however , studies have shown that surgery is best done during normal working hours . given the pressures on theatre use
it is important to be able to assess the retinal detachment and to ascertain the urgency of planning surgical intervention .
one of the most important features is the involvement of the macula and fovea that is macula on or macula off . in cases of macula - off retinal detachments ,
macula - on retinal detachments , however , should have their surgery expedited , the main concern being the conversion to a macula - off situation which has a much poorer visual prognosis .
the assessment of rhegmatogenous retinal detachments is multifactorial ; in an otherwise normal eye visual acuity is an easy measure of macula involvement with the 6/60 patient being macula off and 6/6 macula on .
similarly the onset of symptoms and the age of the retinal detachment is important , as chronic detachments can be more stable and surgery can be safely delayed .
also the extent of detachment and position of the retinal break can also help predict the progression of an acute macula on retinal detachment .
however , in certain situations the macula - on or macula - off question is not easily answered ; visual acuities may be misleading ; examination of the detachment may be difficult due to poor views often due to vitreous hemorrhage and chronicity may be difficult to ascertain in patients with vague histories .
high - speed spectral domain optical coherence tomography ( oct ) offers a noninvasive tool to evaluate retinal microstructural changes in a number of eye pathologies .
newer systems using spectral domain calculations have improved data acquisition speeds compared with conventional time - domain oct equipment allowing much greater axial resolution .
given the greater resolution a number of characteristic changes seen in retinal detachment have been observed . in this paper , we discuss two cases where spectral domain oct and an understanding of the histological changes have enabled a clearer diagnosis and planning of treatment .
our first case is a seventy - five - year - old gentleman who presented with a vague history of blurred vision for six weeks .
visual acuity was 6/24 and examination revealed a pseudophakic inferotemporal macula - off retinal detachment .
the reduction in visual acuity was thought to be secondary to vitreous haemorrhage as biomicroscopy assessment showed the detachment stopping inferior to the macula ( figure 1 ) . to confirm the macula status ,
contrary to the biomicroscopy examination ( figure 1 ) , this revealed a macula - off retinal detachment ( figure 2 ) .
changes seen in the oct scan were characteristic of an old retinal detachment with the presence of intraretinal cysts , undulation of outer retinal layers , and the hyper - reflectivity in the photoreceptor layer ( figure 2 ) .
secondary to these oct findings , the surgical session was deprioritised and performed five days later .
the surgical repair consisted of a three - port pars plana vitrectomy with perfluoropropane tamponade and cryotherapy .
subsequent spectralis oct one year following the retinal detachment shows restoration of normal retinal morphology with resolution of the intraretinal cysts , flattening of the retinal layers , and no hyperreflectivity seen ( figure 3 ) .
our next case was a fifty - year - old myopic female who presented on a friday with a several - month history of floaters and visual distortion described as 
microstructural analysis of the macula was performed using a heidelberg spectralis oct scan which confirmed a macula - off retinal detachment ; however , the oct scan revealed that the fovea was bisected by this detachment ( figure 4 ) .
moreover , the macula microstructure seen in the oct scan showed no retinal folds or hyperreflectivity present near the fovea .
indeed , the only morphological retinal detachment changes observed which indicated any chronicity were small intraretinal cysts present peripherally away from the fovea ( figure 4 ) .
given the oct findings , she was treated as a macula - on retinal detachment patient , and surgery was expedited such that an emergency theatre session was organised within 24 hours on a saturday morning .
the surgical repair was a three - port pars plana vitrectomy using a sulphur hexaflouride tamponade and cryotherapy .
after subsequent cataract surgery , vision had returned to 6/6 with normal oct findings ( scan not shown ) .
the morphological changes seen in retinal detachment have previously been evaluated by oct and are becoming clearer with newer systems using spectral domain calculations , which have improved data acquisition speeds to ~40  000 a - scans per second allowing much greater axial resolution to approximately 3.5  m tissue resolution .
the transformations seen in retinal detachment include intraretinal cyst formation , intraretinal separation , and undulation of outer retinal layers [ 3 , 4 ] .
the disruption of the photoreceptor inner and outer segment junction in macula - off rhegmatogenous retinal detachments is also seen both preoperatively   and postoperatively [ 6 , 7 ] .
murine models comparing histology and oct confirm these findings and also highlight the hyperreflectivity in the photoreceptor layer which may represent a cellular immune infiltration or misalignment of the photoreceptor layer .
these changes were all seen in our first case ( figure 2 ) proving that the retinal detachment had been present for a period of time prior to arrival in our unit and enabling appropriate de - prioritisation within a busy vitreoretinal service . in our second case ,
in which the fovea was bisected by a retinal detachment , time of onset was in some doubt .
retinal thickness of the detached retina has been shown to be time dependent initially thickening then thinning with time [ 8 , 9 ] ; however the subfovea thickness was normal when scanned suggesting a recent event along with the absence of any intraretinal cysts , retinal undulations , and hyper reflectivity of the photoreceptor layer ( figure 4 ) .
onset of retinal detachment is of importance , as experimental retinal detachments in cats have shown that although alterations in the outer nuclear layer occur after 1 hour , progressive loss of photoreceptors continues up to 1330 days , with limited atrophy in cat retinas detached 3 to 7 days .
however , patients that have no tomographic structural changes presumably due to recent foveal involvement have better clinical prognosis .
this is most likely secondary to less atrophy and death of the photoreceptors which has histopathologically been shown to be present in prolonged detachment of the retina [ 1014 ] . finally , the height of retinal detachment , which appears to affect the formation of multiple cystic cavities in the detached inner and outer neuronal layers , correlates with poor visual outcome [ 15 , 16 ] .
all of these features when taken into account suggested a good prognostic outcome for our second patient and hence prompt surgery resulting in an excellent visual recovery ; an outcome that could have been considerably poorer if surgery had been delayed and fovea atrophy had occurred .
the morphological changes in retinal detachment seen in oct scans give prognostic factors pertaining to visual outcome and thus help anticipate surgical outcomes .
this paper has shown the two scenarios where surgical prioritisation is reversed , that is , from macula on to macula off and secondly , from macula off to macula on . in our first case ,
a chronic detachment was identified by oct and allowed planning within the department for higher priority operations to take place .
conversely , the lack of subfoveal morphological changes in our second case led to the conclusion that the detachment was recent and prognosis good , thus surgery was expedited .
we suggest that if any doubt regarding the status of the macula exists , a routine noninvasive oct should be performed to help clarify the situation prior to surgery .
 regmatogenous retinal detachments need prompt intervention particularly when macula is on . 
 unfortunately this is not always easy to ascertain clinically and the chronicity of the event is often muddled in patient 's histories . 
 developments in optical coherence tomography ( oct ) have allowed high - resolution axial scans which have enabled the characterisation of retinal changes in retinal detachments . in this paper 
 , we show the changes in retinal morphology observed by spectral domain oct and how this can be used to plan appropriate surgical intervention . 