How is ADOA Differentiated from Normal Tension Glaucoma?

It is common for adults with Autosomal Dominant Optic Atrophy (ADOA) to be initially misdiagnosed with Normal Tension Glaucoma (NTG). Both conditions are characterized by progressive optic nerve damage and vision loss while intraocular pressure (the fluid pressure inside the eye) remains within normal limits ^[1]. Because glaucoma is much more common than hereditary optic atrophies, eye doctors may suspect NTG first. However, specialists can differentiate the two conditions by carefully analyzing high-resolution eye scans, evaluating visual field tests, and confirming the diagnosis with OPA1 genetic testing ^[2][3].

Why the Two Conditions Can Look Similar

The optic nerve acts like a cable connecting your eye to your brain. It is made up of millions of retinal ganglion cells and their nerve fibers. Both ADOA and NTG cause these essential cells to slowly die off over time, a process called atrophy ^[2].

When a doctor examines the eye, they see that the nerve fiber layer is thinning, but the pressure in the eye is normal ^[1]. If a patient does not have a known family history of early-onset vision loss—which can happen if the genetic mutation is new or symptoms in relatives were mild—the doctor may logically assume the damage is due to Normal Tension Glaucoma.

Differentiating Features on an Eye Exam

Although the conditions look similar on a surface level, specialized testing reveals clear differences in how the damage occurs.

Visual Field Testing (Perimetry)

Visual field testing maps your peripheral and central vision to detect blind spots. This is a gold-standard test for both conditions, but the patterns of vision loss usually differ:

• ADOA: Vision loss typically starts in the center of your vision or between the center and the natural blind spot (central or cecocentral scotomas) ^[4][5].
• NTG: Glaucoma often affects mid-peripheral or side vision first, commonly producing arch-shaped blind spots (arcuate defects) or steps in the nasal field of vision ^[6][7].

Distinct Patterns on OCT Scans

Optical Coherence Tomography (OCT) is a non-invasive imaging test that takes high-resolution cross-section pictures of your retina. This scan is crucial for distinguishing ADOA from NTG:

• Macular vs. Peripheral Thinning: In ADOA, cell loss is typically concentrated in the macula (the center of the retina responsible for detailed central vision) and the papillomacular bundle (the nerve fibers directly connecting the macula to the optic nerve) ^[8][9]. In contrast, glaucomatous damage like NTG usually causes localized, focal thinning in patterns that correspond to the mid-peripheral vision loss ^[10].
• Optic Nerve Head Shape (The Lamina Cribrosa): OCT can also scan deep into the optic nerve to view a mesh-like structure called the lamina cribrosa. In NTG, this structure is typically pushed backward, appearing deeper and more curved due to structural remodeling ^[11]. In ADOA, this deep “cupping” is absent, and the deep structures look closer to those of a healthy eye ^[11].

Visual Appearance of the Optic Nerve

When your doctor looks directly at your optic nerve during a dilated eye exam, they observe different physical changes:

• Optic Disc Pallor: In ADOA, the optic nerve typically appears abnormally pale (pallor), reflecting the underlying atrophy of the nerve fibers ^[4][12].
• Optic Disc Cupping: In NTG, the nerve tissue usually thins at the rims, causing the center “cup” of the nerve to become enlarged and physically deepened ^[12][13].

Color Vision Changes

A hallmark of ADOA that is not typically seen in glaucoma is a specific difficulty with color vision. Many people with ADOA develop a blue-yellow color vision deficit (tritanopia) ^[14][15].

Summary of Clinical Differences

The Definitive Tiebreaker: OPA1 Genetic Testing

While advanced OCT scans and visual fields provide strong clinical evidence, genetic testing is the definitive tool used to confirm ADOA and rule out NTG completely ^[3][16].

The vast majority of ADOA cases are caused by mutations in the OPA1 gene. If your vision continues to worsen despite having low or medically controlled eye pressures, it is highly recommended to ask your eye doctor or a neuro-ophthalmologist about genetic testing. Identifying a pathogenic variant in the OPA1 gene confirms the diagnosis of ADOA and provides critical information about your genetic risks, which a genetic counselor can help you navigate ^[16][17].

Getting the correct diagnosis is critical. Glaucoma treatments, such as medicated eye drops or surgeries designed to lower eye pressure, will not stop or slow the progression of ADOA. (Safety Note: Never stop taking prescribed eye drops without consulting your doctor, as abruptly stopping glaucoma medication can be dangerous if you do have glaucoma.) Furthermore, confirming an OPA1 mutation allows doctors to screen for “ADOA plus,” a rarer form of the condition that can include other symptoms like hearing loss or muscle weakness ^[18][19]. Once diagnosed accurately, you and your care team can focus on appropriate low-vision management and connection with specialized support.