POAG

New England Eye CenterGrand Rounds

Meher Yepremyan, MD

December 14, 2000


Case Presentation

An 8-year-old Russian boy was referred to the New England Eye Center for evaluation of haziness in his vision for at least two years, right worse than left. He denied pain or history of trauma.

The patient was born in Russia full term without complications. He had no past ocular history and no significant past medical history. He was not taking any medications and had no known drug allergies. The patient was a 3rd grade student. His family history was significant for angle closure glaucoma.


Examination

His best-corrected visual acuity was 20/25 with -0.75 +1.25 x 115 in the right eye and 20/20 with -0.25 +0.25 x 90 in the left eye. There was no afferent pupillary defect. Extraocular movements were full bilaterally. Visual fields were full to confrontation. Intraocular pressures were 46 mmHg in the right eye and 42 mmHg in the left eye.

Slit-lamp examination was unremarkable. Gonioscopy revealed indistinct landmarks and high iris insertion with prominent iris processes in both eyes.

External Photographs:

OD OS

Disc Photographs:

OD OS


Examination

His corneal diameters measured 13.5 mm in the right eye and 13 mm in the left eye. Dilated fundus examination revealed severe optic disc cupping affecting the right eye more than the left.

Humphrey Visual Fields

Visual field testing was unreliable.


Differential Diagnosis-Primary Childhood Glaucoma:

-Primary congenital open angle glaucoma

-Juvenile open angle glaucoma

-Primary glaucoma associated with systemic disease

-Primary glaucoma associated with ocular anomalies

-Secondary Childhood Glaucoma:

-Traumatic glaucoma

-Intraocular neoplasm

-Uveitis

-Lens-induced glaucoma

-steroid glaucoma

Optical Coherence Tomogram


Optical Coherence Tomogram

Optical Coherence Tomogram showed a mean nerve fiber layer thickness of 77 microns in the right eye and 96 microns in the left eye, consistent with significant thinning of the NFL, right grater than left.


Clinical Course

The diagnosis of late recognized Primary Congenital Open Angle Glaucoma was made based on the findings. The patient was started on Cosopt and Xalatan and was followed closely by the Glaucoma service.


Clinical Course

One year later, his best corrected visual acuity remained stable at 20/25 from the right eye and 20/20 from the left eye. His intraocular pressure stabilized in the 13 to 15 mmHg range. The comparison of the annual disc photos have not shown any changes in the optic disc cupping contour.

Since the intraocular pressure have been well controlled on medications alone, any surgical intervention was deferred.

Comparison of Annual Disc Photographs:

1999: OD OS

2000: OD OS


Discussion

Despite numerous descriptions of buphthalmos (large globe) in the sixteenth century, it remained for von Muralt to segregate this disorder as a type of glaucoma in 1869. In 1938 Otto Barkan successfully applied goniotomy -- surgical technique that has essentially remained unchanged today.

Primary congenital glaucoma occurs in one out of 10,000 births. It is usually bilateral and occurs slightly more frequently in males in the United States and Europe. Recent studies support an autosomal recessive inheritance pattern which is polygenic and multifactorial.


Barkan observed that in congenital glaucoma a thin, imperforate “membrane” covering the anterior chamber angle of the eyes, prevents aqueous humor outflow, and leads to increased intraocular pressure (IOP). This surface membrane is probably an endothelial surface which normally breaks apart, but which persists in congenital glaucoma.

Most observers, however, have documented a compact mass of compressed trabecular tissue, not resolvable by light microscopy into individual cells or sheets, giving the illusion of a continuous membrane. The underlying basis of the trabecular dysgenesis is still not known.


Most often the classic triad of epiphora, blepharospasm, and photophobia may precede the enlarged corneal diameter (megalocornea), buphthalmos, breaks in the Descemet’s membrane (Haab’s striae), corneal edema, and optic nerve head damage -- changes that occur because of increased IOP and distensibility of the neonatal globe.

Younger children are more likely to present with corneal edema and haze, whereas older children will more commonly present with frank megalocornea (horizontal diameter greater than 12 mm) or buphthalmos. As the axial length of the globe increases, myopia and astigmatism result.


Interestingly, cupping of the optic nerve head may be reversible with normalization of IOP because cupping most likely results from posterior displacement of the lamina cribrosa and enlargement of the scleral canal.

The angle may appear normal with the iris inserted more anteriorly and with a slightly different translucency of the trabecular meshwork surface.

In most cases, the findings of corneal enlargement, optic nerve head changes and buphthalmos are diagnostic for primary congenital glaucoma.


The definitive treatment for primary congenital glaucoma is surgical intervention. Because surgery is performed in the vast majority of patients, no long-term results using purely medical management to control the IOP are available.

Goniotomy is the most widely used initial surgical modality in the management of primary congenital glaucoma. Incising the area of trabecular meshwork near Schwalbe’s line lowers the point of iris insertion, widens the angle or interrupts the abnormal pull of the ciliary muscles on the trabecular fibers, loosening them and effecting a decompression of the trabecular meshwork.


An alternative to goniotomy is trabeculotomy ab externo, which can be used when corneal haze prevents an adequate gonioscopic view. Trabeculotomy ab externo, performed by cannulating Schlemm’s canal from an external approach and then tearing through the trabecular meshwork into the anterior chamber, creates a direct communication between the anterior chamber and Schlemm’s canal.

The outcome of the two procedures is essentially the same, with both enjoying a high success rate and a very low complication rate.


Prognosis is related to the age of the patient at the initial diagnosis. If glaucoma is present at birth, the cure rate is only 55%. If, however, it presents later during the third or fourth month, the long-term success rate increases to almost 100%.


Conclusion

An 8-year-old Russian boy presented with haziness in his vision, intraocular pressures of mid-forties, bilateral megalocornia, severe optic disc cupping, and significant thinning of nerve fiber layer. He was diagnosed with Primary Congenital Open Angle Glaucoma and successfully managed with medical intervention.


References•Barkan O: Technique of goniotomy. Arch Ophthalmol 19:217-221,1938.

•Barkan O: Pathogenesis of congenital glaucoma. Am J Ophthalmol 40:1-11, 1955.

•Sampolesi et al: Scanning electron microscopy of the trabecular meshwork in normal and glaucomatous eyes. Invest Ophthalmol Vis Sci. 16:302-14, 1977.

•Quigley HA: Childhood glaucoma: results with trabeculotomy and study of reversible cupping. Ophthalmology 89:219-26, 1982.

•Anderson DR: Trabeculotomy compared to goniotomy for glaucoma in children. Ophthalmology 90:805-806, 1983.


References•deLuise VP et al: Primary infentile glaucoma (congenital glaucoma). Surv Ophthalmol 28:1-19, 1983.

•Kiskis AA et al: Corneal diameter and axial length in congenital glaucoma. Can J Ophthalmol 20:93-7, 1985.

•Krieglstein GK: Congenital glaucoma -- diagnosis and management. Trans Ophthal Soc UK 105:549-54, 1986.

•Frank W et al: Congenital glaucoma -- a preventable cause of blindness. Arch Dis Child 64:649-50, 1989.

•Akarsu AN et al: A second locus (GLC 3A) for primary congenital glaucoma (buphthalmos) maps to the 1p36 region. Hum Mol Genet 5:1199-203, 1996.


References•Adachi M et al: Clinical experience of trabeculotomy for the surgical treatment of aniridic glaucoma. Ophthalmology 104:2121-25, 1997.

•Taylor RH et al: The epidemiology of pediatric glaucoma: the Toronto experience. J AAPOS 3:308-315, 1999.

•Walton DS: Glaucomas. Gallin PF eds. In: Pediatric Ophthalmology. New York, Thieme Medical Publishers, Inc, 2000.

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