Periorbital anesthesia, with the migration of retina surgery to ambulatory surgery, is the most frequent choice for anesthesia.

The most common complications associated with this type of anesthesia are globe penetration or perforation, retrobulbar hemorrhage, diplopia secondary to muscle injury, optic neuropathy, and respiratory arrest for inadvertent brain stem anesthesia during dural sheath inoculation [4, 5]. In case of retrobulbar hemorrhage, control of hemodynamic is imperative, to preserve and minimize optic nerve injury, and in case of large retrobulbar hemorrhages, canthotomy may be necessary [6].

Each step of scleral buckling procedure can be affected by several complications. Some of these intraoperative complications are quite easy to manage and do not compromise the anatomical and functional outcome. Other complications can be potentially devastating for the visual recovery and challenging to manage.

At the beginning of the surgery, a 360° conjunctival peritomy is performed in order to expose the operative field. This maneuver is as essential as the placement of the buckle and the cryopexy.

A peritomy is combined with radial incision in the superonasal and inferotemporal quadrants to enlarge the circumference of the opened conjunctiva and to avoid tearing of the conjunctiva as this tissue is retracted to expose the sclera [7]. Isolating the entire muscles and avoiding splitting of the muscles belly are important to prevent diplopia, following scleral buckle. When the muscle hook is passed beneath the tendon insertion, it is important not to pass it posterior to the equator where it might damage the vortex veins. Also, when engaging the superior rectus tendon, the hook should be passed from the temporal toward the nasal directions to avoid engaging the superior oblique muscle, which extends in the opposite direction [7].

When the sclera is cleaned in all quadrants where retinal breaks are present and/or where scleral sutures will be placed, a careful inspection of the sclera for signs of marked scleral thinning (ectasia) is required in order to plan the most appropriate buckle approach [7]. Preexisting scleral pathology is a major risk factor for globe rupture during scleral buckling procedure [8]. Scleral thinning is more frequent in superotemporal quadrant and may appear as radial gray lines in the equatorial or pre-equatorial area or as a more substantial bulging of the sclera [7].

If a quadrant is too thin to accommodate a suture or a scleral tunnel, one may need to consider not anchoring the buckle in this quadrant, if the quadrant does not require a buckle to specifically support a break. Rarely, if the sclera is too tenuous, it could be necessary to abandon the scleral buckling procedure switching to vitrectomy [6]. Scleral rupture is a rare but serious complication of retinal detachment surgery. In the study by Tabandeh et al., reoperation after failed scleral buckling procedure and preexisting scleral pathology were identified as the main risk factors for this complication.

Inadvertent penetration of the sclera during scleral sutures placement has been reported to occur in about 5 % of the cases and is usually associated with high myopia and thin sclera [8]. In order to avoid this complication, it is important to adopt a proper suture technique: depress with the needle tip to obtain the initial depth; once the appropriate depth is obtained, flatten the needle to maintain this depth, and always be conscious of the needle depth throughout the entire pass. It is also important to avoid placing suture near vortex veins because of the risk of suprachoroidal hemorrhage.

When a scleral perforation occurs, this typically leads to drainage of the subretinal fluid, if the retina is detached, or to retinal perforations and hemorrhage, if the retina is attached. Under these circumstances, it is important to control the retina in order to evaluate the damage. The site of perforation should be treated with cryotherapy, and the scleral buckle position should be eventually modified in order to support the area of perforation. Perforation with inadvertent drainage of subretinal fluid is not necessarily a bad outcome, even if it can result in hypotony. Subsequent scleral sutures are more difficult to place in a hypotonous globe, and the risk of perforation increases [6]. In the eyes that have undergone previous RD surgery, scleral depression over the site of previously unnoticed suture penetration or cut-down sclerotomies or on an adjacent scleral explant may result in frank rupture.

Tissue glue may be used to facilitate the restoration of the globe. Scleral rupture can make the way to secondary intraoperative complication such as choroidal, subretinal, or vitreous hemorrhage and retinal incarceration [8].

Scleral buckle procedure outcome is directly dependent on the possibility to close and treat all the retinal breaks. A clear cornea and good pupil dilatation are necessary for adequate visualization of the fundus. If pupil constriction occurs during surgery because of sudden hypotony, a normal intraocular pressure can be restored by injecting BSS or gas through the pars plana. Mild pupillary constriction unassociated with hypotony can be resolved by the injection of epinephrine in a concentration of 1:10,000 or less into the anterior chamber. If the corneal epithelium gets cloudy during surgery, this should be removed to permit optimal visualization [7].

Cryotherapy is the most common method used to treat retinal breaks [9, 10]. Each retinal break should be surrounded by a 1–2 mm zone of contiguous cryotherapy application, trying to avoid refreezing of the same area. Cryotherapy application is terminated when a visible effect is seen in the pigment epithelium or the overlying retina. However, if the pigment epithelium freezes but the overlying detached retina does not, the application should be stopped to avoid excessive choroidal damage [7].

There are two main complications linked to cryotherapy. The first occurs when the cryoprobe shaft creates a false indentation, preventing the surgeon from appreciating the correct position of the tip of the probe that lies more posteriorly than expected. This event may result in inadvertent cryopexy of the posterior pole. The second complication can occur if insufficient time is allowed for the cryoprobe to thaw before it is moved. If the probe is moved while it is still frozen, the choroidal vessel may rupture, resulting in a subretinal hemorrhage or scleral avulsion with a consecutive scleral defect. In this case, if the sclera is healthy and the defect is small, a simple mattress suture can be applied. If the defect is large, or the sclera is ectasic, a buckle, with or without glue, can be sutured into place. Alternatively, donor sclera or pericardial patch graft can be sutured over the defect.

The drainage of subretinal fluid remains the step of the scleral buckling with the greatest potential for complications. The decision to drain subretinal fluid at the time of scleral buckling remains controversial. In a prospective randomized trial, Hilton noted that equally successful anatomical and functional results can be obtained either with drainage or non-drainage technique [11], even if there was a greater incidence of complications in the drainage group. On the other hand, in all the situations in which the buckle element alone is not able to create an appropriate indentation to close the retinal break, subretinal fluid drainage is necessary.

Careful selection of the drainage site will help to minimize potential complications. There are many factors to consider in selecting the location of drainage, including the distribution of subretinal fluid and the configuration of the detachment, the vitreoretinal and epiretinal membrane tractions, the location of retinal breaks, the configuration of the scleral buckle, and the choroidal vascularity. A good strategy to minimize retinal damage is to perform the drainage where the retina is the most highly detached (abundant subretinal fluid) and far from the retinal break.

In their study, Wilkinson and Regan reported that the main complications of drainage were loss of formed vitreous, vitreous hemorrhage, choroidal hemorrhage, retinal incarceration, and subretinal hemorrhage.

During the drainage, a cotton tip applicator is placed on the eye between the conjunctiva and the sclera to maintain normal IOP and to guarantee a complete outflow of the fluid. Bleeding from the drainage site can indicate possible choroidal, subretinal, or vitreous hemorrhage. A premature cessation of subretinal fluid drainage can be an indicator of possible retinal or vitreous incarcerations [12]. If retinal incarceration occurs during the drainage procedure, cryotherapy of the site and support with a scleral buckle are necessary [6].

Patterson and Ryan observed that complication rates of drainage of subretinal fluid can be reduced or detected earlier using a variant technique involving continuous intraocular monitoring during the drainage. This technique allows imminent complications to be detected before significant damage occurs, giving the possibility to the surgeon to get a better control over the drainage process. During drainage, if vitreous gel is observed to pass through the tear, the cotton-tipped applicator is rotated with pressure over the tear externally while verifying that the tear has been closed internally. If subretinal bleeding is noted, this can be arrested via external tamponade using the cotton-tipped applicator over the drainage site. The fluttering of retina during the process of drainage is useful as an indicator of an impeded drainage. The absence of retinal fluttering or the presence of retinal dimpling can indicate imminent retinal incarceration as the retina tends to dimple as it nears the choroidotomy site. If such an event is observed, the drainage site is massaged with cotton-tipped applicator in a rolling fashion, which will release the dimpled retina, preventing incarceration. Flattening of the retina against the RPE is observed as the residual SRF drains [12].