Nerve Cupping

L. Jay Katz

BASICS

DESCRIPTION

• Optic nerve cupping can be physiological.

• Pathological optic nerve cupping is a manifestation of regional ganglion cell death and loss of ganglion cell axons from the optic nerve.

• The majority of eyes with pathologic enlargement of the optic cup have glaucoma (1).

• Distinguishing glaucomatous from nonglaucomatous disc cupping can be difficult—in a retrospective review of optic nerve head photographs, Trobe et al. reported that pallor of the neuroretinal rim is 94% specific in predicting nonglaucomatous cupping while focal or diffuse obliteration of the neuroretinal rim is 87% specific in predicting glaucomatous cupping (2).

EPIDEMIOLOGY

Incidence

• The incidence of pathological nonglaucomatous cupping is unknown.

• The observed 4-year incidence of open-angle glaucoma was 1.2% at ages 40–49 years, 1.5% at ages 50–59 years, 3.2% at ages 60–69 years, and 4.2% in persons aged 70 years or more according to the Barbados Incidence Study of Eye Diseases (1992–1997) (3).

Prevalence

• The prevalence of pathological nonglaucomatous cupping is unknown.

• Approximately 67 million people are affected with glaucoma worldwide, and approximately 2 million people in the U.S. have glaucoma (1 in 136 people) (1).

• In developed countries, probably only half of those with glaucoma have been diagnosed.

RISK FACTORS

• Larger optic discs tend to have larger physiologic cup/disc ratio (4)[A].

• Please refer to the “Differential Diagnosis” section of this chapter.

• Please refer to the “Risk Factors” section of the specific diagnosis responsible for the pathological optic disc cupping.

Genetics

There is some dependence of an individual’s physiologic cup/disc ratio on the cup/disc ratio of the parents—multifactorial inheritance is likely (5).

GENERAL PREVENTION

For glaucomatous optic disc cupping: lowering intraocular pressure (IOP)

PATHOPHYSIOLOGY

• Pathologic optic nerve head cupping is a manifestation of retinal ganglion cell death and loss of ganglion cell axons from the optic nerve.

• The primary site of glaucomatous optic nerve damage is thought to be the lamina cribrosa—deformations of the lamina, kinking of nerve fibers, misalignment of laminar pores, blockade of axonal transport; however, the relationship between these findings and glaucomatous damage have not been firmly established (1).

• Other contributing factors may act at the level of the ganglion cell body.

ETIOLOGY

• Elevated IOP

• Ischemia/hypoxia

• Trauma

• Excitotoxicity and aberrant immunity have also been hypothesized to be factors in optic nerve damage (1).

COMMONLY ASSOCIATED CONDITIONS

• Please refer to the “Differential Diagnosis” section of this chapter.

• Please refer to the “Commonly Associated Conditions” section of the specific diagnosis responsible for the pathological optic disc cupping.

DIAGNOSIS

HISTORY

• Presence, onset, and nature of visual disturbance

• Systemic vascular risk factors, such as migraine, Raynaud’s diabetes, and hypertension

• History of ocular trauma or surgeries

• Family history of glaucoma or other optic neuropathies

• Neurological disturbances such as headaches, dizziness, and weakness of extremities

PHYSICAL EXAM

• Check for an afferent pupillary defect.

• Slit lamp examination of the anterior segment to check for signs of secondary glaucoma, such as iris transillumination defects, pseudoexfoliation material, anterior chamber cell or flare, and signs of prior surgery or trauma

• Gonioscopy

• Direct and indirect stereoscopic slit lamp biomicrospy to evaluate the optic nerve head, paying particular attention to

– narrowing of the neuroretinal rim width (relatively narrow rim inferotemporally or superotemporally can indicate glaucomatous damage)

– asymmetry in disc cupping (≥0.2)

– optic disc hemorrhage

– optic nerve color

– beta zone parapapillary atrophy

– optic nerve edema

– loss of retinal nerve fiber layer (focal or diffuse)

• The normal optic disc neuroretinal rim is characteristically broadest inferiorly, followed by superior and nasal rims, and narrowest temporally (ISNT rule).

• An analysis of patients from the Ocular Hyperten-sive Treatment Study and the European Glaucoma Prevention Study showed that an ocular hypertensive patient’s risk of developing glaucoma increased almost 50% for every 0.1 difference between eyes in cup-to-disc ratio (6).

• Staging of the optic disc using Armaly’s cup-to-disc ratio is commonly used.

• Spaeth’s disc damage likelihood scale directs attention to the narrowest area on the optic disc rim (scale 1–10) (7).

DIAGNOSTIC TESTS & INTERPRETATION

Lab

Initial lab tests

• Lab tests as indicated for suspected cause of pathologic optic disc cupping.

• Please refer to the “Differential Diagnosis” section of this chapter.

Follow-up & special considerations

Follow-up as indicated for the suspected cause of pathologic optic disc cupping

Imaging

Initial approach

• Optic disc photographs should be obtained to evaluate and follow patients through their course of treatment.

• Other optic nerve head imaging devices are also currently being used for optic nerve head assessment in glaucoma:

– Scanning laser polarimetry

– Heidelberg retinal tomography

– Optical coherence topography

Follow-up & special considerations

• Follow-up as indicated for the suspected cause of pathologic optic disc cupping

• If glaucoma is suspected, optic disc imaging should be obtained regularly (e.g., annually, or more often if a change in optic disc appearance is suspected) to document and assess the optic nerve head for change.

Diagnostic Procedures/Other

• Visual fields should be obtained at baseline and at regular intervals (e.g., annually, or more often if a change is suspected).

• Diurnal IOP testing may be useful if large IOP fluctuations or periods of IOP spike are suspected.

• Consider neuroimaging for:

– Loss of central visual acuity or central visual field

– Acute onset or rapidly progressive visual loss

– Markedly asymmetric or strictly unilateral optic neuropathy

– Hemianopic visual field loss

– Neuroretinal rim pallor

Pathological Findings

Atrophy of the retinal ganglion cell layer can be noted.

DIFFERENTIAL DIAGNOSIS

• Glaucoma

• Tilted optic nerve insertion

• Coloboma

• Myopic disc

• Posterior staphyloma

• Optic pit

• Hereditary optic neuropathy

• Antecedent optic nerve infarction

• Trauma

• Demyelinating optic neuritis

• Intraorbital and intracranial mass lesions

• Carotic artery fusiform enlargement

• Ischemic optic neuropathy

TREATMENT

MEDICATION

First Line

Please refer to the “Treatment” section of the specific diagnosis responsible for pathological optic disc cupping.

Second Line

Please refer to the “Treatment” section of the specific diagnosis responsible for pathological optic disc cupping.

ADDITIONAL TREATMENT

General Measures

Please refer to the “Treatment” section of the specific diagnosis responsible for pathological optic disc cupping.

Issues for Referral

Referral to a neuro-ophthalmologist may be considered if there is suspicion that the cause of the patient’s optic neuropathy or visual field defect has a possible neurological etiology.

Additional Therapies

Please refer to the “Treatment” section of the specific diagnosis responsible for pathological optic disc cupping.

COMPLEMENTARY & ALTERNATIVE THERAPIES

Please refer to the “Treatment” section of the specific diagnosis responsible for pathological optic disc cupping.

SURGERY/OTHER PROCEDURES

Please refer to the “Surgery/Other Procedures” section of the specific diagnosis responsible for pathological optic disc cupping.

IN-PATIENT CONSIDERATIONS

Initial Stabilization

Please refer to the “Inpatient Considerations” section of the specific diagnosis responsible for pathological optic disc cupping.

Admission Criteria

Please refer to the “Inpatient Considerations” section of the specific diagnosis responsible for pathological optic disc cupping.

IV Fluids

Please refer to the “Inpatient Considerations” section of the specific diagnosis responsible for pathological optic disc cupping.

Nursing

Please refer to the “Inpatient Considerations” section of the specific diagnosis responsible for pathological optic disc cupping.

Discharge Criteria

Please refer to the “Inpatient Considerations” section of the specific diagnosis responsible for pathological optic disc cupping.