Progressive lens measurement

PAL Fitting, facial measurement and markingGS Shrestha, B.OptM.OptomGS Shrestha, B.OptM.Optom

Gauri S. Shrestha, M.Optom, FIACLE


Fitting PALs is an art..

It requires adequate

training & skill

It involves

communication &

counselling skills and

convincing power


And a science..

It requires :

• A systematic approach

• Understanding of potential problems

• In-depth study of designs


What should be systematic approach..1) Identify the problem

--questing the presbyope

--remark the lenses

--check the frame fit

1.frame level 4.facial wrap

2.temple level 5.vertex distance

3.pantoscopic tilt


-- verify the lens fitting

-- observation of use

--confirm refraction and lens power

2) Possible signs and symptoms with PAL’s

3) Possible causes of problems with PAL’s

What should be systematic approach..


Whom to fit ?

ALL PRESBYOPES !

BUT..


Contraindications

Field of View


Contraindications

Direction of Gaze


Contraindications

Mobility / Head Movement


Prescriptions

Contraindications

• Anisometropia / Antimetropia• High Cylinders• Prisms


Patient selection Patient requiring vision for occasional intermediate distances and for those who request an invisible bifocal

Patients who resist convention bifocal or trifocals because of the “lines” are strongly motivated and are excellent candidates for PAL

Emerging presbyopes are also good candidates


Previous bifocal wearer who demonstrate need for a trifocal lens for occasional use may enjoy the flexibility of PALs

PALs should not be recommended for all presbyopes however discretion should be exercised, especially with the following patients

1) currently bifocal or trifocal wearer who are completely satisfied with their lenses

2) Patients with large oculomotor imbalances who require prism

Patient selection


3) patients who are accustomed to wearing and are satisfied with single vision lenses for near vision only

4) Patients with a significant amount of anisometropia(3D or >)

5) Patient who need adds of high power and who have large pupils

6) Patients who are nervous, tense, impatient, and generally intolerant of health-care devices

Patient selection


Fitting ...


Step 1

Identification of Patient’s

Requirements & Expectations


Useful tip

Judge the motivation

Highlight the advantages, but mention

the limitations as well


Step 2. Frame Selection

Frame shape

Good Shape

Bad Shape

Good Depth Good Size

Too LargeInsufficient Depth

Frame sizeFrame depth


Frame Selection

Back vertex distance

Pantoscopic tilt Facial wrap


Useful tip

Prefer metal frames with adjustable

nose pads


Step 3

Adjust before taking facial measurements

Adjust when delivering spectacles

Frame Adjustment


• When to Adjust Before taking the facial

measurements When delivering the

spectacles


Step 3

Back vertex Distance - shorter

Frame Adjustment

Reduced BVD giveswider field of view


Step 3

Pantoscopic Tilt - 10 to 12 degrees

Frame Adjustment

Increase Pantoscopic Tiltincreases near field of view


Step 3

Facial wrap - must not be too flat

Frame Adjustment


Step 4

Monocular PD


Step 4

Monocular PD

Monocular PDMonocular PDMonocular PDMonocular PD

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Step 5

Monocular PD


Step 6

Marking the lens insert


Step 7

Fitting height


Useful tip

Natural head posture

Sit at the same level as the patient

Check binocularly from a dist. of 1 meter

Use a fine marker


Step 8

Checking the cut out


Delivery ..

Markings

Distance power & prism

Addition

Fitting cross heights & PDs


Delivery ..

On eye assessment

Frame fit Fitting crosses


Delivery ..

On eye assessment

Distance Vision Near Vision


Delivery ..

Delivery Instructions


Useful tip

Use positive language

Remove the markings at the end

Maintain a record of the order forms


Useful tip

TAKE A BREAK !!!


3. Facial Measurements

•MethodsDistance method 1Distance method 2Near method 1 (the mirror method)

Near method 2


Facial Measurements

• Distance Method 1 Step 1: Adjust the frame Step 2: Measure the monocular

PDs with the pupillometer

Monocular Monocular PDPD


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Facial Measurements

• Distance Method 1Step 3: Mark the HCL & PD on the dummy lenses


Facial Measurements

• Distance Method 1 Step 4: Check the pupil height Step 5: Check the height while talking to the

patient


Facial Measurements

• Distance Method 1 Step 6: Order the PD as per the

pupillometer reading & height as per step 5


Facial Measurements

• Distance Method 2 Step 1: Adjust the

frame Step 2: Measure

the monocular PDs with the pupillometer


Facial Measurements

• Distance Method 2 Step 3: Place the frame on the patient and dot the

pupil centre Step 4: Check the height while taking to the patient

Dotting the pupil centre


3. Facial Measurements

• Distance Method 2 Step 5: Order the PD as per the pupillometer

reading & height as per step 4


Facial Measurements

• Near Method 1 Steps 1 - 5: as per Distance Method 1 Step 6: Mark the distance and near visual point

circles


Facial Measurements

• Near Method 1 Step 7: Place a mirror between the patient and

you and observe through the mirror the patient’s eyes when looking at the mirror

Step 8: Adjust the near visual circles if necessary to correspond with the patient’s lines of sight


Facial Measurements

• Near Method 1 Step 9: Place the adjusted near visual circles on

the layout chart to determine the final position of the fitting crosses.


Facial Measurements

• Near Method 2 Step 1: Adjust the frame Step 2: Measure the monocular near CDs with

the pupillometer



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Facial Measurements

• Near Method 2 Step 3: Mark the HCL & PD on the dummy lenses


Facial Measurements

• Near Method 2 Step 4: Check the pupil height Step 5: Check the height while talking to

the patient


Facial Measurements

• Near Method 2Step 6: Order the PD as per the pupillometer near PD

reading plus 2.5 mm each eye & height as per step 5


Facial Measurements

• Comparing the Methods Pre-marking the dummy lenses Vs dotting the lenses Pupillometer vs PD rule or dots


Lens Ordering

• PDs• Heights

From the horizontal centre line (Datum) From the frame bottom


Lens Ordering

• Checking the cut-out


Delivery1. Pre-delivery Verification

Checking the markings Checking the frame details Checking the distance power and prism


Re-locating ProgressiveLens Markings

1. Find micro-engraved permanent markings 2. Mark the position of the horizontal locators 3. Select manufacturer’s layout chart for the

correct lens type


Re-locating ProgressiveLens Markings

4. Lay the lens on the chart with the marked locators in the correct position

5. Trace the distance and near reference circles, the fitting cross and the prism reference point

Health & Medicine

Progressive lens measurement