Abstract
purpose. To evaluate a semiautomated image analysis software package, Retinal Image multiScale Analysis (RISA), for the diagnosis of plus disease in preterm infants with retinopathy of prematurity (ROP).
methods. Digital images of the posterior pole showing both disc and macula in preterm infants with ROP were analyzed with an enhanced version of RISA. Venules (N = 106) and arterioles (N = 44) were identified, and integrated curvature, diameter, and tortuosity of the vessels were calculated. After the RISA calculations were completed, the origins of the vessels were determined to be 32 eyes in 16 infants (12 eyes with plus disease, 20 with no plus disease, as diagnosed by ophthalmic examination). Vessels were sorted into two groups—plus disease and no plus disease—and each RISA parameter was compared using the Mann-Whitney test. For each parameter, sensitivity and specificity were plotted as a function of cutoff criterion, receiver operating characteristic (ROC) curves were constructed, and the areas under the curve (AUC) were calculated.
results. For both arterioles and venules, each of the three parameters was significantly larger for the plus disease group. For instance, the median estimated arteriolar and venular diameters were approximately 12 μm greater in plus disease. Sensitivity and specificity plots indicated good accuracy of each parameter for the diagnosis of plus disease. The AUC showed that curvature had the highest diagnostic accuracy (0.911 for arterioles, 0.824 for venules).
conclusions. The strong performance of RISA parameters in this sample suggests that RISA may be useful for diagnosing plus disease in preterm infants with ROP.
The hallmark of retinopathy of prematurity (ROP) is abnormal retinal vasculature.
1 Ophthalmologists diagnose and make decisions about the initial treatment of ROP based on the appearance of the retinal blood vessels. Dilatation and tortuosity of the retinal vessels at the posterior pole in two or more quadrants,
2 termed plus disease, emerged as a sign of high-risk prethreshold ROP that benefits from early laser ablation of the peripheral avascular retina.
2 Detection of plus disease, specifically venous congestion and arteriolar tortuosity,
3 depends on the ophthalmologist’s subjective assessment. In the Early Treatment for Retinopathy of Prematurity (ETROP) study, the ophthalmologists compared their view of the retinal vessels to those in a standard fundus photograph of plus disease.
2
Objective measurement of tortuosity and dilatation has been recognized as an important goal for the unbiased diagnosis of plus disease.
4 5 To this end, investigators have applied image analysis techniques.
6 7 Measurement of tortuosity appears to have promise as an indicator of plus disease.
6 Vessel diameter may also be considered an indicator of plus disease, and its measurement in the preterm fundus is feasible.
5 7 Swanson et al.
7 pioneered the use of a semiautomated software program, Retinal Image multiScale Analysis (RISA),
8 9 10 for assessment of the retinal vessels in ROP. We used an enhanced version of RISA to investigate diameter, tortuosity and, in addition, integrated curvature
11 of posterior retinal vessels in preterm infants with ROP. The prior version of RISA was insensitive to the frequency at which a vessel bows.
7 We added the curvature parameter to address this limitation. In this study, our purpose was to evaluate the enhanced version of RISA for the diagnosis of plus disease.