Prognostic factors in Pars Plana vitrectomy for Proliferative Diabetic Retinopathy

Prognostic factors in Pars Plana vitrectomy for Proliferative Diabetic Retinopathy Rukmangathan K.1*, P. N.2, Ravichandran R.3, Chandrasekaran R.4 DOI: https://doi.org/10.17511/jooo.2020.i06.01 1* Keerthivarman Rukmangathan, Associate Professor, Department of Ophthalmology, Annapoorana Medical College, Salem, Tamil Nadu, India. 2 Nandhakishore P., Consultant, Aravind Eye Hospital, Theni, Tamil Nadu, India. 3 Ramusiddharthan Ravichandran, Consultant, Sri Ramanamaharishi Eye Hospital, Thiruvannamalai, Tamil Nadu, India. 4 Ranjan Chandrasekaran, Consultant, Annai Eye Hospital, Ramanathapuram, Tamil Nadu, India.

Although sophisticated instruments and lasers have been developed for vitreoretinal surgery still the patient needs to undergo 20 gauge sclerotomies and postoperative morbidity because of sutured wounds. Sutureless self-sealing sclerotomies were initially proposed by Chen [12] has gained in popularity.
Over the years modifications in vitrectomy instruments such as 23-gauge transconjunctival sutureless vitrectomy (TVS) introduced by Eckardt [13] in 2005 which had less instrument flexibility allowing greater ocular rotation and the ability to perform a more complete peripheral vitrectomy.
In this present investigation, an attempt has been made to document the prognostic factors in PPV in patients presenting with diabetic retinopathy (DR) at a tertiary eye care facility in Tamil Nadu, India.
Also, the surgical outcomes and complications of standard 20 gauge vitrectomy are compared with 23-gauge transconjunctival sutureless vitrectomy.  All obtained data were analyzed by using an unpaired student t-test for intergroup analysis of mean and the Chi-square test was used for proportions. Differences between values were considered to be statistically significant if P-value is ≤ 0.05.

Results
A total of 49 patients enrolled in the study, 38 (78%) patients were male and 11 (22%) patients were female (Figure 1). The mean age of the patients was 53.06 ± 7.5 years (range 36 to 71 years) and Pars plana Vitrectomy was performed for the right eye in 29 instances (59%) and for the left eye in 20 instances (41%). (Figure 1).  (Table 1).     [15].
Various studies related to indications for vitrectomy in diabetic retinopathy by Thompson et al [16], Tony et al [17], and Helbig et al [18], found that severe non-clearing vitreous hemorrhage, tractional retinal detachment (TRD), combined tractional and rhegmatogenous retinal detachment and fibrovascular proliferation as indications for vitrectomy due to complications of diabetic retinopathy, dense pre macular hemorrhage. In the current study, the most frequent indication for PPV was found to be non-clearing vitreous hemorrhage (63%) (which was similar to other studies), followed by combined tractional retinal detachment with vitreous hemorrhage (18%); 12% of eyes had TRD, 2% of eyes had recalcitrant macular edema and another 2 % had combined tractional and rhegmatogenous retinal detachment.
Coming to surgical procedures used, Qamar et al [19], performed PPV for patients with TRD without retinal break peeling with endolaser. These authors concluded that TRD without retinal breaks can be treated by PPV without internal tamponade. In another study, Castellarin et al [20] concluded that PPV with silicone oil infusion is useful in severely affected eyes with PDR even in the presence of rubeosis iridis and neovascular glaucoma, and also in cases of previously failed vitrectomy. In yet another study, Canan et al [21] observed that the combined operation of PPV, phacoemulsification, and intraocular lens implantation was safe and effective Eye in a 20-gauge group and none in the 23-gauge group and a combined tractional with a rhegmatogenous retinal detachment was noted in one eye in23 the gauge group. In the current study, the difference in the rate of complications between 20 gauge versus 23-gauge vitrectomy was not statistically significant.
Surgical outcomes of PPV for diabetic retinopathy complications may be varied. Machemer et al [28] in their study on vitrectomy for diabetic retinopathy, found that visual improvement occurred in 59% of the eyes in which the retina was stable, while in 25% of patients there was retinal detachment, which resulted in visual improvement in only 46% of the eyes; the total success rate was 51%. The main causes for bad prognosis were rubeosis of the iris and posterior retinal detachment with 42% of all eyes exhibiting some degree of rubeosis of iris. Most of the preoperative eyes (71%) had rubeosis presented postoperatively also with rubeosis. In another study, Amar et al [19] observed successful retinal reattachment in 92% of the operated eyes; in those patients, the retina was stable and attached till the end of one-year follow-up improvement in best-corrected visual acuity was seen in 75%; mean improvement in best-corrected visual acuity was 2.00+1.24 lines at baseline to 1.24+1.22 (p <0.05) at the end of follow up. Dong et al [26] in their study compared clinical outcomes between 23 trans-conjunctival sutureless vitrectomy (TSV) with standard 20 gauge vitrectomy where they compared best-corrected visual acuity between the two groups.

Limitation Conclusion
The authors concluded that there was no difference in best-corrected visual acuity between the two groups at each follow-up visit and concluded that 23 gauge (TSV) is as effective for proliferative diabetic Retinopathy as standard 20-gauge vitrectomy. In the present study, 90% of the patients were found to have stable, well-attached retina postoperatively, while 6% of the patients had a retinal detachment and 4% had persistent macular edema at the end of the follow-up period. These results were comparable to those of other studies, suggesting that PPV is a useful and successful surgical technique in PDR.
Moreover, visual acuity improved significantly after surgery (p < 0.0001) and this improvement was seen in both 20-gauge group (p = 0.0004) and in 23-gauge group (p = 0.0005). There was no significant difference in best-corrected visual acuity noted between the two groups, however, eyes that underwent 23-gauge vitrectomy tended to gain vision earlier when compared to eyes that underwent 20-gauge vitrectomy).

What does the study add to the existing knowledge
Preoperative intravitreal injection of bevacizumab is useful in reducing early post-operative vitreous hemorrhage following PPV. 23-gauge TSV is as effective in treatment for proliferative diabetic retinopathy as standard 20-gauge vitrectomy. Visual acuity following gas tamponade should be assessed since most of the eyes underwent PPV with silicone oil. Eyes that underwent 23-gauge vitrectomy tended to gain vision earlier when compared to eyes that underwent 20-gauge vitrectomy. Tropical Journal of Ophthalmology and Otolaryngology 2020;5(6)