A Review of Pediatric Glaucoma V745 Ocular Disease II Brett King, OD Indiana University School of Optometry. Brett Briggs

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1 A Review of Pediatric Glaucoma V745 Ocular Disease II Brett King, OD Indiana University School of Optometry Brett Briggs

2 A REVIEW OF PEDIATRIC GLAUCOMA 1 Glaucoma is defined as a family of diseases characterized by optic neuropathy as a result of elevated intraocular pressure (IOP) that occurs when aqueous production exceeds outflow. This process irreversibly damages the optic nerve. The clinician must understand that glaucoma is similar to cancer in that it has a wide array of etiologies, risk factors, and classifications. In general, glaucomatous neuropathies result in progressive visual field loss and ultimately blindness, if not successfully managed. Patient should be reminded that there is currently no cure for glaucoma, only effective disease management designed to slow or halt progression. 1 Early in life, primary infantile glaucoma is mainly due to poorly developed structures in the anterior chamber and iridocorneal angle from birth, or secondary to syndromes or postcataract surgery. 1 Any of these circumstances can cause a drainage deficiency in the aqueous outflow pathway and result in a subsequent rise in IOP. 2 There are several classifications of pediatric glaucoma centered on the age of onset. Congenital or neonatal glaucoma refers to when the condition is purely developmental and present at birth. Infantile glaucoma transpires from birth until three years of life. Lastly, juvenile glaucoma follows after the age of three into teenage years and is typically more indolent. 3 For the scope of this paper, we will be focusing on congenital and infantile glaucoma, because they are very closely affiliated, other than the precise time of onset. Pediatric glaucoma presents in the first years of life; about 60% of patients are diagnosed before six months of age, and 80% are diagnosed by the end of their first year. 3 Diagnosing and managing glaucoma in this population produces extraordinary clinical hurdles. Pediatric patients are characteristically not the most cooperative, and they cannot communicate on the same level as a more mature patient. Examination under anesthesia is commonplace for an initial exam with young patients and occasionally necessary for return visits. Great strides have been made in ascertaining the disease process, and therefore the treatment. Nonetheless, poor outcomes still often occur. The majority of patients require a challenging surgery because most patients IOPs do not drop adequately under pharmaceutical management alone for extended

3 A REVIEW OF PEDIATRIC GLAUCOMA 2 periods. Poor visual outcomes, including enucleation, are still too common. 4 Males are 50% more likely than females to develop infantile glaucoma in the United States and Europe. 5 On the low end of incidence, it occurs in about 1 out of 30,000 births in Northern Ireland and can be as high as 1 out of 1,250 in Romanian gypsies. This wide variation in incidence suggests a strong genomic predisposition. 1 A family history is present in 10 40% of cases and gene studies have recognized anomalous loci with an autosomal recessive inheritance pattern on gene GLC3 have as responsible. 6 Aqueous humor is a thin, clear fluid which plays a vital role in nourishing the avascular structures of the eye. The production process, pathway, and eventual outflow are paramount to understanding glaucoma. Within the eye, aqueous provides biological support to the posterior and anterior chambers, while maintaining optical clarity required for vision. 7 This is commonly referred to as the blood-aqueous barrier. The non-pigmented ciliary epithelium produces aqueous humor within the processes of the ciliary body. Once produced, the aqueous humor flows through the posterior chamber, around the crystalline lens, and through the pupil into the anterior chamber. Once in the anterior chamber, aqueous humor passively exits the eye by two channels near the limbus via convection currents. After passing through the anterior chamber, the trabecular meshwork serves as the chief drainage route. The trabecular channel comprises the uveal and corneoscleral meshwork, the juxtacanalicular tissue, and finally Schlemm s canal. 7 The uveal-scleral tract is cited as the alternate or non-conventional outflow. In this pathway, the aqueous seeps within and between multiple tissue types including the supra-ciliary space, ciliary muscle fibers, the supra-choroidal space, vessels of the choroid, interwoven collagen of the sclera, and finally to adjacent lymphatic vessels. 8-9 This physiological elimination process has much less capacity compared to the trabecular meshwork, but its advantage is that it much more pressure independent. Regardless of the pathway the aqueous takes, equilibrium must be maintained between aqueous production and drainage; otherwise, IOPs will invariably increase, giving rise to glaucoma. 7

4 A REVIEW OF PEDIATRIC GLAUCOMA 3 The typical infantile glaucoma patient will present in the first three years of life. The parent may bring in the child to the clinic concerned due to the large size of one or both of the child s eyes. Another common presenting sign is a cloudy edematous cornea. Upon history and examination, the child will classically exhibit a triad of symptoms: epiphora, photophobia, and blepharospasm. 3 The pressure inside of the eye is causing the orbit to struggle to accommodate the eye s larger size and often the child is trying to stimulate vision by rubbing the eye or via involuntary spasm. Buphthalmos is Greek for eye of the bull, referring to the pathognomonic sign of a marked increase in the magnitude of the eye due to the stretching of the sclera. Buphthalmos is an important distinction as a normal adult eye is fully formed, and the sclera of an adult will not stretch like a pediatric patient s eye. Pediatric glaucoma is classically bilateral and corneal edema is often present, along with Haab striae resulting from the corneal insult. 3 If a child presents with a cloudy cornea or other media opacities, slit lamp biomicroscopy may be problematic. In this instance, the clinician should perform a B-scan ultrasonography to image the posterior segment for other pathology. 3,10 A B-scan can aptly penetrate ocular tissues to produce a two-dimensional image. B-scans are highly utilized because they are non-invasive, in-office and relatively inexpensive. The procedure is instrumental in ruling out abnormalities including, but not limited to: tumors, retinal detachments, foreign bodies, inflammatory disorders, choroidal nevi, and melanomas. Furthermore, the optic nerve can be imaged and assessed with B-scan for papilledema and neoplasms. 10 While elevated IOP s are a causative risk factor, the hallmark of glaucoma is optic nerve cupping with associated visual field loss due to the IOP bearing down on the optic nerve. The pressure compresses the vasculature and destroys the nerve fibers. As an aside, if a patient does not have characteristic visual field loss, the patient may just be an ocular hypertensive. A markedly increased cup to disc ratio, especially in an infant, is a sign of glaucomatous damage. Any significant asymmetry between eyes is cause for concern. The severity of optic nerve

5 A REVIEW OF PEDIATRIC GLAUCOMA 4 cupping depends on when the child presents and the IOP s, many times the other symptoms point to glaucoma before clinically assessable damage occurs. Assessing a young child s intraocular pressure is often a tribulation. Goldmann Applanation Tonometry is the widely accepted as the standard of care. Regrettably, it is impractical to do on a toddler or neonate. To date, there is significant debate as to what is the best method of tonometry on pediatric patients. Common alternatives include Tonopen, various forms of non-contact tonometry or, as a last resort, digital tonometry is employed. It is important to remember that tonometry measurements can differ extensively between instruments and are influenced by corneal thickness. Tonopen and non-contact tonometry tend to overestimate IOP s compared to Goldmann. 11,12 Pharmacotherapy is beneficial in treating pediatric glaucoma, at least to defer surgical intervention. Topical eye drops and oral medications are both used. Beta-blockers, specifically timolol, are conventional first-line treatment. Latanoprost, Brimonidine, and Dorzolamide are also alternative mechanism of action choices. 13 Ultimately, medications are not able to keep the IOP near target levels for an extended period. Combination therapy is sometimes used in certain cases, but the patient will in due course need surgical intervention. Surgical interventions for congenital glaucoma originated with the introduction of goniotomy surgery in Goniotomy is defined as a procedure to generate openings within the trabecular meshwork of the iridocorneal angle. 3 Goniotomy remained the pillar treatment for congenital glaucoma until a new technique called trabeculectomy ab externo was developed in This technique entails surgically augmenting Schlemm's canal from outside the eye by fashioning a scleral pouch under the conjunctiva, known as a bleb, which enables additional aqueous drainage. Commonly the bleb is concealed under the superior lid. Today there are many novel extensions to angle surgery involving implanted shunts, valves and laser. Regardless, the mainstay of congenital glaucoma treatment is still trabeculectomy, or the less invasive trabeculotomy, to reduce intraocular pressure by mechanically assisting aqueous outflow

6 A REVIEW OF PEDIATRIC GLAUCOMA 5 References 1. Brandt JD. Congenital Glaucoma. In: Ophthalmology. Vol 4th ed. Philadelphia, PA: SAUNDERS, an imprint of Elsevier Inc.; 2014: congenital glaucoma. In: Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. Saunders, an imprint of Elsevier, Inc; Mandal AK, Chakrabarti D. Update on congenital glaucoma. Indian J Ophthalmol 2011;59(Suppl1):S148 S Aponte EP, Diehl N, Mohney BG. Medical and surgical outcomes in childhood glaucoma: A population-based study. J AAPOS 2011;15: Deluise VP, Anderson DR. Primary infantile glaucoma (congenital glaucoma). Survey of Ophthalmology 1983;28: Sarfarazi M, Akarsu NA, Hossain A, Turacli EM, Aktan GS, Barsoum-Homsy M, Chevrette L, Sayli SB. Assignment of a Locus (GLC3A) for Primary Congenital Glaucoma (Buphthalmos) to 2p21 and Evidence for Genetic Heterogeneity. Genomics 1995;30: Goel M, Picciani RG, Lee RK, Bhattacharya SK. Aqueous Humor Dynamics: A Review. The Open Ophthalmology Journal 2010;4: Toris CB. Uveoscleral Outflow: Current understanding and methods of measurement. Glaucoma Today Kent C. Uveoscleral Outflow: A Better Way to Go? Review of Ophthalmology March Urban D, Ramey J, Bunch R, Lighthizer N. Scoring an A on a B-Scan: Master the art of ultrasound imaging. Review of Optometry March Bradfield YS, Kaminski BM, Repka MX, Melia M. Comparison of Tono-Pen and Goldmann applanation tonometers for measurement of intraocular pressure in healthy children. Journal of American Association for Pediatric Ophthalmology and Strabismus 2012;16: Gupta A, Raina U, Rathie N, Gupta S, Thakar M. Comparison of Goldmann applanation tonometer, Tono-Pen and noncontact tonometer in children. Oman Journal of Ophthalmology 2016;9: Coppens G, Stalmans I, Zeyen T, Casteels I. The Safety and Efficacy of Glaucoma Medication in the Pediatric Population. Journal of Pediatric Ophthalmology & Strabismus 2009;46: Chang TC, Cavuoto KM. Surgical Management in Primary Congenital Glaucoma: Four Debates. Journal of Ophthalmology 2013;2013: Luntz MH, Livingston D. Trabeculotomy Ab Externo and Trabeculectomy in Congenital and Adult-Onset Glaucoma. American Journal of Ophthalmology 1977;83:174 9.

PedsCases Podcast Scripts

PedsCases Podcast Scripts This is a text version of a podcast from Pedscases.com on Approach to Childhood Glaucoma. These podcasts are designed to give medical students an overview of key topics in pediatrics.