Investigating retinal toxicity of tempol in a model of isolated and perfused bovine retina

Purpose

Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl) is a membrane-permeable superoxide dismutase and potentially neuroprotective substance. This study evaluates the retinal tolerance of 0.5 mM, 1 mM, 2 mM, and 5 mM tempol measured by the electroretinogram (ERG) of an isolated and perfused retina whole mount.

Methods

For functionality testing, bovine retinas were prepared and perfused with an oxygen-saturated standard solution, and the ERG was recorded until stable b-wave amplitudes were reached. Tempol concentrations of 0.5 mM, 1 mM, 2 mM, and 5 mM were tested for 45 minutes. To investigate the effects on photoreceptor function, 1 mM aspartate was added to suppress the b-wave and obtain isolated a-waves. ERG amplitudes were monitored for 100 minutes.

Results

While no toxic effects for concentrations of 0.5 mM and 1 mM tempol could be detected, concentrations of 2 mM tempol and higher caused statistically significant negative effects on the b-wave amplitude (?38 %, p?=?0.02 for 2 mM; ?54 %, p?= 0.02 for 5 mM). The a-wave amplitude remained stable even at higher concentrations.

Conclusions

Although the photoreceptors seem to have a tolerance to high concentrations of tempol, higher intravitreal concentrations than 1 mM should be considered critical.     

Electrophysiologic evaluation of retinal function in patients with psoriasis and vitiligo

Purpose

To investigate the relation between psoriasis and vitiligo with the electrophysiologic function of the retinal photoreceptors.

Methods

Patients with psoriasis or vitiligo referred for PUVA therapy were enrolled. Complete eye examination was performed. Patients with any drug or familial history or abnormal eye examination that might affect the retinal function were excluded. Standardized full-field electroretinogram (ERG) elicited with Ganzfeld stimuli using the commercial ERG system (Retiport32; Roland Consult) according to International Society for Clinical Electrophysiology of Vision guidelines was performed. The outcome measures were the difference between the mean rod response, standard combined response, single-flash cone response and 30-Hz flicker wave amplitudes of the patients and normal population.

Results

Seventy-six eyes of 38 patients (vitiligo: 21; psoriasis: 17) and 40 eyes of 20 normal subjects were enrolled in this study. The mean age of patients was 31.3 ± 11.3 years (range 16–54 years). Twenty-two patients (58 %) were female. The mean rod response b-wave, standard combined a- and b-waves, single-flash cone response b-wave and the 30-Hz flicker (N1-P1) amplitudes were significantly lower than the normal population in the same range of age as the study group. There was no significant difference between the patients with vitiligo and those with psoriasis in all wave amplitudes (P = 0.094).

Conclusion

This study showed that overall retinal electrophysiologic function in patients with vitiligo or psoriasis is significantly impaired compared with normal population, independent of age and sex.     

Spatial differences in corneal electroretinogram potentials measured in rat with a contact lens electrode array

Purpose

It has been known for several decades that the magnitude of the corneal electroretinogram (ERG) varies with position on the eye surface, especially in the presence of focal or asymmetric stimuli or retinal lesions. However, this phenomenon has not been well-characterized using simultaneous measurements at multiple locations on the cornea. This work provides the first characterization of spatial differences in the ERG across the rat cornea.

Methods

A contact lens electrode array was employed to record ERG potentials at 25 corneal locations simultaneously following brief full-field flash stimuli in normally sighted Long-Evans rats. These multi-electrode electroretinogram (meERG) responses were analyzed for spatial differences in a-wave and b-wave amplitudes and implicit times.

Results

Spatially distinct ERG potentials could be recorded reliably. Comparing relative amplitudes across the corneal locations suggested a slight non-uniform distribution when using full-field, near-saturating stimuli. Amplitudes of a- and b-waves were approximately 3 % lower in the inferior quadrant than in the superior quadrant of the cornea.

Conclusions

The present results comprise the start of the first normative meERG database for rat eyes and provide a basis for comparison of results from eyes with functional deficit. Robust measures of spatial differences in corneal potentials will also support optimization and validation of computational source models of the ERG. To fully utilize the information contained in the meERG data, a detailed understanding of the roles of the many determinants of local corneal potentials will eventually be required.     

Contribution of N-methyl-dl-aspartic acid (NMDA)-sensitive neurons to generating oscillatory potentials in Royal College of Surgeons rats

Purpose

We investigated how the N-methyl-dl-aspartic acid (NMDA) receptor contributes to generating oscillatory potentials (OPs) of the electroretinogram (ERG) in the Royal College of Surgeons (RCS) rat.

Methods

Scotopic ERGs were recorded from dystrophic and wild-type congenic (WT) RCS rats (n = 20 of each) at 25, 30, 35, and 40 days of age. The stimulus intensity was increased from ?2.82 to 0.71 log cd-s/m² to obtain intensity-response function. NMDA was injected into the vitreous cavity of the right eyes. The left eyes were injected with saline as controls. The P3 obtained by a-wave fitting was digitally subtracted from the scotopic ERG to isolate the P2. For the OPs, the P2 was digitally filtered between 65 and 500 Hz. The amplitudes of OP1, OP2, OP3, and OP4 were then measured and summed and designated as ΣOPs. The implicit times of OP1, OP2, and OP3 were also measured. The frequency spectra of the OPs were analyzed using fast Fourier transform (FFT).

Results

The maximum ERG a- and b-waves as well as ΣOPs amplitudes reduced with age in dystrophic rats. Compared with intravitreal saline injection, administration of NMDA decreased ΣOPs amplitudes from 30 days of age in dystrophic rats, while it did not attenuate ΣOPs amplitudes in WT rats. The implicit times of the OPs of the maximum ERG were prolonged by NMDA injections in WT and dystrophic rats. NMDA/saline ratios of ΣOPs amplitudes area under the FFT curves were significantly lower in dystrophic rats from 30 days of age than that in WT rats.

Conclusion

In the early stage of photoreceptor degeneration, intravitreal NMDA injection attenuated OPs amplitudes in dystrophic rats. This indicates that NMDA receptors play a significant role in generating OPs amplitudes with advancing photoreceptor degeneration.     

Electroretinograms and level of aqueous vascular endothelial growth factor in eyes with hemicentral retinal vein occlusion or branch retinal vein occlusion

Purpose

Hemicentral retinal vein occlusion (hCRVO) is a disease related to CRVO but not to branch retinal vein occlusion (BRVO). We reported a significant correlation between aqueous vascular endothelial growth factor (VEGF) levels and the implicit time of 30-Hz flicker electroretinogram (ERG) in CRVO eyes. The purpose of this study was to compare aqueous VEGF levels and ERG components between hCRVO and BRVO eyes.

Methods

The medical records of patients with macular edema secondary to hCRVO (12 eyes) or BRVO (16 eyes) and received an intravitreal injection of bevacizumab (IVB) at the Nagoya University Hospital from July 2009 to May 2013 were reviewed. Full-field ERGs were recorded before the IVB. Aqueous humor was collected just before the IVB to measure VEGF concentration. Differences in aqueous VEGF level and ERG components between hCRVO and BRVO eyes were determined.

Results

Mean aqueous VEGF concentration in hCRVO eyes was significantly higher than that in BRVO eyes (504 vs. 148 pg/ml, P < 0.05). The implicit time of 30-Hz flicker ERG was significantly longer in hCRVO than in BRVO eyes (33.5 vs. 29.8 ms, P < 0.01).

Conclusion

The significant difference in VEGF levels in aqueous and implicit times of 30-Hz flicker ERG suggest that retinal ischemia is more manifest in hCRVO than in BRVO eyes.     

Investigation of the retinal biocompatibility of acid violet for chromovitrectomy

Purpose

The primary objective was to investigate the retinal biocompatibility of acid violet (AV) as a vital dye for chromovitrectomy. The secondary objective was to evaluate the capacity of AV to stain the anterior capsule of the lens.

Methods

An amount of 0.05 ml of 0.25 g/l and 0.5 g/l AV was injected intravitreally in the OD, while balanced salt solution (BSS) was applied in the OS for control. Clinical examination and histology with light microscopy (LM) were performed after 7 days. Retinal cell layers were evaluated for morphologic alterations and number of cells. The electroretinographic (ERG) changes were assessed at baseline and 7 days. In another part of the study, 0.1 ml of 0.25 g/l AV was injected into the anterior chamber of ex-vivo porcine eyes, and its capacity to stain the anterior capsule was determined. Cadaveric eyes were used to test the capacity of AV to stain the internal limitant membrane (ILM) during vitrectomy.

Results

The gross histopathologic appearance of the retina, choroids, sclera, and optic nerve was within normal limits, without any signs of severe retinal necrosis or cystic degeneration. AV caused no substantial retinal alterations in retinal layers by LM at either the lower or higher dose when compared with the control eye. The injection of AV did not induce considerable ERG alterations. The violet dye stained the anterior capsule after anterior chamber injection and the ILM, allowing a safer capsulorrhexis and vitrectomy.

Conclusion

Acid violet may be safe for the retina at concentrations of 0.25 and 0.50 g/l after intravitreous injection, and may be used as a vital dye for staining the anterior capsule and the ILM.     

Possible implications of acid-sensing ion channels in ischemia-induced retinal injury in rats

Background

Retinal ischemia in eyes with diabetic retinopathy and retinal vein occlusion leads to local tissue acidosis. Acid-sensing ion channels (ASICs) are expressed in photoreceptors and other neurons in the retina, and may play a role in acid-induced cell injury. The purpose of this study was to investigate the neuroprotective effects of amiloride, an ASIC blocker, on induced retinal ischemia in rats.

Methods

Transient retinal ischemia was induced in male Long–Evans rats by the temporary ligation of the optic nerve. Just before the induction of ischemia, the experimental eyes underwent intravitreal injection of amiloride. On day 7, the retinal damage in eyes that underwent amiloride treatment (and in those that did not undergo the treatment) was evaluated by histology and electroretinogram (ERG).

Results

Transient retinal ischemia caused retinal degeneration with thinning of the inner layer of the retina. The blockage of ASICs with amiloride significantly prevented retinal degeneration. ERG demonstrated that the reduction in a- and b-wave amplitudes induced by the transient retinal ischemia was significantly prevented by the application of amiloride.

Conclusions

The present study suggests that ASICs might, at least in part, play a pathophysiological role in ischemia-induced neurodegeneration. Blockage of ASICs may have a potential neuroprotective effect in ocular ischemic diseases.     

Decreased retinal–choroidal blood flow in retinitis pigmentosa as measured by MRI

Purpose

To evaluate retinal and choroidal blood flow (BF) using high-resolution magnetic resonance imaging (MRI) as well as visual function measured by the electroretinogram (ERG) in patients with retinitis pigmentosa (RP).

Methods

MRI studies were performed in 6 RP patients (29–67 years) and 5 healthy volunteers (29–64 years) on a 3-Tesla scanner with a custom-made surface coil. Quantitative BF was measured using the pseudo-continuous arterial spin-labeling technique at 0.5 × 0.8 × 6.0 mm. Full-field ERGs of all patients were recorded. Amplitudes and implicit times of standard ERGs were analyzed.

Results

Basal BF in the posterior retinal-choroid was 142 ± 16 ml/100ml/min (or 1.14 ± 0.13 μl/mm²/min) in the control group and was 70 ±19 ml/100ml/min (or 0.56 ± 0.15 μl/mm²/min) in the RP group. Retinal–choroidal BF was significantly reduced by 52 ± 8 % in RP patients compared to controls (P<0.05). ERG a- and b-wave amplitudes of RP patients were reduced, and b-wave implicit times were delayed. There were statistically significant correlations between a-wave amplitude and BF value (r=0.9, P<0.05) but not between b-wave amplitude and BF value (r =0.7, P=0.2).

Conclusions

This study demonstrates a novel non-invasive MRI approach to measure quantitative retinal and choroidal BF in RP patients. We found that retinal–choroidal BF was markedly reduced and significantly correlated with reduced amplitudes of the a-wave of the standard combined ERG.     

Comparisons of cone electroretinograms after indocyanine green-, brilliant blue G-, or triamcinolone acetonide-assisted macular hole surgery

Purpose

To compare the function of retinal ganglion cells (RGCs) using the photopic negative response (PhNR) in patients who had undergone indocyaine green (ICG)-assisted, brilliant blue G (BBG)-assisted, or triamcinolone acetonide (TA)-assisted internal limiting membrane (ILM) peeling during macular hole (MH) surgery.

Methods

Forty-eight eyes of 48 patients with a macular hole were randomly divided into those undergoing ICG-assisted, BBG-assisted, or TA-assisted vitrectomy (n?=?16 for each group). Full-field cone ERGs were recorded before and 1, 3, 6, 9, and 12 months postoperatively. The amplitudes and implicit times of the a-waves and b-waves and the amplitudes of the oscillatory potentials (OPs) and PhNRs were measured. The mean deviations (MDs) of standard automated perimetry and the best-corrected visual acuity (BCVA) were measured. The circumferential retinal nerve fiber layer (RNFL) thickness was evaluated by SD-OCT.

Results

All macular holes were closed with a significant improvement of the BCVA and MD without differences among the groups. There was no significant difference between the preoperative and postoperative RNFL thickness. The implicit times of the a-waves and b-waves were significantly prolonged, and the ΣOPs amplitude was significantly decreased postoperatively in all groups. These ERG changes were not significantly different among the groups. The postoperative PhNR amplitudes were significantly lower in the ICG group than in the BBG or TA group.

Conclusions

The results indicate that the PhNR may detect subclinical impairments of RGCs caused by the possible toxic effect of ICG. This finding adds to the data that BBG and TA may be safer than ICG for use during MH surgery.     

Functional and high resolution retinal imaging assessment in a case of ocular siderosis

Purpose

To report new findings in a case of ocular siderosis explored by high resolution angiography and adaptive optics (AO).

Methods

We report data on a 40-year-old man with an intraocular foreign body (IOFB) embedded in the sclera after hammering.

Results

Nine months after this accident, the patient presented with full-field electroretinogram (FF-ERG) abnormalities. Subsequent IOFB extraction was performed. One month after the surgery, high resolution angiography showed for the first time small iron particles all over the inner retinal surface. Spreading of these deposits was followed by inflammatory prepapillary new vessels and venous retinal vasculatis, which spontaneously resolved within a few months. ERG responses became slightly electronegative at this time. Clearance of the iron particles was followed over a year with AO and ERG recording. AO revealed an arterial tropism with a decrease in the amount of particles overtime, which may be consistent with macrophagic activity.

Conclusion

High resolution angiography and AO are new tools, combined with electrophysiology, to better understand ocular siderosis pathophysiology.     

Tempol protects against intravitreous indocyanine green-induced retinal damage in rats

Purpose

Indocyanine green (ICG) has been widely used as a vital dye for macular surgery. However, ICG can be toxic to retinal cells. Here we evaluate whether tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl), a free radical scavenger, can protect against ICG-induced retinal damage in rats.

Methods

Brown Norway rats received intravitreal injections of ICG 0.5?% or BSS as controls. Tempol (20?mg/kg BW) or PBS as a control was administered intraperitoneally 24?h and 30?min before ICG and once daily for 7 consecutive days. Tempol was detected in the retina using electron paramagnetic resonance (EPR) spectroscopy. One?week after ICG injections, the effects of tempol on retinal toxicity were assessed by retinal ganglion cell (RGC) back-labeling and by light microscopy. Electroretinography (ERG) was performed after 1 and 2?weeks.

Results

ICG administration reduced RGC numbers by 17?% (1,943?±?45 vs. 2,342 ± 31 RGCs/mm²). Tempol treatment rescued RGCs in a significant manner (2,258?±?36, p?<?0.01) and diminished morphological changes detected by light microscopy. ICG-injected eyes showed a significant reduction of ERG potentials only in PBS-treated animals (V_max 530?±?145?μV vs. 779?±?179?μV, p?=?0.0052), but not in the tempol-treated group.

Conclusions

Tempol significantly attenuates ICG-induced toxicity in rat retinas and may therefore be considered for further evaluation as accompanying treatment in ICG-assisted chromovitrectomy.     

Perfluorocarbon liquid-assisted membrane staining and peeling technique for macular diseases

Purpose

A surgical technique is described that facilitates membrane peeling in patients with macular diseases by using small amounts of perfluorocarbon liquid (PFCL) and brilliant blue G (BBG) dye.

Study Design

Retrospective cohort study.

Methods

After placing about 1.0-1.5 cc PFCL on the macular area, BBG was applied with a 27-gauge blunt needle at the interface of PFCL and retina. The membrane peeling was performed under PFCL.

Results

The amount of BBG dye with PFCL-assisted staining technique has the potential to be smaller than in conventional staining method. Since the displacement angle of the membrane during peeling procedures is considerably increased by PFCL, combined with its high specific gravity and interfacial tension, the risk of tearing the membrane during manipulation is reduced to a great extent. The postoperative visual function in patients with PFCL-assisted peeling was comparable to that of patients without PFCL-assisted peeling.

Conclusion

The PFCL-assisted technique enables sufficient membrane staining with minimal amounts of BBG dye, with tearing of the epiretinal membrane or internal limiting membrane being less likely than with the conventional method.

     

Infliximab exerts a dose-dependent effect on retinal safety in the albino rabbit

Purpose

To study whether the ERG and other clinical findings help to distinguish between advanced hydroxychloroquine (HCQ) retinopathy and pericentral or diffuse retinitis pigmentosa (RP) with similar fundus appearance.

Methods

We conducted a retrospective analysis of patients with advanced HCQ retinopathy (n = 11), pericentral RP (n = 8) and diffuse RP (n = 8). Pericentral RP was defined as having limited fundus damage and relatively normal flicker ERG time-to-peak. Diffuse RP had typical loss of the rod ERG and flicker timing delay. All patients showed reduced amplitude of the ISCEV responses in the full-field electroretinogram (ERG). Aspects of history, visual field results, fundus appearance, fundus autofluorescence and ocular coherence tomography were also compared.

Results

Relative to pericentral RP, patients with HCQ toxicity showed delayed flicker ERG time-to-peak and lower ERG amplitudes, particularly combined rod–cone responses. Relative to diffuse RP, most HCQ toxicity patients had some preserved rod ERG response, and there was no obvious predilection for rod over cone damage. In addition, patients with HCQ toxicity usually lacked markers of long-standing degeneration such as bone spicule figures or severe loss of peripheral field. History of familial disease and long-standing night blindness were specific to RP.

Conclusions

While the early signs of HCQ damage are typically regional in the posterior pole, advanced disease is characteristically diffuse (unlike pericentral RP). This is appropriate for a systemic toxin, as is the finding that rods and cones were both affected in the ERG to a similar degree (unlike genetic rod–cone dystrophies). For patients with severe HCQ exposure and some of our discriminatory findings, and no family history or prior night blindness, HCQ toxicity is a sufficient diagnosis without invoking a second rare disease (Occam’s razor).

     

The effects of excitatory amino acids and their transporters on function and structure of the distal retina in albino rabbits

Purpose

To study the physiological and pathological roles of excitatory amino acid transporters in the distal retina of albino rabbits.

Methods

Albino rabbits were injected intravitreally in one eye with different doses of l- or d-isomers of glutamate or aspartate, with mixtures of l-glutamate and antagonists to glutamate receptors or with inhibitors of glutamate transporters. The other eye was injected with saline, and served as a control. The electroretinogram (ERG) was recorded 4 h and 2 weeks after injection. At the end of the ERG follow-up period, retinas were prepared for light microscopy.

Results

The ERG b-wave was reduced and the a-wave augmented by both isomers of EAAs when tested 4 h after injection. Long-term (2-week) follow-up indicated severe damage to the retina by both isomers of EAAs. Antagonists to glutamate-gated ionic channels failed to protect the rabbit distal retina from permanent damage. Competitive inhibitors of GLAST-1 transporter were highly effective in blocking synaptic transmission in the OPL and in inducing permanent ERG deficit. Selective inhibition of the GLT-1 transporter caused short-term augmentation of the ERG and no permanent ERG deficit.

Conclusion

GLAST-1, the glutamate transporter of Müller cells, plays a major role in synaptic transmission within the OPL of the rabbit retina. Over-activation of GLAST-1 seems to induce permanent damage to the distal rabbit retina via yet unidentified mechanism.     

Changes of Oscillatory Potentials and Photopic Negative Response in Patients with Early Diabetic Retinopathy

Purpose

To investigate the clinical significance of the oscillatory potentials (OPs) and photopic negative response (PhNR) of the electroretinogram (ERG) in patients with early diabetic retinopathy.

Methods

One hundred two diabetic patients with diabetic retinopathy at different stages were examined. Thirty-two age-matched normal controls were also studied. Full-field maximal and photopic cone ERGs were recorded. The amplitudes and implicit times of the OPs, cone b wave, and PhNR were compared at the different stages of diabetic retinopathy.

Results

The a and b wave amplitudes of the maximal scotopic ERGs remained unchanged despite advancing stages of retinopathy, but the OP amplitudes were significantly attenuated even at an early stage of diabetic retinopathy. The amplitudes of both the PhNR and cone b wave were reduced at an early stage of diabetic retinopathy. Analysis of the receiver operating characteristic curves demonstrated that the amplitudes and implicit times of the OPs were more sensitive and specific than those of the PhNR in detecting changes of retinal function in the early stages of diabetic retinopathy.

Conclusions

The amplitudes of the OPs and PhNR progressively decrease with the progression of diabetic retinopathy. The PhNR amplitudes were reduced along with the cone b wave, indicating that earlier change of the PhNR in diabetic patients reflects reduced input to the retinal ganglion cell from the distal retina. The amplitudes and implicit times of the OPs are better indicators than those of the PhNR in detecting functional decreases in patients with early diabetic retinopathy.?Jpn J Ophthalmol 2006;50:367–373 © Japanese Ophthalmological Society 2006     

Evaluation of light- and dark-adapted ERGs using a mydriasis-free,portable system: clinical classifications and normative data

Purpose

The full-field electroretinogram (ff-ERG) is a widely used clinical tool to evaluate generalized retinal function by recording electrical potentials generated by the cells in the retina in response to flash stimuli and requires mydriasis. The purpose of this study was to determine the intra-visit reliability and diagnostic capability of a handheld, mydriasis-free ERG, RETeval (LKC Technologies, Gaithersburg, MD, USA), in comparison with the standard clinical ff-ERG by measuring responses recommended by the International Society for Clinical Electrophysiology of Vision (ISCEV).

Methods

This prospective, cross-sectional study included 35 patients recruited at the Hospital for Sick Children (median age?=?17, range 11 months–69 years) who had undergone a clinical ff-ERG according to ISCEV standards. For RETeval (n?=?35), pupils were undilated in most (n?=?29) and sensor strip electrodes were placed under the inferior orbital rim. Stimulus settings on RETeval were equivalent to those used in the clinical ERG. Fifty-seven control participants (median age?=?22, range 8–65 years) underwent undilated RETeval ERG to establish standard values for comparison. Patient waveform components with amplitudes?<?5th percentile, or implicit times?>?95th percentile of normal relative to control data were classified as abnormal for the RETeval system.

Results

The RETeval system demonstrated a high degree of within-visit reliability for amplitudes (ICC?=?0.82) and moderate reliability for implicit times (ICC?=?0.53). Cohen’s Kappa analysis revealed a substantial level of agreement between the diagnostic capability of RETeval in comparison with clinical ff-ERG (k?=?0.82), with a sensitivity and specificity of 1.00 and 0.82, respectively. Pearson’s correlations for clinical ERG versus RETeval demonstrated a positive correlation for amplitudes across the rod (r?=?0.65) and cone (r?=?0.74) ERG waveforms. Bland–Altman plots showed no bias between the mean differences across all amplitude and implicit time parameters of the two systems.

Conclusions

The present study demonstrated that RETeval is a reliable tool with reasonable accuracy in comparison with the clinical ERG. The portable nature of RETeval system enables its incorporation at resource-limited centers where the ff-ERG is not readily available. The avoidance of sedation and pupillary dilation are added advantages of RETeval ERG.

     

Electroretinogram and visual field changes in a case of birdshot chorioretinopathy

Purpose

This case report explores the role of the visual field perimetry and electroretinogram (ERG) in cases of non-infectious uveitis in the assessment and monitoring of retinal function and response to treatment.

Methods

A 59-year-old Caucasian female presenting with bilateral posterior uveitis newly diagnosed as birdshot chorioretinopathy (BSCR) presenting with bilateral decrease in visual acuity and cystoid macular edema, as well as a paracentral scotoma in the right eye. The diagnosis and follow-up of the case was done using visual field perimetry, optical coherence tomography (OCT), and ERG.

Results

Baseline ERG showed a marked decrease in the amplitudes of the scotopic and photopic responses and a delay of peak times mainly in the right eye. Mycophenolate mofetil at 2 g/day and oral prednisolone at 1 g/kg/day were administered with gradual tapering of the corticosteroids. After 5 months, there was a noticeable improvement in the visual acuity, macular edema in OCT, and an obvious increase in the amplitudes of the ERG associated with a decrease in peak times, particularly in the 30 Hz photopic 3.0 Flicker of the right eye.

Conclusion

This case report highlights the importance of the peak time and wave amplitudes of the 30 Hz photopic DA 3.0 Flicker as being a sensitive parameter in the diagnosis and follow-up of BSCR.

     

Contribution of retinal ganglion cells to the mouse electroretinogram

Purpose

To quantify the direct contribution of retinal ganglion cells (RGCs) on individual components of the mouse electroretinogram (ERG).

Methods

Dark- and light-adapted ERGs from mice 8 to 12 weeks after optic nerve transection (ONTx, n = 14) were analyzed through stimulus response curves for a- and b-waves, oscillatory potentials (OPs), positive and negative scotopic threshold response (p/n STR), and the photopic negative response (PhNR) and compared with unoperated and sham-operated controls, as well as to eyes treated with 6-cyano-7-nitroquinoxaline-2,3-dion (CNQX).

Results

We confirmed in mice that CNQX intravitreal injection reduced the scotopic a-wave amplitude at high flash strength, confirming a post-receptoral contribution to the a-wave. We found that ONTx, which is more specific to RGCs, did not affect the a-wave amplitude and implicit time in either photopic or scotopic conditions while the b-wave was reduced. Both the pSTR and nSTR components were reduced in amplitude, with the balance between the two components resulting in a shortening of the nSTR peak implicit time. On the other hand, amplitude of the PhNR was increased while the OPs were minimally affected.

Conclusion

With an intact a-wave demonstrated following ONTx, we find that the most robust indicators of RGC function in the mouse full-field ERG were the STR components.     

Development and preclinical evaluation of a new viewing filter system to control reflection and enhance dye staining during vitrectomy

Purpose

We developed a new artificial image enhancement system and evaluated its usefulness in controlling intraoperative reflection and enhancing of Brilliant Blue G (BBG) staining.

Methods

The system was composed of three kinds of filters (a polarizing filter, a blue-enhancing filter, and a sharp-cut filter Y) and attached to the inferior surface of the operating microscope. Twenty-seven post-mortem extracted porcine eyes were used for a series of examinations. We performed surgery using the 23G-vitrectomy system with a halogen light and xenon lights and compared the reduction of intraoperative reflection under air condition and visibility and BBG contrast with and without this system. The evaluation of images was calculated in CIE 1976 (L*, a*, b*) color space (CIELAB) carried out by ImageJ software. The transmission of each filter and absorbance of BBG was measured by a spectrophotometer. We measured spectral irradiance at each wavelength about each filter from each light source with a spectroradiometer.

Results

Under both light sources, intraoperative reflection was controlled using a polarizing (PL) filter or combination of filters under air condition. Evaluation of the value of L* within the cutter surface was changed by 37.8 % under the halogen light, and 61.6 % (averaged) under the xenon light with inserted filters versus no filter. The BBG intensity difference was obtained with sharp-cut Y filter under both light source and PL with blue enhancing filter under the halogen light using each L*, a*, b* parameter with statistically significant (p?<?0.01, 0.05). However, there was a relative decrease in the observation illuminance when the filter inserted according to the attenuation total spectral irradiance.

Conclusions

This system can reduce intraoperative reflections under the air condition and obtain an excellent BBG staining intensity induced by various light sources.     

Application of Thermo-setting Gel as Artificial Vitreous

Purpose

In this study, we produced a rabbit model and investigated the safety of intravitreous injection of a thermo-setting gel (TG) to determine whether TG can be used as artificial vitreous.

Methods

Ten male Japanese white rabbits were used. After performing vitrectomy in a unilateral eye, we injected 1?ml of WTG-127 into the vitreous cavity. The contralateral control eye was not given ophthalmic solution or surgery. Each eye was examined and intraocular pressure (IOP) and the electroretinogram (ERG) were evaluated. On day 28, all eyes were enucleated and examined.

Results

No abnormal findings and no elevation of IOP were observed. On the ERG, no significant difference in the latency and amplitude of either the a wave or b wave was observed. Histopathological examination of the retinal tissue showed no abnormalities. In the presence of a retinal tear, under the detached retina a drift of TG through the tear was observed in a few animals.

Conclusions

In a rabbit model, the safety of using an intravitreous injection of thermo-setting gel as artificial vitreous was confirmed by ophthalmoscopic, electrophysiological, and histological studies for a relatively short observation period. However, TG injection cannot be expected to provide a tamponade effect. Jpn J Ophthalmol 2005;49:491–496 © Japanese Ophthalmological Society 2005