Objective
To study the displacement of the retina and its change after vitrectomy in idiopathic epiretinal membrane (ERM).
Design
Prospective, interventional case series.
Methods
Fifty-six eyes of 53 consecutive patients with ERM underwent vitrectomy with ERM removal and internal limiting membrane peeling. Fundus autofluorescence (FAF) imaging was examined before and at 1, 3, 6, and 12 months after vitrectomy. Main outcome measures were the proportion of eyes with retinal displacement for ERM detected by FAF imaging and the recovery rate of retinal displacement after vitrectomy.
Results
Before surgery, FAF photography demonstrated hyperautofluorescent lines within the vascular arcade in 37 (66.1%) of the 56 eyes. The lines seemed to be consistent with the location of the retinal vessels before their displacement. These hyperautofluorescent lines appeared significantly more frequently among patients in whom the disease duration was 3 years or less. In 23 (62.2%) of these 37 eyes, within the first postoperative month, the hyperautofluorescent lines disappeared. The disappearance of the hyperautofluorescent line was thought to be the result of the return of the retinal vessel to its original position. Greater visual improvements (logarithm of the minimal angle of resolution, ≥0.3) were statistically significantly obtained in patients in whom the hyperautofluorescent lines had become indistinct at 1 month after surgery ( P < .05).
Conclusions
Hyperautofluorescent lines indicating retinal displacement were found by FAF in 66.1% of patients before surgery for ERM. In addition, retinal displacement was significantly more common among patients who had experienced subjective symptoms for 3 years or less. Fundus autofluorescence is useful for predicting postoperative visual acuity improvement.
In eyes with idiopathic epiretinal membrane (ERM), the retina moves because of the contraction of the membrane. Kofod and la Cour reported that the retinal vessel movements correlated to worsening of best-corrected visual acuity (BCVA) and increased central macular thickness and were more pronounced in patients with worsening of symptoms. At the present time, however, it is difficult to determine the degree to which the retina has been moving. In 2010, Shiragami and associates reported that fundus autofluorescence (FAF) imaging was useful in the detection of retinal displacement after vitrectomy in rhegmatogenous retinal detachment patients. After standard vitrectomy for rhegmatogenous retinal detachment, FAF photography showed the hyperautofluorescent lines to be superior and parallel to the retinal vessels, which was consistent with their location before the vitrectomy. These lines indicated the downward movement of the retina.
Vitrectomy is useful for treating ERM and helping to restore visual acuity. These previous studies showed that the displaced retina returns to its original position to some degree. Lo and associates recently reported the extent of severe foveal displacement and its correlates with decreased visual acuity. We also attempted to qualify the extent of retinal movement in the posterior fundus using FAF photography. Based on these findings, we studied the retinal displacement in ERM and the changes that occur after vitrectomy using FAF. In addition, the relationship between recovery of the retinal position and the postoperative recovery of visual acuity was studied.
Methods
Patients
All procedures conformed to the Declaration of Helsinki, and informed consent for research was obtained from each of the patients participating in the study. This prospective study was approved by the Institutional Review Board of Kagawa University Faculty of Medicine before the beginning of the study and was in compliance with Health Insurance Portability and Accountability Act requirements. Between September 2009 and December 2010, we examined a total of 56 eyes of 53 consecutive ERM patients who underwent vitrectomy with ERM removal and ILM peeling with brilliant blue G staining at Kagawa University Hospital. This study excluded eyes with diseases other than ERM that potentially could influence the visual acuity. Before surgery, BCVA, color fundus photography, FAF imaging (Topcon TRC-50DX; Topcon, Tokyo, Japan), and measurement of the central retinal thickness (CRT) using spectral-domain optical coherence tomography (Cirrus; Carl Zeiss Meditec Inc, Dublin, California, USA) were performed before and at 1, 3, 6, and 12 months after surgery. The BCVA measured with a Japanese standard decimal visual acuity chart and was recorded, and the mean BCVA was calculated using the logarithm of the minimal angle of resolution scale.
Surgical Technique
Local anesthesia was induced by retrobulbar nerve block. In all cases, the Accurus vitrectomy system (Alcon Labs, Fort Worth, Texas, USA) was used to perform the 25-gauge pars plana vitrectomy. The posterior hyaloid was separated and removed using the vitreous cutter. Subsequently, brilliant blue G solution was sprayed onto the posterior retina. The brilliant blue G solution (Coomassie brilliant blue G 250; Sigma-Aldrich, St. Louis, Missouri, USA) was prepared using BSS plus (ALCON JAPAN, Tokyo, Japan) for dilution to achieve a final concentration of 0.25 mg/mL. Immediately, the brilliant blue G solution in the vitreous cavity was aspirated using a vitreous cutter. Using microforceps, the ERM was removed, and the ILM peeled from the underlying retina. Cataract surgery was performed simultaneously in all patients older than 50 years.
Ophthalmic Examinations and Fundus Photography
All patients underwent a regular ophthalmic examination, which included measurement of the BCVA and a fundus examination. In all eyes, color fundus photography and FAF using the Topcon TRC-50DX fundus camera were carried out before and after surgery (1, 3, 6, and 12 months after pars plana vitrectomy in all patients). Color fundus photography was recorded using 50-degree fields. The FAF imaging was recorded using 2 bandpass filters (based on the modification by Spaide with an excitation bandwidth of 500 to 610 nm and an emission bandwidth of 675 to 715 nm). In all eyes, spectral-domain optical coherence tomography was carried out before and after surgery at 1, 3, 6, and 12 months after the pars plana vitrectomy was performed in the patients. The maximum distance between the hyperautofluorescent lines and the location of the corresponding vessels on FAF was measured to quantify the preoperative displacement and postoperative movement.
Statistical Analysis
The Fisher exact probability test, Mann–Whitney U test, and multiple logistic regression analysis were performed to determine whether there was a significant association between the independent variables (which included age, CRT, and duration of symptoms) and the dependent variable (displacement of the retina, visual improvement). A P value of less than .05 was considered significant. All statistical analyses were carried out using SPSS software version 17.0 (SPSS Inc, Chicago, Illinois, USA).
Results
The mean age of all patients (20 males, 33 females) was 68.2 years, with a range of 50 to 86 years. Before surgery, in 37 (66.1%) of the 56 eyes, FAF photography demonstrated hyperautofluorescent lines parallel to the retinal vessels within the vascular arcade. These lines were thought to be consistent with the location of the vessels before disease onset. Representative fundus photographs for patients who exhibited hyperautofluorescent lines are seen in Figures 1 and 2 , whereas Figure 3 presents a fundus photograph for a representative patient without hyperautofluorescent lines.
As seen in Table 1 , the mean ages of patients who exhibited and did not exhibit hyperautofluorescent lines were 66.7 ± 7.6 years and 71.3 ± 6.9 years, respectively. In addition, the BCVAs were 0.46 ± 0.21 and 0.42 ± 0.25, whereas the CRTs were 449.4 ± 95.3 and 416.8 ± 72.7 μm, and the duration of symptoms were 3 years or less in 22 (59.5%) and 4 (21.1%) patients, respectively. There were 15 patients in each group (40.5% and 78.9%, respoectively) who had duration of symptoms of more than 3 years or that was unknown.
| Baseline Characteristics | Hyperautofluorescent Lines | P Value | Statistical Analysis | |
|---|---|---|---|---|
| Present | Absent | |||
| Patient age (y) | ||||
| Mean ± SD | 66.7 ± 7.6 | 71.3 ± 6.9 | .039 | Mann–Whitney U test |
| BCVA | ||||
| Mean ± SD | 0.46 ± 0.21 | 0.42 ± 0.25 | .44 | Mann–Whitney U test |
| CRT (μm) | ||||
| Mean ± SD | 449.4 ± 95.3 | 416.8 ± 72.7 | .148 | Mann–Whitney U test |
| Duration of symptoms | ||||
| 3 y or fewer | 22 | 4 | .01 | Fisher exact probability test |
| More than 3 y or unknown | 15 | 15 | ||
The presence of hyperautofluorescent lines was associated significantly with both a young age and duration of symptoms of 3 years or less ( Table 1 ). The multiple logistic regression analysis indicated that only a duration of symptoms of 3 years or less was associated with the presence of hyperautofluorescent lines ( P = .048; Table 2 ).
| Odds Ratio | 95% Confidence Interval | P Value | ||
|---|---|---|---|---|
| Lower Limit | Upper Limit | |||
| Patient age | 0.969 | 0.881 | 1.065 | .511 |
| Preoperative CRT | 1.005 | 0.997 | 1.013 | .242 |
| Duration of symptoms a | 4.435 | 1.011 | 19.444 | .048 |
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