Evaluation of residual retinal function by pupillary constrictions and phosphenes using transcorneal electrical stimulation in patients with retinal degeneration.
BACKGROUND
To evaluate inner-retinal function by pupillary constrictions and phosphenes evoked by transcorneal electrical stimulation (TES) in patients with hereditary retinal degeneration.


METHODS
Consecutive 20 eyes of 20 patients (16 with retinitis pigmentosa (RP); and four with cone-rod dystrophy (CRD)) whose visual acuity was equal to or worse than 20/2000 at Osaka University Hospital and eight eyes of eight healthy subjects were enrolled. TES was performed on with a contact lens stimulating electrode. The electrically evoked pupillary response (EEPR) was recorded by a pupillometer, and the phosphenes by the subjective responses. Three electrical current thresholds were determined: T1, threshold current for initial phosphene; T2, threshold for eliciting a phosphene extending into the central field; and P, threshold for a relative pupillary constriction > or = 3%. The EEPR and phosphene thresholds were compared with the visual acuity or the visual field.


RESULTS
All T1, T2 and P were significantly higher in patients than in normals (Mann-Whitney, P<0.001). Both T1 and T2 were not correlated with visual acuity but depended on the area and location of the residual visual field. T1 and T2 in RP eyes with a EEPR was significantly lower than that in RP eyes without an EEPR. During TES, all subjects and patients had no pain, and no complications except for a slight corneal superficial punctuate keratopathy.


CONCLUSIONS
The safety and the efficacy of TES to estimate the residual inner-retinal function in patients with retinal degeneration indicate that TES can be used as one of the most important test to select candidates for retinal prostheses.
Morimoto
Takeshi
T
Department of Applied Visual Science, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Fukui
Takehiro
T
Matsushita
Kenji
K
Okawa
Yoshitaka
Y
Shimojyo
Hiroshi
H
Kusaka
Shunji
S
Tano
Yasuo
Y
Fujikado
Takashi
T
D000328:Adult; D000368:Aged; D002648:Child; D003315:Cornea / Q000502:physiology; D004558:Electric Stimulation / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010719:Phosphenes / Q000502:physiology*; D011680:Pupil / Q000502:physiology*; D012160:Retina / Q000503:physiopathology*; D012162:Retinal Degeneration / Q000235:genetics / Q000503:physiopathology*; D012165:Retinal Ganglion Cells / Q000502:physiology; D014792:Visual Acuity; D014794:Visual Fields