Karen A. Karp

A Clinical Prediction Model to Stratify Retinopathy of Prematurity Risk Using Postnatal Weight Gain

OBJECTIVE: To develop an efficient clinical prediction model that includes postnatal weight gain to identify infants at risk of developing severe retinopathy of prematurity (ROP). Under current birth weight (BW) and gestational age (GA) screening criteria, <5% of infants examined in countries with advanced neonatal care require treatment. PATIENTS AND METHODS: This study was a secondary analysis of prospective data from the Premature Infants in Need of Transfusion Study, which enrolled 451 infants with a BW < 1000 g at 10 centers. There were 367 infants who remained after excluding deaths (82) and missing weights (2). Multivariate logistic regression was used to predict severe ROP (stage 3 or treatment). RESULTS: Median BW was 800 g (445–995). There were 67 (18.3%) infants who had severe ROP. The model included GA, BW, and daily weight gain rate. Run weekly, an alarm that indicated need for eye examinations occurred when the predicted probability of severe ROP was >0.085. This identified 66 of 67 severe ROP infants (sensitivity of 99% [95% confidence interval: 94%–100%]), and all 33 infants requiring treatment. Median alarm-to-outcome time was 10.8 weeks (range: 1.9–17.6). There were 110 (30%) infants who had no alarm. Nomograms were developed to determine risk of severe ROP by BW, GA, and postnatal weight gain. CONCLUSION: In a high-risk cohort, a BW-GA-weight-gain model could have reduced the need for examinations by 30%, while still identifying all infants requiring laser surgery. Additional studies are required to determine whether including larger-BW, lower-risk infants would reduce examinations further and to validate the prediction model and nomograms before clinical use.

Semiautomated digital image analysis of posterior pole vessels in retinopathy of prematurity

Plus disease is a major indicator for treatment in retinopathy of prematurity (ROP), and computer-assisted image analysis of vessel caliber and tortuosity in the posterior pole may indicate disease progression and severity. We sought to determine whether semiautomated digital analysis of posterior pole vessels using narrow field images with varying severity of ROP correlated with vessel width and tortuosity.

The Rate of Retinal Vessel Dilation in Severe Retinopathy of Prematurity Requiring Treatment

PURPOSE To assess whether the rate of change of retinal vessel diameter can help identify infants at the highest risk for severe retinopathy of prematurity (ROP). DESIGN Thirty-five infants at risk for ROP were included in this prospective, longitudinal study. METHODS Images were obtained using the NIDEK NM200D noncontact camera (NIDEK Inc, Aichi, Japan) at the time of ROP examinations in the intensive care unit. Vessel diameters were measured from digital fundus photographs of right eyes in a masked fashion using VesselMap image analysis software (IM-EDOS GmbH, Weimar, Germany). The rate of change of vessel diameter was calculated based on the linear regression slope and was compared between eyes in which type 1 ROP requiring treatment developed and in controls without ROP or with ROP less severe than type 1. RESULTS Multivariate analysis showed that the group of eyes in which type 1 ROP developed had a greater increase in diameter over time in the inferior temporal veins (P = .01), superior temporal veins (P < .0001), mean temporal veins (P < .0001), superior temporal arteries (P = .02), and mean temporal arteries (P = .004). The area under receiver operator characteristic curve for venous diameter change was 0.96 for the superior temporal vein, 0.86 for the inferior temporal vein, and 0.96 for the mean temporal vein. CONCLUSIONS On average, the rate of retinal vessel change was greater in eyes with type 1 ROP requiring treatment than in control eyes. The rate of venous diameter change had the best discriminative ability to differentiate between the 2 groups.

Risk Stratification of Preplus Retinopathy of Prematurity by Semiautomated Analysis of Digital Images

OBJECTIVE To determine whether quantitative analysis of retinal vessel width and tortuosity from digital images discriminates which eyes with preplus retinopathy of prematurity (ROP) progress to treatment severity. METHODS Posterior pole images of eyes at first clinical diagnosis of preplus ROP were obtained using a 30 degrees-field, noncontact fundus camera. Width and tortuosity of retinal vessels were analyzed from digital images using computer-assisted image analysis software. Mean width and tortuosity of venules and arterioles were compared in 19 preplus eyes that regressed spontaneously and 11 preplus eyes that progressed to treatment severity. Receiver operating characteristic curve analysis was performed to assess whether width and tortuosity discriminated between groups. RESULTS Mean widths of venules alone, arterioles alone, and the 3 widest vessels were higher in preplus progressed eyes (P < .04). Mean tortuosity of the 3 most tortuous vessels was higher in preplus progressed than in preplus regressed eyes (P = .01). Most vessel width and tortuosity variables predicted which eyes with preplus progressed to treatment moderately well, with an area under the receiver operating characteristic curve of 0.72 to 0.82. CONCLUSIONS Digital image analysis of retinal vessel width and tortuosity may be useful in predicting which preplus ROP eyes will require treatment. Because vascular abnormalities are a continuum and clinical diagnosis is subjective, quantitative analysis may improve risk stratification for ROP.

Interactive Retinal Vessel Extraction by Integrating Vessel Tracing and Graph Search

Despite recent advances, automatic blood vessel extraction from low quality retina images remains difficult. We propose an interactive approach that enables a user to efficiently obtain near perfect vessel segmentation with a few mouse clicks. Given two seed points, the approach seeks an optimal path between them by minimizing a cost function. In contrast to the Live-Vessel approach, the graph in our approach is based on the curve fragments generated with vessel tracing instead of individual pixels. This enables our approach to overcome the shortcut problem in extracting tortuous vessels and the problem of vessel interference in extracting neighboring vessels in minimal-cost path techniques, resulting in less user interaction for extracting thin and tortuous vessels from low contrast images. It also makes the approach much faster.

The rate of change in retinal vessel width and tortuosity in eyes at risk for retinopathy of prematurity

PURPOSE To describe the rate of change in retinal vessel width and tortuosity in eyes that develop treatment-requiring, or type 1, retinopathy of prematurity (ROP) versus eyes that do not develop type 1 ROP. METHODS Posterior poles of eyes of 41 infants at risk for ROP were imaged longitudinally with a 30° fundus camera. Retinal vessel width and tortuosity were measured with computer-assisted image analysis. The rate of change per day in width and tortuosity up to the development of most severe ROP was calculated from linear regression and eyes with (n = 10) and without type 1 ROP (n = 31) were compared. RESULTS Eyes that developed type 1 ROP had a greater rate of change in width for venules and 3 widest vessels (P < 0.0001), and a greater rate of change in tortuosity for arterioles and 3 most tortuous vessels (P < 0.0001) than eyes that did not develop type 1 ROP. These vessel parameters discriminate the 2 groups well (area under the ROC curve, 0.79-0.90). A combination of venular width and arteriolar tortuosity had the best discriminative ability (area under the ROC curve, 0.96). CONCLUSIONS In this pilot study, eyes that eventually developed type 1 ROP demonstrated a faster increase in width and tortuosity of retinal vessels compared with those that did not. Further study of the kinetics of retinal vascular change in a larger sample may allow for the earlier identification of vision-threatening ROP.

Image analysis of posterior pole vessels identifies type 1 retinopathy of prematurity

Identification of type 1 retinopathy of prematurity (ROP) relies heavily on the presence of characteristics of plus disease, especially tortuosity. However, a relatively infrequent subset of eyes with type 1 ROP, eyes with zone 1, stage 3 ROP without plus disease, is included in treatment indications. We examined if posterior pole vessel width is associated with type 1 ROP in a subset of eyes with zone 1, stage 3 ROP without plus disease and whether vessel width differentiates type 1 from non-type 1 ROP.

Retinal vessel changes after laser treatment for retinopathy of prematurity

BACKGROUND The clinical response to retinopathy of prematurity (ROP) treatment is currently assessed subjectively. This study aims to quantify treatment response objectively by assessing changes in digital images of posterior pole retinal vessel width and tortuosity. METHODS Images of 30 right eyes with type 1 ROP obtained at up to three time points were analyzed: before treatment (T = 0) and 1 (T = 1) and/or 2 weeks (T = 2) after treatment. Width and tortuosity of retinal vessels were analyzed from digital images using computer-assisted image analysis software. RESULTS Vessel width decreased by 20% (P < 0.004) within the first week and remained stable by the second week after laser treatment. Vessel tortuosity did not significantly change by the first week but decreased 27% (P < 0.01) by second week. CONCLUSIONS Vessel width appears to decrease dramatic within the first week, whereas the regression of tortuosity follows a slower course.