Glaucoma

Glaucoma = a group of maladies and conditions that impair the optic nerve and may lead to significant

vision loss or even blindness; about 2.5 million Americans have some form of glaucoma and about half of them

don’t even know that they have it; second leading cause of blindness in the U.S. and leading cause of

blindness for African-Americans

Optic nerve = responsible for transmitting visual information and signals from the retina to the brain,

where they will be interpreted

Common Symptoms

  • Open-Angle Glaucoma
    • No clear symptoms in the initial stages of this particular type of glaucoma
    • Later on, blind spots will appear in the peripheral vision
    • Usually, the blind spots will not be conspicuous until after the optic nerve hasbeen extremely impaired or the ophthalmologist diagnoses the blind spots and condition
  • Narrow-Angle Glaucoma
    • Early symptoms:
      • 1) Blurred or indistinct vision
      • 2) Headaches
      • 3) Mild pain in the eyes
      • 4) Redness in the eyes
      • 5) Seeing halos around lights
  • Later symptoms (may also appear in the early stages of this type of glaucoma)
    • 1) Sharp pain in the eyes or brows
    • 2) Redness in the eyes
    • 3) Indistinct vision
    • 4) Seeing halos or colored rainbows around lights
    • 5) Headaches
    • 6) Nausea and/or Vomiting
  • Normal-Tension Glaucoma
    • Damage to the optic nerve
    • Blind spots in the peripheral vision
  • Ocular Hypertension
    • Abnormally high pressure in the eyes
    • May not co-occur with glaucoma symptoms
    • Also called “glaucoma suspects”

Risk Factors

  • Open-Angle Glaucoma
    • Those of African or Hispanic ancestry (especially Mexican-Americans)
      • The risk for African-Americans increases after the age of 40
  • Nearsightedness (or its more extreme form, myopia)
  • Narrow-Angle Glaucoma
    • Those of Asian or Inuit ancestry
    • Farsightedness (or its more extreme form, hyperopia)
  • Hereditary = family history of glaucoma may lead to the passing of the condition to children andfuture descendants
  • Advanced Age (over 50 years)
  • Elevated pressure in the eyes (greater than 21 mm Hg (mercury))
  • History of injury or damage to the eyes
  • Thinner central cornea (s)
  • Refraining from having routine eye examinations according to the recommendations of theophthalmologist
  • Usage of certain steroid medications, including prednisone
  • Any of those conditions that affect blood flow:
    • 1) Low blood pressure
    • 2) Migraines
    • 3) Diabetes

Causes

  • Elevated Eye Pressure
    • Also known as intraocular pressure (IOP)
    • A clear fluid known as the aqueous humor flows in and out of the anterior chamber(between the lens and cornea) to stabilize the eye pressure and nourish any tissues that are nearby
    • The aqueous humor flows out through a small drain called the trabecular meshwork
      • This drain is comprised of a complex network of cells and tissuesin the area called the drainage angle
  • Glaucoma is directly caused by the improper flow of aqueous humor through the trabecularmeshwork
  • Open-Angle Glaucoma
    • The aqueous humor flows out of the trabecular meshwork too slowly
    • This leads to a backup of the fluid, which consequently causes a slow but steadyrise in the intraocular pressure
    • It is called open-angle glaucoma because the angle between the various structureswithin the eye (s) appears to be open
    • This is the most common type of glaucoma that is experienced
  • Narrow-Angle Glaucoma
    • The aqueous humor is prevented from flowing due to a complete blockage of thedrainage angle
    • This leads to a rapid increase in the IOP and subsequently a narrow-angle glaucomaattack with the severe pain in the eye (s) and brows, nausea, and vomiting
    • This attacks constitutes a medical emergency that must be treated immediately
  • Normal (Low) Tension Glaucoma
    • Those who have this form of glaucoma have eye pressures at levels that areregularly below 21 mm Hg
    • Even so, those people will still have impaired optic nerves and blurred vision orloss of vision
  • Congenital Glaucoma
    • This is a rare form of glaucoma that is contracted by infants and youngchildren
    • This is caused by an incorrect or improper development of the drainage systemwithin the eye (s) before birth
    • It may be hereditary in nature
  • Secondary Glaucoma
    • This type of glaucoma is caused by another co-occurring or pre-existing malady inthe eye (s)
    • There are several diseases that may cause this form of glaucoma:
      • 1) Injury to or in the eye (s)
      • 2) Inflammation
      • 3) Blockage of the blood vessels in the retina
      • 4) Formation of abnormal blood vessels due to diabetes
      • 5) The use of medications that contain steroids, including pills,eyedrops, sprays, and others
      • 6) Tumors
      • 7) Long-term steroid therapy
      • 8) Pigment dispersion
        • Small particles from within the iris calledgranules may circulate within the aqueous humor
        • This can cause the blockage of the trabecularmeshwork

Diagnosis

  • Eye Charts
    • The patient will be asked to look at and identify letters at certain distances withone eye open and the other closed
    • This helps test for visual acuity and clarity
  • Tonometry
    • This procedure is meant to test the levels of eye pressure being experienced
    • First, the eyes are anesthetized with eyedrops
    • Then, an instrument called the tonometer is used to measure how the cornea resistspressure within the eyes
    • Normal levels of eye pressure read in the range of 10 to 21 mm Hg
    • Air tonometry involves the insertion of a puff of air as a means of measuring theeye pressure levels
    • Another type of tonometry utilizes a plastic prism that gently pushes against theeye as a means of measuring the IOP
  • Gonioscopy
    • This procedure involves the inspection of the drainage angle within the eye (s)
    • It can’t be properly examined through a mere surface level examination of theeye (s)
    • A mirrored lens is used to look at the drainage angle as a means of differentiatingbetween the different types of glaucoma
  • Ophthalmoscopy
    • The pupils are dilated so as to allow the effective usage of the ophthalmoscope tomagnify and more thoroughly examine the retina and optic nerve
    • It is the color and appearance of the optic nerve that determines how much damage,if any, is present
      • The change in appearance of the optic nerve is called cupping andits progression leads to the appearance of blank spots within the field of vision
  • Perimetry
    • This is also called the visual field test
    • A patch will be temporarily applied to one of the eyes to allow for each eye to beindividually tested
    • The patient will be seated and asked to look straight ahead at some specifiedtarget
    • The computer being used will make a noise and random points of light will flasharound the bowl-shaped instrument called the perimeter
    • The patient is to press a button whenever he/she sees a light
      • Not every noise that the computer makes will be followed by alight
  • This method checks for blank spots within the field of vision, especially those that the patientmay not notice
  • This testing is done every 6 to 12 months to check for any changes
  • Pachymetry
    • Corneal thickness plays a role in the measurements of eye pressure
    • A probe called a pachymeter is lightly placed onto the cornea as a means ofmeasuring the thickness of the cornea

Treatment

  • There is no cure for glaucoma
    • Treatment is meant to mitigate and control the effects of glaucoma, as well as toavoid or retard any other damage to vision
  • Medication
    • Eyedrops
      • These are the most common treatment method for glaucoma
      • They serve to lower the levels of eye pressure in one of twodifferent ways:
        • 1) Retarding the production of the aqueoushumor
        • 2) Improving the flow of the aqueous humor throughthe drainage angle
    • The eyedrops should be taken daily or according to the schedule recommended by theophthalmologist
    • Neither the dosage of medication should be changed nor should the medication not betaken without consulting the ophthalmologist first
    • The ophthalmologist can take of any necessary refills upon request
    • The ophthalmologist should be informed of any and all medications that the patientis currently taking
    • In the same vein, the primary physician should be informed of any and all glaucomamedications that the patient is currently taking
  • Surgery
    • Surgical treatment serves to improve the flow of the aqueous humor out of eye andthrough the drainage angle in order to lower the levels of eye pressure
    • Laser Trabeculoplasty
      • This method is usually used to treat open-angle glaucoma
      • There are two types:
        • 1) Argon Laser Trabeculoplasty (ALT)
          • The laser makes small and evenlyspaced burns within the trabecular meshwork
          • This will not generate any moredrainage holes, but rather stimulate the trabecular meshwork to work more efficiently
      • 2) Selective Laser Trabeculoplasty (SLT)
        • A low-level energy laser targets specific cellswithin different channels in the trabecular meshwork with the usage of very short applications of light
        • This lowers the levels of eye pressure to ratessimilar to those associated with ALT
  • Even when this method is successful, most patients who have glaucoma continue taking theirmedications afterwards
  • Many patients who have had a successful treatment will go back to it again
  • About half of those patients who have used laser trabeculoplasty will notice increased levels ofeye pressure within the next five years
  • This is an alternative for those who are unwilling and/or unable to take the eyedrops
  • Laser Iridotomy
    • This method is used to treat those patients who have narrow-angle glaucoma
    • The laser creates a small hole through the top part of the iris in order to improvethe flow of the aqueous humor out and into the drainage angle
  • Peripheral Iridectomy
    • This is to be used when laser iridotomy is unsuccessful in treating an acutenarrow-angle glaucoma attack or cannot be used for other reasons
    • A small portion of the iris is taken so as to let the aqueous humor flow out andinto the drainage angle again
    • Most cases of narrow-angle glaucoma can be successfully treated with eyedrops orlaser iridotomy, rendering peripheral iridectomy rarely necessary and a last resort option of sorts
  • Trabeculectomy
    •  Firstly, a small flap is made in the sclera
    • Then, a reservoir is made underneath the conjunctiva, which is the thin and filmymembrane covering the sclera
      • The reservoir takes the shape of a bump or blister on the part ofthe sclera above the iris and is covered by the upper eyelid
  • The aqueous humor is now able to be drained through the flap and collected in the reservoir,wherein the aqueous humor will be absorbed into the blood vessels in the surrounding areas within the eye
  • This method has proven to be effective in three out of four people who have used it
  • Many who have had successful treatments no longer have to use the medicated eyedrops, althoughfollow-up appointments with the ophthalmologist are still necessary
  • In those cases in which the new drainage channel created closes or there is an excess of aqueoushumor being drained from the eye, further surgery may be obligatory to fix this new problem
  • Aqueous Shunt Surgery
    • This is an alternative to trabeculectomy and has also proven to be quiteeffective
    • An aqueous shunt is a small and plastic valve that is connected on one end to areservoir
    • It is embedded into the eye through a small incision
    • It acts as an artificial drainage valve of sorts by transmitting the aqueous humorto an area underneath the conjunctiva so that it can be absorbed by the neighboring blood vessels
    • The reservoir cannot be easily seen after having healed unless the patients looksdownward and lifts the eyelid