Case Report

Misdiagnosed Glaucoma Confirmed as Morning Glory Disc

This disease can be relatively benign or can accompany neurological problems. Here’s how this doctor diagnosed and treated the patient.

Michael C. Radoiu, O.D.
Staunton, Va.

A 50-year-old white female was referred with a tentative diagnosis of normal tension glaucoma in her left eye. The referring doctor noted that the cup-to-disc ratio of the patient’s left optic nerve head was unusually large and dramatically asymmetrical compared to that of the right eye.

The patient reported no visual problems and experienced no discomfort. Her ocular, general health and family histories were unremarkable, and there was no known history of glaucoma. The patient was currently taking Premarin hormone replacement therapy (conjugated estrogens) and reported no known medical allergies. She wore a +2.00D reading prescription.

Diagnostic Data
Uncorrected distance acuities were 20/20-2 in the right eye, 20/20-3 in the left. Best-corrected near acuity was 20/20-1 in both eyes.
The pupil exam was normal, and extraocular muscle movements were smooth and full in range of motion. Cover testing revealed a nominal exophoria at distance and near. An external overview of both eyes was normal, and a slit lamp exam was unremarkable. The anterior chambers were wide open in all meridians. Intraocular pressures (9 a.m. reading) were 15mm Hg in the right eye, 16mm Hg in the left.

A dilated fundus examination revealed asymmetric cup-to-disc ratios of 0.3/0.3 in the right eye, 0.7/0.7 in the left. The left optic nerve head appeared scalloped and dramatically enlarged. The cup looked pale and receded.

The surrounding vasculature appeared to be entering and exiting the nerve at its margins in a radiated fashion (see figure). Viewed stereoscopically, the optic nerve head appeared excavated and surrounded by a concentric pattern of chorioretinal pigmentary hypertrophy. The right optic nerve head appeared normal with relatively shallow cupping.

A nerve fiber evaluation performed with red-free illumination showed no apparent wedging or thinning defects. Vessels in the right eye followed a traditional arcade pattern.

Further fundus evaluation revealed no other abnormalities. I took fundus photos of both optic nerve heads.

A baseline automated visual field evaluation showed a slightly enlarged blind spot in the left eye with nondescript superior depressions. Subsequent testing about seven weeks later revealed the same results. The visual field in the right eye was normal.


Treatment and Follow-up
I subsequently diagnosed morning glory syndrome. The distinctive petaloid appearance of the optic nerve head was the most telltale sign.

I explained the significance of the diagnosis to the patient and informed her that neurological problems can accompany this condition. However, I assured her that her case was relatively benign.

I advised the patient to return for an annual eye exam that would include a detailed fundus examination, fundus photography and visual fields. We also discussed the appropriate use of impact-resistant lenses.

Discussion
Morning glory disc is a congenitally enlarged, funnel-shaped area of the optic nerve head surrounded by an elevated ring of chorioretinal pigmentary change.1
Opinions vary as to whether this rare condition is a variation of an optic nerve head coloboma or an optic nerve dysplasia that arises from an unusually large scleral foramen.1 Morning glory disc is not a true coloboma, but a posterior ectasia with associated disturbance to the surrounding sclera.

Morning glory disc is believed to result when incomplete neuroectodermal development leads to an abnormal closure of the embryonic fissure.2-5 While we know that this disorder is congenital, we’re not sure if there’s a molecular or genetic basis as well.6

One thing we do know: Morning glory disc usually doesn’t occur by itself. The condition is usually benign, but studies have observed the condition in patients with other ocular and systemic disorders (see “Other Disorders in Patients with Morning Glory Disc,” page 108).

Associated neurological defects are especially common.7 Basal encephalocele, hypopituitaryism and hypertelorism have often been found in patients with morning glory disc.1,8-11

Retinal detachment is a frequent ocular complication of morning glory disc. That’s because subretinal fluid accumulates at the posterior pole secondary to ectasic distension.12-14

Additional ocular complications include cataracts, strabismus (in up to half of cases), high myopia, microcornea and Duane’s retraction syndrome.1

Diagnosis of morning glory disc rests primarily on a stereoscopic evaluation of the optic nerve head. Three things to look for: a radial vascular pattern that enters and exits the nerve head, an excavation of the cup and an overall enlargement of the affected disc.1 The dramatic enlargement of the nerve head area often leads to an incorrect diagnoses of glaucoma or other optic nerve head anomalies (see, “Optic Disc Anomalies that May Mimic Morning Glory Disc,” right).

Additional tests that can help you confirm your diagnosis include:
• Visual fields. Patients whose cases are unilateral may have decreased visual acuity and a centro-cecal scotoma.1 Bilateral cases, which are rare, generally present with decreased vision in both eyes.1,8-10,15
• Imaging (CT scan and MRI).16,17 Look for anatomical enlargement of the optic nerve head, the foramen and the back of the optic nerve.
• Electrodiagnostic testing. These patients exhibit reduced electroretinogram amplitudes, and their visual-evoked responses typically display normal latencies but subnormal amplitudes.18

Treatment mainly involves monitoring the patient and educating him or her about the condition. Remember, patients with morning glory disc are at a greater risk for retinal detachment. Stress the importance of safety and encourage the patient to wear safety eyewear, especially if he or she is very active or works in a potentially hazardous occupation.1 Also instruct the patient to return for an annual exam, which should include visual fields, a dilated fundus exam and fundus photos.1,8-10
Consider referring the patient to an internist to monitor for the systemic disorders that may accompany morning glory disc. Also refer for neurological testing if warranted.

Morning glory disc is a rare optic nerve anomaly that is often misdiagnosed as glaucoma or another optic nerve anomaly. The condition is usually benign, but it can cause visual field defects and decreased vision. It also has been correlated with some neurological problems.

Proper diagnosis, vigilant follow-up and counseling about safety eyewear are an essential part of your treatment plan. 

Dr. Radoiu is in private practice and is a member of Review of Optometry’s editorial review board.

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