Compressive visual field defects are a general term for visual field changes caused by compression of the visual pathway due to mass effect. Masses include tumors, aneurysms, hematomas, abscesses, and cysts.
The pattern of visual field defects varies greatly depending on which part of the visual pathway is compressed. Therefore, it is clinically very important to be able to estimate the location of the lesion from the pattern of visual field defects.
The most common cause of chiasmal lesions is pituitary adenoma. In children, craniopharyngioma is more frequent.
The incidence of orbital tumors in Japan is shown below.
| Benign (top 5) | Proportion | Malignant (top 3) | Proportion |
|---|---|---|---|
| Idiopathic orbital inflammation | 20% | Malignant lymphoma | Most common |
| Pleomorphic adenoma | 13% | Lacrimal gland carcinoma | — |
| Hemangioma | 13% | Metastatic tumor | — |
| Dermoid cyst | 10% | — | — |
| Reactive lymphoid hyperplasia | 10% | — | — |
Compression of the optic nerve at any site can cause compressive optic neuropathy. The most common site of compression is the orbital apex.
At the optic chiasm, pituitary adenoma is the most common cause. Within the orbit, idiopathic orbital inflammation, pleomorphic adenoma, and hemangioma are the most frequent. In children, craniopharyngioma is common.
Typically, it presents with slowly progressive vision loss in one eye. However, pituitary apoplexy or aneurysm rupture can cause acute onset.
Characteristic findings according to the compression site are shown below.
Orbital Lesions
Proptosis: The most representative finding.
Optic disc edema: Appears early; progresses to pallor and atrophy.
RAPD: Relative afferent pupillary defect is present.
Choroidal folds: Caused by tumor compression of the globe.
Opticociliary shunt vessels: Actually represent retinochoroidal venous collaterals.
Chiasmal Lesion
Bitemporal hemianopsia: A classic finding caused by compression of crossing nasal fibers. Often asymmetric and incomplete.
Junctional scotoma: Central scotoma in the affected eye plus contralateral superior temporal visual field defect, suggesting an anterior chiasmal lesion.
Band optic atrophy: In the chronic phase, pallor of the temporal and nasal central optic disc.
Postchiasmal Lesions
Optic tract: Incongruous homonymous hemianopsia with RAPD. Near the cerebral peduncle, contralateral hemiparesis may occur.
Temporal lobe: Homonymous superior quadrantanopsia (“pie in the sky”). Reflects damage to Meyer’s loop.
Parietal lobe: Homonymous inferior quadrantanopia (“pie on the floor”). May be accompanied by Gerstmann syndrome and hemispatial neglect.
Occipital lobe: Congruous homonymous hemianopia. Macular sparing may be observed.
In compressive optic neuropathy, the optic disc initially swells and progresses to pallor and atrophy if treatment is delayed. Optical coherence tomography (OCT) detects localized thinning of the inner retinal layers corresponding to visual field defects.
In compressive optic neuropathy due to sphenoid fibrous dysplasia, glaucomatous-like cupping has been reported, with OCT showing thinning of the retinal nerve fiber layer (RNFL) in all quadrants and diffuse loss of the ganglion cell layer5).
At the anterior chiasm, junctional scotoma (central scotoma in the affected eye plus contralateral superior temporal defect) or Traquair junctional scotoma (monocular hemianopic defect) may occur. Posterior to the chiasm, homonymous hemianopia or quadrantanopia appears depending on the compression site.
The causes of compressive visual field defects are classified according to the site of compression along the visual pathway.
In adults, vascular/ischemic causes are common. In children, neoplastic causes are typical.
Humphrey automated perimetry (24-2, 30-2, 10-2) is recommended for all patients with unexplained visual impairment. The pattern of visual field defects helps estimate the compression site and determine the imaging strategy.
Visual field testing is also useful for assessing disease progression and treatment efficacy, and should be performed over time.
| Examination Method | Advantages | Main Indications |
|---|---|---|
| CT | Excellent for detecting bone lesions, calcifications, and bone destruction | Orbital bone lesions, surgical planning |
| MRI | Best for soft tissue evaluation. Gold standard. | Tumor characterization, optic nerve assessment |
| PET/CT | Search for systemic metastases | Staging of malignant tumors |
On T2-weighted MRI, it is useful for differentiating tumor characteristics. Solid tumors (such as lymphoma and meningioma) appear hypo- to isointense, while vascular and cystic tumors (such as cavernous hemangioma and dermoid cyst) appear hyperintense. Dynamic MRI is also useful in contrast-enhanced MRI, and delayed enhancement is characteristic of cavernous hemangioma.
Optical coherence tomography (OCT) detects localized thinning of the inner retinal layers and is useful for early detection of mild optic atrophy. It can detect abnormalities earlier than visual field testing. It also helps in estimating prognosis after treatment.
Compressive optic neuropathy may present with glaucomatous cupping of the optic disc 5). The following findings suggest a non-glaucomatous etiology.
A report indicates that 6.5% of patients diagnosed with normal-tension glaucoma had clinically significant intracranial compressive lesions5).
Glaucoma presents with arcuate scotomas along the horizontal nerve fiber bundle, whereas compressive optic neuropathy is characterized by visual field defects that respect the vertical meridian. Pallor disproportionate to cupping, rapid vision loss, and onset before age 50 suggest a compressive lesion. If suspected, neuroimaging should be performed.
Most mass lesions compressing the visual pathway require surgery for both diagnosis (pathological confirmation) and treatment (relief of mass effect). Multidisciplinary collaboration (ophthalmology, neurosurgery, otolaryngology, endocrinology, etc.) depending on the cause is essential.
Once the compression of the optic chiasm is relieved, improvement in visual acuity and visual field can be observed. However, if optic atrophy is already evident, the visual prognosis is poor. Measurement of retinal thickness using OCT is useful for estimating prognosis after treatment.
In compressive optic neuropathy, a delay in intervention of 7 to 10 days or more is associated with an increased risk of irreversible visual impairment4).
Relief of compression can improve visual acuity and visual field. However, recovery is limited if optic atrophy has progressed. Better initial visual acuity indicates a better prognosis.
The visual pathway follows the route: retinal ganglion cells → optic nerve → optic chiasm → optic tract → lateral geniculate nucleus (LGN) → optic radiation → striate cortex (V1).
At the optic chiasm, nasal retinal fibers cross to the opposite side, while temporal retinal fibers remain uncrossed and proceed ipsilaterally. Nasal fibers process the temporal visual field, and temporal fibers process the nasal visual field. Therefore, compression of crossing fibers causes temporal visual field defects, while compression of non-crossing fibers causes nasal visual field defects.
The Wilbrand knee (a structure where contralateral inferior nasal retinal fibers briefly enter the ipsilateral optic nerve before crossing) has been proposed as a cause of junctional scotoma, but its existence is debated.
The optic radiation emerges dorsally from the LGN and divides into two bundles.
The tip of the occipital cortex (macular representation area) receives dual blood supply from the middle cerebral artery and posterior cerebral artery, so macular sparing can occur with damage to a single vascular territory.
Multiple mechanisms are involved in the development of compressive optic neuropathy1).
The effect of the tumor on the optic chiasm involves both direct compression and inflammatory blood flow disturbance.
In temporal lobe lesions caused by compressive lesions, the visual field defect shows a gradual isopter pattern compared to vascular lesions.
Blood flow to the LGN is supplied by the anterior choroidal artery and posterior choroidal artery. Segmental homonymous visual field defects occur depending on the site of damage to each small artery.
Teprotumumab (IGF-1R inhibitory monoclonal antibody) is the first approved drug for thyroid eye disease. Patients with compressive optic neuropathy (CON) were excluded from clinical trials, but efficacy has been reported in mild CON cases.
Chiou et al. (2021) reported two cases of mild CON due to thyroid eye disease that were resistant to IV steroids; after treatment with teprotumumab, visual field defects completely resolved in both cases 3). In the first case, resolution was observed after the third dose, and in the second case after the second dose.
Tsuei et al. (2022) reported a case of a 17 mm paraclinoid internal carotid artery aneurysm treated with a flow diverter (Pipeline embolization device). Despite complete angiographic occlusion, the aneurysm enlarged and caused compressive optic neuropathy 8). Visual fields improved after microsurgical optic nerve decompression and coagulation shrinkage of the aneurysm.
Zhou et al. (2024) performed endoscopic endonasal optic nerve decompression (ETOND) in four adolescent patients (mean age 12.75 years, all male) with visual impairment due to pneumosinus dilatans of the sphenoid bone 10). All cases were resistant to steroid pulse therapy, but visual improvement was achieved with ETOND.
Kong et al. (2022) reported a case of bilateral orbital apex infiltration due to nasopharyngeal carcinoma leading to loss of light perception 7). Despite treatment with steroids, chemotherapy, and radiotherapy, the right eye had no light perception and the left eye only hand motion. The optic nerve is considered to have the lowest recovery rate among cranial nerves 7).
Haydar et al. (2024) reported a case of compressive optic neuropathy caused by a hydatid cyst within the inferior rectus muscle in a 22-year-old male from Afghanistan 9). Complete excision and long-term albendazole therapy restored vision from 20/200 to 20/20.
