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.
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.
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.
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).
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).
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.