Intro to opthamology Flashcards
Formation of a focused image on the retina is dependent on…
1) Ocular shape
2) Transparency of the ocular media
3) Ability of the transparent structures to refract light
Functions of the sclera…
1) Maintains eye shape
2) Maintains intraocular pressure
3) Barrier to infection and trauma
Functions of the cornea…
over the iris and lens
1) Transparency
2) Refraction –> Major refractive component of the eye
3) Barrier to infection and trauma
Aqueous humour is formed by…
Active secretion from the ciliary body epithelium.
The two drainage routes out of the eye for aqueous humour are…
1) Conventional Route –> 85% drains via the trabecular meshwork into the canal of Schlemn.
2) Uveoscleral Route –> 15% drains through the ciliary body and into the ciliary circulation.
What is normal Intra-Ocular Pressure (IOP)?
10-21 mmHG
IOP normally changes throughout the day.
Functions of the crystalline lens…
1) Transparent –> Absence of blood vessels
2) Fine focusing –> Age-related, metabolic, or congenital changes in the lens fibres lead to structural irregularity with resultant opacification (i.e. cataract formation)
Functions of the vitreous humour…
1) Transparent –> collage type 2
2) Protects the ocular structures –> firm gel that is 80% of the globe volume
3) Passive “transport and removal” of metabolites
What are hyalocytes?
Also known as vitreous cells.
Located in the peripheral part of the vitreous body.
Produce hyaluronic acid, collagen,and hyaluronan, glycosaminoglycan.
Function of the retina…
1) Transparent
2) Converts light energy into nervous impulses (via photo-receptors)
What is the macula?
Central vision area of the retina….
1) Lies lateral to optic disc.
2) Slightly darker than rest of retina due to yellow luteal pigment.
3) Has higher visual acuity than rest of retina.
What is the fovea?
The centre of the macula that is rod free and has the highest visual acuity.
“The red eye” (pain, redness, photophobia, discharge) indicates problem with…
Front of the eye.
Painless loss of vision indicates problem with…
Back of the eye.
Distortion of vision/central scotoma indicates problem with…
Macula.
Flashes and floaters indicates a problem with…
Vitreous or retina.
What is emmetropia?
There is no refractive error and light rays from infinity are brought to focus on the retina.
What is myopia?
A term for short-sighted vision where light rays from infinity are brought to focus just in front of the retina.
1) Eye is too long.
2) Or converging power of lens is too strong.
What is hypermetropia?
A term for long-sighted vision where light rays from infinity are brought to focus just behind the retina.
1) Eye is too small.
2) Or converging power of the lens is too weak.
What is astigmatism?
The cornea is NOT spherical.
What is the accommodation-convergence reflex?
A physiological mechanism that allows close objects to be focused on the retina.
Non-accommodating state –> ciliary muscle is relaxed, lens suspensory ligament remain taunt.
Accommodating state –> contraction of ciliary muscle, lens suspensory ligament becomes lax, causing naturally elastic lens to assume more globular (convex) shape.
What is presbyopia?
Long-sightedness caused by loss of lens elasticity (i.e. poor accommodation response). Typically occurs over age of 45 and can be corrected by a weak converging (convex) lens.
