Our estimated incidence of GRT (0.094–0.114 cases per 100,000 annually) in the general U.K. population suggests that it may occur more commonly than previously thought (∼0.05 per 100,000 yearly).
4 This disparity may have occurred because previous estimates were generally derived from retrospective data from single tertiary referral centers. The design of the present study (prospective nationwide surveillance) allows the capture of most GRTs, including the more straightforward cases that would be unlikely to be referred to highly specialized hospitals, thereby giving higher incidence rates. However, there is a possibility that the incidence of GRT is even higher than that reported herein, because of incomplete ascertainment, which is a known limitation of surveillance studies.
11 Unfortunately, it was not possible to determine the exact number of cases that were unreported; similarly, it was not possible to know whether reported cases in which data were not collected were unilateral or bilateral.
GRTs are thought to be most commonly idiopathic or spontaneous. These have been estimated to represent 28% to 78% of all GRTs.
1,3,16–21 The wide range of incidence may be due, at least partly, to the definition of idiopathic GRT used in previous (and possibly outdated) studies: In some case series, idiopathic GRTs were considered to be those that were nontraumatic, whereas in others, idiopathic referred to the absence of any known predisposing factors, including high myopia and previous intraocular surgery.
1,3,16–21 If eyes with predisposing factors other than trauma (such as high myopia and previous intraocular surgery) had also been excluded, then it is likely that the incidence of true idiopathic GRT would be less than that reported in the various case series. In the present study, GRT was defined as idiopathic in the absence of any known predisposing factors, including hereditary vitreoretinopathy, myopia greater than −6 D, aphakia, complicated cataract surgery, and trauma. According to this definition, the incidence of idiopathic GRT was 54.8%.
The most common predisposing factors for the development of a GRT in the present study were trauma (16.1%), hereditary vitreoretinopathies (14.5%), and high myopia (9.7%). In other published series, the GRTs were attributed to trauma in 9% to 43%, inherited vitreoretinopathies (such as Stickler syndrome) in 1% to 8%, and high myopia in 12% to 47%.
1,3,5,16–34 Apart from two prospective multicenter studies, these statistics come mostly from single center, hospital-based, retrospective studies with relatively small sample sizes and thus have inherent weaknesses, including selection bias. The Perfluoron Study Group and Vitreon Collaborative Study Group were both prospective, noncomparative, observational, multicenter series with large sample sizes, but cases were selected to fulfill the inclusion criteria and therefore the studies cannot be considered suitable to provide epidemiologic data.
28,29 Whereas the incidence in the present study of traumatic GRT was lower than that generally found in the literature, that of GRT from hereditary vitreoretinopathies was higher than expected. A possible explanation of this is that some of the highly myopic eyes in previously reported series had concurrent undiagnosed inherited vitreoretinopathies. Another possibility may be that these cases could have been referred to highly specialized centers and were therefore missed by the retrospective evaluation. GRTs have been described after both routine and complicated ocular surgery, including vitrectomy and refractive surgery.
35–40 Such incidences occurred rarely in the present study, with only two (3.2%) cases reported intraoperatively during vitrectomy. No eyes in thus study were described to have other rarer conditions associated with GRT, such as aniridia, lens coloboma, retinitis pigmentosa, and acute retinal necrosis.
41–47
Overall, the mean age of 42.2 years and predominantly male preponderance (71.7%) were both consistent with data in previous reports.
3,16,25,28,30,31 The proportion of eyes presenting with a BCVA of 20/40 or better was 40.3%, within the 0% to 50% range observed in other published studies.
20,21,24,27,28,30,34,48–50 However, only 16.2% presented with BCVA worse than 20/200, and this was better than the 33% to 91% described in other studies.
19,24,27–30 These relatively good levels of presenting vision may be considered a reflection of the comparatively low number of fovea-off detachments (45.2%), greater than 180° GRT (12.9%), and PVR grade C (PVR-C) or greater (11.3%) in the present study. In contrast, other publications have reported fovea-off RDs in 31% to 94%, GRT greater than 180° in 6% to 62%, and severe PVR in 9% to 62%.
16–19,21,23,24,26–28,30,51
Although a small randomized clinical trial for GRT with PVR-C or greater found no difference in the 5-year anatomic reattachment, visual outcomes, and complications between postoperative tamponade with silicone oil or long-acting perfluoropropane (C
3F
8) gas,
52 silicone oil is still the tamponade of choice in most centers across the world, including the United Kingdom.
17–19,22,25–27,33,34,53,54 This preference is reflected in the present study, where silicone oil was found to have been used in 75.8% of cases, even though only 11.3% presented with PVR-C or worse.
In the present study, the retinal reattachment rate for GRT without PVR was 82.1% after the primary procedure, with final reattachment of 94.9% at last follow-up; for GRT with PVR, these rates were 72.2% and 94.4%, respectively. These percentages are similar to the published rates in the literature of 68% to 91% reattachment after one procedure and 94% to 100% at the last visit for GRT without PVR
16,20,48–50,54 and 70% to 90% reattachment after the first operation and 74% to 97% at the final visit for GRT with PVR.
33,34,52,53,55,56 These results are also comparable to the 82.0% (95% CI, 77.9–85.7) retinal reattachment rate after primary surgery by retinal specialists in the 1997 U.K. national audit of primary surgery for rhegmatogenous RD.
9 With regard to visual acuity, GRT without PVR achieved final BCVA of 20/40 or better in 46.2% and worse than 20/200 in 17.9%; for GRT with PVR, these BVCAs were achieved in 33.3% and 27.8%, respectively. This result was comparable to the BCVA outcomes of previously published series: 20/40 or better in 18% to 50% and worse than 20/200 in 0% to 6% for GRT without PVR
16,20,48–50,54 and 20/40 or better in 10% to 64% and worse than 20/200 in 20% to 58% for GRT with PVR.
33,34,52,53,55,56 As with other characteristics of GRT discussed herein, it is not possible to draw comparisons between previous case series and the current data due to methodological differences among studies. It must also be pointed out that the better reported outcomes quoted were generally drawn from smaller case series with sample sizes of fewer than 30 cases. Data from the six largest case series on GRT (which include two prospective multicenter studies from the Vitreon Collaborative Study Group and Perfluoron Study Group respectively and four retrospective single hospital case series) are summarized in
Table 5.
The fellow eye of patients with nontraumatic GRTs is at an increased risk of GRT and RD. In a large series of 228 fellow eyes of nontraumatic GRTs in a study by Freeman,
4 the 124 eyes that did not receive prophylactic treatment had an 11.3% incidence of GRT over a mean follow-up of 3.7 years.
4,57 Furthermore, RDs not associated with GRT may occur in up to 36% of fellow eyes.
1,4,5,57 It should be noted that in the present study, among the nontraumatic and noniatrogenic cases at presentation, 12.0% were fellow eyes of patients who had a history of GRT, compared with 6.6% in the Freeman
4 series. In addition, present or previous RD, retinal breaks (other than GRT), or retinal changes predisposing toward the development of RD were observed in 26.0% of fellow eyes of nontraumatic and noniatrogenic GRT. Although somewhat lower than the 31% to 81% reported in the literature,
1,3,4,16,18,31,57 the rate still represents a high proportion of fellow eyes at risk of visual loss due to RD. Various prophylactic methods have therefore been proposed to prevent or limit the occurrence of GRT and/or RD in fellow eyes, including 360° encircling scleral buckle, cryotherapy, or laser photocoagulation.
4,5,18,31,34,57–62 There is no strong evidence, however, to support or refute the value of these procedures in preventing a GRT, and they are not without possible adverse effects.
63 Furthermore, it is not certain which method is most effective.
63 In the present study, none of the 19 eyes that received prophylactic treatment (whether 360° or local) developed a GRT or an RD throughout the follow-up, whereas 1 (1.6%) of the untreated fellow eyes developed a GRT 3 months after presentation. Caution should be taken, however, when interpreting these results due to the relatively short follow-up and the fact that the status of the vitreous of the fellow eye was not recorded.
1,4,57,62,64–66
Presented in part at the XXVIth Meeting of the Club Jules Gonin, St. Moritz, Switzerland, September 2008.
Supported by the WH Ross Foundation for the Prevention of Blindness (Scotland), Dollar, Scotland, UK.
The authors thank the British Ophthalmological Surveillance Unit (BOSU) for support in the study, and Barny Foot, research coordinator for the BOSU, for help and advice. The following ophthalmologists assisted us with the data collection for the study: Alan J. S. Ang, George W. Aylward, James W. Bainbridge, Richard Bates, Richard M. Best, Ted Burton, Andrew B. Callear, Steve J. Charles, David G. Charteris, David G. Cottrell, Charles J. M. Diaper, Andrew Dick, Subramaniam Dinakaran, Adriana Agius-Fernandez, Alan W. Fitt, Richard R. Goble, Robert Gray, Zdenek Gregor, Harold M. Hammer, Edward Herbert, Robert J. Hill, David V. Inglesby, Charles R. H. James, Robert Johnston, Niral Karia, Joseph Keenan, James N. P. Kirkpatrick, Andrew Luff, Robert MacLaren, Ian Marsh, Paul J. McCormack, Quresh Mohamed, Douglas Newman, Richard Newson, Philippa M. Pennefather, William Pollock, Anna Poulsen, Som Prasad, Nicholas J. Price, Sal Rassam, Robert A. H. Scott, Richard Sheard, Jas Singh, Kenneth P. Stannard, Paul M. Sullivan, Gillian C. Vafidis, Ian F. Whyte, Roger S. Wilson, David Yorston, and Hadi J. Zambarakji.