glaucoma - pharmacology of eye disease

• outline the basic anatomy of the eye (esp for a glaucoma):

  
• what is a glaucoma?

  •Visual impairment - Progressive optic neuropathy, optic nerve cupping

  •Intra-ocular pressure (IOP) raised – a significant risk factor

  •IOP regulated by production and drainage of aqueous humour, 2 causes:

  1. Impaired drainage (↓outflow) is a common cause of raised IOP

  2. Increased production (↑inflow) is a rare cause of raised IOP
• how are glaucomas classified?

  •Primary vs secondaryvs chronic
• how are glaucomas classified?

  • Primary vs secondary
  • Acute vs chronic
  • Open angled vs close angled
  • Primary open-angle glaucoma (POAG) is most common (and chronic)
• ciliary body - an extension of the eye that produces humour
• production of aqueous humor

  ciliary bodies synthesise aqueous humour -> posterior chamber -> pupil -> anterior cavity -> anterior chamber -> chamber angle -> outflow mechanism
• under which conditions is aqueous humour produced?

  Aqueous production via three processes

  •Passive diffusion of solutes down concentration gradients

  •Filtration of fluid from fenestrated capillaries into interstitium of ciliary stroma (passive)

  •Active secretion of solutes against gradients (80-90% production)

  
  

  which 2 biochemical mechanisms are ESSENTIAL for the production of humour

  •Sodium pump: Na⁺/K⁺-ATPase

  •Carbonic anhydrase (CA)
• which three layers comprise the ciliary body?

  1. muscle (three types longitudinal, radial and circular)
  2. epithelia (double layered - inner and outer/ pigmented and non pigmented)
  3. stoma (mesenchyme and connective tissue)
  4. vessels
  5. nerves

  
• what are the functions of the three layers of ciliary muscles:

  1.Longitudinal (LCM): most external, connects scleral spur and trabecular network anteriorly to choroid sclera posteriorly.

  Contraction opens trabecular network and Schlemm’s canal.

  2.Circular (CCM): anterior, inner muscles.

  Contraction → accommodation

  3.Radial (RCM): intermediate, connects LCM and CCM.
• what are they two layers of epithelia in the ciliary body?

  1.Inner layer: non-pigmented adjacent to aqueous humour in posterior chamber

  2.Outer layer: pigmented adjacent to stroma/vessels
• how does the double layered epithelia aid in producing aqueous humour:

  the functional syncytium is made of the non and pigmented layers of epithelia -> overall Na+ is transported across by many transport proteins across both layers of epithelia and their respective basement membranes -> gap junctions between the epithelia allow for the diffusion of molecules across -> Na+/K+ ATPases pump Na+ out into the aqueous humour (then follows water, humour production by pumping out solutes)

  CA allows for the regulation of pH

  
• what are the two outflows for aqueous humour in glaucomas?

  • ~90%: trabecular meshwork -> Schlemm’s canal -> scleral and episcleral veins (pressure SENSITIVE)

  • ~10%: uveoscleral route (pressure INSENSITIVE)