The relationship between word length and threshold character size in patients with central scotoma and eccentric fixation

BACKGROUND

Understanding limitations on text reading with eccentric fixation is of major concern in low vision research. Our objective was to determine, in patients with a central scotoma, whether threshold character size is similar for different word lengths and paragraphed texts.

METHODS

In 19 patients, we retrospectively analyzed the relationship between minimum readable character size for isolated words and text. Isolated letters, two, five, and ten-letter words and a paragraphed text were presented randomly through a scanning laser ophthalmoscope in eight different character sizes.

RESULTS

Threshold character size varied according to the text stimulus (p<0.05). Threshold character sizes for single letters and two-letter words were matched (p>0.99), as were those for five-letter words, ten-letter words, and paragraphed text (p>0.99). Threshold character size for single letters and two-letter words was significantly lower than that measured with other text stimuli.

DISCUSSION

Reading performance is influenced by a variety of factors such as crowding, contextual effects, visual span, degree of oculomotor adaptation needed, and frequency of a defined word. Globally, when reading with a central scotoma, it appears that within word characteristics have more impact than inter-word parameters on threshold character size.

Processes Involved in Oculomotor Adaptation to Eccentric Reading

PURPOSE

Adaptation to eccentric viewing in subjects with a central scotoma remains poorly understood. The purpose of this study was to analyze the adaptation stages of oculomotor control to forced eccentric reading in normal subjects.

METHODS

Three normal adults (25.7 +/- 3.8 years of age) were trained to read full-page texts using a restricted 10 degrees x 7 degrees viewing window stabilized at 15 degrees eccentricity (lower visual field). Gaze position was recorded throughout the training period (1 hour per day for approximately 6 weeks).

RESULTS

In the first sessions, eye movements appeared inappropriate for reading, mainly consisting of reflexive vertical (foveating) saccades. In early adaptation phases, both vertical saccade count and amplitude dramatically decreased. Horizontal saccade frequency increased in the first experimental sessions, then slowly decreased after 7 to 15 sessions. Amplitude of horizontal saccades increased with training. Gradually, accurate line jumps appeared, the proportion of progressive saccades increased, and the proportion of regressive saccades decreased. At the end of the learning process, eye movements mainly consisted of horizontal progressions, line jumps, and a few horizontal regressions.

CONCLUSIONS

Two main adaptation phases were distinguished: a "faster" vertical process aimed at suppressing reflexive foveation and a "slower" restructuring of the horizontal eye movement pattern. The vertical phase consisted of a rapid reduction in the number of vertical saccades and a rapid but more progressive adjustment of remaining vertical saccades. The horizontal phase involved the amplitude adjustment of horizontal saccades (mainly progressions) to the text presented and the reduction of regressions required.

Computer-based measurement of letter and word acuity

Determining causes of poor reading ability is an important step in trying to ameliorate reading performance in low-vision patients. One important parameter is word acuity. The principal aim of the current study is to develop a method to reliably measure acuities for isolated lowercase letters and words of differing length that can be used to test low-vision patients. Using isolated stimuli means that testing is relatively free of potential crowding and/or distracting attentional effects from surrounding words, it is unambiguous which stimulus subjects are trying to read and response times can be recorded for each stimulus. Across a series of experiments, subjects with normal vision were asked to read isolated lowercase single letters and lowercase words of 4, 7 and 10 letters, in separate tests. Acuities for uppercase Sloan letters were also measured to provide a reference, as they are commonly used to measure visual acuity. Each test was based upon the design principles and scoring procedures used in the Bailey-Lovie and ETDRS charts. Acuities for uppercase Sloan letters were found to be equivalent whether measured using ETDRS charts or the computer-based method. Measurement of acuities for lowercase single letters and lowercase words of 4, 7 and 10 letters had a reliability that was no worse than acuities for uppercase Sloan letters. Lowercase word acuities were essentially independent of word length. Acuities for single lowercase letters and lowercase words were slightly better than uppercase Sloan letters acuity. Optimal processing of lowercase single letters and 4-, 7- and 10-letter words occurred at character sizes that were at least 0.2-0.40 log MAR above acuity threshold, i.e. between 1.5 and 3 times threshold acuity for that particular stimulus. In general, critical character sizes appear similar across word lengths as progressive increases or decreases in these values were not observed as a function of the number of letters in the stimulus. We conclude that a computer-based method of stimulus presentation can be used to obtain highly repeatable measures of acuity for lowercase single letters and lowercase words in normal vision.

Simulation of Artificial Vision, III: Do the Spatial or Temporal Characteristics of Stimulus Pixelization Really Matter?

PURPOSE

In preceding studies, simulations of artificial vision were used to determine the basic parameters for visual prostheses to restore useful reading abilities. These simulations were based on a simplified procedure to reduce stimuli information content by preprocessing images with a block-averaging algorithm (square pixelization). In the present study, how such a simplified algorithm affects reading performance was examined.

METHODS

Five to six volunteers with normal vision were asked to read full pages of text with a 10 degrees x 7 degrees viewing window stabilized in central vision. In a first experiment, reading performance with off-line and real-time square pixelizations was compared at different resolutions. In a second experiment, off-line square pixelization was compared with off-line Gaussian pixelization with various degrees of overlap. In a third experiment, real-time square pixelization was compared with real-time Gaussian pixelization.

RESULTS

Results from the first experiment showed that real-time square pixelization required approximately 30% less information (pixels) than its off-line counterpart. Results from the second experiment, using off-line processing, revealed a restricted range of Gaussian widths for which performances were equivalent or significantly better than that obtained with square pixelization. The third experiment demonstrated, however, that reading performances were similar in both real-time pixelization conditions.

CONCLUSIONS

This study reveals that real-time stimulus pixelization favors reading performance. Performance gains were moderate, however, and did not allow for a significant (e.g., twofold) reduction of the minimum resolution (400-500 pixels) needed to achieve useful reading abilities.

Visual recovery after perinatal stroke evidenced by functional and diffusion MRI: case report

BACKGROUND

After perinatal brain injury, clinico-anatomic correlations of functional deficits and brain plasticity remain difficult to evaluate clinically in the young infant. Thus, new non-invasive methods capable of early functional diagnosis are needed in young infants.

CASE PRESENTATION

The visual system recovery in an infant with perinatal stroke is assessed by combining diffusion tensor imaging (DTI) and event-related functional MRI (ER-fMRI). All experiments were done at 1.5T. A first DTI experiment was performed at 12 months of age. At 20 months of age, a second DTI experiment was performed and combined with an ER-fMRI experiment with visual stimuli (2 Hz visual flash). At 20 months of age, ER-fMRI showed significant negative activation in the visual cortex of the injured left hemisphere that was not previously observed in the same infant. DTI maps suggest recovery of the optic radiation in the vicinity of the lesion. Optic radiations in the injured hemisphere are more prominent in DTI at 20 months of age than in DTI at 12 months of age.

CONCLUSION

Our data indicate that functional cortical recovery is supported by structural modifications that concern major pathways of the visual system. These neuroimaging findings might contribute to elaborate a pertinent strategy in terms of diagnosis and rehabilitation.

Functional properties of neuronal nicotinic acetylcholine receptors in the chick retina during development

Acetylcholine (ACh) has been recognized for a long time as a major neurotransmitter in the retina, however, little is known about the contribution of acetylcholine receptors in synaptic processing. Moreover, even less information is available concerning their role during development. To address this question further, we examined the physiological and pharmacological properties of neuronal nicotinic acetylcholine receptors (nAChRs) in retinal ganglion cells from embryonic (E) 12-18-day-old Leghorn chicks. Patch-clamp recordings in whole-cell configuration revealed that at E12 approximately 21% of the ganglion cells responded to acetylcholine pulses with inward currents. The number of responsive cells progressively increased to 57% at E15 to reach up to 15 positive cells out of 15 cells tested at E18. Acetylcholine-evoked responses could be subdivided, according to their time course, into fast and slowly desensitizing. Taking advantage of the selectivity of the frog toxin epibatidine (Epi), that preferentially activates heteromeric neuronal nicotinic acetylcholine receptors, we compared the currents evoked by this toxin vs. the effects of acetylcholine. A further characterization of the receptor diversity during development was to assess their sensitivity to the alpha-conotoxin MII (alpha-CTX-MII), which has been shown to preferentially block alpha6- and alpha3beta2-containing receptors. These data demonstrate that ganglion cells of the chick retina express multiple receptor subtypes that progressively develop as a function of retina maturation.

Pasteurella multocida endophthalmitis: case report and review of the literature

BACKGROUND

Postoperative bacterial endophthalmitis is caused by the patient's endogenous flora in most cases (80 %). Pasteurella multocida (PM) is a Gram-negative coccobacillus found in the upper respiratory tract of dogs and cats and is very rarely implicated in postoperative endophthalmitis.

HISTORY AND SIGNS

We describe a case of PM endophthalmitis that developed after cataract surgery.

THERAPY AND OUTCOME

Cultures of both the conjunctiva and the aqueous humor were positive for PM. Topical, intravitreous and intravenous antibiotics were administered. Despite treatment, the outcome was unfavourable and complicated by a corneal perforation.

CONCLUSIONS

The prognosis of postoperative PM endophthalmitis remains poor, despite adequate treatment of the infection. A history of recent pet exposure should alert physicians to this possible aetiological factor.

Varicella-Zoster Virus Retinitis: Successful Evolution with a Combination of Antiviral Therapies

BACKGROUND

We present the description of a successful outcome in a case of varicella-zoster virus (VZV) acute retinal necrosis (ARN).

HISTORY AND SIGNS

A healthy 40-year-old patient was admitted for a VZV retinitis.

THERAPY AND OUTCOME

10 days after the onset of intravenous (i. v.) acyclovir treatment, new small peripheral retinal necrotic lesions appeared in the right eye. A viral resistance was suspected and the acyclovir therapy was optimised with i. v. foscarnet combined with 2 intravitreal injections of ganciclovir. The outcome was favourable with a final vision of 1.0 after a follow-up of 30 months. No systemic or local complications were observed.

CONCLUSIONS

VZV ARN is a severe infection with a poor prognosis. This case demonstrates that combination of antiviral therapies given intravenously (acyclovir + foscarnet) and in the vitreous (ganciclovir) may be safe and efficacious in the management of necrotising herpetic retinopathies affecting immunocompetent patients.

Elicited repetitive daily blindness: a new familial disorder related to migraine and epilepsy

The authors report a family affected by multiple daily episodes of transient visual loss, elicited repetitive daily blindness (ERDB); the onset was early in life, and the disease followed a benign course. ERDB is associated with childhood epilepsy and familial hemiplegic migraine, apparently segregating as a monogenic, autosomal dominant condition with variable expression. Genetic linkage to CACNA1A was excluded.

Development of a viewing strategy during adaptation to an artificial central scotoma

Although many individuals with a central scotoma develop eccentric fixation most often beneath or left of the scotoma, little is known about how they come to develop a particular viewing strategy. We investigated this by asking eight subjects with normal vision to read isolated letters, words and text passages while an artificial scotoma covered a central portion of the visual field. We quantified viewing strategy and analysed changes in their viewing behaviour over 8-10 sessions within a two-week period. Subjects read while either a horizontal (n=4) or vertical bar scotoma (n=4), 10 degrees wide, covered the entire horizontal or vertical meridian of the stimulus field. For the horizontal scotoma group: (1) there was an increasing preference to use the inferior visual field for isolated letters/words and text passages, which was essentially complete within the test period; (2) the superior visual field was preferred when reading letters/words initially presented in upper visual space and the inferior visual field when reading letters/words initially presented in lower visual space; (3) in general, variation in viewing strategy according to stimulus position diminished over the sessions for all stimuli. For the vertical scotoma group: (1) two subjects used the left and right visual fields in approximately equal proportion to view isolated letters/words, one subject showed a weak preference to use the left visual field and one subject developed a strong preference for using the right visual field; (2) the text passages could be read with combined use of left and right visual fields in a specific manner; (3) the left visual field was preferred to view stimuli initially presented in left visual space while the right visual field was preferred for words initially presented in right visual space. This effect diminished across sessions. Overall, these findings indicate that (1) a specific viewing strategy can be developed through as little as 5 hours of reading experience without guided training; (2) two distinctly separate retinal areas can be used in an integrated manner during reading; (4) stimulus position in visual space can influence viewing strategy; (5) in general, reading encourages a preference for the inferior over the superior visual field, but not the left over right visual field. Letter/word/text recognition and reading speeds increased progressively across sessions, even after scotoma lateralisation appeared stabilised suggesting that multiple mechanism are involved in adaptive changes.

Simulation of artificial vision: II. Eccentric reading of full-page text and the learning of this task

Reading of isolated words in conditions mimicking artificial vision has been found to be a difficult but feasible task. In particular at relatively high eccentricities, a significant adaptation process was required to reach optimal performances [Vision Res. 43 (2003) 269]. The present study addressed the task of full-page reading, including page navigation under control of subject's own eye movements. Conditions of artificial vision mimicking a retinal implant were simulated by projecting stimuli with reduced information content (lines of pixelised text) onto a restricted and eccentric area of the retina. Three subjects, naïve to the task, were trained for almost two months (about 1 h/day) to read full-page texts. Subjects had to use their own eye movements to displace a 10 degrees x 7 degrees viewing window, stabilised at 15 degrees eccentricity in their lower visual field. Initial reading scores were very low for two subjects (about 13% correctly read words), and astonishingly high for the third subject (86% correctly read words). However, all of them significantly improved their performance with time, reaching close to perfect reading scores (ranging from 86% to 98% correct) at the end of the training process. Reading rates were as low as 1-5 words/min at the beginning of the experiment and increased significantly with time to 14-28 words/min. Qualitative text understanding was also estimated. We observed that reading scores of at least 85% correct were necessary to achieve 'good' text understanding. Gaze position recordings, made during the experimental sessions, demonstrated that the control of eye movements, especially the suppression of reflexive vertical saccades, constituted an important part of the overall adaptive learning process. Taken together, these results suggest that retinal implants might restore full-page text reading abilities to blind patients. About 600 stimulation contacts, distributed on an implant surface of 3 x 2 mm2, appear to be a minimum to allow for useful reading performance. A significant learning process will however be required to reach optimal performance with such devices, especially if they have to be placed outside the foveal area.

[The value of multifocal ERG in diagnosis of discrete macular dystrophies]

BACKGROUND

Multifocal ERG is being extensively applied to numerous retinal disorders. It has gained particular clinical value in retinal disorders developing without morphological alterations.

PATIENTS AND METHODS

We investigated a series of 4 patients, aged 10, 18, 29, and 49 years, respectively. When examined, they complained of photophobia and slowly progressive bilateral loss of vision, visual acuity ranging from 0.7 to 0.1.

RESULTS

Ophthalmoscopic examination showed no or minimal alterations such as subtle granular changes in the fovea. Photopic-scotopic full-field ERG was normal. Multifocal ERG, in contrast, showed markedly reduced signal amplitudes within the central 10 degrees.

CONCLUSIONS

Based on the results of multifocal ERG, we were able in each case to consider with a high degree of probability the diagnosis of progressive foveal cone dystrophy. This is to emphasize the sensitivity of multifocal ERG in disorders affecting primarily the macula, without morphological changes, as cone (-rod) dystrophy, early Stargardt dystrophy, etc. The uttermost advantages of multifocal ERG are its innocuity, its applicability to children and the very early sensitivity to changes in retinal function.

Can fixation instability improve text perception during eccentric fixation in patients with central scotomas?

BACKGROUND

Oculomotor behaviour was investigated in 14 patients with central scotomas from age related macular degeneration (AMD) or Stargardt's disease. A scanning laser ophthalmoscope (SLO) was used to project letters and words onto the retina and to assess fixation behaviour. Five patients reported while deciphering letters that they needed to "move their eye" to prevent the image from vanishing. The observation of the SLO fundus images revealed that the gradual disappearance of the stimulus did not result from a transient projection of the word in the lesion. This prompted the authors to investigate, in an experimental setting, whether purposeful changes in fixation position could improve the perception of an eccentrically fixated text stimulus.

METHODS

Twenty normal subjects were asked to alternate fixation, every three to four seconds, between two vertically aligned dots, spaced 10 degrees apart, and to report any changes in the perception of a laterally located letter, 1.5 degrees in height, 7 degrees apart and equidistant between the two fixation spots.

RESULTS

Nineteen subjects reported a transient refreshment of the letter image immediately after the realisation of a saccade. Improved perception lasted approximately a second. With persistent fixation, they noted a rapid fading effect that reduced letter recognition.

CONCLUSION

These observations suggest that ocular instability during eccentric viewing can have a functional advantage, probably related to counteracting Troxler's phenomenon. In addition to alternating between PRLs, it appears that saccades related to fixation instability might be valuable and improve text perception in individuals with a central scotoma and eccentric fixation. This possibility should be taken into consideration when conducting visual rehabilitation procedures.

Ganglion cells from chick retina display multiple functional nAChR subtypes

We have examined the properties of nicotinic acetylcholine receptors in embryonic chick retinal ganglion cells. Ganglion cells, identified according to morphological and physiological criteria, displayed spontaneous or induced action potentials. In 94/99 cells acetylcholine pulses evoked responses. In current clamp mode, acetylcholine provoked membrane depolarization and triggered action potentials. Under voltage clamp conditions, acetylcholine evoked inward currents that were readily blocked by d-tubocurarine. Antagonists specific for homomeric (alpha-bungarotoxin) and heteromeric (dihydro-beta-erythroidine) receptors revealed that ganglion cells express multiple functional receptor subtypes. These findings demonstrate that ACh modulates the electrical activity of these cells and is likely to mediate synaptic transmission. The presence of multiple receptor subtypes may contribute to processing and transmission of information in the retina.

Direction-selective motion blindness after unilateral posterior brain damage

Motion blindness (MB) is defined as the selective disturbance of visual motion perception despite intact perception of other features of the visual scene. MB is characterized by a pandirectional deficit of motion direction discrimination and is assumed to result from damage to the visual motion pathway, especially area MT/V5. However, the most characteristic feature of primate MT/V5 neurons is not their motion selectivity but their preference for one direction of motion (direction selectivity), which changes incrementally at neighbouring columns. In addition to this microscopic directional organization, studies in nonhuman and human primates suggest that single directions of motion are also coded at a more macroscopic level. We thus hypothesized that if MB in humans results from damage to direction-selective neurons in the visual motion pathway, posterior brain damage might cause MB which is direction selective, not pandirectional. The present study investigated motion direction discrimination in patients with posterior unilateral brain damage and determined separate psychophysical thresholds for the four cardinal directions. In addition, we analysed whether the direction of erroneous motion perception (i.e. the perception of right motion for upward motion) was random or showed a directional bias. We report three principal findings. First, motion direction discrimination was severely impaired in one or two directions while it was normal in the other directions. This constituted direction-selective MB. Second, MB was characterized not only by a quantitative direction-selective increase in psychophysical thresholds but also by a qualitative impairment of perceiving motion direction systematically in wrong directions. Both findings suggest that the cortical modules specialized for the perception of a single direction of motion might be larger than previously thought. Third, lesion analysis showed that unilateral damage, not only the human homologue of MT/V5 but also to parieto-occipital cortex, leads to MB.

Dog phobia in a motion-blind patient

INTRODUCTION

A prominent neurophysiological model of phobia generation holds that specific phobia might result from the uncoupling of unaware subcortical fear responses from aware cortical fear responses. Former responses are thought to be automatic and fast, providing approximate information about the external stimulus, whereas the latter responses are more controlled and allow comparison with previous experience. Since only the cortical pathway carries information available to awareness, this model also accounts for the striking irrationality of specific phobia in humans.

METHODS

Here, we report neuropsychological and neuro-ophthalmological findings in a 41-year-old patient who developed severe dog phobia following bilateral parietal lobe damage.

RESULTS

The examinations showed a severe deficit in visual motion perception (visual motion blindness or akinetopsia) as well as spatial vision. Importantly, the patient was largely unaware of his visual deficits.

CONCLUSION

Based on the present observation it is argued that irrational fear, as found in specific phobia, might not only result from a general uncoupling of aware cortical from unaware subcortical fear responses, but also from a functionally similar dissociation at the cortical level.

Visual consciousness in health and disease

Conscious experience is an essential part of normal human life and interaction with the environment. Yet the nature of consciousness and conscious perception remains a mystery. Because of its subjective nature, consciousness has been difficult to investigate scientifically, but clues have been gained through studies involving patients with cortical lesions. During the past decade, the development of event-related fMRI has provided insights into aspects of conscious perception in control subjects and patients with cortical lesions by correlating awareness and performance with neural activity during visual tasks. This article reviews how recent research has advanced understanding of conscious perception, its relationship to neural activity and visual performance, and how this relationship can be altered by visual dysfunction. It also presents recent research about how conscious awareness of vision might be represented at a neural level in the central nervous system.

[Morganella morganii endophthalmitis after vitrectomy: case report and review of the literature]

BACKGROUND

Postoperative bacterial endophthalmitis are caused in 80 % of the cases by the patient's own flora. Most of the time, bacterial agents are Gram-positive ((2/3) of cases) and more rarely Gram-negative ((1/3) of cases). Usually, Pseudomonas sp, Proteus sp or Klebsiella sp are isolated, but very rarely Morganella morganii.

HISTORY AND SIGNS

We describe a case of a Morganella morganii endophthalmitis which occurred after a vitrectomy.

THERAPY AND OUTCOME

Bacterial examinations disclosed the presence of Morganella morganii in the vitreous. An aggressive treatment (intravitreous [ceftazidim, vancomycin], topical [gentamycin, chloramphenicol] and intravenous [imipenem, ofloxacin] antibiotics) was introduced. In spite of this treatment, the outcome was not favorable.

CONCLUSIONS

Post-vitrectomy endophthalmitis is very rare and the isolation of a Gram-negative bacteria, in this case Morganella morganii, is infrequent. The outcome of these infections is often poor despite the introduction of a rapid, specific and aggressive treatment.

[Cerebral sinus thrombosis in Behçet disease: case report and review of the literature]

BACKGROUND

Behçet's disease is a chronic inflammatory disorder, clinically characterised by multisystemic vasculitis. Primary neurologic involvement in childhood is quite exceptional. We report a case of a child with recurrent venous thrombosis of the dural sinus. Behçet's disease was diagnosed.

HISTORY AND SIGNS

A 13-year-old boy from Eritrea was referred to our clinic with severe headaches and photophobia one month after onset. Ophthalmological examination disclosed a bilateral papilledema. Recurrent oral ulcers and pseudo-folliculitis were present. Pathergy test was positive.

THERAPY AND OUTCOME

Complementary investigations disclosed an inflammatory syndrome. Computertomography was normal. Cranial magnetic resonance venography disclosed multiple cerebral sinus thrombosis (superior sagittal sinus, sigmoid sinus and lateral left sinus). There was no evidence of infectious, inflammatory or hypercoagulation disorder. A Behçet's disease was diagnosed based on the medical history and clinical examination. Whilst his general health deteriorated rapidly before treatment, he improved quickly after the onset of therapy with immunosuppression (Prednisone and Ciclosporine) in combination with anticoagulation (coumarin/Sintrom).

CONCLUSION

Behçet's disease is uncommon and difficult to diagnose in children. Neurologic involvement as a first presentation is rarely described, but might be underestimated. We emphasise, therefore, the systematic application of magnetic resonance venography in children with unclear persistent headaches.

Indocyanine green angiographic features in endogenous Candida chorioretinis

BACKGROUND

To describe indocyanine green (ICG) angiography (ICGA) findings and clinical features of endogenous mycotic endophthalmitis.

PATIENTS AND METHODS

Two patients (a female 62 years, a male 31 years) were addressed to investigate a progressive unilateral visual loss. Slit-lamp examination disclosed a macular chorioretinitis. A clinical work-up revealed a mycotic infection (Candida albicans). Before treatment an ICGA was performed.

RESULTS

ICGA early frames disclosed hypofluorescent lesions. Progressively, the lesions were surrounded by a slight hyperfluorescence, although the centre of the lesions was still hypofluorescent.

CONCLUSIONS

The presence and persistence of a hypofluorescent lesion after introducing a specific treatment, led us to suspect a necrotic/ischaemic process affecting the choroidal vascular bed. ICGA provided additional information regarding the pathophysiological process and the patient's functional visual recovery.

Chronic hyposphagma revealing primary ocular amyloidosis

BACKGROUND

Amyloidosis is an extracellular accumulation of a clear substance called amyloid in different organs. Fragments of identical proteinic chains are the components of this substance. Amyloidosis can be primary, secondary (chronic inflammation, multiple myeloma, tumour), senile or hereditary.

HISTORY AND SIGNS

A 59-year-old healthy patient was referred with recurrent subconjunctival haemorrhages in his right eye since one year. The clinical examination disclosed the presence of yellowish subconjunctival deposits associated with haemorrhages.

THERAPY AND OUTCOME

Histopathologic examination of these deposits revealed the presence of amyloid. A complete work-up to exclude a systemic disease gave negative results.

CONCLUSIONS

Primary conjunctival amyloidosis is a rare clinical entity that is mainly diagnosed histopathologically. In the presence of a recurrent hyposphagma of unknown aetiology the diagnosis of amyloidosis should be excluded.