Macular photocoagulation. Optimal wavelength selection

Direct Photocoagulation for Treating Microaneurysms with Hyperreflective Ring in Eyes with Refractory Macular Edema Associated with Branch Retinal Vein Occlusion

Microaneurysms (MAs) with hyperreflective rings are sometimes detected in eyes with refractory macular edema (ME) associated with branch retinal vein occlusion (BRVO) for more than 12 months after onset when examined using optical coherence tomography (OCT). We proposed that these MAs could result in refractory ME secondary to BRVO and hypothesized that OCT-guided direct photocoagulation of MAs could result in a reduction in refractory ME. Eleven eyes (from eleven different patients) with refractory ME associated with BRVO for more than 12 months following initial treatment were included. The mean number of MAs in each eye at baseline was 3.5 ± 2.0 (range, 1–8). The mean central subfield thickness, central macular volume, and parafoveal macular volume significantly decreased 6 months following initial direct photocoagulation when compared with those at baseline (baseline = 378.7 ± 61.8 μm, post-treatment = 304.2 ± 66.7 μm, p = 0.0005; baseline = 0.3 ± 0.049 mm³, post-treatment = 0.24 ± 0.053 mm³, p = 0.001; and baseline = 2.5 ± 0.14 mm³, post-treatment = 2.28 ± 0.15 mm³, p = 0.001, respectively). Moreover, the mean best-corrected visual acuity significantly improved 6 months following initial direct photocoagulation when compared with that at baseline (baseline = 0.096 ± 0.2 logarithm of the minimum angle of resolution (logMAR), post-treatment = 0.0077 ± 0.14 logMAR, p = 0.031). Direct photocoagulation could be suggested as a treatment option for refractory ME associated with BRVO in MAs with a hyperreflective ring on OCT.

Comparison of the 1-Year Visual and Anatomical Outcomes between Subthreshold Red (670 nm) and Yellow (577 nm) Micro-Pulse Laser Treatment for Diabetic Macular Edema

We investigated the efficacy and safety of red (670 nm) subthreshold micropulse laser (SMPL) treatment for diabetic macular edema (DME) and compared the 1-year treatment outcomes of red and yellow (577 nm) SMPL for DME. A medical chart review was performed in 43 consecutive eyes of 35 patients who underwent red or yellow SMPL treatment for DME and were followed up for 12 months. There were 26 and 17 eyes in the yellow and red SMPL groups, respectively. The mean best-corrected visual acuity (BCVA) was maintained throughout the follow-up period of 12 months in the yellow and red SMPL groups (p = 0.39, p = 0.70, respectively). The central retinal thickness (CRT) measured by spectral-domain optical coherence tomography (SD-OCT) was significantly decreased at 12 months from baseline in the yellow and red SMPL groups (p = 0.047, p = 0.03, respectively). Although the amount of CRT reduction in the red SMPL group was significantly greater than that in the yellow SMPL group at 8 months from baseline (p = 0.02), the significance disappeared at the final follow-up period (p = 0.44). The red SMPL maintained the BCVA in patients with center-involving DME. The mean CRT in the red SMPL group significantly decreased, and the amount of CRT reduction was equivalent to that in the yellow SMPL group.

[Transpupillary laser photocoagulation of ocular fundus: history, the present, and the future]

The present review covers the use of chorioretinal photocoagulation, which is now a popular treatment for many diseases of the ocular fundus. The review includes a detailed 50-year history of the technology with account to both Russian and foreign achievements. The current state of the field is shown through Russian and foreign literature data. A particular emphasis is placed on subthreshold, pattern, and navigated techniques. Breakthrough solutions, such as optoacoustic monitoring, that ensure high precision of the procedure, maximum saving of tissues, and high therapeutic effectiveness are described.

Green or yellow laser treatment for diabetic macular edema: exploratory assessment within the Diabetic Retinopathy Clinical Research Network

PURPOSE

Explore differences in green compared with yellow focal/grid laser treatment on functional and anatomical endpoints in eyes with diabetic macular edema.

METHODS

Data from two randomized clinical trials were evaluated for differences in visual acuity and optical coherence tomography parameters for eyes assigned to sham injection + prompt laser, ranibizumab + prompt laser, or prompt laser only: among subgroups of eyes treated exclusively and electively with either green or yellow laser.

RESULTS

In the sham injection + prompt laser group, the mean visual acuity letter score change for eyes receiving green and yellow laser treatment, respectively, was +2.4 ± 14 and +5.1 ± 13 at the 52-week visit (P = 0.06) and +2.4 ± 15 and +6.0 ± 13 at the 104-week visit (P = 0.13), with no corresponding evidence of differences in optical coherence tomography thickness. When comparing wavelength groups in the ranibizumab + prompt laser and prompt laser-only groups, meaningful differences in visual acuity and optical coherence tomography thickness were not detected at 1 year or 2 years.

CONCLUSION

A trend toward improved vision outcome with yellow laser observed in one trial was not corroborated by anatomical outcomes or by the other trial. In this study, without random assignment to different wavelengths controlling for bias and confounding, it is not possible to determine whether one wavelength is better than the other.

Characterization of microaneurysm closure after focal laser photocoagulation in diabetic macular edema

PURPOSE

To characterize microaneurysm closure following focal laser photocoagulation in diabetic macular edema (DME) using simultaneous fluorescein angiography (FA) and spectral-domain optical coherence tomography (SD-OCT).

DESIGN

Retrospective observational case series.

METHODS

Leaking microaneurysms (n = 123) were analyzed in eyes (n = 29) with nonproliferative diabetic retinopathy (NPDR) that underwent navigated focal laser photocoagulation in DME and were followed at 3, 6, and 12 months. Closure of diabetic microaneurysms was characterized in detail following focal laser using SD-OCT.

RESULTS

Closure rate of microaneurysms by both FA and SD-OCT was 69.9% (84/123), 79.7% (98/123), and 82.9% (102/123) at 3, 6, and 12 months, respectively. Microaneurysm closure rate increased at 6 and 12 months compared to 3 months (P < .003, P < .001). Over half of closed microaneurysms (45/86, 52.3%) left hyperreflective spots while the remaining half (41/86, 47.7%) disappeared without any hyperreflectivity by SD-OCT at 3 months. Hyperreflective spots decreased at 6 (36/99, 36.4%) and 12 months (17/102, 16.7%) with a concomitant increase in complete loss of reflectivity at 6 (63/99, 63.6%) and 12 months (85/102, 83.3%). Smaller outer and inner diameters and heterogeneous lumen reflectivity were positively associated with microaneurysm closure at 12 months (P < .0001, P < .001, P < .03).

CONCLUSIONS

Characterization of microaneurysms following focal laser photocoagulation resulted in hyperreflective spots and complete resolution of all reflectivity using SD-OCT. Smaller microaneurysms and those with heterogeneous lumen were positively associated with microaneurysm closure. These findings provide greater understanding of localized retinal changes following focal laser photocoagulation in DME treatment.

Therapeutic window of retinal photocoagulation with green (532-nm) and yellow (577-nm) lasers

BACKGROUND AND OBJECTIVE

The 577-nm (yellow) laser provides an alternative to the 532-nm (green) laser in retinal photocoagulation, with potential benefits in macular treatment and through ocular opacities. To assess relative risk of thermomechanical rupture of Bruch's membrane with yellow laser in photocoagulation, the therapeutic window, the ratio of threshold powers for mild coagulation and rupture, was measured.

MATERIALS AND METHODS

Retinal coagulation and rupture thresholds, visualized ophthalmoscopically, were measured with 577- and 532-nm lasers using 10- to 100-ms pulses in 34 rabbit eyes. Lesions at 1 and 7 days were assessed histologically.

RESULTS

Coagulation threshold with yellow laser was 26% lower than with green laser. The therapeutic window increased linearly with log-duration for both wavelengths with a difference in parallel-slope intercept of 0.36 ± 0.20, corresponding to 8% to 15% wider therapeutic window for yellow wavelength.

CONCLUSION

The therapeutic window of retinal photocoagulation in rabbits at 577 nm is slightly wider than at 532 nm, whereas histologically the lesions are similar.

Frequency-doubled Nd:YAG laser for the treatment of exudative diabetic maculopathy

PURPOSE

To determine the clinical efficacy of frequency-doubled Nd:YAG (FD YAG) laser for the treatment of diabetic clinically significant macular oedema (CSMO).

METHODS

A prospective pilot study was carried out on 55 eyes with CSMO. FD YAG laser exposures were applied in a focal or grid pattern. The results were evaluated by Snellen visual acuity, slit-lamp biomicroscopy, colour photography and fundus fluorescein angiography.

RESULTS

At mean review of 5.3 months, macular oedema had resolved either completely or partly in 44 (80%) eyes, was unchanged in 10 (18%) eyes and progressed in 1 (2%) eye. Visual acuity improved in 11 (20%), stabilised in 40 (73%) and deteriorated in 4 (7%) eyes.

CONCLUSION

FD YAG laser therapy is effective in the treatment of CSMO. It combines the ergonomic advantages of a solid-state laser with the benefits of its wavelength. A comparison between the clinical results of FD YAG and other lasers used in the treatment of CSMO is, however, required.

Lasers and diabetic retinopathy: the art of gentle destruction

Laser retinal photocoagulation represents the primary therapy for the potentially blinding manifestations of diabetic retinopathy. Advances in laser therapy for diabetic eye disease have arisen from the convergence of laser technology and clinical ophthalmology. In this review, the basis of laser therapy in diabetic retinopathy is discussed. Included are the clinical characteristics, classification, and pathogenetic mechanisms of diabetic retinopathy. The principles of laser technology, variety of lasers currently available for therapy, and mechanisms of laser actions on retinal target tissues are introduced. The milestone clinical trials establishing the efficacy of laser therapy and the parameters for its clinical application in diabetic retinopathy are outlined.

Lasers in ophthalmology

This article reviews the principle uses of ophthalmic lasers, providing historical background with an emphasis on new applications and areas of investigation. Ophthalmic photocoagulation was the first medical laser application and has restored or maintained vision in millions of people. More recently, photodisruption and, increasingly, ablation have gained prominence for treating a wide range of ocular pathology. The unique properties of lasers have also been harnessed for diagnostic purposes, with optical coherence tomography representing a significant improvement over existing imaging methods. Many ophthalmic applications of lasers have been developed, but the field is a dynamic one which continues to evolve along with laser technology itself.

Classification of retinal pigment epithelial detachments associated with drusen

To understand the natural history of retinal pigment epithelial (RPE) detachments (PEDs) associated with drusen, we retrospectively reviewed 125 PEDs that had not undergone laser treatment over an average follow-up period of 28 months. We identified six types of RPE detachments: pseudo-vitelliform, confluent drusen, serous, vascular, and hemorrhagic lesions as well as PEDs associated with a retinal vascular abnormality. We correlated the type of detachment with visual acuity and anatomic outcome. The poorest results were obtained for PEDs associated with neovascularization (vascular, hemorrhagic, and retinal vascular abnormality types). Eyes presenting with pseudo-vitelliform lesions or confluent drusen had the best visual prognosis and anatomic results. Obvious subretinal new vessels developed in 16 (34%) of the serous PEDs over an average follow-up period of 25 months. Subretinal neovascularization was rare in the pseudo-vitelliform and confluent drusen groups. The proposed classification system may be useful in predicting the natural course of PEDs.

Atrophic creep of the retinal pigment epithelium after focal macular photocoagulation

To determine if enlargement of laser scars occurs in nonmyopic individuals, the authors retrospectively reviewed 126 consecutive patients with age-related macular degeneration who had been successfully treated with focal macular laser photocoagulation for subretinal neovascularization. Of the 174 laser scars in the study, 122 (70%) increased in size from 50 to 1016 microns (mean, 290 microns) as determined photographically on serial examination ranging from 2 to 81 months. There was no statistically significant difference in the number of scars which increased in size among the three laser wavelengths used. Four (3%) patients lost vision as a result of the scar extending into the fovea. Enlargement of retinal pigment epithelial (RPE) atrophy after focal macular laser photocoagulation may cause significant, delayed visual loss after successful treatment of subretinal neovascularization.

Age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible severe visual loss in the United States in people over 50 years of age. The nonexudative stage includes hard drusen (associated with localized dysfunction of the retinal pigment epithelium [RPE]), soft drusen (associated with diffuse dysfunction of the RPE), and geographic (areolar) atrophy. These fundus changes may predispose the eye to develop the neovascular/exudative stages of AMD. Most patients who develop severe visual loss from AMD have this exudative stage. Treatment for AMD has been shown to be effective for only a small proportion of patients who have a well-defined choroidal neovascular membrane (CNVM) more than 200 microns from the foveal center. Even in successfully treated cases, severe visual loss is postponed only for about 18 months because of the high rate of recurrent CNVMs that extend into the fovea. Thus, despite recent breakthroughs in laser treatment for AMD, most patients who develop the exudative form of AMD will develop central visual impairment. At the present time, the only available treatments for the majority of patients who develop the exudative form of AMD are low vision aids. Investigators are currently evaluating whether treatment is effective for membranes within 200 microns of the foveal center. Future studies need to be directed toward further understanding of the pathogenesis, treatment and prevention of the blinding complications of AMD.

Dye laser photocoagulation of macular subretinal neovascularization in pathological myopia. A randomized study of three different wavelengths

The authors present a randomized study of 27 eyes affected by pathological myopia with macular subretinal neovascularization which were treated with a tunable dye laser. The effectiveness of three different wavelengths (577, 590 and 620 nm) in the direct treatment of subretinal neovascularizations was evaluated in 3 groups of 9 patients each. Statistical analysis of both visual and anatomical results did not show significant differences among the three wavelengths used.

Retinal thermal response to copper-vapor laser exposure

A thermal model has been used for the interaction of an annular laser beam of a high-repetition-rate pulsed laser (copper-vapor laser) with the retina of a rabbit. The model predicts the temperature rise at each retinal point, during and after the laser exposure, as a function of pulse energy, exposure time, and pulse repetition rate. The retinal effects for each set of treatment parameters were estimated according to the predicted temperature rise and were found to be identical with our previous experimental results. The character of the interaction between the copper-vapor laser and the retina can be pretuned by the laser pulse repetition rate to fit the requirements of various treatments, permitting multiple uses of this laser for ophthalmic treatments.

Wavelength selection in macular photocoagulation. Tissue optics, thermal effects, and laser systems

The therapeutic effects of macular photocoagulation result from focal heating of the retina and choroid. The magnitude, spatial extent, and duration of temperature increases produced by laser exposures are influenced by light scattering in intraocular and intraretinal transit; light absorption by melanin, hemoglobin, and xanthophyll in target tissues; and beam parameters, such as wavelength, spot size, and exposure duration. Tissue optics and thermodynamics provide a useful guide for selecting new laser systems of potential value in macular photocoagulation, but laser-tissue interactions and subsequent chorioretinal responses are poorly understood, and therapeutic efficacy can be established only by controlled clinical trials.

Diabetic macular edema. A review

Diabetic macular edema can be classified into a focal variety, characterized by focal leakage from microaneurysms, often with accumulation of extravascular lipoprotein in a circinate pattern around the focal leakage, and a diffuse variety, with diffuse leakage from retinal vessels often accompanied by cystoid macular changes. Laser photocoagulation is directed at microaneurysms for focal leakage and is applied in a grid pattern for diffuse leakage. Several prospective randomized clinical trials have shown that laser-treated eyes fare better than untreated eyes: there is a higher rate of modest visual improvement and a lower rate of visual deterioration in eyes treated with laser photocoagulation. In patients with diabetic macular edema, especially the diffuse variety, systemic factors also may play a pathogenic role. Fluid retention and hypertension due to cardiovascular and renal disease exacerbate retinal capillary leakage. Correction of systemic abnormalities (reduced blood pressure, diuresis) may reduce macular edema and should be included as part of the total management of patients with diabetic macular edema.

Histology of macular photocoagulation

The histology of macular photocoagulation is reviewed. This information may be helpful in selecting the best available laser for retinal vascular and choroidal disorders in the macular region, as providing an experimental method to better understand the effects of photocoagulation on retinal disease processes.

Retinal damage after argon laser iridotomy

We conducted a prospective clinical study to evaluate potential retinal damage after argon laser iridotomy in 25 eyes of 22 patients with primary chronic angle-closure glaucoma. Kinetic perimetry and ophthalmoscopy showed no detectable damage. Iridotomy required a mean of 11.4 +/- 10 joules to achieve a patent coloboma of 200 micron after one to three sessions. Dark-prone and mydriasis tests were performed one month after surgery. Pilocarpine was discontinued in all cases. Both static perimetry and fluorescein angiography of the midperiphery corresponding to the meridian of laser coloboma done six months after surgery showed focal damage. There was no damage in control tests of the same eyes in an opposite area of the retina.

Analysis of monochromatic green argon-laser treatment for age-related macular degeneration

A retrospective evaluation of 61 consecutive age-related disciform macular degeneration patients who received green argon-laser photocoagulation was done to evaluate the visual results and to search for characteristics of the presenting lesion that correlated with prognosis. For subretinal new vessels within 200 micron of the foveal avascular center, average pretreatment visual acuity was 20/80 and post-treatment 20/200. Twenty-eight percent improved, 36% stabilized, and 36% had worse acuity at last follow-up. Where new vessels were more than 200 micron from the foveal center, 36% improved, 20% stabilized, and 44% had worse acuity. The average pre- and post-treatment visual acuity for this group was 20/80. Overall, 36% required more than one treatment, and associated retinal vascular obliteration was noted in 31%. Hemorrhage over part of the neovascularization, turbid pigment epithelial detachment, and pigment epithelial detachment in the foveal avascular zone were signs that yielded the worst visual prognosis.

Krypton red laser photocoagulation for subretinal neovascularization

One hundred fifty-seven patients with subretinal neovascularization (SRN) were treated in a prospective, nonrandomized, consecutive study with the krypton red laser (KRL). The patients were analyzed with respect to age, etiology of the SRN, location of the SRN, and pre- and post-treatment visual acuity in patients with at least three months follow-up. Previous studies have not investigated KRL photocoagulation within the foveal avascular zone (FAZ). The results of this study compare favorably with other large series in which patients with SRN located outside the FAZ were treated with the argon blue-green laser (ABGL).

Important points in management of patients with choroidal neovascularization

The efficacy of argon blue-green laser treatment for extrafoveal choroidal neovascularization (CNV) in aging macular degeneration, presumed ocular histoplasmosis syndrome and idiopathic choroidal neovascularization has recently been proven by the Macular Photocoagulation Study. These results are applicable only to eyes managed according to certain principles of therapy and post-treatment follow-up. These include the use of a recent fluorescein angiogram and retrobulbar anesthetic, aiming for complete obliteration of the CNV. Meticulous post-treatment follow-up is critical. This includes daily patient monitoring of the Amsler grid, and prompt examinations if distortion is noted. Excellent quality fluorescein angiography is mandatory. This is repeated frequently and studied promptly. Residual or recurrent extrafoveal CNV requires prompt re-treatment.

Natural history of choroidal neovascularization in degenerative myopia

We studied 354 eyes with myopic chorioretinal degeneration by means of standard clinical evaluation and fluorescein angiography. The eyes were classified on the basis of the degree of chorioretinal degeneration found in the posterior pole. Lacquer cracks (breaks in Bruch's membrane) were noted in 82% of the 149 eyes with choroidal neovascular membranes (CNM) and in 96% of the 58 eyes with isolated subretinal hemorrhages. These hemorrhages were reabsorbed without adverse visual sequelae in 32 eyes that were followed; in 14 of these eyes that were followed closely, the average time of reabsorption was 6.4 weeks. Seventy eyes with CNM were followed for an average of 40.9 months. In 96% of these eyes the CNM remained stable or regressed, leaving an atrophic, nonexudative scar. This study indicates that CNM in degenerative myopia is usually self-limited.

Effects of the CW YAG Laser on the Human Iris and Retina

A CW YAG laser was used to coagulate retina and to produce an optical iridotomy in a human eye that was to be enucleated for malignant melanoma at the optic nerve head. Moderate coagulation with the CW YAG laser produced a deep choroidal reaction involving the outer portion of the retina. The inner structure of the fovea remained relatively unaffected. The nerve fiber over the coagulated vessels was unchanged. An optical iridotomy also was produced with the CW YAG. At least ten times more energy was needed to produce retinal photocoagulation with the CW YAG than is generally needed with the argon laser. Retrobulbar anesthesia should be used to prevent pain if extensive coagulation is done.

Effect of CW YAG and argon green lasers on experimentally detached retinas

We evaluated the effects of argon-green (514.5 nm) and CW neodymium YAG (1060 nm) wavelengths on experimentally detached retinas of primates. Neither laser produced damage to the sensory retina of the fovea. The argon green wavelength, which was absorbed by haemoglobin in the vessel or by extravasated red blood cells, created vasospasm and nerve fiber layer damage. The beam of the CW YAG was not absorbed by haemoglobin; therefore, no vasospasm could be produced on experimentally detached retinas.

Diabetic maculopathy. A critical review highlighting diffuse macular edema

Retinal ischemia and edema are the two major intraretinal components of diabetic maculopathy. Focal macular edema is caused by focal leakage from retinal microaneurysms and dilated capillary segments; diffuse edema is caused by leakage from diffusely dilated retinal capillaries throughout the posterior pole. Diffuse macular edema may be exacerbated by systemic factors such as cardiac or renal failure, and hypertension. It is postulated that dysfunction of the retinal pigment epithelial barrier and transport functions might contribute to the problem of diffuse macular edema. Newer techniques of laser grid photocoagulation for diffuse edema have been proposed. It is postulated that photocoagulative debridement of a disordered retinal pigment epithelium could be a mechanism of action of this treatment.

Transpupillary CW YAG laser coagulation. A comparison with argon green and krypton red lasers

The authors have developed a CW YAG laser for transpupillary coagulation. The effects of CW YAG coagulation on the retina, retinal vessels, and fovea were compared with those produced by the krypton red and argon green lasers. To produce threshold coagulative lesions in monkeys and rabbits, we needed five to ten times more energy with the CW YAG than with the krypton red or argon green lasers. Nerve fiber damage was observed only when coagulating retinal vessels with the argon green laser. At the parameters used, none of the lasers damaged the sensory retina of the fovea. The CW YAG may be used as a new mode of laser coagulation in the treatment of retinal diseases.

The effects of red krypton and green argon laser on the foveal region. A clinical and experimental study

The destruction of senile neovascular membranes in the central avascular region of the macula by argon laser is difficult and associated with complications. Yellow pigment in this region absorbs the blue component of the conventional argon laser radiation. In this study, the authors used lasers of different wavelengths: red krypton and green argon. Optical and electron microscopic studies on nonhuman primates were performed at 1 hour and 6 weeks. Maximum damage was seen at the level of the internal choroid with krypton laser and at the level of the pigment epithelium with green argon laser. A clinical and angiographic study showed that the destruction of the juxtafoveal neovascular membranes by both lasers was possible. Our clinical experience suggests that the red krypton laser offers a better alternative for treatment of neovascular membranes located near the foveola than the green argon laser.

Management of choroidal neovascularization within the foveal avascular zone in senile macular degeneration

After fluorescein angiography, central visual field testing, and photofield mapping, 94 eyes with senile macular degeneration and foveal choroidal new vessels (distance of 200 micron or less from the center of the foveal avascular zone) were treated with the monochromatic green argon laser. By the end of the follow-up period (average follow-up, 15 months), the new vessels were closed in 88 eyes and visual acuity was stabilized or improved in 70 eyes. These 70 eyes included 68 of 80 eyes with preoperative visual acuities of 20/70 or worse and only two of 14 eyes with preoperative visual acuities of 20/60 or better. Visual acuity was stabilized or improved in 55 of 62 eyes in which the foveal edge of the choroidal new vessels was within the margins of the pretreatment scotoma and in only 15 of 32 eyes with foveal edges extending beyond the scotoma margins.