Quantitative assessment of intervortex anastomosis in central serous chorioretinopathy and fellow eyes: Does the size of anastomotic vessels matter for the diagnosis?

PURPOSE: To evaluate the frequency and size of intervortex anastomosis at the posterior pole on en-face spectral domain optical coherence tomography (SD-OCT) images in central serous chorioretinopathy (CSC) cases and their fellow eyes and its associations with choroidal morphology. METHODS: Sixty-five treatment-naive eyes of 65 patients with CSC, 65 fellow eyes, and 55 eyes of healthy age-matched participants were included. The presence of intervortex anastomosis at the watershed zone and asymmetry of the choroidal vessels between the superior and inferior macula were evaluated using 6 × 6 mm en-face SD-OCT. The diameter of the widest Haller vessel and the diameter of the widest anastomotic Haller vessel passing through the watershed zone were measured on en-face SD-OCT images. The choroidal vascularity index (CVI) was assessed using ImageJ software. RESULTS: Intervortex vein anastomosis on the horizontal watershed zone was detected in 75.4% diseased eyes, 61.5% in fellow eyes, and 36.4% in healthy age-matched controls (p < 0.001). The mean CVI was significantly higher in both diseased (74.3 ± 2.3%) and fellow (73.8 ± 2.2%) eyes of CSC cases than in healthy controls (72.5 ± 2.3%) (p = 0.002, p = 0.013, respectively). In the cases with intervortex vein anastomosis, the diameter of the widest anastomotic Haller vessel passing through the watershed zone was 0.40 ± 0.10 mm in diseased eyes, 0.35 ± 0.11 mm in fellow eyes, and 0.30 ± 0.09 mm in healthy age-matched controls (p = 0.001). CONCLUSIONS: Intervortex anastomosis might be seen as a variation in normal eyes, however, its frequency and the size of anastomotic vessels are significant higher in not only CSC but also in fellow eyes.

POLYPOIDAL LESIONS ASSOCIATED WITH CHOROIDAL NEVI.

PURPOSE: To investigate eyes with polypoidal lesions associated with choroidal nevi, their multimodal imaging characteristics, and long clinical follow-up. METHODS: Multicenter, retrospective case series study of patients with polypoidal lesions overlying choroidal nevi. Demographic and clinical information were recorded. Multimodal imaging including color fundus photography, optical coherence tomography, optical coherence tomography angiography, fundus fluorescein angiography, indocyanine angiography, and A- and B-scan ultrasonography were analyzed for nevus and polypoidal lesion characteristics. RESULTS: Fourteen eyes (14 patients; mean age: 70.3 ± 6.7 years) with polypoidal lesions overlying choroidal nevi were included. The mean follow-up duration was 50.0 ± 27.9 months (range 12-108). All nevi were pigmented on color fundus photography, flat on ultrasonography with a mean basal diameter of 3.8 ± 0.4 mm. In all but one eye, optical coherence tomography showed a shallow irregular pigment epithelium detachment overlying the nevus. A total of 11/14 eyes (78.6%) had exudative activity, 9 eyes received intravitreal anti-vascular endothelial growth factor injections, and one eye required intravitreal anti-vascular endothelial growth factor combined with photodynamic therapy. Mean visual acuity was 20/32 at baseline and 20/50 at final visit. CONCLUSION: We present the largest known cohort of eyes with polypoidal lesions associated with choroidal nevi with up to 9 years follow-up. The exudative degree of the polypoidal lesion in this condition is variable and treatment decisions should be taken on an individual basis. We hypothesize that choroidal ischemia because of altered choroidal vasculature rather than Haller layer hyperpermeability plays a role in the formation of polypoidal lesions overlying nevi.

Influence of fellow eye on the diagnosis and classification of central serous chorioretinopathy.

PURPOSE: To assess the influence of fellow eye information on diagnosis and classification of central serous chorioretinopathy (CSCR) using multimodal imaging-based classification. METHODS: This was a retrospective, observational study including patients with CSCR with unilateral or bilateral involvement. Multimodal images of both eyes of each patient were compiled and presented to two masked retina specialists subdivided into three groups: (1) both eye data, (2) right eye data and (3) left eye data. The masked observers graded the CSCR as per the new CSCR classification into simple and complex CSCR in three different scenarios as subdivided above. Interobserver and intraobserver agreement was assessed using Cohen's kappa (95% confidence intervals). RESULTS: A total of 206 eyes of 103 patients with unilateral or bilateral CSCR were graded. We found a "strong" intraobserver and interobserver agreement when one eye versus both eye data was provided in terms of "simple CSCR" or "complex CSCR" (kappa value = 0.77 and 0.87, p < 0.001, and kappa value = 0.85 and 0.76, p < 0.001, respectively). Forty-three eyes (10.55%) showed discrepancy in classification between observers for individual eyes, whereas only 13 eyes (6.53%) showed discrepancy between observers when both eye data was provided. CONCLUSION: We conclude that fellow eye information was helpful in solving diagnostic dilemmas and reached 85% consensus in the diagnosis of CSCR between the observers. We found that information of fellow eyes led to a discrepancy only in 6.53% cases with 2.42% cases that had a controversial diagnosis of CSCR. Multimodal imaging-based CSCR classification provides objective approach to diagnose and classify CSCR.

THE TARGET SIGN: A Near Infrared Feature and Multimodal Imaging in a Pluri-Ethnic Cohort with RDH5-Related Fundus Albipunctatus.

PURPOSE: Retinol dehydrogenase 5 (RDH5)-related fundus albipunctatus can present with phenotypic variability. Our purpose was to investigate new clinical characteristics and multimodal imaging findings in patients from different ethnic origins, carrying different mutations. METHODS: Multicenter international retrospective case series of 18 patients with genetically confirmed RDH5-related fundus albipunctatus. Patients' files were reviewed for fundus images, visual acuity, macular optical coherence tomography scans, near-infrared images, fundus autofluorescence, electroretinogram, and genetic mutations. Imaging and electroretinogram findings. RESULTS: All eyes (n = 36, 100%) showed small circular findings seen on near-infrared images, termed as the "target sign," correlating to the yellowish dots seen clinically and to the distinct hyperreflective linear lesions on optical coherence tomography at the level between external limiting membrane and retinal pigment epithelium. Perifoveal atrophy with foveal sparing was seen in 4 eyes of 2 patients (both RDH5-c.160C>T, p.R54X mutation). Fundus autofluorescence revealed small hyperautofluorescent dots (n = 16, 44.4%). Scotopic electroretinograms were significantly reduced in all cases with an electronegative pattern, 66.7% displayed cone dysfunction. CONCLUSION: Our results show distinct imaging findings present in all patients with fundus albipunctatus independent of ethnicity or genetic mutation. Our results can facilitate the current algorithm to diagnose RDH5-related fundus albipunctatus and allow for targeted genetic testing.

Interocular asymmetry in distribution of leaks in central serous chorioretinopathy.

PURPOSE: To study interocular asymmetry in distribution of leaks in central serous chorioretinopathy (CSC). MATERIAL AND METHODS: Patients with unilateral CSC were included in this retrospective multicenter study. All patients received multimodal imaging. The prevalence of leaks within 1 disk diameter (DD) peripapillary area and the mean shortest distance between a leak and the optic disk edge was analyzed for the right and left eyes separately based on FA images. Clinical and morphological characteristics were collected and compared between eyes with a peripapillary leak and eyes with a leak elsewhere. RESULTS: In total, 152 eyes (77 right eyes and 75 left eyes) of 152 patients (128 males and 24 females) with a mean age of 45.2 ± 9.8 years were included. The mean distance from the leak to the edge of the optic disk was statistically significantly lower (p = 0.0003), and the prevalence of the leaks within the 1 DD-peripapillary area was higher in the left eye than in the right eye (32.1% versus 10.7%, respectively, p = 0.0017). The eyes with a peripapillary leak had a longer duration of the disease (p < 0.05), a wider area of retinal pigment epithelium alteration (p < 0.001), and a higher prevalence of outer retinal atrophy (p < 0.001) compared to the eyes with a leak elsewhere. CONCLUSION: The left eye showed closer location of the leak to the optic disk edge and higher prevalence of leaks within the peripapillary area. The cases with peripapillary leak commonly demonstrated characteristics of chronic CSC despite relative preservation of visual acuity.

Short-term choroidal vascular changes after aflibercept therapy for neovascular age-related macular degeneration.

INTRODUCTION: The purpose of this study was to evaluate choroidal vascular changes in patients with neovascular age-related macular degeneration (nAMD) treated with aflibercept injection over a 3-month period. METHODS: Enhanced depth imaging optical coherence tomography scans of 60 eyes with treatment-naïve nAMD and 60 unaffected fellow eyes were retrospectively analyzed. Data was collected at baseline and after 3 monthly intravitreal injections of aflibercept. The ImageJ software was used to binarize OCT scans and measure total choroid area (TCA), luminal area (LA), and stromal area (SA). Choroidal vascularity index (CVI) was defined as the ratio of LA to TCA. RESULTS: After treatment, subfoveal choroidal thickness (CT) in nAMD eyes significantly decreased from 210. 6 ± 61.6 to 194.6 ± 58.7 µm (P < 0.001), TCA from 1.620 ± 0.502 to 1.500 ± 0.451 mm2 (P < 0.001), LA from 1.075 ± 0.335 to 0.985 ± 0.307 mm2 (P < 0.001), SA from 0.545 ± 0.176 to 0.516 ± 0.153 mm2 (P = 0.005), and CVI from 66.36 ± 2.89 to 65.46 ± 2.87% (P = 0.009). The decrease of CVI after treatment was significantly correlated with baseline CVI (Rs = 0.466, P < 0.001), but not with the change in BCVA and presence of dry macula after treatment (always P > 0.05). CONCLUSION: Choroidal thickness and vascularity significantly decreased after treatment with aflibercept in nAMD eyes. Besides the pharmacologic effect on the neovascular lesion, aflibercept may induce vascular changes also on the underlying choroid.

CHOROIDAL VASCULARITY INDEX QUANTIFICATION IN GEOGRAPHIC ATROPHY USING BINARIZATION OF ENHANCED-DEPTH IMAGING OPTICAL COHERENCE TOMOGRAPHIC SCANS.

PURPOSE: To evaluate choroidal structural changes occurring over time in geographic atrophy (GA) secondary to age-related macular degeneration using choroidal vascularity index (CVI). METHODS: Enhanced-depth imaging optical coherence tomography scans of 34 patients with GA and 32 control subjects were retrospectively analyzed. Data were collected at baseline and after a mean follow-up of 18.3 ± 8.3 months. Choroidal images were binarized using the ImageJ software, and the luminal area and stromal area were segmented. Choroidal vascularity index was defined as the ratio of luminal area to total choroid area. RESULTS: Patients with GA showed significantly lower values of CVI, total choroid area, luminal area, and subfoveal choroidal thickness compared to control subjects (65.83 ± 3.95 vs. 69.33 ± 3.11, P < 0.001; 0.400 ± 0.239 mm vs. 0.491 ± 0.132, P = 0.006; 0.263 ± 0.152 mm vs. 0.340 ± 0.094, P = 0.002; 185.2 ± 79.8 µm vs. 216.8 ± 58.8 µm, P = 0.036, respectively). Best-corrected visual acuity was significantly correlated only with choroidal thickness (R = -0.509; P = 0.002). During the follow-up period in patients with GA, subfoveal choroidal thickness decreased from 185.2 ± 79.8 to 152.2 ± 73.1 (P = 0.001), stromal area increased from 0.138 ± 0.090 mm to 0.156 ± 0.068 (P = 0.028), and CVI decreased from 65.83 ± 3.95 to 62.24 ± 3.63 (P < 0.001). CONCLUSION: This study showed for the first time that CVI is reduced in patients with GA, and that this metric further worsened during the follow-up period.

OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY CHARACTERISTICS OF POLYPOIDAL CHOROIDAL VASCULOPATHY SECONDARY TO CHRONIC CENTRAL SEROUS CHORIORETINOPATHY.

PURPOSE: To report diagnostic capability of optical coherence tomography angiography (OCTA) in detecting polypoidal choroidal vasculopathy and its morphologic characteristics in white patients with chronic central serous chorioretinopathy. METHODS: Retrospective consecutive series of 20 eyes (17 consecutive patients) with a diagnosis of polypoidal choroidal vasculopathy secondary to chronic central serous chorioretinopathy based on clinical and multimodal imaging were included. All patients underwent a complete ophthalmologic examination, including best-correct visual acuity, fundus autofluorescence, fluorescein and indocyanine green angiography, spectral-domain optical coherence tomography, and OCTA. RESULTS: In all eyes (100%), OCTA revealed the branching vascular network as a hyperflow lesion in both choriocapillaris and outer retina layers. Segmentation of the choriocapillaris in OCTA, in correspondence of the polypoidal dilation detected at indocyanine green angiography, showed a hyperflow round structure in 75% of cases and hypoflow round structure in 15%. Two of 20 eyes (10%) had no detectable polyps on OCTA. CONCLUSION: Optical coherence tomography angiography is a noninvasive imaging modality allowing a good visualization of both branching vascular network and polyp dilations. Our findings suggest that OCTA is a useful tool in the investigation of chronic central serous chorioretinopathy complicated by polypoidal choroidal vasculopathy.

Ocular surface and respiratory tract damages from occupational, sub-chronic exposure to fluorspar: case report and other considerations.

OBJECTIVES: To report the ocular surface and respiratory tract damages due to a sub-chronic (3 months), occupational exposure to fluorspar dust in case of inconsistent use of personal protective equipment. METHODS: A 50-year-old man was referred to our clinic with bilateral conjunctival injection, ocular foreign body sensation and symptoms of ocular discomfort. He reported having 3 days before an urgent hospital admission for dyspnoea with odynophagia, hyposmia, nausea, vomiting, headache and asthenia. Otorhinolaryngological examination revealed a severe hypertrophic rhinopharyngitis and a significant decrease in overall sensitivity to olfactory stimuli. General anamnesis was negative for previous diseases or medication use. RESULTS: Ocular examination revealed a diffuse injection of the ocular surface with some areas of conjunctival and limbal ischaemia, a best-corrected visual acuity of 20/25 in both eyes, an intraocular pressure of 23 and 21 mmHg, respectively, in the right and in the left eyes, and a normal fundus oculi. Assessment of the tear film and ocular surface showed the presence of dry eye disease. Based on medical history and clinical tests, initial diagnostic hypothesis was ocular surface burn due to chemical exposure, i.e. to fluorspar. Therefore, anterior segment fluorescein angiography was performed to confirm the extension of conjunctival and limbal ischaemia. Thus, ocular ischaemia was detected in approximately 10 clock hours of limbus and in 50% of conjunctiva. CONCLUSIONS: The present work remarks the importance of using protective equipment for preventing ocular and respiratory tract damages in workers occupationally exposed to the 'acid-grade fluorite'.

Evaluation of Vascular Changes with Optical Coherence Tomography Angiography after Plaque Radiotherapy of Choroidal Melanoma.

AIM: The purpose of this paper was to evaluate whether optical coherence tomography angiography (OCT-A) can be used to quantify the vascular changes in radiation maculopathy, and changes in the tumor vasculature in eyes treated with plaque radiotherapy for choroidal melanoma. METHODS: In this prospective study, we evaluated 39 Caucasian patients with choroidal melanoma (39 eyes) treated with ruthenium-106 plaque radiotherapy. The patients underwent complete ophthalmic examination, bulbar echography, and OCT-A before and 1 year after treatment. RESULTS: At baseline, the mean best-corrected visual acuity (BCVA) in the affected eyes was 0.35 ± 0.40 logMAR, and the mean tumor thickness was 2.68 ± 0.25 mm at A-scan echography. After treatment, the mean BCVA increased to 0.41 logMAR, the mean tumor thickness decreased to 1.66 ± 0.23 mm, and the tumor basal diameter was significantly reduced (U = 108, p = 0.001). Moreover, the capillary vessel density was significantly lower in all Early Treatment of Diabetic Retinopathy Study sectors, and both the vessel and flow areas were significantly reduced (p = 0.030 and p = 0.001, respectively). CONCLUSIONS: OCT-A is a noninvasive, reliable method with which to quantify the vessel changes in radiation maculopathy and, given the association between vascularization and malignancy, this procedure may be an aid in treatment decision-making and in monitoring the efficacy of treatment.

Navigated yellow subthreshold micropulse laser for refractory cystoid macular edema following rhegmatogenous retinal detachment surgery.

Purpose: To report the efficacy and safety of navigated 577nm yellow subthreshold micropulse laser (YSML) treatment in a case of refractory cystoid macular edema (CME) following combined phaco-vitrectomy for rhegmatogenous retinal detachment (RRD). Observations: A 69-year-old male patient complained a slow and progressive visual loss in the right eye (RE) since two months. A complete ophthalmological evaluation was performed. Best corrected visual acuity (BCVA) was hand motion and slit lamp examination revealed a nuclear cataract and a total macula-off RRD in the RE. Patient underwent a combined phaco +25 gauge pars plana vitrectomy (PPV) with 5000 cSt silicon oil (SO) tamponade. At the 3-month follow up BCVA was 20/250, retina was completely flat but a macular proliferative vitreoretinopathy (PVR) was detected with swept source optical coherence tomography (SS-OCT) and a second 23 G PPV with PVR peeling and SO removal was performed. At 1 month visit from the second surgery retina was flat and BCVA was 20/200 due to a persistent CME. Oral carbonic anhydrase inhibitors and topical steroids were administered for 2 months without any improvements. At this point, YSML was applied with a macular grid pattern and at three months follow up visit SS-OCT showed a complete resolution of CME, BCVA was 20/100 and these anatomical and functional outcomes were maintained at 6 months follow-up. Conclusions and importance: YSML treatment may be considered a safe and effective treatment strategy for the management of refractory CME following complex RRD surgery cases.

Exudative Progression of Treatment-Naïve Nonexudative Macular Neovascularization in Age-Related Macular Degeneration: A Systematic Review With Meta-Analyses.

PURPOSE: To systematically review and report the rate of exudative progression over time in patients with nonexudative macular neovascularization (MNV) in age-related macular degeneration (AMD). DESIGN: Systematic review with prevalence meta-analyses and individual participant meta-analysis. METHODS: We searched 10 literature databases on March 26, 2023, for studies of consecutive patients with treatment-naïve nonexudative MNV in AMD. The primary outcome of interest was time from diagnosis to exudative progression. We conducted meta-analyses on the prevalence of exudative progression at 1 and 2 years. Where possible, we extracted individual participant data from studies and conducted an individual participant meta-analysis and explored the exudative progression using a time-to-event curve. RESULTS: We identified 16 eligible studies with a total of 384 eyes with nonexudative MNV. Exudative progression had occurred in 20.9% (95% CI 13.1%-29.8%) of eyes at 1 year and in 30.7% (95% CI 21.8%-40.4%) at 2 years. Similar results were observed in the individual participant meta-analysis, showing exudative progression in 18.9% (95% CI 13.5%-26.3%) of eyes at 1 year and 31.3% (95% CI 24.2%-40.0%) at 2 years. Risk factors for a fast exudative progression were the presence of subretinal lipid globules, large MNV areas, rapid MNV growth, growth in pigment epithelium detachment height and width, appearance of a branching pattern, and development of a hyporeflective halo around the MNV. CONCLUSIONS: Nonexudative MNVs in AMD are at high risk of exudative progression. Recognition of these lesions may allow for better individualized follow-up regimens in which closer monitoring may facilitate earlier diagnosis of exudative progression.

Outcomes after giant peripheral retinotomy and anterior flap retinectomy for rhegmatogenous retinal detachments with advanced proliferative vitreoretinopathy using small gauge vitrectomy.

PURPOSE: To analyze the visual and anatomical outcomes for eyes with rhegmatogenous retinal detachment (RRD) and advanced proliferative vitreoretinopathy (PVR) undergoing giant peripheral retinotomy (GPR) using 25-gauge pars plana vitrectomy (PPV). METHODS: In this retrospective multi-center study, patients with RRD with either anteroposterior or circumferential retinal shortening and advanced PVR requiring more than 90-degree GPR with/without relaxing retinotomy were included. Subjects of either gender, any age group, and with complete surgical notes were included. Outcome measures of the study included anatomical success (i.e. complete retinal re-attachment) at 6 months using survival analysis, visual outcomes, and post-operative complications. RESULTS: Forty-one eyes of 41 patients (33 males) with a mean age of 44.9 ± 21.4 years were included. At 6 months follow-up, anatomical success was seen in 29 eyes (70.7%) with a cumulative re-attachment rate of 66% (95% confidence interval = 48 = 79%). All re-detachments occurred at ≤6 months with a peak at 4-6 months (n = 9). Twenty-three eyes (56%) achieved ambulatory vision (5/200) or better. Direct perfluorocarbon liquid-silicone oil exchange was performed in 20 eyes. Intra-operative complications included persistent retinal folds (2 eyes), subretinal air (1 eye), and subretinal bleed (1 eye). Eleven eyes (26.8%) developed secondary glaucoma (2 eyes required a drainage device), and hypotony of ≤6 mmHg was noted in 3 eyes (7.3%). Corneal decompensation was noted in 8 eyes (19.5%), and 3 eyes (7.3%) underwent re-surgery for re-RRD. CONCLUSION: After GPR using small gauge PPV, two-thirds achieve anatomical success, and over half have ambulatory vision, but overall post-operative complications can occur in more than half of the eyes.

Peripapillary fluid: Obvious and not so obvious!

Intraretinal or subretinal fluid in the peripapillary area can be clinically visualized in conditions such as peripapillary choroidal neovascularization, optic disc pit maculopathy, and optic nerve head tumors and granulomas. Optical coherence tomography (OCT) helps to visualize peripapillary fluid in many other chorioretinal conditions such as peripapillary pachychoroid syndrome, posterior uveitis, central retinal vein occlusion, malignant hypertension, hypotonic maculopathy as well as neuro-ophthalmological conditions such as glaucoma, microcystic macular edema and disc edema due papilledema, non-arteritic anterior ischemic optic neuropathy, neuroretinitis, and diabetic papillopathy. Often, the differential diagnosis of peripapillary fluid is a bit tricky and may lead to misdiagnosis and improper management. We describe a diagnostic algorithm for peripapillary fluid on OCT and outline the salient features and management of these conditions.

Iatrogenic ophthalmic artery occlusion after platelet-rich plasma dermal filler documented with ultra-widefield imaging.

PURPOSE: To report a case of iatrogenic ophthalmic artery occlusion (OAO) secondary to platelet-rich plasma (PRP) dermal filler injection for facial rejuvenation documented with ultra-widefield imaging. METHODS: Case report. RESULTS: A 45-year-old woman developed a sudden and painful vision loss in the left eye (LE) after a dermal filler injection of PRP in the left glabellar region. She immediately received intravenous corticosteroids with no improvements. Two weeks later a complete ophthalmological examination including visual acuity (VA), fundus examination, ultra-widefield fundus autofluorescence and fluorescein angiography, and optical coherence tomography was performed. A diagnosis of iatrogenic OAO in the LE with profound ocular ischemia was made and VA remained no light perception. Monthly follow-up visits were scheduled to ascertain the onset of any ocular complication. CONCLUSIONS: Dermal filler injections of PRP can lead to rare but devastating side effects with permanent visual loss. Considering that there is currently no validated treatment strategy, prevention could be the real key of iatrogenic OAO management.

Influence of protocol scan on choroidal vascularity measurements: a spectralis optical coherence tomography study.

OBJECTIVES: To compare choroidal vascularity index (CVI) measurements using the automated image binarization algorithm in healthy subjects with two Spectralis spectral-domain optical coherence tomography (SD-OCT) protocol scans. METHODS: Sixty-nine eyes of 69 healthy volunteers were included in this cross-sectional prospective study. Two subsequent horizontal 20°line scans passing through the fovea were acquired with enhanced-depth imaging mode with high speed (HS) and high resolution (HR) protocol scans. CVI and its subcomponents were measured with the previously validated automated algorithm. Differences between choroidal measurements obtained with HS and HR protocol scans were evaluated with t-test and Bland & Altman plots. RESULTS: A total of 33 male (47.8%) and 36 female (52.2%) subjects with a mean age of 35.1 ± 13.4 years were included. Overall, HS protocol scan was associated with significant lower values of total choroidal area (-0.047 mm2) and stromal choroidal area (-0.036 mm2), and a significant greater value of CVI (+0.010%) if compared to HR protocol. Luminal choroidal area was lower when calculated with the HS protocol, although it did not reach significance. To compare the two different protocols, the number of pixels should be multiplied for 3.87 ×5.73 when the CVI is measured on a HR OCT b scan and 3.87 ×11.46 for the HS OCT b scan. CONCLUSIONS: HS and HR acquisition modes significantly influence CVI and its subcomponents values measured with the automated software. However, adopting the scale factors can minimize the differences between the two protocol scans.