Cataracts in Children, Congenital and Acquired
A cataract is any light scattering opacity of the lens. It is estimated that congenital cataracts are responsible for 5% to 20% of blindness in children worldwide. Incidence varies from country to country. One retrospective study of the prevalence of infantile cataracts in the U.S. showed a rate of 3-4 visually significant cataracts per 10,000 live births. This is a similar rate to a U.K. study which showed 3.18 per 10,000.These numbers underestimate the total number since they do not take into consideration visually insignificant cataracts.
Cataracts may be unilateral or bilateral and can vary widely in size, morphology and degree of opacification from a small white dot on the anterior capsule to total opacification of the lens. Consequently, the effect on vision, course of treatment and prognosis may also be widely variable.
The causes of infantile cataracts have been the source of much speculation and research. Making a distinction between unilateral and bilateral cataracts may be useful when considering etiology.
The majority of bilateral congenital or infantile cataracts not associated with a syndrome have no identifiable cause. Genetic mutation is likely the most common cause. Over fifteen genes involved in cataract formation have been identified, and the inheritance is most often autosomal dominant although it can be X-linked or autosomal recessive. Within the same pedigree, there can be considerable morphologic variation.
Systemic associations include metabolic disorders such as galactosemia, Wilson disease, hypocalcemia and diabetes. Cataracts may be a part of a number of syndromes, the most common being trisomy 21. Intrauterine infections including rubella, herpes simplex, toxoplasmosis, varicella and syphilis are another cause.
In contrast, most unilateral cataracts are not inherited or associated with a systemic disease and are of unknown etiology although they do not rule out the possibility of an associated systemic disease. They are usually the result of local dysgenesis and may be associated with other ocular dysgenesis such as persistent fetal vasculature (PFV), posterior lenticonus or lentiglobus.
Trauma is a known cause of pediatric cataracts. If there is no known history of trauma to explain an acquired cataract in this age group, investigation must be considered in children who present with other signs suggestive of child abuse.
Regardless of the etiology, prompt treatment of visually significant cataracts is necessary to allow proper development of vision.
In many cases of congenital cataracts, there is a family history. History of prenatal and pregnancy history can also provide clues.
Cataracts present as an opacity in the lens which run a spectrum from easily visible in the undilated state and apparent to the parents or pediatrician, to much more subtle changes requiring dilation and careful examination with a slit lamp. The red reflex is an extremely useful part of the exam giving an estimate of size and location within the visual axis, even in an uncooperative child.
Cataracts are classified according to their morphological appearance and location; however, making the diagnosis of a specific type of cataract can be difficult if it spreads to involve multiple layers, obscuring the original opacity.
Cataracts may be a part of another disease or syndrome, and are sometimes the initial finding that leads to the diagnosis. A cataract may be accompanied by additional noticeable ocular abnormalities such as microcornea, megalocornea, coloboma of the iris, aniridia, and zonular dehiscence.
Often an infant with mild cataracts appears asymptomatic, delaying the diagnosis for years. At other times, lack of reaction to light, strabismus, a failure to notice toys and faces or an apparent delay in development become the cause of concern. Mild cataracts may cause photophobia only in bright lights. Dense cataracts also may be discovered if they lead to the development of sensory nystagmus.
For unilateral cataracts in an otherwise healthy child, an extensive workup is not necessary. The most critical part of the workup is a thorough ophthalmologic exam including slit lamp examination of both eyes, checking intraocular pressure, and an ultrasound of the posterior pole if not visible. If the exam reveals the classic appearance of a specific diagnosis such as persistent fetal vasculature (PFV) or posterior lenticonus, no further evaluation is necessary.
The first step in the workup of bilateral cataracts should be a family history including examination of family members. If there is a clear autosomal dominant pattern and the child is healthy, further evaluation is not necessary. In cases without clear family history, a thorough pediatric and developmental exam should be performed. Recommended lab workup includes TORCH titers, VDRL, serum calcium and phosphorus levels and urine for reducing substance. Additional systemic workup should be done in coordination with the pediatrician. Dysmorphic features may suggest the need for involvement of a geneticist.
For bilateral cataracts without a family history, the recommended workup includes a urine test for reducing sugars, TORCH (toxoplasmosis, rubella, cytomegalovirus, varicella) screening, a Venereal Disease Research Laboratory (VDRL) test for syphilis, and a blood test for calcium, phosphorus, glucose, and galactokinase levels. Dysmorphic features may suggest the need for involvement of a geneticist.
The differential diagnosis for leukocoria or white pupil includes retinoblastoma, PFV, retinopathy of prematurity, chorioretinal colobomas, toxocariasis, Coats disease, vitreous hemorrhage and other retinal tumors. These can be distinguished by a complete exam of the anterior and posterior segment, often including ultrasound.
Management of a cataract in a child is different from adults because of the anatomically younger ocular tissues, continuous ocular growth and other associated structural anomalies. Management can be challenging for a surgeon intra-operatively as well as post-operatively because of potential immediate and long term complications and the necessary long term follow up required for adequate management of associated amblyopia. Not all pediatric cataracts require surgery. A small, partial or paracentral cataract can be managed by observation. Pharmacologic pupillary dilation with phenylephrine or tropicamide can be helpful. Dilation with atropine should be avoided as it is amblyogenic due to the cycloplegia. Part-time occlusion may be necessary in unilateral or asymmetric cases that develop or are at risk for amblyopia. These techniques may at least delay the need for surgery until a point when eye growth has stabilized and an IOL can be implanted with less refractive uncertainty. Because of the unpredictability in the progression of partial cataracts, these patients should be carefully monitored and if significant amblyopia develops and is unresponsive to treatment, surgical intervention should be performed.
Visual assesment-Age appropriate visual acuity testing to assess visual function helps establish the significance of the lens opacification on visual development and amblyopia.
- In preverbal children- assessment of ability to fixate and follow light or objects, response to optokinetic nystagmus (OKN) drum rotation, preferential looking test such as teller’s acuity card, patterned visual evoked potential (VEP), resistance to occlusion of either eye
- In verbal children- optotypes charts such as Allen pictures, LEA symbols
Evaluation of strabismus and nystagmus- Strabismus and nystagmus are noted in wide of congenital cataracts and gives a clue about amblyopia. Presence of amblyopia emphasizes the visual deprivation and significance of the cataract and suggests prompt surgery, ideally prior to onset of nystagmus.
Anterior and posterior segment examination-
- Examination with hand held slit-lamp, especially in infants
- Examination under anesthesia (EUA) is often required
- Measurement of corneal diameter
- Measurement of intraocular pressure
- Dilated fundus examination to look for persistant fetal vasculature (PFV /PHPV) or any other posterior abnormalities
- B-scan ultrasound if fundus is not visible. Ultrasound helps to rule out PFV, retinal detachment, retinoblastoma or fundal coloboma
- Measurement of axial length and anterior chamber depth (ACD) using A-scan ultrasound
- Keratometry (details as described below)
Biometry and IOL power calculation[edit | edit source]
Due to the continuous growth of the eyes after surgery and the difficulty in obtaining parameters required for IOL calculation in younger children, IOL power calculations are a challenging task in pediatric age group. Accurate measurement of all the parameters for IOL calculation can often only be obtained when a child is sedated or anaesthesized with general anaesthesia. Full sedation during an EUA allows for a thorough exam, including gonioscopy, corneal diameter measurement, retinoscopy, etc.
- Axial length (AL)-Axial length at birth is 17–17.5 mm approximately. It increases rapidly in the first 6 months (0.46 mm/month), then has a relatively slower (infantile phase) growth (0.15 mm/month) until 18 months, followed by a slow (juvenile phase) growth (0.10 mm/month). It can be estimated with both immersion A‑scan and indentation A‑scan.
- Keratometry - Keratometry values are obtained using a keratometer. Corneal curvature steeply reduces in the first 6 months (−0.40 D/ month), −0.14 D/month in the next 6 months, and − 0.08 D/month in the second year, reaching the adult range at about 3 years of age.
Optical biometer- can be used to calculate AL and keratometry in older children.
- IOL power calculation- The IOL power depends on various factors which include the age of presentation, morphology of cataract, visual acuity at presentation, time of development of cataract (congenital/developmental), biometry at presentation, unilateral or bilateral cataract, and refractive status of the fellow eye. IOL can be implanted in eyes with AL >17 mm and corneal diameter >10 mm. As the eyes grow, a myopic shift is expected. To compensate for this change, a goal for the immediate post operative period of hyperopia is desired.
Methods commonly used to undercorrect the IOL power-
- According to Dahan and Drusedau undercorrection of 20% in children <2 years and 10% in children between 2 and 8 years
- Prost suggested 20% undercorrection between 1 and 2 years of age, 15% undercorrection between 2 and 4 years, and 10% between 4 and 8 years of age.
- Enyedi suggested postoperative target refraction to be used for IOL power calculation according to age (age + postoperative refraction = 7)
Intraoperative aphakic refraction or aberrometry can also be used to calculate the IOL power. The IOL formulae – SRK/T and Holladay 2 have shown to have least predictive errors.
Apart from routine blood check up for anaesthetic and operative purposes other tests are specific and chosen according to history and morphology of cataract. A thorough history of prenatal fevers or rashes in mother helps provide information about intrauterine infectious causes. Other important elements in the history include consumption of any drugs or alcohol, trauma during delivery, preterm delivery (retinopathy of prematurity), failure to thrive, and vomiting (galactosemia). Various laboratory tests in bilateral cataract include:
- Blood sugars
- TORCH titers
- Venereal Disease Research Laboratory (VDRL) test
- Red cell galactokinase
- Serum calcium and phosphorus
- Urine analysis for reducing substances and amino acids
- Newer tests- DNA sequencing technologies, so-called Next Generation Sequencing (NGS) are not performed commonly but are seen as a future testing to improve the diagnosis of congenital cataract especially for genetically heterogeneous conditions.
A unilateral cataract does not typically require extensive diagnostic evaluation, as most of them are isolated, non hereditary with no systemic and genetic abnormality.
General systemic evaluation
This is done by a pediatrician to rule out any systemic associations of cataract.
Indications for visually insignificant cataract are as follows:
- Cataract < 3mm in diameter
- Peripheral or paracentral cataract not obscuring the visual axis
- Blue-dot cataract which is not afftecting the vision
- Presence of good red reflex viewed with direct ophthalmoscope or retinoscope
- Absence of strabismus or nystagmus
Non-surgical management options include:
- Observation with careful regular monitoring to look for any change or progression in cataract and/or development of amblyopia. If either occurs, treatment is recommended.
- Pharmacologic pupillary dilation can be used to increase the pupil size and allow the child to see through a clear portion of the lens. Cycloplegic drops should be avoided as they can cause loss of accommodation and can lead to amblyopia by themselves.
- Occlusion of the other eye is useful in case of unilateral cataract, to prevent amblyopia until surgery is completed.
Indication for surgery
- Any cataract that is visually significant: >3mm central opacity, centrally obscuring posterior pole , with strabismus or nystagmus
Timing of surgery
- Unilateral cataracts should be operated on as early as possible between 4- 6 weeks of age. Operating a child before 4 weeks increases the risk of complications of general anaesthesia and increases the risk of aphakic glaucoma and operating after 6 weeks increases the risk of amblyopia.
- Bilateral cataracts should be operated by 6-8 weeks of age- each eye one week apart. If the child is systemically a high risk case for general anaesthesia, both eyes can be simultaneously operated by an experienced surgeon with a completely different set of instruments for each eye.
The choice of anaesthesia depends upon age and systemic condition of patient. Risk and benefits of general anaeshthesia has to be considered. Infants less than 1 month have immature organ systems and thermoregulation system and are at greater risk for post-operative apnea. For older children, of more than 10 years age, who can understand and cooperate for local anaesthesia, peribulbar block with or without sedation can be used.
Considerations for treatment
Decision about surgery depends upon age of patient at presentation, extent of opacity and associated conditions.
If child is <1 year of age, the surgical approach is typically lensectomy (pars plana or limbal) with primary posterior capsulotomy and anterior vitrectomy, leaving anterior and posterior capsular rim (for a secondary IOL at a later point), optic rehabilitation using aphakic glasses or contact lenses and amblyopia and strabismus management. In older children, a lensectomy (with or without primary posterior capsulotomy and anterior vitrectomy) and potentially a lens implant can be considered. Management always includes amblyopia management and careful refractions for bifocals (even with IOL implantation). In children older than 5-7, a posterior capsulotomy may not be necessary at the time of the initial surgery if they are able to sit at the slit lamp for a Yag laser, if needed later after cataract extraction.
Surgical steps and consideration
There are numerous important differences between pediatric and adults eyes to consider during surgery. Pediatric eyes have lower corneal and scleral rigidity, very elastic anterior capsules, soft lenses, and well‑formed vitreous. These factors play a role intraoperatively and warrant slight modifications in various steps of cataract surgery.
- Incision – superior incision is preferred as it is covered by the lid and protected by Bell’s phenomenon in case of any trauma, as children are more prone to trauma than adults. Either scleral or corneal incisions can be made, as the difference in post-operative astigmatism is insignificant. A paracentesis should also be made to aid in cataract extraction and cortex removal. In cases of infants less than 7 months of age who are left aphakic, lens aspiration can be done from paracenteses only.
- Anterior capsule management- An optimal anterior capsulotomy is important to facilitate intraocular lens (IOL) placement in the capsular bag. An ideal anterior capsulotomy should be a continuous curvilinear capsulorrhexis with a round, regular shape that is of adequate size (approximately 5.5-6mm). Capsules of pediatric patients are elastic and hence it is challenging to make a continuous curvilinear capsulorrhexis. Trypan blue (0.06%) can be used to stain the anterior capsule for good visualization. Trypan also reduces the elasticity of capsule which aids in making a continuous capsulotomy. Anterior capsulorhexis is completed with the help of a cystitome or bent needles, and forceps (Utrata, intravitreal 23G, or intraocular capsulorrhexis). Other methods of performing anterior capsulotomy in pediatric population are vitrectorhexis with low aspiration and high cut rate with the vitrectomy cutter. This technique is especially useful if IOL placement is not planned. The disadvantage of vitrectorhexis is that the irregular edges created by this method can lead to unanticipated tears of the anterior capsule. Radio-frequency diathermy and Fugo plasma blade have been also advocated for anterior capsulorhexis but have same disadvantages as vitrectorhexis. Femtosecond laser can be employed for both anterior and posterior capsulotomy with good precision and decreased corneal endothelial damage. However, it is not cost-effective and may have micro-irregular edges. Studies that analyzed pediatric anterior capsulotomy techniques in the porcine model found that manual capsulorhexis produced the most extensible capsulotomy with the most regular and stable edge. Precision pulse capsulotomy has also been shown to create well-centered and strong capsulotomies in a pediatric age-group.
- Hydrodissection – should be minimal, gentle and in all quadrants. Hydrodissection was found in a randomized-controlled trial to decrease lens removal time and fluid volume used. Inadvertent excessive hydrodissection in patients with pre-existing posterior capsular rupture can lead to drop of lens matter in vitreous cavity.
- Lens aspiration - the lens in pediatric cataract is generally soft. Gentle lens aspiration can be performed using automated lensectomy techniques or manually with a Simcoe cannula or irrigation-aspiration cannula from a limbal approach. A pars plana approach is also acceptable, especially when IOL implantation is not planned.
- Posterior capsulotomy - performed in children less than 6 years of age to prevent post operative visual axis opacification (VAO). It can also be performed in children older than 6 years (with developmental delay or with nystagmus) who may not cooperate for laser capsulotomy at a slit lamp later. Techniques to perform posterior capsulotomy are similar to anterior capsulotomy including capsulorhexis using forceps, vitrectorhexis, radio-frequency endodiathermy and femtosecond laser assisted capsulotomy. The size of the posterior capsulotomy is made 1-2mm smaller than the anterior capsulotomy. Posterior capsulotomy can be performed from a limbal approach or from a pars plana approach.
- Anterior vitrectomy - performed when there is a break in anterior vitreous face due to posterior capsulotomy or in attempts to prevent VAO by breaking the scaffold for proliferating lens epithelial cells (LECs) and metaplastic pigment cells. Additionally, in younger children, post-operative inflammation causes a fibrous reactionary membrane over an intact anterior vitreous face, leading to VAO. A thorough anterior vitrectomy is often done in children of less than 6 years of age following posterior capsulotomy. Like posterior capsulotomy, vitrectomy can be performed through anterior route or pars plana route depending on surgeon’s preference.
- Lens implantation- IOL implantation is the primary mode of visual rehabilitation in children more than 1 year of age. In younger children, especially in infants it is almost impossible to predict the adequate IOL power because of their fast growing eyes and change in parameters. In a multicenter, randomized clinical trial done by The Infant Aphakic Treatment study (IATS), it was found that compared to infants with no IOL after cataract removal, patients treated with primary IOL implantation prior to 6 months of age had more adverse events and required more additional intraocular surgeries over the first five years following surgery for unilateral congenital cataract, with most occurring during the first postoperative year. The Toddler Aphakia and Pseudophakia Study (TAPS) found that IOL implantation was relatively safe in children older than 6 months and younger than 2 years. IOL placement in the bag is most preferred site, though the IOL can be placed in the ciliary sulcus when posterior capsular support is inadequate. Infants who are left aphakic are planned for secondary IOL later and until that time visually rehabilitated with glasses or a contact lens.
- Preferred IOL material- Acrylic hydrophobic foldable IOLs have unique benefits in children due to increased biocompatibility. There is less chance of postoperative inflammation and posterior capsular opacification with this type of IOL. Due to its foldability, it can be inserted through a smaller incision than polymethylmethacrylate (PMMA) lenses. PMMA lenses also have good biocompatibility but are not foldable and large incisions are required for insertion. In terms of safety profiles, studies have shown that primary implantation of PMMA in pediatric cataract surgery is comparable to acrylic IOLs. Due to their low expense, PMMA lenses are commonly used in developing countries. Many PMMA lenses are also useful for in-sulcus implantation or for optic capture with haptic in sulcus when thin capsule rim cannot support the optic of the lens. IATS randomized children 1-6 months of age with a unilateral cataract to primary IOL implantation vs aphakia. There was no significant difference between visual acuity of operated eyes in children who underwent primary IOL implantation and those left aphakic. However, there were significantly more adverse events and additional intraoperative procedures in the IOL group. The refractive goal of cataract surgery in children is complicated and involves many factors. Most surgeons will chose to make the child hyperopic (as to avoid high myopia in adulthood) but there is currently no agreed upon standard. Aphakic and pseudophakic children will need bifocal glasses for the rest of their lives.
- Closure of wound- After completion of surgery and thorough washing of viscoelastic from anterior chamber, the wounds are sutured using 10-0 suture, often nylon or vicryl. Vicryl has the advantage of dissolving and not requiring surgical removal, but can be more inflammatory.
- Wound leakage
- Iris or vitreous incarceration in wound
- lOL/iris capture
- Post-operative inflammation- Fibrinous or exudative postoperative uveitis is common due to increased tissue reactivity of these eyes. Inflammation can be treated with topical and oral steroids. The visual axis may require clearing with the Nd:YAG laser or vitrectomy/membranectomy. Tissue plasminogen activator has been recommended in cases of severe fibrin deposition on the IOL surface, threatening visual rehabilitation.
- Post operative increased IOP
- Vitreous haemorrhage
- Retinal haemorrage due to low IOP
- Retinal detachment
- Post-operative endophthalmitis
- Careful surgical technique can reduce early postoperative complications such as wound leak, iris to the wound and vitreous to the wound. Retinal hemorrhages can occur, probably as a result of leaving the intraocular pressure low at the end of surgery. Iris capture of the IOL optic can cause discomfort and disfigure the pupil. This is caused by iris scarring to the anterior capsule and the risk can be reduced by careful placement of the lens at the time of surgery. Cystoid macular edema in children is not common as with adults, but can be seen on rare occasions.
Secondary Opacification/ Visual axis opacification
Opacification of the visual axis is the most common complication of cataract surgery in children. This is a serious complication because it can lead to amblyopia. A posterior capsulorhexis and anterior vitrectomy as previously discussed is one way to avoid this. An IOL can prevent the formation of a Sommering’s ring, but it is also easier for the lens epithelial cells to migrate to the center of the pupil. Others have suggested captruring the optic by placing the haptics in the bag and pushing the optic through the posterior capsularhexis may prevent opacification. If opacification occurs, a Nd:YAG laser capsulotomy can be attempted. In the younger age groups, general anesthesia is often necessary and a surgical membranectomy may be indicated if the Nd:YAG laser is not effective or available.
Secondary glaucoma is the most sight threatening complication of pediatric cataract surgery. Approximately 20% of children will develop glaucoma following cataract surgery. Open-angle glaucoma can develop months to years after the surgery. The two most significant risk factors for development of glaucoma following pediatric cataract surgery are young age of surgery and microphthalmia. Angle-closure glaucoma can result from anterior synechiae leading to pupillary block, which can be treated with a peripheral iridectomy. Some eyes with secondary glaucoma can be controlled with topical medication, but many cases will require additional surgical intervention. Children who have had cataract surgery require lifelong monitoring for the development of glaucoma. The incidence of secondary glaucoma is found to be higher in aphakic patients, history of surgery within the first month of life, children with family history of aphakic glaucoma, persistent fetal vasculature syndrome, and nuclear cataract. The risk of developing glaucoma is life-long; hence, regular monitoring of IOP is necessary
The lifetime risk of retinal detachment after cataract surgery in pediatric patients is increased. Risk factors for retinal detachment are PFV, high myopia and repeated surgeries. Life-long monitoring with regular dilated fundus examinations is required.
Amblyopia, strabismus, and nystagmus which may have developed prior to cataract surgery may continue despite removal of the cataract(s) and must also be addressed.
In the postoperative period, it is important to prevent and keep under check any significant inflammatory reaction. The prolonged use of local steroids, nonsteroidal anti-inflammatory agents, and atropine are recommended for this purpose. Systemic steroids are used by some to prevent or treat secondary membranes, but often are not successful resulting in the need for Nd:YAG laser or surgery. The eye must be monitored regularly for the development of a secondary cataract or any other early or delayed problem.
Unlike in adults, the management of a pediatric patient is not complete when the post-operative period is over. In some ways, the more difficult and important part of management is still ahead. Neglecting the treatment and prevention of amblyopia or not giving proper refractive correction is leaving the work half done. Lifelong careful follow-up is essential for all pediatric cataract cases.
Management of pediatric aphakia depends on the age of the child, the family situation and whether there are abnormalities of other ocular structures such as the cornea and the development of the child. For infants, aphakic contact lenses are the treatment of choice for those infants who do not receive an IOL.
Aphakic spectacles are an option in children who are contact lens intolerant or as a backup to contact lenses in bilateral aphakes. Spectacles are not ideally used for unilateral aphakes because they disrupt binocular fusion. However, for a child without binocular potential or strabismus, unilateral aphakic spectacles in combination with patching can be used. A high refractive index lens can diminish the weight and size of aphakic spectacles making them better tolerated.
Amblyopia treatment must be initiated as soon as possible. For amblyopia treatment to be effective, the amblyopic eye must have not only a clear visual axis, but also the proper corrective lenses to provide the retina with a clear image. In unilateral cases, the amount of patching required depends on the age at which the visual axis was cleared. Patient and family education about amblyopia and treatment strategies is essential.
The course and prognosis of pediatric cataracts is highly variable. The likelihood and rate of progression is very difficult to predict. In addition, the presence of other ocular or systemic abnormalities contribute to the variable outcome.
The most serious complication of congenital cataracts is permanent visual impairment. When the visual axis is blocked by a lens opacity during the sensitive period of visual development, irreversible amblyopia and permanent nystagmus may result. The first two months of life are the most critical for visual development; amblyopia resulting from visual deprivation after the age of 2 to 3 months can often be reversible to some degree. Visual development continues until at least 7 years of age.
Unilateral cataracts carry a less favorable prognosis than bilateral cataracts. Even a minimal opacity can create significant amblyopia. A child with a unilateral cataract is also at greater risk for anisometropia, which can complicate the picture.
In addition to clearing the visual axis by appropriate surgical technique, proper optical correction in the form of aphakic glasses, contact lenses or intraocular lens implants and treatment for amblyopia is essential for good visual development. This requires an ongoing commitment from both the ophthalmologist and family of the infant.
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- Infant Aphakia Treatment Study Group, Lambert SR, Buckley EG, Drews-Botsch C, Dubois L, Hartmann EE, Lynn MJ, Plager DA, Wilson ME. A randomized clinical trial clinical trial comparing contact lens with intraocular lens correction of monocular aphakia during infancy: grating acuity and adverse events at age 1 year. Arch Ophthalmol. 2010. Jul:128:810-8.
- Glaucoma-Related Adverse Events in the First 5 Years After Unilateral Cataract Removal in the Infant Aphakia Treatment Study.https://www.ncbi.nlm.nih.gov/pubmed/25996491