Longevity of visual improvements following transcorneal electrical stimulation and efficacy of retreatment in three individuals with retinitis pigmentosa

Abstract

Purpose: A small-scale randomized controlled trial conducted by our group found that four of seven retinitis pigmentosa (RP) subjects who received six weekly Transcorneal Electrical Stimulation (TES) sessions developed significant improvements in visual acuity (VA), quick contrast sensitivity function (qCSF), and/or Goldmann visual fields (GVF). We longitudinally monitored three of these participants for declining visual function due to natural RP progression to determine the duration of their responses and administered retreatments.

Methods: Over a period of 29-35 months, repeated ETDRS VA, qCSF and/or GVF tests and three to six TES treatment courses consisting of six weekly sessions were administered in each eye of three RP participants every four to 16 months in an unmasked, prospective case series study.

Results: For two participants, there were significant VA improvements of 44-52 letters (0.88-1.04 logMAR) and 15-23 letters (0.3-0.46 logMAR) in the worse eye at baseline after each of three or four treatment courses of TES compared to initial baseline. They had no significant decreases from baseline for VA or qCSF over 29 to 35 months, The third participant had a significant mean improvement in VA in the eye with better baseline vision (p = 0.004) and binocularly (p < 0.001) following six treatment courses over the 29-month period. For the first two participants, mean annual rates of GVF change for each eye ranged from -5% to 0% with the V4e stimulus, and -26% to +33% the III4e stimulus. The third participant's mean annual GVF changes were +14 to +35%, with a statistically significant improvement across 29 months for both the V4e and III4e stimuli in the right eye (p = 0.045; p = 0.015) and the V4e stimulus in the left eye (p = 0.047).

Conclusion: Following encouraging visual improvements after TES that lasted for several months, it appears it may be possible to restore and prevent slowly diminishing vision over time with retreatments, which requires confirmation in a large-scale randomized controlled trial.

Keywords: Contrast sensitivity; Goldmann visual field; Retinitis pigmentosa; Transcorneal electrical stimulation; Visual acuity.

Fig. 1

Panels 1a, 1b, and 1c show the change in ETDRS VA letters from baseline over time for subjects 1, 2, and 3, respectively (five letters = 1 line = 0.1 logMAR). Panels 1d, 1e, and 1f show the changes in the qCSF test results from baseline over time for subjects 1, 2, and 3, respectively. The asterisks along the x-axis indicate the assessment that occurred four to 7 weeks after completion of each TES treatment course of six weekly sessions. The bar along the top of each figure panel indicates the periods during which TES was administered (gray shaded areas) and when no TES was administered (white areas)

Fig. 2

Panels 2a, 2b, and 2c show the GVF log retinal areas over time for subjects 1, 2, and 3, respectively. The asterisks along the x-axis indicate the assessment that occurred four to 7 weeks after completion of each TES treatment course of six weekly sessions. The bar along the top of each figure panel indicates the periods during which TES was administered (gray shaded areas) and when no TES was administered (white areas)

Fig. 3

GVF maps of the plotted locations of vision in each eye of the three subjects at baseline (pre-TES)(shown in the left panels) and the last follow-up visit, 29–35 months post-TES (shown in the right panels). The V4e isopter is drawn with a black line and the III4e isopter is indicated by gray filled areas

Fig. 4

Fundus photos of the macula in each eye taken at baseline (pre-treatment) and the last follow-up assessment at 29 months for subjects 2 and 3, or 35 months for subject 1

Fig. 5

OCT images of the macula obtained in each eye (OD in left panel and OS in right panel) of subject #3 at 29 months post-TES