honeypot link
skip to main content
  • follow us on facebook
  • follow us on X
MSD Manual LogoMSD ManualProfessional Version
MEDICAL TOPICSRESOURCESCOMMENTARYPROCEDURESQUIZZESABOUT US
homeMEDICAL TOPICSRESOURCES
Search icon
  1. <Medical Topics
    Ophthalmology
    Approach to the Ophthalmologic Patient
    • Evaluation of the Ophthalmologic Patient
      • History
      • Physical Examination
        • Visual acuity
        • Eyelid and conjunctival examination
        • Corneal examination
        • Pupil examination
        • Extraocular muscles
        • Ophthalmoscopy
        • Slit-lamp examination
        • Visual field testing
        • Color vision testing
      • Testing
        • Tonometry
        • Angiography
        • Optical coherence tomography
        • Electroretinography
        • Ultrasound
        • CT and MRI
    • Ophthalmic Anatomy
    Symptoms of Ophthalmic Disorders
    • Acute Vision Loss
      • Pathophysiology
      • Etiology
        • Etiology reference
      • Evaluation
        • History
        • Physical examination
        • Red flags
        • Interpretation of findings
        • Testing
        • Evaluation references
      • Treatment
      • Key Points
    • Anisocoria
      • Etiology
        • Etiology reference
      • Evaluation
        • History
        • Physical examination
        • Red flags
        • Interpretation of findings
        • Testing
        • Evaluation reference
      • Treatment
      • Key Points
    • Blurred Vision
      • Etiology
        • Etiology reference
      • Evaluation
        • History
        • Physical examination
        • Red flags
        • Interpretation of findings
        • Testing
      • Treatment
      • Geriatrics Essentials
      • Key Points
    • Diplopia
      • Etiology
      • Evaluation
        • History
        • Physical examination
        • Red flags
        • Interpretation of findings
        • Testing
      • Treatment
      • Key Points
    • Eyelid Swelling
      • Etiology
        • Etiology references
      • Evaluation
        • History
        • Physical examination
        • Red flags
        • Interpretation of findings
        • Testing
      • Treatment
      • Key Points
    • Eye Pain
      • Pathophysiology
      • Etiology
      • Evaluation
        • History
        • Physical examination
        • Red flags
        • Interpretation of findings
        • Testing
      • Treatment
      • Key Points
    • Proptosis
      • Etiology
      • Evaluation
        • Red flags
        • Testing
        • Evaluation reference
      • Treatment
      • Key Points
    • Floaters
      • Pathophysiology
        • Pathophysiology Reference
      • Etiology
      • Evaluation
        • History
        • Physical examination
        • Red flags
        • Interpretation of findings
        • Testing
      • Treatment
      • Key Points
    • Red Eye
      • Pathophysiology
      • Etiology
      • Evaluation
        • History
        • Physical examination
        • Red flags
        • Interpretation of findings
        • Testing
      • Treatment
      • Key Points
    • Tearing
      • Pathophysiology
      • Etiology
        • Increased tear production
        • Decreased nasolacrimal drainage
        • Etiology reference
      • Evaluation
        • History
        • Physical examination
        • Red flags
        • Interpretation of findings
        • Testing
      • Treatment
      • Geriatrics Essentials
      • Key Points
    • Other Eye Symptoms
      • Dry eyes
      • Eye discharge
      • Halos
      • Blue hues
      • Scotomata
      • Reference
    Cataract
    • Cataract
      • General reference
      • Etiology
        • Etiology references
      • Symptoms and Signs
      • Diagnosis
      • Treatment
      • Cataract extraction and lens implant procedures
      • Postsurgical care and complications
      • Treatment references
      • Prevention
        • Prevention references
      • Key Points
    Eyelid and Lacrimal Disorders
    • Blepharitis
      • Etiology
        • Acute blepharitis
        • Chronic blepharitis
        • Etiology reference
      • Symptoms and Signs
        • Acute blepharitis
        • Chronic blepharitis
      • Diagnosis
      • Treatment
        • Acute blepharitis
        • Chronic blepharitis
        • Treatment references
      • Prognosis
      • Key Points
    • Blepharospasm
      • General references
    • Canaliculitis
      • Etiology
        • Etiology reference
      • Symptoms and Signs
      • Diagnosis
      • Treatment
        • Treatment reference
      • Key Points
    • Chalazion and Hordeolum (Stye)
      • Chalazion
      • Hordeolum
      • General reference
      • Symptoms and Signs
        • Chalazion
        • Hordeolum
      • Diagnosis
      • Treatment
        • Chalazion
        • Hordeolum
        • Treatment references
      • Key Points
    • Dacryocystitis
      • Acute dacryocystitis
      • Chronic dacryocystitis
      • Reference
    • Dacryostenosis
      • General references
      • Diagnosis
      • Treatment
        • Treatment reference
      • Key Points
    • Entropion and Ectropion
      • Entropion
      • Ectropion
      • General reference
    • Trichiasis
    • Eyelid Growths
      • Xanthelasma
      • Basal cell carcinoma
      • Other malignant growths
      • General references
    Conjunctival and Scleral Disorders
    • Trachoma
      • General references
      • Symptoms and Signs
        • Symptoms and signs references
      • Diagnosis
        • Diagnosis references
      • Treatment
        • Trachoma control in endemic areas
        • Treatment references
      • Key Points
    • Viral Conjunctivitis
      • Etiology
        • Etiology references
      • Symptoms and Signs
        • Symptoms and signs reference
      • Diagnosis
        • Diagnosis reference
      • Treatment
      • Key Points
    • Acute Bacterial Conjunctivitis
      • Etiology
        • Etiology reference
      • Symptoms and Signs
      • Diagnosis
      • Treatment
        • Treatment reference
      • Key Points
    • Adult Inclusion Conjunctivitis
      • General references
      • Symptoms and Signs
      • Diagnosis
      • Treatment
      • Key Points
    • Allergic Conjunctivitis
      • Etiology
      • Symptoms and Signs
        • General allergic conjunctivitis
        • Seasonal and perennial conjunctivitis
        • Vernal keratoconjunctivitis
        • Symptoms and signs reference
      • Diagnosis
      • Treatment
      • Key Points
    • Subconjunctival Hemorrhages
      • References
    • Overview of Conjunctival and Scleral Disorders
      • Selected eye findings in conjunctival disorders
      • Reference
    • Ocular Mucous Membrane Pemphigoid
      • General reference
      • Symptoms and Signs
      • Diagnosis
        • Diagnosis reference
      • Treatment
        • Treatment references
      • Key Points
    • Overview of Conjunctivitis
      • General reference
      • Symptoms and Signs
      • Diagnosis
      • Treatment
        • Treatment references
      • Key Points
    • Pinguecula and Pterygium
      • Pinguecula
      • Pterygium
        • Pterygium references
    • Episcleritis
      • General reference
      • Treatment
        • Treatment reference
    • Scleritis
      • General reference
      • Symptoms and Signs
        • Symptoms and signs reference
      • Diagnosis
      • Treatment
        • Treatment references
      • Prognosis
        • Prognosis reference
      • Key Points
    Corneal Disorders
    • Cogan Syndrome
      • Reference
      • Symptoms and Signs
        • Ocular
        • Vestibuloauditory
        • Vascular
      • Diagnosis
      • Treatment
        • Treatment reference
      • Key Points
    • Introduction to Corneal Disorders
    • Bullous Keratopathy
      • Etiology
      • Symptoms and Signs
      • Diagnosis
      • Treatment
      • Key Points
    • Corneal Ulcer
      • Etiology
      • Pathophysiology
      • Symptoms and Signs
      • Diagnosis
      • Treatment
        • Treatment reference
      • Key Points
    • Herpes Simplex Keratitis
      • Symptoms and Signs
        • Primary infection
        • Recurrent infection
      • Diagnosis
      • Treatment
        • Treatment reference
      • Key Points
    • Herpes Zoster Ophthalmicus
      • References
      • Symptoms and Signs
        • Complications
      • Diagnosis
      • Treatment
      • Prevention
        • Prevention references
      • Key Points
    • Interstitial Keratitis
      • Symptoms and Signs
      • Diagnosis
      • Treatment
      • Key Points
    • Keratoconjunctivitis Sicca
      • Etiology
      • Symptoms and Signs
      • Diagnosis
      • Treatment
        • Treatment references
      • Key Points
    • Keratoconus
      • Reference
    • Keratomalacia
    • Peripheral Ulcerative Keratitis
      • References
    • Phlyctenular Keratoconjunctivitis
    • Superficial Punctate Keratitis
      • Ultraviolet keratitis
    • Corneal Transplantation
      • Indications
      • Procedure
      • Complications
      • Complications references
      • Prognosis
        • Prognosis references
      • Corneal Limbal Stem Cell Transplantation
      • Key Points
    Glaucoma
    • Overview of Glaucoma
      • References
      • Pathophysiology
        • Pathophysiology reference
      • Symptoms and Signs
      • Diagnosis
        • Screening
        • Diagnosis reference
      • Treatment
      • Key Points
    • Primary Open-Angle Glaucoma
      • Etiology
        • Etiology reference
      • Pathophysiology
        • Elevated-pressure glaucoma
        • Normal-pressure glaucoma or low-tension (low-pressure) glaucoma
      • Symptoms and Signs
        • Optic nerve appearance
        • Visual field defects
        • Pathophysiology reference
      • Diagnosis
      • Treatment
        • Medical therapy
        • Surgery
        • Treatment reference
      • Key Points
    • Angle-Closure Glaucoma
      • Reference
      • Etiology
      • Pathophysiology
        • Primary angle-closure glaucoma
        • Secondary angle-closure glaucomas
      • Symptoms and Signs
        • Acute angle-closure glaucoma
        • Chronic angle-closure glaucoma
      • Diagnosis
      • Treatment
        • Acute angle-closure glaucoma
        • Chronic angle-closure glaucoma
      • Prevention
      • Key Points
    How To Do Eye Procedures
    • How To Remove a Foreign Body From the Eye
      • Indications
      • Contraindications
      • Complications
      • Equipment
      • Additional Considerations
      • Positioning
      • Step-by-Step Description of Procedure
        • Removal of superficial foreign bodies
        • Removal of embedded foreign bodies
      • Aftercare
      • Warnings and Common Errors
      • Tips and Tricks
      • References
    • How To Irrigate the Eye and Do Eyelid Eversion
      • Indications
      • Contraindications
      • Complications
      • Equipment
      • Additional Considerations
      • Relevant Anatomy
      • Positioning
      • Step-by-Step Description of Procedure
      • Eyelid eversion
      • The scleral lens
      • Aftercare
      • References
    • How To Do Lateral Canthotomy
      • Indications
      • Contraindications
      • Complications
      • Equipment
      • Additional Considerations
      • Relevant Anatomy
      • Positioning
      • Step-by-Step Description of Procedure
      • Aftercare
      • Warnings and Common Errors
      • Tips and Tricks
      • References
    Optic Nerve Disorders
    • Compressive Optic Neuropathy
      • Etiology
        • Etiology reference
      • Symptoms and Signs
        • Symptoms and signs reference
      • Diagnosis
      • Treatment
    • The Optic Pathway
    • Hereditary Optic Neuropathies
      • Dominant optic atrophy
      • Leber hereditary optic neuropathy
      • General references
      • Symptoms and Signs
        • Dominant optic atrophy
        • Leber hereditary optic neuropathy
      • Diagnosis
      • Treatment
        • Treatment references
    • Ischemic Optic Neuropathy
      • General reference
      • Symptoms and Signs
        • Symptoms and signs reference
      • Diagnosis
        • Diagnosis reference
      • Treatment
        • Treatment reference
      • Prognosis
        • Prognosis reference
      • Key Points
    • Optic Neuritis
      • Etiology
      • Etiology references
      • Symptoms and Signs
        • Symptoms and signs reference
      • Diagnosis
        • Diagnosis reference
      • Treatment
        • Treatment references
      • Prognosis
        • Prognosis references
      • Key Points
    • Papilledema
      • General reference
      • Symptoms and Signs
      • Diagnosis
      • Treatment
      • Key Points
    • Toxic and Nutritional Optic Neuropathies
      • Etiology
        • Etiology reference
      • Symptoms and Signs
      • Diagnosis
      • Treatment
      • Prognosis
      • Key Points
    Orbital Diseases
    • Tumors of the Orbit
      • Children
      • Adults
      • General references
    • Cavernous Sinus Thrombosis
      • Etiology
        • Etiology reference
      • Pathophysiology
      • Symptoms and Signs
      • Diagnosis
        • Diagnosis references
      • Treatment
        • Treatment references
      • Prognosis
        • Prognosis reference
      • Key Points
    • Inflammatory Orbital Disease
      • Symptoms and Signs
        • Symptoms and signs reference
      • Diagnosis
      • Treatment
        • Treatment references
      • Key Points
    • Preseptal and Orbital Cellulitis
      • Etiology
        • Etiology references
      • Pathophysiology
      • Symptoms and Signs
      • Diagnosis
        • Diagnosis references
      • Treatment
        • Preseptal cellulitis
        • Orbital cellulitis
        • Treatment reference
      • Key Points
    Refractive Error
    • Overview of Refractive Error
      • Symptoms and Signs
      • Diagnosis
      • Treatment
    • Contact Lenses
      • Care and Complications
        • Care and complications references
      • Rigid Corneal Contact Lenses
      • Scleral Contact Lenses
      • Soft Hydrophilic Contact Lenses
        • Soft hydrophilic contact lenses reference
    • Refractive Surgery
      • Types of refractive surgery
        • General references
        • Laser In Situ Keratomileusis (LASIK)
        • Kerato-Lenticule Extraction (KLEx)
        • Phakic Intraocular Lenses (IOLs)
        • Photorefractive Keratectomy (PRK)
        • Clear Lensectomy/Refractive Lens Exchange (RLE)
        • Radial Keratotomy and Astigmatic Keratotomy
    Retinal Disorders
    • Age-Related Macular Degeneration (AMD or ARMD)
      • General reference
      • Etiology
      • Pathophysiology
        • Pathophysiology reference
      • Symptoms and Signs
        • Dry AMD
        • Wet AMD
      • Diagnosis
      • Treatment
        • Dry AMD
        • Wet AMD
        • Treatment references
        • Supportive measures
      • Key Points
    • Central Retinal Artery Occlusion and Branch Retinal Artery Occlusion
      • Etiology
        • Etiology reference
      • Symptoms and Signs
      • Diagnosis
      • Treatment
        • Treatment references
      • Prognosis
        • Prognosis reference
      • Key Points
    • Central Retinal Vein Occlusion and Branch Retinal Vein Occlusion
      • Etiology
        • Etiology reference
      • Symptoms and Signs
      • Diagnosis
      • Treatment
        • Treatment references
      • Prognosis
        • Prognosis reference
      • Key Points
    • Diabetic Retinopathy
      • Pathophysiology
        • Nonproliferative retinopathy
        • Proliferative retinopathy
      • Symptoms and Signs
        • Nonproliferative retinopathy
        • Proliferative retinopathy
      • Diagnosis
        • Screening
      • Treatment
      • Treatment references
      • Prevention
        • Prevention reference
      • Key Points
    • Hypertensive Retinopathy
      • Pathophysiology
      • Symptoms and Signs
      • Diagnosis
      • Treatment
      • Key Points
      • More Information
    • Retinal Detachment
      • Etiology
        • Etiology reference
      • Symptoms and Signs
      • Diagnosis
      • Treatment
        • Treatment reference
      • Key Points
    • Retinitis Pigmentosa
      • Symptoms and Signs
      • Diagnosis
      • Treatment
        • Treatment references
      • More Information
      • Key Points
    • Epiretinal Membrane
      • General reference
    • Cancers Affecting the Retina
      • Choroidal Melanoma
        • General reference
      • Choroidal Metastases
      • General reference
    Uveitis and Related Disorders
    • Uveitis Caused by Systemic Rheumatic Disease
      • Spondyloarthropathies
      • Juvenile idiopathic arthritis (JIA)
      • Sarcoidosis
      • Behçet disease
      • Vogt-Koyanagi-Harada (VKH) disease
      • Tubulointerstitial nephritis and uveitis syndrome (TINU)
      • References
    • Endophthalmitis
      • References
      • Diagnosis
      • Treatment
        • Treatment reference
    • Infectious Uveitis
      • Toxoplasmosis
      • Herpesviruses: HSV and VZV
      • Herpesviruses: Cytomegalovirus
      • References
    • Overview of Uveitis
      • General reference
      • Etiology
      • Symptoms and Signs
        • Complications
        • Symptoms and signs reference
      • Diagnosis
      • Treatment
      • Treatment references
      • Key Points
    • Sympathetic Ophthalmia
      • Reference
      • Treatment
        • Treatment reference
    MSD
    • About us
    • Disclaimer
    • Permissions
    • Privacy
    • Cookie Preferences
    • Terms of use
    • Partnerships
    • Contact Us
    • Global Medical Knowledge
    • Veterinary Manual
    • Mobile App
    • follow us on facebook
    • follow us on X
    This icon serves as a link to download the eSSENTIAL Accessibility assistive technology app for individuals with physical disabilities. It is featured as part of our commitment to diversity and inclusion.
    • follow us on facebook
    • follow us on X
    This icon serves as a link to download the eSSENTIAL Accessibility assistive technology app for individuals with physical disabilities. It is featured as part of our commitment to diversity and inclusion.
    MSD

    Copyright© 2026Merck & Co., Inc., Rahway, NJ, USA and its affiliates. All rights reserved.