Dr. Quan & Associates, Optometrists

Our doctors provide you with the best care possible.

To provide you with the most precise and comfortable vision that your eyes deserve, proper Eye glasses dispensing and fitting are also an important part of the eye care process. Licensed professionals like optometrists, opticians, are trained to:


·         Assess your visual needs, counseling.

·         Make proper eyeglasses measurements

·         Adjust / fit the eyeglasses on the patient’s face.



1.       Visual needs: proper determination of your work conditions, distance of reading, occupation, visual demands, are needed in order to recommend you the right frame and type of lenses for your needs. 



2.       Eye glasses measurements: specific measurements are needed in order to dispense glasses. The measurements depend on your prescription, how high it is, presence of astigmatism, type of lenses (bifocals, progressives), type of frames (curvature of the frame, of the patient’s face)


·         PDs measurements: or pupil distance measurement is the distance between the pupils. It has to be measured by a Pupilometer, based on corneal reflex method, in order to be the most precise. It has to be a monocular measurement (one eye at a time, from the nose to each eye's pupil).


Why? Only a deviation or difference of 0.5 mm or 1mm can sometimes change your effective visual perception and comfort. It is especially more important on some prescription (medium to high RX, astigmatism, eye muscles deviation etc), and on some types of lenses (bifocals or progressives, aspheric lenses, high index lenses).


Monocular measurements are especially important on some RX or lenses. For example, if your total binocular PD is 70mm, but your right eye may be 33mm and left eye 37mm. A glasses made with total PD of 70mm compared, with a glasses made with 33mm right and 37mm left will feel different, and have different visual properties, especially on some types of RX or lenses.   


PDs measurement is NOT the only measurement needed for proper eye glasses dispensing. PDs measurements is NOT part of a standard regular eye exam, as PDs and other glasses measurements are ONLY taken at the time of dispensing by a licensed optician at an optical store, with your final chosen frame sitting on your face.

Also, proper prepared eyeglasses require other accurate measurements such as:



·         Vertex distance: is the distance between your eyes and the back of the eye glasses frame. It can only be measured with your frame on. It has to be measured with your physical eye glasses frame sitting on your face. It is needed for medium to strong prescription (more than 4 dioptre).


Why? If your frame sit closer or further than normally on your face than intended, the effective power that your eyes receive is different, and your prescription on the lenses need to be calculated and changed accordingly.


·         Bifocal heights or progressives height measurements: is the measurement of the position of the bifocal or the progressive lenses. It has to measured with your frame on your face, as that measurement will varies with the size of the frame, how the frame sit on your face etc. A small deviation of 1mm in the position of the progressive height can cause visual discomfort and can change your effective vision.


·         Single vision lenses height: (optical center) is the measurement of the center of the pupil to the bottom of the frame. It can only be measured with your frame on your face. It is especially important and needed for: medium to high prescription, presence of astigmatism, aspheric lenses, and high index lenses and other eye conditions. A wrong optical center can induce prism effects and eye strain.


·         Base curve: is the curvature of the lenses. The base curve sometimes has to be specified and changed depending on the patient’ RX, frame or the shape of the patient’s face. A wrong curvature can induce or create more peripheral astigmatism, and can change your perception, magnification and comfort.


To provide you with the most precise vision and comfort that your eyes deserve, these measurements and other measurements have to be done by trained licensed professional such as optometrists, or opticians working in optical stores.


Contrarily to some beliefs, your chosen eye glasses frames have to be ON your face, in order to make these measurements with precision.





3.       Adjustment, fitting of glasses: your final eye glasses need to be properly adjusted in order for them to sit properly as intended, and to provide you with comfortable wear.



 Visual or systemic symptoms, such as blur, eyestrain, diplopia, or headache, can develop if the spectacle parameters are inaccurate or proper dispensing procedures are not followed.




Optometry standard of practice:  "The measurement of a patient's pupillary distance (PD), fitting height for multifocals, selection and fitting of an appropriate frame, selection of an appropriate lens material and selection of an appropriate lens coating are considered part of the eyeglass dispensing service and not part of a regular eye examination."







You can bring the prescription that our doctors give you to a local Alberta licensed optical store to get your eye glasses made.


The Alberta licensed optical store where you are getting the glasses will be able to counsel you, make proper eye glasses measurements, and adjustments.

Our  doctors cannot help you with PDs or any other eyeglasses measurements, or help you order eyeglasses online, as it is the legal and professional responsibility of the optical store to provide these services to you.


It is also recommended that you wear and try the eye glasses frames on your face, in order for the Optical to dispense and make proper accurate measurements.



Thank you.




Optometry FAQ
Dilation test
Visual fields test
Common Eye conditions and eye diseases
Office Policies and Fees
Privacy Policy
Book Appointments Online, All locations:Edmonton, Calgary, Red deer, Okotoks, Sherwood park, St albert