Our present results indicate that early surgery on patients in the Good group with BCVA ≦0.046 logMAR promoted significantly greater BCVA improvement than in the Moderate group. Epiretinal membrane is known to occasionally develop in younger patients [20]. Individuals in certain occupations and those leading certain lifestyles require a high level of visual function. Therefore, we have consider performing surgery on individuals with good BCVA to be an effective approach to maintaining high-quality visual function in such individuals.
Horizontal metamorphopsia is easily perceived by patients [17, 21]. Because it is more common to encounter horizontally oriented text than vertically oriented text while writing and reading, MH is of major importance. Surgery reportedly results in a greater improvement of MH than of MV [11, 13, 15]. Thus, MH at post–6 M was used as the primary outcome measure in the present study.
Although no significant intergroup difference was found in MV at the final observation time point, possibly due to restricted horizontal displacement [13, 21, 22], MH showed improvement in both groups (Moderate group: 0.5°, Good group: 0.37°) at the final observation time point. Once metamorphopsia reaches 0.5° or worse, the patient reportedly becomes aware of the symptoms [21]. A previous study on quality of vision (QOV) reported that metamorphopsia has a more marked influence on QOV than on BCVA [23]. In the present study, in the Good group, MH improved to 0.37°, i.e. < 0.5°, thereby indicating that it was useful for improving QOV.
Only the preoperative MH was selected as a factor that affected the postoperative MH. The calculation of MH using the category model indicated that the preoperative MH leading to postoperative scores of < 0.5° was 0.9°. This result showed that the preoperative MH of 0.9° represents a clinical data point that can be used as an index for determining surgery indications.
The aniseikonia investigation revealed significant worsening of both AV and AH in the Moderate group at post–6 M and that macropsia was > 5 %. The reason for this worsening of postoperative macropsia has yet to be identified. A report on aniseikonia by Okamoto et al also showed that, although there was no significant pre- versus postoperative difference, macropsia was increased postoperatively [26]. However, in the Good group in our study, macropsia remained below 5 %, though there was no improvement. Aniseikonia ≧ 5 % reportedly indicates a loss of binocular vision [24, 25]. Therefore, in patients with a preoperative value of < 5 %, this parameter may providean index applicable to determining surgical indications for patients with good BCVA.
Concerning binocular function, TST is reportedly associated with preoperative CFT [15]. Preoperative CFT was significantly greater in the Moderate group than in the Good group and preoperative stereopsis was significantly poorer before surgery. However, the significant difference in CFT between the two groups had disappeared at post–6 M, resulting in no significant difference in stereopsis. Asaria et al reported that the longer the symptoms persist preoperatively, the worse the pre- and postoperative stereopsis tends to be [27]. In the present study, the time period from initial symptom onset even in the Good group was unknown. If surgery is performed shortly after symptom onset, then better recovery of visual function including binocular function can be achieved.
VFQ–25 assessment was performed only for the Good group. Okamoto et al, who evaluated patients with a mean preoperative logMAR score of 0.495, reported that the composite score improved from 66.2 preoperatively to 77.9 postoperatively and that all items, with the exception of general health and peripheral vision, showed significant postoperative improvement [9]. The preoperative BCVA was good in the present study. Therefore, the preoperative composite score was also high at 75.3. Despite this, the score at post–12M showed significant improvement to 82.0, indicating that the surgery in the Good group was effective. Postoperative scores for both general health and vision-related mental health improved, indicating that the patient satisfaction level also improved with the surgery. Both general vision and near activities improved, possibly due to the improvement in visual function itself. As vision itself improved, eye strain was alleviated, which in turn may have ameliorated ocular pain.
The present study prospectively analyzed patients in the Good group. In contrast, because previous data were utilized in the Moderate group, which was used for comparison, postoperative 1 M and 12 M data could not be obtained. Symptoms may also improve at 1 or 2 years postoperatively [28]. Therefore, further investigation of this issue over longer periods of time and with higher numbers of patients is required. The present study included 20 cases with pseudo-macular holes. Although there was no significant intergroup difference in terms of the pseudo-macular hold rate, further investigation without pseudo-macular hole cases should be conducted to investigate metamorphopsia and aniseikonia accurately.
No postoperative complications developed in the present study. However, the BCVA of one 79-year-old male patient with pseudo-macular holes decreased from 1.0 preoperatively to 0.7 in decimal BCVA at 12 M postoperatively. The patient had no subjective perception that his BCVA had declined. It is sometimes difficult to improve BCVA in patients with pseudo- and lamellar macular holes with vitreous traction [29]. Therefore, caution is required when determining surgical indications in such cases with good BCVA. Also, sufficient caution is essential when managing epiretinal membrane patients with uveitis [30], concurrent glaucoma [31], and cyst formation [32].
Recently, micro-incision vitrectomy surgery has come into widespread use and its safety has improved dramatically. Therefore, the surgical indications for macular surgeries have been expanding. Number of patients with epiretinal membrane are expected to increase as the mean age of the population rises. The results obtained in this study indicate that early epiretinal membrane surgery can improve QOL in patients with good BCVA.