History
The history of low-tension glaucoma (LTG) may include the following:
-
Ocular history
-
Steroid use
-
Trauma
-
Vasospasm (see below)
-
Coagulopathies - Previous blood loss or shocklike episode
-
Systemic nocturnal hypotension (notably in older thin, white women)
-
Autoimmune disorders (evidence of other autoimmune diseases common)
-
Systemic vascular disease
-
Thyroid disease - Increased incidence of thyroid disease in patients with low-tension glaucoma (6 of 25 patients in 1 series)
-
Sleep apnea (particularly in heavy men)
-
Alzheimer disease - Associated with mild increase in cup-to-disc ratio
-
Family history of glaucoma or optic neuropathy
Physical
Physical examination findings in low-tension glaucoma (LTG) may include the following:
-
Conduct general medical examination (eg, blood pressure, carotid arteries).
-
Exclude ocular hypertension and POAG
-
Refractive error - Myopia
-
Cornea (see below)
Central corneal thickness thinner in normal-tension glaucoma [3] in correlation with severity
Keratic precipitates indicating uveitis
Krukenberg spindle indicating pigment dispersion
-
Iris - Transillumination defects or pigment dusting indicating pigment dispersion
-
Anterior chamber (see below)
By definition, low-tension glaucoma has an open, normal-appearing angle.
Rule out angle closure and angle recession.
-
Lens - Glaucomflecken indicating previous IOP elevation, probably secondary to acute angle closure
-
Posterior synechiae
-
Peripheral anterior synechiae
-
Intraocular pressure (see below)
-
Myopic - Greatest risk of progression
-
Senile sclerotic - Older with vascular disease
-
Focal ischemic - May be younger
-
Optic disc in low-tension glaucoma as compared to high-tension glaucoma (controversial)
-
Larger discs
-
Peripapillary disc atrophy (particularly beta zone)
-
Thin disc rims; more commonly shows notching, more sloping of cup
-
Narrow vessels in peripapillary area, independent of stage of the disease [5]
-
Disc hemorrhages [6]
-
Acquired pit
-
Retina - Arteriosclerotic changes indicating vascular disease
-
Visual fields in low-tension glaucoma as compared to high-tension glaucoma (controversial)
-
Focal
-
Closer to fixation
-
Deeper
-
Blood pressure - Nocturnal hypotension
-
Carotid bruit indicating carotid insufficiency
Causes
Low-tension glaucoma is associated with the following:
-
Migraine
-
Peripheral vasospasm, Raynaud syndrome
-
Generalized peripheral vascular endothelial dysfunction [7]
-
Ocular circulation insufficiency (lower ocular pulse amplitude) [7]
-
Increased resistance index in the central retinal artery (role in progression of visual field defect) [8]
-
Impaired vascular autoregulation (prolonged arteriovenous venous passage time in relation to ocular perfusion) [9]
-
Autoimmune disorders
-
Systemic vascular disease (ie, atherosclerotic disease, cerebrovascular insufficiency) [10]
-
Systemic nocturnal hypotension
-
Sleep apnea (decreases oxygen saturation)
Complications
Permanent loss of vision can occur if low-tension glaucoma is not detected early.