The author developed a concept known as interface vitrectomy, which is based on performing a variety of techniques with air, perfluoro-octane (PFO), or silicone oil in the eye. Vitreous removal, forceps membrane peeling, scissors segmentation/delamination, diathermy, internal drainage of subretinal fluid, and retinectomy all work well with these agents in the eye. The term “interface” was selected to emphasize that the vitreous cutter and other tools must be placed outside the air, PFO, or silicone oil bubble. Air and silicone oil float in infusion fluid, but PFO sinks. It is crucial to understand that there is always a fluid layer at the retinal surface except with PFO in the eye.

The retina is more than 90% water; retina vitreous, epiretinal membranes, subretinal fluid, and blood are all immiscible in air, silicone oil, and PFO. The author introduced the concept of endophotocoagulation “under” air more than 4 decades ago.¹ Coll et al also introduced membrane peeling “under” PFO for proliferative vitreoretinopathy (PVR) cases in 1995.² Interface vitrectomy prevents an increase of subretinal fluid during traction removal, allows realistic assessment of remaining traction, confines bleeding to the interface, and stabilizes the retina. Air stabilizes the retina by spring dampening, silicone oil by viscous dampening, and PFO by inertial (F=ma) and gravitational (high specific gravity) effect. Twenty-five gauge vitrectomy is ideal for these cases, if the surgeon is careful to avoid applying vacuum while the port is in silicone oil. Moderate amounts of subretinal silicone can be removed in conjunction with retinectomy and epiretinal membrane removal without plugging the vitreous cutter by using a 650 mmHg vacuum.

EVOLUTION OF FLUID–AIR EXCHANGE

Prior to the development of fluid-air exchange by the author, fluid was withdrawn through a single needle, which was then used to inject gas into the collapsed eye after turning a stopcock. Air–gas exchange is best performed at the end of the case, after fluid–air exchange and endolaser retinopexy. Similarly, most surgeons perform fluid–air exchange and endolaser retinopexy before air–silicone exchange. Some surgeons recommend fluid–silicone exchange and omit the fluid–air exchange step. The fluid–silicone exchange approach can make visualization as well as complete reattachment before endolaser retinopexy more difficult. Fluid–perfluorocarbon exchange is preferred to fluid–air exchange before perfluorocarbon placement in retinal detachment, proliferative vitreoretinopathy, and giant break cases. Perfluorocarbon–gas or perfluorocarbon–silicone exchange is performed after laser retinopexy unless medium-term PFO is planned.

VITRECTOMY UNDER AIR

Certain portions of the vitreous surgery procedure can be completed after fluid–air exchange. Very rarely, severe bleeding cannot be controlled with combined extrusion and bipolar diathermy or endophotocoagulation. If internal fluid–air exchange is performed in such an instance, the bubble will confine the blood to the bleeding site, improving visualization, and thereby enabling diathermy or endophotocoagulation to the bleeding vessel.

The air–vitreous interface is quite visible, which facilitates removal of residual vitreous by placing the cutter port barely into the vitreous just outside the interface. The air–vitreous interface facilitates visualization of residual vitreous after an exchange is performed. The author often places the vitreous cutter port just outside the air–vitreous interface and performs additional vitrectomy under air. This is can be done with PFO and silicone oil as well, which is termed “interface vitrectomy” (Figures 1 and 2).

Forceps membrane peeling, scissors segmentation and delamination, subretinal surgery, retinectomy, laser endophotocoagulation, and foreign body removal can all be performed under air if the eye being operated is not an aphakic eye with striate keratopathy. Fogging of intraocular lenses (IOLs) if a YAG capsulotomy has been performed is a serious limitation of this method. Silicone IOLs fog much more than acrylic or PMMA lenses, because they have a higher thermal mass and higher posterior capsule opacification rates. Prior YAG capsulectomy and intraoperative removal of the anterior vitreous cortex creates the fogging problem by allowing air access to the IOL surface. Intraocular lenses fog because they have significant thermal mass, they are cooled by room temperature infusion fluid, and the air in the eye is saturated with water vapor. Although a viscoelastic can be injected against the posterior surface of the lens to reduce fogging, this creates a morphed image, increases cost, and probably increases silicone oil emulsification. Air–silicone exchange can be used, endophotocoagulation performed under oil, and the oil removed in several weeks. Perfluoro-octane eliminates this problem by facilitating removal of subretinal fluid and performing endophotocoagulation before PFO–gas exchange.

REOPERATIONS WITH SILICONE OIL PRESENT

For more than 35 years, the author has reoperated all silicone oil cases for epimacular membrane or redetachment from proliferative vitreoretinopathy without removing the oil. The MedOne silicone oil injection cannula placed over a nonvalved cannula can be used with 3-port technique to supplement the oil in retinal detachment cases; 2-port technique can be used for epimacular membranes, which usually do not require adding oil. The author never removes silicone oil when performing reoperations, because procedures such as forceps membrane peeling, scissors segmentation/delamination, retinectomy, and laser are all effective “under” silicone. Silicone oil is infused to replace volume created by removal of subretinal fluid and aqueous humor between the oil and retinal surface. The suction (vacuum) is used at the highest setting (650 mmHg). Advantages or reoperation without removing oil include the following:

• Unlike when using air, no IOL fogging occurs.
• The liquid perfluorocarbon step is eliminated, which reduces cost and prevents subretinal PFO.
• Retinal tension and traction against interfacial surface tension force can be realistically determined.
• The procedure is faster, therefore there is less trauma, less inflammation, less anesthesia risk and lower labor cost.
• There is viscous dampening of retinal motion.
• Oil contains bleeding.

CONCLUSION

Vitreoretinal surgeons should consider performing reoperations for PVR and epimacular membranes without removing silicone oil. This approach has many advantages and no disadvantages. Vitrectomy “under” air has many advantages as well is very useful in vitrectomy for rhegmatogenous detachment. RP

REFERENCES

1. Charles S, Calzada J, Wood B. Vitreous Microsurgery. Williams and Wilkins: Baltimore, MD:2010.
2. Coll GE, Chang S, Sun J, Wieland MR, Berrocal MH. Perfluorocarbon liquid in the management of retinal detachment with proliferative vitreoretinopathy. Ophthalmology. 1995;102(4):630-8; discussion 638-9. doi:10.1016/s0161-6420(95)30975-x