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. 2026 Feb 28;6(5):101139. doi: 10.1016/j.xops.2026.101139

Retinal Blood Flow Decreases After Treatment with Laser Photocoagulation for Retinopathy of Prematurity

Shaiza Mansoor 1, Christina Kilby 2, Joyce Wang 1, Jeong-Yoon Wu 2, He Eun Forbes 2, Jason Zhou 1, Ria Kapoor 2, Urjita Das 2, Sarah Ward 2, Hansine Vexlund 2, Kristin Williams 2, Moran Roni Levin 2, Sripriya Sundararajan 3, Larry Magder 4, Avigyan Sinha 5, Abhishek Rege 5, Janet Leath Alexander 2,∗
PMCID: PMC13099490  PMID: 42027468

Abstract

Purpose

To compare total retinal blood flow (TRBF) rates before and after retinopathy of prematurity (ROP) treatment with laser photocoagulation using laser speckle contrast imaging (LSCI).

Design

Prospective cohort study.

Participants

Fourteen eyes from 8 premature infants in the neonatal intensive care unit receiving laser photocoagulation treatment for ROP.

Methods

Total retinal blood flow was measured using LSCI longitudinally before and after laser treatment. Subject characteristics and clinical ROP features were included in regression analysis using generalized estimating equations to account for 2 eyes per subject and longitudinal measures over time.

Main Outcome Measures

The main outcome measure was peak TRBF.

Results

Prior to ROP treatment with laser photocoagulation, subjects had a peak TRBF of 8.8 ± 2.1 a.u. compared to 7.3 ± 1.4 a.u. after treatment (mean difference = 1.5 a.u., P = 0.04). Quadrant-specific blood flow analysis found that the nasal quadrant demonstrated the most significant blood flow reduction after laser treatment (P = 0.02), followed by the superior quadrant (P = 0.03). The inferior (P = 0.3) and temporal (P = 0.4) quadrants did not have significant blood flow reduction. Peak TRBF decreased over time after laser treatment, but the decrease was not significant (β = –0.3 a.u./week, P = 0.2).

Conclusions

We observed lower TRBF after ROP treatment with laser photocoagulation.

Financial Disclosure(s)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Keywords: Retinopathy of prematurity, Laser speckle contrast imaging, Laser photocoagulation, Anti-VEGF, Total retinal blood flow (TRBF)

Retinal vascular changes have been central to the clinical evaluation of retinopathy of prematurity (ROP) since the earliest descriptions of the disease in 1942.1 These vascular abnormalities remain a key criterion for diagnosis and treatment decisions today.2,3 While vessel caliber and tortuosity provide qualitative indicators of disease severity, technological advances have enabled quantitative assessment of vascular alterations, including measurements of dynamic blood flow. Retinal blood flow in preterm infants at risk for ROP has been quantified using color Doppler imaging, laser speckle flowgraphy, and laser speckle contrast imaging (LSCI).4, 5, 6, 7, 8 Complementary imaging technology, for example, OCT angiography, captures static vessel structure rather than dynamic flow, and correlations between architectural and hemodynamic parameters have been demonstrated.9

Laser photocoagulation has been a mainstay of ROP treatment for more than 5 decades.10, 11, 12, 13, 14, 15 However, its effects on retinal blood flow remain poorly characterized. One prior study with a relatively small sample size reported decreased retinal blood flow after laser treatment for ROP.16 Similarly, studies using color Doppler imaging and LSCI have demonstrated reductions in ocular blood flow after intravitreal anti–VEGF therapy.17, 18, 19 Together, these findings suggest that both laser and pharmacologic treatments may alter ocular perfusion, yet the underlying mechanisms and temporal dynamics of these changes remain unclear.

The purpose of this study was to assess total retinal blood flow (TRBF) using LSCI longitudinally before and after ROP treatment with laser. We hypothesized that TRBF would decrease after laser treatment. Furthermore, we hypothesized that alterations in retinal blood flow after laser photocoagulation would be quadrant-specific.

Methods

This study was conducted as part of an ongoing prospective study at the University of Maryland Neonatal Intensive Care Unit in Baltimore, Maryland. The study was approved by our accredited institutional review board (HP-00088705) in adherence with US Health Insurance Portability and Accountability Act guidelines and the Declaration of Helsinki. The study was conducted from January 2021 to December 2024.

Participants

Parents of neonates who met the criteria for ROP screening examinations were invited to participate in this study. Informed consent was obtained from the parents of each subject after explanation of the nature and possible consequences of participating in the study. Prior approval by neonatology was obtained for all enrolled subjects. Data were collected from subjects throughout the duration of their ROP screening after enrollment. Subjects analyzed included 8 infants meeting the criteria in Table 1. Analysis was restricted to data collected during the 6 weeks before and 6 weeks after treatment with laser for comparison. There was no external control group.

Table 1.

Inclusion and Exclusion Criteria

Inclusion Criteria Exclusion Criteria
  • •

    ROP screening risk factors: gestational age ≤30 weeks, or birth weight ≤1500 g

  • •

    Treatment-requiring ROP due to type 1 threshold ROP as graded by the treating physician. Specifically, (a) plus disease or stage 3 in zone I or (b) plus disease with stage 2-3 in zone II2 or (c) the presence of concerning features, namely preplus disease with thick or extensive stage 3 membranes with anteroposterior traction concerning for progression to stage 4 ROP20, 21, 22, 23, 24

  • •

    Laser provided as the sole treatment modality (no intravitreal anti-VEGF)

  • •

    Laser performed within first 50 weeks postmenstrual age
  • •

    Media opacity (i.e., cataract)

  • •

    Genetic syndrome

  • •

    Cardiac surgery

  • •

    Stroke or blood clot

  • •

    Infants older than 50 weeks postmenstrual age at the time of laser
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ROP = retinopathy of prematurity.

ROP Imaging and Examinations

One hour prior to ROP examination, infants' pupils were dilated with topical mydriatic (cyclopentolate 0.2% and phenylephrine 1%) drops. One drop of 0.5% proparacaine was placed in each eye immediately before the eye examination. Positioning was conducted as previously described.19

Laser speckle contrast imaging was performed using the investigational XyCAM CRE prototype system (Vasoptic Medical, Inc). The XyCAM CRE is a custom-modified version of the US Food and Drug Administration-cleared XyCAM RI System (Vasoptic Medical, Inc) wherein the imaging unit is mounted on a mobile articulating arm to facilitate retinal imaging in supine infants in the neonatal intensive care unit setting. Details of the imaging protocol have been previously described.19

Immediately after LSCI, a standard ROP screening exam was performed using binocular indirect ophthalmoscopy, followed by retinal photography using the RetCam Envision (Natus Medical Inc). After ophthalmoscopy and photography, the examining physician documented the zone, stage, and presence of plus disease in the electronic medical record. RetCam fundus photos were later analyzed in deidentified masked fashion to verify zone using the RetCam software caliper, stage, and plus score (p-score) using side-by-side image comparison to the standard 9-level p-score reference photo.25

Clinical Data

Clinical data were collected from documentation in the electronic medical record and also separately graded in masked fashion. Plus scores, zone, and stage were assigned based on fundus photos and compared to clinical documentation. For statistical analysis, zone I was entered as “1.0,” zone IIp was entered as “1.5,” and zone IIa was entered as “2.0.” RetCam images were used to verify all clinical documentation, and no discrepancies were noted in zoning or p-score assignment between our 2 graders (J.L.A. and M.R.L.) (κ = 1.0).

Image Analysis

The XyCAM CRE LSCI outputs a time-stack of blood flow velocity index maps of the posterior retinal vasculature. Obtained data contains a time-sequence of blood flow velocity index values at each pixel. Pseudocolor heat maps are used in real time during imaging to visualize the spatial distribution of blood flow velocity index, while time plots reveal the trends of blood flow pulsations over multiple cardiac cycles. Blood flow velocity index–related metrics within specific regions are also provided in tabular format for subsequent analysis.

Total retinal blood flow was determined at the point of care. Images were centered on the optic disc region in order to capture the entire retinal blood flow entering and exiting the eye. Image analysts were masked to the clinical status of the subject. After image registration for motion, the optic nerve head border was outlined using previously described reference standard elliptical region of interest (ROI) with semiaxis lengths 162.71 and 172.41 pixels, respectively, which fully encircled the optic nerve in 100% of the cohort.7,16,19 Use of the reference standard ROI avoids analyst subjectivity in selecting the optic nerve head border. After 6-second image acquisition, one single frame with optimal focus, centration, and no motion was selected at peak flow on the cardiac cycle tracing. The 2 adjacent dips for the peak are also selected by default for this ROI. The 2 adjacent dips are averaged to determine overall dip flow. Mean flow is also provided by default as the average of overall dip and peak flow. The mean and dip flow offer the same information as peak flow, offset by a constant. In this study, peak flow was selected as the outcome of interest to avoid bias and redundancy. Automated analysis was performed within the ROI to determine quadrant-specific blood flow, shown in Figure 1.

Figure 1.

Figure 1

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Automated generation of quadrant-based retinal blood flow in the left eye. The superior quadrant is represented in blue, temporal quadrant in white/gray, inferior quadrant in pink, and nasal quadrant in yellow. A, Color-coded quadrant mapping on the OD reference standard ellipse; B, quadrant-specific BFVi over time (seconds) throughout the cardiac cycle. The user defines the optic nerve region of interest using a reference standard ellipse, and the direction of the direct temporal peripapillary region (white asterisk ∗) based on the fundus photo overlay (defined as the point of intersection on the circumference of OD for the straight line from the center of the OD to the fovea). The software then divides the OD into 4 90-degree quadrants such that the temporal quadrant spans 45-degrees on either side of the user input for the temporal marker. BFVi = blood flow velocity index; OD = optic disc; ROI = region of interest.

Statistical Analysis

Variables evaluated included age at imaging, age at laser, gestational age, current weight, birth weight, p-score, zone, and stage. The main outcome measure was predefined as peak TRBF, based on previously published findings.19 Total retinal blood flow includes components of peak, mean, and dip over the cardiac cycle, but the mean and dip are roughly scaled measures of the peak, and therefore were regarded as redundant.

Longitudinal peak TRBF was collected from both eyes, at multiple time points, both before and after treatment. The duration of “before” and “after” was predefined at 6 weeks based on 2 factors: (1) most available data was within this time frame and (2) the biological reasoning that >6 weeks before or after laser, other factors may influence blood flow more than the laser treatment. Variables were compared before and after laser using a nonparametric test of significance (Wilcoxon test) and regression models with adjustment for inclusion of 2 eyes per subject and longitudinal measures in the same eye over time (generalized estimating equations).

Univariate analysis assessed participant demographics, characteristics, clinical features, and peak TRBF. Next, the association between treatment and peak TRBF was examined using the Wilcoxon nonparametric test to compare TRBF before and after treatment as a global comparison. Multivariable regression with generalized estimating equations was also used to compare TRBF before and after treatment. After primary analysis of peak TRBF, secondary analysis of quadrant-specific peak TRBF was evaluated in each model. Resulting P values were calculated based on Wald tests from the Mixed Effects model. Subject characteristics and clinical ROP features were included in regression analysis. Generalized estimating equations were used to account for 2 eyes per subject and longitudinal measures over time to compare TRBF before and after treatment. Correlation tests were performed on clinical and blood flow variables using parametric and nonparametric methods. SAS v9.4 (Statistical Analysis Software, North Carolina State University) was used to perform all statistical analyses. To determine statistical significance, 2-sided P < 0.05 was utilized in the analysis. For models with multiple variables demonstrating P < 0.05, exact P values were reported.

Results

Demographics

This cohort included 8 participants (14 eyes) with ROP who underwent ROP treatment with laser photocoagulation between 2021 and 2024. Participants were followed for evidence of reactivation for 10 months to 4 years and seen to have complete regression (no reactivation) of ROP after laser. Among the 8 participants, 3 were female (38%), 3 were Black individuals (38%), 2 were White individuals (25%), 1 was an Asian individual (13%), and 2 individuals had Hispanic ethnicity (25%) (Table 2).

Table 2.

Demographics and Clinical Features (Total 8 Subjects, 14 Eyes)

N (%) Range
Sex
 Female 3 (38%)
 Male 5 (62%)
Race
 Black 3 (38%)
 White 2 (25%)
 Other 2 (25%)
 Asian 1 (13%)
Ethnicity
 Hispani 2 (25%)
Gestational age (wks) 26.1 ± 2.8 22.9–31.6
Birth weight (grams) 869 ± 344 500–1429
Postmenstrual age at laser (wks) 40.2 ± 3.4 35–47
Current weight at laser (grams) 3025 ± 1033 1340–4750
Retinopathy of prematurity at time of laser
 Stage 3 ± 0 3
 Zone 2 ± 0 2
 Plus score 6.9 ± 0.9 6–8
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Clinical Features and Treatment Timing

Birth weight in the cohort was 869 ± 344 (range 500-1429 g), and gestational age was 26.1 ± 2.8 (range 22.9-31.6 weeks). Subjects underwent laser photocoagulation at 40.2 ± 3.4 postmenstrual weeks (range 35-47 postmenstrual weeks) (Table 2). All subjects had zone 2, stage 3 at the time of laser treatment. Seven (n = 7) subjects had plus disease (p-score >7) and one (n = 1) subject had preplus disease (p-score 6). The mean p-score was 6.9 ± 0.9 (range 6-8) (Table 2). All subjects regressed to zone 2, stage 0, p-score ≤5 within 2 months after laser.

TRBF after Treatment

Prior to ROP treatment with laser photocoagulation, subjects had a peak TRBF of 8.8 ± 2.1 a.u. compared to 7.3 ± 1.4 a.u. after treatment (mean difference = 1.5 a.u., P = 0.04). Quadrant-specific blood flow analysis found that the nasal quadrant demonstrated the most significant blood flow reduction after laser treatment (P = 0.02), followed by the superior quadrant (P = 0.03). The inferior (P = 0.3) and temporal (P = 0.4) quadrants had no significant blood flow reduction (Table 3).

Table 3.

Mean Retinal Blood Flow before and after Laser Treatment

Before Laser (0-6 Wks Prior to Laser Treatment) After Laser (1-6 Weeks after Laser Treatment) P Value
Stage 2.6 ± 0.8 1.7 ± 1.2 0.032
Zone 2 ± 0 2 ± 0 1.0
Plus score 6.3 ± 1.5 4.3 ± 1.5 0.0022
Retinal blood flow (a.u.)
 Total (all quadrants) 8.81 ± 2.11 7.28 ± 1.35 0.036
 Nasal quadrant 8.47 ± 2.12 6.68 ± 0.74 0.017
 Temporal quadrant 5.68 ± 1.29 5.19 ± 1.07 0.37
 Superior quadrant 9.19 ± 1.93 7.70 ± 0.91 0.034
 Inferior quadrant 9.63 ± 2.41 8.81 ± 1.33 0.34
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Values that are bolded are statistically significant (P < 0.05).

Longitudinal TRBF was collected at multiple time points for most subjects, ranging from 6 weeks prior to laser to 6 weeks after laser (Tables 4 and 5). After laser, within 6 weeks, zone was unchanged (P = 1.0), stage decreased (P < 0.03), and p-score decreased (P < 0.002). The peak TRBF also decreased significantly after treatment (P = 0.04). Peak TRBF decreased over time after laser treatment, but the decrease was not significant (β = –0.3 a.u./week, P = 0.2). Clinical and blood flow data were found to be correlated. There is a moderate positive relationship between plus score and nasal blood flow (rp = 0.45, P=0.045). P-score did not have a significant correlation with superior, temporal, and inferior quadrants (Table 4). Total blood flow has a strong positive correlation with quadrant-specific blood flow (Table 5).

Table 4.

Imaging Timeline

Subject Weeks before Laser Treatment
 Weeks after Laser Treatment
–6 –5 –4 –3 –2 –1 0 1 2 3 4 5 6
1 ▪
2 ▪
3 ▪
4 ▪
5 ▪ ▪
6 ▪ ▪ ▪ ▪
7 ▪ ▪ ▪ ▪
8 ▪
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Table 5.

Correlation Matrix for Blood Flow and Clinical Features

Clinical Features
 Retinal Blood Flow
Stage Plus Score Total Nasal Temporal Superior Inferior
Clinical features
 Stage rp = 0.68
(P = 0.0001)
rs = 0.71
(P < 0.0001)		 rp = 0.15
(P = 0.48)
rs = 0.077
(P = 0.71)		 rp = 0.32
(P = 0.17)
rs = 0.37
(P = 0.11)		 rp = –0.13
(P = 0.59)
rs = –0.17
(P = 0.49)		 rp = 0.069
(P = 0.77)
rs = –0.057
(P = 0.81)		 rp = 0.066
(P = 0.78)
rs = 0.029
(P = 0.90)
 Plus score rp = 0. (P=) rs = 0. (P=) rp = 0.21
(P = 0.30)
rs = 0.21
(P = 0.31)		 rp = 0.45
(P = 0.045)
rs = 0.54
(P = 0.014)		 rp = 0.12
(P = 0.62)
rs = 0.058
(P = 0.81)		 rp = 0.19
(P = 0.41)
rs = 0.20
(P = 0.40)		 rp = 0.37
(P = 0.11)
rs = 0.30
(P = 0.20)
Retinal blood flow
 Total rp = 0. (P=) rs = 0. (P=) rp = 0. (P=) rs = 0. (P=) rp = 0.80
(P < 0.0001)
rs = 0.67
(P = 0.0012)		 rp = 0.73
(P = 0.0003)
rs = 0.69
(P = 0.0007)		 rp = 0.93
(P < 0.0001)
rs = 0.91
(P < 0.0001)		 rp = 0.82
(P < 0.0001)
rs = 0.84
(P < 0.0001)
 Nasal rp = 0. (P=) rs = 0. (P=) rp = 0. (P=) rs = 0. (P=) rp = 0. (P=) rs = 0. (P=) rp = 0.53
(P = 0.015)
rs = 0.38
(P = 0.094)		 rp = 0.83
(P < 0.0001)
rs = 0.76
(P < 0.0001)		 rp = 0.76
(P = 0.0001)
rs = 0.69
(P = 0.0007)
 Temporal rp = 0. (P=) rs = 0. (P=) rp = 0. (P=) rs = 0. (P=) rp = 0. (P=) rs = 0. (P=) rp = 0. (P=) rs = 0. (P=) rp = 0.77
(P < 0.0001)
rs = 0.78
(P < 0.0001)		 rp = 0.74
(P = 0.0002)
rs = 0.71
(P = 0.0004)
 Superior rp = 0. (P=) rs = 0. (P=) rp = 0. (P=) rs = 0. (P=) rp = 0. (P=) rs = 0. (P=) rp = 0. (P=) rs = 0. (P=) rp = 0. (P=) rs = 0. (P=) rp = 0.79
(P < 0.0001)
rs = 0.84
(P < 0.0001)
 Inferior rp = 0. (P=) rs = 0. (P=) rp = 0. (P=) rs = 0. (P=) rp = 0. (P=) rs = 0. (P=) rp = 0. (P=) rs = 0. (P=) rp = 0. (P=) rs = 0. (P=) rp = 0. (P=) rs = 0. (P=)
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rp = Pearson correlation coefficients; rs = Spearman correlation coefficients.

Discussion

We found that TRBF decreased after laser photocoagulation. The significance of this finding is particularly meaningful given existing literature demonstrating that TRBF generally increases over time in an ROP cohort that does not require treatment.7 Our finding that peak TRBF decreased by 1.5 a.u. represents a 17% reduction in blood flow (Table 3). Previous studies in smaller cohorts used various other technologies to measure blood flow after laser.17,18,26 Using laser speckle flowgraphy, Matsumoto et al18 found a 46% decrease in blood flow after treatment with laser (n = 8 eyes, P = 0.0007). Previous work using standard Doppler imaging demonstrated a 32% decrease in blood flow after laser (P = 0.001).17 Overall evidence suggests that ROP treatment with laser is associated with significant ocular blood flow reduction.

Our results are also consistent with previous findings that retinal blood flow decreases after intravitreal anti-VEGF ROP treatment. We previously published findings that intravitreal anti-VEGF treatment for ROP lowers TRBF by 22.5%.19 Other groups have published similar findings.18,26 Treatment impact on retinal blood flow for eyes receiving intravitreal anti-VEGF and eyes receiving laser cannot be directly compared because of different treatment indications for anti-VEGF and laser. Evidence supports use of intravitreal anti-VEGF rather than laser for younger postmenstrual age and more posterior ROP, particularly zone 1 ROP.27, 28, 29, 30 As a result, future direct comparison of blood flow reduction by treatment modality is not possible due to lack of equipoise on the clinical profile that warrants the respective treatments.

Animal studies have likewise demonstrated a significant association between retinal blood flow, retinal VEGF,31 and avascular retina. In a rat model analogous to human zone 2, stage 3 ROP, Budd et al31 showed there was increased mRNA expression of VEGF and VEGF receptor 2 in areas of avascular retina in response to the increased blood flow requirement to compensate for hypoxia.

Quadrant-specific blood flow analysis has not been previously reported using LSCI technology in the setting of ROP. We found that the nasal quadrant demonstrated the most significant blood flow reduction after laser treatment (P = 0.02), followed by the superior quadrant (P = 0.03). There was no significant blood flow reduction in the inferior (P = 0.3) and temporal (P = 0.4) quadrants. It is unknown why the nasal quadrant demonstrated more significant blood flow reduction after laser. This was an unexpected finding given that in healthy adult controls, the temporal retina exhibits greater vascular conductance with higher flow velocities.32 In addition, the surface area of peripheral avascular retina is generally larger in the temporal quadrant relative to the nasal quadrant, and peripheral avascular retina is a risk factor for ROP severity. Additionally, quadrant-segmented images did not consistently show a greater number of vessels in the nasal quadrant (Fig 2). This suggests that LSCI is detecting hemodynamic changes that are not visually apparent on standard imaging, as there is no obvious difference that explains the more pronounced reduction in nasal TRBF. Possible reasons for the difference in nasal versus temporal flow are the lower relative amounts of vascularized retina in the nasal quadrant, and the presence of a physiologic avascular zone (the fovea) in the temporal quadrant. There is evidence that structural differences between retinal hemispheres persistent after ROP treatment,33 and further investigation on quadrant-specific differences in blood flow are needed.

Figure 2.

Figure 2

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Quadrant-specific retinal images. Superior quadrant is in blue, temporal in gray, inferior in pink, and nasal in yellow.

Peak TRBF decreased over time (per week) after laser treatment, but the decrease was not significant (β = –0.3 a.u./week, P = 0.2). Previous studies demonstrated a significant sustained blood flow pattern after anti-VEGF treatment for ROP; however, this study may have lacked adequate power to assess blood flow over time after laser.19

Decreased TRBF after laser therapy may be linked to improved retinal oxygenation due to decreased demand for tissue oxygenation posttherapy.34 In ROP, peripheral retinal hypoxia due to peripheral avascular retina leads to increased production of VEGF. Increased VEGF binding to VEGFR2 receptors also leads to increased nitric oxide, which promotes vasodilation. As a result, vessels become dilated and tortuous, and TRBF increases, a global effort to compensate for retinal ischemia.35 Clinically, this manifests as increased p-scores, and ultimately, plus disease. Laser photocoagulation works by ablating retinal tissue and replacing metabolically active cells with glial scars, thereby decreasing the retina's oxygen consumption.34 Photoreceptor replacement by glial scarring reduces the number of mitochondria and increases the amount of oxygen that can now reach the inner retina.34 Studies have shown this process is less immediate for laser as compared to intravitreal anti-VEGF, thus demonstrating the advantage of longitudinal data collection to address the potential for TRBF changes to progress in the weeks before and after laser treatment, not just the immediate pretreatment and posttreatment interval.

Unique aspects of this study include point-of-care blood flow measurement and quadrant-specific LSCI blood flow analysis—approaches not previously reported in ROP. Point-of-care assessment demonstrates the feasibility of incorporating blood flow data into real-time clinical decision-making. Although further validation is needed to establish clinical utility, feasibility, and practicality are unlikely to limit assessment of TRBF in this context. By subclassifying TRBF into quadrant-specific components, this study provides novel insight into the role of nasal retinal blood flow and underscores the potential of LSCI to deepen understanding of regional flow patterns in ROP.

Strengths of this study include a larger cohort than prior reports, longitudinal follow-up, and quadrant-specific analysis. Blood flow was assessed over a 12-week interval (6 weeks before and 6 weeks after laser photocoagulation). A longitudinal approach, rather than a single prelaser and postlaser comparison, was chosen for both practical and biological reasons. Few subjects had data collected immediately before and after laser treatment, and retinal blood flow in ROP is known to evolve progressively before intervention and to recover gradually thereafter.36 Therefore, statistical modeling was used to account for variable data collection time points, inclusion of both eyes from some subjects, and repeated measures over time. All participants were followed clinically for at least 10 months postlaser, with some followed for up to 4 years after treatment. Future investigation of untreated eyes with ROP may inform our understanding of baseline TRBF patterns in neonates who do not require treatment.

Limitations

This study had a limited but sufficient sample size. Subjects were imaged at variable time points ranging from 6 weeks prior to laser to 6 weeks after laser. Some infants enrolled in the study after their laser treatment, based on the availability of parents to provide consent. Other infants were discharged or transferred from our hospital before longitudinal follow-up was complete. Fortunately, statistical tools (generalized estimating equations) allowed us to account for the different follow-up schedules and different clinical features of each eye, including accounting for within subject variation. None of the reasons for missing time points are expected to significantly bias our results. Additionally, while neonates requiring cardiac surgery were excluded, nonsurgical cardiovascular pathology was not controlled for, resulting in a limitation of the study.

Conclusions

We demonstrate the feasibility of blood flow measurement, including quadrant-specific analysis, alongside validated metrics like stage and p-score coincident with the regression of ROP after laser photocoagulation. Using LSCI-based blood flow measurements, we observed significantly lower peak TRBF after ROP treatment with laser photocoagulation, with corresponding reduction in ROP stage and p-score. Blood flow reduction was most significantly impacted in the nasal quadrant, a finding worthy of further study. Blood flow may offer an objective biomarker for ROP treatment response.

Manuscript no. XOPS-D-25-00891.

Footnotes

This study was presented at the Association for Research in Vision and Ophthalmology Annual Meeting, May 4-8, 2025, Salt Lake City, Utah.

The Article Publishing Charge (APC) for this article was paid by the Department of Ophthalmology and Visual Sciences, University of Maryland School of Medicine.

Disclosure(s):

All authors have completed and submitted the ICMJE disclosures form.

The authors made the following disclosures:

A.S.: Grants – National Institute on Aging of the National Institutes of Health, National Institute of Neurological Disorders and Stroke of the National Institutes of Health, National Eye Institute of the National Institutes of Health; Consultant – Vasoptic Medical, Inc.; Travel expenses – Vasoptic Medical, Inc.; Employment – Vasoptic Medical Inc.

A.R.: Grants – National Institute on Aging of the National Institutes of Health, National Institute of Neurological Disorders and Stroke of the National Institutes of Health, National Eye Institute of the National Institutes of Health; Consultant – SIGT, LLC; Employment – Vasoptic Medical Inc.; Royalties or licenses – Vasoptic Medical Inc, Johns Hopkins University; Honoraria – National Science Foundation, National Institutes of Health; Patents planned, issued or pending – Vasoptic Medical, Inc. (VMI), Johns Hopkins University; Leadership or fiduciary role in other board, society, committee or advocacy group, paid or unpaid – Vasoptic Medical, Inc. (VMI); Stock or stock options – Vasoptic Medical, Inc. (VMI).

J.L.A.: Financial support – Vasoptic Medical Inc.; Grants – Vasoptic Medical Inc.

This study was supported by the National Eye Institute of the National Institutes of Health, Maryland Industrial Partnerships (MIPS), and grants K23EY03525, SBIR R43EY030798, UL1TR003098, and MIPS7103. A.R. reports financial support was provided by Vasoptic Medical Inc. J.L.A.'s work has been funded by Maryland Industrial Partnerships (MIPS) Program (grant 7103, funded in part by Vasoptic Medical).

Data Availability: Deidentified data can be made available upon reasonable request to corresponding author.

HUMAN SUBJECTS: Human subjects were included in this study. This study was conducted as part of an ongoing prospective study at the University of Maryland Neonatal Intensive Care Unit (NICU) in Baltimore, MD. The study was approved by our accredited institutional review board (HP-00088705) in adherence with US Health Insurance Portability and Accountability Act guidelines and the Declaration of Helsinki. The study was conducted from January 2021 to December 2024. Informed consent was obtained from the parents of each subject after explanation of the nature and possible consequences of participating in the study.

No animal subjects were used in this study.

Author Contributions:

Conception and design: Wang, Rege, Alexander

Analysis and interpretation: Kilby, Zhou, Magder, Sinha, Rege, Alexander

Data collection: Mansoor, Kilby, Wu, Kapoor, Ward, Vexlund, Williams, Levin, Alexander

Obtained funding: Alexander

Overall responsibility: Mansoor, Wang, Forbes, Zhou, Das, Levin, Sundararajan, Sinha, Rege, Alexander

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