|Ahead of print publication
Childhood glaucoma – A review of basics
Sucheta Parija, Saswati Sen
Department of Ophthalmology, All India Institute of Medical Sciences, Bhubaneswar, Odisha, India
|Date of Submission||22-Jan-2020|
|Date of Decision||08-Jul-2020|
|Date of Acceptance||27-Jul-2020|
Department of Ophthalmology, All India Institute of Medical Sciences, Bhubaneswar - 751 019, Odisha
Source of Support: None, Conflict of Interest: None
Childhood glaucoma is a rare disease associated with significant pressure related visual loss and ocular comorbidity. It consists of a heterogeneous group of diseases which can be classified based on etiopathogenesis and morphology. Global incidence of childhood glaucoma accounts for 2%–6% of blindness in children. Although glaucoma in children is rare compared to adults yet the burden of blindness is significant. Hence, early diagnosis and treatment is of paramount importance to save vision. The classical triad of signs is blepharospasm, epiphora, and photophobia which may be missed in the infants unless corneal edema and buphthalmos manifests. Attention to these minute details makes detection of the disease possible even by the primary treating physician. Unlike adult glaucoma, the cupping in these cases is reversible. Therefore, the diagnosis and classification of the disease plays an important role in deciding the treatment protocol. Treatment for childhood glaucoma is primarily surgical management and requires a long-term follow-up. The prognosis is better if the disease is diagnosed and treated earlier. In developing countries delay in diagnosis, availability of limited surgical expertise, frequent follow-up and lifetime rehabilitation adds to the stress on parents and burden to the community. Relevant data regarding congenital glaucoma were researched on by the qualified ophthalmologists through Google Search, Bing, and Opera Mimi search engines from PubMed, Scopus, and Copernicus indexed journals. Emphasis was given on including hand searched articles after going through the hard copies of certain articles and the appropriate references have been cited in the text. This article highlights the epidemiology, classification, genetics and current management of this disease with emphasis on future strategies and planning to reduce the rate of avoidable blindness in children due to glaucoma.
Keywords: Avoidable blindness, blepharospasm, buphthalmos, congenital glaucoma, goniotomy
| Introduction|| |
Childhood glaucoma is a rare disease associated with significant pressure-related visual loss and ocular comorbidity. It consists of a heterogeneous group of diseases which can be classified based on etiopathogenesis and morphology. Global incidence of childhood glaucoma is around 1 in 10000 in many populations worldwide. The incidence of primary congenital glaucoma (PCG) is 10 times higher in communities with high consanguinity. Children usually present at different stages of the disease and mostly in the advance stage requiring multiple procedures and long-term treatment. Although the incidence of glaucoma in children is much less in comparison to adults but the burden of visual impairment and blindness is significant and irreversible. Rehabilitation in terms of correction of refractive errors and treatment of amblyopia with long-term follow-up is essential. Thus, the economic, psychological, and social burden has immense impact not only on the parents, the community but also on the nation. The present line of management focuses on early diagnosis and treatment with long-term rehabilitation. Future horizon lies in detecting the causative gene in PCG during premarital screening in recessive diseases, genetic counseling to potential couples that will help to eradicate the disease in future.
This review article aims to provide an overview on the epidemiology, the recent classification, genetics, and advances in the techniques of surgeries and future strategies to combat childhood blindness due to glaucoma in children.
| Methods|| |
The literature review was conducted to find all the papers using the available online biomedical search engines PubMed, Medline, EMBASE, and Cochrane library. The search was made using the following terms: Childhood AND Pediatric AND Glaucoma AND (Morphology OR Clinical presentation OR Classification OR Surgery OR Antiglaucoma drugs OR Visual outcome OR Complications OR Rehabilitation) AND Blindness AND Strategies. Both the authors identified all the articles and the relevant articles that were based on childhood glaucoma were included for review. The search was made on all the English articles from 1989 to 2019, including review articles, systemic review, and meta-analysis and original articles.
| Epidemiology|| |
The incidence of PCG varies across various populations and ethnicity. The overall incidence of PCG ranges from 1: 2500 to 1: 6800 in different populations. The incidence of childhood glaucoma in a population study in Minnesota, USA, was 2.29/100,000 or 1/43 575 residents younger than 20 years. In Germany, history-based prevalence of juvenile glaucoma was 0.01%. The prevalence was an order of magnitude higher (0.16%) between the age of 18 and 40 years, and two orders of magnitude higher at later ages (1.98%). In a study conducted in North-East India, the incidence of PCG was found to be 1.2% and secondary glaucoma (SG) was 3.2%. A study in Southern India, reported the incidence to be 1 in 3300. Surgery for congenital cataract is found to be an important factor in the development of aphakic glaucoma in children. Consanguinity plays an important factor in cases of PCG as compared to secondary cases.
| Classification|| |
Childhood glaucoma has been classified under different classification systems in the past; yet none are widely accepted now.
From anatomical point of view, Hoskin's classification describes the site of dysgenesis which results in glaucoma. It divides PCG into three groups of trabeculodysgenesis, iridotrabeculodysgenesis (stromal defects, anomalous iris vessels, structural defect), and corneotrabeculodysgenesis (anomalies, such as Axenfeld's, Rieger's, and Peters).
The childhood glaucoma research network (CGRN) classification system is the first international consensus classification for childhood glaucoma. The clinicians can utilize it as a logical diagnostic guideline that will help them to use it systematically and reproducibly categorize childhood glaucoma patients. At the Ninth World Glaucoma Association (WGA) Consensus, this system got its recognition and has been adopted by the American Board of Ophthalmology for research. CGRN definition of glaucoma and glaucoma suspects is largely applicable in the present day scenario as described in [Table 1]. After the diagnosis of glaucoma, further categorization can be done as per the CGRN as discussed below and in [Figure 1].
|Table 1: Classification of childhood glaucoma and glaucoma suspect as per Childhood Glaucoma Research Network definition|
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|Figure 1: Guidelines for decision making for the cause of glaucoma as per the childhood glaucoma research network classification|
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Primary childhood glaucoma
This consists of both PCG and juvenile open angle glaucoma (JOAG). PCG in children presents early in life and mostly result from an abnormal development of the drainage system.
- PCG-According to the age of presentation, it can be
- Congenital-when the presentation is since birth. The intraocular pressure (IOP) is raised during intrauterine life
- Infantile-when manifestation is before 3 years of age
- Juvenile-where the presentation is between 3 and 16 years of age.
In these cases, there is no congenital abnormality or corneal enlargement but it meets glaucoma criteria as per CGRN.
Secondary childhood glaucoma
These are a group of patients in whom glaucoma is associated with ocular or systemic abnormalities as described in [Table 2].
Childhood glaucoma can be further classified into primary (isolated congenital abnormality of the aqueous outflow) or secondary (abnormality affecting the other regions of the eye) as per the WGA as described in the [Table 3].
| Genetics|| |
The genetics of glaucoma is still at its developing stage and a research area to be developed in future. In case of PCG, most cases are sporadic though familial inheritance is also seen. Inheritance is mostly autosomal recessive. Four identified genetic loci of PCG are GLC3A, GLC3B, GLC3C, and GLC3D; but additional loci are likely to exist. Two main genes associated with PCG have been identified: CYP1B1-cytochrome P450 family 1, subfamily B, polypeptide 1 within the GLC3A locus and LTBP2-latent transforming growth factor beta-binding protein 2 within the GLC3C locus., The developmental glaucoma is caused by multiple genes. The study by Gould et al. reported, some of these genes as PITX2, PITX3, FOXC1, FOXE3, PAX6, LMX1B, and MAF which collectively encode for transcription factors that bind to specific DNA segments and regulate gene expression., In families with unknown etiologies, angiopoietin receptor TEK (tunica interna endothelial cell kinase), also known as Tie2 mutation has been reported.
Most cases of JOAG have an autosomal dominant inheritance pattern, but sporadic cases occasionally occur. JOAG has been linked to mutations in the trabecular meshwork inducible glucocorticoid response/myocilin gene located at the GLC1A locus on chromosomes 1q23.5. In an Indian study by Acharya et al. JOAG is said to be associated with CYP1B1 pathogenic variants alone.
| Pathophysiology|| |
The pathophysiology of congenital glaucoma cases depend upon the time of presentation, type and etiology.
| Primary Associations with Congenital Glaucoma|| |
In most cases of PCG increased resistance to outflow through the trabecular meshwork is caused by a membrane covering the anterior chamber angle and plays a significant role in the pathophysiological mechanism. There is abnormal development of the angle structures derived from the neural crest tissue. Anterior insertion of the iris root along with dysgenesis of the trabecular meshwork (enlarged trabeculae with diminished inter-trabecular spaces) is also seen in these cases., Developmental glaucoma is usually associated with angle anomalies, posterior embryotoxon, and other respective systemic anomalies as in Axenfeld Rieger anomaly, aniridia, Peters plus syndromes, microcornea, and Lowe syndrome. JOAG is classified as a primary open angle glaucoma presenting after the age of 4 years. This is a rare form of pediatric glaucoma inherited as an autosomal dominant trait with a strong family history of glaucoma. The rise in IOP is associated with atrophy of optic nerve head and vision loss.
| Secondary Associations with Congenital Glaucoma|| |
Children are more prone to be affected than adults in steroid-induced, uveitic, or postsurgery-induced glaucoma., The administration of topical steroids specially for vernal conjunctivitis is one of the major cause of steroid-induced glaucoma in children., The proposed mechanism of corticosteroid-induced glaucoma includes morphological and functional changes in the trabecular meshwork system as evidenced by one of the studies. Increase in IOP depends on the type of drug (short or long acting), the dose, the frequency of the administration, and the corticosteroid responsiveness of the patient.
Juvenile idiopathic arthritis, and ANA positive uveitis without evidence of arthritis have more predisposition to develop uveitic glaucoma. A study by Merayo-Lloves et al. found frequency of SG was more in anterior uveitis (67%) compared with posterior uveitis (13%) and pars planitis (4%). The mechanism may be due to the effect of inflammatory cells or due to corticosteroid therapy or a mixed mechanism. Hence, it is important to establish that the patients had normal IOP before the development of uveitis and to maintain normal pressure after the resolution of uveitis.
Children undergoing cataract surgery for congenital cataract are prone to develop glaucoma. I Gawdat et al. found the incidence of glaucoma to be 11.33% following cataract extraction. Further, depending on the lens status, glaucoma may be aphakic or pseudophakic after cataract surgeries. IOP may be raised due to various causes such as intraoperative barotrauma or decreased traction on the zonules post lens removal, postoperative complications such as vitreous loss, contact of the trabecular meshwork with vitreous, lens particles, or inflammatory cells affecting the drainage of aqueous from the angles.
Following trauma and tumors rapid changes in the angle structures causes the development of glaucoma earlier in these cases. Qiao et al. reported that traumatic glaucoma is the second-most common cause of glaucoma in children. It may be associated with angle recession, hyphema, and corneal injuries. Blockage of angle structures by blood or inflammatory debris, and long standing vitreous hemorrhage in trauma and direct invasion of tumor cells in malignancy may cause an increase in the IOP. Other mechanisms that play a role are: melanophagic, hemolytic secondary angle closure, suprachoroidal hemorrhage, iris neovascularization, and choroidal detachment.
| Clinical Presentation|| |
The clinical manifestations and its high degree of variability are determined by the age of onset and magnitude of the elevated IOP. Glaucoma in a neonate usually presents with the classical triad of watering, photophobia or blepharospasm. On examination, the signs of the disease include corneal haze due to increased IOP or due to localized breaks. Haab striae are curvilinear healed breaks in Descemet's membrane. Buphthalmos occurs due to stretching sclera because of elevated IOP prior to the age of 3 years. The thinned sclera often appears blue and leads to high myopia in children [Figure 2]. Corneal scarring and vascularization are seen. Optic disc cupping is seen in many cases. Most normal infants exhibit no apparent cupping.
|Figure 2: A 10-year-old child showing megalocornea and cloudy cornea with intraocular pressure of 24 mmHg and 30 mmHg|
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| Diagnosis|| |
Proper history taking is important regarding the appearance and duration of symptoms. Evaluation under general anaesthesia is generally required. It involves measurement of IOP, anterior chamber examination, optic disc examination, corneal diameter measurement with calipers. IOP measurement in children is a challenge. The current methods are handheld applanation tonometry (Tonopen and Perkins tonometer) and rebound tonometry (i Care). IOP measurement needs to be done immediately post induction of anesthesia to minimize its effect on IOP. The role of pachymetry is still unclear in cases of congenital glaucoma. Central corneal thickness should not be adjusted for IOP as in adults, but taken for overall consideration. Children diagnosed as PCG and JOAG, have thinner cornea while congenital aniridia and post cataract aphakia patients tend to have thicker corneas than normal subjects.
Gonioscopy using a direct goniolens may be normal or reveal trabeculodysgenesis. The main purpose of gonioscopy is to differentiate between primary and SG. Refraction under anaesthesia needs to be done. This facilitates differentiation from axial myopia or astigmatism and also helps to give correction and manage amblyopia if present. Progressive myopia, changes in corneal diameter and axial lengths with borderline IOP and cupping suggests a fluctuating IOP, which needs follow-up to determine the response to treatment.
| Differential Diagnosis|| |
Several diseases may mimic the signs and symptoms of the disease as described in [Table 4].
| Medical Management|| |
Medical treatment of childhood glaucoma is primarily used as an adjunct to surgery. It is helpful in decreasing corneal edema prior to surgery and as an extra tool for lowering IOP in case of partially successful surgical procedures. The drugs commonly used are β-blockers, alpha 2 agonists and carbonic anhydrase inhibitors.
The drug is usually used as a first-line agent in children. It works by decreasing aqueous production from ciliary body. The side-effects are bronchospasm, apnea, and bradycardia. Children are more susceptible than adults to side effects like bronchospasm due to risk of systemic absorption. The use of betaxolol (b1 selective antagonist), timolol 0.25% gel, and timolol 0.1% can help to avoid these side. Topical administration is reported to have caused average decrease of 30.7% in IOP.
Alpha 2 agonists
These drugs are mainly avoided in children. These drugs act by decreasing the aqueous secretion. Several studies on the efficacies of the drug has been reported., There is limited use in children below 2 years of age for the risk of apnea. Brimonidine causes bradycardia, hypotension, hypotonia, and apnea in infants and severe lethargy in toddlers.
These groups of drugs increase the uveoscleral outflow. Latanoprost has showed to have achieved >15% reduction in IOP (termed as responders) in older children. The side effects are minimal but there is darkening of the iris as seen in adults. A study by Quaranta L et al. reported travoprost to have minimal adverse effects in children and was effective in lowering IOP in selective group of patients.
Carbonic anhydrase inhibitors
They act by suppressing the aqueous production. This drug can be used by both topical and systemic routes. Oral acetazolamide is more effective in lowering IOP and is used at doses of 5 mg/kg/day. They have additive effect with prostaglandins. They also act as good adjunct in postoperatively where the IOP is high with one anti-glaucoma medication. Metabolic acidosis is one of the complications of oral treatment.
Other drugs: pilocarpine has limited use in pediatric patients. Certain osmotic drugs like mannitol can be administered in children with the developmental glaucomas to reduce the IOP before surgery. It can also be given to patients with IOPs that are high even with standard medical therapy.
| Surgical Management|| |
Pediatric glaucoma surgery is challenging because of anatomical variation; difference in tissue behavior and difficulties with postoperative management., Goniotomy and trabeculotomy are the surgery of choice for PCG. The prognosis is best for patients undergoing angle surgery between the ages of 3 and 12 months, with a success rate of 70%–90%. Surgery in these cases can be difficult owing to the distorted angle structures and also poor visualization of the structures. The different surgical techniques are described below and a brief summary of few studies on different surgical techniques is summarized in [Table 5].
| Goniotomy|| |
Goniotomy is the first procedure of choice but requires a clear cornea as a prerequisite for safe surgery. This procedure includes insertion of a blade through the trabecular meshwork into the anterior chamber. Sectioning of the abnormal trabecular tissue during goniotomy allows repositioning of the angle structures and hence the appearance of the angular recess. A study in East Africa showed improvement in 22 out of 26 children following goniotomy. Some studies have reported occurrence of urrets zavalia syndrome following goniotomy. This is a condition where the pupil remains fixed and dilated after any ophthalmic procedure and is usually seen in patients post penetrating keratoplasty. Although the pathophysiology is not established, a sudden rise in IOP along with ischemia of iris is said to play a role.
| Trabeculotomy|| |
This is a procedure of choice in cloudy cornea. It involves altering the trabecular meshwork. Trabeculotome is inserted beneath a flap through the Schlemm's canal into the anterior chamber. Then the instrument is rotated into the anterior chamber after tearing the trabecular meshwork. A 360 degrees trabeculotomy has better 1 year IOP control than the conventional trabeculotomy., It is better in cases where visualization of anterior chamber structures is hampered by cloudy cornea.
| Trabeculectomy|| |
Trabeculectomy remains the gold standard surgical technique for glaucoma till date. Here a full thickness scleral flap is made and conjunctiva covers the flap making a water tight filtration. The mean IOP reduced from 35 ± 10 to 13 ± 2.5 mmHg after trabeculectomy in a study in JOAG patients. Due to aggressive wound healing, thin and elastic sclera in children the success rate is 60%–70%. The use of antimetabolites such as mitomycin-c and 5-fluorouracil is said to have better results according to some studies., Bleb related endophthalmitis is a dreaded complication reported in 7%–14% of cases.
| Drainage Devices|| |
Aqueous drainage devices are reported with a higher success rate compared to trabeculectomy. The glaucoma drainage devices are basically of two types. These are characterized as open-tube (nonrestrictive) devices such as the Molteno and Baerveldt implants, or valved (flow-restrictive) devices such as Krupin implant or Ahmed glaucoma valve. These shunts are implanted after making sclera flaps and introducing tube into the anterior chamber to drain the aqueous and maintain the IOP. The bleb formed in these cases is much posterior as compared to the traditional blebs and are supposed to cause less infection. Success rates vary with different tube shunts and the age of patient undergoing surgery. Complications include anterior migration of the tube shunt with resultant corneal damage, tube blockage, tube erosion with resultant endophthalmitis, cataract, motility disturbances, bleb encapsulation with elevated IOP, and pupil distortion.
| Combined Trabeculotomy and Trabeculectomy|| |
This procedure is the first line of surgical procedure in specific centers for PCG patients. Trabeculotomy can be combined with goniotomy and trabeculotomy for better results. Advantage of combination procedures is most probably because of the dual outflow mechanism that acts to control the IOP. The debate that trab-trab is a superior procedure than either trabeculotomy or trabeculectomy performed alone has been clarified by Dietlein et al. Although there was a higher success rate of the combined procedure at 6 and 60 months of follow-up, but the survival analysis failed to demonstrate significant difference in the surgical outcome between the three procedures.
| Cyclodestructive Procedures|| |
Cyclodestructive procedures are an option for difficult to treat cases. Cyclophotocoagulation is an effective method in children with glaucoma uncontrolled with medical or surgical therapy. Both transscleral and endocyclophotocoagulation were found to be effective in lowering IOP. These procedures lower IOP by causing areas of the ciliary body to atrophy, resulting in less aqueous production. Cyclotherapy has a risk of ocular hypotony and is recommended in eyes with sustained high IOP, and cosmetically disfiguring eyes with low visual potential.
| Prognosis in Childhood Glaucoma|| |
Prognosis depends on several factors the interplay of which results in the final visual outcome. The decision making factors are severity of the disease, the age of presentation, age of surgical intervention, number of surgical procedures, IOP control and its variation, early rehabilitation, and amblyopia therapy.
| What Have we Achieved till now and What Next?|| |
First, there is a census acceptable and standardization of the newer classification for childhood glaucoma. CGRN classification system will help in better patient categorization and will help in a uniform standardization of communication leading to future research on childhood glaucoma.
Second, in recent decades the surgical innovations for childhood glaucoma were few as very few surgeries were undertaken even in specialized centers. The study published in 2010 by Sarkisian on circumferential illuminated catheter for trabeculotomy has aroused the interest among the surgeons. El Sayed Y et al. in 2017. reported the results of the randomized study comparing the 360° illuminated catheter-assisted trabeculotomy with rigid probe trabeculotomy. Comparing the control of IOP levels in both the groups was not significant but the rate of re-surgery was less and survival period more in the illuminated catheter group.
Third, the question arises do we need a nationwide screening program for detecting childhood glaucoma looking into the issues of consanguinity, irrational use of steroids, and late management of trauma.
Future horizons are increasing awareness, establishing strong networking system for early detection and referral, accessibility and follow-up issues to be addressed. Premarital screening in recessive individuals and genetic counseling and further helps to control the disease at the early stage.
| Conclusion|| |
Glaucoma in children demands the treating ophthalmologists to be infallible. Key to the management of congenital glaucoma is early diagnosis and surgical management to prevent irreversible damage and blindness. In children early visual rehabilitation and amblyopia therapy plays a crucial role. Low incidence, difficult surgical technique makes the diagnosis and treatment a dilemma for the ophthalmologist. Hence, meticulous decision making regarding medical and surgical management should be done for better results.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]