In diabetic eyes, multifocal ERG reflects differences in function between the nasal part and the temporal part of the macula

Purpose

The purpose of the present study was to compare retinal function between the perifoveal nasal and perifoveal temporal areas of diabetic eyes using multifocalERG (mfERG).

Methods

We included 36 eyes from 27 patients with diabetes (age 58?±?14?years; duration of diabetes 13?±?9?years; HbA_1c 7.1?±?1.8%) and a control group with 18 eyes from 18 healthy subjects (age 57?±?11?years). Retinal thickness was assessed with optical coherence tomography (OCT) in the perifoveal areas corresponding to the summed nasal and temporal inner and outer areas. MfERG amplitude and implicit time were recorded from corresponding areas.

Results

Diabetic eyes showed lower mfERG amplitude in the nasal area than in the temporal area (14?±?6 vs 17?±?7?nV/deg²; p?p?=?0.005). In the control group, there were no significant differences between the two areas.

Conclusion

Diabetic eyes showed lower amplitude and longer implicit time in the nasal area than in the temporal, which might indicate that the nasal area is more vulnerable. These findings may be of importance for evaluation of diabetic maculopathy and outcome after laser treatment.     

Macular function assessed with mfERG before and after panretinal photocoagulation in patients with proliferative diabetic retinopathy

Purpose: To examine macular function and its correlation to macular thickness before and after panretinal photocoagulation for proliferative retinopathy in diabetic patients. Methods: Ten diabetic patients (aged 57 ± 10 years, diabetes duration 21 ± 10 years) treated with panretinal photocoagulation outside the great vascular arcade underwent multifocal electroretinography (mfERG) and optical coherence tomography (OCT) before and 6 months after treatment. When focal treatment in the macular region was performed prior to panretinal photocoagulation the investigations took place 3 weeks after this treatment but before the panretinal photocoagulation. One eye per patient was examined. Amplitudes and implicit times of the mfERG response were analyzed within the four innermost (27°) of the six concentric rings registered by the mfERG, which corresponds to the area measured by the OCT (Ø 3.5 mm). Results: Visual acuity was similar before and after photocoagulation, 1.0; 0.7–1.0 (md, range) versus 1.0; 0.6–1.0 (md, range). The mean values of the ring average amplitudes were reduced in the first and second, third and fourth concentric rings from foveola after photocoagulation, p= 0.001, p= 0.011 and p= 0.004, respectively. No change was seen in implicit time after treatment. OCT values were similar before and after photocoagulation. There was no correlation between retinal thickness assessed with OCT and amplitudes measured by the mfERG. Conclusion: In spite of unchanged values of retinal thickness and visual acuity, panretinal photocoagulation seems to cause a functional impairment in the adjacent untreated macula, shown by reduced amplitudes measured by the mfERG.     

Structural and functional outcomes after treatment of uveitic macular oedema: an optical coherence tomography and multifocal electroretinogram study

Background: The aim was to evaluate the correlation between the anatomical and functional outcomes before and after treatment of uveitic macular oedema. Methods: Thirty‐three eyes of 33 patients with uveitic macular oedema were included in the present study. Visual acuity (VA), optical coherence tomography (OCT) and multifocal electroretinogram (mfERG) were measured before and after treatment of the macular oedema. Correlation analyses between VA, OCT and mfERG parameters were performed. Results: The VA and mfERG measurements showed statistically significant improvement after treatment of the macular oedema (p < 0.01) and OCT‐measured central foveal thickness decreased significantly from 434 ± 135 µm before treatment to 267 ± 92 µm after treatment (p < 0.001). Correlation analyses showed that uveitic central foveal thickness before treatment was correlated with mfERG N1 response amplitude of area 1 (Spearman's r = ‐0.62, p < 0.001). VA (logMAR) after treatment had a negative correlation with the mfERG N1 response amplitude of area 1 (Spearman's r = ‐0.56, p = 0.001). Also, there was no correlation between the final VA and pre‐treatment OCT and mfERG measurements. Conclusion: This study deals with cystoid macular oedema associated with recurrent uveitis. In cystoid macular oedema, the value of mfERG before treatment is related to the central foveal thickness and VA. In contrast, after treatment the decrease of macular thickness is not always followed by an improvement of mfERG and VA. This supports the view that in uveitic macular oedema, the decrease in macular thickness after treatment may not be used as a predictor of improvement of macular function.     

玻璃体腔注射康柏西普治疗湿性年龄相关性黄斑变性的早期mfERG变化

目的：利用多焦视网膜电图(mfERG)评价玻璃体腔注射康柏西普的湿性年龄相关性黄斑变性(age-related macular degeneration,ARMD)患者视网膜功能的早期变化。

方法：经眼底荧光血管造影确诊为湿性ARMD患者接受玻璃体腔注射康柏西普眼用注射液(0.05mL/0.5mg),记录注射前及注射后1mo的最佳矫正视力及mfERG各环N1、P1波潜伏期及P1波振幅密度。

结果：共20例20眼患者纳入研究,平均LogMAR视力从注射前0.80±0.48提高到注射后0.65±0.50(P<0.001),环1平均振幅密度从注射前39.59±16.60nV/deg²提高到注射后的53.81±20.41nV/deg²(P=0.006),振幅密度的改变与视力的改变呈正相关(r=-0.776,P<0.001)。

结论：对于湿性ARMD患者玻璃体腔注射康柏西普短期内能改善黄斑中心凹的功能。     

Multifocal electroretinogram (mfERG) in patients with diabetes mellitus and an enlarged foveal avascular zone (FAZ)

Purpose To assess the relationship between foveal microcirculation and central retinal function in diabetic patients having both an enlarged foveal avascular zone (FAZ) and a preserved visual acuity (0.6 or better). Methods Twenty-five patients with diabetes type 1 or 2 with an enlarged FAZ (largest diameter > 650 μm) measured in fluorescein angiograms were examined with multifocal ERG (mfERG). The largest FAZ diameter, the FAZ area as well as the adjacent perifoveal intercapillary area (PIA), was calculated from the fluorescein angiogram. The retinopathy level was mild to preproliferative. There was no macular edema and no eye had previously been treated with photocoagulation. Results The mean FAZ diameter was 0.92 ± 0.17 mm and the mean summed area (FAZ and PIA) was 0.74 ± 0.24 mm². There was a significant correlation between increasing FAZ diameter and increasing implicit time of the innermost concentric rings and of the third concentric ring in the first order kernel of the mfERG (P = 0.03 and P = 0.008, respectively). An increasing summed area (FAZ and PIA) was correlated to increasing implicit time in the same areas of the mfERG (P = 0.005 and P = 0.026, respectively). No correlation was seen between the ischemic areas and the mfERG amplitudes. Conclusion A correlation between the ischemic areas and prolonged implicit time in the mfERG indicates that alterations in neuronal macular function due to ischemia might precede the deterioration of visual acuity.     

Tilted disc syndrome: an OCT and mfERG study

Purpose To evaluate retinal thickness and function in eyes with tilted disc syndrome with optical coherence tomography (OCT) and multifocal electroretinogram (mfERG). Methods Twenty-one eyes of 12 patients (4 males and 8 females) with tilted disc were studied with OCT3 and mfERG and compared with 40 eyes of 20 age and sex-matched control subjects. The thickness of the fovea and the thickness of retinal nerve fibre layer (RNFL) along a 3.4-mm-diameter circle centred on the optic nerve head were evaluated using OCT3. The macular cone function was tested by mfERG. Results The OCT-derived RNFL thickness was significantly decreased in the superior area of eyes with tilted disc with a mean value equal to 106.47 μm (SD 24.1). The mean response amplitude density of the fovea (11.75 nV/deg2) and parafovea (8.22 nV/deg2) was significantly lower in eyes with tilted disc than in normal eyes. Conclusion OCT and mfERG can be objective tools for assessing anatomical and functional damage of the macula. Our results suggest that in tilted disc syndrome even without visual impairment the optic nerve and the macula show dysfunction not visible by other means.     

Multifocal electroretinography in type 2 idiopathic macular telangiectasia

Background

To characterize the electroretinographic response of the macula by multifocal electroretinography (mfERG) in patients with type 2 idiopathic macular telangiectasia (MacTel).

Methods

A prospective study of mfERG in patients with type 2 MacTel was conducted from April 2009 to November 2009. mfERGs were recorded using a visual evoked response imaging system (MonElec2, Metrovision, Perenchies, France). The International Society for Clinical Electrophysiology of Vision (ISCEV) guidelines were followed. Patients with type 2 MacTel confirmed by fundus fluorescein angiography without subretinal neovascularisation were included. For recording purposes, 61 stimulus hexagonal elements were used. The first-order kernel mfERG responses were analyzed. Individual mfERG responses for the hexagons were grouped into concentric rings centered on the fovea for analysis (< 2, 5–10, 10–15 and >15°). Student’s t-test and Mann–Whitney U test and linear regression analysis was performed with STATA ver 11.1 (StataCorp, College Station , TX, USA).

Results

Twenty eight eyes of 14 patients and 20 eyes of ten normal controls were included in the study. The mean logMAR visual acuity of the patients was 0.51 (Snellen equivalent 20/63). The mean N1 amplitude (nv/deg²) of patients were significantly reduced compared to controls and were as follows: 8.91?±?14.00 vs 43.44?±?9.55 (p?<?0.0001) in less than 2°, 9.24?±?10.47 vs 22.00?±?3.87 (p?<?0.0001) in 5–10°, 8.57?±?10.02 vs 15.24?±?1.89 (p?<?0.0001) in 10–15°, and 7.03?±?6.52 vs 12.47?±?2.62 in?>?15° (p?<?0.001). The mean P1 amplitude (nv/deg²) was also significantly reduced in patients compared to controls and was as follows: 27.66?±?37.44 vs 96.20?±?12.41 (p?<?0.0001) in less than 2°, 22.61?±?19.38 vs 53.78?±?9.79 (p?<?0.0001) in 5–10°, 18.75?±?20.21 vs 35.22?±?4.16 (p?<?0.001) in 10–15°, and 17.10?±?12.54 vs 25.71?±?3.93 (p?<?0.001). The implicit time of N1 and P1 were also delayed significantly in all the rings. The mean central foveal thickness assessed by optical coherence tomography (OCT) scan was 84.78?±?45.12 μm. There was poor correlation between mfERG amplitudes or implicit times with either the visual acuity or OCT central thickness.

Conclusion

mfERG showed significant reduction in amplitudes and implicit times of the waveforms in patients with type 2 MacTel in all the rings, suggesting a more generalized affection of the macula. The maximum reductions were seen in the <2^o rings. Although there was poor correlation between the visual acuity and the amplitudes a of the waveforms, mfERG is a useful investigative modality for functional assessment of macula in type 2 MacTel patients.     

光相干断层扫描连续监测大鼠慢性高眼压模型视盘神经纤维厚度变化

目的:用光相干断层扫描（OCT）连续观测大鼠慢性高眼压模型视 盘神经纤维层（RNFL）厚度的变化。 方法:选用Wistar大鼠48只，随机分为3组，每组16只鼠32只眼 ，右眼为激光光凝眼，左眼为对照眼。用波长为532 nm氩激光在全麻下光凝右眼小梁网，引 起眼压 慢性、中等程度升高并观测眼压变化。眼压升高后第3、6、9周时用OCT做视盘线性扫描， 计算机自动测量视盘RNFL厚度，然后处死大鼠，将每组8只大鼠右眼做光学切片行组织学 测量RNFL厚度，将另外8只大鼠右眼做全视网膜铺片甲苯胺蓝染色，记数视网膜神经元细胞 密度，将结果进行比较分析。 结果:激光光凝后大鼠眼压缓慢、中等程 度升高，在第3、6、9 周时光凝眼眼压分别比对照眼眼压为显著升高，差异有统计学意义(P＜0.001)。 OCT检查结果显示在3、6、9周时大鼠光凝眼视盘RNFL厚度分别小于对照眼，差 异有统计学意义（P＜0.05）。处死大鼠后组织学测量RNFL厚度，在3、6、9周时，光 凝眼为（64.38±6.54）、（51.47±6.4）、（42.10±6.10）μm，对照眼厚度为（76.23±6.78）、（78.64±6.15）、（77.64±6.63）μm。将两种方法测 得RNF L厚度值进行回归分析，两者变化趋势一致，相关系数(R=0.932，P＜0.001)。全视网 膜铺片甲胺蓝染色结果显示两组视网膜神经元细胞（RGC）密度值差异有统计学意义（P＜0.0 5）。 结论:激光光凝大鼠小梁可以成功建立大鼠慢性高眼压模型；OCT对大鼠慢性高眼压模型视盘RNFL厚度的测量与 在光学显微镜下的测量值变化趋势一致，相关性好；OCT可以连续活体监测大鼠慢性高眼压 模型视盘神经纤维厚度变化，从而了解大鼠青光眼视神经病变的进展。     

Variability in photocoagulation treatment of diabetic macular oedema

Purpose: To establish whether differences in the assessment of diabetic macular oedema (DME) with either optical coherence tomography (OCT) or stereoscopic biomicroscopy lead to variability in the photocoagulation treatment of DME. Methods: The differences in the assessment of DME with either OCT or stereoscopic biomicroscopy were analysed by calculating the surface areas and the overlap of retinal thickening. Photocoagulation treatment plans of retinal specialists were compared by evaluating the number and location of planned laser spots. Results: The threshold for and dosage of photocoagulation differ depending upon whether the basis of retinal thickness diagnosis is clinical observation or OCT. The overlap in laser spot location based on the assessment of DME with OCT or biomicroscopy averages 51%. Among retinal specialists, the treatment plans differed in the laser spot count by six‐ to 11‐fold. Conclusion: Diabetic macular oedema photocoagulation treatment threshold and dosage of laser spots differ depending on whether thickness assessments are based on stereoscopic slit‐lamp biomicroscopy or OCT. In addition, retinal specialists differed in the number and placement of planned laser spots even when given identical information concerning DME and treatable lesions. This variability in the photocoagulation treatment of DME could lead to differences in patient outcome and laser study results.     

In diabetic retinopathy, foveal thickness of 300 μm seems to correlate with functionally significant loss of vision

Purpose To study the relationship between foveal thickness assessed by optical coherence tomography (OCT) and foveal function measured with multi focal electroretinography (mfERG) in patients with non-proliferative diabetic retinopathy, and with no previous laser treatment. Methods Twenty-six eyes from 18 diabetic patients (13 men), aged 59 years, (range 28–79 years), diabetes duration 15 years, (range 2–27 years), with a macular thickness between 200 and 600 μm were evaluated by mfERG, visual acuity (ETDRS score) and OCT. Mean amplitudes and implicit times of the mfERG responses were analyzed within the four innermost (14 degrees) of the six concentric rings. For comparison with the results from the OCT (diameter of measured area = 6 mm) we analyzed the summed response from the first and second ring (central zone), corresponding to the central area of the OCT. The third(zone 2) and fourth (zone 3)of the four innermost of the six concentric rings measured by the mfERG corresponding to the second and third area of OCT. Results An increased macular thickness in the central area of the OCT correlated to reduced amplitudes (r = −0.541; P = 0.004) and prolonged implicit times (r = 0.548; P = 0.004) in the central zone of the mfERG, and inversely correlated with visual acuity, −0.49; P = 0.045. Retinal thickness in the second area was correlated to prolonged implicit times in the second mfERG zone (r = −0.416; P = 0.034). No correlations were found for the third area of the OCT. When macular thickness exceeded 300 μm the decrease of amplitudes and prolonged implicit times, measured by mfERG, seemed to be more pronounced. Conclusion In conclusion increased macular thickness is correlated with reduced amplitudes and prolonged implicit times on the mf ERG and worse visual acuity.     

中心性浆液性脉络膜视网膜病变OCT与mfERG图像的相关性

目的利用光学相干断层扫描（OCT）与多焦视网膜电图（mfERG）分析中心性浆液性脉络膜视网膜病变（csc）患者的OCT与mfERG图像的关系。方法横断面研究。应用德国CarlZeissCirrusHD-OCT及美国EDI VERIS Science^TM4．9视诱发反应图像系统对40只急性期CSC眼（40例）进行检查。将CSC患者OCT黄斑厚度图三个环的视网膜平均厚度与相对应的多焦视网膜电图（mfERG）的1＋2环、3环、4环的N1、P1波的平均反应密度和峰时间进行比较,并将黄斑区体积、总的黄斑中心凹的厚度、视网膜下液高度、视网膜下液范围和中心凹神经上皮厚度与mfERG6个环的N1、P1波反应密度和潜伏期比较分析。采用Spearman秩相关进行数据分析。结果CSC患者OCT内环、中环、外环的视网膜平均厚度与mfERG1＋2环、3环、4环的N1、P1波的峰时间呈正相关。黄斑区体积、总的黄斑中心凹的厚度、视网膜下液高度和视网膜下液范围与mfERG的N1、P1波反应密度和峰时间有显著的相关性。结论CSC患者的黄斑平均视网膜厚度及积液情况与mfERG之间有一定的相关性,可用OCT测量黄斑区视网膜下液的积液量,尤其是用积液范围来评估黄斑区视网膜功能的改变。OCT与mfERG的检测可以综合评价CSC患者的形态与功能的变化。     

Correlations among metamorphopsia test scores,optical coherence tomography findings and multifocal electroretinogram responses in epiretinal membrane patients

Purpose

To quantify metamorphopsia with a novel objective method in patients with epiretinal membrane (ERM) and to compare the relationships among metamorphopsia scores, spectral-domain optical coherence tomography (OCT) findings, and multifocal electroretinogram (mfERG) results.

Methods

This study included 52 eyes of 52 patients with idiopathic ERM who underwent comprehensive ophthalmologic examinations, including measurement of best-corrected visual acuity (BCVA), OCT, and mfERG. The degree of metamorphopsia was quantified using MonPack One® (Metrovision, Perenchies, France). On the topographic map of the early treatment diabetic retinopathy (ETDRS) grid, retinal thickness in the central, superior, inferior, nasal, and temporal subfields were measured, and metamorphopsia scores for each corresponding subfield were also obtained. The amplitudes and implicit times of mERG were elicited from each subfield. Then, the correlations among metamorphopsia scores, OCT findings, and mfERG responses were analyzed.

Results

The mean age of the patients was 65.3?±?18.5 y, and the average metamorphopsia score of the individual subfields was 2.03?±?1.18. Initial BCVA was 0.50?±?0.12 logMAR, but there was no significant correlation between metamorphopsia scores and BCVA. The metamorphopsia scores from the central subfields showed significant correlations with central retinal thickness (CRT) (p?=?0.001). The mean metamorphopsia scores in the central subfield showed a significant relationship with the mean N1 and P1 amplitudes (p?=?0.001, p?=?0.048, respectively), while no relationship was observed between metamorphopsia scores and mfERG amplitudes in other subfields.

Conclusions

The degree of metamorphopsia in patients with ERM could be objectively quantified in each subfield using a novel metamorphopsia test. The metamorphopsia scores were significantly correlated with retinal thickness, especially at the central subfields, and the scores in the central subfields were significantly correlated with the N1 and P1 amplitudes of mfERG. Thus, the metamorphopsia test can be a useful method to evaluate metamorphopsia symptoms for patients with ERM.

     

Functional and anatomical results after a single intravitreal Ozurdex injection in retinal vein occlusion: a 6‐month follow‐up – The SOLO study

Purpose:  To evaluate the efficacy of intravitreal dexamethasone implants in eyes with cystoid macular oedema (CME) secondary to branch retinal vein occlusion (BRVO) or central retinal vein occlusion (CRVO) in the clinical everyday practice, examine the effects of early retreatment and compare the results with the GENEVA study. Methods:  The charts of 102 patients (102 eyes) with CME secondary to BRVO (n = 54) or CRVO (n = 48) treated with Ozurdex at 8 centres were retrospectively reviewed. The patients were examined monthly over a 24‐week period. Slit‐lamp biomicroscopy, measurement of best‐corrected visual acuity (BCVA) and measurement of the central retinal thickness (CRT) with spectral‐domain optical coherence tomography (SD‐OCT) were performed at baseline and at every follow‐up examination. With progression of the disease (loss of one line or increased central retinal thickness (CRT) of 150 μm), a reinjection of Ozurdex or anti‐VEGF was offered. Additional supplementing sectorial or panretinal laser photocoagulation was considered based on the individual status of the retina. Results:  In the BRVO group, the median BCVA was 0.6 logMAR (Snellen equivalent of 0.25) at baseline and improved to 0.4 logMAR (Snellen equivalent of 0.40) after 4 weeks, 0.3 logMAR (Snellen equivalent of 0.50) after 8 weeks, 0.4 logMAR (Snellen equivalent of 0.40) after 12 weeks, 0.5 logMAR (Snellen equivalent of 0.32) after 16 weeks, 0.4 logMAR (Snellen equivalent of 0.40) after 20 weeks and 0.45 logMAR (Snellen equivalent of 0.35) after 24 weeks. The mean CRT was 559 ± (SD) 209 μm at baseline and it decreased to 335 ± 148 μm after 4 weeks, 316 ± 137 μm after 8 weeks, 369 ± 126 μm after 12 weeks, 407 ± 161 μm after 16 weeks, 399 ± 191 μm after 20 weeks and 419 ± 196 μm after 24 weeks. In the CRVO group, the median BCVA was 0.7 logMAR (Snellen equivalent of 0.20) at baseline and improved to 0.4 logMAR (Snellen equivalent of 0.40) after 4 weeks, 0.4 logMAR (Snellen equivalent of 0.40) after 8 weeks, 0.6 logMAR (Snellen equivalent of 0.25) after 12 weeks, 0.6 logMAR (Snellen equivalent of 0.25) after 16 weeks, 0.5 logMAR (Snellen equivalent of 0.32) after 20 weeks and 0.52 logMAR (Snellen equivalent of 0.30) after 24 weeks. The mean CRT at baseline was 740 ± 351 μm and it decreased to 419 ± 315 μm after 4 weeks, 352 ± 261 μm after 8 weeks, 455 ± 251 μm after 12 weeks, 497 ± 280 μm after 16 weeks, 468 ± 301 μm after 20 weeks and 395 ± 234 μm after 24 weeks. The BCVA improvement was statistically significantly better (p < 0.05) compared with baseline in both groups at every follow‐up visit. The mean CRT maintained significantly better when compared with baseline in both groups at all follow‐up visits. Early reinjection was indicated in BRVO in 40.7% after 17.5 ± 4.2 weeks and in CRVO in 50% after 17.68 ± 4.2. Six eyes (11%) with BRVO received a sectorial laser photocoagulation at a mean interval of 22 ± 5.0 weeks. Seven eyes (15%) with CRVO received a panretinal laser photocoagulation after a mean interval of 18 ± 7.0 weeks. The BCVA improvement and the mean CRT reduction were statistically significant (p < 0.05) compared with baseline in both groups at every follow‐up visit. Conclusions:  Dexamethasone intravitreal implant resulted in a significant improvement of the BCVA and reduction of CME in patients with BRVO or CRVO. Early retreatment after 16 weeks instead of 24 weeks, like in the GENEVA study, was indicated in 50% to stabilize the improved functional and anatomical results.     

Foveal amplitudes of multifocal electroretinograms are larger following full-field electroretinograms

Purpose

The clinical standards for multifocal electroretinograms (mfERG) call for adaption to normal room lighting before the mfERG begins. They specify that any assessments where bright lights are used, should be done after the mfERG to prevent excess stimulation of retinal cells. However, full-field electroretinograms (FFERG) are performed prior to mfERGs in some clinical settings. It is unclear from the literature whether the FFERG has an impact on the mfERG. This study seeks to examine the effect of the FFERG on the mfERG when performed sequentially.

Methods

Thirty young healthy subjects (age 27.1?±?3.5 years) were included. Patients reported for two visits and were fully dilated at both visits. At visit one, a FFERG was recorded (VERIS 6.2) using our clinical protocol which includes an ISCEV standard flash sequence; each flash condition was repeated 4–6 times. Following the FFERG, an mfERG was recorded using a 4-min m-sequence at near 100% contrast. At visit two, only the mfERG was recorded. A Burian–Allen contact lens electrode filled with celluvisc was used for all recordings. The two mfERGs were compared for foveal, peripheral, and overall implicit time (IT) and amplitudes (amp). Paired t tests were used to evaluate the data. Coefficient of variation and Bland–Altman analysis was also reported for this patient group.

Results

There was a small but statistically significant difference in foveal amplitudes (amp) (p?=?0.004) wherein the amp was larger following the FFERG stimuli. The mean difference was 11.1 nV/deg² (100.9 nV vs 89.8 nV). There was no difference in foveal IT (p?=?0.66). There was no difference in overall IT or amp when averaging the entire eye (p?=?0.44 amp and p?=?0.54 IT) or just evaluating the periphery (p?=?0.87 amp and p?=?0.051 IT). Bland–Altman analysis found a coefficient of repeatability overall was 1.57 ms (IT) and 10.7 nV/deg² (amp).

Conclusions

The difference in foveal amplitude is likely the result of a small long-term cone adaptation, but further studies are needed. While it is statistically significant, the small difference is unlikely to be clinically important. These results should help increase clinical confidence in mfERG results when recorded following a FFERG.

     

Optical coherence tomography and vessel diameter changes after intravitreal bevacizumab in diabetic macular oedema

Purpose: To assess the effect of intravitreal bevacizumab on diabetic macular oedema (DMO) and retinal vessel calibres. Methods: We performed a consecutive case series study in which 10 consecutive eyes with diffuse DMO, two of which had not previously been treated, received an intravitreal injection of bevacizumab 1 mg, which was followed by two more injections at 6‐week intervals. Fundus photography and optical coherence tomography (OCT) were carried out at baseline immediately before injection and at 1, 2.5 and 4 months after the first injection. Outcome measures were best corrected visual acuity (BCVA) in Early Treatment Diabetic Retinopathy Study letters, macular volume, foveal subfield thickness and vessel diameter measurement. Results: Intravitreal administration of bevacizumab was followed by a mean increase in BCVA of 7.3 ± 17 (mean ± standard deviation) letters between baseline and month 4, which was 1 month after the last injection (p < 0.0001). This was accompanied by a reduction in mean macular volume from 9.90 ± 1.9 mm³ to 8.96 ± 2.4 mm³ (p = 0.002) and in foveal subfield thickness from 447 ± 117 μm to 388 ± 117 μm (p = 0.03). Two eyes with early proliferative diabetic retinopathy lost all signs of proliferation without any evidence of fibrosis. Although there was a trend towards vasoconstriction, the changes in vessel diameters (arteries and veins) after 4 months of intravitreal Avastin injection were not statistically significant (p = 0.9 and p = 0.17, respectively). Foveal thickness in non‐injected fellow eyes with DMO changed from 428 ± 153 μm at baseline to 383 ± 151 μm at 4 months (p = 0.1), which did not reach statistical significance. Conclusions: Intravitreal bevacizumab 1 mg every 6 weeks was followed by a moderate reduction in DMO without normalization of foveal and macular thickness. Our observations suggest that a larger study where patients are examined sooner after injection is needed to elucidate the potential relationship between changes in retinal vessel diameters and thickness changes in DMO.     

Corneal thickness mapping by 3D swept‐source anterior segment optical coherence tomography

Purpose: To assess accuracy and repeatability of central corneal thickness (CCT) measurements obtained by swept‐source anterior segment optical coherence tomography (AS‐OCT), spectral‐domain retinal OCT with corneal module and ultrasound pachymetry (USP), and to assess repeatability of pachymetric mapping with AS‐OCT. Methods: 50 healthy volunteers were recruited. A single, experienced operator analysed the right eye of each participant twice in the same session with AS‐OCT (‘corneal map’ routine), retinal OCT and USP. CCT measurements were compared using repeated‐measures analysis of variance, Bonferroni test, Pearson correlation and Bland‐Altman plots. Repeatability of thickness maps and CCT measurements were assessed using Alpha of Cronbach, intraclass correlation coefficient (ICC) and coefficient of repeatability. Results: Mean CCT ± SD was 540 ± 28.9 μm for AS‐OCT, 544 ± 29.5 μm for retinal OCT and 549.3 ± 31.7 μm for USP; the differences were statistically significant (p < 0.01). CCT measurements obtained with the three instruments were highly correlated: r was 0.965 for AS‐OCT/USP, 0.962 for retinal OCT/USP and 0.984 for AS‐OCT/retinal OCT comparison. The repeatability of CCT measurements was higher for AS‐OCT than for the other devices (p < 0.001). Repeatability of pachymetric maps was excellent (ICC = 0.999). Conclusions: Pachymetric maps by swept‐source AS‐OCT showed excellent repeatability. CCT measurements obtained by AS‐OCT, USP and retinal OCT were highly correlated although not identical.     

The spatial resolution of the porcine multifocal electroretinogram for detection of laser‐induced retinal lesions

Purpose: This study aimed to investigate the spatial resolution of a porcine multifocal electroretinogram (mfERG) protocol by testing its ability to detect laser‐induced retinal lesions. Furthermore, we wanted to describe time‐dependent changes in implicit time and amplitude of the different mfERG peaks after laser‐induced retinal damage. Methods: Three pigs underwent a three‐port pars plana vitrectomy, followed by laser photocoagulation of different lesion sizes within the visual streak. In an additional six non‐vitrectomized pigs, we studied changes in mfERG signals with time after a uniform laser photocoagulation within the visual streak. The animals were evaluated with mfERG 1 and 6 weeks after treatment. After the last mfERG examination, selected eyes were processed for histological examination. Results: The size of the smallest lesion detected was approximately 1/4 of the longest diameter of the optic disc (LDOD) measured in pixels. When analysing the uniform lesions we found that signals deriving from the centre of the laser lesions were characterized by a significant reduction in the amplitude of all three peaks after 1 week of observation. After 6 weeks, the amplitudes of P1 and N2 were still significantly reduced. The implicit times were unaffected by laser treatment in the acute phase. After 6 weeks only P1 was significantly delayed. Conclusion: We have determined the spatial resolution of the mfERG in the porcine retina to be smaller than or equal to the area of two adjacent hexagons, corresponding to a width of approximately 288 pixels or 1.2 mm. Laser lesions of uniform size resulted in a significant reduction of the amplitudes 1 and 6 weeks after treatment.     

Multifocal ERG findings in carriers of X-linked retinoschisis

Purpose To determine whether retinal dysfunction in obligate carriers of X-linked retinoschisis (XLRS) could be observed in local electroretinographic responses obtained with the multifocal electroretinogram (mfERG). Methods Nine obligate carriers of XLRS (mean age, 46.2 years) were examined for the study. Examination of each carrier included an ocular examination and mfERG testing. For the mfERG, we used a 103-scaled hexagonal stimulus array that subtended a retinal area of approximately 40° in diameter. The amplitudes and implicit times in each location for the mfERG were compared with the corresponding values determined for a group of 34 normally-sighted, age-similar control subjects. Results Mapping of 103 local electroretinographic response amplitudes and implicit times within a central 40° area with the mfERG showed regions of reduced mfERG amplitudes and delayed implicit times in two of nine carriers. Conclusions The mfERG demonstrated areas of retinal dysfunction in two carriers of XLRS. When present, retinal dysfunction was evident in the presence of a normal-appearing fundus. Multifocal ERG testing can be useful for identifying some carriers of XLRS.     

"Light" versus "classic" laser treatment for clinically significant diabetic macular oedema

AIM: To compare the effectiveness of "light" versus "classic" laser photocoagulation in diabetic patients with clinically significant macular oedema (CSMO). METHODS: A prospective randomised pilot clinical trial in which 29 eyes of 24 diabetic patients with mild to moderate non-proliferative diabetic retinopathy (NPDR) and CSMO were randomised to either "classic" or "light" Nd:YAG 532 nm (frequency doubled) green laser. "Light" laser treatment differed from conventional ("classic") photocoagulation in that the energy employed was the lowest capable to produce barely visible burns at the level of the retinal pigment epithelium. Primary outcome measure was the change in foveal retinal thickness as measured by optical coherence tomography (OCT); secondary outcomes were the reduction/elimination of macular oedema on contact lens biomicroscopy and fluorescein angiography, change in visual acuity, contrast sensitivity, and mean deviation in the central 10 degrees visual field. Examiners were masked to patients' treatment. RESULTS: 14 eyes were assigned to "classic" and 15 were assigned to "light" laser treatment. At 12 months, seven (50%) of 14 eyes treated with "classic" and six (43%) of 14 eyes treated with "light" laser had a decrease of foveal retinal thickness on OCT (p = 0.79). A comparison of reduction/elimination of oedema, visual improvement, visual loss, change in contrast sensitivity, and mean deviation in the central 10 degrees showed no statistical difference between the groups at 12 months (p>0.05 for all groups). CONCLUSIONS: This study suggests that "light" photocoagulation for CSMO may be as effective as "classic" laser treatment, thus supporting the rationale for a larger equivalence trial.     

The predictive value of optical coherence tomography after grid laser photocoagulation for diffuse diabetic macular oedema

Purpose: To assess the predictive value of optical coherence tomography (OCT) mapping of retinal thickness and intraretinal morphological changes after macular grid for diffuse diabetic macular oedema (DMO). Methods: We carried out a prospective, non‐controlled, case series study, in which 28 consecutive eyes with previously untreated diffuse DMO underwent fundus photography and OCT at baseline and at 1, 3 and 6 months after treatment. Results: Macular photocoagulation was followed by a significant reduction in retinal thickness in the foveal centre (? 80 μm) and in the foveal subfield (? 65 μm) from baseline to 6 months (p < 0.01). The bulk of the reduction in retinal thickness and macular volume was manifest after 1 month. No significant change in retinal thickness occurred from 1 to 3 months or from 1 to 6 months in any macular subfield (p > 0.05). The relative decrease in retinal thickness at 6 months was highest in the foveal centre (? 22%), followed by the foveal region (? 18%), the inner parafoveal region (? 8%), and the outer parafoveal region (? 2%). Thus, the effect of photocoagulation on retinal thickness decreased with increasing eccentricity (p < 0.025). Overall, there was no statistically significant change in best corrected visual acuity (BCVA) between baseline and follow‐up (p < 0.05), but changes in foveal subfield thickness and changes in VA were highly correlated (r = 0.66, p < 0.0001). Visual outcome (final BCVA) and final foveal subfield thickness at 6 months were correlated with the pattern of intraretinal morphological changes at baseline (Spearman’s correlation coefficient r = ? 0.41, p = 0.03 and r = 0.45, p = 0.02, respectively). In addition, visual outcome (final BCVA) and final foveal subfield thickness at 6 months were correlated with baseline foveal thickness (Spearman’s correlation coefficient (r = ? 0.37, p = 0.05 and r = 0.5, p = 0.01, respectively). Conclusions: It seems that the 1‐month time‐point after macular laser treatment is a critical point for establishing the outcome of this modality of management of DMO. Baseline OCT mapping of intraretinal fluid accumulation patterns and foveal thickness can help to predict the final visual outcome and final foveal thickness, but not the absolute change in either of these parameters after macular laser therapy.