Ophthalmology introduction Flashcards
What is the average axial length
23mm
Differentiate myopia and hypermetropia
myopia ‘short sight’
long eyeball
image focuses in front of retina
hypermetropia ‘long sight’
short eyeball
image focuses behind retina
What happens if there is misalignment of the visual axes
misalignment of the visual axes will lead to double vision or suppression of the 2nd image
What is proptosis?
Inflammation (Graves ) in a bony box
,…
….
What occurs to the eye in orbital fracture
Orbital fracture= Box broken = enophthalmos & eye movement restriction (trapped inferior rectus)
Outline the facial development
Branchial arches form in the 4th week
1st arch - forms the face
2nd- muscles of facial expression
Outline the embryological development of the eye
- The eye begins to develop as a pair of optic vesicles on each side of the forebrain at the end of the 4th week of pregnancy.
- Optic vesicles are outgrowings of the brain which make contact with the surface ectoderm and this contact induces changes necessary for further development of the eye.
- Through a groove at the bottom of the optic vesicle known as choroid fissure the blood vessels enter the eye.
- Several layers such as the neural tube, neural crest, surface ectoderm, and mesoderm contribute to the development of the eye
What is failure of fusion of the iris called
Iris coloboma, can also happen with retina (retinal coloboma)
Visual milestones at birth, and 3 months
do not focus on targets further than 20-30 cm away
only see high contrast eg chequerboard not colours
cannot move their eyes between the two images
at 3 months should be able to
fix & follow
Visual milestones at 5-8 months
good colour vision by five months of age
8 months old start crawling
reaches for objects
Visual milestones at 9months-1year
visually spot a small (2-3 mm) object nearby
watches faces and tries to imitate expressions
searches for hidden objects after observing the “hiding”;
By 2 years
By 2 years complete myelinization of the optic nerve is completed; acuity is normal
By 2-5 yeats
2-5 years brain functions nearly adult basic sensory processing abilities. Analyzing complex visual scenes, specific objects and faces will occur later.
By 3 years?
By 3 years: Retinal tissue is mature the child can complete a simple form board correctly (based on visual memory), do simple puzzles, draw a crude circle and put 2.5 cm pegs into holes.
By 5-7 years
By 5-7 years: the functional development of brain substrates for perception of complex visual scenes takes still longer.
Definition of blindness
Blindness is legally defined as ‘so blind that they cannot do any work for which eyesight is essential’.
Most common cause of blindness globally
Cataract
What is most common cause of irreversible blindness in working aged people
Diabetic retinopathy
Outline the disease process in trachoma
There is infection with chlamydia trachomatis
This causes trachomatous inflammation and then scarring
There is then trachomatous trichiasis which causes the eyelashes to be pulled in
The lashes can scratch the corneal surface, leading directly or indirectly (from secondary infections) to corneal opacity
What are the interventions for trachoma
Environmental improvements
Face washing
Abx treatment
Surgery for trichiasis
(at each stage, have a look)
or
SAFE:
Surgery, antibiotics, face washing and education & environmental improvements
Abx treatment for trachoma
Tetracycline or azithromycin
