Development of temporal response properties and contrast sensitivity of V1 and V2 neurons in macaque monkeys

The temporal contrast sensitivity of human infants is reduced compared to that of adults. It is not known which neural structures of our visual brain sets limits on the early maturation of temporal vision. In this study we investigated how individual neurons in the primary visual cortex (V1) and visual area 2 (V2) of infant monkeys respond to temporal modulation of spatially optimized grating stimuli and a range of stimulus contrasts. As early as 2 wk of age, V1 and V2 neurons exhibited band-pass temporal frequency tuning. However, the optimal temporal frequency and temporal resolution of V1 neurons were much lower in 2- and 4-wk-old infants than in 8-wk-old infants or adults. V2 neurons of 8-wk-old monkeys had significantly lower optimal temporal frequencies and resolutions than those of adults. Onset latency was longer in V1 at 2 and 4 wk of age and was slower in V2 even at 8 wk of age than in adults. Contrast threshold of V1 and V2 neurons was substantially higher in 2- and 4-wk-old infants but became adultlike by 8 wk of age. For the first 4 wk of life, responses to high-contrast stimuli saturated more readily in V2. The present results suggest that although the early development of temporal vision and contrast sensitivity may largely depend on the functional maturation of precortical structures, it is also likely to be limited by immaturities that are unique to V1 and V

Cortical effects of brief daily periods of unrestricted vision during early monocular form deprivation

Experiencing daily brief periods of unrestricted vision during early monocular form deprivation prevents or reduces the degree of resulting amblyopia. To gain insight into the neural basis for these protective effects, we analyzed the monocular and binocular response properties of individual neurons in the primary visual cortex (V1) of macaque monkeys that received intermittent unrestricted vision. Microelectrode-recording experiments revealed significant decreases in the proportion of units that were dominated by the treated eyes, and the magnitude of this ocular dominance imbalance was correlated with the degree of amblyopia. The sensitivity of V1 neurons to interocular spatial phase disparity was significantly reduced in all treated monkeys compared with normal adults. With unrestricted vision, however, there was a small but significant increase in overall disparity sensitivity. Binocular suppression was prevalent in monkeys with constant form deprivation but significantly reduced by the daily periods of unrestricted vision. If neurons exhibited consistent responses to stimulation of the treated eye, monocular response properties obtained by stimulation of the two eyes were similar. These results suggest that the observed protective effects of brief periods of unrestricted vision are closely associated with the ability of V1 neurons to maintain their functional connections from the deprived eye and that interocular suppression in V1 may play an important role in regulating synaptic plasticity of these monkeys

Pachychoroid neovasculopathy has clinical properties that differ from conventional neovascular age-related macular degeneration

Abstract To determine the clinical properties of pachychoroid neovasculopathy (PNV) that differ from conventional neovascular age-related macular degeneration (nAMD) and suggest that they are different clinical entities. To accomplish this, we reviewed the medical records of 100 consecutive patients diagnosed with nAMD. All of the patients were Japanese, and their mean age was 75.5 years. There were 72 men and 28 women. For the bilateral cases, only the right eye was analyzed. An eye was diagnosed with PNV when a macular neovascularization (MNV) was detected just above the dilated choroidal vessels. The Indocyanine green angiographic (ICGA) and en face optical coherence tomographic (OCT) images were used to assess the vertical symmetry of the medium and large choroidal vessels. The subfoveal choroidal thickness (SCT) was also measured manually in the OCT images. After reclassification, there were 29 (29%) patients with typical nAMD (25 with type 1 MNV, 4 with type 2 MNV), 43 (43%) with PNV, 21 (21%) with polypoidal choroidal vasculopathy, and 7 (7%) with retinal angiomatous proliferation. Of the 43 PNV, 17 (39.5%) had polypoidal lesions and 26 (60.5%) had no polypoidal lesions. The percentage of eyes with vertical asymmetry of the medium and large choroidal vessels was significantly greater in the 35 PNV (81.4%) than in the 16 non-PNV (28.1%; P < 0.01) cases. The mean SCT was significantly thicker in the PNV eyes than in the non-PNV eyes (298 ± 96 μm vs. 228 ± 82 μm; P < 0.01). The response of PNV to anti-vascular endothelial growth factor treatments was better than that of non-PNV eyes [higher dry macula rate after the loading period (90.9% vs. 59.1%), fewer total number of injections (11.0 ± 2.9 vs. 13.4 ± 3.2), and longer treatment intervals for the anti-VEGF therapy (8.4 ± 3.1 vs. 13.4 ± 3.2 weeks) at 2 years (all P < 0.01)]. These differences in the morphology and response to anti-VEGF treatments suggest that PNV is a separate clinical entity to conventional nAMD

Detection of retrobulbar blood vessels in optical coherence tomography angiographic images in eyes with pathologic myopia

Purpose: To report the detection of retrobulbar blood vessel in the optical coherence tomography angiographic (OCTA) images of two eyes with pathologic myopia. Observations: Two eyes of 2 cases with pathologic myopia were examined by OCTA (RTVue XR Avanti, Optovue, and Cirrus 5000, Zeiss). Case 1 was a 64-year-old man, and Case 2 was a 65-year-old woman. In Case 1, the thickness of the subfoveal choroid was 38 μm and the sclera was 274 μm, and they were 17 μm and 214 μm, respectively, in Case 2. The axial length was 35.8 mm in Case 1 and 29.5 mm in Case 2. The choroidal vessels were clearly visible in the choriocapillary slab in both the RTVue and the Cirrus images. The vessels were visible in the area of the retinal pigment epithelial and choriocapillaris atrophy due to the pathologic myopia. The retrobulbar blood vessels temporal to fovea were seen in the OCTA images at the level of the outer aspect of the sclera in both cases. Cross sectional images of the retrobulbar blood vessel in both cases were observed under the sclera in serial scan images overlaid with blood flow. Conclusions: and Importance: These in situ images of the retrobulbar blood vessels that were obtained by OCTA was possible because of the thinness of the choroid and sclera and atrophy of the choriocapillaris in these eyes with pathologic myopia. We conclude that OCTA might have utility to study the retrobulbar vascular alterations in eyes with pathologic myopia

Visualizing large choroidal blood flow by subtraction of the choriocapillaris projection artifacts in swept source optical coherence tomography angiography in normal eyes

Abstract Optical coherence tomography angiography (OCTA) seems not to image the choroidal blood flow pattern in the normal individual because of the OCT light attenuation. Our purpose in the current study was to visualize the large choroidal blood flow pattern after subtraction of the choriocapillaris projection artifact in normal eyes non-invasively by swept source (SS) OCTA. Sixty-one eyes of 45 individuals (19 men, 26 women) without ocular disease were examined by SS-OCTA (AngioPlex Elite 9000, Zeiss, Germany). A 12 × 12 mm macular area was scanned. Subfoveal choroidal thickness (SCT) was measured, and the choroidal blood flow pattern in a slab of 30 µm width at one-half of SCT was analyzed. In examining the choroidal blood flow pattern, a slab that was between 30 to 60 µm posterior to the retinal pigment epithelium, in which the choriocapillaris blood flow was most clearly imaged, was used for the subtraction of the projection artifacts from the choriocapillaris on the stromal area of choroid. The ratio (%) of the choroidal blood flow area in the whole choroidal region was calculated after binarization. Thirty-four eyes of 27 individuals (12 men, 15 women) were also examined by spectral domain OCTA (SD-OCTA). After the subtraction, the middle and large choroidal blood flow were clearly visible in SS-OCTA in all eyes. The mean SCT was 297 ± 61 µm, and the mean ratio of the choroidal blood flow area was 27.3 ± 8.2%, which was significantly correlated with SCT (R = 0.738, P < 0.01). SD-OCTA did not show the choroidal blood flow pattern. In conclusion, removal of the projection artifacts of choriocapillaris can make the choroidal blood flow visible in SS-OCTA of normal eyes. Because the ratio of choroidal blood flow area was correlated with SCT, the choroidal blood flow might be an important factor related to the choroidal thickness

Comparisons of interocular suppression in V1 neurons of normal neonatal and infant strabismus monkeys

Background: V1 neurons in neonatal monkeys (6–14 days of age) show a higher prevalence of interocular suppression than in adults to both interocularly matched (iso-oriented) and unmatched (orthogonally-oriented) gratings. However, the prevalence of these suppressive interactions rapidly decreases to normal adult levels by 8 weeks of age (Endo et al, 2001). In this study we investigated how early onset strabismus influenced this normal maturation of binocular signal interactions. Methods: Strabismus was optically simulated in 8 infant rhesus monkeys using a prism-rearing procedure. The onset of strabismus was at 2 weeks of age (before the know onset age for stereopsis), and 4 or 6 weeks of age (after stereopsis onset), and the duration was 14 days (short) and 4 or 8 weeks (long). Immediately after the end of the rearing period, we conducted the microelectrode recording experiments. Results: In all strabismic infants, the binocular signal interactions in V1 neurons were very similar to those that were found in normal neonatal monkeys. Specifically, the strabismic monkeys exhibited a higher than normal prevalence of interocular suppression and the prevalence of interocular suppression for the orthogonally oriented gratings was nearly identical to that for binocularly matched gratings. Conclusions: These findings suggest that the higher than normal prevalence of interocular suppression in V1 in both strabsimic and normal neonatal monkeys has similar underlying causes. One possibility is that the effectiveness of excitatory binocular connections, both local and long-range, is reduced in strabsimic subjects due to early conflicting binocular inputs or in normal neonates due to retinal and/or cortical immaturities, while inhibitory inputs are largely spared or, at least relatively, more mature (Sepigel et al, 1996; Smith et al, 1997; Kumagami et al, 2000)

Misalignment of center of foveal avascular zone and center of photoreceptors in eyes with history of retinopathy of prematurity

Abstract To determine the relationship between the center of the foveal avascular zone (FAZ) and the center of the foveal photoreceptors in eyes with a history of retinopathy of prematurity (ROP). To accomplish this, we reviewed the medical records of patients with ROP who were examined at the ROP Clinic of the Tokyo Women's Medical University Hospital. We studied 43 eyes of 23 children with ROP and 67 eyes of 36 control children without any fundus abnormalities. The optical coherence tomography angiographic (OCTA) en face images were used to measure the size and location of the foveal avascular zone (FAZ), and cross-sectional OCT images to measure the central retinal thickness (CRT). Our results showed that the size of the FAZ was significantly smaller in the ROP group (0.200 ± 0.142 mm2) than in the control group (0.319 ± 0.085 mm2; P < 0.01). The CRT was significantly thicker in the ROP group (228 ± 30 µm) than in the control group (189 ± 13 µm; P < 0.01). The mean length of the foveal bulge was not significantly different between the two groups. The actual distance of the misalignment between the center of the FAZ and the center of the photoreceptors was significantly greater in the ROP group (50.4 ± 29.5 µm) than in the control group (39.6 ± 21.9 µm; P = 0.001). The correlations between the actual distance of misalignment and the size of the FAZ, CRT, and length of the foveal bulge in both groups were not significant. Despite the significant misalignment in eyes with a history of ROP, the center of the foveal photoreceptors was consistently located within the narrow FAZ which indicates that the development of the FAZ and photoreceptor formation are interrelated