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Major Ocular Diseases

Notes

Major Ocular Diseases

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Ocular Pathologies Tutorial

To learn about additional ocular pathologies, such as myopia, presbyopia, uveitis, etc..., see the Ocular Pathologies whiteboard tutorial.

Conjunctivitis

Overview

Basic Pathogenesis

Conjunctival inflammation of the the inner eyelids (the tarsal conjunctiva) and the sclera (the "white of the eye", which is the bulbar conjunctiva).

Etiology

Conjunctivitis can be secondary to a variety of causes, which we divide into infectious and non-infectious.

Infectious Causes

Bacterial conjunctivitis

  • Prominent feature is purulent "mucus" consistency discharge (yellow, green, or white).
  • Unilateral or bilateral in distribution. 7 – 10 day course.
  • Key bacteria include -
    • Adults: Staphylococcus aureus (and less often Streptococcus pneumoniae, Haemophilus influenzae).
    • Children: Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis.
    • Contact Wearers: Pseudomonas aeruginosa is a notable cause. As well, be aware that the risk of Acanthamoeba keratitis (a vision-threatening infection) is increased by contact use.

Trachoma

  • Chlamydia trachomatis, the worldwide leading infectious cause of blindness, is a keratoconjunctivitis secondary to recurrent Chlamydia trachomatis infection. The infection typically occurs in children in endemic areas via direct or indirect transmission of ocular or nasal secretions (the microorganism collects on a person's fingers, on an inanimate object (fomite), or on a fly and is transmitted to another individual's eyes).
  • Note that trachoma manifests as active conjunctivitis (active trachoma) and ultimately can result in conjunctival scarring (cicatricial disease), which is secondary to recurrent infection and a type 4 hypersensitivity response (cell-mediated delayed hypersensitivity).

Viral conjunctivitis

  • Adenoviral conjunctivitis is the prominent cause (~ 75% of cases).
  • Typically, part of an adenovirus infection with a upper respiratory infectious prodrome.
  • Copious, watery, mucoserous discharge with a "gritty" feeling in one eye and then the other eye becomes symptomatic within 1-2 days.
  • Highly contagious (transmissible).

NON-Infectious Causes

Allergic Conjunctivitis

  • Airbone allergens induce a type I IGE-mediated hypersensitivity response.
  • Bilateral pink (more-so than red) appearance.
  • "Velvety thickening" and Giant papillae on the inner eyelid, giving a cobblestone appearance.
  • Burning, itching, irritation, worsens with eye rubbing.

Toxic, Mechanical, or Chemical Conjunctivitis

  • Irritant-induced.
  • Typically, self-limited.

For further details regarding Conjunctivitis, Trachoma, and HSV keratitis, see: Conjunctivitis.

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Corneal Abrasion

Definitions

Corneal abrasion refers to a defect on the corneal surface due to mechanical trauma but is often used more widely to encompass any defect on the cornea (regardless of etiology).

Corneal laceration refers to a cut into the cornea (deeper than an abrasion).

Corneal ulceration refers to a corneal epithelial defect that progresses into the stroma and can ultimately involve the full thickness of the cornea.

Descemetocele refers to herniation of the Descemet's membrane through the corneal defect or a bulging forward of Descemet's membrane. Typically surrounded by a cicatricial ring. See: EyeRounds.org for examples of a descemetocele and an accompanying cicatricial ring.

Cataracts

Overview

A cataract is an opacification of the ocular lens. Cataracts are painless but can lead to blindness if not treated. In fact, cataracts are the number one preventable cause of blindness worldwide, especially in areas with poor access to cataract surgery.

Pathogenesis

Age-Related Changes

The crystalline lens is made up of crystallin proteins, which accrue defects over time via age-related changes (eg, oxidation, post-translational modifications, accumulation of fluorescent chromophores, etc…). These defects produce opacities, which disturb the passage of light detection to the retina.

In addition to opacification, lens protein defects lead to rigidity (decreased elasticity) and compaction in the central (nuclear) region of the lens, called nuclear sclerosis. This loss of flexibility results in a failure to accommodate, and thus presbyopia (impairment in far vision).

Non-Age Related Changes

There are numerous additional causes beyond age-related changes that produce cataracts. They include, but are not limited to:

  • Trauma
  • Toxic causes: tobacco, alcohol, sunlight exposure (UV-B exposure),
  • Genetic factors in general and specific genetic disorders (eg, myotonic dystrophy, Wilson's disease, galactosemia)
  • Diabetes mellitus and metabolic syndrome
  • Opportunistic infections
  • Iatrogenic causes: steroids, phenothiazines, topical anticholinesterases, post ocular-radiation therapy.

Clinical Presentation

Symptoms

Painless, progressive visual disturbance with a variable symptom progression involving issues such as:

  • Inability to focus on close-up objects (inability to read fine print), called presbyopia
  • Glare of oncoming headlights
  • Trouble reading road signs

Classifications

The primary classifications of cataract are nuclear sclerotic, cortical, and posterior subcapsular. We illustrate the location of these cataracts in the accompanying diagram (to help with visual organization) but for details about their etiology and differing presenting symptoms, refer to the American Academy of Ophthalmology article on cataracts.

Management

Cataract surgery is common and effective. Phacoemulsification is an ultrasound technique that breaks the cataract into small particles that can be aspirated out. Other techniques exist including manual extracapsular cataract extraction (ECCE).

Beyond removing the cataract, intraocular lens (IOL) placement is also performed during the cataract surgery to improve the ultimate visual outcome.

Got to Cataracts for further details about the clinical presentation, signs, and key pathogenesis of cataracts.

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Glaucoma

Overview

Definition

Glaucoma is a disorder of increased intraocular pressure (IOP)-induced optic neuropathy. There are a few different forms of glaucoma, different causes of increased ocular pressure, namely, open-angle and closed-angle (both have primary and secondary forms), as well as developmental. The "angle" refers to the iridocorneal angle of the anterior chamber of the eye.

In open-angle glaucoma, there is either excess aqueous production or insufficient outflow. Either way, pressure builds, which ultimately compresses the optic nerve head.

  • In angle-closure glaucoma, there is narrowing (or complete closure) at the iridocorneal angle.
  • Developmental glaucoma is a disorder of infancy and childhood.

Prevalence & Morbidity

  • The most common causes of blindness are cataracts, glaucoma, age-related macular degeneration (especially in Whites), and diabetic retinopathy.

Glaucoma Pathophysiology

  • In angle-closure glaucoma, there is apposition of key anterior structures, which trap the flow of aqueous humor.
    • For instance, there can be abutment of the lens and iris or the iris and the cornea, with resultant fluid obstruction.
  • In open angle glaucoma, fluid flows freely in between the iris and lens but its reabsorption is blocked via poor uptake at the trabecular meshwork or canal of Schlemm, such as from uveitis.

Glaucoma

Open-Angle Glaucoma

Symptoms

  • In open-angle glaucoma, patients are typically asymptomatic. It is not painful, does not cause eye redness, and it does not impact central vision until late-stage.

Signs

  • The eye, itself, appears normal in open-angle glaucoma.

Ophthalmologic Evaluation

Intraocular Pressure

  • Intraocular pressure is typically elevated (> 21 mmHg) but may be normal (8 – 21 mmHg).
    Fundoscopic Exam
  • Glaucoma produces the following findings on fundoscopic exam (but exam may be normal): optic disc thinning, hollowing-out of the optic nerve, called "cupping", alteration of the optic cup shape, or disc rim notching: a useful value to suggest glaucoma is when the cup is > 50% of the diameter of the vertical disc.

Angle-Closure Glaucoma

Symptoms

  • If the intraocular pressure rises slowly, patients may be asymptomatic but if there is rapid development of angle-closure glaucoma, patients can have any of the following symptoms:
    • Intense eye pain (pain in V1 distribution).
    • Nausea and vomiting.
    • Vision impairment/obscuration with halos around lights, rainbows, blurring and even transient loss of vision.

Signs

  • Typically, only one eye is affected (it is unilateral). Sudden increase in intraocular pressure can produce:
    • Conjunctival injection ("bloodshot eye" -- redness/conjunctival vessel engorgement).
    • Corneal cloudiness/haziness can be seen.
    • The pupil can be mid-dilated (4 – 6 mm diameter pupil) and react poorly to light.
    • Forward bowing of the iris with a resultant shallow anterior chamber.

Ophthalmologic Evaluation

Intraocular Pressure

  • Patients may or may not demonstrate increased intraocular pressure (IOP > 21 mmHg) at the time of evaluation.
    Fundoscopic Exam
  • Do not dilate the eye.
  • Cupping (see above), may or may not be present.
    Gonioscopy
  • Gonioscopy is a slit-lamp exam using a special lens and is the gold standard diagnostic method for diagnosing glaucoma.

Image References

Overview

Age-related macular degeneration (ARMD) refers to an acquired degeneration of the retina with characteristic findings of drusen (yellow protein and lipid-rich extracellular deposits), retinal pigment abnormalities, and retinal atrophy (geographic atrophy).

If choroid neovascular membrane formation is present ("leaky capillaries") then the disease is referred to as "wet" or exudative or neovascular.

The majority of ARMD, however, is "dry" or nonexudative or nonneovascular disease -- there is no neovascularization.

Risk Factors

  • Age
  • White race (European descent)
  • Family history
  • Light irides
  • Female gender
  • Atherosclerotic risk factors
    • tobacco abuse, hypertension, hypercholesterolemia, obesity

Clinical Presentation

We might assume central visual acuity would be a reliable indicator of disease severity but, in fact, central visual acuity may be preserved early in the disease and poorly correlates with disease severity.

Although visual acuity is often gradually affected, a worrisome reality is that visual acuity can be suddenly affected in this disorder.

Patients complain usually complain of blurred or distorted vision, or ill-defined abnormalities.

Diagnosis

Diagnosis is confirmed using fluorescein angiography and optical coherence tomography (OCT).
See classic choroidal neovascular membrane in age-related macular degeneration via:

Clinical Management

Clinical management involves risk factor modification, antioxidant and mineral supplementation, complement factor inhibition (eg, pegcetacoplan and avacincaptad pegol) and anti-VEGF treatment for wet macular degeneration.

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Diabetic Retinopathy

Diabetic Retinopathy

  • Diabetic retinopathy is a significant cause of blindness due to chronic hyperglycemia in combination with high blood pressure. It divides into nonproliferative and proliferative forms.

Glucose Abnormalities

  • May worsen in pregnancy and other conditions (eg, steroid use) when blood glucose control is impaired.

Prevention & Management

  • Prevention and management involves control of blood glucose and pressure.
  • Screen all patients with diabetes annually/pregnant patients every trimester.
  • See below regarding proliferative retinopathy management: (anti-VEGF drugs), panretinal laser photocoagulation, vitrectomy.

Diabetic macular edema (DME)

  • Diabetic macular edema refers to edema at the macula (the site of central vision). It can occur at any stage of diabetic retiniopathy (nonproliferative or proliferative) and is a key cause of loss of vision.

For high yield Q&A on diabetic retinopathy, see:

Stages of Diabetic Retinopathy

Nonproliferative diabetic retinopathy (NDR)

  • Increased capillary permeability with hemorrhages (dot/blot hemorrhages), microaneurysms, exudates, macular ischemia and retina thickening from leaked capillary fluid.
  • Look for: capillary microaneurysms, hard or soft exudates, dot and blot retinal hemorrhages.
    • Hard exudates: Yellow particles that suggest chronic edema.
    • Soft exudates (aka, cotton-wool exudates): white/fuzzy-looking areas that represent ares of microinfarction of the nerve fiber layer.
  • Treat edema with antivascular endothelial growth factor drugs, focal laser, intraocular corticosteroid implants, or vitrectomy.

Proliferative retinopathy

  • Ischemia stimulates retinal cell release of vascular endothelial growth factor (VEGF) release to stimulate growth of blood vessels.
  • Neovascularization at the vitreous surface of the retina can lead to vitreous hemorrhage and neovascularization in the anterior segments of the eye can lead to glaucoma.
  • Preretinal fibrous tissue can develop and lead to retinal detachment.
  • Patients may present with complaints of blurred vision/floaters/flashing lights with sudden vision loss.
  • Treat with antivascular endothelial growth factor drugs, panretinal laser photocoagulation, vitrectomy.

Image Reference

Diabetic Retinopathy

Giant Cell Arteritis

Overview

Giant cell arteritis (aka temporal arteritis or Horton disease) is a granulomatous disease with multi-focal arteritis of large arteries (thoracic aorta, subclavian artery, axillary artery, external carotid artery) that affects elderly individuals (especially women > 55 years-old of northern European descent).

Symptoms

Common symptoms include:
– Scalp tenderness (raised, tender temporal artery)
– Vision loss via optic neuropathy.
– Neck and/or jaw pain (jaw claudication, especially with chewing).
– Tongue necrosis (typically unilateral but bilateral can occur).

Epidemiology

Giant cell arteritis is most common in women over 55 years of age of Northern European descent. It is associated with polymyalgia rheumatica in up to 50% of cases.

Diagnosis & Management

  • Serious complications include aortic aneurysm, stroke, and blindness.
  • Elevation in ESR (Erythrocyte Sedimentation Rate) and other inflammatory markers are used to support a clinical suspicion of temporal arteritis.
  • Importantly, high-dose steroids (60 - 80 mg per day) should NOT be delayed awaiting temporal artery biopsy (IV methylprednisolone is often used at the time of diagnosis).
  • Temporal artery biopsy will still be reliable after initiation of steroids.

Summary

In summary, the histopathology of giant cell arteritis is characterized by multi-focal segmental panarteritis with:

  • Chronic inflammation.
  • Granuloma formation.
  • Destruction of the tunica media and elastic laminae.
  • Tunica intima remodeling and hyperplasia.
  • Luminal occlusion – which, as we've seen, can lead to downstream ischemia and tissue damage.

For additional information about temporal arteritis pathophysiology, see: Giant cell arteritis (temporal arteritis).

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Papilledema

Overview

Papilledema (optic disc edema) occurs due to increased intracranial pressure (ICP) from various etiologies. The "papilla" is another word for optic nerve head (the site of entry of the optic nerve into the back of the eye).

Symptoms

Headache is typically a prominent feature of increased intracranial pressure. The headache severity and quality depends on the underlying etiology. For instance, in idiopathic intracranial hypertension (pseudotumor cerebri), the headache pain, itself, may not be terribly severe but there are other characteristic features (eg, washing machine sound) that accompany the headache.

The full symptom complex found in papilledema directly depends on the underlying etiology. For instance, in meningitis-induced increased intracranial pressure, patients can progress to coma (and death); whereas, idiopathic intracranial hypertension can cause severe visual impairment but does not cause coma and is not fatal.

Because the papilledema, by definition, begins with expansion of visual "blind spot" (the visual field that references the optic disc), patients are typically unaware of the visual loss until it is fairly severe.

Signs

Optic disc edema on fundoscopic exam is the definition of papilledema. It's important to know, however, that the development of disc edema can lag behind the development of increased ICP. And, conversely, the disc edema will persist for a period of time after the ICP is brought back to normal.

Expansion of the visual blind spot can be detected on visual field testing at the bedside and confirmed with formal visual field testing.

For more information on the pathogenesis and complexities of papilledema, see Optic Disc Edema and Elevated Intracranial Pressure (ICP): A Comprehensive Review of Papilledema

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