The cornea

• What are the learning goals mentioned in the study material?

  Gross anatomy, microstructure, innervation, regulation
• What is the significance of the cornea in the eye?

  It is the most important optical element of the eye
• What percentage of ocular dioptric power does the cornea account for?

  75%
• What is the cornea's role as a barrier?

  It prevents foreign substances from entering the eye
• What is the diameter of the cornea horizontally (HVID)?

  11.7 mm
• How does the corneal diameter differ between genders?

  Women have smaller diameters by about 0.1 mm
• At what age does the corneal diameter not significantly alter?

  From the age of 2 years
• What is the corneal diameter at birth?

  9.5 mm
• What defines microcornea and macrocornea based on HVID?

  HVID < 10 mm = Microcornea; HVID > 13 mm = Macrocornea
• What is the anterior radius of the cornea?

  Approximately -7.8 mm
• What is the posterior radius of the cornea?

  Approximately -6.5 mm
• How does the radius of curvature affect dioptric power?

  A smaller radius means more dioptric power
• What is the central corneal thickness (CCT) range?

  490 to 560 µm

  
• What does a CCT > 700 µm indicate?

  Endothelial decompensation
• What does a CCT < 400 µm indicate?

  Keratoconus
• What is the normal range for corneal thickness at the limbus?

  700 to 900 µm

  
• What factors affect corneal thickness?

  Age, gender, ethnicity, refractive error

  
• How does age affect corneal thickness?

  CT decreases with age

  
• How does gender affect corneal thickness?

  Women have slightly thinner corneas than men

  
• What is the effect of high myopia on corneal thickness?

  High myopias have decreased CT

  
• How does circadian rhythm affect corneal thickness?

  CT increases during the night by about 5.5%
• What ocular pathologies affect corneal thickness?

  Fuch’s dystrophy, keratoconus, glaucoma
• What is the correlation between IOP and CT?

  Positive correlation between IOP and CT
• What happens to IOP after LASIK surgery?

  Average decrease of 2.5 mmHg
• What is the refractive index of the tear film and aqueous humour?

  1.3375
• What is the refractive index of the cornea?

  1.376
• What are the optical functions of the cornea?

  Refraction and transmission of light
• What maintains corneal transparency?

  Minimal scattering and smooth optical surface
• What is the composition of the cornea?

  78% H2O, 15% collagen, 5% other components
• What is the thickness of the epithelium?

  50 µm thick
• How many layers does the corneal epithelium consist of?

  5–7 cell layers
• What are the three layers of the corneal epithelium?

  Apical, wing, basal columnar cells

  
• What is the function of tight junctions in the epithelium?

  Maintains corneal homeostasis and transparency
• What is Bowman’s membrane?

  Modified region of the anterior stroma
• What is the thickness of Bowman’s membrane?

  8-14 µm thick
• What is the primary composition of the stroma?

  Rich in collagen, predominantly type I
• What is the thickness of the stroma?

  About 450-500 µm thick
• What are the main components of the cornea's microstructure?

  • Epithelium
  • Bowman's membrane
  • Stroma
  • Descemet's membrane
  • Endothelium

  
• What are the clinical parameters related to corneal health?

  • Corneal thickness (CT)
  • Corneal transparency
  • Ocular pathologies
  • Intraocular pressure (IOP)
  • Contact lens fitting

  
• What are the optical characteristics of the cornea?

  • Refractive index: 1.376
  • Optical functions: refraction and transmission
  • Maintains transparency through minimal scattering