Preoperative laser flare values do not predict proliferative vitreoretinopathy in patients with RRD
The measurements of preoperative laser flare are not reliable in discriminating those patients with rhegmatogenous retinal detachment (RRD) at high and low risk of acquiring postoperative proliferative vitreoretinopathy (PVR), a recent study has found.
“[T]he wide variation and overlap in flare values between patients with and without PVR implicate that the measurement of aqueous humour flare with a Kowa Laser Flare Meter is inaccurate in discriminating between those patients with RRD at high and low risk of developing PVR.
Data from two independent prospective studies (centre 1: n=120; centre 2: n=194) were combined to validate the use of preoperative flare values as a predictor of PVR risk, as well as to confirm the sensitivity and specificity of this method for identifying high-risk patients.
PVR was defined as redetachment due to the formation of traction membranes that required reoperation within 6 months of initial surgery. Logistic regression and receiver operating characteristic analysis were performed to determine whether higher preoperative flare values correlated with an elevated risk of postoperative PVR.
Of the 314 patients included in the study, 21 (6.7 percent) developed PVR redetachment. Since median flare values significantly differed between centres, analyses were done separately. [Br J Ophthalmol 2017;101:1285-1289]
Based on logistic regression analysis, only centre 2 demonstrated a small but statistically significant increase in odds of PVR redetachment with increasing flare (odds ratio, 1.014; p=0.005).
Areas under the receiver operating characteristic showed low sensitivity and specificity (centre 1: 0.634; 95 percent CI, 0.440 to 0.829; centre 2: 0.731; 0.598 to 0.865).
“The results of our study suggest that preoperative flare values are a poor predictor of postoperative PVR development,” researchers said. “Although the logistic regression analysis showed a significant result for one of the two centres, this did not improve classification of patients into their respective groups (PVR vs no PVR development).”
“In addition, the sensitivity and specificity of preoperative flare at different cutoff values were too low to adequately filter out the high-risk patients. As a consequence, we were unable to validate the findings of Schroder [and colleagues], although they used the same flare meter type and calibration protocol,” they added. [Retina 2012;32:38–42]
The investigators found discrepancies between the two centres during the analysis of the data. One such discrepancy was a statistically significant difference in median flare values. Patients with no PVR in centre 1 (17.7 pc/ms) had a higher median value than those in centre 2 (10.2 pc/ms). In addition, healthy fellow eyes had significantly higher median flare values.
“A comparison of the values with those of previous studies using flare measurement suggests that centre 1 is the one whose values are higher,” researchers said. [Retina 2012;32:38–42; Graefes Arch Clin Exp Ophthalmol 2010;248:957–62; Am J Ophthalmol 2001;132:343–7; Br J Ophthalmol 1991;75:348–52]
“Previously reported mean values range from 3.7 to 6.5 pc/ms in healthy individuals and a median of 10 pc/ms in patients with RRD. We therefore decided to analyse the results separately for each centre,” researchers noted.
Whether the addition of aqueous flare as a parameter to existing risk formulae would enhance their predictive value should be further investigated, according to researchers.
RRD is a common eye condition whose prevalence increases with age. Surgical repair is effective in majority of cases, but in 5 to 10 percent of patients, reattachment is complicated by the formation of epiretinal or subretinal contracting membranes. This complication is known as PVR, which often results in recurrent detachments and a poor prognosis in terms of regaining vision. [Surv Ophthalmol 1998;43:3–18]