Retinal and choroidal responses to panretinal photocoagulation: an ultrastructural perspective

Detection sensitivity of fluorescence lifetime imaging ophthalmoscopy for laser-induced selective damage of retinal pigment epithelium

PURPOSE

To investigate the sensitivity of fluorescence lifetime imaging ophthalmoscopy (FLIO) to detect retinal laser spots by comparative analysis with other imaging modalities.

METHODS

A diode laser with a wavelength of 514 nm was applied with pulse durations of 5.2, 12, 20, and 50 µs. The laser pulse energy was increased so that the visibility of the laser spot by slit-lamp fundus examination (SL) under the irradiator's observation covers from the subvisible to visible range immediately after irradiation. The irradiated areas were then examined by fundus color photography (FC), optical coherence tomography (OCT), fundus autofluorescence (AF), FLIO, and fluorescein angiography (FA). The visibility of a total of over 2200 laser spots was evaluated by two independent researchers, and effective dose (ED) 50 laser pulse energy values were calculated for each imaging modality and compared.

RESULTS

Among examined modalities, FA showed the lowest mean of ED50 energy value and SL the highest, that is, they had the highest and lowest sensitivity to detect retinal pigment epithalium (RPE)-selective laser spots, respectively. FLIO also detected spots significantly more sensitively than SL at most laser pulse durations and was not significantly inferior to FA. AF was also often more sensitive than SL, but the difference was slightly less significant than FLIO.

CONCLUSION

Considering its high sensitivity in detecting laser spots and previously reported potential of indicating local wound healing and metabolic changes around laser spots, FLIO may be useful as a non-invasive monitoring tool during and after minimally invasive retinal laser treatment.

Quantitative Evaluation of Fundus Autofluorescence in Laser Photocoagulation Scars for Diabetic Retinopathy: Conventional vs. Short-Pulse Laser

Short-pulse laser is popular for its advantages like less pain. However, its effectiveness is still debated. The aim of this study was to compare fundus autofluorescence (FAF) luminosity changes of laser photocoagulation scars between the conventional laser (0.2 s) and the short-pulse laser (0.02 s) for diabetic retinopathy. Conventional and short-pulse laser photocoagulations were performed in six and seven eyes, respectively. FAF images were captured at 1, 3, 6, 12, and 18 months after the treatments. To evaluate FAF, individual gray-scale values of the laser scars adjacent to the retinal arcade vessels were recorded; then, the mean gray values of the scars were divided by the luminosity of arcade vein. The average luminosity ratio of laser scars at 1, 3, 6, 12, and 18 months were 1.51 ± 0.17, 1.26 ± 0.07, 1.21 ± 0.03, 0.95 ± 0.11, and 0.89 ± 0.05 with conventional laser and 1.91 ± 0.13, 1.50 ± 0.15, 1.26 ± 0.08, 1.18 ± 0.06, and 0.97 ± 0.04 with short-pulse laser, respectively. Findings suggest the short-pulse laser displayed delayed hypoautofluorescence progression. This implies potential postponement in post-irradiation atrophic changes, as well as metabolic amelioration delay in the ischemic retina, when compared to conventional laser treatment.

Quantification of macular perfusion following panretinal photocoagulation for diabetic retinopathy: An optical coherence tomography angiography study

PURPOSE

To assess the effects of panretinal photocoagulation (PRP) on the microvascular structure of the macula and central thickness of the macula and choroid via optical coherence tomography angiography (OCTA).

METHODS

In this prospective clinical study, 43 eyes of 31 patients with severe non-proliferative diabetic retinopathy or early proliferative diabetic retinopathy were included. Before and at the third and sixth months after PRP, the foveal avascular zone (FAZ) area, acircularity index (AI), foveal density (FD), and vascular density of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) were evaluated using OCTA. The central macular thickness (CMT) and subfoveal choroidal thickness (SCT) were also measured after PRP.

RESULTS

There was no difference between the FAZ area, AI, FD, and vessel density of the SCP and DCP before and at the third and sixth months after PRP (all p>0.05). The CMT value was higher at the third and sixth months than at baseline (p = 0.002 and p = 0.001, respectively). The SCT value was lower at the third and sixth months than at baseline (p = 0.002 and p = 0.001, respectively).

CONCLUSION

PRP is a beneficial and reliable method that supports the integrity of the macular microvascular structure. After PRP, the CMT increases, and the SCT decreases.

Coughing-induced retinal pigment epithelial tear after trabeculectomy combined with pars plana vitrectomy

Purpose

Observations

Conclusions and importance

Choriocapillaris: Fundamentals and advancements

The choriocapillaris is the innermost structure of the choroid that directly nourishes the retinal pigment epithelium and photoreceptors. This article provides an overview of its hemovasculogenesis development to achieve its final architecture as a lobular vasculature, and also summarizes the current histological and molecular knowledge about choriocapillaris and its dysfunction. After describing the existing state-of-the-art tools to image the choriocapillaris, we report the findings in the choriocapillaris encountered in the most frequent retinochoroidal diseases including vascular diseases, inflammatory diseases, myopia, pachychoroid disease spectrum disorders, and glaucoma. The final section focuses on the development of imaging technology to optimize visualization of the choriocapillaris as well as current treatments of retinochoroidal disorders that specifically target the choriocapillaris. We conclude the article with pertinent unanswered questions and future directions in research for the choriocapillaris.

Choroid structure analysis following initiation of hemodialysis by using swept-source optical coherence tomography in patients with and without diabetes

We aimed to evaluate choroid structural changes using swept-source optical coherence tomography (SS-OCT) following hemodialysis initiation in diabetic and nondiabetic patients with end-stage kidney disease (ESKD). In this multicenter, prospective, cross-sectional study, diabetic (DM group; 30 eyes; 16 patients) and nondiabetic patients (NDM group; 30 eyes; 15 patients) with ESKD were evaluated after hemodialysis initiation. SS-OCT findings were analyzed using a manual delineation technique and binarization method before the first and last hemodialysis sessions, conducted approximately 2 weeks apart. Subfoveal choroidal thickness changes and mean large choroidal vessel layer thickness were significantly greater in the DM group (−13.3% ± 2.5% and −14.5% ± 5.2%, respectively) than the NDM group (−9.5% ± 3.1% and −9.2% ± 3.4%, respectively; p = 0.049 and p = 0.02, respectively). Binarized SS-OCT analysis revealed that the mean subfoveal choroidal area was significantly larger in the DM group (−21.9% ± 6.5%) than the NDM group (−17.2% ± 5.9%; p = 0.032). The change ratio in mean luminal area values was significantly greater in the DM group (−27.7% ± 8.7%) than the NDM group (−17.7% ± 5.8%; p = 0.007). The DM group exhibited substantial changes in the choroidal layer, possibly reflecting choroidal vascular disorders caused by diabetes.

The effect of silicone oil presence time on macular and choroidal thickness with macula-off rhegmatogenous retinal detachment

OBJECTIVE

To investigate the effects of silicone oil (SiO) on macular thickness (MT) and subfoveal choroidal thickness (SFCT) in patients with macula-off rhegmatogenous retinal detachment (RRD) undergoing pars plana vitrectomy (PPV).

MATERIAL AND METHODS

In this prospective study, 70 eyes of 70 patients who received SiO tamponade for the treatment of macula-off RRD were treated with PPV and a 5000-cSt SiO endotamponade followed by subsequent SiO removal. MT and SFCT were measured 1 day before and 3 months after SiO removal using spectral-domain optical tomography (SD-OCT) and enhanced depth imaging optical tomography (EDI-OCT). The patients were divided into 3 groups according to the length of time that the SiO was present: group 1 (3-6 months), group 2 (6-9 months), and group 3 (9-18 months).

RESULTS

A total of 70 eyes of 70 patients with a mean age of 57.22±9.83 years (range: 30 years to 75 years) were included in the SiO (5000-cSt) study. SiO was extracted after a mean duration of 8.67±5.33 months (range, 3-18 months) after PPV. In the 1st group, BCVA increased from 1.83±0.32 log MAR before PPV to 0.85±0.41 log MAR at 3 months after silicone removal (P<0.001). In the 2nd group, BCVA increased from 1.76±0.38 log MAR before PPV to 0.86±0.48 log MAR at 3 months after silicone removal (P<0.001). In the 3rd group, BCVA increased from 1.89±0.28 log MAR before PPV to 1.08±0.63 log MAR at 3 months after SiO removal (P=0.001). There was no statistically significant change in MT in the difference values of each group. As the length of SiO presence in the eye increased, significant thinning was observed on measurement of SFCT. Differences in the SFCT values were -14.91μm, -18.76μm, and -51.50μm in groups 1, 2, and 3 respectively (P=0.004).

CONCLUSIONS

A significant decrease in macular and choroidal thicknesses after SiO removal was observed. Presence of SiO endotamponade for 9 months was associated with subfoveal choroidal thinning and decreased final visual acuity in eyes undergoing RRD surgery. SD-OCT and EDI-OCT may be recommended for the treatment and follow-up of patients with complications caused by the use of SiO tamponade.

Evaluation of blood flow on optic nerve head after pattern scan and conventional laser panretinal photocoagulation

To evaluate the changes in the blood flow on retina and the optic nerve head (ONH) after conventional laser treatment and to compare it to that after patterned scanning laser (PASCAL) treatment in patients with severe nonproliferative diabetic retinopathy (S-NPDR).In this prospective, cross-sectional study, the blood flow on retina and the ONH was assessed by laser speckle flowgraphy using the mean blur rate (MBR) in 39 eyes with S-NPDR before, 1, 4, 8, 12 weeks after panretinal photocoagulation (PRP). Of 39 eyes, 17eyes with 17 patients treated by conventional laser and 22 eyes with 22 patients treated by PASCAL.The mean age was 55.5 ± 11.5 years in the conventional laser group, 55.6 ± 11.8 years in the PASCAL group. The MBR-vessel, which can be dominantly expressed as retinal blood flow, was significantly reduced after PRP treated by conventional laser (P < .001), but did not change after PRP treated by PASCAL. The ratio of MBR-vessel to the baseline was significantly lower in the conventional laser group only at Week 1 (P = .045). The MBR-tissue, which can be dominantly expressed as the ONH blood flow, did not significantly change after PRP in the both group. The multiple stepwise regression analysis revealed that the laser burns was an independent factor significantly correlated with the ratio of MBR-vessel at Week 1 to the baseline (β = -0.550, P = .012).The retinal blood flow was significantly reduced during the 12 weeks only after completion of PRP by conventional laser treatment. Our results indicate that short pulse on PRP treatment performed by the PASCAL would not significantly reduce the retinal blood flow.

Changes in choriocapillaris and retinal morphology after laser photocoagulation by OCT angiography: A case report

RATIONALE

Earlier studies have shown that laser photocoagulation treatments are associated with good long-term visual acuity in most patients with severe nonproliferative diabetic retinopathy (S-NPDR). Histopathologic studies of autopsied eyes have demonstrated defects in the choriocapillaris beneath the retinal laser lesions secondary to photocoagulation for S-NPDR. These lesions have been observed to expand centrifugally over time especially in the posterior pole, and the atrophy of the retinal pigment epithelium (RPE) can be significantly enlarged. There are, however, limited studies detailing the in vivo changes that occur in the RPE and choriocapillaris following laser photocoagulation.

PATIENT CONCERNS

A 46-year-old woman presented with visual disturbances in both eyes.

DIAGNOSES

Fundus examinations showed many retinal hemorrhages and soft exudates in the four quadrants due to S-NPDR.

INTERVENTIONS

Laser photocoagulations with a 532-nm wavelength argon laser with power of 170 to 230 mW and spot size of 200 μm were performed to treat the S-NPDR. The changes in the choriocapillaris and retinal vasculature were followed by optical coherence tomography (OCT) angiography.

OUTCOMES

The choriocapillaris beneath the laser spots was disrupted from 1 hour following the photocoagulation but it was restored at week 2. The choriocapillaris appeared almost normal at some laser spots, but they were still some spots that were altered at 1 year. The outer retina and RPE were disrupted beneath the laser spots at 1 year. On the contrary, there were no visible retinal vascular changes in the superficial and deep plexuses of retinal vasculature determined by OCT angiography with manual and automated segmentation.

LESSONS

The choriocapillaris in human eyes can recover after laser photocoagulation although the outer retina and RPE remain disrupted and do not recover.

Less Expansion of Short-Pulse Laser Scars in Panretinal Photocoagulation for Diabetic Retinopathy

Purpose

To compare the expansion rates of laser photocoagulation scars between the conventional laser and short-pulse laser using fundus autofluorescence (FAF).

Methods

Retrospective chart review. Conventional laser was performed on 6 eyes of 6 patients, and short-pulse laser was performed on 11 eyes of 8 patients with diabetic retinopathy. FAF images were obtained by Optos® 200Tx (Optos, Dunfermline, Scotland, UK) at 1, 3, 6, and 12 months after treatment. The average area of 20 photocoagulation scars was measured by using ImageJ software. The expansion rates were calculated from the proportion of the averaged area against the optic disc area. Regression of retinopathy and central macular thickness were also evaluated.

Results

The expansion rates of the conventional laser scars compared with the size at 1 month after treatment were 1.12 ± 0.08 (3 M), 1.27 ± 0.12 (6 M), and 1.39 ± 0.11 (12 M). The expansion rates of the short-pulse laser scars were 1.04 ± 0.05 (3 M), 1.09 ± 0.04 (6 M), and 1.13 ± 0.05 (12 M). The expansion rates of the short-pulse laser were significantly lower than those of the conventional laser (p < 0.01).

Conclusion

FAF images were useful to evaluate the changes in the photocoagulation scar sizes. The scars with the short-pulse laser showed lower expansion rates than those of the conventional laser.

Swept source optical coherence tomography-angiography of choroid in choroidal hemangioma before and after laser photocoagulation

Swept source optical coherence tomography-angiography (OCT-angiography) gives us a unique opportunity to study the vasculature of choroidal lesions in vivo. We describe the OCT angiographic characteristics of circumscribed choroidal hemangioma before and after laser photocoagulation. Medium-sized choroidal vessels/vessels on the tumor surface become predominantly visible after laser photocoagulation due to laser-induced damage to the overlying choriocapillaris. OCT-angiography adds a new dimension to in vivo analysis of vascular changes in choroid due to choroidal tumors and their response to therapy.

Effects of photocoagulation on ocular blood flow in patients with severe non-proliferative diabetic retinopathy

Purpose

To investigate ocular blood flow and correlations between ocular blood flow and variables in patients with severe non-proliferative diabetic retinopathy (S-NPDR) following panretinal photocoagulation (PRP).

Methods

In this retrospective, cross-sectional study, the blood flow on the optic nerve head (ONH) and choroid was assessed with laser speckle flowgraphy (LSFG) using the mean blur rate (MBR) in 76 eyes of 76 patients with S-NPDR who underwent PRP, 39 eyes of 39 patients with S-NPDR who did not undergo PRP, and 71 eyes of 71 normal subjects. The correlation between MBR and variables, including visual acuity (VA) and choroidal area determined by binarization method, was analyzed.

Results

The mean age was 62.9 ± 11.9 years in the S-NPDR with PRP eyes, 55.6 ± 11.4 years in the S-NPDR without PRP eyes, and 60.3 ± 11.1 years in the normal subject eyes. The ONH MBR in vessel and tissue areas and the choroidal MBR were significantly lower in the S-NDR with PRP group than in the other groups (p < 0.001, p < 0.001, and p < 0.001, respectively). The luminal and the stromal areas were significantly smaller in the S-NDR with PRP group than in the other groups (p < 0.001 and p < 0.001, respectively). LogMAR best corrected visual acuity (BCVA) exhibited significant negative correlation with the ONH MBR in vessel (r = −0.386, p < 0.001), tissue (r = −0.348, p < 0.001), and the choroid MBR (r = −0.339, p = 0.002) in the S-NDR with PRP group. Stepwise multiple regression analysis demonstrated that BCVA was a common independent factor associated with the ONH MBR in vessel, tissue, and the choroidal MBR in the S-NDR with PRP group.

Conclusions

ONH and choroid MBR in addition to choroidal component, including the luminal area, were significantly lower in eyes of patients with S-NPDR after PRP compared with no PRP and normal subjects group. This could suggest that the significantly reduced ocular blood flow in PRP-treated S-NPDR eyes correlated with long-term decreased post-PRP luminal area and visual acuity.

Choroidal thickness in diabetic retinopathy: the influence of antiangiogenic therapy

PURPOSE

To analyze the effect of anti-vascular endothelial growth factor agents (anti-VEGF) in submacular choroidal thickness (CT) of diabetic retinopathy (DR) patients.

METHODS

Cross-sectional study, which included 25 DR patients (50 eyes) divided in 2 groups, according to DR stage and previous treatments: nonproliferative DR and diffuse diabetic macular edema in both eyes, submitted to macular laser in both eyes and anti-VEGF injection only in 1 eye (nonproliferative diabetic retinopathy + diabetic macular edema group, n = 11); and proliferative DR in both eyes, treated with panretinal photocoagulation in both eyes and anti-VEGF injection only in 1 eye (proliferative diabetic retinopathy group, n = 14). In the study visit, all patients underwent optical coherence tomography with enhanced depth imaging protocol. Choroidal segmentation was performed manually. The medium CT in central macular area (CCT) and the CT in centrofoveal B-scan were obtained automatically.

RESULTS

The 25 eyes treated with anti-VEGF showed a reduction on CCT (P = 0.002) and subfoveal CT (P = 0.004), compared with the fellow eyes treated with laser only. Independent evaluation of PDR group revealed similar results (CCT, P = 0.02; subfoveal CT, P = 0.03). In nonproliferative diabetic retinopathy + diabetic macular edema group, CCT was also significantly thinner in eyes treated with anti-VEGF (P = 0.04). A correlation between the number of injections and a thinner CT was found in this group (P = 0.03) and in the evaluation of all eyes together (P = 0.03).

CONCLUSION

Diabetic eyes treated with anti-VEGF agents have reduced CT.

Changes of choroidal thickness after treatment for diabetic retinopathy

PURPOSE

To investigate the choroidal thickness changes after intravitreal bevacizumab injection (IVB), panretinal photocoagulation (PRP) or both for diabetic retinopathy treatment.

MATERIALS AND METHODS

The study included 31 eyes (31 patients) in the IVB group, 35 eyes (35 patients) in the PRP group and 35 eyes (35 patients) in the IVB-PRP group. Enhanced depth imaging optical coherence tomography (EDI-OCT) was performed before and 1 month after each treatment to measure subfoveal and extrafoveal (500 and 1000 μm) choroidal thicknesses. The best-corrected visual acuity (BCVA) and central macular thickness (CMT) were also measured.

RESULTS

The choroidal thickness at all locations significantly decreased after treatment in all groups, but there was no significant difference in the amount of change among the three groups. The subfoveal choroidal thickness and CMT significantly decreased after treatment in the IVB and IVB-PRP groups. In the PRP group, the CMT significantly increased, while the choroidal thickness significantly decreased after treatment. The subfoveal choroidal thickness and CMT were significantly reduced after IVB, but there was no significant correlation between their changes. The BCVA was improved significantly in the IVB and IVB-PRP group, but not in the PRP group.

CONCLUSIONS

The choroidal thickness decreased after all treatments, suggesting that IVB or PRP rapidly reduced choroidal vascular permeability.

Decreased circulation in the feline choriocapillaris underlying retinal photocoagulation lesions

PURPOSE

To investigate the effects of argon laser photocoagulation on the choroidal circulation in cats.

METHODS

Three sizes of argon laser lesions designed to damage the outer retina were created in six cats: larger than 1 mm, 500 μm, and 200 μm. At least 1 month after the lesions, damage to the choroidal vasculature was studied in two ways. First, scanning laser ophthalmoscopy was used to obtain infrared reflectance (IR) photographs and indocyanine green (ICG) angiograms. Second, fluorescent microspheres (15 μm) were injected into the left ventricle. The globes were fixed, the choroid was flat mounted, and images were taken with a fluorescence microscope. Retinal histology was assessed in comparable lesions.

RESULTS

Histology showed that the inner retina was preserved, but the choroid, tapetum, and outer retina were damaged. ICG angiograms revealed choriocapillaris loss in large lesions and in some 500-μm lesions, whereas the larger vessels were preserved; in 200 μm lesions, choriocapillaris loss was not detectable. However, in all lesions, the distribution of microspheres revealed little if any choriocapillaris flow. In larger lesions, the damaged region was surrounded by an area in which the number of microspheres was higher than in the lesion but lower than in the normal retina.

CONCLUSIONS

Under lesions that destroyed photoreceptors, the choriocapillaris was also compromised, even when no change could be detected with ICG angiography. Panretinal photocoagulation is designed to increase retinal PO2 by allowing choroidal oxygen to reach the inner retina, but its effectiveness may be limited by damage to the choriocapillaris.

Fundus autofluorescence in multifocal choroiditis and panuveitis

PURPOSE

To investigate the autofluorescence findings associated with multifocal choroiditis and panuveits (MCP), a condition that has marked potential to affect the retinal pigment epithelium (RPE).

DESIGN

Observational case series.

METHODS

This is a retrospective review of consecutive patients with MCP examined in a retinal referral practice. Each patient was given a comprehensive examination including fundus photographs, angiographic studies, and autofluorescence photography with an excitation filter with the bandpass wavelengths of 535 to 585 nm and a barrier filter with a bandpass of 615 to 715 nm. Integrative analysis was performed of the ocular imaging to ascertain abnormalities caused by the disease.

RESULTS

Thirty-six eyes of 18 consecutive patients were evaluated. The mean duration of symptoms was 86.2 months and the mean visual acuity was 20/50. Of the 36 eyes, 23 had choroidal neovascularization (CNV). Chorioretinal hypoautofluorescent spots >or= 125 microns usually, but not always, had the clinically evident correlate of a punched-out scar visible by color fundus photography. Chorioretinal hypoautofluorescent spots less than 125 microns, which could number in the hundreds, typically were not visible by color fundus photography. All chorioretinal scars visible by color fundus photography were visible by autofluorescence photography. During follow-up many patients developed new clinically evident chorioretinal scars, which were presaged in earlier autofluorescence photographs. CNV had a hyperautofluorescent boundary, making it readily visible.

CONCLUSIONS

Patients with MCP have much more widespread involvement of the RPE than would be suspected by other means of imaging. Autofluorescence photography supplies information about inflammatory damage and secondary CNV in a noninvasive manner.

A chronic grey matter penumbra, lateral microvascular intussusception and venous peduncular avulsion underlie diabetic vitreous haemorrhage

The landmark publications that gave such impetus to our understanding of proliferative diabetic retinopathy are reviewed in the light of more recent reports. Briefly, confluence of small areas of capillary closure in the midperipheral and peripheral retina results in arteriovenous shunting and abnormal oxygen partial pressure gradients. These gradients embrace a chronic ischaemic penumbra that stimulates neuroglial secretion of angiogenic growth factors and upregulation of their receptors in the retinal venous endothelium and adventitia. The blood shunting produces biomechanical stresses within the veins and induces microvascular intussusception near arteriovenous crossings, giving way to neovascular outgrowths and/or segmental venous lesions (such as omega loops and coils) that penetrate the inner limiting lamina. The lamellar collagenous matrix of the vitreous cortex is then exploited for integrin-dependent rete expansion along chemotactic gradients. During posterior vitreous detachment, haemorrhaging takes place from the arterialised veins as venous neovascular peduncles are avulsed.