The Effects of Aging Eyes (Presbyopia) on Vision and Maintenance Cost of Loupes

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ErgoPractice News – March 2022
By Jin Chang PhD


The working distance of loupes will be increased as a function of the eye because the near focal distance of aging eyes will increase due to the reduced accommodation power of the eyes and the increased working distance will affect the vision through loupes. Therefore, the working distance of loupes should be restored either by updating the reading prescription (near vision ADD diopter power) with loupe optics (only manufacturers can do – loss of time and high cost. Backup loupes are needed during repair) or by adjusting working distance with SurgiTel’s interchangeable working distance caps (users can do – no loss of time and low cost). SurgiTel can offer significant cost benefits to users of loupes – this may allow users to save thousands of dollars.

Figure 1: Effect of Presbyopia. Source: Wikipedia

The Effect of Aging Eyes on Vision

The average population may start to notice that they feel difficulty in reading fine print from around the age of 40 due to the accommodation power of the eyes decreasing as a function of age.1 Figure 1 shows how presbyopia changes the focal length of the eye, Figure 2 shows the accommodation power of eyes as a function of age, Figure 3 shows an example of the eyeglass prescription, and Figure 4 shows typical near vision (NV) ADD diopter power (reading prescription) vs. age. The reading prescription will continue to increase from +0.25 diopter (about age 40) up to +2.5 diopter (about age 65) which helps aging eyes see objects at a close distance. After about age 65, the change of reading prescription will stop because the change of accommodation power will stop.

Since the near focal distance of aging eyes will continue to increase as a function of age after about age 40, the working distance of loupes will continue to increase. With the increased working distance, we can see fewer details through loupes.2 If the working distance is increased by 10%, we can see 10% fewer details of linear objects, 19% fewer details of 2D objects, and 27% fewer details of 3D objects. Since with increased working distance, we can see fewer details, our working distance with loupes should be restored regularly to see the same details after the presbyopia starts to affect your vision.

Figure 2: Duane’s classical curves showing the amplitude (diopter) or width of accommodation as changing with age. Mean (B) and approximate lower (A) and upper (C) standard deviations are shown. Source: Wikiwand

Figure 3: Example of Eyeglasses Prescription – ADD (or NV) is additive diopter power needed for older eyes to see close or near objects.

Figure 4: Typical NV ADD Power vs Age  Source: EyeQue

Restoration of Original Working Distance of Loupes

Today there are two methods that restore your working distance with loupes. The first method is updating your reading prescription inside the loupe optics. The second method is to use interchangeable working distance caps or working distance adjustment caps. Most manufacturers can only use the first method. On the other hand, SurgiTel can use either the first or second method because SurgiTel loupes are designed with the use of patented interchangeable working distance caps. The main difference between the two methods is that updating reading prescriptions with loupe optics should be done only by manufacturers. The typical time for updating a reading prescription (inside the ocular) is 2 to 5 weeks due to the time for shipping both ways and updating the reading prescription – loss of significant time and updating cost of reading prescription. If your backup pair of loupes need to have the reading prescription adjusted too, the maintenance will be doubled. In contrast, restoring the working distance of SurgiTel loupes can easily be done by users by replacing working distance caps – no loss of time and low cost of working distance caps.

Benefits of SurgiTel Loupes Designed With Working Distance Caps

  1. Creating different working distances with interchangeable working distance caps (patented): Users can increase or reduce the working distance of loupes for different cases to achieve the best working posture.
  2. Restoring the working distance that increased due to aging eyes (presbyopia) with interchangeable working distance caps: With SurgiTel loupes, you can save thousands of dollars for restoring the working distance of loupes increased due to aging eyes.
  3. Increasing the effective magnification power of loupes with interchangeable working distance caps: Eyes can see better by getting closer to objects because the image projected onto the retina becomes larger as the distance of the object decreases. Loupes just magnify the image projected onto the retina. If you decrease the working distance of SurgiTel prism loupes with interchangeable working distance caps, you can increase your visual acuity. If you decrease the working distance by 20%, you can see 20% better with line, 36% better with area, and about 50% better with 3D objects. SurgiTel prism loupes can be used as multi-vision loupes.

Why You Should Consider SurgiTel as Your Partner for Your Vision Aid Products:

The founding mission of SurgiTel has been providing clinicians with truly ergonomic, posture-safe loupes and eye-safe LED headlights. During the last 30 years, SurgiTel introduced many world-first vision aid products based on patented concepts, including customizable Front-Lens-Mounted (FLM) loupes, ergonomic frames, truly ergonomic Through-The-Lens (TTL) loupes, true-color LED beam-forming optics which allows SurgiTel to offer safer LED headlights with the best color accuracy, LED lights with no-touch switching, multi-vision loupes with interchangeable working distance caps, interchangeable custom nose pad systems, and loupe-mountable digital cameras (SurgiCam HD).


SurgiTel offers unique benefits which may not be available with other brands as follows:

  1. SurgiTel offers the most magnification options (2.5x to 10x).
  2. SurgiTel offers all magnification loupes with either FLM style or TTL style.
  3. SurgiTel offers the most LED light options (warm, neutral, and cool) with various models (wired, wireless, and no-touch switching).
  4. SurgiTel offers truly ergonomic loupes to all clinicians with various nose types which offer truly ergonomic benefits over deflection loupes.5
  5. SurgiTel offers a free evaluation service – posture analysis with your current loupes and potential blue light hazard with your current LED lights.

SurgiTel’s free evaluation service can help evaluate your working posture and avoid the potential blue light hazard of various cool brands of LED lights. Click here to schedule a free evaluation.


  1. Anderson, David Leech. The Science of Vision: An Introduction. The Mind Project, n.d. Content Copyright © 2003 The Mind Project. All Right Reserved.
  2. Chang, Jin. “Choosing Loupes for Dental School: Three Most Common Myths.” SurgiTel. SurgiTel, July 1, 2020.