Ophthalmology Final

Diabetic Retinopathy (DR)

• Most common cause of impaired vision worldwide in the working-age group.

• Pathophysiology: Microangiopathy due to chronic hyperglycemia -> vessel leakage, ischemia.
  • Loss of pericytes, thickening of basement membrane.

• Non-Proliferative DR (NPDR)
  • Signs:
    • Microaneurysms (earliest sign)
    • Dot-and-blot hemorrhages
    • Hard exudates
    • Cotton-wool spots (nerve infarctions, also seen in HTN)
    • Venous beading
    • Intraretinal microvascular abnormalities (IRMA)
  • Severity Assessment (NPDR):
    • Mild: Microaneurysms only.
    • Severe: (4-2-1 Rule) - Microaneurysms in 4 quadrants OR Venous beading in 2 quadrants OR IRMA in 1 quadrant.

• Proliferative DR (PDR)
  • Cause: Progressive retinal ischemia -> VEGF release -> abnormal new vessel growth.
  • Hallmark: Neovascularization (NVD - on disc, NVE - elsewhere, NVI - on iris).
  • Complications: Vitreous hemorrhage, tractional retinal detachment, neovascular glaucoma.
  • Treatment: Pan-retinal photocoagulation (PRP), Anti-VEGF injections.

• Diabetic Macular Edema (DME)
  • Most common cause of decreased vision in patients with DR.
  • Cause: Vascular leakage leading to retinal thickening/swelling at the macula.
  • Can occur at any stage of DR (NPDR or PDR).
  • Treatment: Anti-VEGF injections, focal/grid laser photocoagulation.

• Management Principles:
  • Non-proliferative with macular edema: Treat macular edema (e.g., Anti-VEGF).
  • Proliferative DR: Treat with PRP +/- Anti-VEGF.

• Risk Factors:
  • Duration of DM (most important)
  • Poor glycemic control
  • Hypertension (HTN)
  • Nephropathy
  • Pregnancy

Glaucoma

• Definition: Group of diseases causing characteristic optic neuropathy (optic disc cupping) and characteristic visual field defects, +/- increased Intraocular Pressure (IOP).

• Primary Open-Angle Glaucoma (POAG)
  • Most common type of glaucoma.
  • Often asymptomatic until late stages.
  • Signs: Open iridocorneal angle on gonioscopy, progressive peripheral visual field loss, characteristic optic disc cupping.
  • Treatment Aim: Lower IOP (medications - e.g., prostaglandin analogs first line, laser, surgery).

• Angle-Closure Glaucoma (ACG)
  • Mechanism: Peripheral iris obstructs the trabecular meshwork (TM).
  • Acute Angle-Closure Glaucoma (AACG):
    • Ophthalmic emergency.
    • Symptoms: Sudden painful vision loss, halos, nausea/vomiting.
    • Signs: High IOP, corneal edema, mid-dilated pupil, shallow anterior chamber.
    • Treatment: Lower IOP immediately (IV Acetazolamide, topical beta-blockers, osmotic agents like Mannitol), Topical Pilocarpine (miotic - after IOP lowers), Laser Peripheral Iridotomy (definitive).
  • Chronic Angle-Closure Glaucoma: Gradual angle closure, scarring, fewer symptoms initially, presents later with vision loss/optic nerve damage.
  • Angle closure can be precipitated by pupillary dilation (e.g., contraindicated cycloplegics like atropine).

• Congenital Glaucoma
  • Presents early, often within the first year.
  • Cause: Improper development of aqueous outflow structures (TM).
  • Signs: Buphthalmos (enlarged eye), large corneal diameter, corneal clouding, excessive tearing (epiphora), photophobia.
  • Treatment: Surgery.

• Secondary Glaucoma
  • Neovascular Glaucoma: Can result from PDR (NVI).

• Diagnosis:
  • Tonometry (IOP measurement, normal 10-21 mmHg, but not required for Dx).
  • Gonioscopy (visualize angle).
  • Fundoscopy (assess optic disc cupping).
  • Perimetry (visual field testing).

Cataract and Cataract Surgery

• Definition: Opacification of the crystalline lens.

• Symptoms: Gradual blurring of vision.

• Signs: Lens opacity, absent red reflex (in mature/dense cataract).

• Types: Nuclear, Cortical, Posterior Subcapsular, Mature, Hypermature.

• Treatment: Surgery (lens extraction and intraocular lens - IOL - implantation).
  • Phacoemulsification: Most common method, small incision, earliest visual rehabilitation.
  • Extracapsular Cataract Extraction (ECCE): Larger incision.
  • Intracapsular Cataract Extraction (ICCE): Rarely performed now.

• Cataract Surgery Complications:
  • Posterior Capsular Opacification (PCO): Most common complication.
    • Symptoms: Blurred vision months to years post-op.
    • Treatment: Nd:YAG laser capsulotomy.
  • Endophthalmitis:
    • Serious intraocular infection. Ophthalmic emergency.
    • Presents days post-op (usually 3rd-5th day) with pain, decreased vision, redness, hypopyon.
    • Most common organism: Staphylococcus epidermidis.
    • Treatment: Intravitreal antibiotics +/- vitrectomy.
  • Cystoid Macular Edema (CMO): Weeks post-op, painless vision drop.
  • Retinal Detachment (RD): Increased risk, especially if posterior capsule ruptures.
  • Suprachoroidal Hemorrhage: Rare, serious intraoperative complication.
  • Iris Prolapse.
  • Incorrect IOL power / Refractive surprise.

• Note: Leukocoria (white pupil) can be caused by cataract, but is a sign, not a complication of surgery.

Uveitis

• Definition: Inflammation of the uveal tract (iris, ciliary body, choroid).

• Classification:
  • Anterior: Iris and/or ciliary body (Iritis, Iridocyclitis).
  • Intermediate: Vitreous.
  • Posterior: Choroid and/or retina (Choroiditis, Chorioretinitis).
  • Panuveitis: All parts involved.

• Symptoms:
  • Anterior: Pain, photophobia, redness, blurred vision.
  • Posterior/Intermediate: Blurred vision, floaters, less pain/redness.

• Signs:
  • Anterior: Ciliary injection, Keratic Precipitates (KPs) on endothelium (fine or "mutton-fat"), cells and flare in anterior chamber, hypopyon (severe), posterior synechiae (iris to lens), PAS (peripheral anterior synechiae - iris to cornea/TM -> glaucoma), miosis.
  • Intermediate: Vitreous cells/haze ("snowballs," "snowbanking").
  • Posterior: Retinal/choroidal lesions, vasculitis, optic disc edema.

• Causes/Associations:
  • Anterior Uveitis: Often Idiopathic. Associated with HLA-B27 conditions (Ankylosing Spondylitis), JIA, Sarcoidosis, Herpes.
  • Posterior Uveitis: Toxoplasmosis (most common cause). Also CMV (in HIV), Sarcoidosis, Syphilis, TB.
  • Systemic Disease: Sarcoidosis (bilateral anterior uveitis, posterior uveitis - "candle wax drippings"), JIA (often asymptomatic "white eye" anterior uveitis in oligoarticular type, risk of cataract/glaucoma), Crohn's disease, Behcet's disease.

• Complications: Cataract, Glaucoma, Cystoid Macular Edema (CMO), Synechiae, Retinal Detachment.

• Treatment:
  • Corticosteroids: Topical (anterior), Periocular/Intravitreal injections, Systemic (posterior/severe/bilateral).
  • Cycloplegics/Mydriatics: (e.g., cyclopentolate) for anterior uveitis to prevent posterior synechiae and relieve ciliary spasm/pain.
  • Treat underlying cause if identified.

Cornea and External Disease

• Anatomy: Transparent, avascular. Layers (anterior to posterior):
  • Epithelium (stratified squamous, regenerates)
  • Bowman's Layer (acellular, does not regenerate well - scars)
  • Stroma (90% of thickness, collagen lamellae, keratocytes)
  • Descemet's Membrane (basement membrane of endothelium, regenerates)
  • Endothelium (single layer, hexagonal cells, does not regenerate - cell density decreases with age/disease, maintains dehydration via pump)
  • Function: Major refractive component (approx. 2/3 of eye's power). Diameter ~11.5mm horizontal.

• Keratoconus:
  • Progressive thinning and conical protrusion of the cornea.
  • Causes irregular myopic astigmatism (most common cause of vision loss in KC).
  • Signs: Central thinning, Vogt's striae, Fleischer ring (iron), Munson's sign, hydrops (acute rupture of Descemet's - painful edema).
  • Management: Stop eye rubbing, Rigid Gas Permeable (RGP) contact lenses, Corneal Cross-Linking (CXL), Intrastromal corneal rings (ICRS), Corneal Transplant (PK/DALK). LASIK is contraindicated.

• Corneal Dystrophies: Inherited, bilateral disorders.
  • Stromal Dystrophies: Cause corneal opacity due to deposits.
  • Endothelial Dystrophies (e.g., Fuchs): Cause corneal edema due to endothelial pump failure -> vision loss.

• Corneal Transplantation (Keratoplasty):
  • Indications: Keratoconus, Pseudophakic Bullous Keratopathy (PBK) (most common indication worldwide/developed countries), corneal scarring, dystrophies, infections.
  • Types: Penetrating (PK - full thickness), Lamellar (DALK, DSEK/DMEK - partial thickness).
  • Complications: Rejection, astigmatism, infection (endophthalmitis), glaucoma, cataract.

• Keratitis (Corneal Inflammation):
  • Acanthamoeba Keratitis:
    • Protozoan, found in soil/water. Risk factor: Contact lens wear (especially with tap water exposure).
    • Symptoms: Severe pain disproportionate to signs.
    • Signs: Pseudodendrites, radial keratoneuritis (pathognomonic), ring infiltrate/abscess.
    • Treatment: Prolonged course of anti-amoebic agents (e.g., PHMB, chlorhexidine), not pyrimethamine. Topical antibiotics for superimposed bacterial infection.
  • Herpes Simplex Virus (HSV) Keratitis:
    • Epithelial: Dendritic ulcer (stains with fluorescein). Treatment: Topical antivirals.
    • Stromal/Endothelitis: Requires steroids + antiviral cover.
  • Herpes Zoster Ophthalmicus (HZO): VZV in V1 distribution. Hutchinson's sign (tip of nose) indicates higher ocular involvement risk. Can cause keratitis, uveitis, neurotrophic issues. Treatment: Systemic antivirals.

• Chemical Injury:
  • Ophthalmic emergency.
  • Immediate copious irrigation is the first step.
  • Alkali burns are generally worse than acid burns (penetrate deeper).

Refractive Errors and Optics

• Refractive Power: Cornea (~43D, 2/3 total power) + Lens (~20D, 1/3 total power).

• Accommodation: Ability to increase eye's focus for near vision, achieved by contraction of the ciliary body/muscle, relaxing zonules, allowing lens to become more convex. Decreases with age (Presbyopia).

• Emmetropia: No refractive error, light focuses on retina.

• Ametropia (Refractive Errors):
  • Myopia (Nearsightedness): Light focuses in front of retina (long eye/too much power). Corrected with concave (minus) lenses.
  • Hypermetropia (Farsightedness): Light focuses behind retina (short eye/too little power). Corrected with convex (plus) lenses. Can lead to accommodative esotropia, angle-closure glaucoma risk.
  • Astigmatism: Cornea has different curvatures in different meridians, light focuses at multiple points. Corrected with cylindrical lenses.
  • Presbyopia: Age-related loss of accommodation. Corrected with reading glasses (convex lenses).

Orbital Conditions

• Orbital Walls: Roof (Frontal), Floor (Maxilla, Zygomatic, Palatine), Medial (Ethmoid, Lacrimal, Sphenoid, Maxilla - thinnest), Lateral (Zygomatic, Sphenoid - strongest). Nasal bone is not part of orbit.

• Blowout Fracture: Trauma causes fracture of orbital walls.
  • Most common sites: Floor (Maxillary sinus) and Medial wall (Ethmoid sinus).
  • Signs: Diplopia (especially on upgaze due to inferior rectus/oblique entrapment), restricted eye movements, infraorbital nerve anesthesia (floor fracture), subcutaneous emphysema (medial wall fracture).
  • Enophthalmos (sunken eye) is a late sign, not early.
  • Surgery indicated for significant entrapment or large fractures causing enophthalmos.

• Orbital Cellulitis:
  • Infection posterior to orbital septum. Serious, potential vision/life threat.
  • Cause: Often sinus infection spread (ethmoid). Common pathogens: Strep, Staph.
  • Signs: Proptosis, painful/restricted eye movements, decreased vision, fever, eyelid edema/erythema, conjunctival hyperemia/chemosis.
  • Must differentiate from Preseptal Cellulitis (infection anterior to septum, typically no proptosis, normal EOMs/vision).
  • Management: Hospital admission, IV antibiotics. CT scan to assess sinuses/abscess.

• Thyroid Eye Disease (TED):
  • Autoimmune disorder affecting orbital tissues (muscles, fat). Associated with Graves' disease (hyperthyroidism), but can occur in eu/hypothyroid states.
  • Most common cause of unilateral or bilateral proptosis in adults.
  • Smoking is major risk factor.
  • Signs: Proptosis, lid retraction, lid lag, restrictive myopathy (diplopia, inferior rectus most commonly affected -> restricted upgaze), optic neuropathy (compressive).

• Orbital Tumors:
  • Children: Capillary hemangioma (most common benign), Rhabdomyosarcoma (most common primary malignant).
  • Metastasis Source in Children: Retinoblastoma, Neuroblastoma (sympathetic chain), others.

• Carotid-Cavernous Fistula (CCF): Abnormal connection between carotid artery and cavernous sinus. Can occur post-trauma. Signs: Pulsatile proptosis, orbital bruit, chemosis, dilated conjunctival vessels, increased IOP.

Neuro-Ophthalmology

• Visual Pathway & Field Defects: Lesions produce predictable field defects.
  • Optic Nerve: Monocular vision loss / ipsilateral field defect.
  • Optic Chiasm: Bitemporal hemianopia (e.g., pituitary adenoma).
  • Optic Tract: Contralateral homonymous hemianopia (often incongruous).
  • Optic Radiation: Contralateral homonymous hemianopia or quadrantanopia (more congruous). Left radiation lesion -> right hemianopia.
  • Visual Cortex: Contralateral homonymous hemianopia, often with macular sparing.

• Pupils:
  • Relative Afferent Pupillary Defect (RAPD): Sign of unilateral or asymmetric optic nerve disease (e.g., optic neuritis) or extensive retinal disease. Detected by swinging flashlight test.
  • Light-Near Dissociation: Pupils constrict better to near stimulus than light (e.g., Argyll Robertson pupil - syphilis).

• Ptosis (Drooping Eyelid):
  • Causes:
    • Neurogenic: Third nerve palsy, Horner's syndrome (sympathetic dysfunction - mild ptosis, miosis, anhydrosis).
    • Myogenic: Myasthenia gravis.
    • Aponeurotic: Dehiscence of levator aponeurosis (age-related).
    • Mechanical: Tumor, swelling.
    • Congenital.
  • Facial nerve (7th) palsy does NOT cause ptosis (causes inability to close eye - lagophthalmos).

• Optic Neuritis: Inflammation of the optic nerve.
  • Often associated with Multiple Sclerosis.
  • Symptoms: Subacute vision loss, pain on eye movement, dyschromatopsia (impaired color vision).
  • Signs: RAPD, visual field defect. Fundoscopy often normal (retrobulbar neuritis - no disc swelling), but papilledema can occur (papillitis).

• Cranial Nerve Palsies:
  • Third Nerve (Oculomotor): Eye deviates "down and out," ptosis, pupil dilation (if parasympathetics involved).
  • Fourth Nerve (Trochlear): Vertical diplopia worse on contralateral gaze and head tilt towards affected side (superior oblique paralysis).
  • Sixth Nerve (Abducens): Inability to abduct eye (lateral rectus paralysis), horizontal diplopia worse on gaze towards affected side.
  • Seventh Nerve (Facial): Facial muscle weakness, inability to close eye (lagophthalmos), brow ptosis, epiphora. Does not cause upper lid ptosis.

Strabismus and Amblyopia

• Strabismus: Misalignment of the eyes.
  • Esotropia: Eye turns inward.
  • Exotropia: Eye turns outward.
  • Hypertropia: Eye turns upward.
  • Hypotropia: Eye turns downward.

• Esotropia Causes:
  • Accommodative Esotropia: Most common cause in children < 1 year old. Associated with hypermetropia. Treat with glasses.
  • Infantile Esotropia: Presents within first 6 months, large angle, often requires surgery. Not associated with hypermetropia. Ocular fixation assessment and fundoscopy are important.
  • Sixth Nerve Palsy.
  • Refractive error (hypermetropia).

• Amblyopia ("Lazy Eye"): Reduced visual acuity in one or both eyes due to abnormal visual development during childhood.
  • Causes:
    • Strabismic: Misaligned eye is suppressed.
    • Refractive: Unequal refractive error (anisometropia) or high bilateral error.
    • Deprivation: Obstruction of vision (e.g., congenital cataract, ptosis, corneal opacity, upper lid hemangioma).
  • Treatment: Correct underlying cause (e.g., glasses, cataract surgery), Patching the better eye to force use of the amblyopic eye. Patching is treatment, not a cause.

• Assessment: Visual acuity, cover/uncover test, alignment measurement, cycloplegic refraction, fundoscopy (to rule out pathology like retinoblastoma).

Eyelid Disorders

• Blepharitis: Eyelid margin inflammation.
  • Signs: Redness, scaling ("dandruff"), crusting, thick Meibomian secretions, lash loss (madarosis).

• Entropion: Inward turning of eyelid margin.
  • Causes: Age-related (involutional - orbicularis weakness/override), cicatricial (scarring, e.g., trachoma).
  • Symptoms: Foreign body sensation, irritation, tearing (epiphora) due to lash abrasion.

• Ectropion: Outward turning of eyelid margin.
  • Causes: Age-related (involutional - lid laxity), cicatricial, paralytic (7th nerve palsy), mechanical.
  • Symptoms: Tearing (epiphora), dryness, irritation. Does not involve medial canthal weakness specifically in this context.

Miscellaneous Ocular Conditions

• Leukocoria (White Pupil):
  • Requires urgent evaluation to rule out serious pathology.
  • Differential Diagnosis: Retinoblastoma, Congenital Cataract, Coats' disease, Retinopathy of Prematurity (ROP), Persistent Fetal Vasculature (PFV), Ocular toxocariasis. Gout is not a cause.

• Hyphema: Blood in the anterior chamber.
  • Cause: Usually trauma, can be spontaneous (neovascularization, tumor). Source is often iris or ciliary body vessels.
  • Complications: Increased IOP, corneal blood staining, re-bleeding (often worse than initial bleed, typically days 2-5).
  • Management: Rest, shield, head elevation, monitor IOP. Avoid miotics like Pilocarpine.

• Hypopyon: Layer of white blood cells (pus) in the anterior chamber. Sign of severe inflammation (e.g., endophthalmitis, severe uveitis, infectious keratitis).

• Lacrimal System:
  • Lacrimal gland located in supero-lateral orbit.
  • Tears drain via puncta -> canaliculi -> lacrimal sac -> nasolacrimal duct -> inferior nasal meatus.
  • Congenital Nasolacrimal Duct Obstruction: Common cause of infant tearing, often resolves spontaneously, may require massage/probing/surgery.

• Red Reflex: Assessed with ophthalmoscope. Should be present and clear. Absence/abnormality indicates media opacity (e.g., cataract, corneal scar, vitreous hemorrhage, tumor like retinoblastoma).

• Fuchs Heterochromic Iridocyclitis: Chronic, mild uveitis with iris heterochromia (affected eye lighter), fine KPs, associated with cataract and glaucoma.