Spectacle technique II
Practical exercises
Print version
Table of Contents
1
1 Calculation of horizontal decentration of spectacle lens in spectacle frame ................................. 1
2 Calculation of spectacle lens vertical decentration......................................................................... 3
3 Spectacle lens vertex distance measurement................................................................................. 6
4 Spectacle frame pantoscopic angle measurement ......................................................................... 9
5 Spectacle frame wrap angle measurement................................................................................... 11
6 Spectacle frame pressure relation measurement......................................................................... 13
7 Spectacle frame static relationship measurement ....................................................................... 16
8 Aniseikonia correction with spectacle frame adaptation ............................................................. 19
9 Taxation of the prescription for spectacles and optical aid.......................................................... 21
10 Choice and recommendation of spherical/cylindrical single vision lens from the catalogue....... 25
11 Choice and recommendation of bifocal lens from the catalogue................................................. 28
12 Choice and recommendation of progressive and degressive lens from the catalogue................ 31
13 Choice and recommendation of lenticular lens from the catalogue ............................................ 34
14 Choice and recommendation of prismatic lens from the catalogue............................................. 37
Literature............................................................................................................................................... 40
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1
1 Calculation of horizontal decentration of
spectacle lens in spectacle frame
Introduction
Position of the spectacle lens centration point is equal to optical spectacle lens in lenses without
prismatic effect (Rutrle, 2001). Position of the spectacle centration we can find out if we draw points
(pupil position) with the pencil right on the demo-foil or we can calculate it without drawing on
demo-foil (see exercise 5 in Spectacle lens technique I).
Goals
• Measure pupillary distance of the patient
• Measure size of the frame according the boxing system
• Measure size of the bridge according the boxing system
• Calculate the size of horizontal decentration in relation to centre of the eye frame for right
and left side
Equipment
Digital and handy PD meter, writing equipment, spectacle frame
Methods
Measure pupillary distance of the patient
Use digital or handy PD meter and measure pupillary distance right and left.
Measure size of the frame according the boxing system
Measure size of the spectacle frame (from center of the right eye frame to the left eye frame).
Measure size of the bridge according the boxing system
Measure size of the spectacle bridge. It is size from the edge of right eye frame to the edge of the left
eye frame. Use boxing system.
Calculate the size of horizontal decentration in relation to centre of the eye frame for right
and left side
According the bellow formula, calculate size of the horizontal decentration for right and left
spectacle lens (h – horizontal decentration right and left, c – frame size, PD is pupillary distance right
and left)
ℎ 𝑅,𝐿 =
𝑐
2
− (𝑃𝐷 𝑅,𝐿) [mm] (16)
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Results
Measure pupillary distance of the patient
PDR =
PDL =
Measure size of the frame according the boxing system
c =
Measure size of the bridge according the boxing system
d =
Calculate the size of horizontal decentration in relation to centre of the eye frame for right
and left side
hR =
hL =
Draw schematically spectacle frame according boxing system and measure and mark its
parameters.
Discussion
The size of the horizontal decentration is important for proper grinding of the spectacle lens. If the
grinding is manual we use TABO-schema for decentration of the spectacle lens. If we use automated
grinding machine we put horizontal decentration data in to the centration instrument called tracer.
Conclusion, notes, comments
Which type of horizontal decentration calculation would you choose for your practice?
How horizontal decentration limits choice of the spectacle lens diameter?
If we get horizontal decentration as negative number, what does it means?
3
2 Calculation of spectacle lens vertical
decentration
Introduction
Spectacle lens vertical decentration is important for correct centration of different spectacle lenses.
Spectacle lens is correctly centered if the optical axis of this lens goes to real eye’s point of rotation,
Spectacle frame has 10 degrees pantoscopic angle. For this purpose, we mark position of the pupil if
the patient has so called perpendicular view.
Picture 2.1: Usage of the so-called perpendicular view (inspired by Rutrle 2001).
Goals
• Measure height of the pupil to the bottom of the frame according the boxing system
• Measure height of the eye frame according the boxing system
• Calculate vertical decentration right and left
Equipment
Spectacle frame, handy or digital PD meter, writing staff, calculator
Methods
Measure height of the pupil to the bottom of the frame according the boxing system
Put the frame on patient and correctly adapt it. Consequently, adapt the head of the patient to be
the frame perpendicular to the floor. Now you can mark position of the pupils of the right and left
4
eye on demo-foil. Or you can height of the pupil measure right with the handy ruler. Height of the
pupil we measure according the boxing system.
Measure height of the eye frame according the boxing system
Draw schematically spectacle frame in protocol and mark and measure all important parameters. For
calculation we need the parameter b which means height of the eye frame.
Calculate vertical decentration right and left
With help of bellow presented formula calculate vertical decentration for right and left eye. The
parameter ymeans height of the pupil and parameter b is height of the eye frame.
𝑣 𝑅,𝐿 = 𝑦 𝑅,𝐿 −
𝑏 𝑅,𝐿
2
[mm] (17)
Results
Measure height of the pupil to the bottom of the frame according the boxing system
yR =
yL =
Measure height of the eye frame according the boxing system
b =
Calculate vertical decentration right and left
vR =
vL =
Drawing of the spectacle frame:
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Discussion
Correct centration is important for correct spectacle lens’ imaging. In general, we have to enable
condition for so called point imaging. Usually we center aspherical lenses on pupil if the spectacles
are adapted on perpendicular view. Centering on pupil in natural view is preferred for anisometropic
correction, high refractive index lenses and lenticular lenses.
Conclusion, notes, comments
How we can know if the frame is suitable for the patient?
What does it mean if the vertical decentration is negative?
How does spectacle frame’s pantoscopic angle influence vertical decentration?
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3 Spectacle lens vertex distance
measurement
Introduction
Vertex distance is measured from rear side of spectacle lens to front part of the cornea. Vertex
distance is important parameter which can change vertex power of the spectacle lens. We have to
respect this fact especially in change from spectacle lens to contact lens.
Goals
Measure vertex distance of spectacle lens in frame with handy PD meter
Measure vertex distance of spectacle lens in frame with special prismatic meter
Measure vertex distance of spectacle lens in frame with centration instrument
Equipment
Spectacle lens, handy PD ruler or PD meter, writing staff, calculator, centration instrument
Methods
Measure vertex distance of spectacle lens in frame with handy PD meter
Put the frame on examined person. With handy PD meter measure distance from back side of the
lens to front side of the cornea. You should measure it if the patient looks in infinity with
perpendicular view. Fixation axis should go through eye’s rotation center and center of the spectacle
lens.
Measure vertex distance of spectacle lens in frame with special prismatic meter
Use bellow listed picture and put the prismatic ruler right on the spectacle frame. Put the beginning
of the upper part of the scale on limbus and read the value in millimeters from the lower part of the
scale. Here you can see deviated image from the same side of the corneal limbus. From the bellow
listed picture we can read vertex distance 11 mm.
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Picture 3.1: Vertex distance measured with prismatic ruler (inspired by Optiboard 2013)
Measure vertex distance of spectacle lens in frame with centration instrument
Put the centration instrument right on the spectacle frame. On the side of the centration instrument
you can find the scale. From this scale you can read the distance from the back side of the spectacle
lens to the front part of the cornea.
Results
Measure vertex distance of spectacle lens in frame with handy PD meter
d1 =
Measure vertex distance of spectacle lens in frame with special prismatic meter
D2 =
Measure vertex distance of spectacle lens in frame with centration instrument
D3 =
Discussion
Currently we can measure vertex distance together with other important centration parameters as is
pantoscopic angle, wrap angle, spectacle frame size etc. with help of digital video centration system.
These centration systems contain camera and special software. For example, Hoya offer centration
system called VisuReal Portable, which can be a part of iPad. Essilor use centration system called
Visioffice etc.
8
Picture 3.2: VisuReal Portable offers by Hoya (Hoya 2013)
Conclusion, notes, comments
Which one from used technique for measurement of vertex distance is the most exact?
Which one from used techniques for measurement of vertex distance is fastest?
For which purpose is measurement of vertex distance important?
9
4 Spectacle frame pantoscopic angle
measurement
Introduction
Pantoscopic angle is the important parameter which is used for centration of spectacle lenses.
Pantoscopic angle in standard spectacle frame is usually 10 degrees. In this context is very important
to centre different spectacle lens with respect to this pantoscopic angle. For example, for traditional
progressive lenses is not suitable to choose spectacle frame with zero pantoscopic angle. This
spectacle frame has usually doubled side.
Picture 4.1: Pantoscopic angle of the frame (inspired by 2020mag.com 2013)
Goals
• Measure pantoscopic angle of the spectacle frame with protractor
• Measure pantoscopic angle of the spectacle frame with instrument for measurement of
pantoscopic angle
• Calculate vertical decentration of the spectacle lens’ optical centre with respect to pantoscopic
angle
Equipment
Spectacle frame, handy PD ruler or PD meter, writing staff, calculator, instrument for measurement
of the pantoscopic angle
Methods
Measure pantoscopic angle of the spectacle frame with protractor
Put the spectacle frame of the patient and adapt it to protect again falling down. With protractor try
to measure pantoscopic angle. The pantoscopic angle is angle between general vertical line and
10
vertical axis of the spectacle frame. Pantoscopic angle is usually from 5 to 15 degrees. If the angle is
smaller you can adapt the spectacle frame.
Measure pantoscopic angle of the spectacle frame with instrument for measurement of
pantoscopic angle
Let’s measure pantoscopic angle with instrument for measurement of pantoscopic angle. This
instrument is put on the spectacle frame and with gravity weight you can read pantoscopic angle of
the spectacle frame.
Calculate vertical decentration of the spectacle lens’ optical centre with respect to
pantoscopic angle
𝑣 = (𝑑 + 13) ∗ 𝑡𝑔𝛼 [mm], [°] (18)
Results
Measure pantoscopic angle of the spectacle frame with protractor
𝛼1 =
Measure pantoscopic angle of the spectacle frame with instrument for measurement of
pantoscopic angle
𝛼2 =
Calculate vertical decentration of the spectacle lens’ optical centre with respect to
pantoscopic angle
v =
Discussion
Spectacle lenses should be properly centered if we want to maintain point to point imaging. Proper
centration means that spectacle lens’ optical axis will goes through real eye’s rotation center. We can
center lens with respect to so called perpendicular view or we can calculate vertical decentration. For
the calculation technique is important vertex distance. Usually 1 degree of pantoscopic angle means
0.5 mm downward in vertical decentration.
Conclusion, notes, comments
What is the value of pantoscopic angle in your case/example?
What is the approximate value of vertical decentration if the pantoscopic value is 10 degrees? Is
there any general rule about the size of vertical decentration?
11
5 Spectacle frame wrap angle measurement
Introduction
Wrap angle of the frame has influence on quality of imaging. Picture 5.1. show us wrap angle of the
frame. We can see that optical axis is not equal with fixation axis. Individual spectacle lenses enable
to compensate astigmatism which is generated by wrap angle of the frame. There is theoretical
possibility to decentre spectacle lens’ optical center into the temporal side to maintain proper
imaging conditions. If we do this peripheral decentration we increase prismatic effect in horizontal
direction. In practice manufacturer can apply negative astigmatism power which eliminate
astigmatism caused by wrap angle of the spectacle frame (Najman 2010).
Picture 5.1: Wrap angle in spectacle frame (green arrow = axis of the spectacle lens, red arrow =
fixation axis) (inspired by Eyesite 2013)
Goals
• Measure wrap angle of the spectacle frame (𝜸)
• Calculate theoretical decentration of the spectacle lens
Equipment
Spectacle frame, handy rule or PD meter, writing staff, calculator, centration template
Methods
Measure wrap angle of the spectacle frame (𝜸)
With help of angle meter or centration template measure wrap angle 𝜸 according picture 5.2.
12
Picture 5.2: Measuring of the spectacle wrap (inspired by Pals-n-all 2013)
Calculate theoretical decentration of the spectacle lens
If we want to calculate temporal decentration of the wrapped frame we need to measure vertex
distance. This task we can do with handy rule for example. If we know wrap angle and vertex
distance we can calculate temporal decentration of the spectacle lens.
ℎ 𝑇 = 𝑑 + 13 ∗ 𝑡𝑔
γ
𝟐
[mm], [°] (19)
Results
Measure wrap angle of the spectacle frame (𝜸)
Schematically draw shape and wrap angle of the spectacle frame into the protocol. Describe size of
the wrapping.
𝜸 =
Calculate theoretical decentration of the spectacle lens
hT =
Discussion
So called spectacle frame’s wrap angle is important parameter for manufacturing of the individual
spectacle lens. These lenses are manufactured exactly according parameters of the customer’s
frame. It is also important in spectacles for sport to adapt spectacle’s lens optical center.
Conclusion, notes, comments
Why we use in calculation formula only half of the wrap angle?
Which methods you can use for measurement of the wrap angle?
13
6 Spectacle frame pressure relation
measurement
Introduction
Places where is contact between spectacle frame and skin are called “critical places”. Spectacle
frame material negatively influences tissue metabolism. Secondary spectacle lens material is
influenced by tissue emission substances. Main goal for the optometrist is to choose that
combination of spectacle frame material and individual skin type which will be minimally destructive
for each other. Empirical data show that accepted skin local stress should be 0.6 till 1 N/cm2
. The
weight of the spectacle is divided into nasal part (90 % of total spectacle weight) and into spectacle
side part (10 % of total spectacle weight). Picture 6.1 shows ideal values of pressure relation (PR) and
of pressure (PN) according to Fischbach (Rutrle, 2001).
Picture 6.1.: Ideal pressure relation values according to Fischbach (inspired by Rutrle, 2001).
Goals
• Calculate pressure relation for selected spectacle frame used for 60 years old patient
• Calculate pressure relation for selected spectacle frame used for your age
Equipment
Spectacle frame, digital kitchen scale, writing equipment, angle meter.
Methods
Calculate pressure relation for selected spectacle frame used for 60 years old patient
For pressure relation calculation we have to measure and calculate some other spectacle
parameters. Firstly, measure angle 𝛼 (see picture 6.2) which is important for calculation of power FN
(see formula 20). With this power press nasal spectacle pads in nasal area. In case of spectacle frame
without spectacle lenses add weight 30 grams to weight of spectacle frame.
14
Picture 6.2: List of powers in nasal area (FG – gravity power, 𝛼 – angle between line of pad and
vertical level, FH – horizontal power, FN – normal power,FTH – horizontal friction power, FT – friction
power,FTN – normal friction power; inspired by Rutrle, 2001).
𝐹 𝑁 =
𝑚∗𝑔
2∗𝑠𝑖𝑛𝛼
m [g], 𝛼 [°], g [m.s-2
], FN [cN] (20)
Note: We use spectacle weight in grams, g means adapted gravity constant 0.981 m.s-2
and resulted
power FN is calculated in cN.
After that we can calculate normal pressure PN. For this calculation we need to know size of spectacle
pad area. For this measurement we can use millimeter paper (see picture 6.3)
Picture 6.3: Fischbach’s spectacle frame pad patterns (inspired by Rutrle, 2001).
15
Further we can according bellow listed formula (21) calculate normal pressure PN. If we use 0.981 for
value g and cm2
for spectacle pad area, we will get result in hectopascals (hPa).
𝑃 𝑁 =
𝐹 𝑁
𝑆
PN [hPa], S [cm-2
] (21)
If we have normal pressure PN value, we can calculate pressure relation (PR). PR means ration
between normal pressure and maximal pressure as a function of the age.
𝑇𝑅 =
𝑃 𝑁
1,25∗(100−𝑎𝑔𝑒)
PN [hPa], age [years] (22)
Calculate pressure relation for selected spectacle frame used for your age
We can use the same calculation for PR as in example above.
Results
Calculate pressure relation for selected spectacle frame used for 60 years old patient
PR60 =
Draw shape of the nasal part of the frame and mark the angle alfa and its size.
Calculate pressure relation for selected spectacle frame used for your age
PR =
Discussion
If we get PR lower than 0.6 it means that spectacles can be worn without restriction. If the PR is
lower than 1.0 spectacles can be used in case that patient’s skin is healthy. Spectacle sides should be
perfectly adapted. If the PR is higher than 1.0 spectacles should be used only for restricted time.
Conclusion, notes, comments
Which parameters of the spectacle frame should be adapted/changed for better PR?
16
7 Spectacle frame static relationship
measurement
Introduction
Spectacle frame should press with attached power to the head optimally. Side parts of the frame
generate significant power moment at the frame hinge. This power moment increases with length of
the spectacle side and initial power. This power works in opposite direction in comparison to
attached power of the spectacle side (Rutrle, 2001).
Goals
• Calculate power which is induced on melted hinge of the spectacle frame
• Calculate power which is induced on rivet hinge of the spectacle frame
Equipment
Spectacle frame, handy PD meter, writing equipment, calculator.
Methods
Calculate power which is induced on melted hinge of the spectacle frame
According to bellow listed picture (7.1) measure length of the spectacle side do the side curvature
and distance from the hinge to the edge point B (d1)
17
Picture 7.1: Power relationships in melt hinge (F – power, B – edge point, d – distance to the edge
point, A – place of power F affection; inspired by Rutrle, 2001).
For our calculation we will suppose that power F affecting with spectacle side curvature the skin
behind the ear has 1 N. Further we can calculate according to below listed formula value of the
power F1Z which affect the place of melted hinge.
𝐹1𝑍 =
𝐹∗𝑑
𝑑1
F1Z, F [N], d [mm] (23)
Calculate power which is induced on rivet hinge of the spectacle frame
With similar way calculate value of the power F1N. This power will affect the spectacle frame in place
of rivet hinge. For calculation use below listed formula.
𝐹1𝑁 =
𝐹∗𝑑
2∗𝑑1
F1N, F [N], d [mm] (24)
Results
Calculate power which is induced on melted hinge of the spectacle frame
F1Z =
Calculate power which is induced on rivet hinge of the spectacle frame
F1N =
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Discussion
Pressure of the spectacle sides on spectacle frame hinge is possible to decrease with choosing of
wider spectacle frame, widen of the spectacle sides or with increasing of spectacle sides curvature.
But on the other hand small pressure of the spectacle sides is recommended otherwise spectacle
should have bad stability.
Conclusion, notes, comments
Which power F1 is higher. In rivet hinge or in melted hinge?
19
8 Aniseikonia correction with spectacle
frame adaptation
Introduction
If the patient has aniseikonia we can reduce it with spectacle lens shift according to below listed
formula. So, called anisodistance spectacles is possible to use in case of monocular aphakia after
cataract surgery. Currently anisometropia, respectively aniseikonia after cataract surgery is
successfully solved by intraocular lenses.
Picture 8.1: Anisodistance glasses (Polasek, 1974).
𝛽 = 1 − ∆𝑑. 𝑆´ 𝐵 S´B [D], d [mm] (25)
In case we decrease vertex distance in convex lenses we decrease the size of the retinal image. In
case of concave lens is it opposite, i.e. decrease of vertex distance means increase of the size of the
retinal image. This principal we can use for example with contact lens correction (Rutrle, 1993).
Size of the aniseikonia can be measured by so called eikonometers. Almost all projection or LCD
optotypes contains so called hook test which can show size of the aniseikonia and further we can
calculate change of the spectacle lens position to minimize aniseikonia.
Goals
• Calculate sagittal position change of the spectacle lens in given magnification
• Calculate change of magnification by change from spectacle lens to contact lens
Equipment
Spectacle frame, writing equipment, handy millimeter ruler or PD meter, calculator.
20
Methods
Calculate sagittal position change of the spectacle lens in given magnification
Measure given spectacle lens. We need the increase of magnification by 3 %. How many millimeters
should we change and which direction to have aniseikonia spectacles?
Calculate change of magnification by change from spectacle lens to contact lens
Given spectacle lens we would like to change for contact lens. How much will change size of retinal
image with this correction?
Results
Calculate sagittal position change of the spectacle lens in given magnification
𝚫d =
Calculate change of magnification by change from spectacle lens to contact lens
𝛃 =
Discussion
We have to parameters which influence aniseikonia. One is own magnification of the spectacle lens
and second one is position of the spectacle lens in front of the eye. If we multiply these two
parameters we will get total magnification of the lens. This magnification we can use for elimination
of aniseikonia. If we have percentage value we have to count two parameters together.
Unfortunately for minimalization of the aniseikonia we have only lower potential, i.e. only 5-10 %.
Conclusion, notes, comments
Which type of eikonometers do you know?
What is the size of the aniseikonia by monocular aphakia corrected with spectacle lens?
What is the size of the aniseikonia by monocular aphakia corrected with contact lens?
21
9 Taxation of the prescription for spectacles
and optical aid
Introduction
Prescription for spectacle prescribe ophthalmologist in Czech Republic. This document contains
information nor only about corrective aid but also about patient and finally about the
ophthalmologist. If you get this document in optical store firstly you have to check if it contains all
important content. If not, ophthalmologist have to repair it. Below listed picture shows all important
contents of the spectacle prescription on its front side. On the back side we have to check if the
patient got this for the first time or repeatably and patient’s signature. Since 2019 in Czech Republic
will get spectacle prescription only children (below 14 years) or patient with special correction
(above 10 D, prism correction etc.)
Picture 9.1: Content of the spectacle prescription – front side (inspired by Benes et al., 2010).
Health insurance payment is given by the actual book emitted by General health insurance (VZP). For
correct payment there is need to know actual version of this book. It is recommended for every
optician and optometrist to have actual version of the book. You can download it from these
websites: www.vzp.cz, www.scoo.cz. Below we put sample of actual version of the book for spectacle
aid.
22
Picture 9.2: Book for payment from VZP actual from 2019 (Benes et al., 2010).
Goals
• In protocol according, the up listed sample draw and fill prescription for spectacles with all
content.
• Fill in prices for spectacles and lenses according up listed prescription.
Equipment
Actual price book of General health insurance (VZP), writing equipment, calculation.
Methods
In protocol according, the up listed sample draw and fill prescription for spectacles with all
content.
Draw and fill both sides of the prescription in protocol. Firstly, fill patients name and surname,
further ophthalmologist’s data. You can define type of refractive error. It is recommended to use
noncommon refractive values. Finally fill in if the patient will get payment for hard coat, tinting and
on the other side of the prescription fill in date of the last corrective aid.
23
Fill in prices for spectacles and lenses according up listed prescription.
Fill in values for optical aid according actual VZP book including its codes. Use the rule of the
cheapest payment.
Results
In protocol according, the up listed sample draw and fill prescription for spectacles with all
content.
Fill in prices for spectacles and lenses according up listed prescription.
24
Discussion
Prescriptions are sent by optical store to VZP and other private insurances once a month. If the
officer found that something is missing in the prescription it is send back to optical store. Expiration
date of the prescription is 3 months.
Conclusion, notes, comments
How often will get money for spectacle frame 2 years old children?
What is the payment for spectacle aid for adult with prescription: OD: sph -10.25D cyl -2.0D ax.
135deg. OS: sph -11.25D cyl -1.0D ax. 45deg.?
What optical aid should get adult with refraction error higher than 10 D?
25
10 Choice and recommendation of
spherical/cylindrical single vision lens
from the catalogue
Introduction
Proper choice of spectacle lens is very important task in practice of optician and optometrist. We
have to evaluate not only technical view but also economic and aesthetic parameters of the
spectacle correction. We have strict rules for centration of spherical and sphero-cylindrical lens. If we
have isometropic patient we have to respect real center of eye rotation, i.e. that optical axis of the
spectacle lens goes through real center of eye rotation. Correct centration is done if the optical
center of the spectacle lens is moved to point of optical centration. This point is created in place
where fixation axis crosses level of the spectacle frame if the frame is in perpendicular position in
comparison to the general level of the ground. In case of anisometropic correction and in near
correction with this so called “point imaging” is created vertical and horizontal prismatic effect which
can negatively influence patient’s fusion reserves. Mainly vertical fusion reserve and critical vertical
effect is very low.
Goals
• For given spectacle frame choose and center proper spherical or sphero-cylindrical lens from lens
catalogue.
• For given patient release and evaluate prescription for optical aid.
• For given patient and prescription create financial plan for spectacles.
Equipment
Actual book of VZP, catalogue of spectacle lens producer, writing equipment, calculator, PD meter.
Methods
For given spectacle frame choose and center proper spherical or sphere-cylindrical lens
from lens catalogue.
Your task is to choose proper spectacle frame for you colleague (student) from spectacle book and
proper spectacle lens. Correction could be for distance or near vision. In the protocol you should
note all measured parameters and data of selection including boxing system, PD of the patient,
height of the centration, vertex distance, name of the frame and lens, type of antireflection coating.
You should of course calculate and note decentration and chosen lens diameter.
For given patient release and evaluate prescription for optical aid.
You should draw general prescription form into the protocol and fill in all important notes in it.
Further you should financially evaluate the prescription.
26
For given patient and prescription create financial plan for spectacles.
In this task you should create financial evaluation of the prescription for patient, i.e. you will sum
price for the spectacle frame, spectacle lenses, for addition task as e.g. repair of the side, soldering
etc. is. From this sum you will subtract price for the prescription and define payment for advance and
payment of the rest of the issue.
Results
For given spectacle frame choose and center proper spherical or sphere-cylindrical lens
from lens catalogue.
For given patient release and evaluate prescription for optical aid.
For given patient and prescription create financial plan for spectacles.
27
Discussion
We have many types of spherical or sphere-cylindrical lenses on the market from different material.
There are many spectacle lens producers and distributors on Czech market. Offer of these producers
we can find in product catalogues. There is a need to orient yourselves in offer of the producers. You
should be able to choose proper product which will be adequate to client’s needs.
Conclusion, notes, comments
Which producers with spectacle lens offer is according to your opinion the best on the market and
why?
What criteria did you evaluate during the choose of the spectacle frame?
28
11 Choice and recommendation of bifocal
lens from the catalogue
Introduction
Bifocal lenses are still currently alternative solution to progressive lenses. Bifocal lenses have some
advantages which are preferred by some patients. Bifocal lenses have lower peripheral astigmatism
and distortion in comparison with progressive lenses. Main disadvantage of the bifocal lens is skip of
the image and aesthetic problem which is represented by visible connection between distance and
near part of the lens.
Goals
• For given spectacle frame choose and center proper bifocal lens from lens catalogue.
• For given patient release and evaluate prescription for optical aid.
• For given patient and prescription create financial plan for spectacles.
Equipment
Actual book of VZP, catalogue of spectacle lens producer, writing equipment, calculator, PD meter.
Methods
For given spectacle frame choose and center proper bifocal lens from lens catalogue.
Your task is to choose proper spectacle frame for you colleague (student) from spectacle book and
proper spectacle lens. Correction could be for bifocal lenses. In the protocol you should note all
measured parameters and data of selection including boxing system, PD of the patient, height of the
centration, vertex distance, name of the frame and lens, type of antireflection coating. You should of
course calculate and note decentration and chosen lens diameter.
For given patient release and evaluate prescription for optical aid.
You should draw general prescription form into the protocol and fill in all important notes in it.
Further you should financially evaluate the prescription.
For given patient and prescription create financial plan for spectacles.
In this task you should create financial evaluation of the prescription for patient, i.e. you will sum
price for the spectacle frame, spectacle lenses, for addition task as e.g. repair of the side, soldering
etc. is. From this sum you will subtract price for the prescription and define payment for advance and
payment of the rest of the issue.
29
Results
For given spectacle frame choose and center proper bifocal lens from lens catalogue.
For given patient release and evaluate prescription for optical aid.
For given patient and prescription create financial plan for spectacles.
30
Discussion
In ideal example addition of the bifocal lens should be lower than accommodation amplitude. In this
case patient is able to cover with accommodation interval all distance and there is no blurry part of
visual field. On opposite case (addition is higher than accommodation amplitude) patient will see
blurry parts of visual field. This problem is successfully solved by progressive lenses. But progressive
lenses contain progressive corridor with peripheral blurry parts and distortion which patient have to
adapt on it.
Conclusion, notes, comments
Which types of bifocal lenses do you know – according to material and technology of manufacturing?
Which types of near segments for bifocal lenses do you know?
Who is inventor of the bifocal lenses?
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12 Choice and recommendation of
progressive and degressive lens from the
catalogue
Introduction
Conception of the progressive lenses is known since beginning of the 19th
century. First progressive
spectacle lens was produced thanks to professor Maitenaze from France in the fifties of 20th
century.
It was the lens with aspherical and side symmetric design. Type of progressive corridor was the same
for right and left eye. Next years there were new types of progressive spectacle lenses. Currently
many global manufactures are able to produce progressive lens with the so called Free-From
technology. Thanks to this technology we can reduce peripheral astigmatism and distortion and if it is
needed we can reduce high order aberration. Degressive lenses are special progressive lenses
adapted for middle and near distance.
Goals
• For given spectacle frame choose and center proper progressive or degressive lens from lens
catalogue.
• For given patient release and evaluate prescription for optical aid.
• For given patient and prescription create financial plan for spectacles.
Equipment
Actual book of VZP, catalogue of spectacle lens producer, writing equipment, calculator, PD meter.
Methods
For given spectacle frame choose and center proper progressive or degressive lens from
lens catalogue.
Your task is to choose proper spectacle frame for you colleague (student) from spectacle book and
proper spectacle lens. Correction could be for progressive or degressive lens. In the protocol you
should note all measured parameters and data of selection including boxing system, PD of the
patient, height of the centration, vertex distance, name of the frame and lens, type of antireflection
coating. You should of course calculate and note decentration and chosen lens diameter.
For given patient release and evaluate prescription for optical aid.
You should draw general prescription form into the protocol and fill in all important notes in it.
Further you should financially evaluate the prescription.
32
For given patient and prescription create financial plan for spectacles.
In this task you should create financial evaluation of the prescription for patient, i.e. you will sum
price for the spectacle frame, spectacle lenses, for addition task as e.g. repair of the side, soldering
etc. is. From this sum you will subtract price for the prescription and define payment for advance and
payment of the rest of the issue.
Results
For given spectacle frame choose and center proper progressive or degressive lens from
lens catalogue.
For given patient release and evaluate prescription for optical aid.
For given patient and prescription create financial plan for spectacles.
33
Discussion
Standard progressive lens is centered according to printed marks. For general centration we need the
frame with standard pantoscopic angle and enough size of frame. Currently we can choose 3 basic
types of progressive canal length. The shortest progressive canal is 16 mm length, but this canal
usually produces highest peripheral astigmatism and distortion.
Conclusion, notes, comments
Is it possible to center progressive lens without printed marks? How?
We have to types of centration and ordering of degressive lens? Which types?
34
13 Choice and recommendation of lenticular
lens from the catalogue
Introduction
Lenticular lenses are special spectacle lenses for high ametropia correction. They were used in times
when we have no high index lenses. Currently lenticular lenses are replaced by high index lenses.
Lenticular lenses are produces from glass or plastic. Optical and none optical zone can be polished or
unpolished. The main disadvantage of the lenticular lens is reduction of the patient’s visual field and
aesthetic conception.
Picture 13.1: Convex lenticular lens (Benes et al., 2010).
Goals
• For given spectacle frame choose and center proper lenticular lens from lens catalogue.
• For given patient release and evaluate prescription for optical aid.
• For given patient and prescription create financial plan for spectacles.
Equipment
Actual book of VZP, catalogue of spectacle lens producer, writing equipment, calculator, PD meter.
35
Methods
For given spectacle frame choose and center proper lenticular lens from lens catalogue.
Your task is to choose proper spectacle frame for you colleague (student) from spectacle book and
proper spectacle lens. Correction could be for lenticular lens. In the protocol you should note all
measured parameters and data of selection including boxing system, PD of the patient, height of the
centration, vertex distance, name of the frame and lens, type of antireflection coating. You should of
course calculate and note decentration and chosen lens diameter.
For given patient release and evaluate prescription for optical aid.
You should draw general prescription form into the protocol and fill in all important notes in it.
Further you should financially evaluate the prescription.
For given patient and prescription create financial plan for spectacles.
In this task you should create financial evaluation of the prescription for patient, i.e. you will sum
price for the spectacle frame, spectacle lenses, for addition task as e.g. repair of the side, soldering
etc. is. From this sum you will subtract price for the prescription and define payment for advance and
payment of the rest of the issue.
Results
For given spectacle frame choose and center proper lenticular lens from lens catalogue.
For given patient release and evaluate prescription for optical aid.
For given patient and prescription create financial plan for spectacles.
36
Discussion
If you will grind the shape of the lens with automatic grinding machine you should be careful not to
lose the lens holder. Patient should get advice about the reduction of the lenses’ visual field.
Spherical lenticular lens should be centered on pupil with natural head position. If we center aspheric
lenticular lens we have to prefer put the lens cent on pupil in so called perpendicular view.
Conclusion, notes, comments
Which types of lenticular lenses you know – material and type?
How does differ the price of lenticular and high index lens for the myopia -11 diopters?
37
14 Choice and recommendation of prismatic
lens from the catalogue
Introduction
Prism lenses are used for correction strabismus and heterophoria. Prism lenses move the optical ray
to base of the prismatic lens, which is thickest part of the lens. Prismatic correction can be realized
by two ways. Firstly, we can decenter spherical or sphere-cylindrical lens during the centering and
grinding. More exact method is ordering the prismatic effect on given lens which is produced by
usage of special grinding ring or tilting of the grinding arm.
Picture 14.1: Manufacturing of prismatic lens (R – center of the curvature, o – optical axis; inspired by
Rutrle, 1993).
Goals
• For given spectacle frame choose and center proper prismatic lens from lens catalogue.
• For given patient release and evaluate prescription for optical aid.
• For given patient and prescription create financial plan for spectacles.
Equipment
Actual book of VZP, catalogue of spectacle lens producer, writing equipment, calculator, PD meter.
Methods
For given spectacle frame choose and center proper prismatic lens from lens catalogue.
Your task is to choose proper spectacle frame for you colleague (student) from spectacle book and
proper spectacle lens. Correction could be for prismatic lens. In the protocol you should note all
measured parameters and data of selection including boxing system, PD of the patient, height of the
centration, vertex distance, name of the frame and lens, type of antireflection coating. You should of
course calculate and note decentration and chosen lens diameter.
38
For given patient release and evaluate prescription for optical aid.
You should draw general prescription form into the protocol and fill in all important notes in it.
Further you should financially evaluate the prescription.
For given patient and prescription create financial plan for spectacles.
In this task you should create financial evaluation of the prescription for patient, i.e. you will sum
price for the spectacle frame, spectacle lenses, for addition task as e.g. repair of the side, soldering
etc. is. From this sum you will subtract price for the prescription and define payment for advance and
payment of the rest of the issue.
Results
For given spectacle frame choose and center proper prismatic lens from lens catalogue.
For given patient release and evaluate prescription for optical aid.
For given patient and prescription create financial plan for spectacles.
39
Discussion
In case of decentration of spherical or sphere-cylindrical lens for inducing of prism effect we are not
able to maintain condition for point imaging. High prism effect we can only induce with strong power
lens. High decentration cause different peripheral thickness of the lens which is not aesthetic.
Manufactured prismatic lens should be shifted by 0.25 mm per 1 pD against the base of the lens
because of maintaining of point imaging.
Conclusion, notes, comments
We have two types of decentration for prismatic lens. Explain the principal.
Why we do the decentration of the main point of prismatic lens in direction against the base of the
lens (0.25 mm per 1 pD)?
40
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41
Spectacle technique II
Practical exercises
Mgr. Petr Veselý, DiS., Ph.D.
Department of Optometry and Orthoptics,
Faculty of Medicine, Masaryk University
Created in collaboration with Service Center for E-Learning at MU,
Faculty of Informatics, Masaryk University, Brno 2021
Published by Masaryk University Press, Žerotínovo nám. 617/9, 601 77 Brno, Czech Republic
1., electronic edition, 2021
ISBN 978-80-210-9852-7