Glaucoma

Intraocular pressure and aqueous humor

• The intraocular pressure (IOP) of an eye is determined by the balance of its aqueous production (which occurs in the ciliary body) and its aqueous outflow (which occurs through the angle of the eye) [link to anatomy lecture]

• The normal IOP is between 10 and 20 mmHg

Types of Glaucoma

• Narrow/closed angle glaucoma– Attributable to restricted outflow of aqueous humor through the

eye’s outflow channel (the angle of the eye, which contains the trabecular meshwork)

• Open angle glaucoma– “A characteristic form of optic neuropathy, with some regard to

intraocular pressure (IOP)”– this is the only definition which holds true for all types of open

angle glaucoma

Narrow/closed angle glaucoma

• In this type of glaucoma, the outflow channel for aqueous humor is either dramatically reduced (when the angle is narrow, but open) or blocked completely or almost completely (when the angle is closed)

• Prevalence of 1 in 1000 persons over 40 years of age

• Risk factors for narrow/closed angle glaucoma– Female gender– Hypermetropia (these eyes are smaller, and have narrower

drainage angles)

History in Cases of Narrow/Closed Angle Glaucoma

• Symptoms of raised IOP– headache– nausea– vomiting

• Symptoms of corneal oedema (which occurs as a result of raised IOP)– reduced vision– haloes– photophobia

• Of note, the onset (i.e. suddenness) and the severity of symptoms relate to the degree of angle narrowing/closure and the consequential rise in IOP

Examination in Cases of Narrow/Closed Angle Glaucoma

• Anterior segment– Macroscopic

• hard, red eye• cloudy cornea• fixed, mid-dilated pupil

– Microscopic• raised IOP (typically > 40 mmHg)• some inflammatory cells in the anterior chamber• shallow anterior chamber

• Posterior segment– Typically a poor view– Glaucomatous optic neuropathy, if the condition has

been present for some time

Angle closure glaucoma

Note red eye, hazy cornea and semi-dilated pupil

• ..

Management of Narrow/Closed Angle Glaucoma

• The management of narrow/closed angle glaucoma is urgent, and involves 3 steps

• Step 1: Normalise IOP in the acute phase– Lie the patient supine (to deepen the anterior chamber)– Instil pupil-constricting drops, pilocarpine, (these will open the angle, if scarring in the angle

has not yet occurred)– Topical steroids (to treat any inflammatory component)– Other topical anti-glaucoma medications, including:

• Beta-blockers• Alpha agonists• Prostoglandin analogues

– Systemic anti-glaucoma agents:• Oral

– Acetozolamide (reduces production of aqueous)• Intravenous

– Acetozolamide – Mannitol (a hyperosmotic agent)

– Which of these agents are required is a case-by-case decision based on the severity of the particular case in question, and on the response to these measures by careful monitoring of IOP

Management of Narrow/Closed Angle Glaucoma

• Step 2: Manage the other eye– Typically, the fellow eye will also suffer from, or be predisposed to, narrow/closed angle

glaucoma, and should be treated on its own merits

– Usually, however, prophylactic measures are all that is required for the fellow eye, including:

• Pupil-constricting drops

• YAG iridotomy (see below)

• Step 3: Prevent further episodes, and manage IOP in the long-term– Create a pathway for the aqueous to flow directly from the posterior chamber (i.e. where the

aqueous is produced) to the angle of the eye, by creating a peripheral iridotomy with a YAG laser (after the cornea has cleared); occasionally, a surgical iridectomy is required for this;

– In a substantial proportion of cases, and because of damage to the drainage angle during the acute episode, long-term anti-glaucoma measures will be required, including:

• Anti-glaucoma drops• Sometimes, glaucoma filtration surgery will be required

YAG iridotomyNote red reflex coming through iridotomy holes in iris

Red reflex also visible around pupil due to iris atrophy

Opacity in pupil is posterior capsular thickening post cataract surgery. This is treated by cutting a hole in the capsule with a Yag laser

Open Angle Glaucoma

• Congenital/infantile/paediatric– 40% congenital, 55% within first 2 years of life– congenital and infantile forms are attributable to developmental abnormality of

trabecular meshwork

• Acquired– primary– secondary

• To ocular abnormalities– pseodoexfoliation– pigment dispersion– aniridia

• To ocular disease– lens capsule perforation (lens-induced) [link]– phacomorphic [link]– trauma– uveitis

• To drugs– Steroids, especially topical steroids

Congenital Glaucoma

• History– There may be a family history of congenital glaucoma

• Examination– Macroscopic

• Photophobia• Lacrimation• Blepharospasm• Buphthalmos (large cornea, > 12 mm in diameter)

– Microscopic• Raised IOP• Cupped discs (see below)

Picture of buphthalmos

Management of Congenital Glaucoma

• The management is surgical, and will consist of:– Goniotomy or trabeculectomy

• Complications of surgery and co-existing ocular pathology (e.g. cataracts) mean that the long-term visual prognosis is poor in many cases

– Long-term anti-glaucoma drops may also be required

Primary Open Angle Glaucoma (POAG)

• “a characteristic form of optic neuropathy, with some regard to intraocular pressure”

• Such a definition is required because some patients can have glaucoma in the presence of normal IOP (known as normal tension glaucoma) and some people can have high IOP but not develop glaucoma (known as ocular hypertension)

POAG

• Affects 1 in 200 people over 40 years of age, and 1 in 10 over 80 years of age

• It is a “silent” disease, and is therefore often diagnosed quite late

• More common and more severe in black people

• A family history of POAG is associated with increased risk of the condition

History, Examination and Investigations

• History– In non-advanced disease, the patient is typically asymptomatic– There may be a family history of glaucoma– History of ocular trauma?

• Examination– IOP

• IOP is measured by Goldmann applanation tonometry, and should be corrected for corneal thickness (thicker corneas yield higher readings, and thinner corneas yield lower readings)

– Look for ocular disease or abnormalities that can cause secondary glaucoma• Pseuodexfoliation• Pigment dispersion• Swollen or perforated lens• Signs of trauma• Uveitis

– Gonioscopy• This involves the use of a special lens to grade the degree to which the drainage angle is open

• Investigations– Visual field analysis (see below)– Neuro-imaging

• Very rarely indicated, and only where unexplained optic neuropathy is seen in conjunction with visual field loss, but where a diagnosis of glaucoma is doubtful; in these circumstances, images of the optic chiasm are advisable;

Goldman tonometerLocal anaesthetic plus fluorescein drops are instilled in the eyes.

The tonometer prism touches the cornea

The dial is turned until the two green semi circles just touch.

Intra ocular pressure is then read measured in mmHg,

Patients must be warned not to rub their eyes for 15 to 20 minutes after drops are instilled

Diagram of view through slit lamp of tonometryUndercorrected

Overcorrected

Correct pressure

Visual Fields

• Glaucoma results in loss of visual field, and visual acuity is only affected in the end-stage of uncontrolled disease

• Diagnosis and/or progression of glaucoma is typically assessed using static perimetry, such as the Humphrey Visual Field Analyser

Humphrey visual fields

Normal visual field right eyeSuperior arcuate field loss in the left eye due to glaucoma

Humphrey visual fieldsGlaucomatous field loss

Markedly restricted peripheral fields- tunnel vision- left eye worse than right

Left eye normal. Right- marked superior arcuate and lesser inferior arcuate field loss

Diagnosis of Primary Open Angle Glaucoma (POAG)

• The diagnosis of POAG is made on a case-by-case basis, based on the following:

– Visual field– IOP– Appearance of optic nerve head (optic disc)– Family history

• Of these, the appearance of the optic nerve head is the most important parameter

– The optic nerve head (ONH), also known as the optic disc, is made up of a pink neuroretinal rim and of a central pale optic cup

– The neuroretinal rim is made up of nerve fibres derived from the nerve fibre layer of the retina, whereas the optic cup is that part of the ONH which does not contain nerve fibres

– In glaucoma, there is loss of nerve fibres, and therefore the optic cup enlarges and the neuroretinal rim becomes thinner, and this is known as pathological optic nerve cupping or glaucomatous optic neuropathy

– some people have a large optic cup, but in the presence of a healthy neuroretinal rim, and this is known as physiological cupping

Normal disc on left and cupped disc on rightnote increased area of pallour and the bending of the blood vessels at

the disc margin in the cupped disc.

Management of Primary Open Angle Glaucoma

• The aim of management is to lower the IOP

• Medical management by use of one or more anti-glaucoma medications, and in the context of regular IOP and ONH checks, and monitoring of visual fields

– Topical anti-glaucoma preparations• Prostaglandin analogues (reduce production, and increase outflow, of aqueous)• Beta-blockers (reduce production of aqueous)• Alpha-agonists (enhance outflow of aqueous)• Carbonic anhydrase inhibitors (reduce production of aqueous)• Miotics (enhance outflow of aqueous)

– Oral anti-glaucoma preparations• Carbonic anhydrase inhibitors (for short-term use only)

• Surgical management– Trabeculectomy– Reserved for a minority of cases where the condition progresses in spite of

maximal tolerable therapy

TrabeculectomyNote

cystic drainage bleb

peripheral iridectomy

POAG

Uncontrolled glaucoma leads to blindness

POAG can be controlled but not cured

Any damage to the optic nerve prior to diagnosis cannot be reversed

POAG needs lifelong follow up and treatment

Normal Tension Glaucoma

• Normal tension glaucoma simply refers to a condition characterised by glaucomatous optic neuropathy and loss of visual field, but in the presence of normal IOP measurements

• If there is doubt about the diagnosis, neuro-imaging of the optic chiasm should be undertaken

• The management is precisely the same as that of POAG, but aiming for a lower target IOP

Ocular Hypertension

• Ocular hypertension (OHT) is characterised by high IOP, but in the absence of glaucomatous optic neuropathy or field loss

• Patients with OHT are at increased risk of developing glaucoma, and therefore should be closely monitored

• There is some evidence to suggest that IOP reduction in patients with OHT reduces the risk of developing glaucoma

Secondary Glaucomas

• Pseudoexfoliaton (PXF)– A condition common amongst those of Scandinavian

origin or descent, and therefore common in Irish people

– Characterised by the accumulation of grey-white basement membrane material on the pupil edge and on the lens capsule

– If pseuodoexfoliation causes glaucoma, it is known as glaucoma capsulare

– PXF also causes cataract– Glaucoma capsulare is managed in precisely the

same manner as POAG

PseudoexfoliationNote white deposit on anterior lens capsule at periiphery and also just outside the margin of the pupil before it was dilated.

Pigment Dispersion Syndrome

• Characterised by dispersion of pigment throughout the anterior segment– Pigment on the corneal endothelium (known as Krukenberg’s

spindle)– Pigment on the anterior lens surface (known as Scheie’s stripe)– Loss of pigment from the iris, with consequential iris

transillumination

• When pigment dispersion syndrome causes glaucoma, it is known as pigmentary glaucoma

• Pigmentary glaucoma is managed in precisely the same way as POAG

Pigment Dispersion SyndromeNote pigment on corneal endothelium

Aniridia

• Congenital absence of the iris

– Associated with foveal hypoplasia– Glaucoma typically develops in late childhood– Managed in the same way as POAG, but the

need for surgery is likely

Glaucoma secondary to ocular disease

• Lens-induced glaucoma [link]• Phacomorphic glaucoma [link]• Uveitis [link]• Trauma

– Blunt trauma can cause damage to the drainage angle (known as angle recession), which can cause glaucoma at the time of injury, or months or years later

• The management of all secondary glaucomas involves the treatment of the underlying cause (e.g. treating the inflammation if it is secondary to uveitis) and management of IOP as for POAG