A seven-year-old boy with intermittent exotropia. (The two-year-old Hispanic boy also had exotropia and other symptoms not typically associated with congenital glaucoma.)
Source: Brian G. Mohney, M.D.
Report shows what led to misdiagnosis
Classic signs of congenital glaucoma may not be enough to diagnose the condition. That’s what a new case study suggests, in which a misdiagnosis of megalocornea occurred originally instead of the proper diagnosis of congenital glaucoma.
While congenital glaucoma usually presents with photophobia, epiphora, and blepharospasm, this case presented without tearing or photophobia, but rather with an enlarged right eye and intermittent right exotropia, noted study authors Kelly Frantz, O.D., professor of optometry, Illinois College of Optometry, Chicago and Nadine Girgis, O.D., assistant professor of optometry, Nova Southeastern University College of Optometry, Ft. Lauderdale. The study was published in Optometry.
“The presence of a unilateral or bilateral enlarged cornea is another indication to investigate for glaucoma in a child, even without the classic signs,” Drs. Frantz and Girgis wrote.
For future reference
In addition to the signs already noted, the two-year-old Hispanic boy in the study had high myopia and an optic nerve cup-to-disc ratio larger in the right eye than in the left eye. His IOP was normal, and he was initially diagnosed by the consulting ophthalmologist with unilateral megalocornea.
“He did not have any other typical signs and symptoms of primary congenital glaucoma,” Drs. Frantz and Girgis reported. “An EUA [examination under anesthesia] eight months later led to a diagnosis of primary congenital glaucoma based on the new appearance of Haab’s striae, further enlargement of the cornea, and an elevated IOP.”
But meanwhile, after the initial diagnosis of megalocornea, the patient was instructed to return to the authors’ clinic for follow-up care. At one follow-up visit, oblique corneal striae were noted in the right eye. Megalocornea usually presents bilaterally, Drs. Frantz and Girgis noted, which already made the diagnosis an atypical one. And while IOP was still within normal range, and fundus examination found no change in disc appearances, the appearance of corneal striae was enough to send the patient back to an ophthalmologist for evaluation, the doctors reported.
Megalocornea is characterized by large, clear corneas, normal IOP, but no Haab’s striae, Drs. Frantz and Girgis noted.
Although the patient did not keep that appointment, he was eventually seen by a pediatric ophthalmologist several months later. His IOP was measured at 22, 23, and 21 mm Hg in the right eye with a Tonopen (Western Ophthalmics, Lynnwood, Wash.), and 25 and 22 mm Hg in the left eye with a Tonopen. New striae also had appeared and corneal measurements were larger (18 mm horizontally by 14 mm vertically in the right eye and 14 mm horizontally by 12 mm vertically in the left eye).
“At this point, the pediatric ophthalmologist made a diagnosis of primary congenital (specifically, infantile) glaucoma because of the new corneal striae [in the right eye], increase in corneal diameter OU [in both eyes], and slight increase in IOP OU compared with the previous examination,” Drs. Frantz and Girgis wrote.
Unfortunately, while the patient was initially prescribed medication to determine if IOP responded adequately, he was lost to follow-up.
Nonetheless, this case study concludes importantly that while primary congenital glaucoma has the best prognosis among all the congenital glaucomas, it may be important to look beyond classical signs and symptoms to accurately diagnose it.
Not everyone agrees
Mark A. DiPillo, M.D., Wyomissing, Pa., suggested that there were still plenty of factors about this case that should have raised suspicion about a greater possibility of congenital glaucoma early on.
Although Haab’s striae might not have been noticed earlier—which was an important factor in making the proper diagnosis upon re-examination—the cup-to-disc ratio was enlarged, which was suspicious, Dr. DiPillo said. Further, variability in corneal thickness could have provided a clue as to whether the condition was congenital glaucoma (at the initial ophthalmologist visit in which megalocornea was diagnosed, pachymetry did measure the right cornea thinner than the left, although the gap was not immense (517 microns versus 560 microns).
“Further, the initial presentation said the eye seemed to be enlarging,” Dr. DiPillo said. “Megalocornea isn’t necessarily something that would be enlarging. There are a lot of suspicious features in the initial exam that would have suggested closer follow-up for congenital glaucoma.”
Editors’ note: Drs. Frantz and Girgis have no financial interests related to this study. Dr. DiPillo has no financial interests related to his comments.
DiPillo: 610-378-1344, firstname.lastname@example.org
Frantz: 312-949-7000, email@example.com
Girgis: 954-262-1728, firstname.lastname@example.org