CASE PRESENTATION
A 37-year-old white male was referred by a community
glaucoma specialist to the Kellogg Eye Center at the
University of Michigan in Ann Arbor for a glaucoma
evaluation. He had a history of Scheie syndrome, hyperopia,
narrow angles, and elevated IOP. His maximum
untreated IOP had been 28 mm Hg in both eyes 2 years
earlier, at which point he began treatment with timolol
0.5% eye drops q.i.d. in both eyes. He had no ocular history
of laser procedures or surgeries and had not used
any other eye drops.
At presentation, the patient complained of gradually worsening vision in both eyes over the past year. Besides Scheie syndrome, his medical history was significant for asthma, sleep apnea, and allergic rhinitis. His systemic medications included an albuterol inhaler and mometasone furoate nasal spray, which he used every other day. He had no family history of glaucoma, although his sister also had Scheie syndrome.
His visual acuity was 20/50 OU with a manifest refraction of +5.00 +0.75 X 81 OD and +5.00 +1.25 X 40 OS. An external examination revealed coarse facial features and a prominent brow. Goldmann applanation tonometry measured 21 mm Hg OD and 16 mm Hg OS. Central corneal thickness was 657 µm OD and 638 μm OS. A slit-lamp examination revealed diffuse stromal haze in the corneas, peripherally shallow anterior chambers, and clear lenses in both eyes (Figure 1). Gonioscopy yielded a difficult view due to the corneal haze, but no angle structures were visible in either eye. Despite the hazy view, an undilated fundus examination showed healthy optic nerves with cup-to-disc ratios of 0.2 OU, and the retinas appeared normal in both eyes. Automated perimetry with the Humphrey Field Analyzer (Carl Zeiss Meditec, Inc., Dublin, CA) showed nonspecific diffuse depression (Figure 2).
HOW WOULD YOU
PROCEED?
- Can the patient's angles be assessed by any other method?
- How would you expect this patient's angles to respond to peripheral laser iridotomy?
- With thick corneas, presumably due to stromal deposits of glycosaminoglycans, is his IOP overestimated by Goldmann applanation tonometry?
SURGICAL COURSE
Because the patient's angles
were difficult to assess with
gonioscopy, I obtained anterior
segment optical coherence
tomography (AS-OCT) imaging
(Visante OCT; Carl Zeiss
Meditec, Inc.), which showed
appositional narrowing for
360° in both eyes (Figure 3). I
then recommended a YAG
laser peripheral iridotomy in
both eyes, which was performed without complication despite the cloudy
corneas. Postoperatively, the patient administered
prednisolone acetate 1% eye drops q.i.d. for 5 days in
each eye. His timolol was continued.
OUTCOME
Repeat AS-OCT showed no significant change in angle
anatomy in either eye. Likewise, the patient's IOP remained
stable after the laser treatment. At this point, there was no
significant elevation in IOP in either eye with pupillary
dilation. Primarily because of his healthy optic nerves but
also because his visual fields were not definitely glaucomatous,
I instructed the patient to continue using timolol
and continued to observe him. He was referred for a
corneal evaluation as well, but given his relatively good
visual acuity, corneal transplantation was deferred.
DISCUSSION
Scheie syndrome is one of a rare group of disorders
known as mucopolysaccharidosis (MPS) in which abnormal
deposits of glycosaminoglycans (GAGs) are deposited
throughout the body, including in the tissues of the
eye.1 The incidence of all types of MPS is approximately
one in 20,000 live births.2 The genetic defects in the various
types of MPS produce specific abnormal lysosomal
enzymes, which are unable to properly metabolize GAGs.
In Scheie syndrome, the abnormal enzyme is alpha-Liduronidase,
and the inheritance of this disease is autosomal
recessive. Patients with Scheie syndrome typically
suffer from skeletal, cardiac, and respiratory problems,
although their phenotypic manifestations tend to be less
severe than in the other subtypes of MPS.1,2
Typical ocular findings in MPS include corneal opacification, ocular hypertension, glaucoma, retinopathy, and abnormalities of the optic nerve.1 Strabismus is not uncommon.3 Corneal clouding occurs because of an accumulation of GAGs in the corneal stroma. Ocular hypertension and glaucoma are thought to develop via three mechanisms. The first is crowding of the anterior chamber angle caused by the thickening of ocular structures due to deposits of GAGs, and angle-closure glaucoma by this mechanism has been described.4 The second mechanism is decreased aqueous outflow due to an accumulation of GAGs in the trabecular meshwork. Finally, goniodysgenesis has been noted in patients with MPS as well.5 Retinopathy in MPS is caused by GAGs deposited in the retinal pigment epithelium and in the photoreceptor layer. Optic disc swelling and atrophy can occur due to glaucoma or because of the compression of axons by dura and sclera thickened by GAG accumulations.1
This patient's hyperopia, which is related to the narrowing of his anterior chamber angles, is also likely to be at least partly associated with Scheie syndrome.1 His history of elevated IOP is probably affected by his thick corneas, which contain deposits of GAGs. It is not clear how GAGs in the corneal stroma affect corneal hysteresis, but it seems likely that his IOP is overestimated because of his increased corneal thickness. Studies have shown that corneal opacification in MPS is positively correlated with IOP and central corneal thickness.1,3 In MPS patients, however, having higher IOP even with thicker, more opaque corneas was associated with more advanced glaucomatous optic neuropathy.3
The utility of laser peripheral iridotomy in eyes with narrow angles associated with MPS has not been well studied. In this case, the angle configuration did not seem to widen after laser treatment, but it is possible that a patent peripheral iridotomy might help to reduce his risk of developing angle-closure glaucoma, whether acute or chronic. Because of the rarity of MPS, studying its association with glaucoma in a large case series in order to make recommendations about treatment is a difficult task. Observing these patients over time is the best opportunity for learning about the ocular complications from which they can suffer.
Jennifer S. Weizer, MD, is an assistant professor of ophthalmology and visual sciences at the Kellogg Eye Center at the University of Michigan in Ann Arbor. She acknowledged no financial interest in the products or companies mentioned herein. Dr. Weizer may be reached at (734) 763-3732; jweizer@med.umich.edu.
