When patients get their prescription from their doctors, they go to their local pharmacy and get the medication. When patients are finished with their eye exams, they give their spectacle prescription to their optometrist or optician and the lenses get put into the frame of choice. Simple, right? But have you ever thought about what goes into the process? As it turns out, it is fairly complicated. Here are some of the things that we do at Dr. Mei-Ling Chan Optometry because designer frames may look great but they won’t improve your vision.
1) Check the pupillary distance so that the optical centre of the lens is lined up with the centre of your pupil.
2) For a progressive lens, an aspheric lens, or a single vision lens with a high prescription (or in a large frame), where the pupils sit from the bottom of the frame (the height) is also critical for clear vision.
3) What the patient needs the glasses for – driving, working on computers, running, or an everyday pair for everything? This will dictate whether we go with a single vision lens, a progressive lens, a modified progressive, polarized lenses, etc.
4) Is there a large face form in the frame? If there is, such as in the case of a pair of wrap around sunglasses, we need to select the appropriate base curve for the prescription lenses so that the lenses do not ‘bulge’ out from the frame and subsequently fall out. The appropriate lens design, such as the Shamir Attitude, would also need to be selected to ensure the vision does not become negatively affected by the extreme curve of the frame.
5) If the patient has certain facial features such as a prominent nose that moves the spectacle lenses further away from the eyes, we have to specify the increased vertex distance (distance from the cornea or front of the eyes to the lens) when ordering the lenses so that the patient does not experience increased peripheral distortion with his progressive lenses.
6) If a frame has an unusual pantascopic tilt, we need to measure that and take that into account when ordering the lenses.
7) What scratch and anti-reflection coatings should be used? Have you had glasses that you needed to bring back to the optical stores because the coating has ‘crazed’. Coatings that are substrate matched to the index of the lens (such as those offered by HOYA) increases the durability of the coatings and minimize this. You want an oleophobic coating that confers smudge resistance so that the lenses are easier to clean. Patients sometimes ask whether they can get their lenses made in glass because it is more scratch resistant than plastics. But did you know some coatings (such as the RECHARGE EX3 by HOYA) have better scratch resistance than glass! And you don’t have to put up with the heaviness of glass lenses. In addition, it reduces the high energy blue light (prominent in tablets and smart phones) from reaching the eyes. HOYA’s Super Hi vision EX3 offers extreme reflection protection and 2 years unlimited warranty. Now that is hard to beat.
Come see us at our Barrie office and ask us all about what goes into making your next pair of lenses!