Pars Plana Vitrectomy for Tractional Diabetic Macular Edema with or without Internal Limiting Membrane Peeling

doi:10.21203/rs.3.rs-2003878/v1

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Pars Plana Vitrectomy for Tractional Diabetic Macular Edema with or without Internal Limiting Membrane Peeling

https://doi.org/10.21203/rs.3.rs-2003878/v1

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Background

To assess the efficacy of pars plana vitrectomy (PPV) in management of tractional diabetic macular edema (DME) and highlight the benefits of additional internal limiting membrane (ILM) peeling.

Methods

This prospective study involved 50 eyes with tractional DME that underwent PPV were split into two groups: group (A) consisted of 25 eyes that did not have ILM peeling, and group (B) consisted of 25 eyes that did. One, three, and six months after surgery, a postoperative assessment was completed.

Results

Mean best corrected visual acuity (BCVA) in group (A) has improved from (0.89 the logarithm of minimal angle of resolution [LogMAR]) preoperatively to (0.64 LogMAR, p < 0.001), and mean central macular thickness (CMT) declined from (471.28µm) to (228.20µm, p < 0.001) after six months of PPV. In group (B), mean BCVA has improved from (0.83 LogMAR) preoperatively to (0.58 LogMAR, p < 0.001), and mean CMT decreased from (496.84µm) to (226.20µm, p < 0.001) after six months of PPV. There were no significant differences between the two groups after 1, 3, and 6 months according to the delta change % of BCVA and CMT. A significant negative correlation was detected between preoperative glycosylated hemoglobin (HbA1c) and BCVA improvement.

Conclusions

PPV surgery is an effective treatment of tractional DME. Additional ILM peeling is not accompanied by extra benefits in a short period. Long-term glycemic control plays a role in vision gain after vitrectomy in diabetic patients.

Vitrectomy

diabetic macular edema

internal limiting membrane

glycosylated hemoglobin

Diabetes (DM) is one of the most challenging public health issue facing almost all communities nowadays. Diabetes affected approximately 285 million people in 2010, accounting for nearly 6% of the global population.The international diabetes federation anticipateed a jump in the number of diabetic patients to nearly 550 million by 2030, which represents about 8% of total world population [1]. Diabetic retinopathy (DR) might be the main cause of vision loss globally. In 2010, DR affected more than 93 million persons worldwide, and 28 million out of them were diseased by vision-threatening diabetic retinopathy (VTDR). VTDRS is defined as the occurrence of severe non proliferative diabetic retinopathy (NPDR), proliferative diabetic retinopathy (PDR), or DME. The prevalence of DR multiplied from nearly 20% to about 50% when HbA1c rose from below or equal 7.0 to more than 9.0% [2].

It has been shown that the possibility of evolveing diffuse diabetic macular edema is 3.4 times less in the eyes which developed complete posterior vitreous detachment (PVD) compared to those with incomplete PVD [3]. Since 1990, several authors have confirmed the benefits of PPV in DME combined with tangential hyaloidal traction caused by taut thickened posterior hyaloids [4].

The ILM is the Muller cell’s basement membrane, which is stiffer than the underlying retinal layers and easily to be bent and changed shape. Muller cells may move to the internal side of the ILM forming a membranous layer, which can contract tangentialy. ILM serves an optimal media for cell proliferation and is usually entangled in the vitreomacular interface (VMI) diseases [5, 6]. The value of peeling of the ILM has been examined in surgical treatment of DME. Many surgeons believe that ILM removal has additional anatomical and visual advantages and prevents the recrudescence of the epi-macular membrane (EMM) [7–9]. In contrast, others reported that ILM peeling did not lead to visual improvement or no difference in both anatomical and functional outcomes [10–13].

Patient selection

This study is an interventional, prospective, and comparative study performed in the Ophthalmology department at Al-Azhar University Hospitals. Approval by Al-Azhar Medical Research Ethical Committee is adhered to the Helsinki Declaration, and was reported to all patients. Patients were enrolled consecutively in the study. All of them gave their informed consent prior to surgery. Inclusion criteria included (i) type 1 or 2 diabetic patients; (ii) presence of PDR; (iii) Age ≥ 40 years; (iv) Snellen chart BCVA better than 20/300 in the study eye; (v) OCT evident of EMM causing tangential traction with resultant tractional DME.

Exclusion criteria included tractional retinal detachment (TRD), macular holes, angiographic evidence of macular ischemia, history of macular photocoagulation, intravitreal corticosteroids or anti-VEGF (vascular endothelial growth factor) within three months prior to PPV, cataract surgery within three months before PPV, previous vitrectomy or glaucoma surgery, presence of iris or angle neovascularization, history of trauma or uveitis, and presence of corneal opacification, dense cataract or vitreous hemorrhage preventing imaging of the retina.

Preoperative assessment

The patient’s preoperative data was collected including detailed medical history, Snellen BCVA which was converted to approximate LogMAR equivalents for statistical calculation, full slit lamp examination of anterior segment (cornea, lens, pupils and iris), intraocular pressure measurement using an applanation tonometer, gonioscopy to ensure absence of iris neovascularization, and fundus examination using slit lamp and + 78 D lens.

Fluorescein angiography (FA) using the Topcon TRC 50DX retinal fundus camera (Topcon Optical Co., Tokyo, Japan) was done to exclude macular ischemia and to asses PDR. Patients were informed before dye injection about the potential risks associated with the procedure.

CMT assessment using spectral domain optical coherence tomography (OCT) (Spectralis OCT; Heidelberg Engineering, Heidelberg, Germany) to document macular thickness, configuration of tractional macular oedema, and EMM.

A general medical evaluation was obtained prior to PPV in the form of preoperative laboratory tests (complete blood picture, bleeding profiles, liver and kidney functions, viral markers, random blood glucose and Hb A1c), and internal medicine consultation.

Surgical procedures

Two groups of the study's eyes were formed:

(A) group: (without the peeling of the ILM) included 25 eyes of participants.

(B) group: (with the peeling of the ILM) included 25 eyes of participants.

The standard PPV using 23-gauge three port PPV technique under peribulbar anesthesia for all patients was performed by one surgeon (Mahmoud Mohamed Ahmed). A DORC vitrectomy machine (DORC International) was used in conjunction with a BIOM system attached to a surgical microscope to allow visualization of the posterior segment without contact lenses. Membrane blue-Dual (DORC International) was used to visualize and ensure complete removal of posterior hyaloid and EMM. To stain the ILM, brilliant blue G (BBG) dye solution (ILM Blue, DORC International) was injected. In group (A), ILM was left without peeling after staining, whereas in group (B), ILM peeling in a circular fashion was achieved using an endgripping ILM forceps. The size of the ILM peeling area was nearly two discs in diameter, extending from the upper to the lower arcades. Endo-laser pan retinal photocoagulation was done for all patients. The vitreous cavity was left in the fluid. In the presence of significant cataract, phacoemulsification and intraocular lens implantation were performed before the vitrectomy. Combined phaco-vitrectomy was done in 13 cases, 7 cases in group (A) and 6 cases in group (B).

Postoperative follow up

On the first post-operative day, a complete slit lamp examination was performed to rule out any early post-operative complications. The patients were then examined one week, one month, three months, and six months after surgery. Examinations include anterior segment examination, fundus examination, intraocular pressure measurement, and Snellen chart BCVA assessment. CMT was measured using an OCT (Spectralis OCT; Heidelberg Engineering, Heidelberg, Germany) at the 1st, 3rd, and 6th months after surgery.

Statistical analysis

Statistical analysis was performed using the Statistical Package for Social Sciences, version 23.0 (SPSS Inc., Chicago, Illinois, USA). The quantitative information was presented in the form of mean, standard deviation, and ranges. Qualitative variables were also introduced in the form of numbers and percentages. To investigate the normality of the data, the Kolmogorov-Smirnov and Shapiro-Wilk tests were used.

Preoperative demographic and baseline characteristics (Table 1)

Surgeries were performed on 50 eyes of 46 Egyptian patients with tractional DME between January 2018 and May 2022. The 50 eyes divided into 2 groups; (A) group: (without the peeling of the ILM) included 25 eyes and (B) group: (with the peeling of the ILM) included 25 eyes.

Table 1: Preoperative demographic and baseline data

Characteristics	Group A (n=25)	Group B (n=25)	Test value	p-value
Sex
Male	10 (40.0%)	9 (36.0%)	x²:0.085	0.771
Female	15 (60.0%)	16 (64.0%)	x²:0.085	0.771
Age (years)
Mean ±SD*	55.12±4.27	54.00±4.97	t:0.855	0.397
Range	48_62	46_62	t:0.855	0.397
Duration of DM (years)			U:1.204	0.229
Mean±SD*	8.32±2.08	9.12±2.37
Range	5_12	5_13
Insulin			x²:0.739
No	12 (48.0%)	9 (36.0%)		0.390
Yes	13 (52.0%)	16 (64.0%)
HbA1c			t:1.433	0.158
Mean±SD*	7.51±0.57	7.76±0.66
Range	6.1_8.8	6.1_8.7
Associated Hypertension			x²:0.081	0.777
No	14 (56.0%)	13 (52.0%)
Yes	11 (44.0%)	12 (48.0%)

Notes: Using: x²: Chi-square test; t-Independent Sample t-test; U=Mann-Whitney test.

p-value >0.05 insignificant.

Abbreviations: SD, standard deviation; HbA1c, glycosylated hemoglobin.

Preoperative phakic status

Prior to PPV, 7 eyes of group (A) and 9 eyes of group (B) were pseudo-phakic (p = 0.548). Preoperative significant cataract was detected in 13 eyes therefore combined phaco-vitrectomy surgery was done for them; 7 eyes of group (A) and 6 eyes of group (B) (p = 0.749).

The BCVA changes (Figure 1)

Mean preoperative BCVA (LogMAR) in total 50 eyes was 0.86±0.11 [0.89±0.12 in group (A) and 0.83±0.10 in group (B), (p = 0.243)]. After PPV by one-month, mean BCVA (LogMAR) in total 50 eyes was 0.74±0.14 [0.76±0.16 in group (A) and 0.72±0.12 in group (B), (p = 0.411)]. In comparison to preoperative BCVA, there was a significant improvement (p = 0.007). After three months, mean BCVA (LogMAR) in total 50 eyes was 0.65±0.20 [0.68±0.19 in group (A) and 0.62±0.20 in group (B), (p = 0.198)]. Compared to preoperative BCVA, there was a highly significant improvement (p < 0.001). After six months, the mean BCVA (LogMAR) in the total 50 eyes was 0.61±0.24 [0.64±0.24 in group (A) and 0.58±0.24 in group (B), (p = 0.198)]. In comparison to preoperative BCVA, there was a highly significant improvement (p < 0.001).

According to delta change % of BCVA (LogMAR), there was a statistically insignificant difference between the two groups after 1 month, 3 and 6 months (p = 0.082, 0.142, and 0.256 respectively) (Figure 2) and (Table 2).

Table 2: Comparison between group (A) and group (B) according to delta change% of BCVA (LogMAR)

Change between	Group A (n=25)	Group B (n=25)	U-Test	p-value
Baseline-1month BCVA
Mean ±SD*	-0.13±0.02	-0.11±0.03	-1.684	0.082
Change%	-14.61%	-13.3%
Baseline-3months BCVA
Mean ±SD*	-0.21±0.03	-0.21±0.04	-1.216	0.142
Change%	-23.6%	-25.3%
Baseline-6months BCVA
Mean ±SD*	-0.25±0.04	-0.25±0.05	-1.071	0.256
Change%	-28.09%	-30.12%

Notes: Using: U=Mann-Whitney test.

p-value >0.05 insignificant.

Abbreviations: BCVA, best corrected visual acuity; LogMAR, the logarithm of minimal angle of resolution; SD, standard deviation.

There was a negative correlation between BCVA improvement after 6 months and preoperative glycemic control (HbA1c) (p = 0.007) (Figure 3).

By the end of our study, 17 eyes (68%) in group (A) improved BCVA by 2 or more lines in the Snellen chart compared with 19 eyes (76%) in group (B). 4 eyes (16%) in group (A) did not get improved BCVA or improved less than 2 lines in the Snellen chart compared to 3 eyes (12%) in group (B). 4 eyes (16%) got worsened BCVA in group (A), compared with 3 eyes (12%) in group (B) (p = 0.820).

CMT changes (Figure 4)

Mean preoperative CMT in total 50 eyes was 484.06±85.55μm [471.28±80.83μm in group (A) and 496.84±89.82μm in group (B), (p = 0.296)]. After PPV by one-month, mean CMT in total 50 eyes was 306.36±57.18μm [292.44±61.34μm in group (A) and 320.28±50.09μm in group (B), (p = 0.085)]. In comparison to preoperative BCVA, there was a highly significant CMT decrease (p <0.001). After three months, mean CMT in total 50 eyes was 254.80±26.73μm [247.40±28.35μm in group (A) and 262.20±23.25μm in group (B), (p = 0.198)]. After six months, the mean CMT in the total 50 eyes was 227.20±22.43μm [228.20±26.45μm in group (A) and 226.20±18.04μm in group (B), (p = 0.198)]. In comparison to the preoperative CMT, there was a highly significant decrease (p < 0.001).

According to delta change % of CMT by OCT, there was a statistically insignificant difference between the two groups after 1 month, 3 months, and 6 months (p = 0.816, 0.712, and 0.282, respectively) (Figure 5) and (Table 3).

Table 3: Comparison between group (A) and group (B) according to delta change% of CMT by OCT.

Change between	Group A (n=25)	Group B (n=25)	U-test	p-value
Baseline-1month CMT
Mean±SD*	-178.84±54.94	-176.56±54.82	-0.233	0.816
Change%	-37.9%	-35.5%
Baseline-3months CMT
Mean±SD*	-223.88±64.59	-234.64±81.47	-0.369	0.712
Change%	-47.5%	-47.2%
Baseline-6months CMT
Mean±SD*	-243.08±66.64	-270.64±87.00	-1.077	0.282
Change%	-51.6%	-54.5%

Notes: Using: U=Mann-Whitney test.

p-value >0.05 insignificant.

Abbreviations: CMT, central macular thickness; OCT, optical coherence tomography; SD, standard deviation.

By the end of our study, 17 eyes (68%) in group (A) showed a reduction of more than 50% of CMT compared with 23 eyes (92%) in group (B). CMT reduction less than 50% was detected in 8 eyes (32%) in group (A) and in 2 eyes (8%) in group (B) (p = 0.321).

Complications

Intraoperative complications

Only 1 eye in group (A) had an iatrogenic break, 2 eyes in the group (B) had iatrogenic breaks (P = 0.556) which were treated intra-operatively by endo-laser photocoagulation.

Postoperative complications

16 cases developed complications “that not prevent follow up and OCT imaging”; 7 of group (A) and 9 of group (B) (p = 0.762) (Table 4).

Table 4: Comparison between group A and group B according to postoperative complications

Postoperative Complications	Group A (n=25)	Group B (n=25)	Total (n=50)	x²	p-value
No	18 (72.0%)	16 (64.0%)	34 (68.0%)	0.092	0.762
Yes	7 (28.0%)	9 (36.0%)	16 (32.0%)	0.092	0.762
Cataract	2 out of 11 phakic eyes (18.2%)	3 out of 10 phakic eyes (30.0%)	5 out of 21 phakic eyes (23.8%)	0.218	0.641
EMM*	1 (4.0%)	0 (0.0%)	1 (2.0%)	1.000	0.317
Glaucoma	0 (0.0%)	1 (4.0%)	1 (2.0%)	1.000	0.317
Vitreous hemorrhage	2 (8.0%)	4 (16.0%)	6 (12.0%)	0.742	0.389
Iridocyclitis	2 (8.0%)	1 (4.0%)	3 (6.0%)	0.348	0.556

Notes: Using: x²: Chi-square test.

p-value >0.05 insignificant.

Abbreviations: EMM, epi-macular membrane.

PPV whether with or without ILM peeling remains the gold standard therapy of DME caused by tractional EMM to release vitreomacular abnormalities (VMAs) and restore normal central retinal contour. Additional ILM peeling may have some positive impacts on vision and macular thickness. The ILM may compose a scaffold promoting production of the EMM [8]. In diabetic eyes, there are abnormal cross-links of fibrils that cause strong connections between the posterior hyaloid and ILM. The ILM is pathologically thickened in diabetic eyes due to the accumulation of extracellular matrix elements by macrophages and fibroblasts. The ILM also contributes to the DME as a result of its rigidity, and removing it allows the release of tangential tractional forces [14]. Moreover, the diffusion of oxygen from the vitreous into the retinal tissue is retarded by the dense ILM found in diabetic patients [15]. The main goal in these surgeries is to isolate the posterior hyaloid from the macula, and ILM peeling ensures that all hyaloidal elements are released [16].

On the other hand, some surgeons believe that ILM peeling does not add any additional benefits to vitrectomy in the treatment of DME. Moreover, some believe that ILM peeling is considered a trauma that can result in retinal damage, especially in a pathological retina [17].

Our study enrolled 50 eyes from 46 patients with tractional DME as a result of EMM formation. 25 eyes underwent PPV without ILM peeling [group (A)], and another 25 eyes underwent PPV with ILM peeling [group (B)].

In the total 50 eyes, mean BCVA LogMAR improved from (0.86±0.11) preoperatively to (0.74±0.14, p =0.007), (0.65±0.20, p <0.001) , (0.61±0.24, p <0.001) at one , three and six months respectively after PPV. The mean BCVA improved by about 14%, 24% and 29% after one, three, and six months, respectively, after PPV.

Several studies showed that vitrectomy in presence of tractional DME led to an improvement in BCVA in more than 50% of cases. Degree of mean BCVA improvement was comparable with (Pendergast nearly 33%) [18], (Yamamoto nearly 57.5% in group A, eyes with PVD and EMM; and about 53.5% in group C, eyes without PVD and with EMM) [19], (diabetic retinopathy clinical research network [DRCR.net] vitrectomy study, ranging from 28% to 49%) [20], (Kim nearly 24% after 3 months, about 30% after 6 months and about 42% after 12 months) [21], (Someya nearly 37% after 6 months) [22].

Also, Jackson et al. in 2016 who studied PPV for vitreomacular traction (VMT) showed near results. The diabetic group analysis showed that, the median BCVA get improved from 0.7 LogMAR at surgery to 0.5 LogMAR at six to twelve months post-surgery with about 33% improvement in BCVA at least 0.3 LogMAR (approximately two Snellen lines) [23]. This is nearly the value of 33% reported in a systematic review about vitrectomy for VMT by Jackson et al in 2013 [24].

Regarding our study, in group (A) ( non-peeling group), mean BCVA LogMAR improved from (0.89±0.12) preoperatively to (0.76±0.16, p <0.001), (0.68±0.19, p <0.001), (0.64±0.24, p <0.001) after one , three and six months respectively after PPV. In group (B) (peeling group) the mean BCVA LogMAR improved from (0.83±0.10) preoperatively to (0.72±0.12, p =0.047), (0.62±0.20, p =0.024) , (0.58±0.24, p <0.001) after one , three and six months respectively after vitrectomy. There were statistically insignificant differences between the study groups (p >0.05) preoperatively and postoperatively after one , three and six months.

In our study, mean CMT in the total 50 eyes decreased from (484.06±85.55μm) preoperatively to (306.36±57.18μm, p <0.001), (254.80±26.73μm, p <0.001), (227.20±22.43μm, p <0.001) at one , three and six months respectively after PPV. The mean CMT decreased by about 37%, 47% and 53% after one , three and six months respectively after PPV.

Several studies showed that PPV led to significant reduction of CMT in most cases; (Pendergast in 81.8% of cases, the macular edema completely resolved during a period of 4.5 months) [18],(Yamamoto CMT reduced by about 46.9% in group A and 50% in group C) [19], (Kim CMT reduced by about 28% after 12 months in tractional DME group) [21], (Someya CMT reduced nearly 45% after 12 months in tractional DME group) [22].

Regarding our study, in group (A) ( non-peeling group), mean CMT has decreased from (471.28±80.83μm) preoperatively to (292.44±61.34μm, p <0.001), (247.40±28.35μm, P<0.001), (228.20±26.45μm, p <0.001) after one , three and six months respectively after PPV. In group (B) (peeling group), mean CMT has decreased from (496.84±89.82μm) preoperatively to (320.28±50.09μm, p <0.001), (262.20±23.25μm, p <0.001) , (226.20±18.04μm, p <0.001) after one , three and six months respectively after PPV. There were statistically insignificant differences between the study groups (p >0.05) preoperatively and postoperatively after one and six months. There was a statistically significant difference between the study groups (p = 0.049) postoperatively after three months.

Improvement in BCVA and reduced CMT were better in group (A) (non-peeling group) at the beginning of follow up after one month from vitrectomy. Improvement was nearly the same after three months, then group (B) (peeling group) became better after six months. This may be related to trauma caused by ILM gripping forceps and a little more added time for peeling.

Our comparative study results are in the same direction with Rinaldi et al who examined this issue in their meta-analysis, looking at diabetic eyes who underwent PPV and ILM peeling versus eyes that underwent PPV only. The eyes with no clinical evidence of traction were only included. There were 672 eyes from 4 studies. As regards postoperative BCVA, BCVA change, CMT or CMT change, they found no significant differences between the two groups. They concluded that ILM peeling in PPV did not significantly improve visual or anatomic results [25].

In their systematic meta-analysis, Nakajima et al also examined the impact of ILM peeling combined with PPV for DME. In comparison to the non-peeling group, the postoperative BCVA in the ILM peeling group was superior by 0.04 (-0.05 to 0.13) LogMAR (nearly 2 lines by ETDRS letters, p = 0.37) and the BCVA change was superior by 0.04 (-0.02 to 0.09) LogMAR (nearly 2 lines by ETDRS letters, p = 0.16). There was no discernible difference in postoperative CMT or CMT reduction between the two groups. They came to the conclusion that there was no significant difference between the visual acuity results using PPV with ILM peeling and no ILM peeling [13].

Flaxel et al collected prospective data from 241 eyes underwent PPV for DME. Multiple parameters were used to evaluate associations of 20 preoperative and intraoperative factors within six months outcomes of BCVA and CMT. They reported that ILM peeling showed better anatomical outcomes but was not associated with better BCVA improvement after PPV [11].

Also, Shiba et al found no different surgical outcomes among the three operative techniques for DME patients. The tree techniques were vitrectomy alone, vitrectomy combined with peeling of ILM, and vitrectomy combined with removal of the posterior hyaloid using triamcinolone acetonide accompanied with intravitreal triamcinolone acetonide injection postoperatively [26].

On the other hand, a meta-analysis was achieved by Hu et al who examined 14 studies involving 857 eyes. They concluded that PPV was successful for DME and its outcome (especially for anatomical results) could be enhanced by ILM peeling, without increasing the incidence of complications either intraoperatively or postoperatively [9].

Abe et al investigated the actual role of the ILM in DME by performing 3-D OCT imaging preoperatively and postoperatively in 26 eyes of DME patients who underwent PPV. Non tractional VRI abnormalities were found in 15 of the eyes, while tractional abnormalities were found in the remaining 11 eyes. Using 3D imaging, they discovered fine folds in 11 out of 15 cases with non tractional interfaces. VRI was classified into three groups based on these observations. Smooth retinal surfaces were visible in both tomography and 3D imaging in group 1. A smooth retinal surface was only visible in group 2's tomography, but 3D imaging revealed small folds in the retina. In group 3, tomography and 3D imaging revealed a tractional VRI with a noticeable EMM and/or taut posterior vitreous cortex. After peeling the ILM, the fine folds disappeared, the DME improved in group 2, and the CMT significantly decreased in groups 2 and 3. The presence of type IV collagen expression in surgically obtained specimens confirmed that the fine folds involved the ILM. They suggested that the proper indications of PPV in DME could be ascertained by only using 3D imaging to detect the ILM tangential fine folds [8].

The favorable effect of additional ILM removal in PPV for cystoid DME was proved by Hoerauf et al's study, where the morphological changes were considerable but the visual improvement was unsatisfactory. BCVA improved by more than 2 lines in one of the 20 cases; remained the same in 17 cases; and decreased in the other two cases. As regard to the CMT, in group I (PPV alone), there was a slow improvement in the anatomical results but marked fewer effective results than in additional ILM removal where the mean preoperative CMT was 425.25μm and become 432.33μm three months postoperatively and 415.2μm at six months .Time has no considerable role. In group II (PPV and ILM peeling) the mean preoperative CMT was 442.13μm then become 352.62μm three months postoperatively, and 297.64μm six months postoperatively. They concluded that PVD alone slowly improved the anatomical outcomes, but it is markedly less effective than additional ILM peeling in the long-term [7].

No significant anatomical or functional difference did exist between the two groups at the conclusion of our study. Nevertheless, ILM peeling is not a challenging technique, is not accompanied by significant added complications, and may be recommended for releasing tractions or reducing the risk of re-proliferation of the EMM in the long-term scope.

In our recent study, we found a considerable negative correlation between BCVA improvement and the long-term blood glycemic control ( p = 0.007 ). This finding in accordance with Kumagai et al who studied the long-term results of PPV for non-tractional DME in 496 eyes (followed for 12 to 170 months) and reported a negative correlation between preoperative HbA1c and postoperative BCVA [27].

Yamada et al also studied the preoperative systemic or ocular factors relationships with BCVA or CMT before and after 6 months of the surgical procedure for 44 eyes who had underwent PPV with ILM peeling. They found that; while BCVA and CSMT were related to ocular factors before surgery, they were related to long-term glycemic control postoperatively [28].

The limitation of our study was related to its relatively old argument. However, this issue has not been fully determined yet. Most of recent meta-analysis suggested more studies and evaluations in the future. We suggest a comparative study included longer time of follow up and much more eyes. On the other hand, our research performed at the same place on the same ethnic group of people and surgeries were done by one surgeon with the same steps except only ILM peeling for group (B). All vitreous cavities were left fluid-filled. No usage of steroids in any step of the operation. Instead, we used a double staining technique with vital dyes. These points give more strength to our study.

By the end of the study, the vision is significantly improved in both non-ILM and ILM peeling groups with insignificant differences between them. CMT also decreased significantly at the end of the study in two groups. There is no anatomical or functional significant difference between two groups at the end of the study. The postoperative BCVA was lower in patients with poor glycemic control (high HbA1c) prior to the surgery, while the postoperative retinal thickness was thicker in patients with higher HbA1c.

BBG: brilliant blue G dye; BCVA: best corrected visual acuity; CMT: central macular thickness; DM: diabetes mellitus; DME: diabetic macular edema; DR: diabetic retinopathy; EMM: epi-macular membrane; FA: fluorescein angiography; PPV: pars plana vitrectomy; HbA1c: glycosylated hemoglobin; ILM: internal limiting membrane; LogMAR: logarithm of minimum angle of resolution; NPDR: non proliferative diabetic retinopathy; PDR: proliferative diabetic retinopathy; PVD: posterior vitreous detachment; TRD: tractional retinal detachment; VEGF: vascular endothelial growth factor; VMI: vitreomacular interface; VMT: vitreomacular traction; VTDRS: vision-threatening diabetic retinopathy.

Ethics approval and consent to participate

All procedures performed in studies involving human participants were in accordance with the ethical standards of Al-Azhar Medical Research Ethical Committee and with the 1964 Helsinki declaration and its later amendments. The ethical approval was obtained from the ethics committee of Al-Azhar Medical Research Ethical Committee, Cairo, Egypt. A written informed consent was obtained from all individual participants included in the study.

Consent for publication

Not applicable.

Availability of data and materials

The datasets used during and/or analysed during the current study are not available due to privacy/ethical restrictions but are available from the corresponding author on reasonable request.

Competing interests

The authors declare no competing financial issues.

Funding

The study was supported by Al-Azhar University Hospitals in cooperation with The Egyptian Knowledge Bank (EKB).

Authors’ contributions

AAAK: acquired and analyzed the data, drafted the initial manuscript, and revised the manuscript. MMA: He performed surgeries, conceptualized and designed the study, and collected data. AHH: conceptualized and designed the study, coordinated, and supervised data collection, analyzed the data, critically reviewed the manuscript, and revised the manuscript. All authors read and approved the final manuscript.

Acknowledgements

None.

Author details

¹Assistant lecturer of Ophthalmology, MSc (Ophthalmology), Faculty of Medicine, Al-Azhar University, Cairo, Egypt. ORCID number 0000-0003-4632-8506. ²Assistant professor of Ophthalmology, MD (Ophthalmology), Faculty of Medicine, Al-Azhar University, Cairo, Egypt. ORCID number 0000-0002-0703-177X. ³Professor of Ophthalmology, PhD (Ophthalmology), Faculty of Medicine, Al-Azhar University, Cairo, Egypt.

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No competing interests reported.

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Pars Plana Vitrectomy for Tractional Diabetic Macular Edema with or without Internal Limiting Membrane Peeling

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Background

Methods

Patient selection

Preoperative assessment

Surgical procedures

Postoperative follow up

Statistical analysis

Results

Discussion

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