Glaucoma Flashcards
Explain/Describe Glaucoma in Laymans Terms
Glaucoma is best described as high pressure in the eye that causes damage to the optic nerve. The optic nerve is the large nerve that sends visual information from the eye to the brain. High pressure causes damage to this nerve over time. Glaucoma is a very slow process that usually has no real symptoms other than peripheral vision loss that may go unnoticed until far advanced. Diagnosis is made by measuring the eye pressure, examining various risk factors such as family history and corneal thickness, and by measuring actual damage with optic nerve scans (such as OCT) and visual field testing. Treatment is focused on lowering eye pressure with topical eye drops, laser therapy (SLT), and even surgical treatment (trabeculoplasty or tube-shunt). Most people have chronic open-angle glaucoma and develop visual problems slowly over time. A minority suffer from acute glaucoma and develop acute pain, blurry vision, and extremely high eye pressure. If glaucoma goes unchecked, it will lead to permanent vision loss and even blindness.
What are some of the relevant history questions that should be asked for a glaucoma suspect?
- Vision? Peripheral or central? Distortion? No abnormalities? Pain?
- History of Trauma? ( Linked with Angle Recession) Hyphema? (Blood settled in anterior chamber)
- High Risk Medications? (Steroid use?)(Long term corticosteroids use? - causes increased outflow resistance, increasing IOP)
- Diabetes? (patients are twice as likely to develop POAG)
- Cold hands or Feet? Do they change color? (Peripheral Vasospasm - Raynauds Phenomenon has been linked to NPG )
- Hyper/hypo- tension? (Strong link between Hypertension and POAG)
- (to consider) Age - Caucasian over 50 y/o and African descended people over 40 y/o are at higher risk
- (to consider) Race- Asians have higher risk for ACG, African descended people high risk for POAG
- History of Smoking?
- Family History - 3-5x higher risk if 1st degree relative has glaucoma.
- Myopia? 2-5x greater risk Hyperopia? risk factor for ACG
What Examinations/Tests need to be done for the diagnosis of Glaucoma
- Taking an extended History. Look for signs of Secondary Glaucoma
- Preliminary Tests - Pupils for RAPD - 1/3 of glaucoma pxs have an RAPD and is more commonly associated with higher VF loss.
- IOP
- Slit Lamp
- VH
- Gonioscopy
- AC assessment ( PDG or PXG )
- Pupil Examination (PDG or PXG
- Optic Nerve Head Assessment (Dilated - After IOP has been checked)
- RNFL Assessment
- OCT (anterior and posterior)
- Pachymetry (CCT)
- Perimetry
If suggested
- Colour Vision Testing (If suspecting neurological)
- Contrast Sensitivity
Pseudoexfoliative Glaucoma (PXG) is most common in what ethnicity group?
Scandinavian
What is the difference between Pseudoexfoliative Glaucoma (PXG) and Pigment Dispersion Glaucoma (PDG) ?
Both are Secondary types of Glaucoma.
PXG is when a person has a disorder called Pseudoexfoliation (PXF) where a fibrillar proteinacious substance is deposited both systemically and within ocular tissue. The majority of ocular deposits occur on the anterior lens capsule where pupillary movement leads to dispersion of the material and iris pigment into the trabecular meshwork, causing an decrease in outflow and increase in IOP. This is also an INDEPENDENT risk factor for glaucoma.
Pigment Dispersion Syndrome (PDS) is where the pigmented posterior iris rubs against the lens zonules with subsequent dispersion of pigment onto the corneal endotheluim (Krukenberg spindle) and into the trabecular meshwork. PDS occurs in patients with a deep anterior chamber and/or backwards bowing of the iris, The resulting reduction in aqueous outflow may result in a rise in IOP and secondary pigment dispersion glaucoma (PDG). Approximately 20% of patients with PDS will progress to PDG. Typical patients are younger (age 30-50 years), male and myopic.
What are the specific things you are looking for when doing a DFE or Undilated Slit Lamp Assessment?
- Cup to Disc Ratio (with respect to dIsc size and Insertion)
- Cup to Disc Ratio Asymmetry (>0.2 difference more suspicious)
- Neuroretinal Rim Thinning (Thinning, focal narrowing or notching of the neuroretinal rim typically in the superior and inferior poles of the optic nerve head indicative of glaucoma)
- Optic Disc Haemorrhage (Drance)
- Blood Vessels (bayoneting or baring)
- Retinal Nerve Fiber Layers ( defect in the superior or inferior nerve bundles sign of potential glaucoma)
- Peripapillary Atrophy ( Zone Beta PPA , represents loss of retinal pigment epithelium and choriocapillaris leaving intact choroid vasculature.)
What is the Normal Range for Central Corneal Thickness (CCT) and how does this effect IOP accuracy?
Average corneal thickness is 535 to 545 microns. Thinner corneas tend to underestimate IOP, whereas thicker corneas
tend to overestimate IOP.
Revise the severity gradings for Glaucoma
= High Risk Ocular Hypertension (OHT)
- CCT less than 555 microns, IOP greater than 26mmHg, Age greater than 60, Larger C/D ratio and a Higher
Pattern Standard Deviation (PSD)
- OHTS calculator states an OHT px is at 15% chance of developing POAG in 5 years
= Pre-Perimetric Glaucoma
- 3 or more structural signs of the disease (ONH/GCC/RNFL/BV etc) with NO visual field defects.
=Early Perimetric Glaucoma
- 3 or more structural signs of the disease (ONH/GCC/RNFL/BV etc) with repeatable visual field defect (Humphrey Mean Deviation (MD) 0 to -6 dB)
=Moderate Perimetric Glaucoma
- 3 or more structural signs of the disease (ONH/GCC/RNFL/BV etc) with repeatable visual field defect (Humphrey Mean Deviation MD -6 to -12 dB) and NOT within 5 degrees of fixation by standard automated perimetry.
=Severe Perimetric Glaucoma
- 3 or more structural signs of the disease (ONH/GCC/RNFL/BV etc) with severe repeatable visual field defect (Humphrey Mean Deviation MD worse than -12 dB) or any defect WITHIN 5 degrees of fixation by standard automated perimetry.
OHTS Risk Calculator uses what findings to determine risk of Glaucoma Development AND over what time period?
AGE PRESSURE (avg) CCT (avg) VERTICAL CUP TO DISC RATIO (avg) PATTERN STANDARD DEVIATION (avg)
The OHTS risk calculator, calculates the risk of developing POAG in 5 years.
What are the IOP targets for each type of severity?
= High Risk Ocular Hypertension (OHT)
- 20% reduction in IOP
= Pre-Perimetric Glaucoma
- 20% reduction in IOP
=Early Perimetric Glaucoma
- 25% reduction in IOP
=Moderate Perimetric Glaucoma
- 30% reduction in IOP
=Severe Perimetric Glaucoma
- Lower than 14mmHgWhat extra percentage reduction in IOP is warranted if progression is still seen?
Evidence of repeatable progression at any severity stage mandates greater IOP reduction of another 10% over the existing target IOP.
What are the different types of treatment options for glaucoma, according to Optometry Australia?
- Topical Eye Drop Therapy
- Selective Laser Trabeculoplasty (SLT)
- Ciliary Body Ablation (injecting a drug that is toxic to the ciliary body - where the aqueous humour is made, and therefore production is stopped)
- Surgery : Laser Trabeculectomy, Tube Shunt
- Minimally Invasive Glaucoma Surgery (MIGS)
When would SLT be more advantageous than Topical Eye Drop Therapy?
- Early use of SLT can be advantageous in PXG or PDG
- If Pxs have allergies or contraindications to the use of certain classes of drugs
- when compliance and adherence to topical therpay is poor
What is the difference between a Selective and Non Selective Beta Blocker?
A Selective Beta Blocker like Betaxolol, only acts selectively on B1 receptors. B1 receptors are primarily in the heart and therefore there is less side effects when using a Selective Beta Blocker.
A Non-Selective Beta Blocker such as Timolol acts on both B1 and B2 receptors, causing systemic side effects such as bronchospams and bradycardia
What are the TWO First order Medication treatment for Glaucoma? Its MoA, Side Effects and Contraindications?
- Prostaglandin Analogues,
- MoA - Increase Aqueous Outflow- Side Effects - Increase Iris Pigmentation - Lengthening of Eyelashes - Conjunctival Hyperaemia -Contraindications - Intraocular Inflammation (Uveitis, Iritis) - History of Aphakia (lens removal -Catarct surgery) - Hitosry of HSK - Beta Blockers
- MoA - Decrease in Aqueous Production- Side Effects - Blurred Vision - Decreased corneal Sensitivity - Bradycardia (slow heart rate) - Hypotension - Bronchospasm - Contraindication - Bradyarrhythmia - Asthma
