Pattern visual evoked potential and foveal sensitivity in amblyopia

PURPOSE

Amblyopic eyes show impaired visual functions such as poor visual acuity and reduced foveal sensitivity. The purpose of this study was to determine the association between foveal threshold and visual evoked potentials (VEP) in strabismic and anisometropic amblyopia.

METHODS

Forty-five subjects (age range: 7-28 years, 43.3% female) including 15 strabismic and 15 anisometropic amblyopes, and 15 age-similar control subjects participated in this study. Each subject had pattern visual evoked potentials and foveal threshold recorded in each eye using RetiScan (Roland Consult, Germany) and Humphrey Visual Field Analyzer II (HFA II; Carl Zeiss Meditec Inc., Dublin, CA), respectively. These outcomes were compared among the amblyopic eyes, their fellow eyes, and the control eyes.

RESULTS

Compared to the amblyopic eyes (Mean ± SD: 33.4 ± 3.48 dB), the foveal threshold was higher in fellow eyes (37.0 ± 2.04 dB, p = 0.0002) and in control eyes (38.7 ± 0.96 dB, p < 0.0001). Strabismic amblyopes had a lower foveal threshold than anisometropic amblyopes (31.8 ± 3.86 vs. 35.0 ± 2.17 dB, p = 0.005). Relative to the P100 peak time in fellow eyes (1° checks:116.1 ± 9.00 ms; 0.25° checks:118.8 ± 5.67 ms), amblyopic eyes had delayed P100 peak times for both 1° (122.7 ± 11.4 ms, p < 0.0001) and 0.25° (130.4 ± 11.2 ms, p < 0.0001) check sizes. There were also significant differences in P100 peak time between amblyopic and control eyes (1°:122.7 ± 11.4 vs.112.4 ± 5.01 ms, p = 0.15; 0.25°:130.4 ± 11.2 vs.113.9 ± 5.71 ms, p < 0.0001) and between fellow and control eyes (0.25°:118.8 ± 5.67 vs.113.9 ± 5.71 ms, p = 0.009). Amblyopic eyes exhibited lower N75-P100 amplitudes than fellow eyes (1°:12.6 ± 7.96 vs.15.9 ± 8.82 µV, p = 0.01; 0.25°:10.6 ± 6.11 vs. 15.8 ± 10.6 µV, p = 0.001) and control eyes (0.25°: p = 0.0008). Foveal threshold correlated negatively with P100 peak time (1°: r = -0.45, p = 0.002 and 0.25°: r = -0.58, p < 0.0001) and positively with N75-P100 amplitude responses (1°: r = 0.42, p = 0.004 and 0.25°: r = 0.52, p = 0.002).

CONCLUSIONS

Amblyopic eyes showed reduced pattern VEP amplitudes and delayed peak times with significant associations with the foveal sensitivity. However, the VEP measures overlapped extensively between amblyopic and control eyes with no apparent criterion value for optimal discrimination, suggesting that foveal sensitivity might be a better discriminator of amblyopia than pattern VEP.

Functional evaluation with microperimetry in large idiopathic macular holes treated by a free internal limiting membrane flap tamponade technique

Background

Free internal limiting membrane (ILM) flap tamponade technique is an alternative choice for treating large idiopathic macular holes (IMHs). However, the functional recovery related to this surgical approach is not well-characterized. This study aimed to evaluate morphological and microperimetric outcomes 6 months after free ILM flap tamponade technique for large IMHs.

Methods

Twenty-two patients (22 eyes) with large IMHs (minimal diameter > 400 μm) were retrospectively enrolled in this study. All patients underwent 23-gauge pars plana vitrectomy with ILM peeling and free ILM flap tamponade procedures. Snellen best-corrected visual acuity (BCVA), optical coherence tomography (OCT), and MP-1 microperimetry were measured at baseline and 6 months after surgery. Associations of postoperative BCVA with retinal sensitivity were detected.

Results

Macular hole closure was achieved in 21 eyes (95.5%). Dislodgement of free ILM flap was found in non-closed eye. Mean logMAR BCVA improved from 1.10 ± 0.33 at baseline to 0.67 ± 0.32 at 6 months postoperatively (P < 0.001). The mean overall macular sensitivity and foveal fixation stability increased respectively from 8.58 ± 3.05 dB and 65.64 ± 17.28% before surgery to 11.55 ± 2.72 dB and 78.59 ± 13.00% at 6 months after surgery (P < 0.001). The mean change in foveal sensitivity (within 2°) was significantly greater than the change achieved for peri-foveal sensitivity (2° to 10°) by 1.50 ± 2.62 dB (P = 0.014). Linear regression analysis showed that postoperative logMAR BCVA was significantly associated with duration of symptom (B = 0.063, P = 0.001), preoperative logMAR BCVA (B = 0.770, P = 0.000), preoperative peri-foveal (B = − 0.065, P = 0.000) and foveal sensitivity (B = − 0.129, P = 0.000). Moreover, multiple regression model revealed that preoperative foveal sensitivity was independently associated with postoperative logMAR BCVA (B = − 0.430, P = 0.040).

Conclusions

Vitrectomy combined with ILM peeling and free ILM flap tamponade technique results in effective morphological and functional recovery for large IMHs. Preoperative foveal sensitivity might be a prognostic indicator for postoperative BCVA.

[Sensibilidad foveal en ojos con edema macular diabético con y sin engrosamiento temporal perifoveal]

Background

Visual improvement after photocoagulation in focal diabetic macular edema is more frequent when temporal perifoveal area is not affected; functional status before treatment could be worse in eyes with perifoveal temporal thickening. The correlation between visual acuity and foveal sensitivity (usually significant), would allow to compare macular function.

Objective

To compare the correlation between retinal sensitivity and visual acuity in eyes with diabetic macular edema, with and without temporal perifoveal thickening.

Method

Non-experimental, retrospective, comparative, cross-sectional study in type 2 diabetics with macular edema. The correlation between foveal sensitivity and visual acuity was compared in eyes without temporal perifoveal thickening (group 1) and eyes with it (group 2). Multiple regression analysis was used to identify the contribution of foveal sensitivity to the changes of visual acuity; other variables were: center point thickness, center field thickness, temporal perifoveal thickness and macular volume.

Results

60 eyes in group 1, 29 eyes in group 2. Mean sensitivity did no differ between groups (30.0 ± 0.59 vs. 28.4 ± 1.05 dB; p = 0.2), but the correlation between sensitivity and visual acuity did it (group 1, rho: -0.41; group 2, rho: -0.25). In group 1, foveal sensitivity was the only explaining variable of the regression model (beta: -0.52), in group 2 no one explaining variable was included and temporal perifoveal thickness had a negative correlation with foveal sensitivity (rho: -0.60).

Conclusions

Temporal perifoveal thickening reduces the correlation between foveal sensitivity and visual acuity in eyes with diabetic macular edema.