Contrast sensitivity device exposes vision limitations of reattachment patients

By Lynda Charters; Reviewed by John B. Miller, MD

Despite achieving a good letter visual acuity, patients with macula-off rhegmatogenous retinal detachments can be frustrated with their vision following reattachment surgery.

This scenario also is frustrating for physicians and it begs the questions regarding how this visual dysfunction can be better assessed and what functional measures can be used to demonstrate significant improvement with new therapeutics? A new device under development might answer these questions.

“While we are all familiar with letter visual acuity, it doesn’t always tell the full story about a patient’s quality of vision,” John Miller, MD, said. “Surgeons can obtain anatomic success and visual acuity success after reattachment of retinal detachments, but patients remain frustrated with their vision.”

A new platform, the Sentio Platform (Adaptive Sensory Technology), might provide physicians better insights into what patients are experiencing. The device uses a testing algorithm that determines the contrast sensitivity after a retinal detachment has been repaired.

This platform, in the form of a handheld tablet described as a novel contrast sensitivity testing device, was evaluated for its ability to perform quick contrast sensitivity function testing of patients in relation to their visual activities.

Improving on old technologies

“The idea of contrast function is not new, as with the familiar Pelli-Robson contrast testing,” said Dr. Miller, assistant professor of ophthalmology, Harvard Medical School; director of retinal imaging, Massachusetts Eye and Ear, Boston.

The disadvantage of Pelli-Robson contrast testing is that the measurement is done at a single spatial frequency that determines the most-faint letter that can be seen at one type size. Similarly, with traditional Snellen or Sloan letter acuity, clinicians are measuring at one high-contrast frequency as the optotypes get progressively smaller.

With the new device, clinicians can measure multiple spatial frequencies in multiple contrast frequencies and obtain “the world of vision,” i.e., the area under the curve, that the patient can see.

“This technology offers new ways to detect the changes in visual recovery after retinal reattachment.” Dr. Miller said. “The initially large optotypes that are presented to the patient become progressively faint until they are barely visible, which is analogous to Pelli-Robson contrast testing.”

Tested in a pilot study

In a collaboration with colleagues at the Kellogg Eye Center, University of Michigan, Ann Arbor, Dr. Miller’s research team tested the computerized contrast testing device in a pilot study of retinal detachment. Fifteen patients were included and underwent testing of their contrast sensitivity function during their postoperative recovery.

Patients with significant cataract or a history of multiple retinal detachment repairs were excluded. The testing, which offers the use of filtered Sloan letters with 128 possible contrast and 19 possible spatial frequencies, was performed at an average 6 months after the reattachment surgeries, Dr. Miller pointed out.

“In this prospective, observational multicenter case series study, we found a 2 standard deviation difference in the contrast function after retinal attachment compared with age-matched controls,” Dr. Miller explained. “More importantly, this testing device, compared with Pelli-Robson contrast testing, showed that at different spatial frequencies there were relatively large differences. This device allows us to measure at the different spatial frequencies and pick up stronger signals at the intermediate frequencies that had not been detectable with previous technology.”

While the investigators found a difference in the contrast function of 2 standard deviations of all the patients tested, 9 of the 15 patients had a best-corrected visual acuity (BCVA) at 20/30 or better. However, despite the good vision, these patients had a difference in contrast function of 1 standard deviation.

“In patients with good visual acuity, we still found statistically significant contrast function reductions,” Dr. Miller added. “This provides us with a greater clinical signal of functional vision for testing of new therapeutics when visual acuity may otherwise show minimal effects.

“This device provides an efficient, user friendly, smart algorithm to measure the contrast function curve that can be used with a variety of retinopathies,” Dr. Miller said. “Additional work must be performed to validate our findings but could represent a new endpoint for visual function.”

John B. Miller, MD

john_miller@meei.harvard.edu

This article was adapted from a presentation that Dr. Miller delivered at the 2017 American Society of Retina Specialists meeting. Dr. Miller has no financial interest in the Sentio Platform. The device has not been approved by the FDA.