As the Wilmer Eye Institute, Johns Hopkins Medicine celebrates its centennial in 2025, it seems an appropriate time to reflect on the career and accomplishments of one of its most distinguished alumni and faculty members.
David L. Guyton, M.D. completed his ophthalmology residency at Wilmer in 1976 and returned to Wilmer as chief resident in 1977.
The following year, he was appointed Director of Pediatric Ophthalmology and Adult Strabismus — a position he held until 2011. Since 1991, he has held the Zanvyl Krieger Professorship in Ophthalmology.
Guyton established the Laboratory of Ophthalmic Instrument Development in 1978, out of his interest in inventing and his obsession with optics. To this day, the lab is dedicated to creating and building ophthalmic instruments.
He was joined in the lab by Kurt Simons, Ph.D. in 1984 (through 2019), by David Hunter, M.D., Ph.D. in 1992 (through 2002), by Kristi Irsch, Ph.D. in 2010, and since 2000 by Boris I. Gramatikov, Ph.D., who continues to play a key role in the electronics, computer programming, and analytical development of ophthalmic instruments.
Guyton’s accomplishments include more than 330 publications and 19 U.S. patents. Among his most notable achievements are four groundbreaking devices: the Spherocylindrical Subjective Refractor, the Potential Acuity Meter, the Remote Haploscope, and the Pediatric Vision Screener.
Guyton's Four Groundbreaking Devices
Spherocylindrical Subjective Refractor (1978)
The Spherocylindrical Subjective Refractor was developed to measure eyeglass prescriptions. The patient would turn a knob to focus a series of targets, and the device would automatically determine and print out the correct prescription. This innovation was commercially available as the American Optical SR-IV Programmed Subjective Refractor for about 10 years, with 400–500 units sold at $18,000 each. It was the first automated subjective refracting instrument, serving as a precursor to the infrared automatic machines available today for clinical refractions.
Potential Acuity Meter (1980)
The Potential Acuity Meter (the “PAM”) helps predict the vision a patient would have after cataract surgery. Before modern surgical techniques, cataract surgery was riskier, so it was vital to know if the patient would benefit enough to justify the procedure. The device works by projecting an eye chart through a tiny hole in the cataract, allowing the examiner to find a spot where the patient can see the chart. This gives a good estimate of the vision improvement to expect after surgery. The Potential Acuity Meter was commercialized by Mentor O&O Inc., with about 4,000 units sold, and is still fondly remembered by many ophthalmologists. However, it is less commonly used today because faster methods are now available.
Remote Haploscope (1986)
The Remote Haploscope was a room-sized device developed to automatically measure misaligned eyes (strabismus) and perform an automated version of the Lancaster red-green test. The device allowed patients to use a joystick to align a series of targets and took measurements automatically. One of its key innovations was the ability to project an image of the patient out into the room, allowing exams to be performed on the image rather than directly on the patient — an advantage especially for young children who are often frightened by close-up instruments. While the Remote Haploscope was technically successful and provided valuable learning, it was too large and complex to be commercially viable. However, the experience gained from developing it contributed to advances in automated eye measurement and pediatric ophthalmology.
Pediatric Vision Screener (2002)
The Pediatric Vision Screener screens young children for strabismus and amblyopia. The device detects even small degrees of eye misalignment, which are often associated with decreased vision in children. It was designed to be effective for children as young as one year old, using engaging targets like a blinking light paired with a laughing sound to attract the child’s attention and quickly assess eye alignment. The screener was commercialized in 2018 by Hunter’s startup company, Rebion, but it is not widely used. Guyton and Gramatikov have continued to work on improving the device, and it remains an important project for their lab. Although the current commercial version is not as successful as hoped, the device is still notable for its innovative approach to early vision screening in children.
