Calculations of micropulse mode parameters regarding the age and type of appearance by Fitzpatrick scale for selective micropulse individual retinal therapy (SMIRT) on serial lasers

Purpose: to develop formulas for selecting parameters for each patient regarding their age and type of appearance by the Fitzpatrick scale. To obtain the formulas after testing the selective micropulse mode by autofluorescent (AF) results would allow to treat patients using the technology of selective micropulse individual retinal therapy (SMIRT) without preliminary testing on serial laser systems. Materials and methods : 97 patients with acute central serous chorioretinopathy, aged 30–65, with type 1 to type 4 appearance by the Fitzpatrick scale were enrolled in the study. The obtained results after the testing of selective micropulse mode (spot diameter – 100 microns, micropulse duration 50–150 μsec, duty cycle – 0.5–5 %, pulse packet duration – from 10 to 50 ms (1–5 pulses per packet), power –1–2 W) were analyzed. Laser system Iridex IQ 577 was used in the trial. For each laser spot, the probability of damage detection (PDD) was calculated with shortwave AF (488 nm) data. Results. On analyzing 4685 spots by AF findings, PDD logistic regression function was constructed using the likelihood maximization method on a training sample depending on micropulse mode parameters, age and type of appearance by Fitzpatrick scale. The resulting formula was inverted to predict the required power, pulse duration, and number of pulses to achieve the required PDD level. Errors in the logistic regression coefficients were obtained by bootstrapping. The regression quality was assessed using Pearson’s chi-squared test. While comparing the ogistic function and computer modeling, it has been shown that age and type of appearance are key personal characteristics which must be taken into account when selecting parameters of micropulse mode treatment. Conclusion. The authors have developed formulas for selecting parameters of selective micropulse mode regarding the patient’s age and type of appearance by Fitzpatrick scale without preliminary testing for treatment with SMIRT technique on serial laser systems.