The effects of vigabatrin on electrophysiology and visual fields in epileptics: a controlled study with a discussion of possible mechanisms

Purpose: To compare the visual electrophysiology and visual fields of patients taking vigabatrin to those of a control group of epileptics on other anti-epileptic drugs (AEDs). Methods: Fourteen epileptics treated with vigabatrin and 10 control patients treated with other AEDs underwent ERG and EOG. Goldmann visual fields were performed and analysed using standard software to measure areas contained within I4e isopters. Results: The cone and rod b-waves of the ERG, the oscillatory potential amplitudes and Arden indices were reduced in vigabatrin-treated subjects and the oscillatory potentials delayed. The Arden indices were reduced due to an increased dark trough. The areas contained within the I4e isopter of vigabatrin treated subjects were reduced compared to the control group and these areas correlated well with oscillatory potential amplitudes and b-wave amplitudes in the vigabatrin group only. Conclusions:The use of vigabatrin is associated with a reduction of the ERG cone b-wave amplitude and oscillatory potentials which correlates with visual field loss. The Arden ratio is reduced in subjects taking vigabatrin but may recover after cessation. However, visual loss may persist in the presence of a recovered EOG. These findings suggest further effects of the drug than those mediated by GABA receptors, and support the contention that the cause of the field loss may be at least in part due to retinal effects. Possible mechanisms are discussed.     

Seeing in the dusk: physiological basis and investigation

Dark adaptation and seeing in the dusk require a complex interaction of the cone and rod system. Whereas the former provides high temporal resolution and colour vision in daylight, temporal resolution of the latter is smaller but sensitivity higher by a factor of 100 to 1,000. The two operational ranges overlap by several decades. Characteristic symptoms of disease may be derived from the systems' physiological function and should be enquired about specifically. Problems due to opacity of the optic media or reduced visual acuity should be differentiated from night vision disorders in the more specific sense. Apart from a routine ophthalmological examination a set of other tests should be used: When rods function normally the second limb of the dark adaptation curve initiates at 5 - 12 min und reaches a normal absolute threshold after 30 - 40 min; dark adapted visual fields are unrestricted apart from a physiological central scotoma, and the dark adapted electroretinogram (ERG) shows normal amplitudes and latencies for low intensity flashes. The influence of glare on mesopic contrast sensitivity may be investigated with a mesoptometer. Night vision disorders may arise from cone system dysfunction, too. Intact cone vision provides high visual acuity, normal colour vision, normal photopic visual fields, a quick regeneration within minutes during the first limb of the dark adaptation curve and normal single flash and oscillatory potentials in the light-adapted ERG. Localised defects may be detected using the multifocal ERG. Interpretation of the results must account for the age-related decay of contrast sensitivity and speed of adaptation.     

Attenuation of the retinal nerve fibre layer and reduced retinal function assessed by optical coherence tomography and full‐field electroretinography in patients exposed to vigabatrin medication

Purpose: To investigate the clinical value of assessment of peripapillary retinal nerve fibre layer (RNFL) thickness with OCT in addition to the evaluation of retinal function measured by full‐field electroretinography (ff‐ERG) in patients with suspected vigabatrin (VGB)‐attributed visual field defects. Methods: Visual fields from adult patients in our clinical follow‐up program for VGB medication were analysed. Twelve patients with suspected VGB‐attributed visual field defects were selected for the study. They were re‐examined with computerized kinetic perimetry, ff‐ERG and OCT (2D circle scan). Results: Constricted visual fields were found in all patients. Comparative analysis of ff‐ERG parameters showed reduced b‐wave amplitudes for the isolated and the combined rod and cone responses (p < 0.0001). The a‐wave, reflecting photoreceptor activity, was reduced (p = 0.001), as well as the summed amplitude of oscillatory potentials (p = 0.029), corresponding to inner retinal function. OCT measurements demonstrated attenuation of the RNFL in nine of 12 patients, most frequently superiorly and/or inferiorly. No temporal attenuation was found. Significant positive correlations were found between the total averaged RNFL thickness, superior and inferior RNFL thickness and reduced ff‐ERG parameters. Positive correlations were also found between RNFL thickness and isopter areas. Conclusion: OCT measurements can detect attenuation of the RNFL in patients exposed to VGB medication. RNFL thickness correlates with reduced ff‐ERG parameters and isopter areas of constricted visual fields, indicating that VGB is retino‐toxic on several levels, from photoreceptors to ganglion cells. The study also supports previous studies, suggesting that OCT measurement of the RNFL thickness may be of clinical value in monitoring patients on vigabatrin therapy.     

Vigabatrin and retinal changes

Purpose: Vigabatrin is an effective antiepileptic drug but visual field constriction (VFC) is found to be a severe side-effect. The aims have been to investigate whether visual field constriction (VFC) is related to changes in the electroretinography (ERG). Methods: Twenty patients with localisations related epilepsy of whom one half had received vigabatrin were subjected to examination without informing about the treatment given. The eye examination included Goldmann perimetry and ERG. Results: All the patients had normal visual acuity. A total of three patients (30%) in the vigabatrin group and none in the control group were found to have VFC. In the vigabatrin group ERG examination were normal in one case, in five cases there were changes scotopic, photopic and in the oscillatory potentials (OP), while the remaining four had changes in two of these parameters. OPs were abnormal in eight of 10 patients. Of the three patients with VFC all had changes in ERG. The four patients with the most severe abnormalities in ERG had received high daily doses of vigabatrin (4 – 6 mg) in a period. In the control group no abnormality was observed in five cases, and in the remaining five changes were present in one or two of the potentials. Conclusion: It is found that 30% of patients treated with vigabatrin, develop VFC, and none in the control group. Similarly more patients in the vigabatrin group had changes in the ERG as compared to the control group, and the number of abnormal potentials are significantly higher among patients with VFC compared to those without. But the finding of abnormal ERG results is not synonymous with VFC, and this is important to bear in mind when examining patients that cannot cooperate to a VF examination. An individual sensitivity to vigabatrin is supposed, but severe ERG changes occurred in all patients having had high daily doses slant4 g.     

Symptomatic abnormalities of dark adaptation in patients with EFEMP1 retinal dystrophy (Malattia Leventinese/Doyne honeycomb retinal dystrophy)

PURPOSE: To investigate the nature of symptomatic visual disturbance in patients with EFEMP1 retinal dystrophy in the absence of geographic atrophy or choroidal neovascularization. METHODS: Patients presenting to a tertiary referral centre underwent clinical evaluation, fluorescein angiography, colour contrast sensitivity, focal, pattern, and standard electroretinography, electrooculography, scotopic threshold perimetry and dark adaptometry. RESULTS: Clinical features included reduced central vision, difficulty passing from light to dark, and diffuse submacular and peripapillary deposits, which were hyperfluorescent by fluorescein angiography. Colour contrast thresholds were abnormal in all six patients studied and both pattern and focal electroretinograms were abnormal in five of six patients. The scotopic and mixed rod-cone single flash ERG was normal but two patients demonstrated reduced oscillatory potentials and one had borderline delayed 30 Hz responses. Scotopic thresholds were elevated and rod-mediated dark adaptation kinetics were markedly prolonged in all six patients when measured over the central visible confluent deposits. CONCLUSIONS: In patients with EFEMP1 retinal dystrophy with confluent macular deposits, scotopic sensitivity is reduced and dark adaptation kinetics are prolonged over the macular deposits but are normal elsewhere. These results emphasize the localised nature of functional deficits in some patients with EFEMP1 retinal dystrophy and correlate well with the patient's visual symptoms. Symptomatic visual dysfunction may precede the development of clinically evident geographic atrophy or choroidal neovascularization in this disorder.     

Retinal dysfunction in patients treated with vigabatrin

PURPOSE: To present the current knowledge of vigabatrin influence on the retinal function and to introduce a case report of toxic retinopathy diagnosed in our laboratory, in patient treated with vigabatrin. MATERIAL AND METHODS: A review study based on other authors', concerning the role of diagnostic tests like: perimetry, flash electroretinography (ERG), multifocal electroretinography (mfERG), electrooculography (EOG) in patients treated with vigabatrin and presentation of toxic retinopathy in drug-resistant epileptic patient treated with vigabatrin. RESULTS: In vigabatrin treated patients a functional or structural retinal changes may occur, what can be measured by electrophysiological and visual field testing. Irreversible abnormalities of visual field and ERG tests results prove the toxic character of retinopathy in presented vigabatrin treated patient. CONLUSIONS: ERG tests and visual field assessment should be performed in patients treated with vigabatrin. Initial abnormalities occurrence should be a signal for considering the change of therapy.     

Annular fundus autofluorescence abnormality in a case of macular dystrophy

Purpose: To present a case of macular dystrophy with early changes in fundus autofluorescence. Methods: A 20-year-old woman with a recent loss of visual acuity and onset of photophobia was examined. Color vision and visual field testing, fluorescein angiography, full-field and multifocal electroretinograms as well as fundus autofluorescence were performed. Results: Best-corrected visual acuity was 20/100 (right eye) and 20/60 (left eye). There was a red-green color vision defect and a relative central scotoma in both eyes. Ophthalmoscopy and fluorescein angiography were essentially normal, the presence of a dark choroid was debatable. Full-field ERG responses were normal, but the multifocal ERG showed severely reduced responses in the macular region. Both eyes showed a slight circular parafoveolar increase of fundus autofluorescence. Conclusion: Besides multifocal ERG, fundus autofluorescence aids to objectively assess the manifestation of macular dystrophies but does not discern between different types in early stages.     

Enhanced S-cone syndrome with preserved macular structure and severely depressed retinal function

We present ophthalmic features and genetic analysis findings of a 44-year-old croatian patient with enhanced S-cone syndrome (ESCS). Complete ophthalmic examination, Ishihara colour vision test, dark adaptometry, spectral-domain optical coherence tomography (SD-OCT), fundus autofluorescence imaging, Goldmann visual field and automated perimetry, full-field electroretinography (ERG), multifocal ERG, S-cone ERG and ON–OFF ERG were performed. Mutation screening of the NR2E3 gene, which encodes a photoreceptor-specific orphan nuclear receptor, was performed with polymerase chain reaction amplification and direct sequencing. The patient has good visual acuity and normal colour vision. Fundus examination showed normal posterior pole and nummular pigment depositions at the level of the retinal pigment epithelium in the mid-periphery of the retina. The SD-OCT images showed normal macular structure and thickness. The ERG showed characteristic findings: photopic and scotopic responses to the same stimulus had a similar waveform and were dominated by short-wavelength-sensitive mechanisms. Mutation analysis revealed the known NR2E3 mutation c.481delA (p.Thr161HisFsX18) and the novel NR2E3 variant c.1120C > T (p.Leu374Phe). To the best of our knowledge, this is the only ESCS patient older than 40 years who phenotypically has preserved macular structure, good central visual acuity and severely depressed full-field ERG as well as the first reported patient with NR2E3 mutation from Croatia.     

Functional and clinical findings in 3 female siblings with crystalline retinopathy

Purpose To present functional and clinical findings in three female siblings with crystalline retinopathy. Methods Functional and clinical examinations, including full-field and multi-focal electroretinograms (ERG), visual field, dark adaptation and fundus fluorescein angiography (FFA) were performed in three female siblings of a nonconsanguineous Chinese family, who exhibited characteristic retinal crystalline flecks of Bietti crystalline retinopathy. Results Ophthalmological examination revealed similar findings in the first and second daughter of the family. Best-corrected visual acuity was hand movement and finger counting respectively and funduscopic examination showed RPE clumping and relatively fewer yellow-white deposits in the posterior pole and mid-peripheral retina. FFA revealed massive RPE and choriocapillaris destruction. Ganzfeld ERG was undetectable or reduced markedly and multifocal ERG showed all responses were markedly depressed. Ophthalmological examination showed relative preservation of retinal function in the third daughter of the family (the proband). Best-corrected visual acuity was 0.5 in the right eye and 0.4 in the left eye. Funduscopic examination showed numerous crystal deposits scattered throughout the posterior pole. Dark adaptation revealed rod thresholds elevated dramatically and visual field examination demonstrated paracentral scotomas in both eyes. Full-field ERG was decreased slightly and multifocal ERG showed the central responses were markedly depressed. Conclusion The present study describes typical crystalline retinopathy affecting three female siblings in a family.     

Visual electrophysiological effect of a GABA transaminase blocker

Vigabatrin is an antiepileptic drug for the treatment of partial seizures. The anticonvulsant effect is achieved by irreversible inhibition of the enzyme GABA-transaminase which catalyses the inactivation of GABA. Vigabatrin has been associated with visual field loss and electrophysiological abnormalities. The purpose of the study was to determine any alterations in normal volunteers of the visual field and the visual electrophysiology resulting from a short exposure to vigabatrin. A three-way, double-blind study of placebo, carbamazepine and vigabatrin was undertaken at baseline and on days two, four and nine. Seven subjects completed all three cycles and 14 subjects (six females and eight males; mean age 27.3 years SD 6.7) completed at least one cycle. Static threshold automated perimetry comprised Humphrey Visual Field Analyzer Programs 30-2 and 30/60-2. Electro-oculography and electroretinograms were performed with undilated pupils using the Medelec Ganzfeld stimulator GS2000. The visual field was unaffected by placebo, carbamazepine or vigabatrin. The group mean amplitudes and latencies for the scotopic ERG, 30Hz flicker ERG and the oscillatory potentials remained unchanged for any cycle. The group mean photopic ERG b-wave latency increased from baseline (p < 0.05); no significant change occurred with carbamazepine or placebo. The group mean Arden Index for vigabatrin decreased from baseline to day 9 (p <; 0.01); no significant differences were present for carbamazepine or placebo. Vigabatrin has a rapid effect on both the photopic ERG and the EOG; however, the changes merely reflect alterations in retinal GABA levels secondary to concomitant blocking of GABA transaminase by existing vigabatrin therapy. This revised version was published online in July 2006 with corrections to the Cover Date.     

Visual field and electrophysiological abnormalities due to vigabatrin

The purpose of this study was to determine the electrophysiological changes in patients using the anti epileptic drug vigabatrin and to correlate these findings with the previously reported risk for visual field loss in these patients. In 1998 the neurologists of both involved hospitals referred all patients on vigabatrin medication for ophthalmological examination to the outpatients clinics. Of the 33 patients whom were referred to our outpatient clinics, four had to be dropped from the study because of disability to perform the examinations the remaining 29 patients were included in the study. Standard ophthalmological investigations were carried out, and contrast sensitivity, visual field (Humphrey 30-2 and Esterman or Octopus 32), colour vision (panel D15), ERG and EOG according to ISCEV standards were tested. 18 patients continued the medication and 11 stopped taking the drug during the study. Nine of the patients who stopped the drug were followed during at least half a year afterwards, this group will be described in the combined article `Electro ophthalmic recovery after withdrawal from vigabatrin' (Graniewski and Van der Torren, this issue). The electro-ophthalmological findings in the group of 29 patients were correlated with the visual fields and the daily and cumulative dosages of vigabatrin. Of the patients, 32% showed no visual field constriction at all; from these patients 64% had EOG and/or ERG changes. Of the patients with slight to marked visual field constriction, 90% presented EOG and/or ERG changes. Significant correlation between daily dosages of vigabatrin and visual field defects was shown as well as between visual field defects and rod and cone b wave amplitude reductions. Cumulative vigabatrin dosages presented a significant correlation with EOG ratio and ERG rod b-wave amplitude. Conclusively EOG and ERG testing were found to be even an more accurate way to monitor the direct vigabatrin effect on the outer retina and is possible different from the visual field testing.     

Involutional diabetic retinopathy.

The end-stage or involutional phase of proliferative diabetic retinopathy may result in stabilization of vision for long periods of time. However, the clinical resemblance to the progressive tapetoretinal degenerations suggests that marked functional impairment of the retina is present in such eyes. We studied 19 eyes with involutional retinopathy to document the status of the retinal function. Studies included fluorescein angiography, visual field examination, dark adaptation testing, color vision testing, electro-oculography and electroretinography (ERG). The results indicated marked functional abnormalities in all eyes. The ERG tracings showed uniformly subnormal responses and delayed implicit times, similar to those of dominantly inherited retinal pigment degeneration, and indicative of a progressive retinal disorder. In two patients, color vision testing showed defects similar to those seen in inherited tritanopia; and in the remaining patients, defects were indicative of an acquired blue-yellow dyschomatopsia.     

Electroretinographic (ERG) responses in pediatric patients using vigabatrin

The antiepileptic drug vigabatrin is known to cause retinal and visual dysfunction, particularly visual field defects, in some patients. Electroretinography (ERG) is used in an attempt to identify adverse effects of vigabatrin (VGB) in patients who are not candidates for conventional perimetry. We report data from 114 pediatric patients taking VGB referred for clinical evaluation; median age at test was 22.9 (2.4 to 266.1) months, and median duration of VGB use was 9.7 (0.3 to 140.7) months. Twenty-seven of them were tested longitudinally (3 to 12 ERG tests). ERG responses to full-field stimuli were recorded in scotopic and photopic conditions, and results were compared to responses from healthy control subjects. We found that abnormalities of photoreceptor and post-receptor ERG responses are frequent in these young patients. The most frequently abnormal scotopic parameter was post-receptor sensitivity, log σ, derived from the b-wave stimulus-response function; the most frequently abnormal photopic parameter was the implicit time of the OFF response (d-wave) to a long (150 ms) flash. Abnormal 30-Hz flicker response amplitude, previously reported to be a predictor of visual field loss, occurred infrequently. For the group as a whole, none of the ERG parameters changed significantly with increasing duration of VGB use. Four of the 27 patients tested longitudinally showed systematic worsening of log σ with duration of VGB use. In a subset of patients who underwent perimetry (N = 39), there was no significant association of any ERG parameter with visual field defects. We cannot determine whether the ERG abnormalities we found were due solely to the effects of VGB. We caution against over-reliance on the ERG to monitor pediatric patients for VGB toxicity and recommend further development of a reliable test of peripheral vision to supplant ERG testing.     

Oscillatory potentials and pattern electroretinogram: are they related?

The possible relationship between the pattern electroretinogram (ERG) and oscillatory potentials was investigated in two patients with night blindness. One patient had congenital stationary night blindness of Schubert-Bornschein type, and the other had Oguchi's disease. Both had normal visual acuity, normal mass photopic (cone) ERG and normal local macular ERG. In each patient, scotopic (rod) ERG after 20-minute dark adaptation was nonrecordable and the single bright flash ERG was of the negative type. The difference between the ERG pattern of the two patients was found in the oscillatory potentials. The patient with congenital stationary night blindness showed no oscillatory potentials, whereas the patient with Oguchi's disease had good oscillatory potentials. The pattern ERG in both patients was normal. Based on the data of these two patients, it was thought that the pattern ERG is not closely related to the oscillatory potentials and may have different mechanisms of generation.     

Electrophysiological estimation of the function of different retinal zones in normal eyes and in retinal degenerations

By means of electroretinographical responses from different areas of the retina (zonular ERGs) both healthy people and patients with central and peripheral retinal degenerations were examined. Responses were registered from three retinal areas (zones): central (red, green, and blue stimuli, 10 ° in diameter, during adaptation of 20 lux); paramacular (a dim, blue, ringlike stimulus, 15 ° inner and 50 ° outer diameter, presented at the beginning of dark adaptation) and peripheral (very dim, blue ring stimulus of a 50 ° inner and 110 ° outer diameter, after 3 min of dark adaptation). The data obtained by this method of stimulation give information about the function of stimulated retinal areas and provide new criteria for the function of the spectrally different photoreceptors responsible for intact color vision. Examples are presented that reveal the value of this method for the detection of congenital color vision defects and for the classification of different types of retinal degeneration. This method is shown to be highly effective and has many advantages over the common routine Ganzfeld ERG technique, especially in cases of unusual retinal degenerations.     

Electrophysiologic studies in birdshot chorioretinopathy

We investigated retinal function in 16 patients with birdshot chorioretinopathy. Consistent abnormalities of dark adaptation, color vision, visual field, electro-oculography, electroretinography, and visual-evoked cortical potentials were found. They included raised thresholds of dark adaptation, acquired dyschromatopsia, mainly of the blue-yellow type, an electroretinogram with reduced amplitude, increased latency of the b-wave and absent oscillatory potentials, an abnormal electro-oculogram, and in many a marked disturbance in the pattern reversal visual-evoked cortical potential. The a-wave of the electroretinogram, the fast oscillations of the standing potential, and the flash visual-evoked cortical potential were well preserved. The nature of the abnormalities suggests that dysfunction was caused by inner retinal disease. Little evidence indicated outer retinal dysfunction resulting from choroidal inflammation.     

A Korean family with an early-onset autosomal dominant macular dystrophy resembling North Carolina macular dystrophy

PURPOSE: To characterize and report the phenotype of a Korean family with an early-onset autosomal dominant macular dystrophy resembling North Carolina macular dystrophy (NCMD). METHODS: Five members of a Korean family were examined clinically and underwent fundus photography, fluorescein angiography, indocyanine green angiography, optical coherence tomography, full field electroretinogram (ERG), multifocal ERG, electro-oculography (EOG), a color vision test, and a visual field test. RESULTS: Visual acuity ranged from 20/200 to 20/20. Fundus findings demonstrated varying degrees of involvement ranging from drusen only to chorioretinal involvement. Central scotoma corresponded to retinal lesions in two patients. Full field ERG was normal but multifocal ERG showed decreased amplitude and delayed implicit time in the macular area. EOG was normal except in one patient. Color vision tests were also normal. CONCLUSIONS: The phenotype of this Korean family is consistent with NCMD. Linkage analysis is required to confirm the diagnosis.     

Evaluation of typical and atypical retinal pigmentary dystrophy by three dimensional analysis (XY plane and time) of averaged electroretinograms

Retinal functional imaging of patients with typical and atypical retinal pigmentary dystrophies was investigated by three dimensional (XY plane and time) analysis of ERG topography by comparing visual field and fluorescein angiographic findings. The three dimensional analysis revealed that the area of maximal amplitude deviated to the skin area closest to the dominant location of the retinal pigmentary dystrophy (the so-called paradoxical localization). In patients with temporoinferior sectorial retinal pigmentary dystrophy, for example, the maximal amplitude of the a-, b-waves and retinal oscillatory potentials deviated toward the temporoinferior side on the surface topography. These characteristic phenomena of a- and b-waves were found in 60.8% of all patients. Flicker topography with a stimulus frequency of 30 Hz was especially successful in showing the existence and location of paramacular involvement of retinal dystrophy within the area surrounding temporal vascular arcades. The detectability of macular asymmetric involvement was 65.2%. No significant topographic changes were detected in cases in the early stage with no remarkable visual field defects, or in the end stage with remarkable concentric field defects and complicated glaucomatous visual field defects. A comparative study of topographic changes, visual field changes and fluorescein angiographic findings showed that topographic changes in the a-, b-waves, retinal oscillatory potentials and 30Hz flicker components coincided more closely with visual field changes than fluorescein angiographic findings. We proposed that retinal pigmentary dystrophy is not a homogeneous lesion in its progression and believe that the ERG topography method can, by the imaging of dominant locations, detect this disease as well as visual field testing.     

Acute macular neuroretinopathy--case report

PURPOSE: The aim of this study is to present rare retinal disease of unknown origin. MATERIAL AND METHODS: 27-years-old man was diagnosed because of poor vision in the left eye, which lasted 4-5 weeks. Following examinations were performed: Visual acuity, contrast sensitivity, color perception, visual field, fluorescein angiography (AF), visual evoked potentials (VEP), full-field flash electroretinography (flash ERG), focal-foveal electroretinography (focal ERG), multifocal electroretinography (multifocal ERG). Follow-up 1.5 year. RESULTS: Visual acuity of right eye was 1.25 (-0.1 log MAR) and left eye 1.0 (0.0 log MAR). In left eye between optic disc and macula irregular lesion with dots of retinal pigment epithelium atrophy and little edema was seen. AF revealed small "window" defects. In visual field of the left eye paracentral relative scotoma occurred and in stereokampimetry central relative scotoma was found about 5 degrees from the fixation point. In VEP latency of P100 was delayed and amplitude was reduced in both eyes. In flash as well as focal ERG small reduction of cone function and delayed implicit time of b-wave were found in left eye. In general examination no focal inflammation and no abnormalities in laboratory tests were found. The patient was treated with steroids for 3 weeks. After ten days of general steroid treatment visual acuity improved to 1.25 and subjective improvement of vision occurred. Control examination after 1.5 year revealed no patient's complains, visual acuity 1.25, no change in visual field, VEP improvement. In left eye flat irregular area with pigment epithelium atrophy was seen. CONCLUSIONS: Acute macular neuroretinopathy may be diagnosed after detail examination. Prognosis is generally good, recovery is slow, but despite of local retinal atrophy subjective complains disappear completely.     

视杆细胞视觉传导的慢快通道及临床应用研究进展

视杆细胞对视觉,特别是暗视觉的形成具有重要的作用。视杆细胞与神经节细胞之间视觉传导的具体通道和过程目前尚不清楚。20年前,国外学者认识到在视网膜视杆细胞与神经节细胞之间的视觉传导可能并非只存在一条通道。在15Hz频率下,利用暗适应闪烁光视网膜电图（ERG）可将视杆细胞慢快通道的各自反应分离出来。某些疾病,如视网膜色素变性（RP）、Stargardt黄斑营养不良、完全性静止性夜盲的暗适应15Hz闪烁光ERG反应则表现出某些特性。就视杆细胞多条视觉传导通道的发现、传导途径及临床应用进行综述。