keratomileusis[1,], Radial keratotomy[2] and continued with LASIK and its variants , Femtosecond laser assisted procedures , Small incision lenticule extraction ( SMILE ) [3] etc. Refractive surgery became a subspeciality  in itself .   The art of refraction having been transferred to optometrists ,refractive surgery was actively promoted in all ophthalmology forums. A number of procedures came and became obsolete.Being highly equipment intensive ,refractive surgery today has remained within reach of only a small proportion of ophthalmologists. However refractive surgery has its limitations . It can be performed only once the myopia is stabilised usually after 20 years of age. It is irreversible and regression of myopia is known to occur with time.

Not much thought has gone into the management in the critical initial years of myopia. As the myopia increases with growing age of the child appropriate timely intervention can reduce the progression of myopia. No refractive surgery can be performed in a child but a child also  aspires to be free of glasses . Spectacles become a handicap especially if the child participates in hobbies like dance, or sports like running , volley ball,basketball etc or any contact sports like boxing , judo etc.

In this scenario two interventions have emerged – overnight orthokeratology [4,5] which not only reverses myopia but also slows down the progression of myopia [4-11] and 0.01 % atropine [14] which also slows down the progression of myopia. A new field of Refractive ophthalmology which is much less equipment intensive and is much less expensive and has the potential of transforming myopia outcomes is now emerging , evolving out of the shadow of refractive surgery. Refractive ophthalmology  encompasses the management of childhood myopia with the aim of reducing the progression of myopia thus avoiding all the complications of high myopia. In addition Orthokeratology also helps the children to remain spectacle free and thus would enable them to participate in all outdoor activities which in turn again would help in myopia outcome. This study analysed retrospectively the cases of overnight orthokeratology and prospectively the cases on treatment with 0.01% atropine. None of the orthokeratology patients required a change in lens at one year followup. There was no change in refractive power in any of the patients in the age group upto 12 years in both the groups. All patients of myopia in Orthokeratology group in addition remained spectacle free for the entire duration of one year . They could participate in any activity of their choice whether dance, sports including contact sports. This not only enabled the overall development of the child including his confidence levels but also encouraged the child to participate in outdoor activities which in turn again contributed towards reducing the progression of Myopia. Increase in refractive power was noted in both the groups in the age group of 13 – 14 years . This was expected as it matched with the growth spurt in the child. Correlation of myopia with the growth spurt has been documented in a study by Vivien Cherng-Hui Yip, Chen-Wei Pan, Xiao-Yu Lin et al [12]

The mean increase in Orthokeratology group was 0.025 D . The mean increase in Atropine group was 0.05 Dioptre. The increase in myopia was found to be more in atropine group.The difference was statistically significant.  In both the cases the increase in myopia was much less than expected normal progression at the time of puberty . The expected increase in Myopia has been documented to be around around −1 D per year in East Asians and around −0.5 D per year in Caucasians  [13,14]. Both the forms of treatment were successful in keeping the rate of progression much below the expected rates as mentioned in literature. The mechanism by which orthokeratology reduces the progression of myopia  has been proposed to be a shift to myopic defocus in midperiphery by orthokeratology lens. Spectacle correction and conventional contact lens cause hyperopic defocus in midperiphery which acts as stimulus for increase in axial length.

The mechanism of topical atropine is not just inhibition of accomodation but also the up- and down regulation of retinal and scleral muscarinic receptors with influence on the scleral matrix [15, 16].  Atropine has been found to inhibit myopia induction in both mammalian and avian eyes [17,18]. In contrast to mammalian eyes which contain smooth muscles the avian eye contains striated ciliary muscle innervated by nicotinic receptors rather than muscarinic receptors [22]. Therefore, atropine may function at a relatively lower dose, through M1/M4 receptors in the retina, and not via the accommodation system . On the other hand, a non-muscarinic and a direct influence of atropine on the scleral fibroblasts could also contribute to the effect [28].

A number of studies have documented the role of orthokeratology in slowing down the progression of myopia [4-11]. Similarly Atropine in various concentrations has also been widely researched [12-16]. This study has shown the effectiveness of both the techniques in reducing the progression of myopia.In fact no progression was seen in prepubertal age groups. The age group of 13 -14 years also showed significant slowing down of progression of myopic growth spurt. Myopic growth spurt with pubertal changes has been documented in literature[12]. The sample size in this study was less. A larger study with more subjects using the other eye as control is recommended to further prove the efficacy of these techniques. However more and more researchers are convinced  about the efficacy of these techniques in retardation of myopic progression. Another trial is underway studying the complimentary effect  of Orthokeratology and 0.01 % atropine in controlling the progression of myopia [19] .

The burden of myopia is increasing by the day. Besides the refractive element the other changes due to high myopia including retinal degenerations and even retinal detachments are well known [20].

Despite growing evidence in literature , orthokeratology [4-11]and use of 0.01% atropine [23-27]  have not come into active  clinical practice. These simple interventions have the potential to bring down the burden of high myopia in the population. The time has now come for these techniques to be included into the armamentarium of ophthalmologists and refractive ophthalmology emerges out of the shadow of refractive surgery.It will be a small step for man but a giant leap for the mankind.

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TABLES

Table1   Age of patients

AGE(years) Orthok Group Atropine Group
7 to 9 6 8
10 to 12 8 6
13 – 14 6 6

Table 2    Sex distribution

Sex Orthok Group Atropine Group
Male 8 11
Female 12 9

Table 3   Type of Myopia.

Type of Myopia Orthok Group Atropine Group
Simple Myopia 18 23
Compound Myopic   Astigmatism With the rule         14 With the rule           8
Against the rule      8 Against the rule       9

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