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CP1 mid sessionals term 1 > Important content to remember > Flashcards

Important content to remember Flashcards

1
Q

describe the optic disc, cup and macula and fovea.

describe arteries vs veins
and isnt rule

A

optic disc is nasal and the macula is temporal.
optic disc is the blind sppot. no photoreceptors.
pinky orange colour but not good if white.

arteries are thinner and lighter and veins are thicker and redder.

I>S>N>T follows isnt and if isnt then isnt glaucoma.
neuroretinal rim is the broadest in inferior and thinnest in temporal.

cup size= 0.3-0.4mm. can be different. normal in some people or indicator of damage.

macula= posterior retina that contains pigments and photoreceptors cells. responsible for colour and central vision. fovea is the depression of central inner macula=clearest vision.

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2
Q

when examining the eye what do you look for (10)

A

overall view of the eye
assess quality of fundus
assess disc appearence
colour (pink)
clarity disc margin (sharp edges)
cup to disc ratio
neuroretinal rim isnt rule
assess arteries and veins

repeat for each 4 quadrants
assess macula and fovea

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3
Q

high blood pressure vs high intraocular pressure

A

high blood pressure= can see it in the back of the eye.=hypertension screening.

high intraocular pressure= due to poor drainage of aqueous humour.

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4
Q

monocular

describe and
mag and fov numbers

A

using one eye to assess
views real and erect images
condensing lens required
greater fov and wd
lower mag
no stereopsis (3d)

mon indirect- 5 times mag
15 degrees fov
independent of patients Rx
no stereoscopic view

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5
Q

binocular

A

using both eyes to assess
stereoscopic, aerial
condensing lens
real inverted laterally reversed
greater fov than direct

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6
Q

direct vs indirect

A

direct- small fov, high mag, close wd, dim image, monocular, easy to use, mag image, erect image

indirect- high fov, low mag, far wd, need to dilate pupil, stereoscopic, inverted imag.

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7
Q

keeler wide angle vs Pan optic

A

monocular
10 times larger fov than direct

Pam optic- 5 times larger than direct

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8
Q

binocular

A

using both eyes to assess
stereoscopic, aerial
condensing lens
real inverted laterally reversed
greater fov than direct

higher power condensing lens= decreases mag= increases fov

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9
Q

indirect biomicroscopy( slit lamp) and compare to head mounted bio
and when to use

A

fov depends on lens power and diameter of lens
90 and 78D bi convex
60D and superfield unidirectional

less mag w stronger lenses.

lens used with slit lamp
short wd
gerater mag than head mounted bio
smaller fov than head mounted bio

when to use-
poor direct view
stereoscopic view
wider fov than direct

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10
Q

binocular indirect
head mounted bio

prinicples
properties
procedure
and when to use

A

principles-

stereoscopic view
hand held condensing lens
image inverted and laterally reversed
real image

condensing lens most common is +20
flatter side towards patients
lower powers have higher mag, smaller field of view, greater wd.

properties-
2.5 times mag
30 degrees fov
must dilate

procedure-
set up headbang
eye piece rx and pupil size
hold condensing lens in front of eye
pull lens back until fundus image fills lens
8 positions
remember inversions

when to use- poor direct view
stereoscopiv view
to see whole fundus
to assess for diabetes, rd symptoms or young children

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11
Q

digital fundus camera

A

large stand instruments
2 light sources- 1 to take flash photo and 1 to view fundus

optical design based on indirect opth
specialised low power microscope w an attached camera

immediate viewing
archive and monitor
images can be shown to patients

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12
Q

oct

A

most common used for routine imaging of retina and optic nerve in high resolution

non invasive cross sectional imaging of retina by measuring the backscatter and delay as it journeys through the ocular tissue comparign it to a known reference path

provides thickness data of retinal layers
used in med retina care, glaucoma care, primary health care and screening

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13
Q

equation for direct opthalmoscopy

A

M= Fe/4 times 1/1-wK

Fe= power of eye +60
w= working distance (negative and m)
k=ocular refraction

mag= Fe/4 therefore emmetropes its always times 15, if myope then power is higher than 60 then it will be more than 15
for hyperopes power is less so it will be less than 15

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14
Q

higher refraction of the patients eye is it easier or difficult to assess back of eye and why

A

more difficult it is to assess the back of the eye

as increased refraction= increased mag= decreases fov

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15
Q

if light doesnt focus on the retina but behind it

A

blur circle is formed on the retina
we can work out the size of this= field of view

j(m)=g(k-w)/Fe

j= blur circle of fov
g= pupil size (m)
k= ocular refraction
w= reciprocal of wd (m and negative)
Fe= dioptric power= 60D

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16
Q

factors affecting fov and mag

A

pupil size increases increases fov
sighthole size
wd closer increases fov
subjects ametropia. increasing decreases fov

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17
Q

good ophthalmoscope

A

clear uniform light patch
fov coincident w light patch
minimise corneal reflections
abscence of sighthole flare
range of target apertures
extra targets

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18
Q

for j= k-w equation

A

convert w to metres first and then make sure its negative
and then work out the reciprocal

and then do the equation

and then times by 1000 at the end!

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19
Q

Human eye refracts w 2 ocular structures

A

cornea = 2/3 refraction 40D
lens= 1/3 refraction 20D
overall= 60D

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20
Q

3 elements to focus light

A

shape of cornea,
power of lens
and length of eyeball

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21
Q

far point and near point

A

furthest distance a person can see without glasses or contact lenses. can be at infinity, behind or in front of an eye.

near point= closest point at which a person can see an object in perfect focus without glasses or cl

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22
Q

focal point

A

where parallel light meets after passing through the lens.
can be at the macula in front of the macula or behind the macula or retina.

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23
Q

myopia

A

focal point is in front of the retina
far point is in front of the retina
blur circle is formed on the retina

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24
Q

myopia and why

A

focal point is in front of the retina
far point is in front of the retina
blur circle is formed on the retina

if cornea is too curved or if the lens is too powerful (refractive ametropia)
or bc eye is too long or combination of these (axial ametropia)

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25
Q

hyperopia

A

focal point is behind the retina, far point is behind eye and image formed behind retina. blur circle on retina. corrected with positive lens.accom can fix this if young

could be bc cornea is too flat or if lens is too weak (refactive ametropia)
or bc eye is too short or combination (axial ametropia)

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26
Q

astigmatism

A

usually occurs with myopia or hyperopia
irregular curvature of cornea or lens. light rays focus in different locations.

theres 2 focal points 1st and second. use cylindrical lens to correct this

light can hit at one meridian and other.

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27
Q

2 types of astigmatism

A

against the rule (cornea more curved in horizontal meridian)

with the rule (cornea more curved in vertical meridian))

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28
Q

correction

A

amount of power in D needed to bring rays of light back onto focus on the retina

if + hyperopia
if - myopia

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29
Q

visual acuity

A

sharpness of vision measured by the ability to discern letters or numbers at a given distance according to a fixed standard.

distance= 6m for far
near= 40cm

30
Q

visual acuity

A

sharpness of vision measured by the ability to discern letters or numbers at a given distance according to a fixed standard.

distance= 6m for far
near= 40cm

snellen chart= widely used
problem= scale is not linear, crowded, hard notation

31
Q

minimum angle of resolution

A

reciprocal of snellen fraction

logMAR= log 10 of the minimum angle of resolution (MAR)
bailey lovie charts. same no of test letters but easier to use

32
Q

how does the log mar thing work

A

each letter read correctly= -0.02 logmar
logmar- (0.2 times no of letters read)

33
Q

picture snellen

A

lea symbol chart- based on logmar principles and uses shapes

unaided vision- check va with glasses and test worst eye first

n-notation- N= height of letter. 1/72 of an inch. N5= 5/72 inches/ etc

jaeger and m notation

if you cant recognise letters-
orientation of rotated snellen c
tumbling E orientation of prongs
key card point matching
picture or symbol charts
teller nad keller acuity cards
cardiff acuity cards
logmar acuity cards

34
Q

vision in spherical ametropia and lens

lens and ciliary muscles and accom at near

A

Rx can affect va
accom and pupil size also afects va

lens- shape isnt fixed. its responsible for accomodation= eye changes its power by the lens changing its shape.

ciliary muscles are relaxed= lens zonules taut, lens flattened.
ciliary muscles contracted= lens zonules relax and lens surface becomes fat= power=accom

distant-cm relaxes
near- cm contracts lens fat= accom

35
Q

vision in spherical ametropia and lens

lens and ciliary muscles and accom at near

A

Rx can affect va
accom and pupil size also afects va

lens- shape isnt fixed. its responsible for accomodation= eye changes its power by the lens changing its shape.

ciliary muscles are relaxed= lens zonules taut, lens flattened.
ciliary muscles contracted= lens zonules relax and lens surface becomes fat= power=accom

distant-cm relaxes
near- cm contracts lens fat= accom
(as age increases lens flexibility decreases and hence power decreases=presbyopia)

36
Q

near vision triad

A

convergence- inward movement of eyes towards each other
pupil miosis- constriction as accom
acccomodation= increases lens power

37
Q

emmetropia, hyper and myopia accomodation

A

not using accom for distant
near= closer distance= increases power of eye

accom= ray has to bend through a larger angle to focus them onto the retina.

hyperopia- can accom to bring it forward
near= accom all the time

myopia= cant as it brings it more forward

38
Q

length of standard eye

A

22.22mm
longer then myopia
if shorter than hyperopia

39
Q

power

A

+60D
if higher than myopia
if lower than myopia

40
Q

ametropia what it does to pupil size and blur circle with va.

A

decreases pupil size decreases blur circle and increases vision.

large pupil= blur circles overalp and cant be resolved.

so we can use pinhole aperture to decreases pupil size of the retinal blur circle to get the best acuity. if vision does not improve w pinhole then vision loss is due to non refractive causes eg disease.

41
Q

decimal notation

A

snellen numbers divided

42
Q

Astigmatic ametropia if

A

The eye displays 2 different refractive powers in 2 planes when meridians are perpendicular to each other. 2 focal points instead of 1.

Cone or rugby ball shape. Steeper meridian more curved= light is refracted more by this curvature and least by the flattest curvature. (Ocular astigmatism)

43
Q

Spherical ametropia

A

Same curvature over the entire surface
Light is refracted by the same amount when it passes= -> one sharp focus

44
Q

Corneal, lenticular and ocular astigmatism, with and against and oblique

A

Corneal astigmatism- major source of astigmatism. Measured w keratometer.
Lenticular- astigmatism by anterior and posterior surfaces of lens being tilted. Calculated by taking corneal readings away from the total astigmatism.

Corneal and lenticular total astigmatism.

Ocular astigmatism- regular if meridians are 90 degrees apart
Irregular- meridians any angle apart not perpendicular Ocular can be with the rule or against. With- more curved in vertical and against is more curved in horizontal.

Oblique- one meridian lies between 120 and 80 and other between 30-60

45
Q

What is the circle of least confusion

A

Dioptric midpoint between the anterior and posterior focal point. We need to move this onto the retina

This is the sphere power+ (cyl power/2)

46
Q

Classification of astigmatism (regular)

A

Simple hyperopic astig - focal line 1 on retina and one behind. Plano and positive
Compound hyperopic- focal line 1 and 2 behind retina. Both positive.

Simple myopic astigmatism-focal line 1 on retina and one in front. Plano and negative.
Compound myopic- focal line 1 and 2 are in front of the retina. Both negative.

Mixed astigmatism- focal line 1 in front of retina and one behind retina, pos and neg.

Larger difference- larger distance between 1st and 2nd focal line.

47
Q

Vision in uncorrected astigmatism and what is it affected by

A

Accommodation isn’t too useful as 2 focal points
Stretched or distorted

Affected by: amount of astigmatism, types of astigmatism, axis direction

48
Q

Optimum vision

A

When circle of least confusion on retina. Can happen in simple or compound hyperopia if enough accommodation. Otherwise need to fix

Oblique is likely to affect vision more.

49
Q

How to correct astig

A

1st= put 2nd focal line on the retina by adding + or - lenses
2nd= then add - cylinders to push the 1st focal line left to the retina

+lenses= pushes it left
- lenses= pushes it right

If you add + lenses it pushes both focal lines left. And then you need to push it right using negative lenses.
If you add - lenses moves it right then you put second focal line onto as well so add - again

50
Q

Indirect vs direct mag and fov

A

Indirect-
typical M= times 2- times 5
Typical fov= 25-45 degrees

Direct-
Typical M= times 15
Typical fov= 10 degrees

51
Q

What affects indirect

A

Pupil size effecting diameter
Condensing lens power
Distance from patient to lens
Distance lens to observer
Ametropia

52
Q

retinoscopy used to to what

A

Objective
Used to measure patients Rx
Useful and accurate

Screen for ocular disease: keratoconus, media opacities
Specialist retiniscope- next year, accommodative stability, accommodative lag
Dynamic ret- next year
Wd= 67cm
Can put in drops to relax accommodation

53
Q

Describe the retinoscope

A

Eyepiece- light source - spot/streak bulb.
Collar- needs to be kept down= divergent light rays

The ret reflex is normally red or orange. Trial lenses are addd till reversal. Estimate Rx. Remove working distance. 1/0.67= 1.50 so minus 1.50

54
Q

Where is the ret reflex

A

Appears to be located in the patients pupil but it’s anywhere front or behind.
If accommodation is relaxed external image is formed at the far point of the eye.

55
Q

Vergence of light rays

A

Dependent on patients Rx

Emmetrope= rays leave parallel far point at infinity
Myope- rays leave convergent far point In front of eye
Hyperope- rays leave divergent far point is virtual. Only converging light focuses on the retina.

56
Q

Far point explaining the patient and examiner eye thing

A

If far point is behind patient= hyperope with
If between patient and examiner- myope and against
If behind examine low myope= with

Far point should be coincidental w examiners ret.
neutral- no movement. Bright. Fast.

57
Q

If with and against and over correction snd neutral

A

Add positive lenses till neutral
Against= add negative lenses till neutral
Overcorrection= against

Neutral lean forward with lean back= against to check.

58
Q

How to do ret

A

Accom relaxed= distance
Dim room illumination
Px observes target at 6m
Wd=2/3m
Both eyes open
Use ret in right hand when examining left eye
Keep the same wd

Adding lenses moves the far point to the examiners ret.
Fog the other eye = against

Neutral= fast, bright, no movement;

59
Q

If -1D what does that tell us

A

1/ far point
So here far point is 1m in Front of patients eye

60
Q

No movement

A

Wouldn’t add anything bc neutral
Far point is at the retina

61
Q

If neutral does this mean the person is an emmetrope

A

No, it means the far point is at the examiners ret

This doesn’t mean the person is an emmetrope. Emmetrope= far point at infinity so you still need to bring this to the retinoscope to check the eye. And you add positive lenses to do this.

62
Q

2 ways to vary the working distance

A

Add lenses to vary the far point plane
Vary wd, only do this if at neutral

63
Q

If power is pos or Neg

A

You know if it’s in front or behind

64
Q

How to correct w spherical sylindrical lenses

A

Correct slowest with first or fastest against

65
Q

Variations in ret and cycloplegia and methods of ret

A

Can use trial frames, ret bar, or phoropter.

Cycloplegia- relaxed accommodation by relaxing ciliary muscles. Pupils get dilated. Ensures we know patients real Rx

Methods of ret- streak, Spot or static ( patient fixated on a distant target w accom relaxed)

66
Q

Near fixation or Barrett’s method

A

Used when examiner is unable to do ret accurately with both eyes eg lazy eyes
Only one of practitioners eye is used
Perform ret on both eyes of Px whilst patient fixates the ret and then check spherical component

Ret at near- and ret at distance. Do near one for both eyes and then distant one for the eye that is good for examiner. Them work out difference and the And apply this difference in both eyes.

67
Q

Mohindra

A

Useful in children that cannot fixate distant targets

Dark room
Fixates ret light
Wd=50cm monocular
Correc of -1.25D

68
Q

How to do ret in opacities, large pupil and keratoconus

A

Opacities- if in centre can’t really do it but dilate pupil or move closer
Large pupil- focus at the centre

Keratoconus- cone shape, Sllit or scissor reflex, use lens step larger than 0.25D and use bracketing technique.
Increase room illumination to decrease pupil size

69
Q

Factors affecting accuracy of ret

A

Intra-individual variation (same people)
Inter individual variation (between diff people)
Not concentrating on movement in centre of pupil
Age of px
Off axis errors
Wd errors
Blocking pxs errors of chart-> likely stimulating accom

70
Q

Speed of reflex

A

Important in estimating neutral point

Dioptric power= reciprocal of distances

CP1 mid sessionals term 1 (3 decks)

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