You are in: eMedicine Specialties > Ophthalmology > INTRAOCULAR PRESSURE Glaucoma, Low TensionArticle Last Updated: Jun 22, 2006AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Iqbal Ike K Ahmed, MD, FRCSC, Clinical Assistant Professor, Department of Ophthalmology, University of Utah Iqbal Ike K Ahmed is a member of the following medical societies: American Academy of Ophthalmology, American Society of Cataract and Refractive Surgery, Canadian Ophthalmological Society, and Ontario Medical Association Coauthor(s): Baseer U Khan, MD, Staff Physician, Department of Ophthalmology, University of Toronto, Canada; Khalid Hasanee, MD, Glaucoma and Anterior Segment Fellow, Department of Ophthalmology, University of Toronto Editors: Neil T Choplin, MD, Adjunct Clinical Professor, Department of Surgery, Section of Ophthalmology, Uniformed Services University of Health Sciences; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Martin B Wax, MD, Clinical Professor, Department of Ophthalmology, University of Texas Southwestern Medical School; Vice President, Ophthalmology Research and Development, Head, Ophthalmology Discovery Research, Alcon Labs, Inc; Lance L Brown, OD, MD, Ophthalmologist, Affiliated With Freeman Hospital and St John's Hospital, Regional Eye Center, Joplin, Missouri; Hampton Roy Sr, MD, Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences Author and Editor Disclosure Synonyms and related keywords: LTG, low-pressure glaucoma, optic neuropathy, intraocular pressure, primary open-angle glaucoma, POAG INTRODUCTIONSection 2 of 10
  BackgroundLow-tension glaucoma (LTG) is a chronic optic neuropathy that affects adults. Its features parallel primary open-angle glaucoma (POAG), including characteristic optic disc cupping and visual field loss, with the exception of a consistently normal intraocular pressure (IOP), ie, less than 22 mm Hg. PathophysiologyLTG is an optic neuropathy with chronic loss of retinal ganglion cells (RGC) due to a genetic hypersensitivity to IOP. This condition also is due to vascular factors, including vasospasm and ischemia. FrequencyUnited StatesUp to 15-25% of patients with POAG experience LTG. According to the Baltimore Eye Study, 50% of individuals with glaucomatous disc and visual field changes had an IOP of less than 21 mm Hg on a single visit, and 33% had an IOP of less than 21 mm Hg on 2 measurements. InternationalAn increased prevalence of LTG exists in Japan. Mortality/MorbidityLoss of peripheral vision is associated with LTG. RaceAn increased prevalence of LTG exists in Japan. SexLTG is more common in females than in males. AgeThe mean age of patients with LTG is 60 years; they are older than patients with POAG. CLINICALSection 3 of 10
History
Physical
CausesLTG is associated with the following:
DIFFERENTIALSSection 4 of 10
Central Retinal Artery Occlusion Glaucoma, Angle Closure, Acute Glaucoma, Angle Closure, Chronic Glaucoma, Drug-Induced Glaucoma, Pigmentary Glaucoma, Primary Open Angle Glaucoma, Uveitic Optic Neuritis, Adult Optic Neuropathy, Anterior Ischemic Optic Neuropathy, Compressive Posner-Schlossman Syndrome Sarcoidosis Toxic/Nutritional Optic Neuropathy
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| Drug Name | Brimonidine (Alphagan) |
|---|---|
| Description | Selective alpha2-receptor that reduces aqueous humor formation and may increase uveoscleral outflow or inhibit inflow. |
| Adult Dose | 1 gtt in affected eye(s) tid |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; patients receiving MAOI therapy |
| Interactions | Coadministration with topical beta-blockers may further decrease IOP; tricyclic antidepressants may decrease effects of brimonidine; CNS depressants, such as barbiturates, opiates, and sedatives, may potentiate effects of brimonidine |
| Pregnancy | B - Usually safe but benefits must outweigh the risks. |
| Precautions | May exacerbate or precipitate ocular irritation, topical sensitivity, vasovagal attack, and optic nerve ischemia in patients with advanced glaucomatous optic neuropathy |
By slowing the formation of bicarbonate ions with subsequent reduction in sodium and fluid transport, it may inhibit carbonic anhydrase in the ciliary processes of the eye. This effect may decrease aqueous humor secretion, reducing IOP.
| Drug Name | Dorzolamide (Trusopt) |
|---|---|
| Description | Used concomitantly with other topical ophthalmic drug products to lower IOP. If more than 1 ophthalmic drug is being used, administer the drugs at least 10 min apart. Reversibly inhibits carbonic anhydrase, reducing hydrogen ion secretion at renal tubule and increasing renal excretion of sodium, potassium bicarbonate, and water to decrease production of aqueous humor. |
| Adult Dose | 1 gtt in affected eye(s) tid |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity |
| Interactions | Coadministration with high-dose salicylate therapy may increase toxicity; may have additive systemic effects if patient is already on oral carbonic anhydrase inhibitors |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Local ocular adverse effects, primarily conjunctivitis and lid reactions, may occur with chronic administration of dorzolamide; discontinue therapy and evaluate patient before restarting therapy |
The exact mechanism of ocular antihypertensive action is not established, but it appears to be a reduction of aqueous humor production or inhibition of inflow.
| Drug Name | Timolol ophthalmic (Timoptic XE, Timoptic, Blocadren) |
|---|---|
| Description | May reduce elevated and normal IOP with or without glaucoma by inhibiting inflow. |
| Adult Dose | 1 gtt of 0.25% or 0.5% in affected eye(s) bid; if IOP is maintained at satisfactory levels, change dosage to 1 gtt in affected eye(s) qd; if clinical response not adequate, change dosage to 1 gtt of 0.5% solution in affected eye(s) bid; if IOP is still not at satisfactory level, consider concomitant therapy |
| Pediatric Dose | Administer as in adults |
| Contraindications | Documented hypersensitivity; bronchial asthma; sinus bradycardia; second- and third-degree AV block; severe chronic obstructive pulmonary disease; overt cardiac failure; cardiogenic shock |
| Interactions | May cause bradycardia and asystole when used in combination with systemic beta-blockers (may cause additive effects) |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Product may have sulfites, which may cause allergic-type reactions in susceptible patients; may exacerbate or precipitate heart block, asthma, chronic obstructive pulmonary disease, and mental changes (especially in elderly patients) |
| Drug Name | Levobunolol (AKBeta, Betagan) |
|---|---|
| Description | Nonselective beta-adrenergic blocking agent that lowers IOP by reducing aqueous humor production and possibly increasing outflow of aqueous humor. |
| Adult Dose | 0.5% solution: 1-2 gtt in affected eye(s) qd 0.25% solution: 1-2 gtt in affected eye(s) bid Severe or uncontrolled glaucoma: 0.5% solution bid; closely monitor patient; > 1 gtt (0.5% levobunolol) bid not shown to be more effective; if IOP not at satisfactory level on this regimen, concomitant therapy can be instituted; do not administer 2 or more topical ophthalmic beta-adrenergic blocking agents simultaneously |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; bronchial asthma; severe chronic obstructive pulmonary disease; sinus bradycardia; second- and third-degree AV block; overt cardiac failure; cardiogenic shock |
| Interactions | May cause bradycardia and asystole when used in combination with systemic beta-blockers (may cause additive effects) |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Beta-blockade may potentiate muscle weakness that is consistent with certain myasthenic symptoms (eg, diplopia, ptosis, generalized weakness); product may have sulfites, which may cause allergic-type reactions in certain susceptible persons |
| Drug Name | Betaxolol (Betoptic) |
|---|---|
| Description | Indicated for glaucoma. Selectively blocks beta1-adrenergic receptors with little or no effect on beta2-receptors. Reduces IOP by reducing production of aqueous humor. |
| Adult Dose | 1-2 gtt in affected eye(s) bid; consider concomitant therapy if IOP is not at satisfactory level |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; bronchial asthma; severe chronic obstructive pulmonary disease; sinus bradycardia; second- and third-degree AV block; overt cardiac failure; cardiogenic shock |
| Interactions | May have additive systemic effects if patient is already on systemic beta-blockers |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Beta-blockade may potentiate muscle weakness consistent with myasthenic symptoms; product may have sulfites, which may cause hypersensitivity reactions in susceptible persons |
For reduction of IOP in patients intolerant to other IOP-lowering medications or who do not respond optimally to other IOP-lowering medications.
| Drug Name | Travoprost ophthalmic solution (Travatan) |
|---|---|
| Description | Prostaglandin F2-alpha analog. Selective FP prostanoid receptor agonist believed to reduce IOP by increasing uveoscleral outflow. Used to treat open-angle glaucoma or ocular hypertension. |
| Adult Dose | 1 gtt in affected eye(s) hs; not to exceed 1 dose/d |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; signs of inflammation; pregnancy |
| Interactions | None reported |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Commonly causes ocular hyperemia; may cause permanent increase in pigment to iris (ie, increases brown pigment) and eyelid; may increase eyelash growth; may cause bacterial keratitis; caution in uveitis or macular edema; do not instill if wearing contact lenses |
| Drug Name | Unoprostone ophthalmic solution (Rescula) |
|---|---|
| Description | Prostaglandin F2-alpha analog. Selective FP prostanoid receptor agonist believed to reduce IOP by increasing uveoscleral outflow. Used to treat open-angle glaucoma or ocular hypertension. |
| Adult Dose | Instill 1 gtt in affected eye(s) bid |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; signs of inflammation |
| Interactions | None reported |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Commonly causes ocular hyperemia; may cause permanent increase in pigment to iris (ie, increases brown pigment) and eyelid; may increase eyelash growth; may cause bacterial keratitis; caution in uveitis or macular edema; do not instill if wearing contact lenses |
| Drug Name | Bimatoprost ophthalmic solution (Lumigan) |
|---|---|
| Description | A prostamide analogue with ocular hypotensive activity. Mimics the IOP-lowering activity of prostamides via the prostamide pathway. Used to reduce IOP in open-angle glaucoma or ocular hypertension. |
| Adult Dose | Instill 1 gtt of 0.03% solution in affected eye(s) hs; not to exceed 1 dose/d |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; signs of inflammation |
| Interactions | None reported |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | May cause permanent increase in pigment to iris (ie, increases brown pigment) and eyelid; may increase eyelash growth; may cause bacterial keratitis; caution in uveitis or macular edema; do not instill if wearing contact lenses |
| Drug Name | Latanoprost (Xalatan) |
|---|---|
| Description | May decrease IOP by increasing outflow of aqueous humor. |
| Adult Dose | 1 gtt (1.5 mcg) in affected eye(s) qd in evening; higher frequency administrations may decrease effectiveness |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity |
| Interactions | Coadministration with eye drops containing the preservative thimerosal may reduce effects (administer at intervals of 5 min between applications) |
| Pregnancy | B - Usually safe but benefits must outweigh the risks. |
| Precautions | Do not administer while wearing contact lenses; may increase brown pigment in iris and gradually change eye color (unknown effect) |
Article Last Updated: Jun 22, 2006
