Optics/ Ophthalmic Optics Flashcards
(128 cards)
1
Q
For patient wearing RGP CL if you steepen the base curve by 0.75D how should you adjust the contact lens power?
A
Prescription should increase by -0.75D
** remember SAM FAP Steepen add minus
2
Q
Flattening the base curve of a lens induces?
A
Additional minus power of the tear film
**therefore to offset this power change need to ADD plus power to the Rx
**SAM FAP (Flat add plus)
3
Q
What adjustments can be made to a GP lens if it’s loose and moves too much? (4)
A
Options:
1. Steepen base curve
2. Increase optic zone diameter
3. Increase overall diameter (OAD)
4. Narrow peripheral curve system or steepen it
4
Q
Modifications to lens that fits too tight
A
- Flatten base curve
- Decrease OAD
- Decrease optic zone diameter
- Flatten peripheral curve
- Widen width of peripheral curves
5
Q
What formula is used to calculate induced prism?
A
P=dF
d in cm
F in diopters
6
Q
Tolerance for sphere powers +/- 6.50
A
+/- 0.13 D
(According to ANSI standards)
7
Q
What does ANSI stand for?
A
American National Standards Institute
8
Q
True or false
More strict tolerance for powers in lower power
A
True
9
Q
Error tolerance for cyl powers of 2.00 DC or less
A
+/- 0.13 D
10
Q
Over correction of near reading power will result in?
A
Reduced focal length
Causing patient to bring reading materials closer to
11
Q
Antimetropia
A
One eye is myopic, while other is hyperopic
12
Q
Refractive index of CR-39
A
1.498
* plastic
13
Q
Refractive index of crown glass
A
1.523
14
Q
Refractive index of Trivex
A
1.523
15
Q
Abbe value of polycarbonate
A
30
* low abbe= high chromatic aberration
16
Q
Abbe value of trivex
A
43-45
17
Q
Abbe value of CR-39
A
58
18
Q
Abbe value of crown glass
A
58
19
Q
Frame adjustment
If right lens is in
A
Move right temple in (or left temple out)
20
Q
Frame adjustment
If left lens is in
A
Move left temple in (or right temple out)
21
Q
Frame adjustment
If right lens is out
A
Move right temple out (or left temple in)
22
Q
Frame adjustment
If left lens is out
A
Move left temple out (or right temple in)
23
Q
If frame not straight on face
Right lens is up how would you fix it?
A
Bend right temple up (or left temple down)
24
Q
If frame not straight on face
If left lens is up
A
Bend the left temple up (or right temple down)
25
If frame not straight on face
If right lens is down
Bend right temple down or left temple up
26
If frame not straight on face
If left lens is down
Bend left temple down or right temple up
27
Drop ball test for dress lenses to be considered impact resistant
5/8 inch steel ball weighing 0.56 oz dropped from distance of 50 inches
28
Terrien’s marginal degeneration causes what type of astigmatism?
Against the rule (ATR)
29
True or false
Increasing index of refraction of lens material will allow for decrease in lens thickness
TRUE
* thinner lenses and may also lower specific gravity which minimizes overall weight of glasses
30
What is the far point when uncorrected?
Assume constant pupil size and relaxed accommodation.
OD: -6.75 DS
** take inverse of subjective refraction
1/ -6.75 =-0.148 or 14.8 cm
* if object is placed at this distance from the eye, pt will perceive a clear image if left uncorrected
31
Which ophthalmic instrument will provide the most accurate method of assessing spectacle lens warpage?
Lens clock
* used to calculate base curve of spectacle lenses, determine add power of Multifocal lens, determine slab-off prism, calculate thickness of GPCL
32
Which lens material has the greatest amount of reflection at its incident surface?
Polycarbonate n= 1.586 (refractive index)
33
Jackson cross cylinder
RX will have spherical equivalent of 0
Example: +1.00 -2.00 x 180
34
What factors contribute to development/progression of myopia in young children? (5)
1. Family history of myopia (especially if both parents are myopic)
2. Prolonged near activities on a consistent basis
3. Presence of ATR astigmatism
4. Children emmetropic or have less than 0.50 D hyperopia at school age
5. Long axial length (> 24mm)
(Normal average axial length: 24mm)
35
What is the annual progression rate of myopia in children?
0.25 to 0.50 diopters annually
36
Marfan syndrome, ROP and Ehlers Danlos syndrome are most associated with what refractive error?
High myopia
37
Leber congenital amaurosis, cornea plana and nanophthalmos present with what refractive error?
High hyperopia
38
Normal A-scan length
22-25 mm
39
Patients with high myopia have axial lengths of ____mm or longer
26.5 mm
40
Which races have the highest predilection to pathological high myopia?
Japanese
Chinese
Jewish
Arab
* rare in AAs
41
What is a common characteristic of pathologic myopia related to the eye's length?
Increased axial length
## Footnote
Increased axial length is a key indicator of pathologic myopia.
42
What is observed in patients with pathologic myopia concerning the lens?
Premature lenticular pacification
## Footnote
This refers to the early clouding of the lens in myopic patients.
43
What type of eye alignment issues may be present in pathologic myopia?
Large exophoria or exotropia
## Footnote
Exophoria and exotropia are conditions related to outward eye deviation.
44
Posterior staphyloma
outpouching of the sclera that can occur in high myopia.
45
What abnormality may occur regarding the optic discs in pathologic myopia?
Oblique insertion of the discs
## Footnote
This refers to the atypical positioning of the optic nerve head.
46
What are lacquer cracks in the context of pathologic myopia?
breaks in Bruch’s membrane
*can cause CNVM
* seen in pathological myopia due to stretching long axial length
47
What change in the vitreous is noted in pathologic myopia?
Syneresis of the vitreous
## Footnote
Syneresis refers to the shrinkage of the vitreous body, which can lead to complications.
48
What type of membranes can develop subretinally in pathologic myopia?
Subretinal neovascular membranes
## Footnote
These membranes can lead to vision loss due to their growth and subsequent complications.
49
What serious retinal condition can occur in patients with pathologic myopia?
Retinal detachments
## Footnote
Retinal detachments are a critical complication that can severely impact vision.
50
What is foveal retinoschisis?
splitting of the retinal layers at the fovea and is associated with high myopia.
51
What visual symptom may patients with pathologic myopia report?
Decreased visual acuity
## Footnote
Decreased visual acuity is a common complaint among individuals with pathologic myopia.
52
Fill in the blank: Patients with pathologic myopia may experience image _______.
minification
## Footnote
Image minification is the perception of images being smaller than they are.
53
What impairment in color perception might occur in pathologic myopia?
Impaired color vision
## Footnote
This refers to difficulties in distinguishing colors, potentially due to retinal damage.
54
What abnormal adaptation to darkness may patients with pathologic myopia experience?
Abnormal dark adaptation
## Footnote
Abnormal dark adaptation refers to the difficulty in adjusting to low light conditions.
55
FDA class of SCL Group 1
Low water, non-ionic
56
Which group of the FDA classes of SCL is least likely to develop deposits?
Group 1
*low water, non-ionic
57
What is the recommended method for measuring distance PDs?
Use a pupillometer
## Footnote
The pupillometer is noted as the most accurate method for measuring distance PDs.
58
What should be done to the frame before taking fitting measurements?
Fit and fully adjust the desired frame on the patient's face
## Footnote
Adjustments include pantoscopic tilt, frame height, vertex distance, face-form wrap, and nose-pad alignment.
59
What must be checked regarding the overall circles on the centration chart?
One of the large overall circles must completely enclose the frame's lens shape
## Footnote
This is vital for ensuring the correct lens size and shape.
60
Fill in the blank: The standard method for taking progressive lens fitting measurements includes measuring distance PDs _______.
monocularly
61
True or False: The fitting height measurements can be accurate if the frame is not pre-adjusted.
False
## Footnote
Incorrect adjustments can lead to inaccurate fitting height measurements.
62
What adjustments can be made for a patient reporting decreased field of view through near portion of progressive glasses?
Increase pantoscopic tilt
* 10-12 degree angle is recommended
* field of view in near zones of PAL are widest when near zone sits as close to the eyes as cosmetically and physically as possible
63
Which area of the progressive lens should be used to verify the distance prescription when glasses arrive from the lab?
Center of the distance arc
64
What does a progressive lens prescription typically contain?
Removable markings for prescription verification and fitting purposes
## Footnote
These markings are essential for ensuring the lenses are made according to the specified prescription.
65
What is the purpose of the Distance Reference Point (DRP)?
Indicates the recommended position for measuring the distance prescription with a lensometer
## Footnote
This ensures accurate fitting and prescription verification.
66
What is the Fitting Cross used for?
To verify the fitting height
## Footnote
The Fitting Cross should be centered on the patient's pupil for proper alignment.
67
What do the two horizontal dashes next to the Fitting Cross indicate?
Help to determine whether the lens is level or tilted
## Footnote
This is important to ensure proper vision correction.
68
What is the purpose of the Near Reference Point (NRP)?
Used to verify the near add power
## Footnote
The NRP is located at the center of the circle in the lower part of the lens.
69
Fill in the blank: The PRP is the same as the _______.
Major Reference Point (MRP)
## Footnote
Both points are used for verifying prism power.
70
How to verify near add power on a PAL that has arrived from the lab?
Near reference point (NRP)
* located at the center of the circle of the lower part of the lens
71
What parameters can be modified to improve GP contact lens performance?
Comfort, fit, centration, clarity
## Footnote
These parameters can be altered in the office with a modification unit.
72
How is minus power added to a contact lens?
By holding the suction cup attached to the concave side against the modification unit's sponge tool
## Footnote
The central convex surface (F1 surface) of the lens must be in contact with the sponge tool.
73
What should be done while pressing the lens against the sponge tool?
Rotate the lens counterclockwise while the sponge tool revolves clockwise
## Footnote
This ensures even modification of the lens surface.
74
What is a crucial step after modifying the contact lens?
Remove and evaluate frequently to ensure no warpage is induced
## Footnote
This also helps verify that too much minus power is not added unintentionally.
75
What procedures can be performed in the office on GP lenses?
Polishing of the F1 surface, re-edging the lens, decreasing overall diameter, truncating the lens
## Footnote
These modifications aim to enhance lens comfort and positioning.
76
What should be exercised when modifying high Dk lens materials?
Extra caution
## Footnote
High Dk materials may require special handling to avoid damage.
77
What are the conditions to ensure during the modification process?
Both the modification tool and lens should be sufficiently wet, adequate polish used
## Footnote
This prevents overheating of the lens.
78
What can happen if too much pressure is applied during the modification process?
The optics may become distorted due to lens warpage
## Footnote
Careful pressure application is essential for maintaining lens integrity.
79
What is a common characteristic of patients with pathological myopia?
Increased axial length
## Footnote
Pathological myopia is often associated with elongation of the eyeball.
80
What condition related to the lens is frequently observed in pathological myopia?
Premature lenticular pacification
## Footnote
This refers to the clouding of the lens occurring earlier than usual.
81
What type of eye alignment issues may be seen in patients with pathological myopia?
A large exophoria or exotropia
## Footnote
Exophoria indicates a tendency for the eye to drift outward.
82
Which type of glaucoma is associated with pathological myopia?
Open-angle glaucoma
## Footnote
This is the most common form of glaucoma, characterized by a gradual increase in eye pressure.
83
What structural abnormality is often found in the eyes of those with pathological myopia?
Posterior staphyloma
## Footnote
A posterior staphyloma is an outpouching of the wall of the eyeball.
84
What abnormality may occur regarding the optic disc in pathological myopia?
Oblique insertion of the discs
## Footnote
This refers to an unusual alignment of the optic nerve head.
85
What are lacquer cracks in the context of pathological myopia?
Lacquer cracks
## Footnote
These are breaks in the retinal pigment epithelium due to stretching.
86
What vitreous condition is associated with pathological myopia?
Syneresis of the vitreous
## Footnote
This describes the liquefaction and shrinkage of the vitreous gel.
87
What type of membranes may develop subretinally in patients with pathological myopia?
Subretinal neovascular membranes
## Footnote
These membranes can lead to serious vision complications.
88
What serious retinal condition can occur in patients with pathological myopia?
Retinal detachments
## Footnote
This condition can lead to permanent vision loss if not treated promptly.
89
What visual distortion can patients with pathological myopia report?
Image minification
## Footnote
This describes the perception of images appearing smaller than they are.
90
What type of visual field changes may occur in pathological myopia?
Visual field defects
## Footnote
These can manifest as blind spots or areas of reduced vision.
91
What color vision issue might patients with pathological myopia face?
Impaired color vision
## Footnote
This can lead to difficulties in distinguishing between colors.
92
What abnormality in vision adaptation might be reported by patients with pathological myopia?
Abnormal dark adaptation
## Footnote
This refers to difficulty adjusting to low light conditions.
93
What happens when prescribing minus cylinder power with an axis of 180 degrees?
Minification of images in the vertical meridian
## Footnote
Objects will appear stretched horizontally.
94
What is the effect of prescribing minus cylinder power with an axis of 90 degrees?
Minification of images in the horizontal meridian
## Footnote
Objects will appear stretched vertically.
95
What do patients often note when undergoing a large myopic shift or wearing glasses for the first time?
Overall minification of objects
## Footnote
This observation is generally more pronounced with glasses than with contact lenses.
96
Slab off prism is base ____
Base up
* slab off prism used to eliminate diplopia, it is applied to the most minus or least plus lens (because minus lenses are thickest at the edges and slab off prism is base-up, helps to minimize thickness difference)
97
98
What is acetone commonly used for?
Nail polish remover
99
Can acetone be used to remove markings from polycarbonate lenses?
No
100
Why should acetone not be used on polycarbonate lenses?
It can lead to pacification of the lenses and cause small stress fractures
101
What happens when acetone comes in contact with polycarbonate?
It quickly diffuses into the plastic and causes small stress fractures
102
Which materials are safe to use for cleaning polycarbonate lenses?
Dish soap, water, and acetic acid (vinegar)
103
What are the components of many lens cleaner sprays?
Water, isopropyl alcohol, and soap
104
Fill in the blank: Acetone can lead to _______ of the lenses when used on polycarbonate.
pacification
105
True or False: Isopropyl alcohol is harmful to polycarbonate lenses.
False
106
Increasing pantoscopic tilt on a pair of glasses will increase _____ power
Sphere power
107
Increasing face wrap will induce?
Astigmatism
108
109
Methods to eliminate double vision while reading
- prescribe slab off prism over weaker eye
- prescribe reverse slab off prism (base down) over stronger eye
- prescribe 2 pairs of single vision glasses, one for distance and one for reading
110
What happens when prescribing minus cylinder power with an axis of 180 degrees?
Minification of images in the vertical meridian, causing things to appear stretched horizontally.
111
What is the effect of prescribing minus cylinder power with an axis of 90 degrees?
Minification of images in the horizontal meridian, causing things to appear stretched vertically.
112
What do patients experience when they undergo a large myopic shift or wear glasses for the first time?
An overall minification of objects while wearing their visual correction.
113
How does the perception of minification differ between glasses and contact lenses for myopic patients?
The observation is generally more pronounced with glasses than with contact lenses.
114
What perception do patients experience with a large hyperopic shift or when wearing correction for hyperopia for the first time?
Objects within their visual field appear magnified while wearing their glasses.
115
Is the perception of magnification more noticeable with glasses or contact lenses for hyperopic patients?
Typically more noticeable with glasses than with contact lenses.
116
Pantoscopic tilt rotation induces minus cyl with axis 180 for a ________ lens. And axis 090 for a ______ lens.
Minus cyl with axis 180 for minus lens
Minus cyl with axis 090 for plus lens
117
Face form tilt rotating lens around 090 meridian induces minus cyl with axis 090 for a _____ lens, and axis 180 for a _____ lens.
Induces minus cyl with axis of 090 for a minus lens and axis 180 for a plus lens
118
Where should the segment height for trifocals be measured?
Lower edge of pupil margin
119
True or false
If a child with latent hyperopia only complains about difficulty with near vision, you should prescribe the full cycloplegic distance refraction for distance and reading
FALSE
* only prescribe it for near vision
* allows patient to use normal amount of accommodation to achieve clarity of near vision
120
Can you clean polycarbonate lenses with acetone?
**NO**
Acetone is a solvent that will cause small stress fractures
use instead: dish soap, water, isopropyl alcohol
121
Where is the segment height measured for PALs?
At center of pupil to the bottom of the deepest portion of the lens
122
123
124
125
What happens when prescribing minus cylinder power with an axis of 180 degrees?
Minification of images in the vertical meridian
## Footnote
This causes objects to appear stretched horizontally.
126
What is the effect of prescribing minus cylinder power with an axis of 90 degrees?
Minification of images in the horizontal meridian
## Footnote
This results in objects appearing stretched vertically.
127
What do patients experience when undergoing a large myopic shift or wearing glasses for the first time?
Overall minification of objects
## Footnote
This effect is generally more pronounced with glasses than with contact lenses.
128
What may patients report when experiencing a large hyperopic shift or wearing correction for hyperopia for the first time?
Objects within their visual field appear magnified
## Footnote
This perception is typically more noticeable with glasses than with contact lenses.
