Comparative estimation of laser coagulation efficiency in macular and microphotocoagulation of high density in diabetic maculopathy treatment

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Abstract


Subthreshold microphotocoagulation leads to the development of barely visible or invisible retinal burns. It has also been shown to be effective in macular edema treatment without any side effects that are inherent to the ETDRS method (atrophy of retinal pigment epithelium and choroid and decreased retinal sensitivity). Microphotocoagulation efficacy may be increased by high-density laser applications; however, publications drawing attention to this matter are rare in modern literature.


BACKGROUND

The efficiency of laser coagulation in the treatment of diabetic maculopathy (DM) was confirmed in a multicenter randomized study, Early Treatment Diabetic Retinopathy Study (ETDRS) [1], and currently laser coagulation is the standard treatment for diabetic macular edema. However, the use of laser coagulation is associated with the development of postcoagulative atrophy of the ocular fundus tissues and the decrease in retinal sensitivity. In 1993, Roider et al. proposed microphotocoagulation (MicroPulse) for the treatment of diabetic macular edema, in which the minimum laser radiation levels close to the threshold of damage to the retina are used [2, 3]. More recent studies by Lavinsky et al. (2011) indicate an increase in the efficiency of microphotocoagulation with more compact positioning of retinal burns compared to laser coagulation [4, 6].

It is assumed that with a near-threshold (predominantly subthreshold) effect on the retina as seen with the microphotocoagulation regime, there is practically no coagulation necrosis of the photoreceptors; melanin granules in the cells of the pigment epithelium (PE) undergo thermal exposure, which has a stimulating effect on the retina PE. Therefore, very compact laser applications, practically without gaps, are permitted without the risk of developing scotomata in the visual field. This was confirmed by the data derived from threshold automated perimetry [5]. However, the damage to the retina is not visible when using near-threshold coagulation, so it is technically extremely difficult to exclude the repeated treatment of the same site of the retina. However, it is the predominantly subthreshold nature of the laser action that allows us to neglect these types of errors to significantly increase the effective area of the retina treated by up to 1000–1500 or more laser applications per treatment session without the threat of postcoagulative atrophy of the ocular fundus tissues, followed by a decrease of retinal sensitivity characteristic of traditional supra-threshold laser coagulation.

In addition to diabetic macular edema, the MicroPulse technique can be successfully used for retinal venous occlusions, Eales disease and Coats retinitis, idiopathic perifoveal telangiectasias, central serous chorioretinopathy, and other transudative maculopathies [7].

The aim of this study was to compare the efficiency of laser coagulation using the method of supra-threshold mild macular grid with green laser (λ = 0.532 μm) and predominantly subthreshold high-density microphotocoagulation with a diode laser (λ = 0.81 μm) in the macular area in patients with diabetic macular edema. The follow-up period was 4 months.

MATERIALS AND METHODS

The study included 28 patients (44 eyes) aged 54–79 years, 16 women and 12 men. Patients were divided into 2 equal comparison groups.

The first group (22 eyes) consisted of patients subjected to laser coagulation with a green Nd: YAG laser using the mild macular grid method (pulse duration 0.1 s, irradiation spot diameter 100 μm, the interval between burns was equal to burn diameter, laser emitting power corresponded to the 2nd degree of the burn brightness according to F.A. L’Esperance [1985]).

The second group (22 eyes) consisted of patients subjected to high-density microphotocoagulation with a diode laser (pulse duration 0.2 s, duty cycle 10%, irradiation spot diameter 100 μm, laser application interval is 0–1 irradiation spot diameter, the laser emitting power was selected prior to the appearance of a minimal burn after 1–2 of 10 laser actions [mainly subthreshold radiation]).

Patients in both groups underwent a standard ophthalmological examination. To assess the dynamics of macular edema, optical coherence tomography (HD-OCT Cirrus 4000 of Carl Zeiss Meditec) was used.

RESULTS AND DISCUSSION

Laser coagulation using the mild macular grid method with a green Nd: YAG laser and predominantly subthreshold microphotocoagulation with a diode laser have comparable clinical efficacy in the treatment of DM after a follow-up period of 4 months. A more pronounced regress of edema was noted at a greater thickness of the retina after laser treatment with the green laser than after microphotocoagulation (decrease in the maximal edema height by 50 μm, 31.2% versus 27.3% and by ≥ 100 μm, 13.6% versus 0%). In both comparison groups, a significant decrease in the maximum retinal height was noted after treatment (group 1: from 397 ± 56.8 to 370 ± 69 μm [p = 0.08], group 2: from 368 ± 38.6 to 345.2 ± 234.5 μm [p = 0.009]). In the short-term follow-up period, the visual acuity in the study groups was not significantly different (Figures 1, 2).

 

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Fig. 1. Photos and optical coherence tomography data before and after laser coagulation with green ND:YAG laser (0.532 μm) with the use of focal microgrid pattern. Left: before treatment, right: 4 months after treatment

 

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Fig. 2. Max edema depth dynamic pattern (4 month)

 

CONCLUSION

Mainly subthreshold high-density microphotocoagulation with diode laser and laser coagulation with green laser using the mild macular grid method have comparable efficiency in the treatment of diabetic macular edema. More studies are required to improve the implementation method and increase the efficiency of microphotocoagulation in clinical practice.

Tat’yana V Kotsur

Author for correspondence.
tatiana781@yandex.ru
Eye Microsurgery named after academician S.N. Fyodorov, St Petersburg Branch
Russian Federation

MD, PhD, ophthalmologist. Laser microsurgery and fluorescent angiography department

Aleksandr S Izmaylov

061@mail.ru
Eye Microsurgery named after academician S.N. Fyodorov, St Petersburg Branch
Russian Federation

doctor of medical science, MD of highest qualification, head of laser surgery department

  • ETDRS report number 19. Early treatment diabetic retinopathy study group. Focal photocoagulation treatment of diabetic macular edema. Relationship of treatment effect to fluorescent angiographic and other retinal characteristics at baseline. Arch Ophthalmol. 1995;113(9):1144-1155. doi: 10.1001/archopht.1995.01100090070025.
  • Roider J. Laser treatment of retinal diseases by subthreshould laser effects. Semin Ophthalmology. 1999;14:19-26. doi: 10.3109/08820539909056059.
  • Roider J, Michaud NA, Flotte TJ, et al. Response of the retinal pigment epithelium to selective photocoagulation. Arch Ophthalmol. 1992; 110(12):1786-1792. doi: 10.1001/archopht.1992.01080240126045.
  • Lavinsky D, et al. Randomized clinical trial evaluating mETDRS versus normal or high-density micropulse photocoagulation for Diabetic Macular Edema. Invest Ophthalmol Vis Sci. 2011;52(7):4314-4323. doi: 10.1167/iovs.10-6828.
  • Lovestam-Adrian M. Photocoagulation of diabetic macular oedema-complications and visual outcome / M. Lovestam-Adrian, E. Agardh. Acta Ophthalmol Scand. 2000;78(6):667-671. doi: 10.1034/j.1600-0420.2000.078006667.x.
  • Roider J, Michaud NA, Flotte TJ, et al. Response of the retinal pigment epithelium to selective photocoagulation. Arch Ophthalmol. 1992;110(12):1786-1792. doi: 10.1001/archopht. 1992.01080240126045.
  • Schatz H. Progressive enlargement of laser scars following grid laser photocoagulation for diffuse diabetic macular edema / H. Schatz, D. Madeira, H.R. McDonald, et al. Arch Ophthalmol.1991;109(11): 1549-1551. doi: 10.1001/archopht.1991.01080110085041.

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