Retinal Displacement After Pneumatic Retinopexy Versus Vitrectomy for the Management of Primary Retinal Detachment

Rhegmatogenous retinal detachment (RRD) is an acute, sight threatening condition, with an incidence of approximately 10 per 100,000 people.

Without surgical intervention by a vitreoretinal surgeon, retinal detachment almost invariably results in permanent sight loss in the affected eye. There is an increased risk of delayed visual rehabilitation the longer the wait for surgery. Both of the treatments under investigation are widely used and accepted by vitreoretinal surgeons.

Interventions for retinal detachment:

1. Pneumatic retinopexy (PnR) has been employed to repair retinal detachments since the late 1980s and is a minor surgical intervention, carried out in a treatment room. The initial success rate (i.e. the proportion of patients in whom the retina becomes attached after one treatment) is quoted as approximately 70%. PnR is carried out under topical or local anaesthetic (a freezing injection under the conjunctiva, the superficial skin on the eye). The procedure involves injection of a small gas bubble into the eyeball via a fine needle. This step takes a maximum of 15 minutes. Two gases can be injected into the eye: perfluoropropane (C3F8), which lasts 6 weeks, and sulfahexafluoride (SF6), which lasts about 2 weeks. Both are non-toxic, equally effective, have been validated for this use, and are widely used amongst retina surgeons in the world. After injection of the gas bubble, the patient is required to maintain a strict 'head posture' (for example, head tilt to left) for up to 10 days. The purpose of this 'head posture' is to align the gas bubble (which floats within the eye) to the retinal tear. The buoyant force of the gas bubble, as well as its surface tension, act to reattach the detached retina over several days. The gas bubble spontaneously dissipates after 2-6 weeks, depending on the gas selected. Additionally, laser treatment or cryotherapy is carried out either before or 1-2 days after injection of the gas bubble, to secure the retinal tear. Both laser and cryotherapy are widely accepted methods of securing the tears in the retina and both are considered equally safe and effective. In patients where the retina does not reattach with PnR alone, vitrectomy surgery (PPV) or repeat PnR is needed (see below). However, the minority of patients who go on to need repeat treatment encounter similar final anatomical success rates and will experience the same gain in vision as those patients who underwent PPV in the first place.
2. Vitrectomy surgery (PPV) involves 'keyhole' surgery to the eyeball, via three tiny (23/25 gauge) incisions to the sclera. This procedure is carried out in the operating room, under regional anaesthetic plus sedation. During PPV, the vitreous gel is removed from the eye using a fine metal instrument called a 'vitrector'. A large gas bubble (same gases as mentioned for PnR) is injected (to reattach the retina, as in PnR), and laser or cryotherapy is applied around the retinal tear to secure it (as in PnR). After treatment, the patient will be required to maintain a 'head posture' (face down for 24 hours). The gas bubble reabsorbs after 2-6 weeks, depending on the gas selected. The surgery takes 1-1.5 hours. The success rate (i.e. the proportion of patients in whom the retina becomes attached after one treatment) is reported as being as high as 90% in the scientific literature.

Both of the treatments may be associated with complications such as bleeding, infection, increased intraocular pressure or cataract. The risk of a sight threatening complication such as a severe intraocular infection or hemorrhage is less than 1:1000 (for both procedures). The risk of cataract development (clouding of the lens, requiring cataract extraction surgery) is less than 10% for PnR and at least 70% for PPV.