Ocular Motor Cranial Nerve Palsy as an Indicator of Neglected Systemic Disease in Nigeria: Perspective from a Neuro-Ophthalmology Clinic.

The aim of this article from Nigeria is to draw attention to public health issues in medical care using ocular motor cranial nerve palsy (OMCNP) presenting to a neuro-ophthalmology clinic as a case study. All patients presenting with OMCNP between November 2007 and October 2016 were retrospectively reviewed. Demographic details as well as information regarding the clinical presentation, clinical course, investigation, and treatment outcomes were extracted from case records. Phone calls were made to the contact numbers of patients who had been lost to follow-up. Data were analysed using SPSS version 22 (IBM, Corp. Armonk, NY, USA). Cranial nerve palsies other than oculomotor, trochlear, and abducens palsies were excluded. Fifty-nine patients, comprising 28 males and 31 females, were identified. Age range was 1-84 years (median 43.0 ± 19.7 years). Fifty-one cases (93.2%) were mono neuropathies, while four (6.8%) affected multiple nerves. Oculomotor nerve palsy was most common, accounting for 57.6% of cases. Microvascular angiopathy was the commonest identifiable cause (25.6%). Aetiology was not identified in 16 cases. There were three (5.1%) deaths. Undiagnosed systemic disease appears to be a major risk factor for this patient group in this African setting. Patient investigation was problematic. Poor patient compliance and follow-up resulted in preventable deaths. Neuro-ophthalmologists practicing in low resource settings should be aware of these risks.

Prevalence of congenital colour vision deficiency among secondary school students in Ibadan, South-West Nigeria.

AIM: The aim was to determine the prevalence and pattern of congenital colour vision deficiency among secondary school students in Ibadan, Nigeria. SUBJECTS AND METHODS: A descriptive cross-sectional study was conducted among students from three public secondary schools through a multi-staged sampling method. Ocular examination including visual acuity assessment and colour vision test with the Ishihara plate was performed for all students. Further assessment with the Farnsworth-Munsell D-15 panel was performed for those who failed the Ishihara test. RESULTS: One thousand six hundred and thirty-five students participated in the study. There were 769 (47.0%) males with mean age of 13.9 ± 1.9 years. The overall prevalence of congenital colour vision deficiency was 2.3% with prevalence of 3.8% and 0.9% in males and females, respectively, which was statistically significant (P = 0.00112), and equal proportion of deutans 11 (32.0%) and protans 12 (35.0%) ratio of 1:1.1. CONCLUSION: The prevalence of congenital colour vision deficiency among public secondary school students in Ibadan is comparable to findings in other parts of the country.

A prospective registry study of the epidemiology and management of childhood cancer in the Gambia-The first year experience.

Background and Aim: Globally, over 180,000 children develop cancers yearly, with about 80% residing in low- or middle-income countries where cancer-associated mortality is also high. In The Gambia, cumulative incidence rate of 27.6 childhood cancers/million population was reported between 2002 and 2011. The current study appraised newly-established pediatric oncological services in The Gambia. Methods: In this prospective registry study, children with cancer who presented at the pediatric units, Edward Francis Small Teaching Hospital, Banjul, between November 2022 and October 2023 were assessed. Data on sociodemographic variables, mode of admission and presentation, tumor type, diagnostic methods, and challenges such as laboratory support, treatment, use of blood/blood products; and eventual outcome were analyzed. Results: The median (interquartile range, IQR) age at presentation of the 44 children was 36.0 (22.3-117.0) months. Wilms tumor was the most common tumor 12 (27.3%); followed by leukemia 11 (25.0%); germ cell tumor 8 (18.2%); lymphoma 6 (13.6%); retinoblastoma 4 (9.1%); rhabdomyosarcoma 2 (4.5%) and one central nervous system tumor (2.3%). The median(IQR) duration of symptoms before presentation was 48 (21-90) days, presentation to diagnosis 7.5 (3-20.8) days, and first symptom to diagnosis 62.5 (32-126.8) days. Treatment refusal and abandonment rates were 20.5% and 13.6%, respectively. Families of 93.8% of children could not procure cytotoxic drugs due to nonavailability, high cost, or both. Adequate laboratory monitoring was only available in 6.8%, and none had platelet concentrate transfusion or radiotherapy. The nine (20.5%) who completed treatment are currently being followed up, 10(22.7%) are still receiving chemotherapy, while 2(4.5%) were referred. Eight (18.2%) died, predominantly from metastasis (75%) and severe drug toxicities (25%). Conclusion: Late presentation and diagnosis, poverty, unavailability of drugs, suboptimal or lack of laboratory testing, blood product, adjuvant medications, and psychosocial supports contributed to high treatment refusal, abandonment, and mortality. These daunting challenges can be ameliorated with regular community sensitization, frequent cancer auditing, and strong political will.

X-linked cone dystrophy caused by mutation of the red and green cone opsins.

X-linked cone and cone-rod dystrophies (XLCOD and XLCORD) are a heterogeneous group of progressive disorders that solely or primarily affect cone photoreceptors. Mutations in exon ORF15 of the RPGR gene are the most common underlying cause. In a previous study, we excluded RPGR exon ORF15 in some families with XLCOD. Here, we report genetic mapping of XLCOD to Xq26.1-qter. A significant LOD score was detected with marker DXS8045 (Z(max) = 2.41 [theta = 0.0]). The disease locus encompasses the cone opsin gene array on Xq28. Analysis of the array revealed a missense mutation (c. 529T>C [p. W177R]) in exon 3 of both the long-wavelength-sensitive (LW, red) and medium-wavelength-sensitive (MW, green) cone opsin genes that segregated with disease. Both exon 3 sequences were identical and were derived from the MW gene as a result of gene conversion. The amino acid W177 is highly conserved in visual and nonvisual opsins across species. We show that W177R in MW opsin and the equivalent W161R mutation in rod opsin result in protein misfolding and retention in the endoplasmic reticulum. We also demonstrate that W177R misfolding, unlike the P23H mutation in rod opsin that causes retinitis pigmentosa, is not rescued by treatment with the pharmacological chaperone 9-cis-retinal. Mutations in the LW/MW cone opsin gene array can, therefore, lead to a spectrum of disease, ranging from color blindness to progressive cone dystrophy (XLCOD5).

Central Retinal and Ophthalmic Artery Doppler Velocimetry among Hypertensives and Normotensive Adults at a Nigerian Tertiary Health Facility.

Background: Haemodynamic alterations of the retrobulbar circulation are sequelae of untreated, long-standing hypertension. Early evaluation of the retrobulbar blood flow is very crucial to prevent irreversible ocular complications. The objective of this study was to evaluate the differences in central retinal artery (CRA) and ophthalmic artery (OA) haemodynamics in adult hypertensive and non-hypertensive subjects. Methodology: This prospective, comparative cross-sectional study was conducted among 63 hypertensives and 75 normotensive controls. Using Doppler ultrasonography, the CRA and OA Doppler velocimetry parameters among cases and controls were evaluated and analysed. Results: The CRA Peak Systolic Velocity (PSV) and End-diastolic velocity (EDV) was 7.54 ± 2.60cm/s and 2.99 ± 1.15cm/s (p<0.001) in hypertensives but 10.8 ± 2.51cm/s and 4.50 ± 1.25cm/s) p<0.001 in controls. The systolic/diastolic ratio (S/D) in cases was 2.64 ± 0.75 and 2.44 ± 0.38 p=0.045 in controls. The CRA's Pulsatility Index (PI) between cases and controls was not statistically significant, p =0.082. Furthermore, the CRA's PSV, PI, Resistivity index (RI) and S/D, were higher among subjects with stage 1 compared to stage 2 hypertension (p=0.004; p=0.027; p<0.001 and p=0.001 respectively). The OA mean EDV in hypertensives was 4.57 ± 1.97 and in controls= 5.31 ± 1.79 (p=0.022), while the OA mean RI and Peak Ratio, p=0.009 and 0.003, respectively, were higher in stage 1 hypertension. Conclusion: The Central retinal and ophthalmic artery blood flow parameters were significantly lower among hypertensive cases. Also, hypertensive stage 2 cases had significantly lower blood flow and vascular impedance parameters in the CRA and both Central retinal and ophthalmic artery, respectively.

Does enzyme replacement therapy influence the ocular changes in type VI mucopolysaccharidosis?

BACKGROUND: To describe the ocular changes noted in seven patients with type VI mucopolysaccharidosis (MPS VI) during 44 months of follow-up while on enzyme replacement therapy (ERT). METHODS: One male and six female patients with MPS VI were followed-up for a mean period of 44 months while undergoing enzyme replacement therapy (ERT) with recombinant arylsulfatase B (Naglazyme). They were examined annually for visual acuity, corneal clouding, intraocular pressure (IOP), optic nerve head and fundus morphology. Corneal clouding was documented by photography. We acknowledge that our methodology may not have been sensitive enough to detect extremely mild ocular changes, including minimal increases in corneal thickness or clouding. Nevertheless, this limitation has been considered in the interpretation of our findings. RESULTS: Ophthalmological findings remained stable in 5/7 patients. One patient experienced a modest improvement in visual acuity of more than 2 Snellen lines in one eye, while another patient suffered a deterioration in visual acuity of more than 2 Snellen lines in both eyes. Five out of seven patients showed optic nerve pathology: two of these exhibited optic nerve head swelling, while the other three showed variable degrees of optic nerve atrophy. All seven patients suffered from the typical corneal stromal opacities, however, to variable extents. CONCLUSION: Visual function and ocular findings did not deteriorate in six out of seven MPS VI patients during a mean follow-up period of 3 and a half years on ERT.

Intraepithelial and invasive squamous neoplasms of the conjunctiva in Ibadan, Nigeria: a clinicopathological study of 46 cases.

BACKGROUND/AIMS: To retrospectively evaluate the clinicopathological features, treatment modalities and factors affecting prognosis in patients with both conjunctival intraepithelial and invasive squamous neoplasms. METHOD: Review and analysis of clinical and pathological records of all cases histologically diagnosed in the Department of Pathology, University College Hospital, Ibadan, Nigeria between January 1990 and December 2004. RESULTS: There were a total of 46 cases in 45 patients (eight intraepithelial carcinomas, 37 invasive squamous cell carcinomas (SCC) and a single case of mucoepidermoid carcinoma in a 71-year-old man). The intraepithelial neoplasms occurred in patients aged between 20 and 90 years. Seven of these patients had actinic changes on histology. For invasive SCC, patients' ages ranged from 18 to 84 years with a mean age of 53 years. Male to female ratio was 1:1. The majority presented with an orbital mass and loss of vision. Twenty-two (60%) of the patients with invasive SCC had enucleation or exenteration as the primary modality of treatment with or without radiotherapy or chemotherapy. Altogether for intraepithelial and invasive squamous neoplasms, the duration of presenting complaints ranged from 1 month to 5 years with an average of 2 years. Human immunodeficiency virus (HIV) infection and smoking were not significantly associated with these cases but a significant number had outdoor occupation. Low socioeconomic status and inability to afford treatment was common among our patients. CONCLUSION: Patients with invasive SCC in Nigeria present late and have significant delay before having any form of treatment. This contributes to the poor outcome. Human papilloma virus (HPV) and actinic aetiology are possible strong causative agents in Nigerians.

Students' perceptions of the learning environment in two Nigerian medical schools offering different curricula.

OBJECTIVE: Compare the results of administering the DREEM questionnaire in two Nigerian medical schools offering traditional and student-centred curricular respectively, to identify any differences in the learning environment and appreciate advantages of the more modern curriculum. METHODS: A survey design was used. Data was analysed using the DREEM scoring rubric. The independent t-test was used to compare results. SETTING: The DREEM questionnaire was administered to final year medical students at two participating centres. PARTICIPANTS: Final year students of a teacher-centred and a student-centred medical school. RESULTS: There were 138 respondents - 50 (96.2% of the final year students) from the teacher centred school and 88 (59.1% of the final year students) from the student-centred school. The mean total DREEM score was 117+22.3 in the former and 119 +23.6 in the latter (p = 0.798). Mean age of students in the teacher centred school was 28 ± 5.28 years, while that of the student-centred school was 23 ± 1.83 years (p < 0.05). CONCLUSION: The mean total DREEM score proximity between the schools suggests that the younger students using a more student-centred curriculum have less of an appreciation of their improved learning environment than is expected. Thus, the hidden curriculum could be lagging behind the written one. The older students in the teacher centred environment have a more mature appreciation of their learning climate. FUNDING: Personal sources.

Ocular changes in patients with mucopolysaccharidosis I receiving enzyme replacement therapy: a 4-year experience.

OBJECTIVE: To describe the progression of ocular changes in patients with mucopolysaccharidosis I receiving enzyme replacement therapy. METHODS: Three male and five female patients with mucopolysaccharidosis I were followed up for 4 years while undergoing enzyme replacement therapy with alpha-l-iduronidase (Aldurazyme). Visual acuity, corneal clouding, intraocular pressure, ophthalmoscopy, and optic disc measurements were performed yearly. RESULTS: Vision remained stable in 5 patients and deteriorated by at least 2 Snellen lines in 3 patients. Deterioration in 2 of these patients was related to progressive corneal clouding. Visual acuities improved in 1 patient after bilateral penetrating keratoplasties. In the third patient, deterioration was related to increasing papilloedema. All patients had typical corneal stromal opacities, however, to a variable extent. Two patients had already undergone corneal transplantation before recruitment in the study. Their grafts remained clear throughout follow-up. Of 2 patients with an elevated intraocular pressure, 1 developed intraocular pressure-related optic nerve damage. Vision remained stable in a patient with bilateral optic atrophy. CONCLUSIONS: Ocular findings remain stable in most patients with mucopolysaccharidosis I receiving enzyme replacement therapy. However, enzyme replacement therapy does not seem to prevent progression of corneal or optic disc changes and, thus, the related worsening of visual function.

Encouraging Subspecialty Practice by Constructively Influencing Trainees Early in their Careers Will Improve Advocacy for Neuro-Ophthalmology among Nigerian Ophthalmologists.

This study was conducted to assess the current knowledge, attitude, and perception of Nigerian ophthalmologists toward neuro-ophthalmology; identify barriers to the uptake of neuro-ophthalmology as a desired subspecialty; and make recommendations to improve interest in neuro-ophthalmology training. This was a cross-sectional survey of ophthalmology consultants and trainees from the six geopolitical zones of Nigeria, who were attending a national ophthalmology conference. All consenting respondents voluntarily completed a validated self-administered questionnaire. There were 107 respondents comprising 56 males and 51 females. Majority (54.2%) of respondents were aged 40 years and younger. Almost half (47.8%) worked at tertiary level, public health institutions. Only 10.3% worked in private practice. Neuro-ophthalmology exposure was short and occurred mainly during residency (65.7%), while 15% had no exposure at all. Most (80.4%) indicated only nominal interest in neuro-ophthalmology, while only 4.6% indicated a desire to specialize in the field. Financial constraint was the main obstacle to the pursuit of subspecialty training. A total of 86% of respondents admitted that full (34%) or partial (52%) Funding would motivate them to pursue the training. Among respondents desiring part sponsorship, more than half were willing to augment such sponsorship with personal funds. In conclusion, career interest in neuro-ophthalmology is very low among Nigerian ophthalmologists. Late and limited exposure to neuro-ophthalmology during medical training may be contributing factors. Early exposure to neuro-ophthalmology during medical school rotations, coupled with the provision of sponsored subspecialty training opportunities, will serve to increase enrollment in the field.

Severe Ophthalmological Complications of Thyroid Disease are Rare in Ibadan, Southwestern Nigeria: Results of a Pilot Study.

BACKGROUND: Ocular manifestations of thyroid dysfunction constitute a wide clinical spectrum ranging from minor ocular discomfort, lid retraction, lid lag and ocular injection, to sight threatening eyeball protusion and optic nerve compression. Thyroid-related eye disorders are most commonly associated with Graves' disease, and this most frequently occurs in the setting of hyperthyroidism. However, in 10% of cases, typical eye signs have also been reported in euthyroid and hypothyroid states. The severity of thyroid eye disease has been linked to cigarette smoking. There is very little data specifically reporting the ocular manifestations of thyroid disease among black African patients and there is no known report from Nigeria. This pilot study therefore focused on documenting the ocular signs accompanying thyroid dysfunction in a black African population. AIM: To evaluate the pattern of ocular complications, among patients treated for thyroid disorders, in a major Nigerian teaching hospital. RESULTS: A total of 75 patients with thyroid dysfunction, were evaluated, comprising 63 females and 12 males. There was a very low prevalence of smoking among patients (<5%). Graves' disease was the commonest thyroid disorder, representing 70% of cases. Seventy-eight percent of patients were hyperthyroid, 11.8% were euthyroid and only 9.8% of patients were hypothyroid. Commonest systemic symptoms were neck swelling (68.6%), weight loss (63.8%), tremors (60.9%) and palpitations (59.4%). Two-thirds of patients reported ocular symptoms consisting mainly of painless eye swelling (66.7%) and ocular irritation (58%). Conjunctival injection, lid lag and lid retraction were the commonest ocular signs. Chemosis, severe proptosis and ocular motility disorder were very rare. Optic neuropathy was found in 4 patients but was related to pre-existing glaucoma. Majority of patients required only ocular emollients and tear supplements. CONCLUSION: Severe ocular complications of thyroid disorders were uncommon in this cross-section of Nigerian patients. This may be linked to the very low prevalence of cigarette smoking among Nigerians or genetic and environmental factors linked to their African heritage.

Central nervous system tumours in children in Ibadan, Nigeria: a histopathologic study.

INTRODUCTION: Contrary to some earlier teachings that central nervous system (CNS) tumours are uncommon in black children, these neoplasms are the fourth most common paediatric tumours in Ibadan. Our centre is the major referral centre for CNS tumours in Nigeria. The last major study of paediatric CNS neoplasms from Ibadan was in 1985. An update of the data on paediatric CNS neoplasms at our centre is presented. METHODS: A retrospective review of all histologically diagnosed CNS tumours in children (0-14 years) from January 2001 to December 2010 from the database of the Department of Pathology, University College Hospital, Ibadan, Nigeria was done. The cases were classified using the 2007 WHO Classification of Tumours of the Central Nervous System and were also based on their supratentorial and infratentorial locations. RESULTS: Seventy-seven tumours, 44 in males, were included in the study. Astrocytic tumour comprised 20 cases, embryonal tumours 15, ependymal tumours 15, germ cell tumours 6, sellar tumours (all craniopharyngiomas) 9 and other histological types- 12 cases. Thirty-seven were WHO Grade 1, eleven Grade 2, ten Grade 3 and nineteen Grade 4 neoplasms. Thirty-six cases were supratentorial and thirty-eight were infratentorial in location. The most common tumours in this series were pilocytic astrocytomas, medulloblastomas, craniopharyngiomas and ependymomas in that order. CONCLUSION: Childhood CNS tumours are being increasingly diagnosed in our centre. This is largely explained by the recent expansion of the available neurosurgical services.

Role of Diffusion-weighted Imaging in Acute Stroke Management using Low-field Magnetic Resonance Imaging in Resource-limited Settings.

A variety of imaging modalities exist for the diagnosis of stroke. Several studies have been carried out to ascertain their contribution to the management of acute stroke and to compare the benefits and limitations of each modality. Diffusion-weighted imaging (DWI) has been described as the optimal imaging technique for diagnosing acute ischemic stroke, yet limited evidence is available on the value of DWI in the management of ischemic stroke with low-field magnetic resonance (MR) systems. Although high-field MR imaging (MRI) is desirable for DWI, low-field scanners provide an acceptable clinical compromise which is of importance to developing countries posed with the challenge of limited availability of high-field units. The purpose of this paper was to systematically review the literature on the usefulness of DWI in acute stroke management with low-field MRI scanners and present the experience in Nigeria.

ROLE OF TRANSCRANIAL COLOUR-CODED DUPLEX SONOGRAPHY IN STROKE MANAGEMENT - REVIEW ARTICLE.

The development of transcranial colour-coded duplex sonography (TCCS) has resurrected the hope of safe, real time bedside brain imaging beyond childhood. This review article provides an overview of the role of TCCS in the management of patients with stroke. The objective is to stimulate interest in the field of neurosonology as a potential means of improving neurological outcome for stroke patients and a area for stroke research endeavors in Africa. Literature search was done on MEDLINE, Cochrane library, and Google Scholar databases with the following keywords: transcranial colour Doppler, Transcranial duplex sonography, transcranial colour-coded Doppler sonography, stroke, infarct and haemorrhage. We also identified relevant articles from the references section of studies produced by our literature search. We discussed the roles of TCCS to discriminate ischaemic from haemorrhagic forms; unravel the mechanism of stroke; monitor temporal evolution of stroke and predictors of stroke outcome; and promote better understanding of the epidemiology of stroke. Its emerging role as a potent point-of-care imaging modality for definitive treatment in ischaemic stroke within and outside the hospital setting is also highlighted. Comparison of TCCS with alternative modalities for neuroimaging in stroke is also discussed. A root cause analysis of the untenable high cost of neuroimaging for stroke patients in Africa is presented vis-à-vis the potential economic relief which widespread adoption of TCCS may provide. We advocate capacity building for TCCS and suggest some action plans required to achieve safe, cheap, affordable and reliable ultrasound based neuroimaging for stroke patients in resource limited areas of Africa.

Rethinking airbag safety: airbag injury causing bilateral blindness.

A healthy 40-year-old man, restrained in the front passenger seat, suffered visually disabling blunt ocular trauma following spontaneous release of the passenger side air-bag module, during vehicular deceleration, without an automobile crash. Though the driver-side airbag was also released, the driver was unharmed. The passenger suffered bilateral hyphema, bilateral vitreous hemorrhage and suspected posterior scleral rupture in the left eye and also had an eyebrow laceration, from impact with the dashboard panel covering the air-bag module, which was detached by the force of airbag deployment. This is the first reported case from West Africa and the first case in which part of the airbag module detached to cause additional trauma. This report adds to the growing burden of evidence world-wide, for a review of the safety aspects of the automobile airbag. This case clearly illustrates that although airbags reduce mortality, they carry a high risk of ocular morbidity, even with seat belt restraint.

Evaluating the potentiating effect of amethocaine on tropicamide-induced mydriasis in darkly pigmented irides, using infrared pupillometry.

PURPOSE: To determine whether prior instillation of amethocaine would increase the rate and magnitude of tropicamide-induced pupillary dilatation in darkly pigmented irides. METHOD: A total of 50 healthy Africans aged 18-40 years, with darkly pigmented irides, received a drop of amethocaine in one eye and a drop of placebo in the contralateral eye, followed by two drops of tropicamide in both eyes. Serial pupil diameters were measured using a monocular infrared video pupillometer. Rate of pupillary dilatation was compared in both eyes. Survival statistics were calculated for the time taken to reach a clinically effective dilatation, clinically effective diameter (CED) of 6.0 mm. RESULTS: Mean difference in pupil diameters between amethocaine- and placebo-treated eyes was 0.30 ± 0.09 mm (P < 0.002). In all, 62% of amethocaine-treated eyes and only 46% of placebo-treated eyes reached the CED. CONCLUSION: We observed a small but statistically significant potentiating effect of a drop of amethocaine on tropicamide-induced dilatation within 20 minutes.

Congenital orbital teratoma: a case report and challenges of its management in a resource limited setting.

We report a case of congenital immature teratoma of the orbit in a female neonate who presented on the second day of life. She was successfully managed by modified exenteration. The patient was lost to follow-up intermittently over a 24-month period without recurrence of the tumour. However the patient could not be traced again after 24 months of follow up. This happened despite concerted efforts to educate the parents. The possible implications of this and other social factors, in a challenging and resource limited setting, on the prognosis of the disease and cosmetic outcome are considered.

The effect of central (macula) sparing on contralateral line bisection bias: a study with virtual hemianopia.

Hemianopic patients show a contralesional bisection bias, but it is unclear whether this is a consequence of their field loss or related to extrastriate damage. One observation cited against the former is that hemianopic bisection bias does not vary with the degree of central (macular) sparing; however, it is unclear to what extent central sparing should affect this bias. Our goal was to determine the effect of central sparing on line bisection biases from field loss alone, with two approaches. First, we studied 12 healthy subjects viewing lines under conditions of virtual hemianopia, created by a gaze-contingent technique. Second, we calculated the effect predicted by a visuospatial model of the effect of central magnification on line representations in the visual system. Our results first replicated the contralateral line bisection bias with hemianopia, confirming that this can be generated by visual hemifield loss in the absence of extrastriate damage. Central sparing had only a modest effect on hemianopic bisection bias, with only slightly less bias with 10° compared to 2° of central sparing. In accordance with these empiric data, computing the center of mass for line representations in our model showed only a shallow decline in bisection bias as central sparing increased from 0 to 10°. We conclude that contralateral bisection bias only decreases slightly with central sparing, and that the absence of a statistically significant effect of central sparing in patients cannot be taken as evidence against a visual origin of contralateral hemianopic line bisection bias.