DME is still an important reason for visual impairment in diabetics and may be refractory to conventional therapies.26
Eyes categorized as diffuse DME do not properly respond MPC visual .15 Lee and Olk5–6 assessing 302 eyes categorized as diffuse DME after treatment with MPC, announced an improvement in vision identical to three Early Treatment of Diabetic Retinopathy Study (ETDRS) charts or over in just 13.7% of eyes after a year, and decline of visual function in 25% at three years. Visual rehabilitation in such cases with no respond to laser photocoagulation, is challenging. vitrectomy is suggested for VMT or a tractional ERM cases.29
Different data have been reported on the vitrectomy effect on BCVA. However, vitrectomy for DME is recommended due to the association between PVD and a lower prevalence of DME. Nasrallah et al16 showed that just 20% of DME eyes showed PVD, while 55% of eyes with no DME showed PVD. Vitrectomy is effective for eyes characterized by detectable hyaloid thickening or contraction, however, the outcomes are controversy regarding eyes with no hyaloidal abnormality. In the current study, a significant improvement was found in foveal thickness. Nonetheless, no significant improvement was detected in visual acuity. Different studies have revealed a significant improvement in BCVA9–11. For example, an improvement of two or over lines in 43–92% of eyes subjected to PPV with ILM removal.7–11, 17 PPV with ILM peeling can reduce retinal thickness with no visual improvement .18–20 The rate of eyes experiencing a minimum of 2 lines of improvement (45%), was at the same rate or over than those reported earlier 7–11, 17.
Our results are in contrast with those by Kim et al 28 who announced that BCVA significantly improved (from 0.44 ± 0.15 logMAR to 0.34 ± 0.22 logMAR after six months) and BCVA decreased at 3 months that was reported to be due to cataract progression. Accordingly, two points should be considered. 1) In Kim et al 28 research the baseline average BCVA was significantly higher compared with ours as well as in Dehghan et al27 research. 2) Kim et al studied (28 eyes) more eyes compared with the current research as well as Dehghan et al27 (12 eyes) study.
Such discrepancies may be due to variations in inclusion criteria, past therapies, chronicity level, previous MPC and/or IVB, diabetic retinopathy level, macular ischemia severity that are not commonly detectable on FA, and follow up period.
PPV with ILM peeling can cause a significant reduction in macular width,7–12,14 however, it is uncorrelated precisely with improvement in visual acuity,18–20(as our research). Such disagreement between anatomic and visual results is possibly because of the increased lens opacity as well as deteriorate of diabetic retinopathy.
Less is known regarding ILM removal function in DME. PPV with no ILM removal has been demonstrated influential like surgery with ILM removal regarding reduced retinal width and visual acuity improvement .12,21 In contrast, PPV could successfully reduce DME, however, better outcomes were achieved in eyes with ILM removal compared with cases with no ILM removal.17 Gandorfer et al7 found that diffuse DME that is able to progresse in spite of PPV along with posterior hyaloid and epiretinal membrane removal for non-clearing vitreous hemorrhage, is resolved quickly following ILM removal. Kimura et al14 introduced rapid resolution of DME in eyes subjected to PPV with no epiretinal membrane. Residual cortical vitreous can be connected to the macula following the posterior hyaloid removal through triamcinolone-assisted PPV.22 Eyes with diabetic maculopathy are found with ILM thickening and cell frequency on the vitreous direction of the ILM.23 Thus, ILM peeling is effective in DME through the removal of the tangential traction due to the ILM and residual cortical vitreous. Also, it possibly is effective to prevent epiretinal membrane generation after surgery via the removal of the scaffold for proliferating cells. We consistent with other studies 7–12 did not find epiretinal membrane generation after surgery reported in 10.2% − 13.8% of eyes following PPV with no ILM peeling,24–26, however, a research announced epiretinal membrane generation in 5% of eyes.14
Complications after surgery were subconjunctival hemorrhage in 4 eyes, hyphaema in 4 eyes and vitreous hemorrhage in 2 eyes that resolved 3 month post operation.
The power of our study are the prospective, PPV along with ILM peeling and IVB injection, Contrast sensitivity measurement and independent, unsponsored study. However, our study has some limitation such as small sample size, short term follow-up and randomization deficiency. Also, systemic parameters, particularly HbA1c and lipid levels, can be confounding factors however, we did not evaluate them.
It can be concluded that vitrectomy with ILM removal and IVB injection for persistent diffuse DME is able to decrease macular thickness, however, causes no significant improvement in visual acuity through a 3-month follow. A large, multicenter, randomized controlled trial is needed to compare PPV with/without ILM removal as well as IVB injection using longer follow-up for establishing the ILM removal effect on treating DME.