Giant Retinal Tears
Giant retinal tears need special mention because of some special characteristics—
- they rapidly lead to extensive retinal detachment,
- posterior flap has a tendency to roll over, fold or invert,
- they have increased risk of proliferative vitreoretinopathy (PVR),
- they require meticulous surgery to prevent complications,
- they have several ocular and systemic associations,
- fellow eye involvement occurs frequently, and
- re-detachments occur frequently in these cases.
Scott classified GRTs into three types based on their location with emphasis on pathophysiology and required management: equatorial, equatorial with posterior extensions, and oral. Equatorial GRTs are most common and have posterior extensions give posterior flaps extra mobility and tendency to invert or fold. Oral type is least common.
Schepens classified GRTs on the basis of etiology into idiopathic, traumatic, lattice-related, and iatrogenic types. Iatrogenic GRTs are known to occur after heavy diathermy or photocoagulation, pars plana vitrectomy (PPV), and refractive surgeries.
Based on the configuration, GRTs may be classified as—
- GRT without detachment;
- GRT with detachment with (a) at posterior flap, (b) rolled posterior flap, and (c) inverted posterior flap; and
- GRT with detachment with associated posterior extensions (radial rips) at or within the tear margin.
Various risk factors are described for giant retinal tears:
- Closed globe trauma
- Open globe trauma
- Cataract surgery
- Refractive Surgery
- Hereditary vitreoretinopathies
Rarely, buphthalmos and microspherophakia may be risk factors for GRTs.
Giant retinal tear occurs due to dynamic vitreous traction at areas of retinal abnormality which usually is an area of white-without pressure (WWOP). These areas have dense vitreous condensation and these increase in extent and density over time. The posterior border of WWOP is well defined with thick inelastic vitreous attachment. In addition, in such eyes, central vitreous liquefies early leaving a shrunken gel anteriorly and thin layer of vitreous cortex posteriorly. This gel contains dense bands attached anteriorly. PVD usually stops at this border leading to focal vitreoretinal adhesion and traction which subsequently may lead to a neurosensory retinal tear. The anteriorly directed vitreous traction then “rips” the abnormal retina circumferentially. Thus, the pathogenesis of GRT is similar to that of a smaller tear with difference only in the area of retinal abnormality.
Giant retinal tears are characterized by intense ocular inflammation due to blood retinal barrier breakdown. Hypotony develops quickly due to increased uveoscleral ouflow. Large bare retinal pigment epithelium (RPE) surface predispose to greater release of RPE cells which undergo transdifferentiation into myofibroblasts. Initially, the posterior flap is freely mobile but as PVR sets in, it becomes stiff and begins to roll. If left untreated, the size of GRTs increases with subsequent extension of the RD.
Fellow eyes of non-traumatic GRT cases often have vitreo-retinal pathology on presentation. However, there exists no evidence to support or refute use of 360 degree prophylactic treatment in the fellow eyes.
Freeman noted several high-risk characteristics in fellow eyes of giant retinal tears: high myopia (>-10 dioptres), increasing white without pressure areas, and increasing condensation of the vitreous base. The objective in management of such high-risk fellow eyes is to relieve the vitreous traction. A prophylactic scleral buckle in phakic eye with an attached retina is challenging and not without complication. 360 degree retinopexy, either in the form of cryopexy or laser photocoagulation may also be considered.
GRTs have associated RRD in about 44% to 92% cases. Presenting visual acuity depends on status of macula and configuration of GRT flap in relation to macula. Macula-off RDs usually have a visual acuity between counting fingers (CF) and light perception (LP).In the rest, if GRT flap covers the macula, poor vision is the norm.
Tobacco dusting in vitreous cavity is present in all cases. Vitreous haemorrhage may also result if tear involves the retinal vessels. Most GRTs have less than 180 degree circumferential extent. Location of GRT varies with infero-temporal and supero-nasal quadrants being commonly involved in traumatic cases .
The posterior flap may invert over the optic disc or the macula, thereby the full extent of the associated RD may not be ascertained. Posterior tears or radial rips may exacerbate the inversion of flap. PVR occurs quickly and frequently because of large area of RPE being exposed and increased liberation of RPE cells into vitreous cavity.
Fundus of the fellow eye should be examined thoroughly to look for any predisposing lesion and features of high myopia.
B scan ultrasonography of the posterior segment helps in determining the location and extent in cases with media obscuring vitreous haemorrhage. Also it can help to differentiate between GRT and GRD. A classical “double linear echo” sign is seen in GRT with two high-amplitude linear echoes, one extending from the optic disc and other usually lying almost parallel to it (inverted posterior flap).22 In addition, PVD and inverted posterior flap can be seen, which helps in differentiating it from GRD.
Axial length of the other eye should be done to determine if high myopia is the cause. Systemic examination should be done for relevant associated syndromes.
Distinction of GRT from giant retinal dialysis (GRD) is important. In GRD, retina dis-inserts from the ora serrata and vitreous remain attached to the posterior margin of the break, thereby a posterior vitreous detachment (PVD) is usually absent. This prevents the posterior margin in GRD from inverting. These detachments progress slowly. GRDs usually have a good prognosis as they are amenable to scleral buckling or even peripheral cryotherapy. 
On the other side, GRTs have strong vitreous adhesion to the anterior margin of break with posterior margin being free from vitreous attachment. Due to gravity and intrinsic retinal elasticity, posterior flap inverts over itself. GRTs pose numerous surgical challenges and outcomes are not as good as GRD. The detachments related to GRTs very quickly progress to total RDs.
Prior to the advent of pars plana vitrectomy (PPV), numerous strategies were adopted for management of GRT associated RRD like binocular occlusion, retinal incarceration, retinal tacks, trans-scleral suturing and scleral buckling.  However with introduction of PPV only, flap manipulation and complete vitrectomy became possible under direct wide-field visualization.
The surgical principles involved in the management include complete vitrectomy, unfolding of the retinal flap, sealing the tear with chorioretinal adhesion and providing long term intraocular tamponade.
Pars plana vitrectomy has a higher success rate than previously attempted surgeries and is the treatment of choice for GRT.    Despite advances in the surgical techniques and endotamponade agents, GRTs pose challenges due to their complex anatomy, risk of retinal slippage, formation of a new tear and extension of the existing tear due to proliferative vitreoretinopathy (PVR). Redetachments have been reported to occur in upto as high as 45% of the cases.
Conventional 20-G vitrectomy with PFCL use has been reported to have up to 94% final attachment rates in GRT associated RD. Smaller-gauge vitrectomy has evolved over time and has several advantages compared to conventional 20-G surgery including lesser retinal mobility, lesser vitreous traction, easy manipulation of tissues and PVR management, other than improved wound anatomy and reduced postoperative pain and inflammation.  25-gauge PPV can achieve excellent attachment rates in eyes with GRT associated retinal detachment.
A thorough vitrectomy of the vitreous base around its entire circumference is mandatory in the management of a giant tear. It is important to remove the condensed vitreous gel attached to the anterior edge of giant tear. Meticulous removal of the peripheral gel permits complete replacement of the vitreous volume by gas or silicon oil, decreases the likelihood of new breaks along the posterior insertion of the vitreous base, and decreases the occurrence of anterior PVR. Optimal visualization of the vitreous base is vital for its dissection. This is aided by maximal papillary dilatation pharmacologically, or with help of iris retractors, scleral indentation with cotton tipped applicator by the assistant or by using wide angle viewing system (panoramic viewing). Epiretinal membranes and proliferative tissue especially near the posterior edge of the giant tear should be removed thoroughly with the help of intravitreal forceps and vitrectomy cutter.
Lensectomy/ Lens aspiration
The main indications for lens removal in giant tears are cataract, lens subluxation and the presence of anterior proliferative vitreoretinopathy. Controversy remains as for need for clear lens extraction in fresh giant tears. The advantages of lens removal are visualization of the edge of the tear during fluid-air exchange, and improved access to the region of the vitreous base. The use of wide angle viewing systems for giant tear surgery improves the ability to see the peripheral retina under air in phakic and pseudophakic eyes. Thus, lensectomy to increase fundus visualization is not necessary. Many eyes with giant tears are highly myopic have large axial length and have broader pars plana region. This anatomic variation allows adequate shaving of the vitreous base with less risk of lens touch. The clears lens should be removed when it impedes adequate peripheral vitreous dissection.
Role of PFCL
The introduction of perfluorocarbon liquid (PFCL) supplanted all previous techniques for unrolling and repositioning inverted giant retinal tears. PCFLs having a high specific gravity with relatively low viscosity allow for precise, controlled and accurate repositioning of the retina with minimal manipulation
Once the retina is mobilized by membrane peeling, the inverted retinal flap is unfolded to expose the optic disc and posterior pole and liquid perfluoroactane is slowly injected over; the optic disc. Care is taken to prevent the injection of multiple bubbles by ensuring that the tip of injection needle is always within the PFCL bubble and the size of the bubble is gradually increased as subretinal and vitreous cavity fluid is displaced anteriorly and out of the eye.
With the retina fully attached under PFCL eight to ten rows of endophotocoagulation of 200-500 micron spot size are applied to the posterior edge and anterior retinal flap (Fig 40.3) and at least five rows are placed in the fundus periphery not involved in giant tear.
Cryotherapy can also be used to treat the GRT edges up to the ora, especially if it is very anterior.
The perfluorocarbon liquids can then be directly exchanged with gas or silicone oil. If the surgeon is sure of total vitreous base removal, and drying of free retinal edges, air-PFCL exchange followed by gas/silicon oil exchange may also be done. A flute needle (Janowitz ) with a soft silicone tip is positioned at the edge of the giant break as air-enters the vitreous cavity. The anterior retina is flattened as the bubble descends towards the perfluorocarbon meniscus. Fluid should be aspirated at the edge of the break, at the air/perfluorocarbon interface, to prevent posterior slippage of retina. Slippage may occur when persistent subretinal fluid is trapped posteriorly by descending air bubble causing the retina to slide. It's important to maintain adequate intraocular pressure during PFCL air exchange to prevent posterior slippage of retina.
Alternatively a direct silicone oil perfluorocarbon exchange can be done to decrease the chances of slippage of retina.. Both PFCL and silicone oil being hydrophobic extrudes fluid at the PFCL-oil interface. Presence of fluid at the PFCL–air interface at the area of tear allows entry of fluid into sub retinal space and cause tear slippage. A silicone oil infusion pump should be used during the exchange. With panoramic viewing, aspiration of perfluorocarbon liquid should be started at the edge of the giant tear using a silicone tipped blunt needle. As the silicone oil interface descends and covers; the edge of the tear, the liquid overcomes any residual intrinsic elastic forces that may result in posterior slippage. The aspirating tip is then placed just below the anterior surface of the PFCL as the oil continues to fill the vitreous cavity.
Role of encircling element
The use of encircling scleral band in GRT is controversial. Some studies have reported higher redetachment rates with encirclage due to redundant retinal folds, fish-mouthing and increased posterior retinal slippage, while others report a lack of encircling element to be associated with a higher rate of re-detachment.     Oil tamponade is usually used in the surgical management of GRT related RDs.
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