The site for all things eye-related


Theodore Leng, MD, FACS

I’m an Associate Professor of Ophthalmology at the Stanford University School of Medicine, Director of Clinical and Translational Research and Director of Ophthalmic Diagnostics at the Byers Eye Institute at Stanford in Palo Alto, CA.

I am a board-certified ophthalmologist that specializes in vitreoretinal diseases and surgery, which means that I am a “retina specialist” and deal with many sight-threatening disorders such as macular degeneration and diabetes on a daily basis.

I started this blog to help inform others about vision and the things that can affect it. Occasionally, I write about other topics, but the main focus of this page is to help inform about eye care.  I draw from my daily experience as a busy clinician and educator and address the most common issues that arise.

Outside of my work as a physician, I am active in developing the intersection of medicine and mobile/social media and served as President of the Stanford Medicine Alumni Association.  I also enjoy mentoring medical and pre-medical students and volunteering as a Command Pilot with Angel Flight West to fly patients for medical care.

When I am not doing any of the above, I dream about flying airplanes.

12 comments on “About

  1. Peggy LaPlante
    August 29, 2015

    Hi Dr. Leng. I’m scheduled for surgery Monday mid-morning. Look forward to seeing you. Impressed with VisionMD. Thanks for making this available.
    p.s. It is refreshing to see you wearing stylish, practical sunglasses rather than aviator type. Have a great weekend!

  2. w flower
    March 21, 2016

    Hi, I find the lowest reading power 1.00 in pharmacy stores bit powerful for me. My actual range seems to be less than 1.00.
    My optometrist prescribed according to age (mine 49) at 1.75 and letters seem to jump up. So I got another 0TC type, bought lowest available= 1.00. This too seem a bit high a power glass for me.
    Is there 0.75 or 0.50 strength reading glasses?

    • visionmd
      March 21, 2016

      Not that I know of as the power is inversely proportional to the focal distance of the glasses. Thus, a 0.5D lens would have an optimal focal distance of 2 meters (~6 feet)! which is longer than most people’s arms.

    • Cyclemum
      March 27, 2019

      You won’t find an OTC reading spec of 0.50 or 0.75 but an optometrist could prescribe one. visionmd is correct that the focussing distance of 0.50D is 2m however as you will have some focussing “power” in your own natural lens, 0.50 or 0.75 may be all you need to “top up” your vision.

  3. Larry Hoffheimer
    June 15, 2016


    • visionmd
      June 15, 2016

      That’s a great question and the current answer is that we don’t know. There is data to support it, but it is not conclusive at this point. Stay tuned for more research results

  4. Larry Hoffheimer
    June 15, 2016

    The answer is “we do know”. The data collected by the NEI during the AREDS study show conclusively that zinc in the AREDS formula, will accelerate the progression in a minority (about 15%) of those with intermediate AMD. Please look at the web site It is a shame that a retina specialist with your distinguished credentials is saying “we don’t know”. You say to stay tuned for more research results. Tell me what research are you referring to. I know of no such research.

    Larry Hoffheimer
    Chairman and Founder of the Macular Degeneration Association

  5. visionmd
    June 15, 2016

    You are correct that there is some data that would indicate that Zinc MAY have a negative effect in patients with AMD. However, I would hesitate in saying that this data “conclusively” proves that Zinc is bad – it was only one study, which was not done prospectively and was a post hoc analysis. Moreover, it is a stretch to say that based on this one study, we should be screening patients to determine if Zinc may be bad for any specific patients.

    There are two points I will make about this that support my original statement that “we don’t know” and that the jury is still out on this:

    1) The American Academy of Ophthalmology’s official recommendation is that routine genetic testing should NOT be routinely performed on AMD patients. Ths was published in their journal, Ophthalmology, by a panel of leading experts who reviewed the available data.

    2) Dr. Emily Chew, the lead investigator at the NEI for the AREDS study has refuted the study that Zinc may cause worse vision in some patients with AMD.
    You can read her published response here:

    Thus, while I appreciate you reaching out to have a discourse about the role of Zinc in the management of AMD, I still stand behind my original statement and say that “we don’t know” yet whether Zinc is good or bad or neutral in AMD patients. More research is necessary as there is conflicting evidence for and against the use of Zinc.

  6. Larry Hoffheimer
    June 15, 2016

    Emily Chew and the NEI are conflicted on this subject. They are receiving millions of dollars both personally and the NEI. Bausch and Lomb is a co-owner of the patent with the principal NEI employee who put the test together. (I think you know that). The AAO is merely following the lead of the NEI for purely political reasons. People are, losing their vision because the these doctors are forgetting their “do no harm” mantra!

    I’d be happy to discuss further by phone if you wish.

  7. visionmd
    June 15, 2016

    There are conflicts on both sides. Dr. Carl Awh, the lead author of the paper you are likely basing your conclusions that Zinc is bad on, has equity ownership in a company that does genetic testing for AMD to determine if Zinc is bad for you.

    So there are conflicts on both sides. Thus, I personally remain at equipoise on this issue and am awaiting further data to make any definitive conclusions.

    Again, I really appreciate you having this discussion with me. It is good for others to see that science and clinical recommendations are not so straight forward. Warmest regards.

    • Larry hoffheimer
      June 7, 2020

      You are a class act. I truly respect your position. Carl Awh is indeed my source. He is an exceptionally well respected retina specialist. I am saddened that you suggest, by inference, that his conclusions regarding zinc’s potentially harmful effect is driven by monetary influence.

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