Krypton Red Laser Research Articles

The Influence of Treatment Extent on the Visual Acuity of Eyes Treated With Krypton Laser for Juxtafoveal Choroidal Neovascularization

To examine the direct relationship between the extent of treatment with krypton red laser photocoagulation and visual acuity loss in eyes with choroidal neovascularization secondary to ocular histoplasmosis or age-related macular degeneration. Photographic and visual acuity records from 129 eyes treated in the Ocular Histoplasmosis Study--Krypton Laser and 224 eyes treated in the Age-Related Macular Degeneration Study--Krypton Laser were reviewed. The proportion of eyes with severe visual acuity loss (6 or more lines of loss) was examined for subgroups of eyes based on the distance of the neovascular lesion from the center of the foveal avascular zone and on the extent of laser treatment to the lesion. Differences in the proportions with severe visual acuity loss were evaluated by longitudinal data analysis methods. Among eyes in the Ocular Histoplasmosis Study--Krypton Laser with lesions less than 200 microns from the center of the foveal avascular zone, only 5% of eyes with laser treatment that covered the foveal side and had a narrow (< or = 100 microns) border of treatment to adjacent uninvolved retina experienced severe visual acuity loss compared with approximately 25% of eyes with either some of the foveal side of the lesion left untreated or a wide border of treatment on the foveal side. Treatment extent had little influence on severe visual acuity loss in eyes in the Ocular Histoplasmosis Study--Krypton Laser with neovascular lesions 200 to 500 microns from the center of the foveal avascular zone or in eyes in the Age-Related Macular Degeneration Study--Krypton Laser with lesions in either distance category. Accurate, complete treatment of choroidal neovascularization close to the foveal center is required to provide the patient with the best chance of avoiding further severe visual acuity loss, especially in patients with ocular histoplasmosis. Even among experienced retinal specialists, the required accuracy of treatment is difficult to achieve.

The role of laser wavelength in the treatment of vitreoretinal diseases

Advances in laser technology have provided ophthalmologists with lasers spanning the visible and near-infrared spectrum. Recently, prospective, randomized clinical trials have compared laser wavelengths in the treatment of specific disorders. The Krypton Argon Regression Neovascularization Study found no difference between argon blue-green and krypton red laser when performing panretinal photocoagulation to manage proliferative diabetic retinopathy. The Macular Photocoagulation Study Group and the Canadian Ophthalmology Study Group have independently found no substantial difference in treatment outcome when using argon green versus krypton red laser to treat choroidal neovascularization in eyes with age-related macular degeneration. These recent trials and others that evaluate laser management of proliferative diabetic retinopathy, choroidal neovascularization, retinopathy of prematurity, and retinal breaks are reviewed. Multiple studies have failed to identify a moderate difference in treatment outcome between treatments performed with different laser wavelengths; however, small differences in outcome cannot be excluded without further study involving great numbers of patients. At the present time, ophthalmologists should be reassured that individual preferences for one wavelength over another in specific situations should not have a major effect on the visual outcome of the procedure.

Blue and green upconversion in Er3+-doped fluoroindate glasses

Abstract The upconversion properties of Er3+ in fluoroindate bulk glasses (composition: 40InF3−20ZnF2−16BaF2−(20−x)SrF2−2GaF3−2NaF−xErF3 with x=1,2,3 and 4 mole %) are investigated, following 4 F 9 2 excitation with a red krypton laser. A strong green and a weaker blue luminescence is observed at room temperature corresponding to emissions from the thermally coupled 4 S 3 2 and 2 H 11 2 bands and the 2 H 9 2 level respectively. Resonant energy transfer processes involving two excited erbium ions and a two-step absorption process are proposed to explain the upconversion phenomena. The emission intensities depend on the excitation power as Pexcn with 1.5≤n≤1.7 for the green and 1.6≤n≤1.9 for the blue emission. The decay times and the relative intensities of the luminescence are also studied as a function of Er3+ concentration.

Laser Photocoagulation of Subfoveal Neovascular Lesions in Age-Related Macular Degeneration

A clinical trial has been conducted to evaluate the effect on vision of laser treatment (argon green or krypton red lasers, assigned randomly) compared with no treatment of eyes with subfoveal choroidal neovascularization associated with age-related macular degeneration. Three months after enrollment, the visual acuity of 37 (20%) of 184 laser-treated eyes had decreased 6 or more lines from the baseline level, while only 19 (11%) of 178 untreated eyes had suffered such large decreases (P = .01, chi 2 test). However, 24 months after enrollment, the visual acuity of only 23 (20%) of 114 laser-treated eyes had decreased by 6 or more lines from baseline compared with 41 (37%) of 112 untreated eyes (P less than .01, chi 2 test). On average, after 24 months, visual acuity of laser-treated eyes had decreased 3 lines from baseline, and visual acuity of untreated eyes had decreased 4 lines (P = .003, t test). Laser-treated eyes retained contrast threshold for large letters at or near baseline levels through 36 months of follow-up examinations, while the contrast threshold of untreated eyes worsened. Persistent or recurrent neovascularization was observed in 51% of the laser-treated eyes by 24 months after initial treatment but was not associated with decreased visual acuity. None of the findings suggested a reason to favor either the argon green or krypton red wavelength. Laser treatment of subfoveal neovascular lesions that meet the eligibility criteria for this study is recommended if both the patient and the ophthalmologist are prepared for a large decrease in visual acuity immediately after treatment.

Krypton Laser Photocoagulation for Neovascular Lesions of Age-Related Macular Degeneration

To the Editor. —The Macular Photocoagulation Study (MPS) Group recently reported the results of a randomized clinical trial comparing krypton red laser photocoagulation with no treatment for choroidal neovascular lesions involving the foveal avascular zone in patients with age-related macular degeneration. 1 Although a thorough review of the literature was not the purpose of the report, earlier work by Yassur et al 2 had bearing on the MPS results and should have been cited. Their results from a randomized trial involving 123 eyes with age-related macular degeneration and neovascular lesions involving the foveal avascular zone showed that 37 (67% ) of 55 untreated eyes had deterioration in visual acuity in comparison with only 22 (32% ) of 68 eyes treated with krypton laser. The MPS results for similar eyes showed that 98 (58% ) of 169 untreated eyes in comparison with 86 (49% ) of 174 treated eyes had severe visual loss (six or

Hereditary Hemorrhagic Macular Dystrophy

We treated two brothers who had a hemorrhagic macular lesion in one eye; a similar problem affected the fellow eye of both patients within eight months. Generalized fine granularity of the retinal pigment epithelium and peripheral iris transillumination defects were observed in both siblings. A study of the family suggested that the disorder was dominantly inherited and probably was Sorsby's pseudoinflammatory macular dystrophy. The macular lesions in one brother were treated by argon green laser photocoagulation and in the other brother by krypton red laser photocoagulation. Although the brother treated by krypton red laser photocoagulation attained better final visual function, additional differences in treatment methods also may have contributed to the final outcome.

VISUAL RESULTS AFTER LASER TREATMENT FOR PERIPAPILLARY CHOROIDAL NEOVASCULAR MEMBRANES

To investigate the potentially harmful effects of laser photocoagulation in the papillomacular bundle (PMB), the records of patients treated for idiopathic neovascular membranes or membranes secondary to histoplasmosis extending into the PMB were reviewed. Twenty-eight eyes of 27 patients were identified. Most eyes (75%) were treated with the krypton red laser, while the remainder (25%) were treated with either argon green (18%) or a combination of the two (7%). After treatment 21 eyes (75%) had stable or improved visual acuity and three eyes (11%) lost more than three lines. Four eyes (14%) had changes in the optic disc and one eye developed a permanent arcuate scotoma. These data suggest that severe visual loss and extensive visual field defects occur rarely after photocoagulation of peripapillary choroidal neovascular membranes.

Krypton Laser Photocoagulation for Neovascular Lesions of Age-Related Macular Degeneration

The Age-Related Macular Degeneration Study-Krypton Laser (AMDS-K) is a multicenter controlled clinical trial designed to determine whether krypton red laser photocoagulation is of value in preventing visual acuity loss in eyes with macular degeneration that have either choroidal neovascularization 1 to 199 microns from the center of the foveal avascular zone or choroidal neovascularization 200 microns or farther from the foveal avascular zone center with blood and/or blocked fluorescence extending within 200 microns of the foveal avascular zone center. Recruitment ended in December 1987 after 247 patients had been assigned to photocoagulation and 249 patients had been assigned to no treatment. At 3 years after randomization, 49% (86/174) of treated eyes, in contrast to 58% (98/169) of untreated eyes, had lost six or more lines of visual acuity. The average visual acuity of treated and untreated eyes at that time was 20/200 and 20/250, respectively. The benefit of laser treatment was largest among patients without evidence of hypertension and diminished to no apparent benefit among patients who had highly elevated blood pressure and/or used antihypertensive medication. Treatment of lesions meeting the AMDS-K eligibility criteria in eyes of patients with no hypertension is recommended. However, treatment cannot be recommended uniformly for patients with definite hypertension having lesions similar to those of patients enrolled in the AMDS-K.

Persistent and Recurrent Neovascularization After Krypton Laser Photocoagulation for Neovascular Lesions of Age-Related Macular Degeneration

The persistence and recurrence of choroidal neovascularization after initial treatment with laser photocoagulation have been shown to be major contributors to loss of visual acuity. The 247 eyes assigned to krypton red laser photocoagulation in the Age-Related Macular Degeneration Study-Krypton Laser were examined to describe the incidence, timing, visual impact, and potential risk factors for persistence and recurrence. Persistent neovascularization detected within 6 weeks of initial treatment was observed in 32% of treated eyes, and recurrent neovascularization was estimated by life-table methods to develop in an additional 47% over a 5-year period. Both persistence and recurrence were accompanied by an increased frequency of severe visual loss. The persistence rate among eyes having 10% or more of the foveal side of the neovascular membrane not covered by treatment was twice as high as in eyes having more extensive coverage. Patients having a fellow eye with a neovascular membrane or scar, a fellow eye with 20 or more drusen in the central macula, or a fellow eye with nongeographic atrophy at initial visit had more recurrences than patients without these characteristics. Ophthalmologists treating similar lesions may be able to reduce persistent neovascularization and the associated visual loss by covering the entire lesion with treatment.

PHOTOCOAGULATION SCAR EXPANSION AFTER LASER THERAPY FOR CHOROIDAL NEOVASCULARIZATION IN DEGENERATIVE MYOPIA

The authors performed a prospective study of 36 eyes affected by pathologic myopia with macular subretinal neovascularization (SRNV) successfully treated with either argon green, dye orange (590 nm), or krypton red lasers. Re-treated eyes were excluded. Evolution of the laser scar was carefully monitored for 12 months. Scar expansion was noted in 35 cases (97%), without a significant loss of visual acuity during the first year after treatment. The scar enlarged more conspicuously during the first 3 months after photocoagulation, with a mean increase of 103% in the first year. Expansion was not related to laser wavelength, patient age, SRNV size, or degree of myopia. Scar enlargement was greatest in the same direction as that of maximal extension of the myopic peripapillary crescent; inspection of the morphologic configuration of the peripapillary crescent before laser treatment may be helpful in evaluating the potential risk of post-laser scar expansion toward the fovea.

Clinicopathologic Study of Organic Dye: Laser in the Human Fundus

One day before enucleation for choroidal melanoma, four patients consented to experimental laser photocoagulation for the purpose of comparing the histopathologic appearance of acute chorioretinal lesions produced by various dye laser wavelengths with krypton red and argon green laser controls. Three patients had simulated “light” and “heavy” treatment of an extrafoveal choroidal neovascular membrane (CNVM) with wavelengths 577 nm (yellow), 595 nm (orange), and 600 nm (orange). One patient had simulated panretinal photocoagulation (PRP) with four different dye laser wavelengths. Extrafoveal “light” treatment with the three dye wavelengths and both controls spared the inner retina and produced similar effects in the outer retina, pigment epithelium, and choriocapillaris. Choroidal penetration was deepest with the longer wavelengths (590–647 nm) in both “light” and “heavy” treatment groups. “Heavy” treatment gave varying degrees of full-thickness retinal uptake for all dye and both control wavelengths. Both ends of the orange spectrum (590–600 nm) produced the most severe inner retinal uptake. Panretinal photocoagulation produced similar full-thickness retinal uptake for all four dye wavelengths tested. These results indicate that caution should be used when treating “heavily” with 590 and 600 nm in the extrafoveal area.

Iatrogenic Choroidal Neovascularization After Krypton Red Laser Photocoagulation

A major cause for failure of krypton red laser photocoagulation in patients with exudative age-related macular degeneration has been the development of recurrent choroidal neovascularization adjacent to the previously treated areas. After reviewing the possible causes of recurrences, it is apparent that a certain number are iatrogenic, ie, induced by krypton red laser causing disruption and damage to the pigment epithelium-Bruch's membrane-choroidal complex. We describe three separate episodes in two patients of iatrogenic recurrent choroidal neovascularization after krypton red laser photocoagulation.

The Treatment of Serous Macular Detachment Secondary Choroidal Melanomas and Nevi

The authors successfully treated with laser photocoagulation five patients who had a serous macular detachment secondary to leakage from a pigmented choroidal tumor. Three patients had dye leakage on fluorescein angiography from a choroidal neovascular membrane. The subretinal fluid resolved in all three patients after the neovascular membrane was obliterated by either krypton red (2 patients) or argon green (1 patient) laser photocoagulation. The other two patients had prominent leakage from a localized choroidal neovascular membrane as well as mild diffuse leakage over the entire tumor. Focal argon laser treatment to the neovascular membrane alone did not cause permanent resolution of the subretinal fluid. The fluid did resolve, however, after the entire area of diffuse leakage was retreated with photocoagulation. In one of the patients who received both focal and confluent laser treatment, the choroidal tumor grew in a collar-button fashion through Bruch's membrane at the original site of focal treatment. This eye was enucleated, and results of histopathologic examination showed a choroidal melanoma.

Persistent and Recurrent Neovascularization After Krypton Laser Photocoagulation for Neovascular Lesions of Ocular Histoplasmosis

Persistence and recurrence of choroidal neovascularization after initial treatment with laser photocoagulation have been shown to be major contributors to loss of visual acuity. The 144 eyes assigned to krypton red laser photocoagulation in the Ocular Histoplasmosis Study-Krypton Laser were examined to describe persistence and recurrence in these patients. Persistent neovascularization was observed among 23% of treated patients and recurrent neovascularization was observed among an additional 8%. Both persistence and recurrence were accompanied by an increased frequency of severe visual loss. Patients with high blood pressure were more than 2.5 times as likely to have persistent neovascularization as patients without high blood pressure (95% confidence interval = 1.5, 4.8). Eyes in which the neovascular component of the complex was within 200 microns of the center of the foveal avascular zone were twice as likely to have persistent neovascularization (95% confidence interval = 1.2, 4.6). Eyes in which the treatment did not cover the neovascularization completely or did not meet the required level of intensity on the foveal side had a persistence rate approximately three times that of eyes in which the neovascularization was covered completely by intense, confluent burns (95% confidence interval = 1.7, 6.5). This last finding is of particular importance for ophthalmologists who treat similar patients.

RETINAL LASER PHOTOCOAGULATION

Three monkeys were treated with krypton red laser photocoagulation in a manner simulating treatment of a choroidal neovascular membrane. One eye of each monkey was treated by employing immediately the power level needed to produce a lesion judged biomicroscopically to be of sufficient intensity (Method A). The fellow eye was treated by starting with lower power levels and then gradually increasing to the level needed to produce a similar-appearing lesion (Method B). Parameters of spot size and treatment duration were kept constant. Animals were sacrificed three days, eight days, and four months after treatment. Both methods of treatments spared the overlying ganglion cell layer in all fundus locations, but Method A induced cell loss in the inner nuclear layer while Method B spared it. Since reaching the clinical endpoint for Method B required fewer spots at the highest power level, the number of spots at the highest power level is probably the most important factor in determining degree of inner retinal absorption. Since both methods of treatment resulted in satisfactory closure in the choriocapillaries, the histopathologic differences may not be clinically important.

Modified Grid Laser Photocoagulation for Diabetic Macular Edema: The Effect on the Central Visual Field

Modified grid laser photocoagulation has been shown to stabilize visual acuity in patients with diabetic macular edema, but the effect on extrafoveal visual function is uncertain. Automated static threshold perimetry was performed on 64 eyes of 36 patients before and after modified grid therapy with the argon green or krypton red laser. Twenty-eight eyes underwent two grid treatments for persistent macular edema. For all eyes tested, average threshold sensitivity in the central 5° dropped 3.44 dB (standard deviation [SD], 3.79 dB) after the first treatment and 6.86 dB (SD, 5.02 dB) cumulatively after the second treatment. Qualitatively,. the grayscale displays of the central visual field were darker after treatment, but the scotomata from laser photocoagulation could not be distinguished from those due to macular edema. The foveal threshold showed no significant change. In a subgroup of patients tested, color vision was not significantly improved and nearly all patients exhibited a tritan defect before and after treatment. No difference was detected between the argon and krypton groups. This suggests that with modified grid laser photocoagulation visual acuity and foveal threshold are preserved at the expense of generalized loss of threshold sensitivity across the central 10° of the visual field.

Treatment of Small Choroidal Melanomas With Photocoagulation

Seventeen eyes with small choroidal melanomas presumed to be malignant were photocoagulated. The melanomas measured 7 to 15 mm at the tumor base and 2 t0 5 mm thick. First, photocoagulation using the green argon laser was aimed at closing the choroidal vascular supply of the tumor. In a second stage, tumor tissue was destroyed using the red krypton laser for confluent burns of long duration. Such treatment was supplemented by cryotherapy in peripherally located tumors or whenever photocoagulation alone did not result in tumor regression. Photocoagulation alone was used in ten eyes and combined wih cryotherapy in seven. After an average follow-up of 42 months, marked tumor regression was achieved in 12 eyes and some tumor regression in two. Tow eyes ultimately required proton beam irradiation, and one eye was enucleated. No metastasis occurred during follow-up.

Krypton laser for proliferative diabetic retinopathy: The Krypton Argon Regression of Neovascularization Study

The Krypton Argon Regression of Neovascularization Study (KARNS) is a multicenter, randomized, controlled clinical trial designed to determine the efficacy of red krypton laser photocoagulation in the treatment of proliferative diabetic retinopathy.

Histopathology of the Effects of Tuneable Dye Laser on Monkey Retina

The tuneable dye laser was used to simulate treatment of choroidal neovascularization and panretinal photocoagulation (PRP) in monkey retina. The histopathologic effects of wavelengths from 560 to 630 nm in juxtafoveal, papillomacular bundle, and nonfoveal areas were investigated. An unexpected observation using high-intensity burns in juxtafoveal and, to a lesser extent, in papillomacular bundle areas was inner retinal damage with 600-nm light. At moderate energy levels, the effects of 600 nm were more comparable with those with other wavelengths and included much less damage to the inner retinal layers. At mild energy levels, the effects were comparable with other wavelengths. During and after the application of the burns, the energy levels and ophthalmoscopic appearances were comparable for each wavelength for the high-, moderate-, and mild-intensity burns. The histopathologic effects of 630-nm light (tuneable dye red) were comparable with those of the standard krypton red (647 nm) laser. Nonmacular and PRP effects were similar with all wavelengths. These results indicate that power levels may need to be reduced when placing 600-nm (orange) laser burns in the macula.

Retinal Pigment Epithelial Tears: Patterns and Prognosis

Increasing experience with the diagnosis of retinal pigment epithelial (RPE) tears has led to expanded recognition and understanding of this clinical entity. The authors report 18 RPE tears followed for an average of 28 months; 16 were associated with age-related macular degeneration and 2 with presumed ocular histoplasmosis syndrome. Retinal pigment epithelial dehiscences fell into four categories: nine spontaneous tears associated with choroidal neovascularization, one tear associated with an RPE detachment without choroidal neovascularization, four iatrogenic tears occurring at krypton treatment of choroidal neovascularization, and four iatrogenic tears developing weeks to months after laser treatment of choroidal neovascularization. Eight patients had a final visual acuity of 20/100 or better, four were 20/200, and six were 20/400 or worse. Photocoagulation, particularly with the use of krypton red laser, may be modified on the basis of possible RPE tear formation. Heightened awareness of the possibility of inducing pigment epithelial rips should improve diagnosis and management of these cases.