Discussion
Spontaneous release rate of VMT is achieved only in 11%–47% of the cases over a mean time frame of 8–60 months,7 8 and even with spontaneous release abnormal structural changes in the macula and decreased visual acuity can persist, especially in chronic and/or severe cases of VMT. For VMT associated with FTMH, spontaneous closure rates are much lower (3%–11% of cases).9 10 Most MHs enlarge, with a progression rate of 84% from stage II to stage III/IV.10 Untreated FTMHs can result in significant and persistent decrease in visual acuity. The closure rates of MHs with current vitrectomy techniques are typically 88% or higher.11
In VMT, treatment observation is shown to be ineffective; however, PPV is, today, the best treatment, but there is a higher risk of cataract formation, glaucoma, infection, retinal tears and detachment; for this reason, less invasive but effective treatment options are being developed.
Through the recently approved ocriplasmin (Jetrea; Thrombogenics, USA, Alcon/Novartis EU), pharmacological vitreolysis shows a possible safer alternative to surgery in patients affected by VMT.5
In our study, we report the Italian clinical experience using ocriplasmin for VMT with or without an MH. In phase III testing, the efficacy of ocriplasmin for VMT release was 26.5%,3 but this percentage can be higher (42%–67%)%) depending on the presence of positive predictive criteria like: age less than 65 years, focal adhesions ≤1500 mm, presence of FTMH, phakic status and absence of epiretinal membrane.4 Our results showed that VMT release occurred in 44 eyes (44/74 eyes; 59.5%). In 22 eyes (22/44, 50%), success occurred within the first month of follow-up. This difference between the clinical trials and the results of postmarketing studies could be due to our selection of the patients.
The closure rate of FTMH in our study was 40%; this finding is also consistent with data of the Microplasmin for intravitreous injection-traction release without surgical treatmen (MIVI-TRUST) trials (40.6%).3 4 The MH diameter was shown to be an important prognostic factor; in fact, eyes with FTMH width of ≤250 µm at baseline were more likely to achieve pharmacological FTMH closure (53.8%) compared with those with FTMH width of >250 µm, who achieved closure only in 7% of the cases. Furthermore, our group included four patients with FTMH >400 µm, in whom the closure rate was 0%. Eyes with FTMH width between 250 µm and 400 µm at baseline achieved a closure rate of 33.3%. These results are similar to those obtained by the clinical trials.4 In other reports, different closure rates were presented (17%%–27%−28.6%−40%).5–7 12
In figure 3, successful and unsuccessful cases are12 presented using OCT images.
VMT extension was shown to be, according to the clinical trials,4 an important prognostic factor; in fact, the success rate was 0% in the eyes with VMT extension ≥1500 micra. However, the association between ERM presence at baseline and VMT release was not significant (p 0.931). This result is not in agreement with the clinical trials,4 in which the prevalence of ERM may have been underestimated. In the clinical trials, an old generation time-domain OCT was used, so patients with very evident epiretinal membrane were also included. Although we used the SD-OCT (more capacity of detection of epiretinal membranes), the prevalence of ERM in our patients was lower (16.2% vs 38.7%). This discrepancy is more probably due to improved patient selection for the ocriplasmin injection.
Regarding visual function, ocriplasmin showed important results: an improvement or complete resolution of metamorphopsia was achieved in 50.8% of the eyes. Furthermore, in our results, visual acuity at baseline did not influence VMT resolution after the injection (p 0.5153). The patients in which there was VMT resolution had better visual acuity; in fact, if we consider the difference between BVCA after 3 months of follow-up among the success and no-success groups, in the first group, there was significant improvement (about three lines) (p<0.0001) figure 4.
Figure 4Scatterplot of baseline (x-axis) versus 3-month (y-axis) logMAR visual acuity. Eyes with surgical success are presented as light grey diamonds and those with no success are dark grey dots. Values above the diagonal (dashed) line are improved compared with baseline.
This result could be explained in part by the complete restoration of the ellipsoid zone (EZ) integrity after the ocriplasmin injection, which takes about 3 months.13 In fact, it has been described in literature that transient OCT-based alterations were identified in a substantial number of the eyes after ocriplasmin therapy.14 These transient changes are particularly prominent in the EZ. In addition, the accumulation of subretinal fluid has also been described and appears to be closely linked to the changes in the EZ. The phase III trials used time-domain OCT, so the detection of these changes was difficult. The integrity of the EZ has been identified as an important factor for VA in multiple vitreoretinal conditions.15–17
In two cases, we encountered a strong adhesion between the posterior hyaloid and the optic pit; however, performing active aspiration with the vitrectomy probe, even though after approximately 1 min of suction, we obtained the vitreous separation from the posterior pole.
In our series, we observed adverse events in only 25.7% of the eyes; the majority of these were transitory, and VMT resolution was observed in about 27 days; no serious adverse events were registered.
