Giant Retinal Tear

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Chapter 109 Giant Retinal Tear

Introduction

Giant retinal tear by definition is a retinal tear of more than 90° circumferential extent.1 Since the posterior vitreous is detached, the vitreous gel is adherent to the anterior flap. Hence, the posterior flap has a tendency to fold over. In contrast, in a giant retinal dialysis the retina is either torn at the ora serrata or there is a break in ciliary epithelium, with the vitreous being adherent to the posterior retina.2 Thus, the posterior flap does not have the tendency to fold over, since it is supported by the vitreous gel.

The management of fresh giant retinal tear is an emergency. The delay in surgical intervention could lead to significant proliferative vitreoretinopathy (PVR) changes jeopardizing reattachment of the retina and eventual visual gain. Before the introduction of perfluorocarbon liquids by Stanley Chang,3 the management of giant retinal tears was challenging and resulted in limited success. The present day management of giant retinal tear is reasonably straightforward, with predictably good success rate.

Etiology

Most giant retinal tears are idiopathic in origin with males being at higher risk. Traumatic giant retinal tears are commonly located in the upper nasal and lower temporal quadrants and are again commoner in males. In a population-based study in the UK, Ang et al. have reported an annual incidence of 0.091 patients per 100 000 population.4 Most of the cases were idiopathic (54.8%) and males predominated (71.7%).4

The association with high myopia is well established.5 Of all retinal detachments in Marfan syndrome, 11.3% have been reportedly caused by giant retinal tears.6 Retinal detachment, especially due to giant retinal tear has been identified as an important complication of Stickler syndrome.7 Other diseases associated with occurrence of giant retinal tear include the Ehlers–Danlos syndrome,8 lens coloboma,9 and aniridia.10

Pathogenesis

Schepens first described the important role played by the vitreous in giant retinal tear. Central vitreous liquefaction is associated with condensation in the peripheral vitreous base that leads to traction on the peripheral retina.1 As traction progresses, it is evident clinically as spreading “white-without-pressure.” Later, transvitreal contraction of the cortical gel occurs, tearing the retina along the vitreous base in a zipper fashion. Occasionally, multiple horseshoe-shaped tears may form along the posterior vitreous base and coalesce to form a giant retinal tear. Radial extensions (horns) can occur at the two ends of the giant retinal tear. Eyes with radial extension invariably have some amount of vitreous hemorrhage since the tears cut across larger blood vessels posteriorly.

A giant retinal tear nearing 180° in circumferential extent has a tendency to fold over. The size of the giant retinal tear also has an effect on the amount of retinal pigment epithelium that gains access to the vitreous cavity, thus increasing the risk of PVR. Giant retinal tear occurring after penetrating injuries has high risk of PVR while giant dialysis tends to progress very slowly.

History of management of giant retinal tear

The management of giant retinal tear can be divided conveniently into pre- and post-perfluorocarbon liquids (PFCL) eras. Most techniques used in the pre-PFCL era are of historic importance. However, a brief mention of these techniques is relevant in the overall understanding of the management of giant retinal tear. The primary problem faced by the surgeon was the gravity-driven tendency of the flap of the retinal tear to fold and fall back. Scleral buckles have been done for smaller extent of the tears (around 90°). A relatively shallow, but broad buckle was aimed at, so that the tendency for the flap to slip back is reduced and the inevitable central sagging of the flap is accommodated on the broad buckle.17 Attempts were also made to rotate the patient and to reposition the retinal flap with the help of an air bubble.18 Vitreoretinal surgery helped mobilize the inverted flaps of large giant retinal tears but the surgeon still faced difficulty in unrolling the same and fixing it in position. One strategy was to divide the giant retinal tear into smaller segments by pinning the edge of the tear down to the RPE/choroid complex using retinal tacks19,20 or sutures.21 This enabled routine fluid–air exchange to fix the retina without slippage of the retinal flap. Another technique involved fluid–air exchange in prone position. After a vitrectomy (and sometimes placement of buckle), the sclerotomies were closed and the patient was turned prone. Without contaminating the operative field, fluid–air exchange was then performed, with the air injection being done in front of the optic disc and fluid being evacuated from the anterior chamber.22 The air progressively attached the retina posteroanteriorly. The patient is repositioned in the supine position and internal tamponading agent was injected – gas or silicone oil as the case may be. Among all these techniques, perhaps the best attachment of the retina with no folds or slippage was seen with prone fluid–air exchange following vitrectomy. With the use of PFCLs, the surgery has become much simpler.

Preoperative evaluation and planning

A thorough evaluation of both the anterior and posterior segments is important to plan the surgery properly. Corneal and lens status must be noted. Perforating injury-related retinal detachments with vitreous incarceration and giant retinal tear can have associated corneal problems such as generalized haze due to edema, opacity, Descemet’s membrane folds, etc. The lens could be subluxated due to the blunt trauma and could be also cataractous.

Pseudophakic eyes can also have specific problems. The intraocular lens (IOL) could be tilted or subluxed (especially in eyes that had capsular dehiscence and vitreous disturbance during cataract surgery). Deposits on the IOL and posterior capsule opacification can interfere with surgery. A decision as to the need to remove the IOL should be taken based on this evaluation. There is however no justification to remove a well-placed IOL.

The intraocular pressure (IOP) could be low, normal or high. A low to very low IOP is seen in relatively recent giant retinal tears and often associated with choroidal detachment. One may chose to treat such cases with a course of systemic steroids for a few (3–5) days before performing the surgery. High intraocular pressure is rare at the time of presentation with acute giant retinal tear even in eyes with preexisting glaucoma. However, eyes with traumatic dialysis can have persistent high pressures despite the presence of retinal detachment. Following reattachment of the retina, one should anticipate an acute rise in intraocular pressure. Hence, arrangements for frequent IOP monitoring must be in place. It is only rarely that a glaucoma surgery needs to be combined with the retinal reattachment surgery.

The posterior vitreous will be found to be detached in cases of giant retinal tear, unlike in dialysis. In eyes that had blunt injury, the vitreous base can be avulsed and is seen as a rope-like structure near the pars plana. In eyes with perforating injury or following cataract surgery misadventure, the vitreous could be incarcerated in the wound and is seen as a transvitreal membrane. The giant tear or dialysis is seen usually in the opposite quadrant.11

The extent of retinal detachment can vary. A dialysis can be associated with chronic partial detachments of the retina with high water marks, while giant retinal tear is usually associated with a more rapidly spreading retinal detachment. Eyes with around 90° tears are characterized by sagging of the center of the tear posteriorly but do not show inversion of flap. However, if the two ends of the giant retinal tear trail significantly posteriorly (horns), the retinal flap that is enclosed in between, can fold back. Retinal tears that are nearing 180° circumferentially will show a tendency to fold back. The inverted flap can sometimes obscure the disc (Fig. 109.1). The edge of the tear usually is scrolled inwards despite lack of obvious PVR elsewhere. The pars plana epithelium can be detached in the area of tear and sometimes beyond, due to the vitreous base traction. The anterior flap of the retina can harbor lattice degeneration. Additional horseshoe tears can be seen in other quadrants near the posterior vitreous base. A macular hole can coexist – especially in eyes that are highly myopic or where the giant retinal tear is a result of blunt injury. Significant pigment dispersal is seen in the vitreous cavity and pigment is often seen adherent to the surface of the retina. A traumatic dialysis is often associated with evidence of damage to the RPE and choroid at the site of the ora serrata.

Ultrasonographic diagnosis of giant retinal tear

In eyes with opaque media, giant retinal tear can be suspected on ultrasonography.23 A suggestive feature is a discontinuity noticed anteriorly in the retinal echo and extending more than one quadrant. Double linear echo would be seen near the disc due to the close proximity of the two layers of the retina; one representing the flap of the giant retinal tear and hence discontinuous with the globe contour and the other representing the detached retina and hence continuous with the globe contour (Fig. 109.2).

Role of nonsurgical treatment

Role of simple scleral buckling

In the present era, wherein vitreous surgery has become the desired approach to fix even simple retinal detachments with horseshoe tears, most surgeons would not perform simple scleral buckle for giant retinal tear of any degree. The role of scleral buckle is perhaps restricted to the cases of giant retinal dialysis. In the absence of a vitreous detachment and the usually young age of the patient, a vitrectomy approach may not be ideal in cases with dialysis. A scleral buckling would suffice in most such cases.