Penny Shaw MSc, FCOptom Types Effects Hypermetropia Axial length too short or refractive power too low Light would focus behind retina Accommodation needed to bring.
Download ReportTranscript Penny Shaw MSc, FCOptom Types Effects Hypermetropia Axial length too short or refractive power too low Light would focus behind retina Accommodation needed to bring.
Slide 1
Penny Shaw
MSc, FCOptom
Slide 2
Types
Effects
Slide 3
Hypermetropia
Axial length too short or
refractive power too low
Light would focus behind
retina
Accommodation needed to
bring image into focus
Accommodation is
the increase in power
of the intraocular
lens effected by
contraction of the
ciliary muscle
Slide 4
Effects of Hypermetropia
Nothing!
Tired, irritable eyes
Headaches
Blur N and/or D – transient or permanent
Increased problems in low light
Slide 5
Myopia
Axial length too long or refractive
power too high
Focal plane infront of retina
Accommodation is no use
Slide 6
Effects of myopia
Blur beyond far point
(e.g. -1.00
myopia = blurred after 1m)
Glare from light sources
affects night driving / flying
Occasionally headaches
Slide 7
Astigmatism
Irregular curvature of the
refractive surface(s),
usually the cornea
2 or more focal planes
Simple/myopic/hyperopic/
mixed
Accommodation is of little
use
Irregular astigmatism
results from corneal ectasia
(eg. keratoconus), scarring,
surgery
Bar to military flying
Slide 8
Effects of astigmatism
Blur D and N
Doubling or ghosting of image
Point sources spread along
orientation of astigmatism
Glare in bright light
Headaches
Slide 9
Presbyopia
Slide 10
Effects of presbyopia
Blurring at near
Headaches
Eyestrain/tired eyes
after near work
Difficulty refocusing to
distance after near work
First noticed in dim
light / poor contrast
(cockpits, maps!)
Slide 11
Questions?
Slide 12
Slide 13
Snellen chart at exactly 6 metres (or
other known distance)
Well illuminated (preferably
internally)
Use occluder, avoid pressing on eye,
squeezing eye shut or looking
through fingers
Record smallest line correctly read
Note: people have good memories!
Slide 14
Recording vision
Standard testing distance: UK=6m, US=20ft
Vision recorded as the fraction: test distance/letter
size
“Standard vision”: UK 6/6, US 20/20
“Standard vision”: Each limb of the letter subtends 1’
arc at the eye
Letter size increases iaw similar triangles: e.g 6/12
letter is double the size of 6/6 letter
Can also be recorded as decimal e.g. 6/6=1.0,
6/12=0.5, 6/3=2.0
Slide 15
Recording vision
Snellen
<6/60
6/60
6/36
6/24
6/18
6/12
6/9
6/6
6/4
PULHEEM S
V = vision without correction
8
VA =Visual acuity with correction
7
PULHEEMS Recording under EE
6
R V/VA L V/VA
5
e.g. 7/2 4/1
4
R Unaided 6/60 corrects to 6/9,
3
L Unaided 6/18 corrects to 6/6
2
1
1
Slide 16
Questions?
Slide 17
Convex
Concave
Toric
Recognition
Slide 18
Convex lenses - recognition
Thicker in the middle
Magnifying effect
Face looks larger
within spx frame
“Against” movement
of image
Slide 19
Convex lenses - use
Correction of hyperopia
and presbyopia
Slide 20
Concave lenses - recognition
Thinner in the middle
Minifying effect
Face looks smaller
within spx frame
“With” movement of
image
Slide 21
Concave lenses - use
Correction of myopia:
Slide 22
Toric lenses - recognition
Can be concave, convex,
simple or mixed
Swivel test produces
“scissor” effect
Slide 23
Toric lenses - use
Correction of
astigmatism
Refraction determines
the position and
orientation of each
focal plane
Slide 24
Spectacle lenses
Convex
Spx lenses are thin,
curved to improve
visual comfort and
appearance
Concave
Slide 25
Questions?
Slide 26
Slide 27
Subjective refraction
Aim
To determine the lens strength
needed to focus parallel light from
distant object on to the retina of the
relaxed eye
Slide 28
Subjective refraction
Use maximum plus to ensure
relaxed accommodation
Use minimum minus to ensure
accommodation is not stimulated
Clearest image with relaxed eye
Slide 29
Subjective refraction
Slide 30
Subjective refraction
Best sphere
Fit trial frame correctly
Record monocular vision including Ph vision
Unaided vision: correspondence to degree of
refractive error esp. myopia
6/12 approx -1.00
e.g 6/60 approx -3.00,
Uncorrected hyperopia may not blur vision
Slide 31
Subjective refraction
Start with +ve lenses
•Start with
+1.00
•Does it blur?
NO
Yes
•Add +1.00
•Try +0.50
instead
•Does it blur?
•Does it blur?
No
Yes
Yes
•Try +0.50
•Try +0.25
instead
•Try +0.25
•Does it blur
•Does it blur?
•Does it blur?
No
•Reject last
change
END POINT –
Record VA
Slide 32
Subjective refraction
Move to –ve lenses if myope
Note unaided vision: start with appropriate strength
e.g. V6/12 start with -1.00
•Is it clearer ?
Yes
•Add -0.50
No
• Add -0.50
• Is it clearer ?
•Is it clearer?
Yes
• Reject and add -0.25
instead
• Is it clearer?
No
• Reject and confirm
with +1.00
• Does it blur by about 3
lines?
Yes
Record VA
• END POINT REACHED
Slide 33
Subjective refraction
Best sphere – final check
Final check with +1.00 should blur vision by ~ 3
lines
If VA remains below Ph level, consider
astigmatism correction
Slide 34
Questions?
Slide 35
Types
Aftercare
Issues
Slide 36
Slide 37
Spectacles vs CL in aviation
Depends on A/C type
CFS mist up, restrict field of view, fall to bits,
hurt
CL: Some issues mainly to do with lens
dehydration.
CL generally preferred to CFS
Daily disposables preferred
Survey of Refractive correction in RAF Aircrew :2004: Shaw P, Scott RAH,
Mushtaq B, Coker W
Refractive Correction in RAF Aircrew: 2006: Partner A, Scott RAH, Shaw P,
Coker W
Slide 38
Lens types
Daily disposable: sph or toric designs,
hydrogel/silicone hydrogel
FRP: hydrogel/silicone hydrogel
replaced weekly, 2-weekly or monthly.
Durable: tailor-made hydrogels
Complex fits eg keratoconus kerasoft (hydrogel or silicone hydrogel)
Slide 39
Modalities
Daily wear with daily disposable or FRP
Flexible wear: occasional overnight use
Continuous wear: up to 30 days
Orthokeratology (OK): overnight rigid lenses
give temporary correction
Slide 40
Aftercare intervals
Daily wear
Extended /flexible wear
Initial fitting
Initial fitting
7-10 days
1 week daily wear
1-3 months
6 months
(practice lens handling)
After 1st overnight wear
1 week CW
3 months
6 months
Slide 41
Aftercare checks
Vision: stability, over refraction
Fit/comfort
Wearing times
Compliance
Lens handling
Ocular response
Slide 42
CL in aviation - advantages
Full field of view
Integration with head furniture
No misting
Aesthetics!
Slide 43
Contact lens complications
(very few!)
Subjective:
Drying
Excess movement
Poor/fluctuating vision
Lens supplies/storage
Solution use/storage
Slide 44
Contact lens complications
Objective:
Corneal oedema/
hypoxia
Drying
CLPU
Slide 45
Contact lens complications
Poor lens hygiene
Lid reactions
MK
Slide 46
Questions?
Penny Shaw
MSc, FCOptom
Slide 2
Types
Effects
Slide 3
Hypermetropia
Axial length too short or
refractive power too low
Light would focus behind
retina
Accommodation needed to
bring image into focus
Accommodation is
the increase in power
of the intraocular
lens effected by
contraction of the
ciliary muscle
Slide 4
Effects of Hypermetropia
Nothing!
Tired, irritable eyes
Headaches
Blur N and/or D – transient or permanent
Increased problems in low light
Slide 5
Myopia
Axial length too long or refractive
power too high
Focal plane infront of retina
Accommodation is no use
Slide 6
Effects of myopia
Blur beyond far point
(e.g. -1.00
myopia = blurred after 1m)
Glare from light sources
affects night driving / flying
Occasionally headaches
Slide 7
Astigmatism
Irregular curvature of the
refractive surface(s),
usually the cornea
2 or more focal planes
Simple/myopic/hyperopic/
mixed
Accommodation is of little
use
Irregular astigmatism
results from corneal ectasia
(eg. keratoconus), scarring,
surgery
Bar to military flying
Slide 8
Effects of astigmatism
Blur D and N
Doubling or ghosting of image
Point sources spread along
orientation of astigmatism
Glare in bright light
Headaches
Slide 9
Presbyopia
Slide 10
Effects of presbyopia
Blurring at near
Headaches
Eyestrain/tired eyes
after near work
Difficulty refocusing to
distance after near work
First noticed in dim
light / poor contrast
(cockpits, maps!)
Slide 11
Questions?
Slide 12
Slide 13
Snellen chart at exactly 6 metres (or
other known distance)
Well illuminated (preferably
internally)
Use occluder, avoid pressing on eye,
squeezing eye shut or looking
through fingers
Record smallest line correctly read
Note: people have good memories!
Slide 14
Recording vision
Standard testing distance: UK=6m, US=20ft
Vision recorded as the fraction: test distance/letter
size
“Standard vision”: UK 6/6, US 20/20
“Standard vision”: Each limb of the letter subtends 1’
arc at the eye
Letter size increases iaw similar triangles: e.g 6/12
letter is double the size of 6/6 letter
Can also be recorded as decimal e.g. 6/6=1.0,
6/12=0.5, 6/3=2.0
Slide 15
Recording vision
Snellen
<6/60
6/60
6/36
6/24
6/18
6/12
6/9
6/6
6/4
PULHEEM S
V = vision without correction
8
VA =Visual acuity with correction
7
PULHEEMS Recording under EE
6
R V/VA L V/VA
5
e.g. 7/2 4/1
4
R Unaided 6/60 corrects to 6/9,
3
L Unaided 6/18 corrects to 6/6
2
1
1
Slide 16
Questions?
Slide 17
Convex
Concave
Toric
Recognition
Slide 18
Convex lenses - recognition
Thicker in the middle
Magnifying effect
Face looks larger
within spx frame
“Against” movement
of image
Slide 19
Convex lenses - use
Correction of hyperopia
and presbyopia
Slide 20
Concave lenses - recognition
Thinner in the middle
Minifying effect
Face looks smaller
within spx frame
“With” movement of
image
Slide 21
Concave lenses - use
Correction of myopia:
Slide 22
Toric lenses - recognition
Can be concave, convex,
simple or mixed
Swivel test produces
“scissor” effect
Slide 23
Toric lenses - use
Correction of
astigmatism
Refraction determines
the position and
orientation of each
focal plane
Slide 24
Spectacle lenses
Convex
Spx lenses are thin,
curved to improve
visual comfort and
appearance
Concave
Slide 25
Questions?
Slide 26
Slide 27
Subjective refraction
Aim
To determine the lens strength
needed to focus parallel light from
distant object on to the retina of the
relaxed eye
Slide 28
Subjective refraction
Use maximum plus to ensure
relaxed accommodation
Use minimum minus to ensure
accommodation is not stimulated
Clearest image with relaxed eye
Slide 29
Subjective refraction
Slide 30
Subjective refraction
Best sphere
Fit trial frame correctly
Record monocular vision including Ph vision
Unaided vision: correspondence to degree of
refractive error esp. myopia
6/12 approx -1.00
e.g 6/60 approx -3.00,
Uncorrected hyperopia may not blur vision
Slide 31
Subjective refraction
Start with +ve lenses
•Start with
+1.00
•Does it blur?
NO
Yes
•Add +1.00
•Try +0.50
instead
•Does it blur?
•Does it blur?
No
Yes
Yes
•Try +0.50
•Try +0.25
instead
•Try +0.25
•Does it blur
•Does it blur?
•Does it blur?
No
•Reject last
change
END POINT –
Record VA
Slide 32
Subjective refraction
Move to –ve lenses if myope
Note unaided vision: start with appropriate strength
e.g. V6/12 start with -1.00
•Is it clearer ?
Yes
•Add -0.50
No
• Add -0.50
• Is it clearer ?
•Is it clearer?
Yes
• Reject and add -0.25
instead
• Is it clearer?
No
• Reject and confirm
with +1.00
• Does it blur by about 3
lines?
Yes
Record VA
• END POINT REACHED
Slide 33
Subjective refraction
Best sphere – final check
Final check with +1.00 should blur vision by ~ 3
lines
If VA remains below Ph level, consider
astigmatism correction
Slide 34
Questions?
Slide 35
Types
Aftercare
Issues
Slide 36
Slide 37
Spectacles vs CL in aviation
Depends on A/C type
CFS mist up, restrict field of view, fall to bits,
hurt
CL: Some issues mainly to do with lens
dehydration.
CL generally preferred to CFS
Daily disposables preferred
Survey of Refractive correction in RAF Aircrew :2004: Shaw P, Scott RAH,
Mushtaq B, Coker W
Refractive Correction in RAF Aircrew: 2006: Partner A, Scott RAH, Shaw P,
Coker W
Slide 38
Lens types
Daily disposable: sph or toric designs,
hydrogel/silicone hydrogel
FRP: hydrogel/silicone hydrogel
replaced weekly, 2-weekly or monthly.
Durable: tailor-made hydrogels
Complex fits eg keratoconus kerasoft (hydrogel or silicone hydrogel)
Slide 39
Modalities
Daily wear with daily disposable or FRP
Flexible wear: occasional overnight use
Continuous wear: up to 30 days
Orthokeratology (OK): overnight rigid lenses
give temporary correction
Slide 40
Aftercare intervals
Daily wear
Extended /flexible wear
Initial fitting
Initial fitting
7-10 days
1 week daily wear
1-3 months
6 months
(practice lens handling)
After 1st overnight wear
1 week CW
3 months
6 months
Slide 41
Aftercare checks
Vision: stability, over refraction
Fit/comfort
Wearing times
Compliance
Lens handling
Ocular response
Slide 42
CL in aviation - advantages
Full field of view
Integration with head furniture
No misting
Aesthetics!
Slide 43
Contact lens complications
(very few!)
Subjective:
Drying
Excess movement
Poor/fluctuating vision
Lens supplies/storage
Solution use/storage
Slide 44
Contact lens complications
Objective:
Corneal oedema/
hypoxia
Drying
CLPU
Slide 45
Contact lens complications
Poor lens hygiene
Lid reactions
MK
Slide 46
Questions?