Inadequate wound closure and subsequent hypotony were proposed as a possible risk factor in the first study reporting endophthalmitis following sutureless vitrectomy [12]. The sclerotomy leakage and hypotony would allow ingress of microorganisms from the ocular surface into the eye. Studies conducted on port site dynamics have shown that there is a definite risk of ingress of material from the ocular surface into the eye in sutureless ports as compared to those that have been sutured [19–22].

Endoscopic evaluation of autopsied vitrectomized eyes has shown that vitreous is often incarcerated at the port sites [23, 24]. This incarcerated vitreous can prolapse out of the wound and rest in the sub-conjunctival space especially following sutureless PPV. The microorganisms can potentially migrate along the vitreous blob into the intraocular space predisposing the eye to endophthalmitis.

The type of intraocular tamponade can also have a bearing on the risk of endophthalmitis. This is because of differential surface tension properties. As silicone oil or gas has a greater surface tension than water, both oil and gas are better tamponading agents than balanced salt solution (BSS). The risk of wound leakage is thus lesser when the tamponading agent is either gas or oil as against BSS. In a retrospective series, we have shown that the odds of post-vitrectomy endophthalmitis is 8.2 when the final tamponading agent is BSS as opposed to oil or gas [25].

Vitreous contamination by microorganisms has also been proposed as a risk factor for endophthalmitis. It has been shown that the vitreous contamination is significantly higher in sutureless transconjunctival PPV as compared to 20G PPV [26, 27]. The lesser risk of the instrument contamination in 20G surgeries was attributed to a lesser contact of the 20G instruments with the conjunctival surface. Surgeon learning curve can also increase the risk of endophthalmitis, particularly at the transition phase of the surgeon from sutured to sutureless PPV [28].

The clinical features in post-PPV endophthalmitis are very similar to those seen in post-cataract surgery endophthalmitis. Most presentations are very acute with patients largely presenting within 48 h of the surgery with pain, redness, watering, and decreased vision. In the largest cohort of these cases, we have shown that the median time interval between vitreous surgery and the onset of endophthalmitis is 1.5 days [25]. Most cases do not have a favorable final visual outcome due to the underlying primary retinal disease.

The overall culture positivity in post-PPV endophthalmitis has been quite varied over the years. Nearly 50% of cultures across studies are culture positive. The commonest organism is coagulase-negative Staphylococci [29–33] (Table 15.3).