Temporal Retina Research Articles

Spectral-Domain OCT Findings of Retinal Vascular–Avascular Junction in Infants with Retinopathy of Prematurity

Bedside examination of premature infants at risk for retinopathy of prematurity (ROP) is predominantly performed with ophthalmoscopic en face viewing of the retina. While postmortem retinal microstructures have been studied at the vascular-avascular junction, a critical location for pathogenesis of ROP, to date this has not been possible in vivo. Here we present bedside, non-sedated in vivo cross-sectional imaging and analysis of retinal microstructures at the vascular-avascular junction in infants with ROP using handheld spectral-domain optical coherence tomography (SDOCT). Prospective observational study. Eleven preterm infants consented for research imaging during ROP screening examinations. We imaged the vascular-avascular junction in the temporal retina using a SDOCT system (Envisu, Bioptigen Inc., NC) in 18 eyes from 11 preterm infants with zone I or II, stage 0 through 4 ROP. B-scan and en face images were analyzed and compared to historical light micrographs. SDOCT morphology at the vascular-avascular junction. Multiple bedside SDOCT findings at the vascular-avascular junction were comparable to historic light micrographs: thickened inner retinal ridge structure in stage 2 ROP was comparable to thickened vanguard and rear guard cells in micrographs; vascular tufts on the posterior retinal surface in stage 2 ROP, broad arcs of neovascularization above the retina in stage 3 ROP, and splitting of inner retinal layers into clefts on either side of neovascularization mimicked findings of historic light micrographs. A unique findings was thickening of the avascular inner retinal band adjacent to neovascularization. On SDOCT imaging over several weeks, neovascularization and retinal clefts diminished after intravitreal bevacizumab therapy. Retinal morphology at the vascular-avascular junction imaged with handheld SDOCT is consistent with known histopathology, and provide the advantage of monitoring change in vivo over time. These unique findings provide new insights into preterm retinal neurovascular development in ROP.

Sickle cell maculopathy: Identification of systemic risk factors, and microstructural analysis of individual retinal layers of the macula.

PurposeTo identify systemic risk factors for sickle cell maculopathy, and to analyze the microstructure of the macula of Sickle Cell Disease (SCD) patients by using automated segmentation of individual retinal layers.MethodsThirty consecutive patients with SCD and 30 matched controls underwent spectral-domain optical coherence tomography (SD-OCT) and automated thickness measurement for each retinal layer; thicknesses for SCD patients were then compared to normal controls. Demographic data, systemic data, and lab results were collected for each SCD patient; multivariate logistic regression analysis was used to identify potential risk factors for sickle cell maculopathy.ResultsOngoing chelation treatment (p = 0.0187) was the most predictive factor for the presence of sickle cell maculopathy; the odds were 94.2% lower when chelation was present. HbF level tended to influence sickle cell maculopathy (p = 0.0775); the odds decreased by 12.9% when HbF increased by 1%. Sickle cell maculopathy was detected in 43% of SCD patients as patchy areas of retinal thinning on SD-OCT thickness map, mostly located temporally to the macula, especially in eyes with more advanced forms of sickle cell retinopathy (p = 0.003). In comparison to controls, SCD patients had a subtle thinning of the overall macula and temporal retina compared to controls (most p<0.0001), involving inner and outer retinal layers. Thickening of the retinal pigment epithelium was also detected in SCD eyes (p<0.0001).ConclusionsChronic chelation therapy and, potentially, high levels of HbF are possible protective factors for the presence of sickle cell maculopathy, especially for patients with more advanced forms of sickle cell retinopathy. A subtle thinning of the overall macula occurs in SCD patients and involves multiple retinal layers, suggesting that ischemic vasculopathy may happen in both superficial and deep capillary plexi. Thinning of the outer retinal layers suggests that an ischemic insult of the choriocapillaris may also occur in SCD patients.

Characteristics of Retinal Breaks and Surgical Outcomes in Rhegmatogenous Retinal Detachment in Familial Exudative Vitreoretinopathy

To determine the characteristics of retinal breaks and surgical outcomes in eyes with a rhegmatogenous retinal detachment (RRD) with familial exudative vitreoretinopathy (FEVR). Retrospective, noncomparative case series. Thirty-seven patients (46 eyes) with a RRD in FEVR. The medical records were reviewed and the types, directions, and positions of the retinal breaks and surgical outcomes were analyzed. Fundus examinations, including ophthalmoscopy, fluorescein angiography, and RetCam imaging (Natus Medical Incorporated, Pleasanton, CA). The retinal breaks were identified as tears in 12 eyes, atrophic holes in 24 eyes, tears and atrophic holes in 2 eyes, dialysis-related in 1 eye, a retinal break in the ora serrata in 1 eye, and unidentified in 6 eyes. Most retinal breaks (86.1%) were identified only in the temporal retina. Most tears (85.7%) were observed on the demarcation line, whereas atrophic holes were identified both on the demarcation line (53.8%) and the avascular retina (42.3%). The representative tears were almond-shaped, which differs from the typical horseshoe-shaped tears. Scleral buckling was performed as the initial surgery in 37 eyes and resulted in reattachment in 35 eyes (94.6%). Vitrectomy with or without scleral buckle was performed for eyes with more complex RRD in FEVR and resulted in reattachment in 5 of 9 eyes (55.6%). In total, reattachment was achieved in 40 of 46 eyes (87.0%). There was a history of stage 1A or 2A FEVR in 45 eyes and a history of stage 2B FEVR in 1 eye. Our data clarified the types, directions, and positions of the retinal breaks and the effectiveness of scleral buckling as the first surgical choice for treating RRDs in FEVR.

Executive Laterality: Evidence from Hemisometry, Hemisity, and MRI

The bilateral human brain includes structures producing a preconscious executive element, the source of the final decision to act. This executive element appears to be located unilaterally in the brain on the larger side of the anterior cingulate cortex. In a given individual, its side of residence is genetically determined in idiosyncratic manner by a phenomenon called hemisity. Using flash hemisometers, a single 0.5ms flash was directed to both cerebral hemispheres of the subject simultaneously. This was done either by stimulating nasal retinal surfaces or temporal retinal surfaces of the subject's eyes. Of 91 subjects, 87 (96%) reported seeing two flashes; the first appearing on one idiosyncratic side, closely followed by another on the same side. Yet, only single flashes were reported when nasal and temporal retinae were simultaneously stimulated. This non-intuitive two flash result would occur if on one side of the brain the flash went directly to a unilateral executive observer to be seen first. Because the flash going to the other, non-executive side of the brain would not be perceived there, it would have to cross the corpus callosum to reach the executive observer as a delayed second flash. Here, the individual brain side of the executive observer determined by this method was highly correlated with each subject's larger anterior cingulate and MRI-calibrated hemisity. These results provide confirmatory evidence for the existence of executive laterality.

Medical management of a subretinal Klebsiella pneumoniae abscess with excellent visual outcome without performing vitrectomy

To report the case of a Klebsiella pneumoniae endogenous endophthalmitis (KPEE) of hepatic and urinary origin that was successfully treated with systemic antibiotherapy and 13 intravitreal antibiotics injections without performing a vitrectomy. Case report of a 60-year-old man with a subretinal abscess in the left eye that developed 3 days after initial presentation for K.pneumoniae bacteremia, liver abscess and urinary tract infection. Ophthalmic examination of the left eye showed anterior uveitis and a single subretinal abscess located in mid-peripheral temporal retina. BCVA dropped to 20/50. Follow-up was made with clinical examination and multimodal imaging (SD-OCT, FA, ICGA) with high field photographs. A total of 13 intravitreal injections (IVI) of ceftazidime were performed, and no vitrectomy was required. Ocular signs regressed and prognosis was excellent with 20/20 of final BCVA. KPEE is a rare but severe condition with a typically poor ocular prognosis. When diagnosis is made early, subretinal abscess with partially conserved BCVA could be treated successfully with medical management that includes systemic antibiotics and repeated intravitreal injections without requiring vitrectomy.

ERP responses greater for faces in the temporal compared to the nasal visual field.

The distribution of retino-tectal projections is dissimilar depending on whether the receptors are situated in the nasal and temporal visual hemiretinas. Indeed, it has been claimed that the superior colliculus receives a greater proportion of its input from the temporal visual hemifield (nasal hemi-retina) relative to the nasal hemifield (temporal hemi-retina). In order to investigate whether these subcortical projections influence face processing, we investigated the early cortical ERP responses to faces and houses presented in the temporal and nasal retinas using monocular viewing. Neutral or fearful faces were presented concurrently with houses on either side of a central fixation cross, while participants were asked to discriminate changes in luminance at the center. Results showed that the lateralized N170, computed as the contralateral-ipsilateral electrode difference, was greater for faces appearing in the nasal relative to the temporal visual hemifield. This was due to a greater ipsilateral N170 for temporal relative to nasal presentations. By contrast, no difference was found across emotional expressions. The enhanced ERP response to faces appearing in the temporal visual field, suggests that the retinotectal pathway modulates cortical processing, most likely through activation of a colliculo-pulvino-amygdalar pathway, with subsequent back-projections from the amygdala to visual cortical regions. However, unattended facial expressions do not seem to modulate the response, at least at these angles of eccentricity.

A Modified Foveal Advancement Technique in the Treatment of Persistent Large Macular Holes.

To evaluate the outcomes of a new surgical technique on the closure of persistent large macular holes (MHs) PATIENTS AND METHODS:Data for 10 eyes of 10 patients who underwent surgical intervention for the treatment of large and persistent MHs were reviewed retrospectively. After entrance of the three-port transconjunctival 23-gauge sutureless vitrectomy instruments, a shallow perihole retinal detachment was formed by injecting a small amount of fluid with a 39-gauge /41-gauge subretinal cannula under the perihole (superior, temporal, and inferior sparing nasal bundle fibers) retina. Edges of the hole were brought closer with small, passive aspirations by a silicone-tipped cannula. After fluid-air exchange, a 39-gauge /41-gauge cannula was placed over the hole to remove submacular fluid. Then air was changed with 20% sulfur hexafluoride endotamponade. Mean minimum hole diameter was 691 μm ± 98 μm (range: 500 μm to 812 μm), and mean basal diameter was 1,604 μm ± 321 μm (range: 1,066 μm to 2,200 μm). Preoperative best spectacle-corrected visual acuities (BSCVAs) were lower than 20/200 in eight patients and were 20/200 in two patients. MHs were successfully closed in all eyes (100%). BSCVA did not change in two patients and were lower than 20/200. BSCVAs were 20/200 in six patients and greater than 20/200 in two patients. The ellipsoid zone (EZ) was lost in all patients. All the large and persistent MHs were successfully closed and stayed closed during follow-up period. However, increase in visual acuities was limited, which was related to the loss of the EZ. The authors' modified technique seems to be a good option for the surgical treatment of large and persistent MHs. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:793-798.].

Retinal Findings of a Unique RTEL1 Mutation in Dyskeratosis Congenita

We describe the retinal manifestations of a patient with a unique mutation of the Regulator of telomere length 1 ( RTEL1) gene resulting in dyskeratosis congenita (DC), a rare, fatal, inherited disease. A 4-year-old boy with DC was referred for ophthalmology consult by his attending hematologist and underwent a complete ophthalmic examination, including wide-field fundus imaging and fluorescein angiography. The patient was found to have bilateral retinal vasculopathy and extensive microvascular abnormalities in addition to avascular regions in the temporal peripheral retina. He received multiple pan-retinal photocoagulation treatments in both eyes. Our case highlights the importance of ophthalmic screening and fluorescein angiography and the potential need for timely laser photocoagulation for sight-threatening retinopathy in patients with DC.

New insights on the anatomy and function of the retina in sickle cell disease

IntroductionThe recent rise of OCT showed that asymptomatic atrophy of the median temporal raphe of the retina (ATR) was a frequent occurrence in sickle cell disease (SCD). However, the prevalence, mechanisms and significance of ATR is not known, especially in the paediatric field.MethodsSCD‐children prospectively underwent a fundus examination and an OCT of the macula and the temporal retina. Atrophy of the MTR was quantified on thickness maps. Data from brain imaging were collected in SS‐type SCD children.ResultsEighty‐one children were studied; 64.2% exhibited ATR, while 29.2% had peripheral SCD retinopathy. ATR was often limited to areas located temporally from the usual macular map OCT programs, so that it could be missed with these programs. Patients with peripheral retinopathy were more likely to also exhibit ATR (p = 0.02). While peripheral retinopathy was significantly associated with the children age (p = 0.02), ATR was not.ConclusionATR seems to occur very early in children with SCD and to display most distinct features from the well‐known peripheral SCD retinopathy.

Increased Retinal Thinning after Combination of Internal Limiting Membrane Peeling and Silicone Oil Endotamponade in Proliferative Diabetic Retinopathy

Background: The aim of this study was to examine the change in retinal thickness after vitrectomy with internal limiting membrane (ILM) peeling and/or silicone oil (SO) endotamponade in proliferative diabetic retinopathy (PDR). Methods: The actual amount and ratio of changes in the retinal thickness were calculated. Results: Compared to control eyes in the ILM peeling (-)/SO (-) group, the central, superior inner, and temporal inner retina in the ILM peeling (+)/SO (-) group, the central and superior inner retina in the ILM peeling (-)/SO (+) group, and the central, inferior inner, temporal inner, and nasal inner retina in the ILM peeling (+)/SO (+) group showed a significant reduction of the retinal thickness. The central, superior inner, and temporal inner retina in the ILM peeling (+)/SO (-) group, the central and superior inner retina in the ILM peeling (-)/SO (+) group, and the central, superior inner, inferior inner, and temporal inner retina in the ILM peeling (+)/SO (+) group showed a significantly increased reduction rate of the retinal thickness compared to the control group. Conclusions: Macular retinal thinning in PDR was observed after ILM peeling and SO endotamponade, and it was increased by the combination of these 2 factors.

The Effect of Spectacle Lenses Containing Peripheral Defocus on Refractive Error and Horizontal Eye Shape in the Guinea Pig.

PurposeIt has been proposed that the peripheral retina, responding to local optical defocus, contributes to myopia and associated altered eye growth in humans. To test this hypothesis, we measured the changes in central (on-axis) and peripheral ocular dimensions in guinea pigs wearing a concentric bifocal spectacle lens design with power restricted to the periphery.MethodsFive groups of guinea pigs (n = 83) wore either a unifocal (UF) spectacle lens (−4, 0, or +4 Diopters [D]), or a peripheral defocus (PF) spectacle lens that had a plano center (diameter of 5 mm) with either −4 or +4 D in the surround (−4/0 or +4/0 D). The overall optical diameter of all lenses was 12 mm. Lenses were worn over one eye from 8 to 18 days of age for negative and plano lenses, or from 8 to 22 days of age for positive lenses. Refractive error was measured centrally and 30° off-axis in the temporal and nasal retina. The shape of the eye was analyzed from images of sectioned eyes.ResultsLenses of −4 D UF induced myopia, reflecting enhanced ocular elongation, which was centered on the optic nerve head and included the surrounding peripapillary zone (PPZ, 18° in diameter). Some ocular expansion, including within the PPZ, also was recorded with −4/0 and +4/0 D PF lenses while the +4 D UF lens inhibited rather than enhanced elongation, centrally and peripherally.ConclusionsPeripheral defocus-induced ocular expansion encompasses the PPZ, irrespective of the sign of the inducing defocus. Understanding the underlying mechanism potentially has important implications for designing multifocal lenses for controlling myopia in humans and also potentially for understanding the link between myopia and glaucoma.

The relationship between retinal nerve fibre layer thickness profiles and CorvisST tonometry measured biomechanical properties in young healthy subjects

We previously reported that a shallow circumpapillary retinal nerve fiber layer (cpRNFL) peak angle as measured by optical coherence tomography (OCT) suggests the temporal retina is stretched around the optic disc from the papillo-macular bundle (Yamashita T et al. Investigative Ophthalmol Vis Sci 2013). The purpose of the current study was to investigate the relationship between CorvisST tonometry (CST) corneal measurements, axial length (AL) and the change in OCT-measured cpRNFL peak angle, in young healthy subjects. OCT and CST measurements were carried out in 97 eyes of 97 young healthy volunteers. The relationship between cpRNFL peak angle and 12 CST parameters, adjusted for AL, was investigated using linear modelling. The mean ± standard deviation cpRNFL peak angle of the 97 healthy volunteers was 130.6 ± 25.4 (range: 77.8 to 207.0) degrees. The optimal linear model to explain cpRNFL peak angle (chosen from 216 different models) included three CST variables related to the speed and size of energy absorption (namely, A1 time, A1 length and A2 time), in addition to AL. In eyes with longer AL and shorter energy absorption in CST measurement, temporal retina is stretched around the optic disc from the papillo-macular bundle, as suggested by a shallow cpRNFL peak angle.

Spherical Soft Contact Lens Designs and Peripheral Defocus in Myopic Eyes.

Peripheral retinal defocus has been implicated in myopia progression. The effect of commercially available spherical soft contact lenses (SCLs) on peripheral defocus of adult myopic eyes was investigated. Twenty-five young adults with spherical equivalent (SE) refractions between -0.50D and -6.00D were enrolled. Cycloplegic autorefraction (right eye) was measured centrally and ±20°, ±30°, and ±40° from the line of sight along the horizontal meridian using an autorefractor. Four commercially available spherical SCLs (Biofinity, Acuvue2, PureVision2, and Air Optix Night & Day Aqua) were evaluated. SE defocus (M) was used to calculate relative peripheral defocus (RPD) while wearing each SCL and relative peripheral refraction of the uncorrected eye. Spherical aberration (SA) changes caused by each SCL were measured along the line of sight by aberrometry. Peripheral defocus was analyzed using repeated-measures analyses of variance (RM-ANOVA). The association between changes in axial SA and the change in peripheral defocus was evaluated using linear mixed models. The mean age (±SD) and central SE refractive error were 24.0 ± 1.3 years and -3.45 ± 1.42D, respectively. PureVision2 did not change RPD (P = .33). Significant myopic shifts on the temporal retina were found with three lenses: Acuvue 2 (-0.29D at 30°; -0.80D at 40°; both P ≤ .01), Biofinity (-1.21 D at 40°; P = .02), and Air Optix Night & Day Aqua (-0.23D at 20°, -0.48D at 30°, and -1.50D at 40°; all P < .004). All SCLs caused a negative change in SA. SCLs inducing less negative (more positive) SA changes were associated with a less hyperopic change in RPD. Spherical SCL design can influence the peripheral defocus profile experienced by a myopic eye. Several, but not all, SCLs reduced peripheral hyperopia. Differences in how SCL types influence peripheral defocus may have implications for myopia progression.

Senescent Changes and Topography of the Dark-Adapted Multifocal Electroretinogram.

PurposeTo investigate the topographic changes of the dark-adapted multifocal electroretinogram (mfERG) across adulthood in the central retina and compare the topography between macular versus extramacular, nasal versus temporal, and inferior versus superior retinal areas.MethodsSixty-five subjects (18–88 years) received a comprehensive dilated eye examination to ensure the health of their retina and were tested with a dark-adapted mfERG protocol using a 61-hexagon pattern. The lens absorption of each subject was also estimated using a heterochromatic flicker photometry (HFP) paradigm.ResultsThe response amplitude and latency of the dark-adapted mfERG showed a significant change with age, which was best described with a linear model. All the retinal areas examined demonstrated similar aging effects. The extramacular and temporal retina showed higher response amplitude and faster response latency when compared with the macular and nasal retinae, respectively. No difference was found in response amplitude and latency between the inferior and superior retina. The HFP results also showed a significant correlation with age, consistent with senescent increases in short wavelength absorption by the crystalline lens. However, the change in lens absorption did not exceed the magnitude of the change in response amplitude and latency.DiscussionOur results indicate that there is a decline in dark-adapted retinal activity as measured with the mfERG. These aging processes affect rods and rod-bipolar cells. Their decrease in response can be attributed to both optical and neural factors.

Multifocal Electroretinogram in normal subjects

Background: Multifocal electroretinogram (mfERG) is a device for recording the physiological response of multiple retinal areas in short time. Using this technique enables us to detect the spatial extent and severity of the retinal damage. Objectives: In this study,we aimed to assess the topographic properties of mfERG in normal subjects to use it as a basic data to evaluate eye disease. Methods: We recorded mfERG from 20 eyes of 20 normal subjects. We measured amplitude and latency of recorded waves. We compared between amplitude of these waves between different retinal areas and the same for latency. Results: We found mfERG responses in the form of waves, every wave consists of negative wave (N1) followed by positive wave (P1). The amplitude of N1 wave and amplitude of P1 were largest at the fovea and decreased toward periphery. The latency of N1 and P1 were shorter in upper retina than lower retina. The N1 amplitude and P1 amplitude was larger in upper retina than lower retina, which reflex functional superiority of upper retina. There was no statistical difference between nasal and temporal retina in the amplitude and latency.Conclusion: Multi-focal ERG would be useful for objective examination of the retinal function.

Internal limiting membrane dsytrophy: a case series study of a rarely reported retinal dystrophy

Purpose The purpose of this study was to describe the clinical features of 10 cases of a rarely reported internal limiting membrane dystrophy with glistening retinal reflex and peculiar fundus mottling. Patients and methods This is a retrospective review of 10 patients attending the outpatient clinic of Mansoura Ophthalmic Center in the period between 2000 and 2014. For all cases, measuring BCVA, fundus examination and fundus fluorescein angiography were done. Optical coherence tomography (OCT) was done for nine patients, with one patient missed (was not accessible for the investigation). Results The study included 10 unrelated patients − three female and seven male. The age ranged from 21 to 36 years (mean: 27±0.5 years). The mean visual acuity was 0.3±0.04. In all cases, fundus examination revealed the presence of a peculiar reddish mottling, with glistening retinal reflex and areas of epiretinal membranes and distortion of retinal blood vessels. Fundus fluorescein angiography revealed capillary dye leakage all over the retina with cystoid macular edema in five eyes. In one patient, abrupt cessation of retinal blood vessels was evident in the temporal retina. OCT revealed the presence of epiretinal membranes and schisis cavities in all retinal layers. Secondary choroidal neovascular membrane was evident in one eye. Conclusion Internal limiting membrane dystrophy is an extremely rare hereditary disorder that presents early in life (second-third decade) with early drop of vision. Clinically, it presents with glistening retinal surface, epimacular membranes and peculiar reddish mottling of the whole retina extending from the central retina to the far periphery. Fluorescein angiography shows capillary leakage all over the retina and cystoid macular edema. OCT shows schiscis cavities in all retinal layers. Some cases are complicated by choroidal neovascular membrane.

Retinal Angiomatous Proliferation in Adult Onset Coat's Disease Angiomatous Proliferation in Coat's Disease

A 31 year old female patient had decreased vision in her left eye for several months. Visual acuity was 20/20 in right eye and counting fingers from 2 m in left eye. Examination of left eye demonstrated massive macular exudation with grayish discoloration of central macula and, aneurysmal and telangiectatic vessels with surrounding exudation in temporal mid peripheral retina. Optical coherence tomography of left eye showed findings consistent with neovascular complex, pigment epithelial detachment, subretinal fluid and involvment of choroid. There was hyperfluorescent focus with perfusing retinal arteriole and draining venule at the fovea which was compatible with retinal angiomatous proliferation (RAP) in early phase fundus fluorescein angiography and leakage was observed in late phase. After 3 doses of monthly-injected intravitreal ranibizumab and argon laser photocoagulation applied on aneurysmal and telangiectatic vessels, we observed central macular fibrosis, minimal lipid exudation and no macular edema. So retinal angiomatous proliferation may be a feature of adult onset Coats’ disease.

Binocular vs. monocular hue perception

Hue perception has been shown to differ for the same stimulus when presented to the temporal and the nasal areas of the retina. The present study investigated perceptual differences in stimuli viewed binocularly or monocularly in the peripheral retina to determine how hue information combines across the two retinas for a stimulus falling on the temporal retina of one eye and the nasal retina of the other. A hue-scaling procedure was utilized to ascertain hue perception for three color- and binocular-normal observers viewing monochromatic stimuli (450–670nm, 20nm steps) ranging in size from 1.0° to 3.7°. Peripherally-presented binocular stimuli fell upon the nasal retina of one eye and the temporal retina of the other. Hue-scaling results indicated that peripheral binocular hue and saturation perceptions for smaller stimuli were more similar to those of stimuli falling on the temporal retina in the monocular condition. Hue-scaling data were also used to determine perceptive field sizes for the four elemental hues. Binocular perceptive field sizes were more similar to those obtained for stimuli falling on the temporal retina in the monocular conditions. Eye dominance did not appear to have an effect on hue perception. The results seem to indicate that visual information from the temporal retina is weighted more heavily when information from the two eyes is combined cortically. This finding may relate to differences in V1 cortical activation for stimuli presented to the nasal retina versus the temporal retina.

Hemifield columns co-opt ocular dominance column structure in human achiasma

In the absence of an optic chiasm, visual input to the right eye is represented in primary visual cortex (V1) in the right hemisphere, while visual input to the left eye activates V1 in the left hemisphere. Retinotopic mapping In V1 reveals that in each hemisphere left and right visual hemifield representations are overlaid (Hoffmann et al., 2012). To explain how overlapping hemifield representations in V1 do not impair vision, we tested the hypothesis that visual projections from nasal and temporal retina create interdigitated left and right visual hemifield representations in V1, similar to the ocular dominance columns observed in neurotypical subjects (Victor et al., 2000). We used high-resolution fMRI at 7T to measure the spatial distribution of responses to left- and right-hemifield stimulation in one achiasmic subject. T2-weighted 2D Spin Echo images were acquired at 0.8mm isotropic resolution. The left eye was occluded. To the right eye, a presentation of flickering checkerboards alternated between the left and right visual fields in a blocked stimulus design. The participant performed a demanding orientation-discrimination task at fixation. A general linear model was used to estimate the preference of voxels in V1 to left- and right-hemifield stimulation. The spatial distribution of voxels with significant preference for each hemifield showed interdigitated clusters which densely packed V1 in the right hemisphere. The spatial distribution of hemifield-preference voxels in the achiasmic subject was stable between two days of testing and comparable in scale to that of human ocular dominance columns. These results are the first in vivo evidence showing that visual hemifield representations interdigitate in achiasmic V1 following a similar developmental course to that of ocular dominance columns in V1 with intact optic chiasm.

Neural adaptation to peripheral blur in myopes and emmetropes

In the presence of optical blur at the fovea, blur adaptation can improve visual acuity (VA) and perceived image quality over time. However, little is known regarding blur adaptation in the peripheral retina. Here, we examined neural adaptation to myopic defocus at the fovea and parafovea (10° temporal retina) in both emmetropes and myopes. During a 60-min adaptation period, subjects (3 emmetropes and 3 myopes) watched movies with +2 diopters of defocus blur through a 6-mm artificial pupil in two separate, counter-balanced sessions for each retinal location. VA was measured at 10-min intervals under full aberration-corrected viewing using an adaptive optics (AO) vision simulator. By correcting subjects’ native optical aberrations with AO, we bypassed the influence of the individual subjects’ optical aberrations on visual performance. Overall, exhibited a small but significant improvement after the 60-min of adaptation at both the fovea (mean±SE VA improvement: −0.06±0.04 logMAR) and parafovea (mean±SE VA improvement: −0.07±0.04 logMAR). Myopic subjects exhibited significantly greater improvement in parafoveal VA (mean±SE VA improvement: 0.10±0.02 logMAR), than that of emmetropic subjects (mean±SE VA improvement: 0.04±0.03 logMAR). In contrast, there was no significant difference in foveal VA between the two refractive-error groups. In conclusion, our results reveal differences in peripheral blur adaptation between refractive-error groups, with myopes displaying a greater degree of adaptation.