Eyecare conditions, explained for professionals
Concise, evidence-based clinical overviews of the disease states that define modern ophthalmology and optometry practice. Each page pairs an authoritative summary with the latest KOL video, roundtable, and technique content from iD Social.
Reviewed by the iD Social Medical Editorial BoardCataract & Refractive
Astigmatism
Astigmatism is a refractive error in which the cornea or lens has unequal curvature across meridians, so light focuses at multiple points rather than one, blurring vision at all distances. Regular astigmatism is correctable with cylindrical lenses, while irregular astigmatism—often from corneal disease—requires specialty contact lenses. It commonly coexists with myopia or hyperopia.
Clinical overviewCataract & RefractiveCataracts
A cataract is any opacification of the crystalline lens that degrades vision, most commonly from age-related changes. It is the leading cause of reversible blindness worldwide and is treated definitively with surgical lens removal and intraocular lens (IOL) implantation. Modern phacoemulsification is among the most frequently performed and successful procedures in medicine.
Clinical overviewCataract & RefractivePresbyopia
Presbyopia is the gradual, age-related loss of the eye’s ability to accommodate and focus on near objects, resulting from stiffening of the crystalline lens and changes in the ciliary apparatus. It becomes noticeable in the early-to-mid 40s and is universal. Correction options span spectacles and contact lenses, pharmacologic miotic drops, and lens- or cornea-based surgery.
Clinical overviewCornea & Ocular Surface
Blepharitis
Blepharitis is a common, chronic inflammation of the eyelid margins that contributes substantially to ocular surface disease and dry eye. It is broadly divided into anterior blepharitis, affecting the lash base, and posterior blepharitis, involving the meibomian glands. Management centers on consistent lid hygiene and targeting the underlying inflammatory or infectious contributors.
Clinical overviewCornea & Ocular SurfaceConjunctivitis
Conjunctivitis is inflammation of the conjunctiva with viral, bacterial, allergic, and toxic causes. It is one of the most frequent reasons for acute eye visits, and distinguishing the underlying cause is essential because management differs markedly. Most acute infectious conjunctivitis is viral and self-limited, and thoughtful evaluation reduces unnecessary antibiotic use.
Clinical overviewCornea & Ocular SurfaceDry Eye Disease
Dry eye disease is a multifactorial disease of the ocular surface characterized by loss of tear film homeostasis, accompanied by ocular symptoms, in which tear film instability, hyperosmolarity, inflammation, and neurosensory abnormalities play etiological roles. It is among the most common reasons patients present to eyecare providers. Management is staged and targets the underlying subtype—aqueous-deficient, evaporative, or mixed.
Clinical overviewCornea & Ocular SurfaceFuchs’ Endothelial Corneal Dystrophy
Fuchs’ endothelial corneal dystrophy is a progressive, bilateral disorder in which corneal endothelial cells are lost and guttae accumulate on Descemet membrane, impairing the endothelium’s ability to keep the cornea dehydrated. The result is corneal edema, glare, and characteristic vision that is blurriest on waking. Endothelial keratoplasty—DMEK or DSAEK—is the definitive treatment for visually significant disease.
Clinical overviewCornea & Ocular SurfaceKeratoconus
Keratoconus is a progressive, non-inflammatory corneal ectasia in which the cornea thins and steepens into a cone-like shape, producing irregular astigmatism and reduced vision. It typically presents in adolescence or early adulthood and can progress for years. Corneal cross-linking has transformed care by halting progression, while specialty contact lenses and, when needed, corneal transplantation rehabilitate vision.
Clinical overviewCornea & Ocular SurfaceMeibomian Gland Dysfunction
Meibomian gland dysfunction (MGD) is a chronic, diffuse abnormality of the meibomian glands, commonly characterized by terminal duct obstruction and changes in glandular secretion, and it is the leading cause of evaporative dry eye disease. Because the meibomian glands supply the lipid layer that stabilizes the tear film, their dysfunction leads to accelerated evaporation, instability, and ocular surface inflammation.
Clinical overviewCornea & Ocular SurfacePterygium
A pterygium is a wing-shaped fibrovascular growth of conjunctival tissue that extends onto the cornea, strongly associated with chronic ultraviolet light and environmental exposure. It can cause irritation, redness, induced astigmatism, and, when it encroaches on the visual axis, reduced vision. Management ranges from ocular surface support to surgical excision with conjunctival autografting to lower recurrence.
Clinical overviewCornea & Ocular SurfaceUveitis
Uveitis is inflammation of the uveal tract and adjacent intraocular structures, encompassing a heterogeneous group of infectious, immune-mediated, and idiopathic conditions. It is classified anatomically as anterior, intermediate, posterior, or panuveitis. Prompt diagnosis and control of inflammation are essential because untreated uveitis is a significant cause of preventable vision loss.
Clinical overviewRetina
Age-Related Macular Degeneration
Age-related macular degeneration (AMD) is a progressive disease of the central retina and a leading cause of irreversible central vision loss in people over 50. It is divided into non-neovascular (dry) disease, marked by drusen and, in advanced form, geographic atrophy, and neovascular (wet) disease, in which choroidal neovascularization threatens rapid vision loss. Anti-VEGF therapy transformed the prognosis of wet AMD.
Clinical overviewRetinaDiabetic Macular Edema
Diabetic macular edema (DME) is the accumulation of fluid in the central retina due to breakdown of the blood–retinal barrier in diabetes, and it is the most common cause of vision loss in patients with diabetic retinopathy. It can occur at any stage of retinopathy. OCT has made diagnosis and monitoring precise, and anti-VEGF therapy is the first-line treatment for center-involving disease.
Clinical overviewRetinaDiabetic Retinopathy
Diabetic retinopathy is a microvascular complication of diabetes mellitus and a leading cause of vision loss among working-age adults. It progresses from non-proliferative changes—microaneurysms, hemorrhages, and exudates—to proliferative disease with neovascularization that risks vitreous hemorrhage and tractional detachment. Glycemic and blood pressure control plus timely screening are the foundation of prevention.
Clinical overviewRetinaGeographic Atrophy
Geographic atrophy (GA) is the advanced form of non-neovascular (dry) age-related macular degeneration, defined by sharply demarcated areas of loss of the retinal pigment epithelium, photoreceptors, and choriocapillaris. It causes progressive, irreversible loss of central vision, often sparing the fovea until late and producing dense scotomas that impair reading and face recognition. Complement inhibitors are the first therapies shown to slow GA lesion growth, though none restore vision already lost.
Clinical overviewRetinaRetinal Detachment
Retinal detachment is separation of the neurosensory retina from the underlying retinal pigment epithelium, and it is a sight-threatening emergency. The most common type is rhegmatogenous, caused by a retinal break that allows fluid beneath the retina. Prompt recognition of warning symptoms—new floaters, flashes, and a curtain-like visual field defect—and urgent referral are essential to preserve vision.
Clinical overviewRetinaRetinal Vein Occlusion
Retinal vein occlusion (RVO) is one of the most common retinal vascular disorders, caused by thrombotic obstruction of a retinal vein that leads to hemorrhage, macular edema, and, in ischemic cases, neovascularization. It is classified as branch or central depending on the site of occlusion. Vision loss most often results from macular edema, which is treated effectively with anti-VEGF therapy.
Clinical overviewGlaucoma
Pediatrics & Binocular Vision
Amblyopia
Amblyopia is reduced best-corrected vision in one or both eyes due to abnormal visual development during childhood, without a structural lesion that fully explains the loss. It is the most common cause of monocular vision impairment in children. Because the visual system is most plastic early in life, timely detection and treatment are critical to a good outcome.
Clinical overviewPediatrics & Binocular VisionMyopia
Myopia (nearsightedness) is a refractive error in which distant objects appear blurred because light focuses in front of the retina, usually due to an elongated eye. Its prevalence is rising globally, and high myopia carries lifelong risks of retinal detachment, myopic maculopathy, and glaucoma. Modern myopia management aims to slow axial elongation in children, not merely correct blur.
Clinical overviewPediatrics & Binocular VisionStrabismus
Strabismus is a misalignment of the eyes in which they do not point at the same target simultaneously, and it affects both children and adults. It can cause amblyopia and loss of binocular vision in childhood and diplopia in adults. Management ranges from refractive correction and prism to extraocular muscle surgery, depending on the type and cause.
Clinical overview