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Practical dispensing

This visual recognition task requires the practitioner to consider the dispensing scenarios and determine the correct interpretation and management in each case.

Image A

Image A

01 What is being measured here? 

a) Pantoscopic tilt of –6o
b) Pantoscopic tilt of +6o
c) Facial angle of 6o
d) Frontal angle of 6o 

02 On the basis of the above, aspheric lenses should be centred: 

a) 3mm below the horizontal centre line (HCL)
b) On pupil centre
c) 3mm below pupil centre
d) 3mm above pupil centre 

03 With regard to the measurement above, which statement is false? 

a) Conventional (not individualised) progressive lenses require an angle of close to 9o
b) Outside of the range of 7-12o conventional progressives are unlikely to give an acceptable reading area
c)  For single vision lenses the vertical centres should be moved 1mm down from pupil centre for every +2o
d) An angle of 0o requires optical centres to be on HCL

Image B

Image B

04 What measurement is shown in the image? 

a) Distance between rims (DBR) @15mm below crest
b) Distance between rims @10mm below crest
c) Distance between lenses (DBL)
d) Distance between pad centres 

05 Which statement is false for a hand made frame?

a) DBR @15mm is never smaller than DBR @10mm
b) DBL on a pilot shaped frame could be less than DBR @10mm
c) Box centre distance (BCD) should always be smaller than the centration distance
d) Bridge width is defined as the DBR 5mm below HCL 

06 Which statement is false for a hand made frame?

a) Crest height is the distance between a line intersecting the bearing surface of the nose and the lower limbus of each eye
b) The HCL is taken to be in line with the pupil centres
c) For distance spectacles the BCD should always be equal to or greater than the PD
d) Bridge width is the DBR 5mm below HCL

Image C

Image C

07 The frame above is dispensed to a nine-year-old-boy, Rx +6.00DS @12mm. Which statement is true?

a) The nasal edge of correctly centred 1.74 aspheric lenses would be as thin as the temporal edge
b) Placing OCs at boxed centres of this frame to achieve smallest diameter uncut would be within tolerance
c) It would be better to recommend a smaller frame with BCD closer to the required OCs
d) It is unethical to offer 1.74 aspheric lenses to a child as part of a selection of lenses at various prices 

08 What is the most accurate description of this frame?

a) Boys’ propionate frame with a comfort bridge
b) Gents’ SPX frame with adjustable pads on arms
c) Unisex cellulose acetate frame with regular bridge
d) Gents‘ Optyl frame with fixed pad bridge 

09 With regard to paediatric dispensing which statement is false? 

a) All stages including collection must be conducted by, or under the supervision of, a registrant who must be on the premises and able to intervene
b) An optical assistant can decide to post the glasses to the patient for convenience
c) A registrant can make a decision to post the glasses to the parent/patient under exceptional circumstances and if it is in the best interest of the patient
d) Repair and replacement of children’s glasses also requires registrant supervision

Image D

Image D

10 The image shows a BVD of 7mm, measured from cornea to front vertex, less 1mm to allow for dummy lens thickness. Which is false? 

a) With an Rx lens, thickness callipers can be used to find how much to subtract from the measurement
b) An Rx of +14.00DS @12mm would be ordered as +15.00DS @7mm
c) An Rx of +16.00DS @13mm would be ordered as +14.50DS @7mm
d) It is preferable to fit the the frame as close as possible rather than match the trial frame position 

11 With regard to this measurement, which is false? 

a) It is required on all prescriptions over 5.00D in the highest meridian
b) It is defined as the distance from the visual point of the lens to the corneal apex or the closed eyelid
c) It is measured using vertex callipers from the back vertex of the lens to the anaesthetised ocular surface
d) It may be determined using vertex callipers from the back surface of the lens to the closed eyelid 

12 For a spectacle Rx +16.00/-6.00 x 90 @12mm, what might be an appropriate contact lens Rx?

a) +14.75 / -5.50 x 90
b) +17.50 / -6.50 x 90
c) +19.75 / -8.50 x 90
d) +19.75 / -6.00 x 90

About the author

Peter Black is the dispensing standards manager for Boots Opticians, an ABDO practical examiner and immediate past president of ABDO.

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