The relationship between laser speckle flowgraphy-measured optic disc microcirculation and postoperative visual recovery in rhegmatogenous retinal detachment.

Abstract

The effects of rhegmatogenous retinal detachment (RRD) on ocular circulation are not well understood. In particular, information is lacking on the perioperative time–course of retinal blood flow changes, the risk of retinal ischaemia, and consequent adverse effects on retinal and visual function ( Rosenbaum et al. 1997). Here, we used laser speckle flowgraphy (LSFG), a non-invasive technology that measures mean blur rate (MBR) and a number of derived parameters, to evaluate the hemodynamics of eyes with unilateral macula-off RRD. We then determined the relationship between visual recovery and tissue blood flow in the optic nerve head (ONH). Previously, LSFG was used to clinically evaluate ocular haemodynamics in glaucoma (Aizawa et al. 2013, 2014). This study included 33 eyes of 33 patients with clinically detectable macula-off RRD who underwent successful surgical treatment. Patients with any history of retinal surgical procedures or intravitreal drug use, ocular inflammation, lens nucleus grade 2 or higher by the Emery–Little classification, or vitreoretinal or optic nerve diseases were excluded. Before surgery, we measured the affected/fellow eye tissue MBR ratio in the ONH overall and in each quadrant: superior, temporal, inferior and nasal. We measured best-corrected visual acuity (BCVA) with the Landolt C visual acuity chart, and converted the decimal acuities to logarithm of the minimal angle of resolution (logMAR) units. Finally, we analysed the relationship between the preoperative MBR ratio, overall and in each quadrant, and 1-month postoperative visual recovery. We found that visual recovery was significantly correlated with the tissue MBR ratio in the nasal quadrant of the ONH (Table 1; r = 0.54, p < 0.01), but not with age, preoperative refractive error, preoperative visual acuity, or with the tissue MBR ratio in any other quadrant of the ONH or the ONH overall. Furthermore, although there were no significant differences between the patients in preoperative clinical findings, including age, sex, refractive error, or visual acuity (p = 0.27, p = 0.47, p = 0.38, and p = 0.46, respectively), nor in surgical procedure (p = 0.76), the tissue MBR ratio in the nasal ONH was significantly higher in the eyes with visual recovery ≥0.8 logMAR units (110.7 ± 14.9%) than in the eyes with visual recovery <0.8 logMAR units (93.8 ± 15.7%) (p = 0.03). A previous LSFG study of eyes with macula-on RRD found that ONH tissue MBR was not significantly lower in eyes with focal RRD than in healthy fellow eyes (Nagahara et al. 2000). On the other hand, a later study reported a temporary reduction in retinal tissue blood flow in the macula of eyes with macula-on RRD (Eshita et al. 2004). Our study adds detail to these previous findings by showing that in eyes with macula-off RRD, ONH circulation, especially in the nasal area, is correlated with visual improvement after surgery. Although the importance of nasal ONH circulation in central visual function remains unclear, the relative preservation of nasal ONH circulation has been observed in ocular disorders besides RRD, including glaucoma (Aizawa et al. 2014). The nasal ONH may therefore be a relatively stable region of ocular circulation. This suggests that decreased nasal ONH circulation, such as observed here in the eyes with poor visual recovery, might be an indicator of relatively severe RRD-induced ischaemia in the retinal capillaries, which can permanently impair central visual function. Our observation of decreased nasal ONH circulation may also have been related to the LSFG device losing focus in the areas of retinal detachment. While this would reduce the accuracy of the measurements, the nasal ONH would be relatively less affected, due to its location in the retina being far from the macular detachment. Therefore, our results suggest that the tissue MBR ratio in the nasal ONH, determined non-invasively and objectively with LSFG, could serve as a biomarker of positive postoperative visual outcomes in eyes with macula-off RRD.