Exam Questions Flashcards
1
Q
Describe the design of the ishihara colour vision test
A
Colour confusion test
plates are phedu Isochromatic ( fake 1 colour)
1st plate in every test fake demo
4 Seconds per Plate
not every plate will have Something on it
only finds Red or green defect
in a 28 plate edition 4 wrong = fail
2
Q
What lightening should be used to illuminate the ishihara test
A
daylight source of colour temperature 6500k tungsten no good
3
Q
when using the Ishihara Colour vision test. what is the recommended working distance?
A
7 5 cm
4
Q
Explain the meaning of the following terms related to colour vision
Dueteranomaly
Protanopia
Rod Monochromacy
A
-Deoteranormaly - Green definecy appears grey
Protanopia - Red definecy
Rod Monochromacy- only one photo pigment works.
5
Q
what is the most Common type of congenital colour vision defect
A
red and green more common in males than in females
deuteranomaly
anomalous trichromacy
6
Q
State 2 causes of aquired color vision defect(10)
A
Congenital - inherited photo pigments abnormalities
excessive use of therapeutic drugs
disease or Injury that damage optic neve
7
Q
give 2 ways in which acquired colour vision defects may differ from Congenital defects
A
aquired - develops to Ocular Conditions- or Side effects of medications or toxic effects of Chemicals,trauma aging
Congenital - Inherited at birth In curable and do not Change
8
Q
Define the terms depth perception and Stereopsis (10)
A
Death perception ~ visual ability to Perceive the world In 3D
Stereopsis - Perception of depth produced by the reception in the brain of usual Stimuli from both eyes In Combination
9
Q
A monocular subject may use the following clues to experience depth perception
overlapping Geometric perspective Relative size Aerial perspective Parallax
In one Sentence give brief definition of each of these clues (25)
A
Overlapping - the object in the background obscured by objects in foreground Seem further Away
Geometric . parallel lines narrowing gues perception of been further Away
relative give . objects further away Seem to be smaller
Aerial - further away less contrast
Parallax - determine distance doe to Speed Something is travelling Slower Seems to be further Away
10
Q
what range of values would be considered to be normal for stereoacuity
A
.20 - 40 Sec’s of Arc
11
Q
How is stereoacuity affected by
Pupil distance
Amblyopia
A
PD - larger PD = better SA
Amblyopia - worse SA
12
Q
Define Presbyopia (15)
A
loss of elasticity of the lens
loss of eyes ability to focus on near objects
starts to happen from age 40 +
13
Q
state 2 changes that Occur within the eye that contribute to Presbyopia (10)
A
14
Q
show on a diagram how amplitude of accommodation varies with age (20)
A
13 D at 13 years of age then less 0.25D Per year
Amp = 18 - ( 1/3 Patients age)
15
Q
what’s meant by the term depth of field (10)
A
Distance between nearest and farthest objects that arein Sharp focus In an image
16
Q
How does depth of field affect the value of the amplitude of accommodation as measured using the push- up method (5)
A
Increases
17
Q
A Subject with a -1.00D of myopia has anamplitude of accommodation of +1.50D. what is the Power of the lens (to the nearest 0.25D) that would be required for close Work at 36cm (20)
A
18
Q
Explain how astigmatism may be classified according to the positionof the focal lines formed by a distant Point object relative to the retina (25)
A
Simple Myopia 1 line on retina other in front
Simple Hyperopia 1 line on retina 1 line behind
compound Myopia both line in front
Compound Hypermyopia both behind
mixed 1 Infront 1behind
19
Q
LV
compare the practical advantages and disadvantages of mounted Spectacles magnifiers + monocular Near vision Spectacles Telescopes include 4 points
A
spec Mounted telescopes Can provide longer working distance, Can provide higher amount of magnification
can be variable focus
have significantly restricted foV
easie to provide illumination to object for spec mounted telescopes
20
Q
State criteria for registration as Sight impaired
A
3/60 → 6/60 full visual field
6/60→ 6/24 moderate field loss
6/18 or better + gross field defect
21
Q
Explain what is meant by the terms
Myopia
Axial Hypermetropia
far point
A
myopia- light from a distant object is focused in front of the macula of an unaccommodated, uncorrected eye
Axial - the Power of the reduced Surface is standard while the axial length is Shorter than +22.22mm light from a distant object is focused behind the macula of an un accommodated,uncorrected eye
far point - the Point Conjugate by refraction with the macula of the uncorrected unaccommodated eye
22
Q
A Patient has Snellen acuity of 6/36 explain what this fraction represents
A
6= testing distance 36 = Distance at which smallest letter CX can read Subtends 5' of Arc
23
Q
What would 6/ 36 be as decimal
A
6/36 = 0. 16667
24
Q
explain log Mar
A
logarithmic value of minimum angle of resolution in minutes
25
logmar acuity of 0.0 What Snellan acuity does this represent
6/6
26
3 advantages in using baily lovie chart Instead of a Snellen chart
equal number of letters on each line
works @ different working Distances still acurate each gaps different when going down chart
consistant 0.1 log until progression in letter height between rows
letter Spacing= letter height - reduce visual Crowding
27
Define near point and amplitude of accommodation
near point - Conjugate with the macular by refraction at the fully accommodated uncorrected eye (b)
Amp Of acc the maximum accomodation the eye can exert
amp = k-B
28
State 2 advantages applying to all prescriptions of contact lenses over spectacles
```
cosmetic
Improved fov
no magnification
Sports
Sunglass choice
less aberrations
no prismatic effect
```
29
State 2 Specific Conditions in which C L may be used for therapeutic reasons
Keratoconus - Improve VA through Corneal Surface +tear layer
Albinism - coloured CL reduces blordisc and photophobia
ectropian- bandage CL
High myopia - Reduction in Spectacle magnification
30
Briefly describe a typical Problem which a new wearer of RGP might experience during adaption
What advice
Problem- Discomfort due to lens and lid interaction
Problem- eyelids will touch lens when blinking
advice - increase Wear time slowly
if noticable look down for a few moments
use conditioning Solution to help with wetting
31
briefly describe shape of Cornea
oval in shape average measurements are 11mm horizontally
10mm vertically
radi average 8 - 8.5
32
explain terms edge lift when applied to RGP including reason for its presence
the final curve I'on the back surface of the contact lens is slightly flatter this Is to aid tear exchange + helps lens removal
33
name 2 preservaies currently used in RGP CL Soaking Solutions
Polyhexanide
Hydrogen peroxide
EDTA
34
list instructions which you would give to a CX when advising Safe removal of RGP lens which has moved onto the Superior bulbar Conjunctiva
wash+ Dry hands
look into mirror
Carefully reposition the CL onto Cornea through the eyelid
35
State 1 typical diameter of Scleral contact lens
21-25mm
36
State 1 typical diameter of f rigid contact lens
8.5-10.5mm
37
State 1 typical diameter of a soft contact lens
13.5 - 14.5mm
38
How does the BOZR of a rigid contact lens usually relate to the Central radius of curvature (k reading) of the cornea
The BOZR of an RGP Contact lens is the Same as the flattest k reading
39
How does the BOZR of a soft contact lens usually relate to the Central radius of curvature (k reading) of the cornea /
The BOZR of a soft cL is 0.8mm - 1mm flatter than the flattest K reading
40
State 1 typical K reading
8.00mm
41
State 2 advantages of rigid gas permable contact lenses over traditional (non - Silicone) soft contact lenses (30marks)
```
Improved VA
Good for astigmatism VA + fit
Improved hygiene
myopia control
Greater amounts of Oxygen
High Rx range
```
42
list signs which maybe present in Someone who is suspected of having a microbial Keratitis
```
Signs
closed eye
Swollen eyelids
Hyperaemia
Lacimation
Reduced VA
wearing Sunnies + Photophobia
corneal staining (SIit lamp)
Central corneal ulcer ( Slit lamp)
Anterior chamber Involvement
```
43
list Symptoms which maybe present in Someone who is suspected of having a microbial Keratitis
(40 marks fo Signs + Symptoms )
```
Symptoms
pain
Sudden onset Possibly on lens removal
Red eye
lacrimation
Poor vision
Photophobia
```
44
name a bacterium which is a common cause of microbial Keratitis
Staphylococcus aureus, pseudomonas aeruginosa
45
name a Virus which is a common cause of microbial Keratitis
Herpes Simplex
Zoster
adenovirus
46
name a fungus which is a common cause of microbial Keratitis
canidida Albicans
| fusarium solani
47
name a protozoa which is a common cause of microbial Keratitis
Acanthamoeba
48
A contact lens wearer who appears to be displaying Signs + Symptoms for Keratitis
You are alone in practice
Describe course of action which you should take (40 marks)
Any painful + redeye should cease CL wear immediately but keep Cl in case as made need to determine cause
```
As a Do I would contact local opticians to try get CX in to See optom or clo if not - refer to local eye hospital Or A + E,would contact them ahead to make aware to expect cx,give referral letter with main details on
and include
Relevant history + Symptoms
Signs
VA On the day
Take CL + case to hes
```
49
Name the document which a Prospective wearer must possess before anyone can commence a contact lens fitting Include 3 Criteria which this document must satisfy (40 mark)
the Eye Exam findings/ Prescription / Statement
Signed and in date (2 Years)
Patient details
50
state 2 advantages of scleral contact lenses over rigid Corneal contact lenses (40 marks)
Good for therapeutic fitting
can be used for instilling drugs
High Rx range
51
in traditional non Silicone Soft contact lenses
| What is the main advantage of a high water Content material over a low water content material
Increases the amount of oxygen which reaches the Cornea
Improved comfort
easier to handle
52
state 1 disadvantage of a high water content material (30 marks)
can dry out more than lower water content lenses
53
name + describe two findings which might be recorded at an aftercare appointment following slit lamp examination (40 marks)
tear breakup time
Comeal and Conjunctival Staining
R GP lens fitting
54
State 2 reasons for the use of the Keratometer at a routine aftercare appointment (30 marks)
check for Pathological Conditions
check non - Invasive tear break up time
check Corneal Integrity
55
list 2 other elements of a routine contact lens after care (30 marks)
```
History and Symptoms
contact lens compliance
check vision + VA + over refraction
check lens fitting + lens condition
check Spectacle visual Acuity
feedback + Future actions
```
56
Briefly describe the condition keratoconus (30 marks)
A collagen disorder of the Cornea
the Cornea thins and is displaced down and in from the Central position
the Cornea is distorted + Cone shape
onset is usually lateteens to early 20 's
57
Describe an advantage,Specific to keratoconus of contact lenses over Spectacles and explainthe reason behind this advantage (30 marks)
contact lens give improved vision as the tear film can be used to correct the astigmatism and provide a Smooth refracting Surface
58
list 4 designs of CL that could be used in Keratoconus (40 marks)
Scleral C L
RGP
Hybrid CL
Piggy back
59
A man visits your practice with a red,Painful watery RE.He tells you that his eye Suddenly felt uncomfortable yesterday when he was walking in windy conditions,whilst wearing his RGP CL
state 2 Possible causes of his discomfort ( 30 marks)
```
foreign body (Corneal abrasion) Discomfort,lacrimation
Microbial Keratitis - pain photophobia reduced VA
```
alone in practice cause for action
Remove cl ( keep +case)
Go to A + E
Record actions and advice
60
Describe 4 main advantages of RGP comeal lenses compared to Silicone hydrogel Soft lens
```
improved VA
Corneal astigmatism Corrected with Spherical lens
fewer deposits
myopia Control
more oxygen
High Rx range
less allergic reactions
can be modified
```
61
Describe 1 advantage of modern RGP materials when Compared to the older PMMA material
improved oxygen transmission
62
Describe one disadvantage of modem RGP materials over pmma (15)
lenses are not as comfortable
| more likely to break/damage
63
state 1 typical diameter of a Cornea (HVID) (15)
11 mm
64
for the cornea above (11mm) what would be a typical total diameter for Corneal RGP lens
Soft lens
Scleral lens
RGP = 9. 5mm
Soft . = 14.2mm
scleral = 22mm
65
according to uk legislation List 4 c lasses of Professionals who may legally fit contact lenses (20 marks)
Registered medical Practitioner
Registered optometrist
DO who holds an approved qualification and is registered on GOC
Trainee CLO or pre reg optometrist Under Supervision
66
if a patient is not from your practice requests contact lenses.what document must the Patient show you before you may supply lenses ?
include 3 items of info which must be contained in this document (40 marks)
contact lens Specification
Date fitting commenced
Date specification Expires
Patients details ( DOB if under 16)
Practice details
CL details from which CL can be replicated
Pr actioner details and registration number
67
give 2 examples of important information that fluorescein Sodium Can provide during on initial Contact lens assessment (30 marks)
check for Corneal Integrity and damaged cells
check for dry eye
tear breakup time
conjunctival Staining
68
name a Common finding which might be seen and noted after in stilling fluorescien at initial CL assement (30 marks)
Tear quality - Instill fluorescein - Ask Cx to blink count how many Seconds forthe tear film to start to break up
Record this as TBUT
corneal Staining - fluorescein stains any dry or damaged cells
This can range from dryness to a mechanical stain from CL wear ( previous wearer) Any Cornealdamage needs to be clear before CL fitting can Commence
69
name 4 Structures which are examined with the slit lamp during an Initial CL assesment ( 40 Marks)
```
Cornea epithelium,Stroma,endothium
Conjunctiva - Bulbar,limbal,Palpebral and tarsal
Lids + lashes
limbal blood Vessels
Tear film
```
70
List the advantages a patient with microphthalmos is likely to experience if they were fitted with contact lenses for distance compared to wearing spectacles include 4 advantages (20 marks)
increased field of view
reduced weight
fewer aberrations
reduced reflection
71
describe the symbol cane explain the purpose of this cane and describe how it is used by a visual impaired patient
foldable white cane indicates px is visually impaired extends cane and holds diagonally across body or keeps folded and holds across chest
72
state the defination of severely sight impaired as laid down by the national assistnce act (1948)
so blind as to be unable to perform any work for which eyesight is essential
73
what non optical aid can you advise to help a patient make a cup of tea safely. Describe this aid and explain how this aid works
Liquid level indicator
has 3 prongs hangs over edge of cup
middle prong shorter
when water hits prongs device will make noise and vibrate patient can add milk middle prong will activate once touches liquid
74
if a patient consents to having their name entered onto the register for severely sight impaired. what will happen next within the registration process
assesment of needs will be undertaken
75
3 advantages of spectacle magnifiers
hands free
larger field of view
not too expensive
psycholically more acceptable
76
explain how a telescope can be used to increase their Field of view for a patient with peripheral visual field loss
Reverse Galilean telescope
| minifies image so remains on central part of retina
77
what does the pelli-robson chart measure
measures contrast sensitivity
78
name a non optical aid that may assist a patient seeing the dials on their cooker
enlarger numbers stickers or bumps ons
79
which is the form currently used in Britain to certify someone as serverly sight impaired
RVI form certificate of vision impairment
80
after certification of the patient list who recieves copies of the form
GP
Local Authority
college of optometrists
81
differentiate between a symbol cane and a long cane by stating the use of each
symbol cane used to indicate person has a visual impairment
long cane used for mobility
82
explain the term terrestrial telescope
/an astronomical telescope withan erector system
83
explain the term reading cap
positive lens placed in front of the telescope objective to adapt it for use with a near object
84
explain the term telemicroscope
A telescopic unit designed to view objects closer than infinity
85
explain visual field
the area in space that can be seen when fixating on a point
86
```
state if the following patients would be eligible to be certified as sight impaired. serverely sight impaired or not eligible for certification
Patient with
Va 3/60 full visual field
VA 1/60
diagnosed with early AMD with VA of 6/18
```
sight impaired
severely sight impaired
not eligible
87
why can the measurement from the pelli-robson chart be considered more useful than snellan chart for the practitioner assessing the low vision patient (15)
snellan chart measures in high contrast and most LV patients have greater difficulty in low contrast. Pelli- robson assesses visual function in real life situation rather than black and white of sight test assesses effect of contrast and likely success with aids
88
Distinguish between heterophoria and hetertropia
Heterophoria- in normal binocular vision with both eye fixating there is no deviation. If 1 eye occluded or binocular vision prevented then 1 eye will deviate
Heterotropia- one eye will alwyas deviate. The 2 visual axis are never directed in the same place
89
```
with reference to heterotropia, explain the meaning of the follwoing terms
convergent
divergent
unilateral
alternating
```
Convergent -1 visula axis rotates nasally compared to the other axis
Divergent- 1 visual axis rotates outwards compared to other eye
unilateral- the deviation is always in the same eye
alternating- can switch/ change between each eye either eye can take up fixation
90
concomitant
incomitant
constant
intermittent
concomitant- when angle between 2 visul axis remains the same when viweing distance & near objects what ever position
incomitant- angle between 2 visual axis is compared to object distance position
constant- amount of deviation there all the time
intermittent- comes and goes under certain circumstances
91
what is meant by
dissociated
associated heterophoria
dissociated- 2 eyes presented with completly diff targets so that fusion reflex is presented
associated- the amount of phoria meassured usinga test in which part of the image is the same for both eyes (mallet unit)
92
explain the stage depression of loss model. include a minimum of 4 facts
lack of engaement with professional
feelings of worthlessness
poor memory of interaction
feelings of hopelessness of outcome
93
how will patients age influence the sucessful use of a low vision aid (4 facts)
less likely to accept
dexerity issues
more likely to have additional needs/health issues
difficult to learn new skills
94
what is the benefit of testing contrast sensitivity
(5marks answer) gages visual performance in real world
| (15 mark answe)- allows us to predict the likely sucess of LVA's allows us to gage weather contrast advise is warrented
95
describe the structure of pelli-robson chart
```
8 rows
6 letters per row
in groups of 3
letters same size
each triplet has different contrast
varis from 89% - 0.5%
use at 1m
use in good lightling
progress is logerithmic
```
96
other things to take into consideration other than visual Field and vA maybe to be registered as sight impaired
```
impact on life
home situation
other additional needs
Age of onset
emotional state
physical ability
```
97
the patient is suffering from visual hallucinations. what is name of syndrome
charles bonnet
98
explain what is meant by the terms
myopia
axial hypermetropia
far point
Myopia- light from a distant object is focused in front of the macula an unaccommodated, uncorrected eye
axial hypermetropia- the power of the reduced surface is standard while the axial length is shorter than +22.22mm. Light from a distant object is focused behind the macula of an unaccommodated, uncorrected eye
far point -the point conjugate by refraction with the macula of the uncorrected unaccommodated eye
99
describe key features of a landolt ring
attends 5' of arc at specified distance
| presented to cx with gap at different positions
100
describe how a landolt ring used in practice
minimum angle between 2 objects so eye can resolve as seperate
move away from cx until no gap can be seen
move towards until gap detected
measure distance from cx to landolt C + size of gap
MAR =tan-1 (size of gap/distance to patient)
x by 60 to get minutes of ARC
101
an eye has an ocular ametropia of -1.00 and the nearest object that it is able to focus on is at 25cm from the reduced surface. What is the amplitude of accomodation of this eye
K=-1.00D
b=-25cm
AMp= k-B
B=n/b = 100/25= -4.00D
AMP = K-B = -1.00- -4.00= +3.00D amps of accommodation
caluculate the range of clear vision of the eye?
```
k= n/K = 100/-1.00=-100cm
range = -25cm to -100cm
```
102
Give defininitions of the terms emmetropia and ametropia
Emmetropia - An unaccommodated, uncorrected eye will focus distant light ion the macula- far point lies at infinity and in conjugate with the macula
Ametropia - An uncorrected, unaccommodated ametropic eye will not focus distance light on the macula- eyes far point is not at infinity - some degree of refractive error
103
calculate the power of the lens placed at 12mm required to correct an axially ametropic reduced eye with an axial length of +20.83 (30Marks)
K'= 4/3 x1000 / 20.83= +64.01D
K=K'-Fe = +64.01 - (+60.00) = +4.01D
FSP = k/1+dK = 4.01/ 1+(0.012 x 4.01) = +3.83D
104
Define spectacle magnification
spectacle magnification is the magnification of the retinal image due to the spectacle lens
SM= height of retinal image in corrected ameetropic eye/
Height of retinal image in uncorrected ametroipc eye
=hc/hu'
105
a subject with a refractive ametropia of +10.00D is corrected for distnce vision by +9.00D. Assuming that it is a thin lens. What spectacle magnification does it produce
SM=hc/hu'
| = +10.00/+9.00 = 1.11
106
The corrected eye in previous question view a distant object subtending 2 degrees calculate the size of the retinal image
K=+9.00
K'= +60.00
-1000 tan w /K'
= -1000tan(2)/60 = -0.58
hc'=hu'xSM = -0.58 x 1.11= -0.65
107
Define the terms orthphoria, heterophoria and hetertropia
Orthophoria= straight state eyes are in ideal position for distance and near objects -visual axes always remain directed towards fixation object even whe eyes dissociated
Heterophoria- other state-the visual axes are directed towards the fixation object when the eyes are associated but deviate when dissocaited
hetertropia - manifest squint- only the visual axis of the eye that can fixate will pass throughthe object of regard deviation always present angle can vary
108
A heterphoria can be described as uncompensated what does this mean
where the eyes are unable to align properly - causes strain on muscles as causes cx to correct over correct,compensate for misalignment
109
explain what is meant by fixation disparity
Twinned single oints on the retina are too simplistic. The retina has elliptical zones and if the images falls within these then there will be no diplopia
110
Why is it necessary to dertermine Weather a hetertropia is concomitnat or non concomitant? (10Marks)
concomitant means the angle between visual axis are the same , incomitant varis with direction of gaze.
111
state 2 forms of treatment that maybe used in heterotropia
112
mildest colour defect
Anomalous trichromacy all 3 photopigments are present but one is less sensitive
113
How is stereoacuity affected by
interpupillary distance
Amblyopia
```
PD = longer PD = better Stereo acuity
Amblyopia = Worse Stereoacuity
```
114
Give definition for snellan acuity and Minimum angle of resolution (MAR) (20marks)
snellan based a chart around letter recognition as opposed to resolving gratings. Letter decreased in height allowing the patient to remain seated in a test room tested at 6m as eyes natural depth of field can over come this
The angle (meaursed in minutes of arc) subtended at the nodal point of the eye by 2 points which can just be distinguished as seperate
115
what is the height of a 12m snellan letter
tan5' = letter height/ letter size therefore
letter height = tan5' x letter size
=tan0'5' x 12 x 1000 (mm) = 17.45mm
116
what is the purpose of an optometer
To measure ametropia . device that measures refractive error
117
explain the difference between a subjective optometer and an objective optometer
Subjective - Determines refractive error by analysing response from the patient ( eg Snellan)
objective - no response - (eg Autorefractor/ ret )
118
Name 3 signs of diabetic retinopathy
```
retinal haemorrhages
hard exudates
retinal oedema
neovasucularisation
cotton wool spots
microaneuysm
venous dilation
```
119
State 3 disadvantage of spectacle magnifiers
short WD
thickness
increased TCA
Problems with illumination
120
state 3 advantages of spectacle magnifiers
better FOV than telscopes
Hands free
look normal
121
define term low vision
THe WHO defines low vision as visual acutity less than 6/18 and blindness as visual acuity less than 3/60 or visual field < 10 degrees
122
state the definition of serverly sight impaired as laid down by the National Assistance Act (1948)
Blind so blind to be unable to perform any work for which eyesight is essential
Partially sighted there is no legal defination of partial sight provided by the act gives guidance of- Substantially and permanently handicapped by defective vision caused by congenital defect or illness or injury
123
6 psychological stages a cx may go through when recently diagnosed with sight loss
```
depression
shock
realistic acceptance
denial
disbelief
Anxiety
anger
```
124
What is the pathological term used for the absense of the iris
Aniridia
125
What is the pathological term used for when the eyeball is abnormally small?
Microphthalmia
126
short notes
| Keratoconus (5 facts) (30 Marks)
Cornea cone shape
thinning of the cornea causes it to buldge into a cone shape
more common in males late teens to early 20's
can occur in one or both eyes
can caused blurred vision due to astigmatism
127
write short notes iris coloboma (5facts 30marks)
```
occurs at birth part of the eye does not fully develop
can cause light sensitivity
can affecrt one or both eyes
iris looks like a key hole shape
does not affect vision
```
128
shorts notes on albinism (5 facts 30 marks)
```
lack of pigment in the iris
photophobia
nystagmus
reduced VA due to development of retina
poor depth perception
abnomal curvature of eye causing astigmatism
```
129
A device intended to be postioned and supported by the users hand and without artifical support
hand magnifier
130
A magnifier in which the support is designed to position the optical system at a set or adjustable distance from the object to be viewed
stand magnifier
131
The distance from the magnifier surface nearest to the eye to the virtual image when the object is placed at teh designated position
exit image vergence
132
Agreed distance of 250mm between the anterior corneal vertex of the eye and the object observed
Reference seeing distance
133
Telescope mounted in or on a spectacle frame
Spectacle mounted telescope
134
An astronomical telescope to which has been added an erecting system
Terrestrial telescope
135
A Positive lens placed in front of a telcope objective to adapt the device for viewing a near object
Reading Cap
136
A negative lens placed in front of a near vision telescope/ telemicroscope objective to adapt the device for viewing distance object
Distance cap
137
Distance between the most anterior portion of a near-vision telescope/ telemicroscope and the object
free working distance
138
Device used by visually impaired persons to enhance vision
Low vision aid
139
state why the patient may suffer from asthenopia after prolonged use of the aid
Light is divergent when reaching the eye some accommodation will be required at an elderly age not much accommodation for prolonged periods of time
solve problem - cx to wera SVN specs
140
stand magnifiers may have various sources of power for internal illumination. Name 2 such power sources and name 2 such light sources. Name the most efficient light source currently available
Power sources- mains batteries rechargeable batteries
light sourses tungsten bulbs, halgen, fluorescent, LED
Most efficient - LED
141
List disadvantages of the Snellan chart for Low vision 6 facts (30 marks)
```
too few letters at lower acuties
non logrithmic design
no constant ratio between size of letters
non consistant spacing = crowding
not real life enviroments
designed for use at 6 metres
measures high contrast only
```
142
advantages of bailey lovie chart for assesment of low vision chart
```
logarithmic in design
constant ratio of letter size
line and spacing equal throughout
can be used at any WD
allows more accurate prediction of mag requirements
each line has 5 letters
```
143
Why is the measurement of contrast sensitivity considered useful in the assement of low vision patient
measures in real life situation assesses likely success of visual aids
144
compare the practical advantages and disadvantages of monocular Spectacles Magnifiers + Monocular Near vision Spectacles telescopes
Spec mounted telescopes can provide longer working distance
Spec mounted telescope can provide higher amount of magnification
can be variable focus
have significantly restricted f. O.V
easier to provide illumination to object for Spec mounted telescopes
145
Badal Optometer
A Single high powered len's around 16.00D
The lens is positioned So that he Second focal Point coincides with the plane of Spectacle lens which therefore measures Spectacle Prescription
one eye occluded the target is moved towards the Patient Until retinal Image appears clear
146
Scheiner Disc
opaque disc
38mm in diameter
2 Pinholes around 0.75mm- 1mm-
2-3mm Apart
147
what is meant by dissociated and associated
dissociated - 2 eyes Presented with completely different targets So that fosion reflex is presented
Associated - the amount of phoria measured using a test In which part of the image Is the same for both eyes ( mallet unit)
148
What is keratometry
measurereal - of radi of Curvature of the central Portion of the anterior surface of the Cornea
149
what is keratoscopy
examination of the shape of the corneal surface
150
Section C
| give a definition of Relative Spectacle magnification
Is the ratio of the retinal Image size in corrected ametropic eye Compared with retinal Image Size
151
.what is meant - when a keratometer Is described as being a one Position instrument
Single Mire
uses 2 doubling Prisms Opposed to are another
can read both principal Median from one Position
152
Explain the difference between anisometropia and anti metropia
anisometropia unequal refractive errors in two eyes
| antimetropia opposite refractive errors
153
what is meant by Indentation tonometry
measures the depth of corneal Indentation made by a Small plunger carrying a known weight.the higher the Iop the harder it is to push against and Indent Cornea
154
give definitions of Scotoma and hemianopia
Scotoma - blind spot or partial loss of vision
| hemianopia - blindness over half the field of vision
155
a subject with re fractive Ametropia of + 6.50 D Is Corrected for distance Vision by + 6.00D.Assuming that this lens is thin.What Would Spec magnification Produce
6.50 / 6.00 = 1.0833
View distance object a 2 degrees - calculate Retinal image size
hu' = - 1000 tan w / k ' =
-1000 tan 2 / 60.00 = -0.58
hc' = hu' x Sm= - 0.58 X 1. 0833 = -0.630
156
.How is the field of view affected by a Patients Myopia when examining the fundus using
Direct Ophthalmoscopy
indirect ophthalmoscopy
Direct - Reduced
| indirect - Unaffected
157
define term Stereopsis
| limit of Stereopsis
the perception of depth Produced by the reception in the brain of visual stimuli from both eyes
158
What range is normal for stereoacuity
2 - 40 Seconds of arc
159
what is the name of the early Colour Vision theory which states that there are 3 types of retinal receptor each responding to a different region ofthe Visible Spectrum
Trichromatic theory
160
name a test that can be used to determine Whether a Patients heterotropla is Comitent or Incomitant
mobility test or Hess Screen
161
accommodative esotropia meaning + treatment
is an Inward turn of one or both eyes can happen when child longsighted - they over focus
Prescribe glasses - helps eyes relax
162
Explain what is meant by refractive Surgery
Surgery to the eye to alter the patients refractive error
163
explain
version
Vergence
versions- conjugate Movement.the eyes move together binocularly and angles between the visual axis is constant
Vergences - Disjunctive Movements . eyes move in opposite directions
164
Grades of binocular vision
Simultaneous Perception lowest
fusion
Stereopsis
164
3 Types of Diplopia
Pathological
physiological
Prism Induced
165
simple optometer
```
consists of a sliding target
and a high Positive lens
mounted on a rod that's marked with Spec refraction
eye placed at required Vertex distance
relies or Image clarity
```
166
Disadvantages of Simple optometer
/ difficult to determine astigmatism
--non linear
Proximal accommodation will under correct hypermetropia and over Correct Myopia
retinal Image size varis
167
a maddox Rod placed in front ofthe left eye to be used to detect whether a Subject has exophoria or esophoria
What would be the the axis direction of the maddox Rod
Horizontal
168
if the left eye is looking through the Maddox Rod what would be used as a target for the right eye
Distance Spotlight
169
maddox Rod
| In order to determine what type of heterophoria is present what question would the subject be asked
Is the line Image on the right or left
170
maddox Rod
| what answer would the subject give if exophoria were present
line is on the right
171
Prisms can be used with the Maddox Rod to Measure the exophoria
what would the Subject see when the Correct Image is in place
the Spot and the line would be together
172
what would be the direction of the Prism used to measure the Exophoria
Base in
173
A heterophoria maybe described as Uncompensated what does this mean
Symptoms arise when fusion amplitudes are Inadequate to control deviation
muscular fatigue
eye strain
174
Push up method
using an RAF Rule
move the Slider for away from CX
instruct (x you will Slowly more Slider toward them along rule
at Some point the text will become blurry
when this happens they need to advise and you stop moving the Role
Read Position of the Slider on the Side of the ruler in distance/ dioptres
Repeat for other eye
175
explain what is meant by Convergence when related to eye movements
Aligns the visual axes with the object So two Images will fall on Corresponding retinal points
176
Define near point convergence
nearest point for which a subject can Converge whilst keeping Image on the fovea
177
A Subject with a PD of 66mom Views an object on the midline between the two eyes at a distance of 35cm from the Centres of rotation.calculate the Convergence required by each eye In Prism Dioptres
1/2 PD XMA
| ma = 1/d = 1/ 3.5 = 0.28 X 33 = 9.43 Prism each eye
178
homonymous
hemianopia
heteronymous hemianopia
congruous
homonymous -Same
hemianopia -1/2 visual field loss
heteronymous hemianopia- left or right of both eyes
congruous- Same in each eye
179
fixation disparity
defined as the difference between the target vergence angle and ocular Convergence angle during binocular fixation
180
indirect ophthalmoscopy
exon of the inside of the back of the eye using a beam of light and hand held lens - gives wider view of inside the eye
181
f acultative hypermetropia
manifest hypermetropia
which of these is equal to the amplitude of accomodation
facultative- can not overcome by accomodation
| manifest Cannot be overcome by accomodation
182
accommodative esotropia
is an Inward turn of oneor both eyes that can happen when a Child is longsighted
183
nystagmus
an involuntary rhythmic side to Side up+ down or Circular motion of the eye
Contact lens would move with the eye causing less distortion
184
Percervative In RGP lens
Polyhexamide
185
Define the terms near point and amplitude of accommodation
near point / The vergence required at the fully accomodated eye to form a clear retinal Image
AOA - maximum amount of accomodation an eye can exert
186
An eye has a Ocular Ametropia of -1.00D andthe nearest object that it is able to focus on is a 25cm from the reduced surface
What is the amplitude of accommodation
( 25cm - True near point )
Amp = K-B
B= n/ b = 100 / -25 = -4.00D
= - 1.00- -4.00 = + 3.00D
187
Keratometry
fixed doubling
variable doubling
fixed doubling- Power of prism is fixed
| variable doubling- only one fixed object - Power /position of prism changes
188
placido disc
Corneal topography examines the weall shape of the cornea and is useful when more complex lenses are required
the simplest tool is the placido disc
it is made up of a Series of Concentric black and while circles with a sight hole in the centre
KeratoScope
189
3 advantages of a non- contact method of tonometry
eliminates Corneal contact
eliminates Risk of infection
Does not need topical anesthesia
190
Definition of relative Spec Magnification
the ratio of the retinal . image Size in the corrected aretropic eye compared with the retinal Image size in the Standard Emmetropic eye
191
list 5 ocular Structures
```
lids + lashes - bletharitis - Smooth eyes
Cornea -
conjunctiva - smooth eyelids
Anterior chamber - blood cells
Iris - melanomia-
Limbus - Redness
```
192
Explain Inverse Square law
illuminance at a point on a Surface Perpendicular to a Source is In versely Proportional to the Surface of the distance from Source to Surface
E= I/ d2
193
cosine Square law
illuminance of a surface varies as the Cosine angle of Incidence
the greater the angle the Lower Illumination falling on Surface
E = I / d2 x cos ( angle)
194
luminous flux
rate of light flow from the Source in a given direction
195
illuminance
the amount of luminous flux falling on a surface
Symbol E
unit lux
196
Reflectance
A Ratio comparing the lomens of a flux leaving a surface to the lumens of a flox that were incident on the surface
197
Dry AMD
```
loss of central vision
3 stages early Intermediate,late
no treatment for late
certain medication may slow process
may struggle to See peoples faces
Colours are less bright
regular check ups
monitored at home using Amsler chart
straight lines may appear wavey
will more likely affect both eyes
Progresses slowly over Sereval years
```
198
EVES
```
vary mag
vary brightness / Contrast
auto focus
interact with image
Save image to View later
Portable
Screen reading technology
voice control
no abberations
improved FOV
```
199
PD: 62
| calculate Convergence required in MA and Prism If the spec may of +12.00 D is fitted 27 mm from eyes centre of rotation
PD: 60
F: +12.00D
S= 27
100/ 12 = -8.33 cm
MA = 1 / WD = 1 / I - S = 100 / -8.33-2.7=9.066
P = MA X mono CD= 9.066 X 3.1 = 28.18 each eye
200
State 3 disadvantages of Spec magnifiers
short WD
Poor illumination
weight /thickness
201
State 3 advantages of Spec magnifiers
increased fov
hands free
more acceptable
202
other than a reduced field of view state 2 other Symptoms of retinitis pigmentosa
Poor dark adaptation
| night blindness
203
another Patient Suffers from retinitis Pigmentosa Explain how a telescope can be used to increase their field at View
reverse telescope to minify Images so falls on central retina
204
state the 3 major causes of visual Impairment Certification in england and wales
ARMD
Glaucoma
diabetic Retinopathy
205
A Patient attends foa low vision assessment state how you would explain the Purpose of this appointment
Help cx use residual vision
enable required tasks to be Performed
aids independence
Improves qualily of life
206
structure of Pelli Robson chart
| 8 facts
```
8 Rows
6 letters Per row grouped into 2 triplets
logarithmic design
Used @ 1m
89% ~ 0.5% Contrast
Same size + spacing
Specific lighting needed
high to low contrast left - right, Top - bottom
```
207
advantages of contact lenses for Iris coloboma and howthese advantages are achieved
cosmetically better - handpainted to match look of other eye
better VA
reduced Photophobia
opaque backing reduces Light Scatter
208
3 Signs of diabetic retinopathy
Retinal haemorrhages
micro aneurism
macular Oedema
209
Give 2 reasons Why the results obtained with he simple optometer may not be accurate
Difficult to determine astigmatism
| Proximal accommodation will under/ over correct
