The association between multifocal electroretinograms and OCT retinal thickness in retinitis pigmentosa patients with good visual acuity

'Transcorneal Electrical Stimulation Therapy May Have A Stabilization Effect on Multifocal Electroretinography for Patients with Retinitis Pigmentosa'

PURPOSE

To assess the effects of Transcorneal Electrical Stimulation (TES) on several measures of visual function in retinitis pigmentosa (RP).

METHODS

This prospective, randomized, fellow-eye-controlled study includes 30 eyes of 15 RP patients. Each patient's eyes were randomly selected as treatment(TE) and control eye(CE), and 30 minutes/week TES applied for six months. Patient evaluations were done before and after TES including comprehensive ophthalmological examination, visual fields, full-field and multifocal (mf-) electroretinography (ERG), microperimetry, and optical coherence tomography. All parameters were compared before and after TES and between TE and CE.

RESULTS

After TES, the mean signal amplitudes(MSA) in mf-ERG were stabilized in TE. MSA in CE decreased in every ring, reaching significance in fifth ring (847,15±393,94 and 678,77±282,66 nV, p=0.039, before and after TES, respectively). The changes in MSA of TE and CE were -0,38±295,53 and -185,15±332,62nV in second(p=0,046), 36,69±326,4 and -143,38±317,41nV in fourth(p=0,028), -17,46±333,07 and -168.38±297,14nV in fifth rings(p=0,046), respectively. The decrease in MSA between 2° to 20° midperipheral retina was significantly less in TE (-33,59±225,1nV) than CE (-205,56±345,1nV)(p=0,011). There were no siginificant changes in other parameters.

CONCLUSIONS

The progression in mf-ERG might be stabilized with TES. Further studies with larger sample sizes and longer follow-up are needed to conclude that TES reduces RP progression.

Neurodegeneration, Neuroprotection and Regeneration in the Zebrafish Retina

Neurodegenerative retinal diseases, such as glaucoma and diabetic retinopathy, involve a gradual loss of neurons in the retina as the disease progresses. Central nervous system neurons are not able to regenerate in mammals, therefore, an often sought after course of treatment for neuronal loss follows a neuroprotective or regenerative strategy. Neuroprotection is the process of preserving the structure and function of the neurons that have survived a harmful insult; while regenerative approaches aim to replace or rewire the neurons and synaptic connections that were lost, or induce regrowth of damaged axons or dendrites. In order to test the neuroprotective effectiveness or the regenerative capacity of a particular agent, a robust experimental model of retinal neuronal damage is essential. Zebrafish are being used more often in this type of study because their eye structure and development is well-conserved between zebrafish and mammals. Zebrafish are robust genetic tools and are relatively inexpensive to maintain. The large array of functional and behavioral tests available in zebrafish makes them an attractive model for neuroprotection studies. Some common insults used to model retinal disease and study neuroprotection in zebrafish include intense light, chemical toxicity and mechanical damage. This review covers the existing retinal neuroprotection and regeneration literature in the zebrafish and highlights their potential for future studies.

Ganglion cell-inner plexiform layer and retinal nerve fibre layer changes within the macula in retinitis pigmentosa: a spectral domain optical coherence tomography study

PURPOSE

To investigate how macular ganglion cell-inner plexiform layer (GCIPL) and retinal nerve fibre layer (RNFL) thicknesses within the macula change with retinitis pigmentosa (RP) severity.

METHODS

Spectral domain optical coherence tomography (SD-OCT) was used to examine 177 patients with RP and 177 normal controls. An optical coherence tomography (OCT) line scan was used to grade RP severity. Retinitis pigmentosa (RP) was categorized as more advanced if there was no identifiable inner segment ellipsoid (ISe) band (NISE) and as less advanced if an ISe band could be identified and peripheral loss of ISe was apparent (IISE). Ganglion cell-inner plexiform layer (GCIPL) and RNFL thicknesses were manually measured on OCT images and analysed. Pearson's correlation analyses were used to examine correlations between GCIPL thickness, RNFL thickness, visual acuity (VA) and visual field extent in patients and controls.

RESULTS

Ganglion cell-inner plexiform layer (GCIPL) was significantly thicker in IISE than in control eyes (p < 0.001), but significantly thinner in NISE than in IISE eyes (p < 0.001) in both horizontal and vertical OCT scans. Retinal nerve fibre layer (RNFL) was significantly thicker in eyes with IISE and NISE than in control eyes in both horizontal and vertical meridians (all p < 0.001). Ganglion cell-inner plexiform layer (GCIPL) thickness showed a weak positive correlation with vision, and RNFL thickness showed a weak negative correlation with vision and visual field extent.

CONCLUSION

Based on these results, the inner retina, including the GCIPL and RNFL, maintains its gross integrity longer than the photoreceptor layer in RP. Additionally, thickening of the inner retina may have some functional implications in patients with RP.

The assessment of macular electrophysiology and macular morphology in patients with vitiligo

PURPOSE

We aimed to analyze the electrophysiologic function and morphology of macula in vitiligo patients.

METHODS

Seventeen patients with vitiligo and 11 healthy subjects were studied. All participants underwent multifocal electroretinography (mfERG) and spectral domain optical coherence tomography (SD-OCT) evaluations. The mfERG (P1 mfERG responses central and peripheral) and retinal layer segmentation parameters (nine ETDRS subfields) were compared in vitiligo and control groups.

RESULTS

The mean P1 response amplitudes were significantly decreased in central and peripheral rings of the fovea in patients with vitiligo compared with controls (p = 0.002 and p = 0.006, respectively). There was a tendency toward a prolonged mean implicit time for both central and peripheral in patients with vitiligo compared to controls, however, with no statistical significance (p = 0.453 and p = 0.05, respectively). There was no statistically significant difference in all retinal layers thickness between two groups.

CONCLUSION

In patients with vitiligo, while photoreceptor segment preserved in SD-OCT, mfERG reduced showing potential decline in central retinal function. This study showed a potential decline in central retinal function in patients with vitiligo even if they have normal fundus appearance and SD-OCT findings.

Age-Dependent Morphologic Alterations in the Outer Retinal and Choroidal Thicknesses Using Swept Source Optical Coherence Tomography

Purpose

To evaluate the age-dependent morphologic alterations in the outer retina and choroid at the macula using swept-source optical coherence tomography (OCT).

Methods

Thirty eyes (30 normal subjects; average age, 49 years) were examined; five (age range, third-eighth decades of life) had refractive errors of ±2 diopters or less and no fundus abnormalities. An Early Treatment Diabetic Retinopathy Study (ETDRS) map of the outer retinal and choroidal thickness was constructed using swept-source OCT. The outer retinal and choroidal segmentation lines were drawn automatically, partially manually, within 6 millimeters of the macula.

Results

The mean outer retinal and choroidal thicknesses in the 6-millimeter-diameter circle were 145±13 and 236±68 microns, respectively. The choroidal thickness and age were negatively (r = -0.66, P<0.01) correlated; the outer retinal thickness and age were not correlated (r = -0.16, P = 0.39). The outer retinal and choroidal thicknesses in the ETDRS map were not correlated (r = -0.13, P = 0.49) within 1 millimeter but correlated (r = 0.32, P<0.01) within 6 millimeters.

Conclusions

The choroid thins with aging. The outer retina remains stable. Outer retina and choroid are correlated in the entire macula except for the center. ETDRS map can be useful for evaluation of the morphologic relationship between the outer retina and choroid.

The Structure-Function Relationship between Macular Morphology and Visual Function Analyzed by Optical Coherence Tomography in Retinitis Pigmentosa

Purpose. To evaluate the relationship between macular microstructures and visual function in retinitis pigmentosa (RP). Method. Fourier domain optical coherence tomography (FD-OCT) and Goldmann perimetry were used to examine 100 eyes of 100 RP patients. The preserved photoreceptor outer segment (PROS) length was measured at the horizontal and vertical high definition line scans. The PROS area was calculated from slab image and line scans simultaneously. The visual field area (VFA) was quantified. Each retinal thickness was measured: inner retina (IRT), outer retina (ORT), subfoveal choroidal thickness (SFCT), and central retinal thickness (CRT). Results. The PROS area values acquired differently were consistent. The VFA was related significantly to the CRT, ORT, PROS length (vertical and horizontal), and PROS area (line scan and slab image). Visual acuity was correlated with the CRT, ORT, IRT, PROS length (horizontal and vertical), and PROS area (line scan and slab image) significantly. Multiple linear regression analysis revealed that the PROS horizontal length and ORT were related to the VFA and visual acuity, respectively. Conclusion. Among the macular microstructures, the PROS horizontal length and the ORT were most correlated with VFA and visual acuity, respectively. However, SFCT is not related to visual function.

Contrast sensitivity and color vision in eyes with retinitis pigmentosa and good visual acuity: correlations with SD-OCT findings

BACKGROUND AND OBJECTIVE

To investigate the morphological substrate of the changes in visual function in eyes with retinitis pigmentosa and good visual acuity using spectral-domain optical coherence tomography (SD-OCT).

PATIENTS AND METHODS

A total of 30 eyes of 17 patients with retinitis pigmentosa and visual acuity of 20/40 or better underwent contrast sensitivity and color vision testing. The retinal thickness at the fovea and macula and the length of the photoreceptor inner/outer segment (IS/OS) junction were assessed by SD-OCT. Structural-functional correlations were investigated.

RESULTS

Contrast sensitivity correlated well with IS/OS length (Spearman r = 0.719, P < .001) and foveal thickness (r = 0.672, P < .001) and moderately with macular thickness (r = 0.422, P = .025). Moreover, color vision correlated significantly with IS/OS length (r = -0.725, P < .001) and foveal thickness (r = -0.661, P < .001).

CONCLUSION

In eyes with retinitis pigmentosa and good visual acuity, the structural changes observed on OCT scans correspond well to subtle measures of central visual function, complementary to visual acuity testing.

Association between multifocal electroretinograms, optical coherence tomography and central visual sensitivity in advanced retinitis pigmentosa

PURPOSE

To investigate the association between automated perimetry, multifocal electroretinogram (mfERG) and optical coherence tomography (OCT) measurements in patients with advanced retinitis pigmentosa (RP).

METHODS

Twenty-five patients with advanced RP were included. Central visual field sensitivity (VFS) was evaluated using an average of visual sensitivity value at central four test points during central 30-2 static automated perimetry. OCT imaging was conducted, and the inner and outer segment (IS/OS) line was classified into three groups: Group 1, absence; Group 2, partially intact; and Group 3, intact. Central retinal thickness (CRT) that is the retinal thickness of central 3.0 mm was also evaluated. Average amplitude and implicit time of N1 and P1 in ring 1 and 2 were measured on mfERG. Comparisons of VFS, mfERG and OCT among the three subgroups were performed following IS/OS integrity. Relationship among VFS, mfERG and CRT was evaluated by regression analysis.

RESULTS

Group 3 patients with an intact IS/OS line showed a better VFS, and amplitude of mfERG response than those of Group 1 and 2. VFS and amplitudes of mfERG were correlated significantly with CRT in linear regression analysis.

CONCLUSIONS

Disrupted IS/OS integrity was associated with visual dysfunction which was shown by decreased amplitude of mfERG response and reduced central VFS. CRT was significantly correlated with amplitude of mfERG response and central VFS. An eye with the more reduced CRT was associated with the worse amplitude of mfERG response and central VFS.

Cone dysfunctions in retinitis pigmentosa with retinal nerve fiber layer thickening

Purpose

To investigate whether or not thicker retinal nerve fiber layer (RNFL) in retinitis pigmentosa (RP) patients relates to functional abnormalities of the photoreceptors.

Methods

Optical coherence tomography-based RNFL thickness was measured by Stratus-3™ (Zeiss, Basel, Switzerland) optical coherence tomography and electroretinogram (ERG) recordings made using the RETI-port^® system (Roland, Wiesbaden, Germany) in 27 patients with retinitis pigmentosa and in 30 healthy subjects.

Results

Photopic ERG b-wave amplitude, cone ERG b-wave latency, 30 Hz flicker amplitude, and 30 Hz flicker latency had significant correlations to the RNFL-temporal (r = −0.55, P = 0.004, r = 0.68, P = 0.001, r = −0.65, P = 0.001, and r = −0.52, P = 0.007, respectively). Eyes with thicker RNFL (ten eyes) differed significantly from those with thinner RNFL (eight eyes) regarding cone ERG b-wave latency values only (P = 0.001).

Conclusion

Thicker RNFL in patients with retinitis pigmentosa may be associated with functional abnormality of the cone system.

Macular thickness and aging in retinitis pigmentosa

PURPOSE

This study was designed to analyze macular tomography in patients of different ages with retinitis pigmentosa (RP) and correlate their visual function with macular thickness, which was measured by optical coherence tomography.

METHODS

In all, 75 RP patients and 75 controls were stratified into three age groups and macular thickness was measured by optical coherence tomography. The tomography was subdivided into three circular zones, four quadrants, and nine areas for analysis. Ophthalmic examinations, which involved ophthalmoscopic examinations, dark adaptation tests, visual acuities, visual field examinations, electrooculography, and color sense discrimination tests, were performed.

RESULTS

Macular thickness of the RP patients decreased in the middle age group (45- to 55-year old), whereas the oldest group showed an increased thickness. The thickness of the outer inferior area remained virtually unchanged, whereas the thickness of the inner temporal area showed the most fluctuation with age. In terms of circular sections, the most dramatic changes in macular thickness were observed in the fovea, and the aging effect decreased outward to the outer ring. Furthermore, the thickness of the fovea was more important than the thickness of the inner ring and the outer ring for electrooculography, visual acuity, and color sense discrimination in RP patients.

CONCLUSIONS

In middle age RP patients, the macular thickness decreased, whereas an increased thickness was observed in patients older than 55 years. In addition, the inner temporal area was the most fragile, and the outer inferior area was the least affected in patients with RP.

The structure and function of the macula in patients with advanced retinitis pigmentosa

PURPOSE

To assess the structure and function of the macula in advanced retinitis pigmentosa (RP).

METHODS

Twenty-nine eyes of 22 patients with RP were compared against 17 control eyes. Time-domain optical coherence tomography (OCT) data were processed using OCTRIMA (optical coherence tomography retinal image analysis) as a means of quantifying commercial OCT system images. The thickness of the retinal nerve fiber layer (RNFL), ganglion cell layer and inner plexiform layer complex (GCL+IPL), inner nuclear layer and outer plexiform layer complex (INL+OPL), and the outer nuclear layer (ONL) were measured. Multifocal electroretinography (mfERG) was performed; two groups were formed based on the mfERG findings. Fourteen eyes had no detectable central retinal function (NCRF) on mfERG; detectable but abnormal retinal function (DRF) was present in the mfERG of the other 15 eyes.

RESULTS

The thickness of the ONL in the central macular region was significantly less in the NCRF eyes compared with that in both DRF eyes and controls. The ONL was significantly thinner in the pericentral region in both patient groups compared with that in controls, whereas the thickness of the GCL+IPL and INL+OPL was significantly decreased only in the NCRF eyes. The RNFL in the peripheral region was significantly thicker, whereas the thickness of the GCL+IPL and ONL was significantly thinner in both patient groups compared with that in controls.

CONCLUSIONS

The results are consistent with degeneration of the outer retina preceding inner retinal changes in RP. OCT image segmentation enables objective evaluation of retinal structural changes in RP, with potential use in the planning of therapeutic interventions and conceivably as an outcome measure.

Effects of luminance combinations on the characteristics of the global flash multifocal electroretinogram (mfERG)

PURPOSE

This study aims to ascertain the characteristics of the response triggered by the global flash multifocal electroretinogram (MOFO mfERG) under various combinations of global and focal flash luminance, and to determine the optimal conditions for this measurement.

METHODS

Ten normal subjects with mean age 23.2 yrs (+/- 1.14 yrs) were recruited for the MOFO mfERG measurement. The visual stimulation consisted of four video frames (stimulus frame with 103 scaled hexagonal focal flashes, followed by a dark frame, a global flash and then another dark frame). The focal and global flash intensities were varied independently for four levels (50, 100, 200 and 400 cd/m(2)). The subjects then underwent measurements with sixteen combinations of focal and global flash luminance. The direct component (DC) and induced component (IC) of the MOFO mfERG were grouped into central and peripheral regions for analysis.

RESULTS

The central and peripheral DC amplitude increased with the focal flash luminance under constant global flash luminance. Moreover, the proportion of the global flash and focal flash intensity was shown to be important to achieve an optimal IC response. When the ratio of global flash luminance to focal flash luminance (g/f ratio) was kept at about 2:1, the central and peripheral IC amplitude reached the peak value, and further increasing the global flash luminance would not enhance the IC response magnitude. The implicit time of both central and peripheral DC generally decreased with the increase of g/f ratio. However, the implicit time of central and peripheral IC increased with the g/f ratio.

CONCLUSION

The g/f ratio is important in the MOFO mfERG paradigm, since the DC and IC responses change with this ratio. In order to obtain both optimal DC and IC responses, a g/f ratio of 1:1 with focal flash luminance between 100 cd/m(2) and 200 cd/m(2) would be recommended. As the global flash mfERG paradigm is studying the interaction triggered by both flashes, the g/f ratio is a vital parameter for measurement in future studies.