scientific measurement protocols 1

Churawan Lal Sahu M Optom 1

Scientific Measurement ProtocolsChurawan Lal sahu

M Optom


Measurements

Single vision

Bifocals

Progressive lenses

Scientific Measurement Protocols


Single Vision

IPD

Centration




Effect of decentration


Bifocals IPD

Distance & Near

Segment insertion

Segment height




Near PD & Segment insertion


Segment height



Progressive lenses

Training

Communication and counselling

Convincing power

Designs knowledge



Progressive lenses

Possible causes of problems with PAL’s

Indications

Contraindications




Fields of view Direction of Gaze

Contraindications


Mobility / Head Movement


Contraindications


Contraindications

Anisometropia High Cylinders Prisms High ADD



Contraindications

Bifocal users

Reading glasses users




Measurements step by steps


Step 1

Patients selection



Patients selection

Identification

Requirements

Expectations



Step 2

Frame selection




Frame shape

Good Shape

Bad Shape

Good Depth Good Size

Too Large

Frame sizeFrame depth

Small frame


Ideal frames Prefer metal frames

Adjustable nose pads

Min depth of 25-30 mm

Min fitting height should be 18mm / 14mm



Step 3

Frame Adjustment




Frame Adjustment

Vertex distance

Pantoscopic tilt

Facial wrap


Back vertex distance Shorter

Reduce BVD – wider fields of view




Effect of vertex distance


Pantoscopic tilt

10 to 12 degree

Pantoscopic tilt – increases near field of view




Effect of Pantoscopic tilt


Facial wrap – must not be too flat




Effect of facial wrap


Step 4

Interpupillary distance (IPD)



IPD

Monocular PD

Binocular PD

Scale or Pupillometer



IPD Use a corneal reflex for accuracy In case of strabismus – occlude one eye



Pupillometer centration



Effect of inexact IPD marking




Step 5

Monocular PD marking in the lens


Step 6

Fitting Height/ Vertical Height



Fitting Height Ensure that you are at eye level of patients Take monocular fitting height Measure directly to pupil centre Ensure that patient is looking strait ahead




Fitting height


Effect of wearer posture




Effect of parallax error Parallax error can significantly affect fitting

height


Effect of Fudging Fitting Height




Step7

Check the lens cut out



Delivery ..

Quality check up

Markings

Frame alignments

Power

Fitting cross heights & PDs



Delivery ..

On eye assessment

Frame fit Fitting crosses


Delivery


Delivery Instructions


Thank you

scientific measurement protocols 1

Health & Medicine