Glaucoma Topics Flashcards
Aspects of History Relevant to Glaucoma Assessment/Referral
- Ethnicity
- POAG (afrocarribbean)
- ACG (east asian)
- Prev Ocular History
- OHT/Glaucoma
- Uveitis
- Pseudoexfoliation
- Pigment dispersion
- Myopia (>6.00DS)
- General Health Considerations
- DM
- HBP
- Peripheral vasculature disease
- Migraine
- Reynauds
- Sleep apneoa
- Medications
- Steroid use
- Family History
- 1st degree relative is higher risk
- Younger onset is more severe
Measuring IOP in accordance with SIGN Guidelines
- Measured using application tonometry
- Regular calibration needed (at least monthly)
- Is minimum of 2 readings on single occasion
When to Refer Based on IOP in accordance with SIGN Guidelines
- Consider referral if:
- IOP > 25mmHg
- IOP 21-25mmHg and CCT <555um if ages under 65
- Monitor in community if:
- IOP <26mmHg and CCT >555um with no signs of glaucoma
Measuring CCT in Accordance with SIGN Guidelines
- Increased risk if under 555um
- Record CCT, sd and the instrument used
- If sd is high then repeat measurement
- Record IOP and CCT separately and treat as separate risk factor
When to Refer Based on AC Angle in Accordance with SIGN Guidelines
- VH or gonioscopy are acceptable
- Refer irrespective of other signs if:
- VH grade 2 or less
- 270 degrees or more where pigmented TM is not visible on gonioscopy
When to Refer Based on Visual Fields in Accordance with SIGN Guidelines
- At least 2 tests with repeatable findings recommended
- One test may suffice if result is unequivocal
- Ideally same VF instrument for both tests
- No SIGN recommendation on the level of VF loss:
- If repeatable and clinically appropriate then refer
- Cluster of 3 or more points
Patients Reliability Indices on Visual Fields
- 20% False Negatives
- 20% False Positives
- 30% Fixation Losses
When to Refer Based on Optic DISC assessment in Accordance with SIGN Guidelines
- Irrespective of IOP refer if:
- Disc haemorrhage
- Cup:disc asymmetry > 0.2
Who to Monitor More Carefully
- Pigment dispersion syndrome
- Pseudoexfoliation
- Myopic disc
- Tilted disc
- VF can mimic glaucoma
- Optic disc drusen
- Family history
- OHT (still 2 year monitoring)
Angle Structures as Visible on Gonioscopy
I - Iris
Can - Ciliary Body
See - Scleral Spur
The - Trabecular Meshwork
Line - Schwalbe’s Line
What are Iris Processes
- Small tenuous extensions of the anterior iris surface
- Insert at the scleral spur
- Present in around 1/4 of individuals
- More prominent in brown eyes and children
- Peripheral anterior synechiae are more substantial and insert more anteriorly
G1 Gonioscopy Lens
- View angle by viewing mirror and rotating through 360 degrees
- Single mirror with 62 degree viewing angle
- Highest mag of common gonioscopy lenses (1.5x)
G2 Gonioscopy Lens
- Has 2 mirrors with slightly different angles, so different views of angle
- View angle by viewing in mirror and rotating through 180 degrees
- Highest mag of common gonioscopy lenses (1.5x)
G3 Gonioscopy Lens
- AKA Goldman lens
- Can be used to view peripheral angle and peripheral fundus
- Rotate through 360 degrees to view full angle
- Mag 1.06x
G4 Gonioscopy Lens
- 4 Mirrors for viewing all set at same angle
- View whole angle by using 4 mirrors and rotating 45 degrees
- Has detachable handle for stability if non-flange
- Mag is 1.0x, but can use SL mag
Advantages of Direct Gonioscopy
- Good magnification (1.5x) using SL
- Easy orientation for observer
- Possible to simultaneously compare both eyes
- Can be used in bed bound patients
- Very little corneal distortion
- Wide FOV
Disadvantages of Direct Gonioscopy
- Time consuming
- Requires large working area
- May require assistant
- Requires separate illumination and magnification
- Low magnification depending on SL
- Cannot creat optical section to locate Schwalbe’s Line
- Poor for detail deepening on SL
- Difficult technique
Advantages of Indirect Gonioscopy
- Focal illumination allows location of Schwalbe’s line
- Magnified view of angle
- Excellent for fine detail
- Stable image
- Technique is simple
- Useful for surgical treatment
- Can use ordinary SL
- Px sitting up or supine
- Photography/video possible
Disadvantages of Indirect Gonioscopy
- Poor lateral view (stereopsis difficult)
- Uncomfortable for patient?
- Can require coupling fluid
- Observations reversed
- Small FOV
- Expensive lenses
Advantages of a Non-Flange Gonioscopy Lens
- Use saline to wet lens
- No coupling fluid required
Disadvantages of a Non-Flange Gonioscopy Lens
- Less stable image
Advantages of Flange Gonioscopy Lens
- Easier to get initial image
- View is more stable
Disadvantages of Flange Gonioscopy Lens
- Needs coupling fluid (viscotears/celluvisc)
- Coupling fluid can reduce retinal image quality and impair ability to complete fields
- Cannot perform indentation gonioscopy
- Bubble formation causing issues with viewing
- Messy
Corneal Wedge
- Helps determine if angle is open or closed
- Beam is displaced 5 to 10 degrees temporally or nasally
- The tip of the wedge is Schwalbe’s Line
- If next to iris then angle is closed
- If large gap then angle is open
Indentation Gonioscopy
- Useful to help differentiate between the various pigmented structures
- Positional angle closure will open with pressure
- Synechiae angle closure will not open even with pressure
Shaffer Gonioscopy Grading
- Corresponds to VH grading
- Anterior CB (Grade 4)
- Scleral Spur (Grade 3)
- TM (Grade 2)
- None (Grade 0)
Recording Gonioscopy Results
- Most posterior visible structure
- Shaffer grade each quadrant
- Iris processes/synaechiae (extent and position)
- Pigmentation (graded 0-4)
Physiological Variations Visible on Gonioscopy
Variations in TM Pigment
- Can be physiological or due to PDS/Pseudoexfoliation
Sampolesi’s Line
- Heavy pigmentation anterior to Schwalbe’s line
- Can be normal or due to PDS/Pseudoexfoliation
Iris Processes
- Ensure they are not peripheral anterior synechiae
Pathological Variations Visible on Gonioscopy
Peripheral Anterior Synechiae
- Differentiate from iris processes
- Iris processes are more posterior
Angle Neovascularisation
- Neovascular vessels are leaky and cross structures
PDS
- Increased pigment in angle
- Visible defect on retro-illumination
- Krukenburge spindle on posterior cornea
Pseudoexfoliation
- Deposits in AC angle
- Deposits on anterior lens surface
Order of Prescribing Glaucoma Medications
1st line
- Prostaglandin analogue
2nd Line
- Beta blocker/Carbonic anhydrase inhibitor/Alpha agonist
3rd Line
As above
4th Line
- As above (rarely pilocarpine)
Prostaglandin Analogues in Glaucoma Treatment
- Mechanism
- Increases uveoscleral outflow by ciliary muscle relaxation
- Action
- 30 to 35% reduction
- Effect
- Initial effect after 2 hrs
- Peak effect after 8 to 12 hrs
- Effect duration upto 24 hrs
- Contrainidcations
- Uveitis
- CMO
- Recurrent HSK
- Relative cohtrainidaction in aphakia/pseudoaphakia
- Pregnancy
- Examples
- Latanoprost
- Travoprost
- Bimatoprost
- Tafluprost
Beta Blockers in Glaucoma Treatment
- Mechanism
- Blocks receptors on ciliary body, decreasing aqueous production
- Action
- 25 to 30% reduction
- Suffer from tachyphylaxis i.e. eventually become less effective
- Contraindications
- Arrythmias, cardiac failure, COPD
- Cautions
- Px taking calcium channel blockers
- Px already on systemic beta blockers
- Elderly px
- Examples
- Timolol
- Levobunolol
- Carteolol
- Metipranolol
- Betaxolol (cardioselective)
Carbonic Anhydrase Inhibitors in Glaucoma Treatment
- Mechanism
- Inhibit carbonic anhydrase in ciliary epithelium, reducing aqueous production
- Action
- 18% reduction
- Possible improved optic nerve perfusion due to local vasodilation
- CAI can affect metabolism of corneal endothelium so may cause loss in clarity
- Examples
- Dorzolamide
- Brinzolamide
Carbonic Anhydrase Inhibitors Side Effects
- Ocular Side Effects
- Transient stinging
- Transient blurring
- Allergy
- SPK
- Systemic Side Effects
- Sulphonamide allergy
- Stevens-Johnsons Syndrome
- Aplastic anaemia
Alpha 2 Agonists in Glaucoma Treatment
- Mechanism
- Reduces aqueous production and increases uveosleral outflow
- Action
- 25% reduction
- 4th line due to high rate of allergies
- Experimental neuroprotective properties on optic nerve
- Contraindications
- Children
- People with depression
- Examples
- Apraclonidine
- Brimonidone
Alpha 2 Agonists Side Effects
- High rate of allergy
- Conjunctival hyperaemia
- Follicular conjunctivitis
- Dry mouth
- Systemic BP reduction
- Fatigue and drowsiness
Prostaglandin Analogues Side Effects
- Mild conjunctival hyperaemia
- SPK
- Ocular irritation
- Increased iris pigmentation
- Lengthening of lashes
- CMO
- Reactivation of HSK
- Exacerbation of asthma
- Lower lid skin hyperpigmentation
Beta Blockers Side Effects
Ocular Side Effects
- Corneal hypaesthesia
- SPK
- Dry eye
- Burning/stinging
- Pseudopemphigoid
Systemic Side Effects
- Anxiety
- Depression
- Loss of libido
- Arrhythmia
- Hypotension
- Exacerbation of asthma
- Raynauds
Cholinergic Agents in Glaucoma Treatment
- Mechanism
- Increase trabecular outflow via ciliary muscle contraction and minor decrease in aqueous inflow
- Action
- 20% reduction
- Example
- Pilocarpine 1-4% 4x daily
Pilocarpine Side Effects
Ocular Side Effects
- Ciliary muscle spasm
- Brow ache
- Accommodative myopia
- Miosis (VF constriction)
- Retinal detachment
- Exacerbation of uveitis
- Cataract formation
- Angle closure
Systemic Side Effects
- Bradycardia
- Nausea
- Sweating
- Diarrhoea
- Bronchospasm
