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Y3 > Intro to ophthalmology > Flashcards

Intro to ophthalmology Flashcards

1
Q

What is the most common cause for being registered partially sighted or blind under the age of 65

A

Diabetes mellitus

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2
Q

What do eyes do?

A

Formation of a focussed image on the retina

Transduction of the image into an electrical signal

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3
Q

What is the formation of an image in the eye dependent on

A

Ocular shape - astigmatism
Transparency of the ocular media - cataract
Ability of the transparent structures to refract light

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4
Q

Basic eye anatomy

A 
Cornea
Iris 
Pupil 
Lens 
Vitreous Humour 
Retina 
Macula 
Fovea 
Optic disc
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5
Q

Function of the cornea

A

Maintain transparency
Refraction
Barrier to infection and trauma

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6
Q

How is transparency maintained in the cornea

A

Stroma is maintained relatively dehydrated by the impermeable epithelial barrier and active pumping mechanisms of the corneal endothelium
The regular spacing of individual collagen fibrils
Stasis of the fibres and regular spacing of fibres maintain transparency

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7
Q

What is the refractive role of the cornea

A

The cornea is the major refractive component of the eye - 48/58 dioptres

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8
Q

What is the sclera and what does it do

A

Outer coat of the eye
- opaque, mechanically tough
- forms the posterior 5/6 of the outer coat of the eye
- consists of irregularly arranged collagen fibres
Maintains the eye shape
Maintains the intraocular pressure
Barrier to infection and trauma

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9
Q

What is the aqueous humour

A

It is formed by the active secretion by the epithelium of the ciliary body
Drainage out of eye
- conventional - 85% drains through the trabecular mesh work into the canal of schlemm in the anterior chamber angle
- uveoscleral route - 15% drains through ciliary body into the and into ciliary circulation

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10
Q

What is normal intraocular pressure ?

A

Maintained at 10-21mm Hg

There is a dynamic balance between secretion and drainage of aqueous humour

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11
Q

What is high IOP

A

Glaucoma

Which leads to loss of visual fields and eventual blindness

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12
Q

Features of the crystalline lens

A

Transparent - orderly arrangement of the lens fibres, small difference in refractive index between the various components, absence of blood vessels
Fine focusing - age related , metabolic e.g. Diabetic, or congenital changes in lens fibres lead to structural irregularity with resistant opacification i.e. Cataract formation

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13
Q

Features of the vitreous humour

A

Transparent - collagen type II, arranged into fibrils, few cells ( hyalocytes) - secreting glycoaminoglycans
Protects the ocular structures - firm gel, 80% of the globe volume
Passive transport and removal of metabolites - nourish the retina and maintain shape and integrity of vitreous

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14
Q

Features of the retina

A

Transparent
Transducers light energy into nervous impulses
- at least 11 layers
- photoreceptors 120 million rods - monochromatic, 6 million cones colour vision

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15
Q

Features of the macula

A

Central vision of the retina
- lies lateral to the optic disc
- slightly darker that the rest if the retina due to yellow luteal pigment
Fovea is the centre of the macula and is rod free
Has higher visual acuity
Fovea has the most cones so has the highest visual acuity

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16
Q

Features of the optic nerve

A

Contains over 1 million fibres - non myelinated in eye myelinated as the leave the eye
Nasal fibres decussate at the optic chiasm
Optic disc - the entry of the optic nerve into the eye, corresponds to the blind spot of the visual field as does not contain any overlying photoreceptors

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17
Q

What is the visual pathway

A 
Optic nerves
Optic chiasm
Optic tracts
Lateral geniculate nucleus 
Optic radiations
Visual cortex
18
Q

How to take an ophthalmic history

A 
HPC 
- general symptoms 
-- unilateral or bilateral
-- onset and duration
-- any pain, photophobia, redness discharge 
Vista symptoms
Vision loss 
Sudden gradual distortion 
Field defect 
- unilateral bilateral, central peripheral
Flashes floaters
Diplopia 
Horizontal vertical, binocular, monocular 
Past ocular history 
Other disease 
Family history - glaucoma
PMH
Allergies
Drug history
General health 
Social history
If a child include - obstetric, pregnancy, birth neonatal problems 
Developmental problems and milestones, immunisation history
19
Q

Where is the problem is the eye is red

A

Front of the eye

20
Q

Where is the problem is there is painless loss of vision

A

Back of the eye

21
Q

Where is the problem if there is distortion of the vision/central scotoma

A

Macula

22
Q

Where is the problem if there are flashes or floaters

A

Vitreous or retina

23
Q

What are the types of refractive error

A 
Emmetropia
Ametropia
- myopia
- hypermetropia
- astigmatism
24
Q

What is emmetropia

A

There is no refractive error and light rays from infinity are brought into focus on the retina

25
Q

What is Myopia

A

Short sighted
Light rays from infinity are brought to focus in front of the retina
- the eye is too long - axial myopia
- the lens is too strong from nuclear sclerotic cataract - index myopia

26
Q

What is hypermetropia

A

Light rays from infinity are brought to a focus behind the retina - the eye is too short
Or
The converging power of the cornea or lens is too weak

27
Q

What is astigmatism

A

The cornea is not spherical - rugby ball shaped rather than football shaped

28
Q

What is Accommodation

A

Physiological mechanism that allows close objects to be focused on the retina
In the non accommodative state the circular ciliary muscle is relaxed - allowing the suspensory ligaments of the lens or remain taut
During accommodation the ciliary muscle contracts and the suspensory ligaments become lax causing the natural elastic lens to assume a more globular (convex) shape

29
Q

What happens to accommodation with age

A

Usually 45 years + the lens gradually hardens and is unable to accommodate - called presbyopia
This can be corrected by a weak converging lens (plus) convex lens

30
Q

What occurs in an ophthalmic examination

A

Vision: acuity
Pupils : reaction to light
Front of eye
Back if eye

31
Q

How is the front if the eye examined

A

Pen Torch
Ophthalmoscope
Slit lamp microscopic

32
Q

How is the back of the eye examined

A

Direct ophthalmoscope

Indirect ophthalmoscope

33
Q

What is an ophthalmoscope

A 
3 essential components 
Lenses 
Light
Diaphragm 
See the back of the eye 
Asses red reflex and look at the retina
34
Q

Features of an ophthalmoscope

A

Magnification approx x 15
Small field of view - 6.5-10 degrees
With an undilated pupil you will not see the macula
The disc will take up the whole field of view
Don’t ask the patient to look into your light as the Latimer will accommodate and together with the bright light it will make the pupils smaller

35
Q

How to know what lens to set the ophthalmoscope to

A

If you wear glasses keep them on
Does the patient wear glasses need to set the ophthalmoscope to the patents refractive error
If got contacts lenses set to zero

36
Q

How to do direct ophthalmoscopy

A

Remove patients glasses
Hold ophthalmoscope with your index finger on the lens dial, set ophthalmoscope to see the fundus
Angle of approach
- 15 degrees temporal to the patient
- Same height as the patient
- aim 15 degrees nasal and you’ll hit the optic disc - corresponds or their blind spot
Get close
Start with your dominant eye
Close non dominant eye
Use diaphragm dial to set the small white beam for an undilated pupil and observe the red reflex (yellow orange glow)
The greater the refractive difference between you and patient the more blurred the red reflex will be

37
Q

What to look at in direct ophthalmoscopy

A

Optic disc - colour, cup: disc ratio and contour
New vessels if diabetic

Retinal blood vessels
Arterioles and veins
Claire
New vessels, collateral vessels

38
Q

What is background retinopathy

A 
Least problematic 
Scattered haemorrhages and hard exudates
Not affecting the macula
Non sight threatening 
Used as a marker of disease control
39
Q

What is diabetic maculopathy

A

Haemorrhages and hard exudates in the macula
Leakage if fluid from the vasculature and macular oedema
Treated with a focal laser - fluid can be lipid and interfere with vision
Sight threatening
Needs treating

40
Q

What is the pre proliferative retinopathy

A

It is the next stage from background
More than five cotton wool spots
Venous drainage - thickening tortuousity or beading
Indicated retinal ischaemia
Sight threatening
Can’t treat eye need to aggressively treat diabetes

41
Q

What is proliferative retinopathy

A 
New vessels 
NVD - Disc 
NVE - elsewhere 
New vessels bleed causing vitreous haemorrhage 
Requires extensive laser treatment 
Panretinal photo coagulation 
Where they grow threatens sight
Intravitral injection to try to regress blood vessels

Y3 (22 decks)

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