WEEK 10 - GLAUCOMA

Question 1

Visual System Overview = 7

Answer 1

1. • Eyes to visual cortex
2. • RETINA - Cells transduce light into neural signals
3. • OPTIC NERVE - Axons of retinal ganglion cells
     innervate brain regions
4. • PULVINAR - Visuomotor behaviours
5. • LATERAL GENICULATE NUCLEUS- Main recipient of
     RGC axons in humans.
     -Output and feedback from visual cortex

6.* SUPERIOR COLLICULUS - Orientating sensory input
with visual input
-Larger RGC input in mice/rats

7 * VISUAL CORTEX - Primary cortical region of brain that receives, integrates and processes visual information

Question 2

EYE -LIGHT TRANSDUCTION PROCESS = 8

Answer 2

1. light entry through clear outer layer - cornea
2. pupil adjustment via PUPIL - Controlled by IRIS
3. LENS FOCUS LIGHT
4. photoreceptor activation in back of eye
   - rod = BW, Low light levels
   - cones = different wavelengths of light, detect colour
   Light hits these photoreceptors, causing a chemical change in a molecule called retinal within the photopigments (rhodopsin in rods and photopsins in cones).
5. Phototransduction Cascade:

• The chemical change in retinal activates a protein called opsin.
• This activation triggers a cascade of biochemical reactions, leading to a change in the electrical charge of the photoreceptor cell.
• The key steps include:
  Activation of the G-protein transducin.
• Activation of phosphodiesterase (PDE), which breaks down cGMP.
• Reduction of cGMP levels leads to the closure of sodium channels.
• This causes hyperpolarization of the photoreceptor cell, reducing neurotransmitter release.

6. Signal Transmission:

• The change in neurotransmitter release from photoreceptors alters the activity of bipolar cells in the retina.
• Bipolar cells then transmit the signal to ganglion cells.

7. Optic Nerve Transmission:

• Ganglion cells send their axons through the optic nerve to the brain.

8. Brain Processing:

• The optic nerve transmits the electrical signals to the visual cortex in the brain, where they are interpreted as images.

Question 3

Understanding what happens in the Retina : 6

Answer 3

1. RODS - DEPOLARISE IN ABSENCE OF STIMULI
   - ‘light closes Na+ channels, hyperpolarising’ cell
2. CONES - RESPOND TO WAVELENGTHS OF LIGHT FOR COLOUR VISION (PHOTOPIC)
3. HORIZONTAL CELL - Integrate and regulate photoreceptor input
4. BIPOLAR CELL - RELAY INPUTS
5. AMACRINE CELL - RESPOND TO AND INFLUENCE RGC ACTIVITY
6. ‘GANGLION CELL’ - RETINAL OUTPUT TO OPTIC NERVE

Question 4

HISTORY OF GLAUCOMA = 5

Answer 4

1. Glaucoma used by Hippocrates in Greece in 400BC to describe dimming of vision
2. • Possibly linked to the Greek word ‘glaukos’ meaning cataract or latin word ‘glauca’, meaning bluish green or grey.
3. Inability to visualise the posterior of the eye in the living person
4. • Light source, mirrors and lenses
5. • Why do some eye seem to shine red or give off light?

Question 5

History = Development of the first* ophthalmoscope by Hermann von Hemholtz in 1851 = 3

Answer 5

1. • Axis of illumination and observation is the same, allowing visualisation of interior eye
2. • Hemholtz first scope had only one concave lens
3. • Strong stable illumination

Question 6

History - Imaging of the posterior of the eye was possible = 2

Answer 6

1. • Retina, vasculature, optic disc, etc.
2. • Characterisation of eye diseases

Question 7

HISTORY =First detailed by the German ophthalmologist ‘Albrecht von Graefe’ = 3

Answer 7

1. • Lead the adoption of the ophthalmoscope
2. • Graefe’s Archive for Clinical and Experimental Ophthalmology
3. • Followed Adolf Weber’s proposal of glaucoma as a “pressure excavation”

Question 8

Etiology OF GLAUCOMA = 8

Answer 8

1. • The leading cause of global irreversible blindness
2. • Approximately 64.3m (3.5%) of global population of 40-80yrs
3. -Estimated to increase to 76m in 2020 and 111.8m in 2040
4. • More prevalent in an aging population and urban areas
5. • Asymptomatic until a relatively late stage, delay in diagnosis

6.– Estimated that 10-50% of people know they have the disease

7. • Mostly a primary disease but also a secondary disease
8. – Trauma, inflammation, tumour. etc

Question 9

Overview PROCESS OF GLAUCOMA = 4

2 TYPES?

Answer 9

1. • Loss in RGCs generally linked with increase in INTRAOCULAR PRESSURE
2. • Primary open-angle glaucoma (POAC)
     – Eye and iris angle open
3. • Primary angle-closure glaucoma (PACG)
     – Eye and iris angle closed
4. • Generally characterised by degeneration of RGCs and CHANGES IN THE OPTIC NERVE HEAD
     – ‘Cupping’

Question 10

Healthy eye vs Glaucoma

Answer 10

Healthy: Flow of aqueous humour through the drainage canal

Glaucoma:
1. drainage canal blocked - build up of fluid

2. increased pressure damages blood vessels and optic nerve

Question 11

Mechanisims of GLAUCOMA =

Answer 11

1. AQUEOUS HUMOUR SECRETED by CILIARY BODY
2. DRAINAGE THROUGH ‘TRABECULAR’ network = ‘UVEOSCLERAL OUTFLOW PATHWAY’
3. IN OPEN-ANGLE GLAUCOMA
   = increased resistance through trabecular network and blockage of drainage outflow
4. Results in increased IOP and causes mechanical stress towards the posterior eye

Question 12

Mechanisms of Glaucoma = what does IOP CAUSE? = 3

Answer 12

1. IOP causes MECHANICAL STRESS AND STRAIN ON THE EYE, notably ‘LAMINA CRIBOSA’
2. Compression and remodelling of LAMINA CRIBOSA resulting in ‘CUPPING’
3. DAMAGES AXONS and INTERRUPTS AXON TRANSPORT OF TROPHIC FACTORS

Question 13

DIAGNOSIS OF GLAUCOMA = 5

Answer 13

1. • Results in RGC DEATH and OPTIC NERVE FIBER LOSS
2. • Vision loss/blindness progresses over time
     – Usual ‘midperiphery to centriperipherydamage/blindness’
     – IRREVERSIBLE
3. • Early detection is identified with CHANGES IN APPEARANCE IN THE OPTIC NERVE AND RETINAL NERVE FIBRE LAYER’
4. • VISUAL FEILD DEFECTS CAN CONFIRM DIAGNOSIS
     – 30-50% of RGC loss before defects are DETECTABLE
     – DIFFICULT TO DIAGNOSE AS VARIABILITY WITH ‘ON’ HEAD

5 * IOP measured viaOCULAR TONOMETRY
– IOP VARIES DURING THE DAY
– Longitudinal testing

Question 14

Surgical interventions of glaucoma = 4

Answer 14

1. • Treatment focusing on SLOWING DISEASE PROGRESSION AND PRESERVING QUALITY OF LIFE
2. – Reducing IOP through pharmacological or surgical interventions
3. • Surgical techniques were described by von Graefe in the 19th century
4. IRIDECTOMY - CREATING A SMALL HOLE IN IRIS FOR AQUEOUS FLOW

Question 15

CURRENT SURGICAL INTERVENTIONS FOR GLAUCOMA = 4

Answer 15

1. TRABECULOPLASTY/ECTOMY - ‘DIRECT LASER’ or ‘REMOVE TRABECULAR MESHWORK’ to open blocked/clogged canals and allow fluid to flow through.
2. LASER PERIPHERAL IRIDOTOMY - used in ANGLE CLOSURE GLAUCOMA to CREATE A SMALL HOLE IN THE IRIS
3. CYCLOPHOTOCOAGLUATION - Laser directed to the CILIARY BODY to STOP PRODUCTION OF AQUEOUS FLUID
4. INSTALLATION OF STUNT TO ENHANCE AQUEOUS FLOW

Question 16

Pharmacological interventions OF GLAUCOMA = 8

Answer 16

1. • REDUCING INTAOCULAR PRESSURE pressure only known way to reduce progression
2. – Aim for a 20-50% reduction in IOP but needs to be CONSTANTLY REASSESSED
3. • DECREASE PRODUCTION OF FLUID or INCREASE DRAINAGE WITH ‘ BETA BLOCKERS, APLHA AGONISTS, CARBONIC ACID INHIBITORS’
     - 4. – Most effective pharmacological treatments have been developed in the past 30-40 years. Mischaracterisation
4. • ‘Calabar bean’
     – First IOP lowering medication introduced by
     Sir Thomas Fraser in mid 1800’s
5. – ‘PHYSOSTIGMINE - ACETYLCHOLINESTERASE INHIBITOR’
   – Decreases pupil size (miosis)
   – Reduces IOP

Question 17

CHOLINERGIC AGENTS:

Answer 17

1. NEUROTRANSMITTER-NEUROMUSCULAR JUNCTION
   - 2. PARASYMPATHETIC NERVOUS SYSTEM
   - 3. CNS
2. NICOTINCI RECEPTORS
3. MUSCARINIC RECEPTORS
4. PHYSOSTIGMINE

Question 18

Cholinergic agents - Nicotinic receptors = 3

Answer 18

1. • Ionotropic ligand gated receptor
2. – N1 receptors- Neuromuscular junction
3. – N2 receptors- CNS and PNS

Question 19

CHOLINERGIC AGENTS - MUSCARINIC RECEPTORS…= 3

Answer 19

1. • Muscarinic receptors- Metabotropic
2. – M1, M2, M3, M4, M5
3. – CNS, PNS, organ innervation

Question 20

Cholinergic agents = PHYSOTIGMINE

Answer 20

Physostigmine- acetylcholinesterase
inhibitor

Question 21

UNDERSTANDING CHOLINERGIC AGENTS … PILOCARPINE WHAT IS IT? = 3

Answer 21

1. • Pilocarpine- muscarinic acetylcholine agonist
2. – M3 receptor
3. – Receptor expressed in ciliary bodies (lens shape) and pupillary sphincter muscles (miosis)

Question 22

UNDERSTANDING CHOLINERGIC AGENTS …WHAT DOES IT DO? = 3

Answer 22

1. • Increases IOP outflow and production
2. -Constriction of iris and ciliary bodies relaxes zonular fibres and opens trabecular meshwork
3. -Lens becomes more spherical

Question 23

When is PILOCARPINE ADMINISTERED AND …..

WHAT CAN OVER-TREATMENT OF SUCH CHOLINERGIC DO? = 4

Answer 23

1. PILOCARPINE typically administered as EYE DROPS

2.Over treatment can result in a CHOLINERGIC CRISIS

3.– Overaccumulation of ‘ACh at synapses’ and
neuromuscular junction

4. Symptoms of NICOTINIC AND MUSCARINIC TOXICITY

Question 24

Prostaglandin analogs - WHAT IS PROSTAGLANDIN F2a receptor agonist? = 2

Answer 24

1. – Receptors expressed in CILIARY MUSCLE and TRABECULAR MESHWORK CELLS

2 – GPCR mediated effect

Question 25

• ‘PGF2α receptor ligand expression in a 72 year old
  donor eye’

EXPLAIN AUTORADIOGRAPHY AND PSEUDO COLOURING = 5

Answer 25

1. – Eyes mounted on slides and treated with [3H]PGF2α
2. – Slides loaded onto tritium sensitive film cassettes and phosphor screens
3. – Tritium emits low energy beta radiation which is
   captured by cassettes
4. • Can take days
5. • High receptor expression in longitudinal ciliary muscle (LCM) and iris sphincter muscle (ICM)

Question 26

Prostaglandin analogs…

WHICH RECEPTOR?

TYPES AND WHAT DO THEY DO?

WHEN USED?

INCREASES?

Answer 26

1. • Prostaglandin F2α receptor agonist
     – Receptors expressed in ciliary muscle and trabecular meshwork cells
     – GPCR mediated effect
2. • Latanoprost, Tarvoprost, etc
     – INCREASES OUTFLOW IN THE UVEOSCLERAL PATHWAY
3. • Used once daily, low dose
     – Approximately 22-39% reduction in IOP
     – Increased compliance
     – Minimal side effects

4 * INCREASES MELANIN PRODUCTION
– HYPERPIGMENTATION OF EYE LASHES, IRIS AND PERIOCULAR AREA

Question 27

WHAT IS BDNF?
WHAT IS ITS RECEPTOR? WHAT DOES IT DO? = 5

Answer 27

1. • Brain derived neurotrophic factor (BDNF)
2. its receptor tropomyosin
   receptor kinase B (TrkB)
3. are implicated in a variety of brain processes
   
   4. -Development, plasticity, cell survival, etc
   5. -Neuroprotective

Question 28

Target derived BDNF vs local BDNF = 3

Answer 28

1. PARACRINE - surrounding cells produce and release BDNF
2. AUTOCRINE -RGCs produce and realse BDNF
3. TARGET - NEURONS: neurons in the taregt (e.g superoir colliculus or LGN) produce and release BDNF

Question 29

BDNF …DBA/2J MOUSE

WHAT DOES TOPICA; BDNF DO? = 5

Answer 29

1. DBA/2J mouse- Develops chronic intraocular pressure elevation that mimics glaucoma
2. -Experience a loss in RGCs

3.Topical BDNF increased RGC survival

4. ## 1 eye drop every 48hr for 2 weeks
5. Increased retinal BDNF

Question 29

WHAT DOES STEM CELL THERAPY DO?

Answer 29

1. • Stem cells are able to differentiate into other cell and neuron types
2. – Lack cellular identity
3. • High levels of stem cells during development that give rise to the brain and
     other organs.
4. After development, the production of stem cells decreases
5. Once a stem cell has differentiated into a cell/neuron, it is tied to that fate

Question 30

TYPES OF Stem cell therapy = 2

Answer 30

-Embryonic stem cells

-Reprogramming adult cells into neurons

Question 31

EMBRYONIC STEM CELL ADVANTAGES AND DISADVANTAGES …

Answer 31

+Potential to differentiate into any cell type

-Ethical concerns

Question 32

ADVANTAGES AND DISADVANTAGES … OF Reprogramming adult cells into neurons

Answer 32

+ No ethical concerns

+Less chance of rejection after transplantation

Question 33

STEM CELL THERAPY AND GLAUCOMA EXAMPLE

Answer 33

TRANSPLANTATION OF REPROGRAMMED PERIPHERAL BLOOD CELLS DIFFERENTIATES INTO RETINAL GAANGLION CELLS IN THE MOUSE EYE WITH NMDA-INDUCED INJURY

Question 34

STEM CELL THERAPY PROCESS OF

…INDUCTION OF PLURIPOTENT STEM CELLS FROM MOUSE EMBRYONIC AND ADULT FIBROBLAST CULTURES BY DEFINED FACTORS = 6

Answer 34

1. T-cell –> TiPSC –> RPC —> RGC
2. • Extract T-cells from venous blood and plate in culture
3. • Infect T-cells with a ‘Sendai virus’ driving the expression of ‘Yamanaka
     factors’
4. – Sendai virus is a single strand RNA and does not disrupt DNA in anyway
   (cytosol)
5. – Yamanaka factors- Oct3/4, Sox2, c-Myc, Kfl4

6.Nobel prize in 2012

Question 35

Stem cell therapy

• Author’s injected iPSCs into the eye in a mouse model of glaucoma = 4

Answer 35

1. – NDMA excitotoxicity model. High concentration of NMDA damages RGCs
2. – Progressive loss of RGCs over time. Noticeable at 2w post injection
3. – Injected 0.5ul of cell suspension at a density of 50,000 cells/ul
4. NMDA treatment reduced the number of RGCs
   (confirmation of glaucoma model)

Question 36

Stem cell therapy = ANALYSIS OF GLAUCOMA STEM CELL THERAPY = 3

Answer 36

1. • -Analysed wholemounts of NMDA injected mice 2w after transplantation of
     TiPSC
2. • -Immunostained with DAPI and TUJ1 to confirm migration and survival of
     RGCs
3. • -TiPSC-EBs were able to migrate to the RGC layer and differentiate into RGCs without any additional factors, and in an injury model

Question 37

Stem cell therapy - VEPS

= 5

Answer 37

1. • Obtained ‘visual evoked potentials’ (VEPs) to assess if these cells were functional.
2. Measure the evoked response of neurons caused by a visual stimulus.
3. – Stimulated retinal cells with light and record activity in the visual cortex with
   electrode.

4.Is this the most relevant test for this model at this
timepoint?

5. Increasing the number of neurons does not necessarily mean improved function

Question 38

IMPORTANT KEY POINTS = 5

Answer 38

1. • The eye is important in transducing light into electrical signals and
     projecting these signals to the brain
2. • Glaucoma is characterised by an increase in IOP and mechanical damage to RGC axons at the optic disc
3. • Glaucoma treatment focuses on reducing IOP to preserve RGC health and
     function
4. • There are different pharmacological and surgical treatments depending on
     treatment requirements
5. • Lifelong management and treatment