Glaucoma

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Glaucoma
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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

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Types of Glaucoma

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

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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)

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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

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Examination in Cases of Narrow/Closed Angle
Glaucoma

• Anterior segment
• Macroscopic
• hard, red eye
• cloudy cornea
• fixed, mid-dilated pupil
• Microscopic
• raised IOP (typically gt 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

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Angle closure glaucoma

• ..

• Note red eye, hazy cornea and semi-dilated pupil

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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

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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

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YAG iridotomy

• Note 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

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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

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Congenital Glaucoma

• History
• There may be a family history of congenital
  glaucoma
• Examination
• Macroscopic
• Photophobia
• Lacrimation
• Blepharospasm
• Buphthalmos (large cornea, gt 12 mm in diameter)
• Microscopic
• Raised IOP
• Cupped discs (see below)

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Picture of buphthalmos
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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

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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)

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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

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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

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Goldman tonometer

• Local 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

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Diagram of view through slit lamp of tonometry

• Undercorrected
• Overcorrected
• Correct pressure

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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

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Humphrey visual fields

• Normal visual field right eye

• Superior arcuate field loss in the left eye due
  to glaucoma

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Humphrey visual fields

• Glaucomatous 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

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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

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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.
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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

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Trabeculectomy

• Note
• cystic drainage bleb
• peripheral iridectomy

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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

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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

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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

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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

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Pseudoexfoliation

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

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Pigment Dispersion Syndrome

• Characterised by dispersion of pigment throughout
  the anterior segment
• Pigment on the corneal endothelium (known as
  Krukenbergs spindle)
• Pigment on the anterior lens surface (known as
  Scheies 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

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Pigment Dispersion Syndrome

• Note pigment on corneal endothelium

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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

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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