Projects

Please find an overview and description of the EGRET projects below.

1. Intracranial pressure measured noninvasively in patients with normal tension glaucoma

2. Otoacoustic emissions to probe cochlear frequency selectivity

3. Longitudinal OCT, (f)MRI, and perimetry in a cohort of PD patients (DUPARC) 

4. Longitudinal OCT, (f)MRI, and perimetry in a cohort of glaucoma patients (GLGS)

5. Heritability of eye diseases 

6. Glaucoma screening driven by genetic and other risk factors

7. Motion detection in glaucoma

8. Light adaptation in glaucoma 

9. Using virtual reality to assess visual fields and rehabilitate visual and cognitive functioning

10. Resting-state fMRI in glaucoma subjects

 

1. Intracranial pressure measured noninvasively in patients with normal tension glaucoma 

1

The classical concept of an elevated intraocular pressure (IOP) as primary cause of glaucoma is outdated, or at least incomplete. Current hypotheses focus on (1) the perfusion of the optic nerve head and (2) the difference between IOP and the intracranial pressure (ICP), that is, the pressure gradient over the lamina cibrosa. Some people develop glaucoma without an increase in IOP (normal tension glaucoma [NTG]). A lower than average ICP could contribute to the development of NTG. The gold standard for ICP assessment, the lumbar puncture, is laborious, not patient friendly, and not free of risk. In this project, noninvasive methods for measuring ICP (derived from audiology) are refined and performed in patients with NTG, in similar patients with high tension glaucoma (HTG), and in healthy controls. This will provide insight in the etiology of glaucoma, facilitate the diagnosis of especially atypical NTG cases, and impact treatment decisions.

PhD Candidate

Allison Loiselle (MSc Space Physiology and Health)

Supervision

Prof. Nomdo Jansonius (www.nomdo.nl/research.htm)

Prof. Pim van Dijk (www.rug.nl/staff/p.van.dijk/)

Dr. ir. Emile de Kleine http://www.rug.nl/staff/e.de.kleine/

References

Berdahl JP, Fautsch MP, Stinnett SS, Allingham RR (2008) Intracranial pressure in primary open angle glaucoma, normal tension glaucoma, and ocular hypertension: a case-control study. IOVS 49:5412-8

Berdahl JP, Allingham RR, Johnson DH (2008) Cerebrospinal fluid pressure is decreased in primary open-angle glaucoma. Ophthalmology 115:763-8

Dijk P van, Maat B, Kleine E de (2011) The effect of static ear canal pressure on human spontaneous otoacoustic emissions: spectral width as a measure of the intra-cochlear oscillation amplitude. J Assoc Res Otolaryngol 12:13-28

Fleischman D, Allingham RR (2013) The role of cerebrospinal fluid pressure in glaucoma and other ophthalmic diseases: A review, Saudi Journal of Ophthalmology 27:97-106

Kleine E de, Wit HP, Avan P, Dijk P van (2001) The behavior of evoked otoacoustic emissions during and after postural changes. J Acoust Soc Am 110:973-80

Kleine E de, Wit HP, Dijk P van, Avan P (2000) The behavior of spontaneous otoacoustic emissions during and after postural changes. J Acoust Soc Am 107:3308-16

Morgan WH, Yu DY, Cooper RL, Alder VA, Cringle SJ, Constable IJ (1995) The influence of cerebrospinal fluid pressure on the lamina cribrosa tissue pressure gradient. IOVS 36:1163–72

Ren R, Jonas JB, Tian G et al (2010) Cerebrospinal fluid pressure in glaucoma: a prospective study. Ophthalmology 117:259–66

Ren R, Zhang X, Wang N, Li B, Tian G, Jonas JB (2011) Cerebrospinal fluid pressure in ocular hypertension. Acta Ophthalmol 89:e142-8

 

2. Otoacoustic emissions to probe cochlear frequency selectivity 

2

Otoacoustic emissions are weak sound emitted by the inner ear. They are related to normal hearing mechanisms in the inner ear. Also, they are expected to be useful for the classification of glaucoma. This project investigates some basic characteristics of spontaneous otoacoustic emissions. Specifically, we will optimize the measurement technique, using a new 2-microphone recording method. Also, otoacoustic emission will be used to assess the frequency selectivity (tuning) of the cochlea, by combining emission measurements with measurements of psychophysical tuning curves. Properties of otoacoustic emissions will also be assessed in young glaucoma patients, in relation to characteristics of their glaucoma and possible hearing loss. This project aims at providing insight into basic hearing mechanisms and their relation glaucoma.

PhD Candidate

Sina Engler (MSc Biology)

Supervision

Prof. Pim van Dijk (www.rug.nl/staff/p.van.dijk/)

Prof. Nomdo Jansonius (www.nomdo.nl/research.htm)

References

Dijk P van, Maat B, Kleine E de (2011) The effect of static ear canal pressure on human spontaneous otoacoustic emissions: spectral width as a measure of the intra-cochlear oscillation amplitude. J Assoc Res Otolaryngol 12:13-28

Shera CA, Guinan, JJ, Oxenham, AJ (2002) Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements. PNAS 99, 3318-3323

 

3. Longitudinal OCT, (f)MRI, and perimetry in a cohort of PD patients (DUPARC) 

3

Parkinson’s disease and glaucoma are both age-related diseases. Moreover, PD patients seem to share common retinal abnormalities with glaucoma patients, suggesting a common pathophysiology. Mitochondrial pathology as a common underlying disease process has been suggested for both diseases. These retinal abnormalities can be studied very nicely using optical coherence tomography (OCT). OCT has shown retinal pathology in several cross-sectional PD studies. The changes were quite variable, but especially the retinal nerve fiber layer (RNFL), the ganglion cell layer (GCL), and inner plexiform layer (IPL), including the dopaminergic amacrine cells, seemed to be affected. The abnormalities in the IPL are of special interest, because previous autopsy studies found a decreased dopamine level in the retina of PD patients. Other studies found correlations between cognitive deterioration with or without visual hallucinations and retinal pathology. So, the question arises how the progression of motor- and non-motor symptoms of PD is related to retinal changes, as measured by OCT, and if these retinal changes are related to the severity of nigral dopaminergic cell loss. Another important question is how the retinal changes in glaucoma differ from those seen in PD over time. The currently available cross-sectional studies cannot answer these questions. Therefore, longitudinal OCT measurements will be applied in a de novo PD group, combined with F-DOPA PET imaging and (f)MRI to characterize the level of dopamine depletion and the visual system, respectively, and detailed assessments of motor- and non-motor symptoms. Finally, to answer the question if a shared mitochondrial pathology could explain the similarities between both conditions, genetics will be applied, focussing on the mitochondrial DNA in both patient groups.

PhD Candidate

Asterios Chrysou (MSc Neuropsychology)

Supervisors

Prof. Teus van Laar (www.movementdisordersgroningen.com)

Prof. Nomdo Jansonius (www.nomdo.nl/research.htm)

Prof. Frans W. Cornelissen (www.visualneuroscience.nl)

References

Archibald NK, Clarke MP, Mosimann, UP, Burn DJ. Retinal thickness in Parkinson’s disease. Parkinsonism & rel disord 2011; 17:431-36

Archibald NK, Clarke MP, Mosimann UP, Burn DJ. The retina in Parkinson’s disease. Brain 2009; 132:1128-45

Bayhan HA, Bayhan SA, Tanık N, Gu C. The Association of Spectral-Domain Optical Coherence Tomography Determined Ganglion Cell Complex Parameters and Disease Severity in Parkinson’s Disease. Current Eye Research 2014; 39:1117–1122

Bodis-Wollner I, Miri S and Glazman S. Venturing Into the No-Man’s Land of the Retina in Parkinson’s Disease. Mov disord 2014; 29:15-22

Harnois C, Di Paolo T. Decreased dopamine in the retinas of patients with Parkinson’s disease. Invest Ophthalmology & Vis Science 1990; 31:2473-75

Jindahraa P, Hedgesb TR, Mendoza-Santiestebanc CE and Planta GE. Optical coherence tomography of the retina: applications in neurology. Current Opinion in Neurology 2010; 23:16–23

Meppelink, A. M., de Jong, B. M., Renken, R., Leenders, K. L., Cornelissen, F. W., & van Laar, T. (2009). Impaired visual processing preceding image recognition in Parkinson’s disease patients with visual hallucinations. Brain, 132, 2980–93. doi:10.1093/brain/awp223

 

4. Longitudinal OCT, (f)MRI, and perimetry in a cohort of glaucoma patients (GLGS)4

Optical coherence tomography (OCT) has formed a revolution in the assessment of retinal disease and has become a useful addition to the diagnostic armamentarium in the field of glaucoma. Thus far, the clinical application of OCT in glaucoma is mainly cross-sectionally: it informs the clinician about the presence or absence of damage of the structures relevant to glaucoma (optic nerve head, retinal nerve fiber layer, and retinal ganglion cell layer). The collection, analysis, and interpretation of longitudinal data – did disease progression occur or not – is a way more complicated. Consequently, the role of OCT in clinical progression detection is still largely unclear. To forward this, this project will address this issue in the cohort of the Groningen Longitudinal Glaucoma Study, for which detailed functional (perimetry) and structural (OCT) data of the eye are available. (f)MRI data will be collected in the same cohort and similar tests will also be done in a cohort of patients with Parkinson disease (project #3) in order to enable a comparison of these two neurodegenerative diseases at all levels along the visual pathways.

PhD Candidate

Tuomas Heikka (MSc Biophysics)

Supervision

Prof. Nomdo Jansonius (www.nomdo.nl/research.htm)

Prof. Teus van Laar (www.movementdisordersgroningen.com)

Prof. Frans W. Cornelissen (www.visualneuroscience.nl)

References

Boucard CC, Hernowo AT, Maguire RP, Jansonius NM, Roerdink JBTM, Hooymans JMM, Cornelissen FW (2009) Changes in cortical grey matter density associated with long-standing retinal field defects. Brain 132:1898-1906

Jansonius NM, Schiefer J, Nevalainen J, Paetzold J, Schiefer U (2012) A mathematical model for describing the retinal nerve fiber bundle trajectories in the human eye: average course, variability, and influence of refraction, optic disc size and optic disc position. Exp Eye Res 105:70-78

Junoy Montolio FG, Wesselink C, Gordijn M, Jansonius NM (2012) Factors that influence standard automated perimetry test results in glaucoma: test reliability, technician experience, time of day and season. Invest Ophthalmol Vis Sci 53:7010-7

Junoy Montolio FG, Wesselink C, Jansonius NM (2012) Persistence, spatial distribution and implications for progression detection of blind parts of the visual field in glaucoma: a clinical cohort study. PLoS ONE 7:e41211

Springelkamp H, Lee K, Ramdas WD, Vingerling JR, Hofman A, Klaver CCW, Sonka M, Abramoff MD, Jansonius NM (2012) Optimizing the Information Yield of 3D OCT in Glaucoma. Invest Ophthalmol Vis Sci 53:8162-71

Springelkamp H, Lee K, Wolfs RCW, Buitendijk GHS, Ramdas WD, Hofman A, Vingerling JR, Klaver CCW, Abràmoff MD, Jansonius NM (2014) Population-based evaluation of retinal nerve fiber layer, retinal ganglion cell layer, and inner plexiform layer as a diagnostic tool for glaucoma. Invest Ophthamol Vis Sci 55:8428-38

 

5. Heritability of eye diseases 

LifeLines (www.lifelines.net) is a multi-disciplinary prospective population-based cohort study examining in a unique three-generation design the health and health-related behaviours of over 165,000 persons living in the North East region of the Netherlands (1, 2). It employs a broad range of investigative procedures in assessing the biomedical, socio-demographic, behavioural, physical, and psychological factors which contribute to the health and disease of the general population, with a special focus on multi-morbidity and complex genetics. Information on the occurrence of eye disease is currently collected using an extensive questionnaire. The unique family structure of LifeLines makes it possible to separate and estimate genetic and environmental influences on these eye diseases. In combination with in-depth collections of complete biomedical risk profiles as well as environmental and lifestyle exposures, Lifelines offers unique opportunities to investigate genetic and environmental sources of individual differences underlying occurrence of eye disease in the general population (3). In a number of sub-studies we will focus on specific eye diseases and, for example, investigate the controversial relationship of low blood pressure as a risk factor for glaucoma. We will also be able to explore the role of the autonomic nervous system using heart rate variability as a proxy for parasympathetic nervous system activity.

PhD Candidate

Nigus G. Asefa (MPH Reproductive Health)

Supervision

Prof. Harold Snieder (www.groningenepidemiology.nl)

Prof. Nomdo Jansonius (www.nomdo.nl/research.htm)

Dr J. Vehof (http://www.rug.nl/staff/j.vehof/)

References

Stolk RP, Rosmalen JGM, Postma DS, de Boer RA, Navis G, Slaets JPJ, et al. Universal risk factors for multifactorial diseases. LifeLines: a three-generation population-based study. European Journal of Epidemiology. 2008;23: 67-74.

Scholtens S, Smidt N, Swertz MA, Bakker SJ, Dotinga A, Vonk JM, et al. Cohort Profile: LifeLines, a three-generation cohort study and biobank. International Journal of Epidemiology. 2014: 1-9.

Klijs B, Scholtens S, Mademakers JJ, Snieder H, Stolk RP, Smidt N. Representativeness of the LifeLines Cohort Study. PLoS ONE. 2015;10: e0137203.

 

6. Glaucoma screening driven by genetic and other risk factors 6

Glaucoma is a chronic eye disease, which eventually can lead to irreversible blindness. Symptoms often go unnoticed because of the insidious nature. Because treatment can slow down the progression of glaucoma, screening could be useful. At this moment, there is no nationwide periodic population-based screening program for glaucoma in the Netherlands nor in any other country. The low prevalence of glaucoma is one reason why glaucoma screening is not obviously cost-effective. The prevalence (prior probability) may be increased by limiting the screening to high-risk groups. Although this might work in some populations, we showed – in a Caucasian population in the Western world with an easily accessible health-care system – that preselection on the basis of known glaucoma risk factors (family history and myopia) would not improve the performance of a screening program. The reason was that patients with these risk factors were already more likely to be picked up in regular care (Stoutenbeek et al. 2008). An alternative approach for the time being is case finding at optician shops (Stoutenbeek and Jansonius 2006; de Vries et al. 2012); for the future, preselection based on a genetic risk profile seems promising. Currently, 65 genes are linked to glaucoma – making glaucoma a classical example of a complex disease (Jansen et al 2013). In the current project, we will assess the genetic risk profile of participants in the population-based LifeLines study (www.lifelines.net; see also project #5) and will combine this with other determinants into a glaucoma risk score. Subsequently, we will compare those with a high risk score to those with a low score. As the participants in LifeLines were not involved in the genome-wide analysis studies underlying the 65 glaucoma genes, this approach gives a unique opportunity to evaluate independently the applicability of this type of knowledge in health care.

PhD Candidate

Anna Neustaeter (MSc Quantitative Genomics)

Supervision

Prof. Nomdo Jansonius (www.nomdo.nl/research.htm)

Prof. Harold Snieder (www.groningenepidemiology.nl)

References

Janssen SF, Gorgels TGMF, Ramdas WD, Klaver CCW, Duijn CM van, Jansonius NM, Bergen AAB (2013) The vast complexity of primary open angle glaucoma: disease genes, risks, molecular mechanisms and pathobiology. Prog Retin Eye Res 37:31-67

Stoutenbeek R, Jansonius NM (2006) Glaucoma screening during regular optician visits: can the population at risk of developing glaucoma be reached? Br J Ophthalmol 90:1242-1244

Stoutenbeek R, Voogd S de, Wolfs RCW, Hofman A, Jong PTVM de, Jansonius NM (2008) The additional yield of a periodic screening programme for open-angle glaucoma: a population-based comparison of incident glaucoma cases detected in regular ophthalmic care with cases detected during screening. Br J Ophthalmol 92:1222-1226

Vries MM de, Stoutenbeek R, Müskens RPHM, Jansonius NM (2012) Glaucoma screening during regular optician visits: the feasibility and specificity of screening in real life. Acta Ophthalmol Scand 90:115-121

 

7. Motion detection in glaucoma 

 Glaucoma is a chronic eye disease, which eventually can lead to irreversible blindness. In the earlier stages, striking abnormalities may be found in the relevant eye tissues (optic nerve head, retinal nerve fiber layer, retinal ganglion cell layer) apparently without functional changes, at least if tested with straightforward perimetry. This suggests that we overlook or underestimate malfunction of specific visual functions in glaucoma patients. One of these functions could be motion detection. When measuring illusory movement, a psychophysical phenomenon (Jansonius et al. 2014), in glaucoma patients, we found a clearly increased movement threshold. This is in agreement with earlier studies in this field (Shabana et al. 2003). However, much is still to be clarified. In this project we will make an inventory of psychophysical experiments directed towards motion detection that (1) are likely to be able to discriminate between glaucoma patients and healthy controls and (2) can be modified in such a way that they are easy to perform by glaucoma patients and (other) elderly subjects. The gained knowledge will serve as a basis for the development of better functional testing (discriminating between healthy and glaucoma and progression monitoring in established glaucoma) and rehabilitation. Also, treatment decisions can be optimized by an improved understanding of the disability caused by the disease in various stages. In a companion project, motion detection in glaucoma will be studied using neuro-imaging techniques based on results obtained in this project.

PhD Candidate

Lorenzo Scanferla (MScR Integrative Neuroscience)

Supervision

Prof. Nomdo Jansonius (www.nomdo.nl/research.htm)

Prof. Frans W. Cornelissen (www.visualneuroscience.nl)

 References

Jansonius NM, Stam L, Jong T de, Pijpker, BA (2014) Quantitative analysis of illusory movement: spatial filtering and line localization in the human visual system. Perception 43:1329-1340

Shabana N, Cornilleau Peres V, Carkeet A, Chew PT. Motion perception in glaucoma patients: a review. Surv Ophthalmol. 2003; 48:92-106.

 

8. Light adaptation in glaucoma 8

The human visual system is able to function over an extremely wide range of light intensities, and adapts rapidly to a new light level. Both the range and the adaptation speed appear to be disturbed in glaucoma – as we recently discovered in a large questionnaire study performed amongst glaucoma patients and age-matched healthy controls. From a physiological point of view, adaptation consist of a series of processes located in the retina in the photoreceptors (pigment depletion and regeneration, cellular adaptation, and response saturation), the horizontal cells (lateral inhibition), and the amacrine cells (contrast gain control and contrast adaptation). In this project, we aim to unravel the influence of glaucoma on adaptation, by systematically addressing all the abovementioned processes in psychophysical experiments, to be performed by glaucoma patients and healthy subjects. The gained knowledge will serve as a basis for the development of better functional testing (discriminating between healthy and glaucoma and progression monitoring in established glaucoma) and rehabilitation. Also, treatment decisions can be optimized by an improved understanding of the disability caused by the disease in various stages.

PhD Candidate

Catarina A.R. João (MSc Biomedical Technology – Instrumentation and Medical Signals)

Supervision

Prof. Nomdo Jansonius (www.nomdo.nl/research.htm)

Dr. Frans W. Cornelissen (www.visualneuroscience.nl)

References

Meister M, Berry MJ (1999) The neural code of the retina. Neuron 22:435-450

Shapley R, Enroth-Cugell C (1984) Visual adaptation and retinal gain controls. Progress in retinal research 3:263-346

Snippe HP, Poot L, van Hateren JH (2000) A temporal model for early vision that explains detection thresholds for light pulses on flickering backgrounds. Visual Neuroscience 17:449-462

Valeton JM, van Norren D (1983) Light adaptation of primate cones: an analysis based on extracellular data. Vision Research 23:1539-1547

 

9. Using virtual reality to assess visual fields and rehabilitate visual and cognitive functioning 9

Visual information processing is affected in a wide variety of ophthalmic and neurological disorders – many with an age-related component. Such problems can be due to reductions in visual sensitivity as well as cognition (attention). One of the most widely used tests for assessing visual information processing is visual field analysis (perimetry). Current perimetry tests, however, have serious limitations for some groups. Besides their high costs, they are time-consuming and require well-trained operators. Moreover, measurements are attentionally demanding, and difficult to perform in certain patient-groups. Easily deployable and low-cost 3D virtual reality (VR) systems with integrated eye-tracking are about to come to the market (1). While primarily marketed for gaming, these devices open-up a wide array of possibilities for easy, frequent and non-intrusive screening of ophthalmic and neurological diseases based on a person’s eye-movements (saccades and fixations). In this study, we will collect eye-tracking data while subjects are freely viewing a simulated (and thus highly controllable) environment (e.g. a simulated daily life activity such as driving or shopping (see figure). We will compare eye movement behavior of patients and controls using an advanced gaze analysis algorithm based on priority analysis (2). The first goal is to use this approach to efficiently and effortlessly detect visual field defects (for which there is preliminary evidence (3), as well as assess problems with visual processing at a cognitive (attentional) level. The second goal is to use these new devices to enable safe, enjoyable and effective visual rehabilitation. The final goals of this approach is to use it in combination with visual field simulations (4) to provide insight to family members or care-takers. To demonstrate the latter two, we will develop and employ a VR-based object collision avoidance paradigm for use in visual rehabilitation.

PhD Candidate

Birte Gestefeld

Supervision

Prof. Frans W. Cornelissen (www.visualneuroscience.nl)

Prof. Nomdo Jansonius (www.nomdo.nl/research.htm)

References

1. E.g., www.getfove.com

2. Marsman, Cornelissen, Dorr, Vig, Barth, Renken. A novel measure to determine viewing priority and its neural correlates in the human brain. Manuscript submitted (pre-print available on request).

3. Crabb DP, Smith ND and Zhu H (2014) What’s on TV? Detecting age-related neurodegenerative eye disease using eye movement scanpaths. Front. Aging Neurosci. 6:312. doi: 10.3389/fnagi.2014.00312

4. Cornelissen FW, Bruin KJ, Kooijman AC. (2005). The influence of artificial scotomas on eye movements during visual search. Optom Vis Sci. 2005 Jan;82(1):27-35.

5. Tant ML, Cornelissen FW, Kooijman AC, Brouwer WH. (2002). Hemianopic visual field defects elicit hemianopic scanning. Vision Res. 2002 May;42(10):1339-48.

 

10. Resting-state fMRI in glaucoma subjects 

10

An outstanding issue is whether glaucoma should be considered exclusively an eye disease or also a brain disease. To resolve this, we will examine the brains and visual pathways of primary open angle glaucoma (POAG) and normal-tension (NTG) glaucoma patients using resting-state (RS) fMRI. In NTG, optic nerve damage occurs in the absence of the elevated eye pressure that characterizes the more common POAG, in which it causes retinal ganglion cell (RCG) death. In particular, we will be looking for the presence of neurodegeneration of the brain beyond what can be explained on the basis of propagated retinal and optic nerve damage. If we can demonstrate this, it implies glaucoma should also be considered a brain disease with potential repercussions for treatment. Using RS-fMRI, we will examine and compare spontaneous activity both in and outside the lesion projection zone in visual cortex. In the absence of visual input, such activity is shaped by the underlying neural architecture while still reflecting visuotopic organization [1]. RS-data has the important advantage that it is not potentially “contaminated” by BOLD flow artifacts coming from normal functioning sections of cortex. In connection with conventional retinotopy to outline the different visual cortical areas, we expect these examinations can provide very precise information on the integrity of the visual cortex in these patient groups. We will use fMRI analysis techniques such as population Receptive Field and Connective Field analysis [2,3]. Further development of such analysis techniques (e.g. based on phase synchronization) to assess (RS) fMRI data is also foreseen. In combination with eye-tracking, we intend to also test the hypothesis that fixation stability is correlated with the integrity of the visual cortex [4].

PhD Candidate

Azzurra Invernizzi (MSc Biomedical Engineering)

Supervision

Prof. Frans W. Cornelissen (www.visualneuroscience.nl)

Dr. Remco Renken

Prof. Nomdo Jansonius (www.nomdo.nl/research.htm)

References

1. Gravel, N., Harvey, B., Nordhjem, B., & Haak, K. V. (2014). Cortical connective field estimates from resting state fMRI activity. Front. Neurosci. Brain Imaging Methods. http://doi.org/10.3389/fnins.2014.00339

2. Dumoulin, S. O., & Wandell, B. A. (2008). Population receptive field estimates in human visual cortex. NeuroImage, 39(2), 647–660. http://doi.org/10.1016/j.neuroimage.2007.09.034

3. Haak, K. V., Winawer, J., Harvey, B. M., Renken, R., Dumoulin, S. O., Wandell, B. A., & Cornelissen, F. W. (2013). Connective field modeling. NeuroImage, 66, 1–9. http://doi.org/doi:10.1016/j.neuroimage.2012.10.037

4. Haak, K. V., Morland A.B. Rubin G.S. & Cornelissen, F. W. (2015). Preserved retinotopic brain connectivity in macular degeneration. (under review, manuscript available upon request).