Abstract
Purpose :
Therapeutic strategies in photoreceptor dysfunction rely on the assumption that postreceptoral cone-opponent and luminance mechanisms are intact. However, it has not been well documented yet how cellular organization and synaptic connections develop after birth with deviant cone inputs. Studying congenital color vision deficiency (CCVD) may provide important information regarding this.
Methods :
Healthy volunteers (n=10) and subjects with CCVD (n=8) were tested including best corrected visual acuity (BCVA), microperimetry (MP) and optical coherence tomography (OCT). Type of color defect was determined using Nagel anomaloscope and the Cambridge Color Test (CCT). Ganzfeld electroretinography (ERG) elicited by heterochromatically modulated (HFM) stimuli was recorded to red and green lights modulating in counterphase at 12 and 36 Hz, while the fraction of red modulation was varied.
Results :
Controls (mean age 28.5±5,4 ys, range 24 to 43 ys) and CCVD subjects (mean age 28.3±8,6 ys, range 18 to 46 ys) showed comparable BCVA (-0.1±0,09 and CCVD and -0.075±0,1 logMAR) and MP thresholds (30.4±0,9 dB and 29.7±0,9 dB). OCT images showed normal retinal structure. CCT thresholds (in u’v’*10-4) for controls were normal (protan=43.3±9, deutan=42.3±6, tritan=70.1±21). Tritan thresholds were normal (64.1± 12) in all subjects independent from red-green color deficiency. CCT thresholds for protanopes and deuteranopes were beyond the gamut of the monitor the protan and deutan axes respectively. In the other six patients, protan and deutan thresholds were elevated (219,16±88, range 45 to 343; and 41±96, range 46 to 387). HFM ERG amplitudes and phases were relatively constant at 12 Hz first harmonic and the second harmonic displayed a minimum around R/(R+G) = 0.3 in controls. The 36 Hz conditions showed the V-shaped amplitude responses and phase shift. Dichromats showed substantial changes at both 12 and 36 Hz responses: minimum amplitudes were shifted to far right (protanope) or to the left (deuteranope). Anomalous trichromats displayed moderate changes with a response profile closer to controls.
Conclusions :
These results support previous findings showing the possibility of determining type and severity of CCVD objectively using HFM flicker ERG. Moreover, the data point to a level of cone-opponency in anomalous trichromats that needs to be further investigated by comparing function and genetics.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.