There is a global increase in the prevalence of diabetes.¹ End-stage diabetic eye disease is the most important cause of severe visual impairment in the working age-group. Tractional retinal detachment (TRD) and non-clearing vitreous haemorrhage (NCVH) are two complications of proliferative diabetic retinopathy (PDR)² which are treated with vitreoretinal surgical repair. Over the last 10 years we have seen improvements in surgical techniques such as the use of wide angled viewing systems, use of endolaser^3,4 and use of vascular endothelial growth factors (VEGF) inhibitors such as bevacizumab⁵ and ranibizumab. These have improved visual outcome since the first reported randomized controlled diabetic vitrectomy study.⁶

This report aims to highlight the evolving trends in surgical management of this complex vitreoretinal disorder and provides some insight into current practice and evidence-based medicine. We will also report our own experiences and share 10 year anatomical and visual outcome in patients who underwent 20-gauge (20G) pars plana vitrectomy (PPV) for complications of PDR under the supervision of a single surgeon (THW) at a teaching hospital in south east London, UK.

Vitrectomy surgery

20G PPV with slight modifications has remained the gold standard for over 3 decades in the management of complications due to PDR. However, the last decade has seen the invasion of smaller gauge (23/25G, micro-incision) vitrectomy instruments. In 2002, Fujii et al.⁷ introduced the first commercially available, sutureless, transconjunctival 25 (0.50 mm)-gauge vitrectomy system and subsequently in 2005, Eckardt⁸ described a 23-gauge transconjunctival sutureless system. The current availability of 20-, 23- and 25-gauge vitrectomy systems provides surgeons with enhanced flexibility but creates a variety of questions concerning the respective advantages.

Smaller gauge transconjunctival sutureless vitrectomy offers theoretical advantages of shorter surgical time, less postoperative inflammation, faster visual recovery and improved patient comfort. But these benefits are balanced in complex vitreoretinal adhesion and fibrovascular proliferations — seen in PDR as a result of altered fluidics with reduced flow through the smaller probe as compared to 20G. Advances such as 25G ultra high speed PPV machinery⁹ that has better fluid dynamic control, high speed cutting rate (5000 cuts per minute) and viscodissection assisted microincision vitrectomy¹⁰ offer new options in microincision vitrectomy.

Anatomical and visual results following PPV in complications due to DR with different gauges of vitrectomy instrumentation are comparable. In a retrospective study of 101 eyes by Park et al.¹¹ no beneficial effects on anatomical and visual outcome were seen after direct comparison between 20- and 23-G PPV. However, there were more cases of hypotony in the 23-G PPV group.

Figure 1: Newer cutters are narrower gauge with the orifice closer to the tip of the shaft.

Innovations:

• The introduction of chandelier illumination has provided the surgeon with the means to perform bimanual dissection of membranes. This has eased dissection of tractional retinal detachment (TRD) especially in the presence of mobile retinal detachment.
• Modern high speed cutters have the orifice of the cutter nearer the tip of the shaft allowing the surgeon close shaving of some membranes.
• High speed cutters allow close shaving of the membranes with less chance of incising the retinal because smaller more frequent bites of the tissue are taken. (Figure 1)