Week 26

• What is the retina?

  The retina is a sensory membrane lining the inner back surface of the eye, converting light into nerve impulses that the brain can interpret.
• What are the key regions of the retina


  • Macula: Enables central vision and fine detail.
  • Fovea: Provides the sharpest vision, avascular to reduce light scattering.
  • Optic Nerve: Transmits visual information to the brain, creating a blind spot.
• Where is the retina thickest and thinnest?

  Thickest at the optic nerve head and thinnest in the periphery.
• What is phototransduction?


  It is the process by which the retina converts light into signals for the brain to interpret.
• What does the red reflex indicate?

  It results from light reflecting off choroidal blood vessels; absence may suggest opacity or retinal detachment.
• What is the ora serrata?

  The outer boundary of the retina, firmly attached to the ciliary body, non-light sensing, and difficult to visualize.
• What is the function of the Retinal Pigment Epithelium (RPE)?

  • Adhesion and nutrient transfer.
  • Waste removal and support for photoreceptors.
  • Forms the blood-retina barrier.

  Absorbs stray light and produces visual pigments
• What are the main types of photoreceptors in the retina?

  • Rods: Function in low light (scotopic vision), monochromatic.
  • Cones: Function in bright light (photopic vision), colour vision and fine detail.
• What is the ratio of bipolar cells to photoreceptors in the retina?

  • Fovea: 1:1:1 for fine detail.
  • Periphery: 50-100:1 for sensitivity.
• What is the role of ganglion cells?

  They collect and transmit visual information via the optic nerve.
• Name the supporting cells in the retina and their functions.

  • Horizontal Cells: Pool color information.
  • Amacrine Cells: Modulate signals.
  • Microglia: Retinal defense.
  • Astrocytes: Isolate signals.
  • Müller Cells: Structural support and nourishment.
• How do receptive fields enhance edge detection?

  By responding to contrast changes and organizing into overlapping on-center/off-center fields.
• What is the role of the optic nerve head (ONH)?

  It is where retinal nerve fibers converge, crucial for detecting visual field defects such as glaucoma.
• How is the retina supplied with blood?

  • Inner 2/3: Central retinal artery.

  Outer 1/3: Choroid.
• What are the types of retinal hemorrhages and their sources?

  • Flame hemorrhages: Inner plexus (ganglion/NFL).

  Dot/blot hemorrhages: Outer plexus (bipolar layer).
• What is the importance of the fovea?

  It is the central fixation point, covers 1% of the retina but accounts for 50% of the visual cortex.
• Why is the fovea avascular?

  To reduce light scattering and maximize optical quality.
• What are the characteristics of peripheral retina?

  Larger in myopic eyes, increasing the risk of retinal tears and detachment.
• How does colour vision work?

  Three cone types (red, green, blue) detect different wavelengths and enable trichromatic vision.
• What are the spectral sensitivity peaks of vision?

  • Photopic (daylight): 555nm (green-yellow).
  • Scotopic (night): 500nm (blue-green).
• What are the methods used to examine the retina?

  • Direct ophthalmoscope: 8° field of view.
  • Slit lamp with 90D lens: 74-89° field.
  • Fundus camera/OCT: 45° field.
  • Ultra-widefield imaging (Optos): 200° field.
• Why don't we see our retinal blood vessels constantly?

  Due to the Purkinje retinal vessel tree effect, where the brain filters them out.
• What is the function of the cilioretinal artery?

  Provides extra blood supply and can preserve vision in central retinal artery occlusion.
• Why does the fovea have high visual acuity?

  It contains only cones with no overlying cells, allowing maximum light transmission.
• What is the importance of understanding retinal anatomy?

  To diagnose and manage pathologies such as retinal detachment, glaucoma, and vascular occlusions.