Myopia is a common eye disease worldwide.1 Progressive myopia can lead to marked visual impairment because of myopic retinopathy,2,3 which poses a risk of blindness to about three million Americans4,5 and approximately 1% of the Asian population6 who have pathologic myopia. Prevalence and progression of myopic retinopathy have been shown to be closely related to the magnitude of the refractive error and to the axial length of the eye globe.2,3 In a study by Liu et al,2 15.9% of myopic retinopathy was found present in a population with myopia of −4.0 to −5.99 diopters (D), 40.4% was found present in a population with myopia of −6.0 to −7.99 D, and 72.9% in a population with myopia of −8.0 to −9.99 D. Therefore, slowing down the progression of myopia would save sight for these patients. Presently, there is no effective method for slowing down the progression of high myopia, although the use of bifocal spectacles or dual-focus soft contact lenses has shown some efficacy in cases of mild and moderate myopia progression in two recent randomized trials.7,8
Posterior scleral reinforcement surgery was first proposed by Shevelev9 in 1930. Since then, Snyder and Thompson have modified the technique.10–12 Subsequent reports by others have claimed the effectiveness of posterior scleral reinforcement surgery,13–17 although there was also a negative report with a longer follow-up.18 Therefore, the efficacy of this surgery has varied in western countries because of variations in the surgeries and the study designs.18–23 However, this type of surgery is still practiced in many eye institutes outside of the United States.13–17,23–27 In our institute, this surgery is also performed on patients with high myopia using informed consent. Recently, a retrospective clinical study showed that posterior scleral reinforcement controlled the progression of axial length in patients with high myopia when compared with the nonsurgical contralateral eyes in an adult population.23 Up to now, many of these studies have had the surgery performed in both of the patient’s eyes, without a natural progression in the fellow eye to be used for comparison. There is no carefully designed prospective study to evaluate the efficacy of this treatment modality on young patients who have high myopia and rapid progression. The current study aimed to evaluate the posterior scleral reinforcement surgery on young high myopia using a prospective study design.
Approval was obtained from the Ethics Committee of the Eye Hospital, Wenzhou Medical College, to conduct this clinical research before the initiation of the study. The procedures used for surgery, examinations, and follow-ups conformed to the tenets of the Declaration of Helsinki, and patients/parents signed an informed consent form before entering the study. The parents of the patients were informed about the goal of the procedure (to prevent further axial myopia progression, with the hope of limiting future myopic retinopathy), surgical procedures, possible complications, and possible outcomes. Patients agreed to accept the surgery on one of their eyes and consented to at least a 2-year follow-up after surgery. In addition, parents and patients were informed that there is no approved method to stop myopic progression and that the current surgery may or may not prevent the myopic progression, rather, the procedure would need to be scientifically assessed through postoperative follow-ups. In the case of obvious anisometropia, the more advanced eye was operated on; otherwise, the surgically treated eye was determined by patient preference. From August 2008 to October 2010, consecutively, 35 patients participated in this study and had the posterior scleral reinforcement surgery on one of their eyes while the contralateral eye was left untouched. The entry criteria were (1) patients with high myopia were followed in the myopia clinic during the preceding 2 years with a spherical equivalent (SE) increase equal to or greater than 1.0 D per year; (2) patients had an SE refractive error greater than minus 5.5 D and a global axial length greater than 24.5 mm if patients were younger than 8 years old or SE greater than minus 7.0 D and the global axial length greater than 25.5 mm for patients between 8 and 18 years old. The age of 8 years was used as a delineator because the eye size and growth rate were different between the ages of 1 and 8 years and 8 and 20 years.28 Out of the 35 pediatric patients, 30 of them, who were followed for 10 months or longer, were included in the current analysis. Ten months of follow-up was selected because clinical trials have shown that a significant change of axial length was observed within 10 months of follow-up succeeding a study intervention.8 For the current study, the shortest follow-up was 323 days and the longest follow-up was 1306 days, with a mean of 895 days and a median of 913 days.
Before surgery, both eyes underwent a baseline examination looking at the best corrected visual acuity, intraocular pressure (IOP) (Canon TX-F Full Audio Tonometer, Canon Inc., Tokyo, Japan), manifest refraction (RT-2100 phoroptor, Nidek Inc., Gamagori, Japan) or retinoscopy for refractive errors, IOLMASTER (Carl Zeiss Meditec AG, Jena, Germany) for corneal refractive and axial length, fully dilated fundus examination using slit lamp and indirect ophthalmoscope, and B-type ultrasonography (Carl Zeiss Meditec AG) for staphyloma. The patients stayed in the hospital for 1 week after the surgery and were instructed to pay follow-up visits postoperatively at 1, 3, 6, 12, and 24 months. At each visit, examinations performed during the baseline visit were also conducted. At the most recent follow-up visit, an additional assessment of the macula using optical coherence tomography (OCT) (Optovue Inc., Fremont, CA) was also performed.
The human sclera was obtained from a local eye bank after the cornea was removed for transplantation. The donor had negative serology for HIV and hepatitis B. After a complete evisceration of the eye globe, the sclera was divided into two equal halves and completely washed in 0.9% saline before being immersed in 75% ethanol for 48 hours. The sclera was then transferred into 100% ethanol for 3 to 6 months until usage. Upon surgery, the preserved scleral half was trimmed into the shape as shown in Fig. 1 with a width of 2 to 3 mm at two ends, a width of 10 to 12 mm in the middle and 35 to 45 mm long, depending on the size of the receiving eye globe. The preserved sclera was hydrated in 0.9% saline for at least 5 minutes before use. The posterior scleral reinforcement surgery was performed under general anesthesia. After routine sterilization preparation, a speculum was inserted. A 210-degree conjunctiva peritotomy was performed along the inferior-temporal limbus. A radial cut was made at each end of the peritotomy to expose the inferior and external rectus muscles. Traction sutures were prepared for the inferior and external rectus muscles. With the help of the traction sutures and a muscle hook, the reinforcement scleral flap (40 by 11 by 0.8 mm) was passed underneath the inferior oblique, external rectus, and inferior rectus sequentially. During this process, protecting the orbital septum and vortex veins is very important. One end of the flap is fixed to the sclera 3 to 4 mm behind the insertion of the inferior rectus muscle, and the other end was wrapped around the posterior pole and fixed to the sclera 3 to 4 mm behind the insertion of the superior rectus muscle using 5-0 nylon sutures. The reinforcement flap was stretched to surround the posterior pole in a U-shape (Fig. 1). Posterior pole and flap were checked for proper position and orientation before the conclusion of the procedure.
On completion of the surgery, patients were closely monitored by the anesthesiologist until fully recovered. The eye patch was removed on the second day, and a regimen of 0.5% levofloxacin eye drops QID, 0.1% pranoprofen eye drops QID, and 0.1% fluorometholone eye drops QID was prescribed for 2 weeks.
Continuous ocular parameters such as eye refractive power, global axial length, cornea refractive power and axis, and retina thickness or volume were expressed as means and SDs and compared between surgically treated eyes and their contralateral eyes using a paired t test. To identify the surgical effect, the difference between the changes of the axial length or SE from their baseline for the surgery eyes and the changes for the contralateral eyes was calculated by subtracting the changes for the surgery eyes from the changes for their contralateral eyes. The bigger the difference, the larger the surgical effect achieves. A multiple linear regression was performed using surgical effect as a response, whereas sex, age, baseline SE and axial length, and presence or absence of staphyloma were used as independent factors. Because of the collinearity between the baseline SE and axial length, these two factors were evaluated separately, along with the other factors. All statistical analysis was performed using JMP statistical software version 11. A value of p < 0.05 was considered statistically significant.
Baseline Characteristics of the Patients
There were 30 patients in the current analysis, 21 males and 9 females. Patient ages ranged from 4 to 15 years old, with a mean age of 7.5 years old. The difference of SE between the surgically treated eyes and their contralateral eyes ranged from 0 to 3.0 D, with the exception of two patients whose SE difference was 7.4 and 5.6 D, with a mean difference of 1.1 ± 1.9 D as a whole. The time of follow-up after surgery ranged from 323 days (10.8 months) to 1306 days (3.6 years), with a mean follow-up time of 895 days (2.5 years).
Out of 30 eyes, which had the posterior scleral reinforcement surgery, 15 of them showed obvious staphyloma in B-type ultrasonography before surgical intervention. The baseline information for the patients is summarized in Table 1.
Surgical Effect in Slowing Down the Progression of Axial Myopia
The elongation of the axial length between the final follow-up and the baseline was significantly less in the surgically treated eye group than that in the contralateral eye group (0.75 vs. 0.94 mm, p < 0.0001, paired t test). A similar analysis also revealed a lower increase in the SE (0.7 D less) for the eyes associated with the posterior scleral reinforcement surgery (p < 0.001, paired t test).
The multiple linear regressions revealed that both the baseline axial length and SE were not significant predictors for surgical effect size. However, the presence of staphyloma was significantly associated with a smaller surgical effect (p = 0.0036; Fig. 2); and patient age showed a nonstatistically significant trend that patients at younger ages gained a larger surgical effect (p = 0.0986; Fig. 3). The surgery effect size did not accrue or diminish during the follow-up period (Fig. 4).
Safety and Complications
There were no complications noted in the study. The mean visual acuity at the final follow-up improved slightly from baseline in both groups, and the posterior scleral reinforcement did not adversely affect the visual function of the patients (p = 0.88, paired t test; Table 2). Similarly, the posterior scleral reinforcement did not affect ocular pressure or cornea refractive powers at the two major meridians and their axis (Table 2).
At the final follow-up, an OCT demonstrated that there was no significant difference in retinal thickness and volume at the macula between the contralateral eyes and the surgically treated eyes (Table 3; Fig. 5).
High myopia with growing axial length can stretch the sclera, choroid, and retina at the posterior pole including macula, leading to a thinning and degeneration of the retina and choroid with a resultant myopic maculopathy and visual impairment.3 The impact of myopic retinopathy on visual function is important because the maculopathy is often bilateral, irreversible, and onset is during one’s most productive years.2,29 Because there is no cure and the damage from the axial expansion is not reversible, prevention becomes extremely desirable for both the patient’s family and the ophthalmological community. Several studies have investigated the preventative effect of various spectacles or contact lenses on the progression of axial myopia in mild and moderate myopic children.7,8,30 These noninvasive ways are not suitable for rapid progressive high myopia such as the patients in the current study.
The patients in the current study had a mean age of 7.5 years and a mean axial length of 26.2 mm, which is more than 3 mm longer than that of an emmetropia with the same age.28 Scleral thinning, particularly at the posterior pole of the globe, has long been known to be an important feature of high myopia in humans.31 One of the most important clinical consequences of such thinning is the formation of a posterior staphyloma, which was present in 50% of our patients. Such advanced high myopia may not be responsive to noninvasive preventative techniques such as dual-focus contact lenses or bifocal spectacles.7,8 In the current study, we prospectively designed a paired-eye comparison study to eliminate variations such as age, sex, onset of myopia, and environmental or genetic factors.32
To the best of our knowledge, this was the first such design to tackle this controversial surgical practice.24 This design allows a comparison between the experimental and control eyes for progression of myopia from baseline. Our study showed that a posterior scleral reinforcement did slow down the axial length elongation as compared with that of their contralateral eyes. The progression of both axial length and refractive power was significantly less, statistically, than that of their contralateral eyes during a mean follow-up of 2.5 years after adjusting for age and follow-up time. As expected, axial length elongation is positively associated with follow-up time and negatively associated with patient age. The current study found that less surgical effect was gained for eyes with staphyloma. This may be caused by the fact that the eyes with staphyloma had a more advanced stage of disease, including scleral abnormality. This finding may also suggest that more force should be applied using a donor scleral strip during surgery. In addition, we found a trend that younger patients gained more of a surgical effect or a larger surgical effect size. This may be caused by the difference in eye growth rate between very young children and preteen children or teenagers. Song and et al28 demonstrated that children younger than 8 years old had a much faster eye growth rate than children older than 10 years old. Faster growth may be hindered more by a similar force than a slower growth. It has been questioned if posterior scleral reinforcement can provide a long-term effect on slowing down axial length elongation. Fig. 4 suggests that the surgery did show an effect, but there was no accruing effect. This may be attributed to the degradation of the implanted sclera and a loss of the applied reinforcement effect during the initial few months after the surgery. A better reinforcement material or collagen cross-linking of donor sclera may improve the surgical result in the long run.33,34 In addition, synthetic materials have been investigated for use in scleral reinforcement, which may ease the limitation of human sclera donor availability and may possess a superior durability to the degradation caused by biological enzymatic systems as well as offer a better reinforcement effect.35–37
There is no similar study available to compare with the current study; a retrospective study performed on adults showed effective management of the axial length using a posterior pole buckle procedure, which is similar in concept to the scleral reinforcement effect.23 In a previous experimental study on growing cat eyes using scleral reinforcement surgery, Jacob-LaBarre et al38 also found that scleral reinforcement seems to control the expansion of the growing cat eye, although to a limited extent. Our current human study had a similar conclusion, which showed some degree of delay for axial elongation by the surgery but the surgical effect size was small. Whether the surgical effect can be greater or diminish over time needs a longer follow-up and analysis. From the current analysis, within the 2.5 years’ follow-up time, the surgical effect seems to hold well because the regression lines from the surgery eye and the fellow eye correspond to one another.
In the current study, there were no complications noted during the postoperative follow-ups. This was evidenced by no significant changes seen between the surgically treated eyes and the contralateral control eyes for best corrected visual acuity, IOP, cornea refractive power and axis, as well as retinal thickness and volume at the macula (Tables 2, 3). We think that the effect of the scleral reinforcement may be highly dependent on the surgical technique and the tissue trimming that go into the surgery. All of our surgeries were performed under general anesthesia with a direct view under a surgical microscope. The donor sclera was custom trimmed into a spindle shape, with a wider part covering the posterior pole and the narrower sections serving as anchors. The spindle-shaped donor sclera strip needs to be placed underneath the external rectus, inferior oblique, and inferior rectus muscles to fit the receiving globe. Microscopic surgery enhances secure anchoring and avoids vortex damage as well as accidental globe perforation. We did not find choroidal effusions or eye motility restriction, which has been reported after a similar surgery for control of progressive high myopia in adults.23 The difference may be caused by the applied suppressive strength in the patient’s globe exerted by the donor scleral flap through the surgery or the age difference in the study population. Younger eyes often have a much better ability to recover from surgery and, at the same time, myopic progression is faster. Indeed, in the retrospective study of Ward et al,23 the nonsurgery eye progressed about 0.4 mm during 2.5 years of follow-up, whereas the nonsurgery eyes in our study progressed 0.95 mm. In the study by Ward et al,23 the surgery effect (axial length difference between the surgery eyes and the nonsurgery fellow eyes) was 0.4 mm, which was larger than the 0.2 mm we achieved at a postsurgical follow-up of 2.5 years. We speculate that, through a more suppressive strength exerted by the donor scleral flap, the greater the control of axial elongation may be achieved. However, more complications such as ocular motility restriction, increased IOP, and even choroidal effusions may result.
In summary, through this prospective intrasubject paired-eyes study, we conclude that appropriate posterior scleral reinforcement surgery can control myopic progression to some extent within a follow-up time frame of 30 months. These patients demonstrated a yearly progression of 1 D before the surgery; after the surgery, surgically treated eyes showed only a 1.12-D progression within 2.5 years of postoperative follow-up, whereas contralateral control eyes showed about 1.82 D of progression within the same period. The reinforced posterior sclera countering the elongation force may explain the surgical effect of this study.
We acknowledge the limitations of this study such as nonrandomization of the surgically treated eye and less than desired regular follow-ups between the surgery and the last follow-up. A study with a longer follow-up time is needed to further assess the surgical effect and adverse effects. These study results should not be generalized to a mild or moderate myopic population whose progression may be inhibited by noninvasive or less invasive interventions such as wearing dual-focus soft contact lenses or bifocal spectacles.7,8 Although the surgical effect demonstrated in the current study is statistically significant, the axial length and refractive power change was limited. Considering the good safety profile and the limited surgical effect size, this procedure should only be offered to a well-selected group of pediatric patients with a high axial myopia and should be treated as an investigational procedure. Nonetheless, to the best of our knowledge, this is the first prospective and self-controlled clinical study on this contentious intervention to fight the progression of high myopia.
Institute of Ocular Pharmacology
School of Ophthalmology and Optometry
Wenzhou Medical College
270 Xueyuan Rd
Wenzhou, Zhejiang, 325027
e-mail: email@example.com; Jqu@wzmc.edu.cn
Financial support was received from the National Natural Science Foundation of China (Grant No. NSFC31271022). This study was also supported by the Science and Technology Plan Project of Wenzhou Science and Technology Bureau (C20120009-05). The authors have no financial/conflicting interests in any aspect of this study.
Received June 14, 2013; accepted December 18, 2013.
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Keywords:© 2014 American Academy of Optometry
posterior scleral reinforcement; progressive high myopia; prevention of degenerative myopia; myopic axial elongation; human sclera