Barely visible 10-millisecond pascal laser photocoagulation for diabetic macular edema: observations of clinical effect and burn localization

Short-pulse laser plus subthreshold diffuse laser for serous retinal detachment in dome-shaped macula

BACKGROUND

First described by Gaucher and associates in 2008, dome-shaped macula (DSM) is an anterior convex protrusion of the macula visible on OCT (optical coherence tomography). Visual impairment in DSM results mainly from sub-foveal serous retinal detachment (SRD). Herein, this original study from retrospective data analysis evaluate the anatomical and functional effects of Pascal® short-pulse (SP) laser plus endpoint management (EpM) subthreshold diffuse laser (SDL) in patients with SRD due to DSM.

METHODS

This retrospective study included seven consecutive patients (eight eyes) with SRD secondary to dome-shaped macula who underwent a comprehensive ophthalmological evaluation including logMAR BCVA, slit-lamp biomicroscopy, indirect ophthalmoscopy, and spectral-domain optical coherence tomography (SD-OCT) (Spectralis; Heidelberg Engineering, Germany) before combined Pascal® SP laser plus EpM-SDL with 1 to 6 month intervals, postoperatively, with a mean ± standard error (SE) follow-up time of 12.92 ± 1.34 months.

RESULTS

Eight eyes from seven patients were analyzed in this study. At baseline, mean BCVA (LogMAR) ± standard error (SE) and mean CST (central subfield thickness)(µm) ± SE were 0.6125 ± 0.14 and 412.50 ± 24.65, respectively. After a mean follow-up time of 12.92 ± 1.34 months, mean CST (µm) ± SE and BCVA (LogMAR) ± SE were 294.75 ± 19.68 (p = 0.0078) and 0.4537 ± 0.12 (p = 0.0313), respectively. A statistically significant reduction in mean CST and an improvement in mean BCVA were noted after SRD resolution with laser therapy application. The mean serous retinal detachment resolution time (months) ± SE was 3.75 ± 1.08. No adverse events were registered, including enlargement of atrophic alterations and choroidal neovascularization.

CONCLUSIONS

The novel combined laser modality with Pascal® SP laser plus EpM-SDL treatment may induce subretinal fluid regression and BCVA improvement 1 year after treatment in DSM patients with SRD.

Pascal short-pulse plus subthreshold endpoint management laser therapy for diabetic macular edema: the "sandwich technique"

Background

Diabetic macular edema (DME) is the main cause of visual loss in diabetic patients. Despite the use of anti-VEGF therapy as first-line treatment, there are many patients whose response to treatment is poor or transient at best. Sophisticated laser techniques have emerged aiming at low-intensity retinal damage, avoiding excessive heat that causes tissue necrosis and related collateral effects.

Objective

To evaluate the effect of combined sublethal laser modalities from short-pulse duration (SPD) with endpoint management (EpM) subthreshold laser [named the “sandwich technique” (SWiT)] on central subfield thickness (CST) and best-corrected visual acuity (BCVA) in patients with DME.

Material and methods

In this consecutive retrospective study, 37 patients (37 eyes) with center-involved (CI) DME were treated with SWiT laser therapy from April 2017 to June 2021. The technique consisted of a mean number of 200 (range number 50–400) SPD laser burns OCT-guided thickened area performed on the juxta- and perifoveal area 500 µm away from the foveal center, overlapping with a mean number of 1000 (range number 800–1200) EpM laser burns focused on 6 mm macular diameter area but saving 300 µm toward the foveal center. All patients underwent ophthalmological evaluations, including BCVA and CST measurement by spectral-domain optical coherence tomography (SD-OCT), before and after SWiT laser therapy. The mean follow-up time was 19.2 months (range 2–60 months).

Results

Thirty-five out of 37 cases showed an improvement in CST and BCVA following treatment. At baseline, mean CST (µm) ± standard error (SE) and mean BCVA (logMAR) ± SE was 456.95 ± 37.00 and 0.71 ± 0.29, respectively. After a mean follow-up of 19.2 months, mean CST (µm) ± SE and BCVA (logMAR) ± SE were 272.09 ± 9.10 (p < 0.0001) and 0.54 ± 0.26 (p = 0.003), respectively. A statistically significant reduction in CST and improvement in BCVA was noted after laser therapy application. The anti-VEGF injection frequency was reduced during the mean 19.2 months of the study period.

Conclusions

The novel “sandwich” laser therapy aid reduced CST and improved BCVA in this retrospective case series. Further prospective studies are warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40942-022-00381-5.

Treatment results of nondamaging retinal laser therapy in diabetic macular edema

BACKGROUND

Subthreshold nondamaging retinal laser therapy (NRT) provides a greater safety profile than conventional laser methods, but more data is needed on the efficacy and safety of subthreshold NRT in diabetic macular edema.

PURPOSE

To evaluate the efficacy and safety of NRT for the treatment of clinically significant macular edema (CSME) that is partially responsive or resistant to intravitreal anti-vascular endothelial growth factor (anti-VEGF) treatment.

METHODS

This was a retrospective case series study. Fifty eyes of 38 diabetic patients with CSME previously treated with at least 6-monthly intravitreal bevacizumab injections with/without intravitreal Ozurdex therapy were evaluated. The patients received 577-nm yellow wavelength laser therapy with PASCAL laser system (Topcon Medical Laser Systems, Santa Clara, CA, USA). Best-corrected visual acuity (BCVA) and central subfield thickness (CST) were evaluated before and 1, 3, 6, 12 and 24 months after laser treatment.

RESULTS

Baseline mean CST was 368.06 ± 86.9 µm. The mean CST values at the 1-, 3-, 6-, 12-, and 24-month visits were 336.93 ± 79.8, 352.40 ± 113.5, 336.36 ± 109.3, 325.10 ± 104 µm, and 310.08 ± 84.7 µm, respectively. The mean CST decreased significantly at the first (p = 0.002) and second year visits (p < 0.001) when compared with pretreatment values. Although visual acuity was improved at the first year compared with baseline, this difference was not statistically significant (p = 0.03). There was no significant difference in visual acuities between pretreatment and posttreatment visits. During 24-month follow-up, while 37 eyes were treated with [mean: 5.7 ± 3.4 (1-14)] intravitreal anti-VEGF injections, 3 eyes were administered single-dose intravitreal steroids. Additional intravitreal injections were not required in 10 (20%) eyes.

CONCLUSION

NRT is effective by itself or in combination with anti-VEGF agents in diabetic macular edema that is partially responsive or resistant to previous intravitreal injections. T role in treating this disorder should be assessed in more detail with prospective controlled studies.

Laser Therapy in the Treatment of Diabetic Retinopathy and Diabetic Macular Edema

PURPOSE OF REVIEW

This review highlights indications and evidence on laser therapy in the management of diabetic retinopathy and diabetic macular edema. Particular focus is placed upon the benefits and limitations of conventional laser photocoagulation versus more modern laser photocoagulation techniques, as well as the role of laser photocoagulation in treatment of diabetic retinopathy and diabetic macular edema with the frequent utilization of pharmacologic, including anti-vascular endothelial growth factor (VEGF), therapy.

RECENT FINDINGS

Laser photocoagulation remains the gold-standard therapy for the effective, definitive treatment of PDR, and also is highly effective in the management of DME. However, numerous recent studies have demonstrated the clinical efficacy and improved functional and anatomic outcomes of combination therapy with pharmacologic treatment. Continuing innovations in laser technology and improved understanding of laser-retinal interactions and pathophysiology demonstrate that laser therapy will continue to play a critical role in the treatment of diabetic retinopathy and diabetic macular edema for many years to come.

Diabetic retinopathy and diabetic macular oedema pathways and management: UK Consensus Working Group

The management of diabetic retinopathy (DR) has evolved considerably over the past decade, with the availability of new technologies (diagnostic and therapeutic). As such, the existing Royal College of Ophthalmologists DR Guidelines (2013) are outdated, and to the best of our knowledge are not under revision at present. Furthermore, there are no other UK guidelines covering all available treatments, and there seems to be significant variation around the UK in the management of diabetic macular oedema (DMO). This manuscript provides a summary of reviews the pathogenesis of DR and DMO, including role of vascular endothelial growth factor (VEGF) and non-VEGF cytokines, clinical grading/classification of DMO vis a vis current terminology (of centre-involving [CI-DMO], or non-centre involving [nCI-DMO], systemic risks and their management). The excellent UK DR Screening (DRS) service has continued to evolve and remains world-leading. However, challenges remain, as there are significant variations in equipment used, and reproducible standards of DMO screening nationally. The interphase between DRS and the hospital eye service can only be strengthened with further improvements. The role of modern technology including optical coherence tomography (OCT) and wide-field imaging, and working practices including virtual clinics and their potential in increasing clinic capacity and improving patient experiences and outcomes are discussed. Similarly, potential roles of home monitoring in diabetic eyes in the future are explored. The role of pharmacological (intravitreal injections [IVT] of anti-VEGFs and steroids) and laser therapies are summarised. Generally, IVT anti-VEGF are offered as first line pharmacologic therapy. As requirements of diabetic patients in particular patient groups may vary, including pregnant women, children, and persons with learning difficulties, it is important that DR management is personalised in such particular patient groups. First choice therapy needs to be individualised in these cases and may be intravitreal steroids rather than the standard choice of anti-VEGF agents. Some of these, but not all, are discussed in this document.

Single session of pattern scanning laser versus multiple sessions of conventional laser for panretinal photocoagulation in diabetic retinopathy: Efficacy, safety and painfulness

Purpose

To evaluate the clinical efficiency, safety and painfulness of retinal laser photocoagulation employing a pattern scanning laser system Pascal given in a single-session versus conventional laser multiple-session treatment of the same patient with diabetic retinopathy during 12-month follow-up.

Methods

The cohort included 60 eyes in 30 patients treated at the Ophthalmology Clinic, Faculty Hospital Ostrava, from 2008 to 2013. Panretinal laser coagulation was performed on one eye using the multispot panretinal photocoagulation given in a single-session system Pascal (OptiMedica, Santa Clara, California). On the other eye laser treatment was carried out by the classic conventional multiple-session method.

Results

The performance of Pascal panretinal laser coagulation was evaluated as significantly less painful (visual scale of pain was 3.28 ± 1.9) than the performance of conventional photocoagulation (visual scale of pain was 3.93 ± 1.88) with similar efficiency. Distribution of progression of diabetic retinopathy in individual patients was very similar in both groups under comparison, and was strictly paired in 24 of the 30 patients at the end of 1-year follow-up.

Conclusion

Laser photocoagulation of the retina with the use of short impulse durations and patterns in patients with diabetic retinopathy given in one session possesses similar efficiency to that of conventional retinal photocoagulation in multiple sessions. The single session treatment is also better tolerated by patients and in addition to this, it shortens the performance of the whole therapy, which potentially saves considerable funds of all subjects participating in the process of treatment.

Trial registration

ClinicalTrials.gov NCT03672656.

In Vivo Study of the Long Term Structural Changes Induced by Macular Argon Laser

PURPOSE

To assess the long-term structural changes induced by macular argon laser using en face optical coherence tomography (OCT).

MATERIALS AND METHODS

We reviewed the charts and OCT pictures of patients who had undergone macular laser for diabetic macular edema at least four years ago. Clinical parameters were recorded for each eye, including laser settings. We obtained En face pictures, that were flattened at the RPE (retinal pigment epithelium) plane. We then measured the retinal surface covered by laser marks and the maximal diameter of the largest identified lesion at this plane.  The most superficial level of neurosensory retinal damage as well as the total retinal thickness at this location were measured from the RPE. We also measured the distance between the RPE and the deeper plane at which laser marks were detected.

RESULTS

21 eyes of 16-patients were analyzed. The mean age (±SD) was 61.7 ± 15.5 years. Patients had undergone macular laser 6.5 ± 2.8 years prior to entering our study.  In 16 eyes the most superficial laser marks were detected at the inner plexiform/inner nuclear layers. The level of neurosensory retinal damage was 159 ± 48 microns over the RPE (62.6 ± 18.3% of the retinal thickness). The deepest level at which laser marks were retrieved was 125 ± 110 microns below the RPE.  The growth of laser marks was correlated to time (Pearson's correlation coefficient = 0.23; p = 0.1).

CONCLUSIONS

Argon laser marks gradually expand in the horizontal and vertical axes. The damage induced by argon laser in the neurosensory retina often reaches inner layers.

Recent developments in laser treatment of diabetic retinopathy

Laser photocoagulation has been the mainstay of diabetic retinopathy treatment since its development in mid-20^th century. With the advent of antivascular endothelial growth factor therapy, the role of laser therapy appeared to be diminished, however many advances in laser technology have been developed since. This review will describe recent advances in laser treatment of diabetic retinopathy including pattern scan laser, short-pulse duration and a reduced fluence laser, and navigated laser system for proliferative diabetic retinopathy and macular edema.

Clinical relevance of quantified fundus autofluorescence in diabetic macular oedema

PURPOSE

To quantify the signal intensity of fundus autofluorescence (FAF) and evaluate its association with visual function and optical coherence tomography (OCT) findings in diabetic macular oedema (DMO).

METHODS

We reviewed 103 eyes of 78 patients with DMO and 30 eyes of 22 patients without DMO. FAF images were acquired using Heidelberg Retina Angiograph 2, and the signal levels of FAF in the individual subfields of the Early Treatment Diabetic Retinopathy Study grid were measured. We evaluated the association between quantified FAF and the logMAR VA and OCT findings.

RESULTS

One hundred and three eyes with DMO had lower FAF signal intensity levels in the parafoveal subfields compared with 30 eyes without DMO. The autofluorescence intensity in the parafoveal subfields was associated negatively with logMAR VA and the retinal thickness in the corresponding subfields. The autofluorescence levels in the parafoveal subfield, except the nasal subfield, were lower in eyes with autofluorescent cystoid spaces in the corresponding subfield than in those without autofluorescent cystoid spaces. The autofluorescence level in the central subfield was related to foveal cystoid spaces but not logMAR VA or retinal thickness in the corresponding area.

CONCLUSIONS

Quantified FAF in the parafovea has diagnostic significance and is clinically relevant in DMO.

New treatments for diabetic retinopathy

Diabetic retinopathy is the major cause of vision loss in middle-aged adults. Alteration of the blood-retinal barrier (BRB) is the hallmark of diabetic retinopathy and, subsequently, hypoxia may result in retinal neovascularization. Tight control of systemic factors such as blood glucose, blood pressure and blood lipids is essential in the management of this disease. Vascular endothelial growth factor (VEGF) is one of the most important factors responsible for alteration of the BRB. The introduction of anti-VEGF agents has revolutionized the therapeutic strategies used in people with diabetic retinopathy, and the use of laser therapy has been modified. In the present article, we examine the clinical features and pathophysiology of diabetic retinopathy and review the current status of new treatment recommendations for this disease, and also explore some possible future therapies.

Comprehensive detection, grading, and growth behavior evaluation of subthreshold and low intensity photocoagulation lesions by optical coherence tomographic and infrared image analysis

Purpose. To correlate the long-term clinical effect of photocoagulation lesions after 6 months, as measured by their retinal damage size, to exposure parameters. We used optical coherence tomographic (OCT)-based lesion classes in order to detect and assess clinically invisible and mild lesions. Methods. In this prospective study, 488 photocoagulation lesions were imaged in 20 patients. We varied irradiation diameters (100/300 µm), exposure-times (20–200 ms), and power. Intensities were classified in OCT images after one hour, and we evaluated OCT and infrared (IR) images over six months after exposure. Results. For six consecutive OCT-based lesion classes, the following parameters increased with the class: ophthalmoscopic, OCT and IR visibility rate, fundus and OCT diameter, and IR area, but not irradiation power. OCT diameters correlated with exposure-time, irradiation diameter, and OCT class. OCT classes discriminated the largest bandwidth of OCT diameters. Conclusion. OCT classes represent objective and valid endpoints of photocoagulation intensity even for “subthreshold” intensities. They are suitable to calculate the treated retinal area. As the area is critical for treatment efficacy, OCT classes are useful to define treatment intensity, calculate necessary lesion numbers, and universally categorize lesions in clinical studies.

High-resolution in vivo imaging of regimes of laser damage to the primate retina

Purpose. To investigate fundamental mechanisms of regimes of laser induced damage to the retina and the morphological changes associated with the damage response. Methods. Varying grades of photothermal, photochemical, and photomechanical retinal laser damage were produced in eyes of eight cynomolgus monkeys. An adaptive optics confocal scanning laser ophthalmoscope and spectral domain optical coherence tomographer were combined to simultaneously collect complementary in vivo images of retinal laser damage during and following exposure. Baseline color fundus photography was performed to complement high-resolution imaging. Monkeys were perfused with 10% buffered formalin and eyes were enucleated for histological analysis. Results. Laser energies for visible retinal damage in this study were consistent with previously reported damage thresholds. Lesions were identified in OCT images that were not visible in direct ophthalmoscopic examination or fundus photos. Unique diagnostic characteristics, specific to each damage regime, were identified and associated with shape and localization of lesions to specific retinal layers. Previously undocumented retinal healing response to blue continuous wave laser exposure was recorded through a novel experimental methodology. Conclusion. This study revealed increased sensitivity of lesion detection and improved specificity to the laser of origin utilizing high-resolution imaging when compared to traditional ophthalmic imaging techniques in the retina.

Retinopathy in diabetes

With the incidence, and prevalence of diabetes mellitus increasing worldwide, diabetic retinopathy is expected to reach epidemic proportions. The aim of this chapter is to introduce diabetic retinopathy, a leading cause of blindness in people of the working age. The clinical course of retinopathy, anatomical changes, its pathogenesis and current treatment are described, followed by an overview of the emerging drug therapies for the potential treatment of this sight-threatening complication of diabetes.

Effects of coagulation on the autofluorescence pattern of ARPE-19 cells: an in vitro study

OBJECTIVE

Changes in fundus autofluorescence (AF) are observed in various retinal disorders. Lipofuscin accumulation within the retinal pigment epithelium (RPE) is a source of fundus AF (FAF); however, the causes of short-term increases in FAF observed in inflammatory conditions or after laser treatment are unknown. Here, we describe an RPE cell culture model that is useful for investigations of FAF.

METHODS

ARPE-19 cells were cultured in 2-well chamber slides. Cells were exposed to isolated rabbit photoreceptor outer segments (POS) to mimic in vivo phagocytic activity. The AF of RPE cells exposed to POS was measured before and after focal coagulation of the cultures. AF was measured over a period of 4 weeks. Cell lysates were examined by two-dimensional (2D) gel electrophoresis and mass spectrometry analysis.

RESULTS

The exposure of ARPE cells to POS did not lead to increased AF; however, after coagulation, cells exposed to POS showed a statistically significant increase in AF (p < 0.05). 2D electrophoresis of the cell lysates revealed changes in 3 proteins. One of these proteins, identified by mass spectrometry as ezrin-radixin-moesin-binding phosphoprotein 50, was reduced in the coagulated cell population.

CONCLUSIONS

We have established an in vitro model of RPE cells in culture that can be used to evaluate the development of AF and changes in cellular proteins that accompany laser photocoagulation.

Long-term safety, high-resolution imaging, and tissue temperature modeling of subvisible diode micropulse photocoagulation for retinovascular macular edema

PURPOSE

To determine the long-term safety of high-density subvisible diode micropulse photocoagulation (810 nm), compare the clinical findings with computational modeling of tissue hyperthermia and to report results for a subset of eyes treated for diabetic macular edema (ME) documented pre- and postoperatively by spectral-domain optical coherence tomography.

METHOD

All eyes treated for ME from diabetic retinopathy (diabetic ME) and branch retinal vein occlusion between April 2000 and January 2010 were reviewed for subvisible diode micropulse laser-induced retinal damage. Therapeutic outcomes were reviewed for a subgroup treated for diabetic ME with pre- and postoperative spectral-domain optical coherence tomography. Laser-induced retinal thermal effects were modeled computationally using Arrhenius formalism.

RESULTS

A total of 252 eyes (212 diabetic ME, 40 branch retinal vein occlusion) of 181 patients qualified. None of the 168 eyes treated at irradiance <350 W/cm2 and 7 of 84 eyes at ≥ 590 W/cm2 had retinal damage (P = 0.0001) (follow-up 3-120 months, median, 47). Sixty-two eyes of 48 patients treated for diabetic ME with pre- and postoperative spectral-domain optical coherence tomography with median 12 months follow-up had no retinal injury by infrared, red-free, or fundus autofluorescence photos; fluorescein angiography or indocyanine green angiography; or spectral-domain optical coherence tomography. Central foveal thickness (P = 0.04) and maximum macular thickness decreased (P < 0.0001). Modeling of retinal hyperthermia demonstrates that the sublethal clinical regimen corresponds to Arrhenius integral >0.05, while damage is likely to occur if it exceeds 1.

CONCLUSION

Subvisible diode micropulse can effectively treat retinovascular ME without laser-induced retinal damage, consistent with Arrhenius modeling of pulsed hyperthermia.

The impact of pulse duration and burn grade on size of retinal photocoagulation lesion: implications for pattern density

PURPOSE

Shorter pulses used in pattern scanning photocoagulation (10-20 milliseconds [ms]) tend to produce lighter and smaller lesions than the Early Treatment Diabetic Retinopathy Study standard 100-ms exposures. Smaller lesions result in fewer complications but may potentially reduce clinical efficacy. It is worthwhile to reevaluate existing standards for the number and size of lesions needed.

METHODS

The width of the coagulated zone in patients undergoing retinal photocoagulation was measured using optical coherence tomography. Lesions of "moderate," "light," and "barely visible" clinical grades were compared for 100, 200, and 400 μm spot sizes and pulse durations of 20 ms and 100 ms.

RESULTS

To maintain the same total area as in 1,000 standard burns (100 ms, moderate) with a 400-μm beam, a larger number of 20-ms lesions are required: 1,464, 1,979, and 3,520 for moderate, light, and barely visible grades, respectively. Because of stronger relative effect of heat diffusion with a smaller beam, with 200 μm this ratio increases: 1,932, 2,783, and 5,017 lesions of 20 ms with moderate, light, and barely visible grades correspond to the area of 1,000 standard burns.

CONCLUSION

A simple formula is derived for calculation of the required spot spacing in the laser pattern for panretinal photocoagulation with various laser parameters to maintain the same total coagulated area.