Clinical Evaluation of Individualized and Navigated Microsecond Pulsing Laser for Acute Central Serous Chorioretinopathy

Development of the selective micropulse individual retinal therapy depends on age and type on the Fitzpatrick scale

PURPOSE

To develop a selective micropulse individual retinal therapy (SMIRT) based on the age and appearance type of the patient, to derive a formula for calculating power, and evaluate clinical efficacy for the treatment of central serous chorioretinopathy (CSCR).

METHODS

73 patients (aged 30-65 years) with acute CSCR and types 1-4 on the Fitzpatrick scale were divided into 2 groups. In the first group (33 patients), the testing of the micropulse mode (50 µs, 2.4%, 10 ms, 100 µm, 0.4-1.9 W) on the Navilas 577 s laser system defined as selective by computer modeling was performed. A logistic regression function based on probability damage detection (PDD) of the 1584 laser spots from power, age, and type on the Fitzpatrick scale was constructed. PDD is the probability of detecting the laser spots using the autofluorescence method. The second group was divided into 4 subgroups of 10 eyes each. Groups 2.1, 2.2, and 2.3 were treated without preliminary testing. The power for Groups 2.1, 2.2, and 2.3 was obtained with the inverse PDD function, so that PDD was 50%, 70%, and 90%, respectively. Control group 2.4 went without treatment.

RESULTS

The transmission and absorption coefficients of laser radiation of the eye depend on the age and the Fitzpatrick scale type. In Groups 2.1-2.3, complete resorption of subretinal fluid was observed 3 months after CSCR treatment in 5 (P < 0.35), 8 (P < 0.023), and 10 eyes (P < 0.0008) out of 10, respectively.

CONCLUSION

The developed SMIRT is effective for CSCR treatment with PDD 90%.

Determination of Micropulse Modes with Targeted Damage to the Retinal Pigment Epithelium Using Computer Modeling for the Development of Selective Individual Micropulse Retinal Therapy

PURPOSE

When using a serial laser system for selective impact on the retinal pigment epithelium (RPE), there is a challenge to determine the optimal range of micropulse parameters which result in targeted damage to the RPE. This study proposes a computer model that has identified the optimal parameters to be applied.

METHODS

This study was conducted on 18 patients who were diagnosed with acute central serous chorioretinopathy and transparent optical media, aged 35 to 46 years old, and type 2 and 3 on the Fitzpatrick scale. Testing of the micropulse mode was performed on the Navilas 577s laser system; 864 spots were analyzed in total. Considering the probability of damage visualization at different laser power, the computer simulation of tissue heating and protein denaturation was performed to determine the micropulse modes which resulted in selective damage to the RPE.

RESULTS

The computer model parameter ΔE = 3.34 × 10⁵ J/mol was determined from fitting the model predictions to the autofluorescence test results. The micropulse modes with a micropulse duration of 50-100 µs, duty cycle 2.4-4.8%, 10 ms-pulse envelope (5 micropulses), and spot diameter of 100 µm have efficiency and selectivity above 67% and correspond to the optimal therapeutic window for targeted RPE damage at a certain power. Increasing the micropulse duration, number of micropulses, and duty cycle leads to a decrease in the selective effect on the RPE and higher damage to adjacent tissues.

CONCLUSION

The concepts of efficiency and selectivity have been introduced to quantify the amount of damage caused. The optimal range of micropulse parameters which result in effective and selective damage on the RPE has been determined for the Navilas 577s laser system. The proposed method can be used for any other serial laser system. A comparison of the different micropulse modes, as well as the CW modes, has been performed.

Influence of Retinal Microsecond Pulse Laser Treatment in Central Serous Chorioretinopathy: A Short-Term Optical Coherence Tomography Angiography Study

Background: Central serous chorioretinopathy (CSC) is a common macular condition characterized by detachment of the neuroretina and is a frequent cause of central vision loss in adults. Among the various therapeutic strategies, subthreshold microsecond pulsed laser (SML) treatment has become a useful option. Despite the suggested involvement of choroidal circulatory disturbances in CSC, the effects of this treatment on macular microperfusion have not been fully evaluated yet. Herein, we report the impact of SML on retinal and choroidal microvascular flow using non-invasive optical coherence tomography (OCT) angiography (OCTA). Methods: In this study, CSC patients with persistent subretinal fluid (SRF) with or without secondary choroidal neovascularization (CNV) were included (referred to as the pachychoroid neovasculopathy (PNV) group and the CSC group, respectively). SML was conducted using a yellow (577 nm) laser with a duty cycle of 10%, spot size of 200 µm and duration of 200 ms. Best corrected visual acuity (BCVA) as well as OCT and OCTA images were evaluated at baseline and 4 weeks after SML. OCTA parameters of interest included full retinal perfusion (FRP), choriocapillaris perfusion (CCP), Sattler’s layer perfusion (SLP), and Haller’s layer perfusion (HLP), which were evaluated longitudinally and compared to unaffected fellow eyes. Results: 27 affected eyes and 17 fellow eyes from 27 patients were included. Before treatment, central retinal thickness (CRT) and subfoveal choroidal thickness (SFCT) of affected eyes were significantly larger than in fellow eyes. Four weeks after SML, CRT decreased significantly, whereas perfusion parameters did not change. In subgroup analyses, the CSC group showed a significant decrease in SFCT, whereas the PNV group did not despite the decrease in CRT. Conclusion: Our results suggest that the SML may affect the SFCT of the CSC, but not the PNV patients at least within four weeks following treatment. This effect seems to be independent of the change in choroidal perfusion measured with OCTA.