Fig. 21.1
Preoperative images of retinal detachment. (a) Class I: SD-OCT showing a detached macula with a retina of normal retinal and foveal thickness but the foveal depression is inverted. (b) Class II: SD-OCT showing a detached macula with relatively normal retinal thickness but with increasing loss of the foveal depression. (c) Class III: SD-OCT showing widespread edema in the external plexiform layer of the detached retina and a retained foveal depression. (d) Class IV: SD-OCT showing widespread retinal edema in the external plexiform layer with loss of the foveal depression
21.3.2 Changes at Ellipsoid Zone
The preoperative microstructural changes (IRS and OLU) in the detached macula appeared to be negatively correlated with postoperative recovery of the photoreceptor layer (as assessed by Ellipsoid Zone (EZ) integrity and external limiting membrane (ELM) status). It was furthermore shown that a preoperative foveal loss of EZ in the region of the detached macula was significantly correlated with poor postoperative visual acuity (Nakanishi et al. 2009), whereas others demonstrated that the mean postoperative best-corrected visual acuity in the eyes with photoreceptor layer abnormalities (disruption EZ) was significantly lower than in the eyes without photoreceptor layer alterations (Gharbiya et al. 2012).
21.3.3 Height of Macular Detachment
The height of macular detachment may also interfere with visual recovery in a negative way. In accordance with observations made on experimental models, in which photoreceptor degeneration increased with greater distance of the detached retina from the RPE (Machemer 1968), the extent of macular elevation has been shown to correlate with impaired functional recovery (Ross et al. 2005). More recent studies using OCT have however for the first time allowed objective and quantitative measurements of retinal detachment height. In a prospective study of 25 patients with macula-off retinal detachment, preoperative visual acuity was negatively affected by the height of the retinal detachment as measured by OCT (Hagimura et al. 2000).
Several other studies have also confirmed that the visual outcome becomes worse as the height of retinal detachment increases. Matsui and others have reported that the preoperative and 6-month postoperative visual acuity of eyes with a preoperative height of the retinal detachment ≥1000 μm were worse than the eyes with a preoperative height of the retinal detachment <1000 μm (Matsui et al. 2013; Joe et al. 2013). This observation can be explained by the fact that the greater the distance between the foveal cones and the RPE layer becomes, the less likely it is that the cones will receive adequate oxygenation and nutrition from the choriocapillaris and epithelial layer via diffusion across the subretinal space (Linsenmeier and Padnick-Silver 2000; Machemer 1968).
21.3.4 Duration of the Retinal Detachment
The exact duration of retinal detachment and its potential impact on visual acuity recovery has for decades remained a matter of debate (Burton 1982; Reese 1937). In a large retrospective study, which included several hundred patients, a maximal delay of 5 days for retinal detachment repair was determined adequate clinically without incurring undue risks for visual acuity recovery. A more recent large prospective study of 100 cases with macula-off retinal detachment compared three groups of patients operated between 1 and 2 days, 3 and 4 days, and 5 and 7 days after macular detachment, with a mean follow-up of 10.5 months, but no statistical difference in visual recovery between groups was found (Ross et al. 2005). Using OCT more detailed information has recently become available showing that an increase in duration of the macula-off retinal detachment was significantly associated with reduced postoperative restoration of the IS/OS and the external limiting membrane (ELM). Some preoperative variables (intraretinal separation and outer layer undulation) were not significantly associated with duration of the macular detachment but with the height of the detached macula (Joe et al. 2013).
21.4 Preoperative Optical Coherence Tomography Examination of Retinal Detachment
Very recently an experimental intraoperative OCT device has been investigated, which allows to obtain intraoperative OCT images (Binder et al. 2011). This novel technique could be potentially useful in the intraoperative evaluation of the detached macula in case of vitreous hemorrhage or other vitreous opacities which preclude a detailed preoperative evaluation of the detached macula. Intraoperative OCT could also help in the differentiation between a large macular cyst and a macular hole in the detached macula, which would directly influence the surgical management (Ehlers et al. 2013).
21.5 Postoperative Optical Coherence Tomography Examination of Retinal Detachment
21.5.1 Surgical Technique Influencing Postoperative Retinal Anatomy on Optical Coherence Tomography
The choice for the use of a specific surgical technique for retinal detachments is in general dictated by the type and severity of the retinal detachment to ensure optimal anatomical and functional outcome. It has thus come with some surprise that a recent report using OCT has found that the incidence of postoperative residual subretinal fluid affecting the macular region varies after different surgical techniques. Residual fluid accumulation is significantly higher after scleral buckling with a residual macular detachment occurring in 63 % after transscleral surgery and only in 13 % after vitrectomy (Kambara et al. 2000). Looking at the long-term evolution of this fluid, it was shown that there is an incidence of subretinal fluid in 69 % at 1 month, 50 % at 3 months, and 13 % at 12 months follow-up (Wolfensberger and Gonvers 2002) (Fig. 21.2). However, when looking at patients who had been operated on using vitrectomy, cryotherapy, and fluid-gas exchange, no postoperative persistent subretinal fluid as evaluated by OCT at 1 month after surgery was observed (Wolfensberger 2004). The order of this relationship was also confirmed in two larger studies using both pars plana vitrectomy (Benson et al. 2006) and episcleral buckle surgery (Benson et al. 2007) whereby the subfoveal fluid accumulation occurred in 15 % after vitrectomy and in 55 % after buckle surgery at 6 weeks follow-up. In the most recent study on the subject, postoperative subretinal fluid was noted in 86 % after scleral buckling versus 33 % after vitrectomy at 3 months postoperatively (Matsui et al. 2013). This difference is very likely to be explained by the fact that during vitrectomy, the subretinal space is inadvertently washed out by the continuous flow through the infusion line if the retinal breaks are of sufficient size. Simple transscleral drainage of subretinal fluid will always leave a narrow slither of potentially viscous subretinal fluid, which will take a long time to resolve (Veckeneer et al. 2012).
Fig. 21.2
Postoperative images of retinal detachment. (a) SD-OCT showing persistent single subretinal foveal bleb at 6 months in a patient successfully treated for a retinal detachment with pars plana vitrectomy. (b) SD-OCT showing persistent multiple subretinal foveal blebs at 3 months in a patient successfully treated for a retinal detachment with vitrectomy. (c) SD-OCT showing persistent flat subretinal fluid at 3 months in a patient successfully treated for a retinal detachment with vitrectomy
21.5.2 Postoperative Factors
It has been known for many decades that several gross macular abnormalities, such as cystoid macular edema, epiretinal membrane formation, retinal folds, and pigment migration, can occur after successful surgery for retinal. In some cases, no clinically detected macular changes are however observed, and the reduced postoperative VA remained unexplained. With the advent of OCT, many of these cases could be related to clinically silent modification of macular area, which are described below.
21.5.2.1 Cystoid Macular Edema
Although cystoid macular edema appeared historically to be a frequent postoperative macular complication, which was correlated with partial visual recovery after retinal surgery (Sabates et al. 1989), it disappears spontaneously in the majority of cases (Bonnet et al. 1983). More recent OCT-guided investigations have not confirmed an important role of classic cystoid macular edema in the postoperative phase after retinal detachment (Wolfensberger and Gonvers 2002).
21.5.2.2 Retention of Subretinal Fluid
Subretinal fluid retention after macula-off retinal detachment can occur in two different types of pattern. The most common appearance is a small subfoveal bleb, which has been reported by several authors using postoperative OCT examination. It appears that prolonged fluid retention for more than 3 months after retinal detachment surgery may be one of the causes of delayed restoration of visual acuity (Hagimura et al. 2002; Wolfensberger and Gonvers 2002; Lecleire-Collet et al. 2005; Matsui et al. 2013). On the other hand, other authors have indicated that subretinal fluid finally resolved at 1 year without influencing final visual acuity in 44 eyes after successful scleral buckling for acute macula-off rhegmatogenous retinal detachment (Soe et al. 2008; Delome et al 2012). These fluid blebs may also appear in multiple clusters, which have been linked to intraoperative reattachment of the retina (Kim et al. 2004).
The less common pattern of subretinal fluid accumulation is a diffuse layer of fluid under the macula, which is usually linked to highly myopic eyes in young patients with long-standing asymptomatic inferior retinal detachment (Abouzeid et al. 2009). This fluid may linger for many months despite intraoperative transscleral drainage during buckle surgery (Fig. 21.3). Looking at the long-term evolution of this fluid, it was shown that there is an incidence of diffuse accumulation in 12 % at 1 month, 6 % at 3 months, and total disappearance at 12 months follow-up (Wolfensberger and Gonvers 2002).
Fig. 21.3
Retinal detachment treated with buckle surgery and external fluid drainage. (a) SD-OCT of a young patient, 1 month after inferior retinal detachment treated with buckle surgery and external fluid drainage, shows a diffuse shallow elevation of the retina. (b) SD-OCT shows final complete reattachment of the fovea at 17 months after surgery; the attachment occurred between 6 and 9 months after surgery (Reproduced from Abouzeid et al. (2009), with permission of Acta Scandinavica)
21.5.2.3 Postoperative Foveal Thickness
Decreased postoperative foveal thickness as measured with OCT has been implicated as a factor for reduced visual acuity recovery in a study following patients with both macula-on and macula-off retinal detachments. However, the correlation between the reduced postoperative ONL thickness and postoperative best-corrected visual acuity was lower in the macula-off group suggesting that the visual acuity is primarily related to the preoperative state of the macula which leads to a higher chance of cone cell loss and subsequent ONL thickness decrease (Gharbiya et al. 2012). A direct analysis of the central foveal thickness failed to demonstrate a correlation with visual acuity outcome in successfully repaired retinal detachments (Wakabayashi et al. 2009).
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