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.

1. Volodin P.L., Ivanova E.V. Clinical evaluation of individualized and navigated microsecond pulsing laser for acute central serous chorioretinopathy. Ophthalmic Surgery Lasers and Imaging Retina. 2020; 51: 512–520. DOI: 10.3928/23258160-20200831-06

2. Roider J., Brinkmann R., Wirbelauer C., Laqua H., Birngruber R. Subthreshold (retinal pigment epithelium) photocoagulation in macular diseases: a pilot study. Br J Ophthalmol. 2000; (1): 40–47. doi: 10.1136/bjo.84.1.40

3. Kachalina G.F., Zheltov G.I., Ivanova Е.V. Modern approaches to the use of micropulse mode in the treatment of diseases of the central zone of the retina. Tavricheskiy Medico-biological Vestnik. 2012; 15(3;3): 225–227 (In Russ.).

4. Takhchidi K.P., Kachalina G.F., Zheltov G.I., Ivanova Е.V. New technique of rehabilitation of visual function based on selective infl uence of short laser pulses on retinal pigment epithelium. Ophthalmology in Belarus. 2010; 4(07): 79–83 (In Russ.).

5. Brinkmann R., Birngruber R. Selective Retina Therapy (SRT). Z Med Phys. 2007; 17(1): 6–22. DOI: 10.1016/j.zemedi.2006.11.002

6. Roider R., Michaud N.A, Flotte T.J., Birngruber R. Response of the retinal pigment epithelium to selective photocoagulation. Arch Ophthalmol. 1992; 110(12): 1786–1792. DOI: 10.1001/archopht.1992.01080240126045

7. Schuele G., Rumohr M., Huettmann G., Brinkmann R. RPE damage thresholds and mechanisms for laser exposure in the microsecond-to-millisecond time regimen. Invest Ophthalmol Vis Sci. 2005; 46(2); 714–719. DOI: 10.1167/iovs.04-0136

8. Roider J., Hillenkamp F., Flotte T.J., Birngruber R. Microphotocoagulation: selective effects of repetitive short laser pulses. Proc. Nat. Acad. Sci. USA. 1993; 90: 8643–8647. DOI: 10.1073/pnas.90.18.8643

9. Seifert E., Tode J., Pielen A., Theisen-Kunde D., Framme C., Roider J., Miura Y., Birngruber R., Brinkmann R. Selective retina therapy: toward an optically controlled automatic dosing. J Biomed Opt. 2018; 23(11): 1–12. DOI: 10.1117/1.JBO.23.11.115002. PMID: 30392199.

10. Ivanova E.V., Volodin P.L., Guskov A.V. Determination of Micropulse Modes with Targeted Damage to the Retinal Pigment Epithelium Using Computer Modeling for the Development of Selective Individual Micropulse Retinal Therapy. Curr Eye Res. 2022; 47(1): 107–114. DOI: 10.1080/02713683.2021.1962360

11. Volodin P.L., Zheltov G.I., Ivanova E.V., Solomin V.A. Calibration of the parameters of the micropulse mode of the IRIDEX IQ 577 laser using computer modeling and fundus diagnostic methods. Modern technologies in ophthalmology. 2017; 1: 52–54.

12. Volodin P.L., Ivanova E.V. Computer simulation of laser action in the regime of sir micropulse and reactions of proteins chorioretinalcomplex for selective and effective action on the retinal pigment epithelium cells. Laser Medicine. 2018; 22(1): 61–65 (In Russ.). DOI: 10.37895/2071-8004-2018-22-1-61-65

13. Zheltov G.I., Glazkov V.N., Ivanova E.V. Selective effect of laser pulses on retinal pigment epithelium. Physical basics. ARS-MEDICA. 2012; 3(58): 78–85 (In Russ.).

14. Kachalina G.F., Zheltov G.I., Ivanova E.V. Optimization of operating modes of IRIS Medical IQ 577 laser for selective action onto retinal pigment epithelium. Ophthalmology Eastern Europe. 2015; 4(27): 69–77 (In Russ.).

15. Geeraets W., Williams R., Chan G., Ham W., Guerry D., Schmidt F. The relative absorption of thermal energy in retina and choroid. Invest Ophthalmol Vis Sci. 1962; 1: 340–347.

16. Fitzpatrick T.B. The validity and practicality of sun-reactive skin types I through VI. Arch Dermatol. 1988; 124(6): 869– 71. DOI: 10.1001/archderm.124.6.869

17. Sarna T., Burke J.M., Korytowski W., Rózanowska M., Skumatz C.M., Zareba A., Zareba M. Loss of Melanin From Human RPE With Aging: Possible Role of Melanin Photooxidation. Exp Eye Res. 2003; 76(1): 89–98. DOI: 10.1016/s0014-4835(02)00247-6

18. Weale R.A. Age and the transmittance of the human crystalline lens. The Journal of Physiology. 1988; 395(1): 577–587. DOI: 10.1113/jphysiol.1988.sp016935

19. Broendsted A.E., Hansen M.S., Lund-Andersen H., Sander B., Kessel L. Human lens transmission of blue light: a comparison of autofl uorescence-based and direct spectral transmission determination. Ophthalmic Res. 2011; 46(3): 118–124. DOI: 10.1159/000323576

20. Ivanova E.V., Volodin P.L. Development of the selective micropulse individual retinal therapy depends on age and type on the Fitzpatrick scale. Graefes Arch Clin Exp Ophthalmol. 2022; 261(2): 381–390. DOI: 10.1007/s00417-022-05800-9

21. Volodin P.L., Ivanova E.V., Solomin V.A. Possibilities of modern diagnostic techniques and computerdata processing using «FemtoScan» programs for reveal weak thermal injuries in cells of the retinal pigment epithelium. Laser Medicine. 2018; 22(1): 52–56 (In Russ.). DOI: 10.37895/2071-8004-2018-22-1-52-56

22. Framme C., Brinkmann R., Birngruber R., Roider J. Autofl uorescence imaging after selective RPE laser treatment in macular diseases and clinical outcome: a pilot . Br J Ophthalmol. 2002; 86(10): 1099–1106. DOI: 10.1136/bjo.86.10.1099

23. Framme C., Schüle G., Brinkmann R., Birngruber R., Roider J. Fundus Autofl uorescence After Selective RPE Laser Treatment. Ophthalmologe. 2002; 99(11): 854–60. DOI: 10.1007/s00347-002-0684-z

24. Volodin P.L., Ivanova E.V. Selective micropulse individual retinal therapy in the navigation treatment of central serous chorioretinopathy with the selection of parameters by preliminary testing. Clinical Ophthalmology. 2023; 23(3): 112–118 (In Russ.). DOI: 10.32364/2311-7729-2023-23-3-1

25. Fitzpatrick T.B. Soleil et peau. J Med Esthet. 1975; 2: 33–34.

26. Schlott K., Koinzer S., Ptaszynski L., Bever M., Baade A., Roider J., Birngruber R., Brinkmann R. Automatic temperature controlled retinal. J Biomed Opt. 2012; 17(6): 061223. DOI: 10.1117/1.JBO.17.6.061223

27. Sramek C., Paulus Y., Nomoto H., Huie P., Brown J., Palanker D. Dynamics of Retinal Photocoagulation and Rupture. J Biomed Opt. 2009; 14(3): 034007. DOI: 10.1117/1.3130282

28. Wang J., Quan Y., Dalal R., Palanker D. Comparison of continuous-wave and micropulse modulation in retinal laser therapy. Invest Ophthalmol Vis Sci. 2017; 58(11): 4722–4732. DOI: 10.1167/iovs.17-2161.