2yr OCAP — Transparent Media

Aqueous Humor is? and its concentration are?

Similar to Plasma but has:

— High concentration of ascorbate, pyruvate, lactate.

— Lower concentration of protein, urea, and glucose

Volume of Aqueous Humor in Ant. Chamber & Post. Chamber? And their RI?

AC — 0.25ml

PC — 0.06ml

RI — 1.33

Functions of the Aqueous Humor?

1. Maintains IOP

2. Provides nutrition to avascular lens & cornea

3. Optical Transparency

4. Place of space that is absent in eyeball

Aqueous Drainage is divided into how many systems?

Three Systems

1. Trabecular - Conventional/pressure dependent 90%

2. Uveoscleral - Unconventional/Extracanalicular/pressure dependent 10%

3. Iris Outflow <1%

Full Aqueous Flow?

Ciliary Body → Posterior Chamber → Pupil → Anterior Chamber → Trabecular Meshwork → Schlemm’s Canal → Aqueous Vein → Episcleral Vein → Vortex Vein

Crystalline Lens Structure

1. Transparent, avascular, biconvex structure

2. Deprived of Nerves

3. Found in the anterior cavity of the eye

4. Connected to the ciliary body via suspensory ligament

Crystalline Lens Function and RI

1. Contributes to the refractive power of the eye

2. RI — 1.38-1.42

Crystalline Lens Index of Refraction

Centrally: 1.4

Peripherally: 1.36

Dioptric Power: 15-20D

Lens Measurement at BIRTH

Equatorial - 6.4mm

Anteroposterior - 3.5mm

Weight - 90mg (miligram)

Lens Measurement during ADULTHOOD

Equatorial - 9mm

Anteroposterior - 5mm

Weight - 255mg (miligram)

Functions of the lens

1. Maintains its own clarity

2. Refracts light

3. Provides accommodation

During Accommodation

1. Ciliary Muscle relax

2. Zonules taut (constricts)

3. Lens flattened for focusing on distant objects

During Unaccommodation

1. Ciliary Muscle contract

2. Zonules relax

3. Lens rounded to focus on close objects

Parts of Crystalline Lens

1. Lens Capsule —

• Collagen type IV, and glycosaminoglycan

• Moulds the lens during accommodation

2. Lens Epithelium —

• Simple cuboidal epithelium

• Found only in anterior pole between lens capsule and lens fibers

• Epithelial cells regulate the homeostatic functions of the lens, transporting FLUID and IONS from the aqueous humor

• Progenitor for lens fibers

Composition of Vitreous Humor; Water, Cellular Components, Collagen, Proteins, Presence of, Acids?

Water: 98%-99%

Cellular Components: Phagocytes & Hyalocytes

Collagen: Collagen type II and Vitrocin

Proteins: Small amount

Presence of: Salt & Sugar

Acids: Glycosaminoglycan and hyaluronic acid

Functions of the Vitreous Humor

1. Inflates the eyeball

2. Keeps the retina in place pushing it to the choroid

3. Contributes to Refractive Power with RI of 1.34

Intraocular Pressure (IOP): Function and Value?

Pressure exerted by intraocular fluids on the coats of the eyeball.

Value: Normal 10-21mmHg (milimeter of mercury)

Long Term — Influencing factors of the IOP

Heredity, Age, Sex, Race, Refractive Error

Short Term — Influencing factors of the IOP

Posture: Increased in supine position, highly increased in head down position

Excercise: Decreased in aerobic excercise, increased in isometric excercise

Systemic — Influencing factors of the IOP

Food/Drugs:

1. Alcohol, fatfree diet, vasodilators, heroin, mints — Lowers IOP

2. Water, caffein, steroids, and mydriatics — Increases IOP

3. General Anesthesia: Lowers IOP except KETAMINE