Initial clinical experience using a diode laser in the treatment of retinal vascular disease

Intralesional diode laser pretreatment facilitates surgery for orbital venous malformations: initial experience with 23 consecutive patients

PURPOSE

This study aims to evaluate the efficacy and safety of intralesional diode laser pretreatment for facilitating surgery for orbital venous malformations (OVMs).

METHODS

This is a retrospective, non-comparative, interventional cohort involving 23 consecutive OVM patients undergoing intralesional laser pretreatment followed by surgical excision. The main outcome measures included volumetric changes, exophthalmometry, cosmesis, and symptom scores as well as treatment-related adverse events.

RESULTS

Following intralesional diode laser, the mean volume dropped significantly from 2366 ± 1887 to 129 ± 119 mm³ (t = 5.716; p < 0.001). After a single treatment session, a mean 90 ± 13% volume shrinkage was achieved in all 23 OVM. The mean Hertel exophthalmometry decreased significantly from 14 ± 3 to 13 ± 1 mm (t = 2.515; P < 0.02). The resolution of periocular dyschromasia and swelling were evident in 20 patients (87%). Symptom scores improved significantly from 6.5 ± 1.4 (very intense discomfort or effect on daily living) to 1.2 ± 1.0 (very mild discomfort or effect on daily living; p < 0.001). Short-term bruises and swelling were reported in 20 patients (87%).

CONCLUSION

Intralesional laser pretreatment is effective to facilitate surgery especially for the deep involving orbital venous malformations.

Laser-Activated Corneal Adhesive: Retinal Safety in Rabbit Model

Purpose

The purpose of this study was to investigate whether laser irradiation, used to activate an adhesive for sealing penetrating corneal incisions, causes any ophthalmoscopically or histologically visible retinal changes.

Methods

Baseline fundus assessment was conducted prior to laser irradiation of eyes of pigmented Dutch Belted rabbits. Treatment group was 18 eyes with the corneal adhesive activated in situ by a near infrared laser (125 mW for 45 seconds). The positive control group was 18 eyes, each irradiated for 60 seconds at 375, 500, 625, and 750 mW at different retinal locations. Unexposed regions of the retina were used as negative internal control. Ophthalmoscopic assessment was conducted immediately after laser exposure and prior to euthanasia. Retinas were histologically assessed at 0, 3, 72, and 168 hours after treatment.

Results

No ophthalmoscopically or histologically visible retinal changes were observed in the treatment group immediately, nor up to 168 hours after laser irradiation. In the positive control group, the incidences of ophthalmoscopically visible retinal lesions increased with irradiation power: 5.6% at 375 mW, 16.7% at 500 mW, 44.4% at 625 mW, and 50% at 750 mW. Histologically, retinal damage was observed as coagulative necrosis to all layers of the neural retina, including the retinal pigment epithelium.

Conclusions

The laser irradiation process used in the corneal adhesive technology did not cause any ophthalmoscopically or histologically visible retinal changes in the in vivo pigmented rabbit model. Prolonged exposure with this laser and at higher power can cause coagulative necrosis to the retina.

Translational Relevance

The corneal adhesive can be applied in humans without causing laser retinal damage.

Photocoagulation for retinal vein occlusion

The role of photocoagulation in retinal vein occlusion (RVO) has been studied since 1974. The most serious complications of central retinal vein occlusion (CRVO) and branch retinal vein occlusion (BRVO) are: (i) visual deterioration, most commonly due to macular edema, and (ii) the development of ocular neovascularization (NV), particularly neovascular glaucoma (NVG), with hazardous consequences for vision and even the eye itself. Before discussing the role of photocoagulation in the management of NV and macular edema in RVO, it is crucial to gain a basic scientific understanding of the following relevant issues: classification of RVO, ocular NV in RVO, and the natural history of macular edema and visual outcome of RVO. These topics are discussed. In CRVO, ocular NV is a complication of ischemic CRVO but not of nonischemic CRVO. Photocoagulation has been advocated to prevent and/or treat the development of ocular NV and NVG. Since NVG is the most dreaded, intractable and blinding complication of ischemic CRVO, the role of photocoagulation and its management are discussed. Findings of three randomized, prospective clinical trials dealing with photocoagulation in ischemic CRVO are discussed. The role of photocoagulation in the management of ocular NV and macular edema in BRVO, and three randomized, prospective clinical trials dealing with those are discussed. Recent advent of intravitreal anti-VEGF and corticosteroid therapies has drastically changed the role of photocoagulation in the management of macular edema and NV in CRVO and BRVO. This is discussed in detail.

Patient Comfort with Yellow (577 nm) vs. Green (532 nm) Laser Panretinal Photocoagulation for Proliferative Diabetic Retinopathy

PURPOSE

Pain associated with panretinal photocoagulation (PRP) can adversely affect the number and quality of retinal burns delivered and subsequently increase the number of treatment sessions required to achieve regression of proliferative diabetic retinopathy (PDR). We assessed comfort in patients undergoing treatment with yellow (577 nm) vs. green (532 nm) PRP for PDR.

DESIGN

Prospective, single-center, randomized crossover clinical trial.

SUBJECTS

Patients with PDR with high-risk characteristics.

METHODS

Subjects were equally randomized to first receive PRP with a laser indirect ophthalmoscope with either green (IQ 532; IRIDEX, Mountain View, CA) or yellow (IQ 577; IRIDEX) laser, followed by additional treatment with the opposite laser using standardized settings in the superior hemisphere of a single treatment eye per patient. Topical anesthetic was used in all study eyes before each treatment and power was titrated until moderate grey-white retinal burns were achieved.

MAIN OUTCOME MEASURES

The primary outcome measure was patient's perceived pain as measured with a standardized 10-point pain scale. Secondary outcome measures included laser power, treatment time, number of treatment shots with each laser, and physician ease-of-use score with each laser on a 10-point scale.

RESULTS

Forty patients (40 eyes) with a mean age of 54.0 years were enrolled. Mean pain scores were similar when comparing treatment with yellow and green laser (3.1 ± 2.3 vs. 2.8 ± 2.6; P = 0.40). No significant difference was seen in visual acuity (P = 0.44) or central macular thickness (P = 0.39) 1 month after PRP. Additionally, there were no significant differences when comparing minimum power required (243.2 ± 74.2 vs. 234.0 ± 59.6 mW; P = 0.55), treatment time (5.1 ± 3.6 vs. 5.6 ± 3.9 minutes; P = 0.384), and number of treatment shots (257.6 ± 12.6 vs. 258.0 ± 2.3; P = 0.68). Six of 7 co-investigators (85%) preferred using yellow laser over green and reported ease-of-use scores of 9.0 ± 1.2 and 7.6 ± 1.4, respectively (P = 0.07). No severe adverse events occurred.

CONCLUSIONS

Patient comfort during PRP for PDR utilizing laser indirect ophthalmoscopy is similar for green and yellow wavelengths.

Green lasers are beyond power limits mandated by safety standards

There has been an increasing number of reports of people losing vision from laser exposure from pocket laser pointers despite the safety limit of 1 milliwatt (1mW) imposed by the Australian government. We hypothesize that this is because commercially available red and green laser pointers are exceeding their labeled power outputs. We tested the power outputs of 4 red and 4 green lasers which were purchased for less than AUD$30 each. The average of 10 measurements was recorded for each laser. We found that 3 out of 4 red lasers conformed to the 1mW safety standard; in contrast, all of the green lasers exceeded this limit, with one of the lasers recording an output of 127.9 mW. This contrast in compliance is explained by the construction of these lasers - green lasers are typically Diode Pumped Solid State (DPSS) lasers that can emit excessive infrared (IR) radiation with poor workmanship or inconsistent adherence to practices of safe design and quality control; red lasers are diode lasers which have limited power outputs due to `Catastrophic Optical Damage' (COD). Relevant professional bodies ought to advocate more strongly for stringent testing, quality control and licensing of DPSS lasers with a view towards government intervention to banning green laser pointer use.

The 2014 Bowman Lecture-Bowman's and Bruch's: a tale of two membranes during the laser revolution

To describe the historical evolution of the role of lasers in effecting therapeutic changes in the four acellular membranes of the eye. Over the past 50 years, iterative developments have been instituted in lasers used for various forms of eye surgery predominately on the basis of data generated in early experiments in the 1960s to determine thresholds for damage and their incorporation in codes of practice for laser safety. The evolutionary steps are described. Excimer laser technology resulted in the generation of the new field of laser refractive surgery with over 40 million individuals now having undergone procedures such as photorefractive keratectomy and LASIK. Developments in lasers used for various forms of retinal surgery have undergone changes involving shorter and shorter pulse durations together with changes in beam energy distribution with implications for potential intervention in AMD prophylactically. Lasers have made a major impact on surgical treatment on all four acellular membranes of the eye but particularly Bowman's membrane in refractive surgery, where it has been demonstrated that it can be removed without significant consequences for eye health or vision.

Side-effects and complications of laser treatment in diabetic retinal disease

Laser treatment for diabetic retinopathy was the first intraocular treatment to provide a highly effective means for preventing visual loss in patients with diabetes. Although inherently destructive, laser treatment is remarkably effective in preventing visual loss and preserving vision long-term. This review will describe briefly the current techniques and discuss in detail the reported side-effects and potential complications of laser treatment of diabetic retinal disease.

Laser treatment for diabetic macular edema in the 21st century

Diabetic macular edema (DME) is the leading cause of blindness in the diabetic population. The diabetes Control and Complications Trial reported that 27% of patients affected by type 1 diabetes develop DME within 9 years of onset. Other studies have shown that in patients with type 2 diabetes, the prevalence increased from 3% to 28% within 5 years of diagnosis to twenty years after the onset. At the present time, despite the enthusiasm for evaluating several new treatments for DME, including the intravitreal therapies for DME (e.g., corticosteroids, and anti-VEGF drugs), laser photocoagulation remains the current gold standard and the only treatment with proven efficacy in a wide range of clinical trials for this condition. Despite being the standard technique for comparison and evaluation of the emerging treatments, we have generally poor understanding of the ETDRS recommendations, and we often forget about the results of laser in DME. The purpose of this review is to update our knowledge on laser photocoagulation for DME with an extensive review of the ETDRS results and discuss the laser techniques. Furthermore, we will describe the new developments in laser systems and review the current indications and results. Finally, we will discuss the results of laser treatments versus the current pharmacological therapies. We conclude by trying to provide a general overview that which laser treatment must be indicated and what types of lasers are currently recommended.

Transscleral diode photocoagulation of large retinal and choroidal vascular lesions

BACKGROUND

Transscleral retinal photocoagulation with a diode laser is used in glaucoma refractory to medical and surgical treatment. Our main research question was how the technique performed in large vascular lesions associated with hemangiomas of the retina and choroid.

METHODOLOGY/CLINICAL FINDINGS

Patient charts were retrieved from the hospital files for patients who underwent the procedure and were followed for at least 24 months. Five patients (6 eyes) fit the criteria. Cases included Von Hippel's disease (2 eyes), Coats' disease (1 eye) and choroidal hemangioma (3 cases). Transscleral diode laser treatment was performed under retrobulbar and topical anesthesia with a retinopexy probe (IRIS DioPexy, IRIS Medical Instruments, Mountain View, CA) applied transsclerally under indirect ophthalmoscope visualization. We found an improvement in best-corrected visual acuity at 24 months postoperatively.

CONCLUSIONS/SIGNIFICANCE

Transscleral photocoagulation may have a clinical application in these diseases as an alternate to the high cost of photodynamic therapy with photosensitizing agents.

Long-term safety, high-resolution imaging, and tissue temperature modeling of subvisible diode micropulse photocoagulation for retinovascular macular edema

PURPOSE

To determine the long-term safety of high-density subvisible diode micropulse photocoagulation (810 nm), compare the clinical findings with computational modeling of tissue hyperthermia and to report results for a subset of eyes treated for diabetic macular edema (ME) documented pre- and postoperatively by spectral-domain optical coherence tomography.

METHOD

All eyes treated for ME from diabetic retinopathy (diabetic ME) and branch retinal vein occlusion between April 2000 and January 2010 were reviewed for subvisible diode micropulse laser-induced retinal damage. Therapeutic outcomes were reviewed for a subgroup treated for diabetic ME with pre- and postoperative spectral-domain optical coherence tomography. Laser-induced retinal thermal effects were modeled computationally using Arrhenius formalism.

RESULTS

A total of 252 eyes (212 diabetic ME, 40 branch retinal vein occlusion) of 181 patients qualified. None of the 168 eyes treated at irradiance <350 W/cm2 and 7 of 84 eyes at ≥ 590 W/cm2 had retinal damage (P = 0.0001) (follow-up 3-120 months, median, 47). Sixty-two eyes of 48 patients treated for diabetic ME with pre- and postoperative spectral-domain optical coherence tomography with median 12 months follow-up had no retinal injury by infrared, red-free, or fundus autofluorescence photos; fluorescein angiography or indocyanine green angiography; or spectral-domain optical coherence tomography. Central foveal thickness (P = 0.04) and maximum macular thickness decreased (P < 0.0001). Modeling of retinal hyperthermia demonstrates that the sublethal clinical regimen corresponds to Arrhenius integral >0.05, while damage is likely to occur if it exceeds 1.

CONCLUSION

Subvisible diode micropulse can effectively treat retinovascular ME without laser-induced retinal damage, consistent with Arrhenius modeling of pulsed hyperthermia.

Micropulsed diode laser therapy: evolution and clinical applications

Many clinical trials have demonstrated the clinical efficacy of laser photocoagulation in the treatment of retinal vascular diseases, including diabetic retinopathy. There is, however, collateral iatrogenic retinal damage and functional loss after conventional laser treatment. Such side effects may occur even when the treatment is appropriately performed because of morphological damage caused by the visible endpoint, typically a whitening burn. The development of the diode laser with micropulsed emission has allowed subthreshold therapy without a visible burn endpoint. This greatly reduces the risk of structural and functional retinal damage, while retaining the therapeutic efficacy of conventional laser treatment. Studies using subthreshold micropulse laser protocols have reported successful outcomes for diabetic macular edema, central serous chorioretinopathy, macular edema secondary to retinal vein occlusion, and primary open angle glaucoma. The report includes the rationale and basic principles underlying micropulse diode laser therapy, together with a review of its current clinical applications.

Subthreshold micropulse diode laser photocoagulation for clinically significant diabetic macular oedema: a three-year follow up

PURPOSE

To report the long-term visual outcome of subthreshold micropulse diode laser photocoagulation for clinically significant diffuse diabetic macular oedema (CSME).

DESIGN

Non-comparative case-series.

METHODS

The main outcome measures of this 3-year follow-up study of infrared (810 nm) subthreshold diode micropulse laser photocoagulation for CSME were visual outcome and the angiographic CSME status of 19 patients (25 eyes).

RESULTS

Visual acuity stabilized or improved in 84% of treated eyes by the end of the first year. The result was maintained in the second year and by the third year, 92% maintained vision. However, more patients needed supplementary grid laser in the third year than in the second year. CSME decreased in 92% of the eyes and resolved in 88% in the first year. By the second year, 92% showed complete resolution. However, in the third year, recurrent CSME was noted in 28% of patients.

CONCLUSION

This study has the longest follow up reported so far and demonstrating that subthreshold micropulse diode laser photocoagulation has a beneficial long-term effect on visual acuity and resolution of CSME with minimal chorio-retinal damage.

Laser treatment of cultured retinal pigment epithelial cells-evaluation of the cellular damage in vitro

PURPOSE

Evaluation of the effects of laser photocoagulation on cultured primary retinal pigment epithelial cells.

METHODS

Cells were treated by a diode laser (678 nm) with 800 and 1600 mW for 0.186 second. Cell toxicity was tested by the WST-1 assay, and the uptakes of glutamate and gamma-aminobutyric acid (GABA) were measured.

RESULTS

Laser photocoagulation (1600 mW) caused cell damage and the mitochondrial enzyme activity evaluated by a WST-1 test significantly decreased by 20%-30%. Laser treatment caused a dose-dependent decrease in glutamate uptake but increased GABA uptake.

CONCLUSIONS

Laser treatment and the laser-induced increase in temperature influence transport processes in retinal pigment epithelial cells and may cause cell damage in the posterior part of the retina.

Subthreshold micropulse diode laser treatment in diabetic macular oedema

BACKGROUND/AIM

Enlargement of laser scars after retinal argon laser photocoagulation can give rise to deterioration in visual acuity. Subthreshold micropulse diode laser may decrease this risk. The aim of this study was to compare the effectiveness of subthreshold micropulse diode laser (810 nm) and conventional argon laser (514 nm) photocoagulation for the treatment of clinically significant macular oedema in diabetic patients.

METHODS

23 eyes of 16 patients were randomised to either treatment. Follow up was conducted for a minimum of 5 months. Changes in visual acuity and macular oedema measured by optical coherence tomography were examined.

RESULTS

Visual acuity remained stable in all treatment groups throughout the observation period. Changes in retinal thickness were small both foveally and perifoveally. In patients with focal macular oedema a significant reduction in retinal thickness (9% approximately -26 microm, p = 0.02) was seen foveally 3 months after diode laser photocoagulation.

CONCLUSION

Subthreshold micropulse diode laser and conventional argon laser treatment showed an equally good effect on visual acuity. Subthreshold micropulse diode laser showed a stabilising or even improving effect on macular oedema. The combination of primary diode laser and supplementary argon laser might be particularly favourable in reducing diabetic macular oedema.

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.

Diode laser transscleral retinopexy in rhegmatogenous retinal detachment surgery

PURPOSE

To evaluate the safety and efficacy of transscleral diode laser for retinopexy in rhegmatogenous retinal detachment surgery.

METHODS

Conventional retinal detachment surgery with transscleral diode laser retinopexy was performed on 52 eyes of 52 patients (22 female, 30 male), aged from 12 to 74 years (mean 51 + 4.1).

RESULTS

Of the 52 eyes 36 (69%) were reattached in a single operation and adequate chorioretinal scars were achieved in 34 of them. Additional transpupillary laser photocoagulation was performed in two cases in the postoperative period. Retinal re-attachment was achieved with exoplant revision and transscleral laser retinopexy in six cases (12%). Ten cases (19%) with severe PVR were reattached with vitreoretinal surgery.

CONCLUSIONS

Transscleral diode laser retinopexy was an effective and safe method, with accurate lesion location, concurrent permanent laser marks on the retina, and easy transmission through the extraocular muscles and solid buckling elements. Minor complications were minimized by gaining experience with the technique.

Evidence-based recommendations for the diagnosis and treatment of neovascular glaucoma

PURPOSE

To succinctly update information on the pathogenesis, etiology, diagnosis, and treatment of neovascular glaucoma based on a systematic review of available literature and to provide summary recommendations rated for their importance to clinical outcome.

CLINICAL RELEVANCE

Neovascular glaucoma is a devastating ocular disease that often results in loss of vision. The current standard of care includes retinal ablation and control of increased intraocular pressure with medical and surgical therapy. LITERATURE REVIEW METHODOLOGY: The authors conducted a MEDLINE literature search of articles published in English from 1966 to the present. Each article reviewed was rated as to the strength of evidence it provided, and summary ratings for the strength of evidence supporting clinical recommendations were generated.

RESULTS

Level A (most important to patient outcome) recommendations for the diagnosis of neovascular glaucoma include a high index of suspicion, a full ocular examination including undilated gonioscopy, and pupil examination. In regard to treatment, Level A recommendations include treatment of the underlying disease origin, complete panretinal photocoagulation (if retinal ischemia is a factor), and medical control of both elevated intraocular pressure and inflammation. Level B recommendations (moderately important to patient outcome) encompass glaucoma surgery to control intraocular pressure when medical therapy is unsuccessful, although the ideal surgical procedure is unknown. Currently, trabeculectomy with antimetabolite therapy, aqueous shunt implants, and diode laser cyclophotocoagulation are the preferred surgical treatment options.

CONCLUSIONS

The current literature on neovascular glaucoma has few articles that provide strong evidence in support of therapy recommendations (level I). Future research studies are needed to address areas in which the current evidence is moderately strong (level II) or weak, consisting only of a consensus of expert opinion (level III). Whenever practicable, these studies should be prospective, randomized clinical trials.

Diode laser-induced thermal damage evaluation on the retina with a liposome dye system

BACKGROUND AND OBJECTIVES

The aim of the study was to evaluate the feasibility of retinal thermal damage assessment in a rabbit eye model by using laser-induced release of liposome-encapsulated dye.

STUDY DESIGN/MATERIALS AND METHODS

After anesthesia, thermosensitive liposomes (DiStearoyl Phosphatidyl Choline: DSPC) loaded with 5,6-carboxyfluorescein were injected intravenously to pigmented rabbits. Retinal photocoagulations were performed with a 810nm diode laser (P=100-400 mW, laser spot=500 microm, 1s) (OcuLight, IRIS Medical Instruments, Mountain View, CA). Fluorescence measurements in the area of the laser exposures were then realized with a digitized angiograph (CF-60UVi, Canon-Europe, The Netherlands; OcuLab, Life Science Resources, UK).

RESULTS

Fluorescent spots were observed for power ranging from 100 +/- 5 mW to 400 +/- 5 mW. The fluorescence intensity increased linearly with the power and reached a plateau at 280 +/- 5 mW. The fluorescence intensity was correlated to the maximum temperature at the center of the laser spot with a linear increase from 42 +/- 3 degrees C to 65 +/- 3 degrees C. These results are in agreement with our two previous studies with DSPC liposomes for temperature measurements in a tissue model and then in a vascular model.

CONCLUSION

This preliminary study demonstrates the possibility of a laser-induced release of liposome-encapsulated dye for a quantification of diode laser induced thermal damage in ophthalmology. Such a method could be useful for a real-time monitoring of laser photocoagulation for conditions such as choroidal neovascular membranes when a precise thermal damage is required near the foveolar area.

High-power diode laser in neurosurgery: clinical experience in 30 cases

BACKGROUND

High-power semiconductor diode lasers were recently introduced and have been tested in ophthalmology and general surgery. These lasers are attractive from the practical and economical standpoint, and have enough power to perform most surgical procedures. They could replace other surgical lasers such as CO2, argon, 1.06 microm, and 1.32 microm Nd-YAG lasers for many applications in neurosurgery. We report our initial experience with the first available 0.805-microm surgical diode laser, the Diomed 25 (Diomed, Ltd, Cambridge, U.K.) in a series of 30 patients.

METHODS

The diode laser was evaluated during surgical resection of various types of central nervous system tumors in 30 patients. It was used free-hand in 27 patients in contact and non-contact, continuous wave (cw) and pulsed modes, and during ventricular endoscopy in three patients. Average time of laser use during a procedure was 248 seconds. Output power ranged from 1 to 25 watts, with an average power per patient of 2.64 to 15.5 watts (mean, 8.78 watts). Total energy delivered ranged from 65 to 11,051 joules per patient.

RESULTS

Using 600- or 400-microm non-contact optic fiber, well pigmented tumor tissue hemostasis was obtained at cw 3 to 10 watts with a defocused beam, whereas vaporization required 10-25 cw or pulsed watts with a focused beam. Soft and tough tissue section could be obtained using a sculpted cone-shaped (600-300 microm tip) contact fiber at 7-10 cw watts after fiber tip charring. Because of the deeper penetration of 0.805-microm light in non-pigmented tissues, non-contact mode is not recommended for white matter or poorly vascularized tumors. The contact mode was not efficient on very soft tissues such as edematous brain parenchyma. The contact fibers proved to be very fragile because of heat generation.

CONCLUSIONS

The high power diode laser proved to be efficient for hemostasis, section and vaporization, using contact and non-contact modes, at different output powers. Economical and ergonomical advantages of this new generation of surgical lasers may cause them to replace other surgical lasers such as argon, CO2, and Nd-YAG lasers, mostly for tumor surgery.

"Cyclodiode". Trans-scleral diode laser cyclophotocoagulation in the treatment of advanced refractory glaucoma

PURPOSE

To analyze the results of intraocular pressure (IOP) reduction by diode laser contact cyclophotocoagulation ("cyclodiode") in cases of advanced glaucoma refractory to alternative treatments.

METHODS

Two hundred and ten eyes of 195 patients, ages 1 to 89 years (mean, 51 years) were followed for 3 to 30 months (mean, 10 months) after cyclodiode treatment.

RESULTS

More than one treatment was given in 102 eyes (49%), and the overall mean number of treatments given per eye was 1.75 (range, 2-5). Mean pretreatment IOP was 34.1 mmHg (+/-10.6 mmHg). At last follow-up, mean IOP was 20.1 mmHg (+/-9.3 mmHg), and mean total medications was reduced from 2.3 to 1.7. Mean final IOP was lowest in patients with silicone oil glaucoma (17.3 mmHg), and the mean reduction in IOP was greatest in patients with neovascular glaucoma (23.9 mmHg). At last follow-up, visual acuity was worse than before treatment in 29% of eyes, unchanged in 60%, and better in 11%. Overall success rate (IOP < 22 mmHg) was 66% at a mean follow-up of 10 months. Phthisis occurred in one eye (0.5%), and chronic hypotony (0 mmHg < IOP < 5 mmHg for > 3 months) in a further two eyes (1%). Corneal graft decompensation followed treatment in two eyes, macular pucker occurred in one eye, and combined hyphema/vitreous hemorrhage in one patient.

CONCLUSIONS

Diode laser cycloablation is relatively safe and effective at controlling IOP in eyes with advanced refractory glaucoma in the short and medium term. With the treatment parameters used, multiple applications may be needed.

Double-frequency Nd:YAG laser vs. argon-green laser in the treatment of proliferative diabetic retinopathy: randomized study with long-term follow-up

BACKGROUND AND OBJECTIVE

A randomized clinical trial using the argon-green (514 nm) and the double-frequency Nd:YAG (532 nm) lasers was carried out on 42 eyes with proliferative diabetic retinopathy (PDR), with the aim of assessing the long-term effects of double-frequency Nd:YAG panretinal photocoagulation (PRP).

MATERIALS AND METHODS

Twenty-one eyes were randomized to argon laser treatment (ALT) and 21 to double-frequency Nd:YAG laser treatment (NdLT). The mean follow-up was 28.90 months (+/- 6.13) in the ALT group and 29.57 months (+/- 5.17) in the NdLT group.

RESULTS

In the ALT group, 20 eyes (95.2%) showed regression of PDR and one eye (4.8%) enlargement of pre-existing new vessels. In the NdLT group, neovascularization regressed in 20 eyes (95.2%) and increased in one (4.8%).

CONCLUSIONS

The long-term efficacy of double-frequency Nd: YAG laser PRP in the treatment of PDR thus appears to be similar to that of argon-green.

Diode laser photocoagulation of choroidal neovascular membranes

BACKGROUND

Krypton or argon laser treatment of choroidal neovascularization (CNV) has been shown to be effective in reducing the incidence of severe visual loss. The usefulness of diode laser in the treatment of many chorioretinal disorders is currently under evaluation.

METHODS

Our study involved 42 eyes of 41 patients affected with CNV which were treated with a near infrared diode laser.

RESULTS

The mean follow-up was 10.12 months. Visual acuity improved in 12 eyes (28.6%), did not change in 17 eyes (40.5%) and worsened in 13 eyes (30.2%). Mean visual acuity before treatment was 0.23 and 0.21 after treatment. Recurrent CNV was seen in 13 eyes. In a subgroup of 24 well-defined juxtafoveal or extrafoveal CNVs which underwent direct photocoagulation visual acuity improved in 8 eyes (33.3%), was unchanged in 11 (45.8%) and worsened in 5 (20.9%). Five eyes showed recurrent CNV.

CONCLUSIONS

Our results appear to support the use of diode laser in the treatment of CNVs. The deeper penetration into the choriocapillaris of the diode wavelength could be effective in blocking CNV by inducing a more extensive chorioretinal atrophy.

Diode laser contact transscleral retinal photocoagulation: a clinical study

AIM

To examine the clinical efficacy of contact transscleral retinal photocoagulation with a diode laser.

METHODS

Transscleral retinal photocoagulation was performed on 36 eyes. The conditions treated included peripheral retinal breaks associated with retinal detachments (30 eyes) and giant retinal tears (six eyes). Of the 30 eyes with retinal detachments, 28 underwent transscleral photocoagulation to the site of drainage of subretinal fluid in an attempt to reduce the risk of hemorrhage.

RESULTS

Threshold lesions were obtained with irradiances of between 95.4 W/cm2 and 191 W/cm2. Satisfactory chorioretinal adhesion was achieved in all eyes with retinal breaks and giant retinal tears. The only significant complications of treatment encountered were punctate choroidal haemorrhages (three eyes). Drainage related choroidal haemorrhage following earlier photocoagulation occurred in two of 28 eyes.

CONCLUSIONS

This study confirms the clinical potential of transscleral diode laser photocoagulation in the therapy of surgical retinal conditions.

Irradiation of rabbit retina with diode and Nd:YAG lasers

AIMS

This study was carried out to compare the effects of continuous wave infrared laser radiation on pigmented and albino rabbit retinas at two wavelengths: 810 nm (diode) and 1064 nm (Nd:YAG).

METHODS

Transpupillary laser pulses were applied with a spot size of 200 microns and durations of 200 ms (pigmented rabbits) and 0.5-1 s (albino rabbits). Light and electron microscopic analyses were performed immediately after exposure.

RESULTS

In pigmented rabbits, threshold lesions were induced using a power of 100 mW with the diode and 200 mW with the Nd:YAG lasers. Damage was incurred by the retinal pigment epithelium with extension into the superficial and mid choroid posteriorly and into the outer retina anteriorly. In albino rabbits, lesions of comparable anteroposterior extension were identified using a power of 10 W with the Nd:YAG laser. Using diode laser irradiation, a maximum power output of 1.2 W failed to produce discernible lesions.

CONCLUSIONS

The observed patterns of morphological damage are produced by complex tissue radiation interactions. In pigmented animals, this was primarily related to absorption of radiant energy by melanin within the retinal pigment epithelium and the choroidal melanocytes. In albino rabbits, laser induced effects occurred as a consequence of multiple scattering, together with absorption within haemoglobin and possibly also within tissue water. The data obtained provide further insight into the biological mechanisms arising from retinal photocoagulation with near infrared lasers.

Continuous wave Nd:YAG laser photocoagulation in proliferative diabetic retinopathy

AIMS

The therapeutic efficacy of the continuous wave (CW) Nd:YAG laser (working in the free running mode) was investigated in proliferative diabetic retinopathy (PDR) comparing it with a conventional laser source such as the krypton laser.

METHODS

Twenty four eyes of 12 patients affected with bilateral PDR were included and divided in two groups. The right eyes were treated with a red krypton laser and the left eyes with a CW Nd:YAG laser.

RESULTS

Three months after krypton photocoagulation 10 eyes showed a reduction or a complete regression of PDR and two eyes were unchanged. In the CW Nd:YAG laser group no eyes showed any regression of new vessels, in seven eyes the angiographic features were unchanged, and in five eyes they worsened. All the eyes of the second group underwent retreatment with the krypton laser after 3 or 6 months. After a mean follow up of 13 months all eyes in the krypton group showed a reduction or complete regression of PDR; in the retreated group 10 eyes improved and two were unchanged.

CONCLUSIONS

The statistical analysis showed a highly significant difference (p = 0.001) between krypton and CW Nd:YAG laser which indicated the lack of efficacy of the latter in the treatment of PDR. In the krypton laser group no significant difference (p = 0.05) after the retreatment was found confirming the efficacy of this treatment.

Diode laser photocoagulation for diabetic macular oedema

AIMS

This study aimed to investigate whether diode laser irradiation, which is poorly absorbed by haemoglobin, can induce closure of leaking retinal microvascular lesions in the treatment of diabetic macular oedema.

METHODS

Thirty three eyes with clinically significant diabetic macular oedema were treated with a diode laser. Fundus evaluation before and after treatment included visual acuity, stereoscopic biomicroscopy, colour photographs, and fluorescein angiography.

RESULTS

At a mean period of review of 6 months macular oedema had completely or partially resolved in 27 eyes. Visual acuity improved in three, deteriorated in one, and was unchanged in 29 eyes.

CONCLUSION

Preliminary data suggest that diode laser therapy induces closure of leaking retinal microaneurysms and is effective in the treatment of diabetic macular oedema.

Laser energy and dye fluorescence transmission through blood in vitro

PURPOSE

Because of the potential usefulness of evaluating and treating choroidal neovascularization obscured by blood, we designed this study to quantify the transmission of dye fluorescence and laser energy through blood.

METHODS

Blood preparations anticoagulated with ethylenediaminetetraacetic acid with hematocrits of 0% (plasma), 46%, and 99% were placed in open cuvettes with path lengths of 100, 200, or 500 microns and were exposed for one minute to either 100% oxygen or 100% carbon dioxide. Each cuvette was then sealed. Photographs of the cuvettes of blood in front of a flask of fluorescein or indocyanine green solution were decoded and used to calculate the percent transmission of fluorescence through blood. Cuvettes of blood were also placed in the path of argon, krypton, and diode lasers for energy transmission measurements.

RESULTS

Plasma transmission of fluorescein and indocyanine green fluorescence and argon, krypton, and diode laser energy was 89% to 100% for all samples tested. Transmission of fluorescein fluorescence and argon laser energy through 99% hematocrit samples were both less than 5%. Transmission of indocyanine green fluorescence through 100-, 200-, and 500-microns-thick cuvettes filled with 99% hematocrit blood was 57%, 34%, and 4%. Transmission of krypton laser energy was 50%, 25%, and 6%; and transmission of diode laser energy was 60%, 35%, and 12% through 99% hematocrit blood. Intermediate transmission values were obtained for 46% hematocrit samples.

CONCLUSIONS

Krypton and, to a slightly greater degree, diode laser energy penetrate a thin film of blood. Indocyanine green fluorescence also penetrates a thin film of blood. If a layer of blood appears thinner than 500 microns, then indocyanine green angiography may be useful in imaging underlying pathologic features. If a lesion can be imaged with indocyanine green, then it can probably be treated with a krypton or diode laser.

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.

Color contrast sensitivity and pattern electroretinographic findings after diode and argon laser photocoagulation in diabetic retinopathy

The retinal depth at which photocoagulation is maximal varies with wavelength. We compared visual function of eyes undergoing photocoagulation by the near-infrared diode laser to the argon green laser. We treated 14 patients with diabetic retinopathy requiring bilateral panretinal photocoagulation with the diode laser on the right eye and the argon system on the left eye. Before and after treatment visual acuity, central and peripheral color contrast sensitivity, and pattern electroretinograms were recorded. No difference was noted in the clinical response or visual acuity outcome, but a tendency was observed for less decline in color contrast sensitivity and pattern electroretinogram recordings after diode laser photocoagulation. Although P values (.05 to .5) did not reach significance, a mean of 8.4 of 14 patients per test had better test results after diode laser treatment. Diode laser photocoagulation seems to be a viable alternative to argon laser treatment and may be a more gentle mode of treatment.

Diode lasers in ophthalmology

Compact laser emitting diodes of gallium-aluminium-arsenide are now available for incorporation into clinical lasers in ophthalmology. These lasers are cheap and have low running costs. They are portable and their wavelength of emission (810 nm) may be advantageous in certain clinical situations. Clinical trials in retinal vascular disease, trabeculoplasty, and cyclophotocoagulation, have been encouraging. Recent advances allow laser delivery through binocular indirect ophthalmoscopes, endolaser and contact transscleral probes in addition to slit lamp mounted versions. Laser delivery in situations which were previously impossible has immense implication for prevention of blindness due to glaucoma and retinal vascular disease throughout the world.

Diode versus argon-green laser panretinal photocoagulation in proliferative diabetic retinopathy: a randomized study in 44 eyes with a long follow-up time

A clinical randomized study using argon-green (532 nm) and diode (810 nm) lasers was carried out on 44 eyes (34 patients) affected by proliferative diabetic retinopathy (PDR), with the aim of evaluating the long-term effects of diode panretinal photocoagulation. Of the total 44 eyes, 22 were randomized to argon laser treatment (ALT) and 22 to diode laser treatment (DLT). The mean follow-up time was 25 +/- 5 months in the ALT group versus 24 +/- 4 months in the DLT group. In the ALT group 20 eyes (91%) showed regression of PDR whereas 2 eyes (9%) deteriorated. In the DLT group regression of neovascularization was observed in 22 eyes (100%). These results show that the long-term efficacy of diode laser PRP in the treatment of PDR is similar to that of argon-green laser PRP.

Photocoagulation of choroidal neovascular membranes with a diode laser

Nine eyes with parafoveal choroidal neovascular membranes due to age-related macular degeneration or angioid streaks were treated with a diode laser and were followed up to 40 weeks (mean 26 weeks). Angiographically proved closure of the membrane was achieved in seven eyes. Four lesions needed a second treatment for growth of subretinal neovascular tissue. Post-treatment visual acuity ranged from 6/9 to 6/60. Two eyes developed subfoveal membranes resulting in poor visual acuity. The morphology of the diode laser lesions differed from that of the argon green laser and was more similar to that of the krypton laser, producing a 'black hole' on the fluorescein positive print. In one particular eye fluorescein angiography revealed subfoveal choroidal non-perfusion next to the site of the diode lesion suggesting choroidal vascular closure.

Fields, DVLC and panretinal photocoagulation

Laser panretinal photocoagulation (PRP) reduces visual loss in proliferative diabetic retinopathy but decreases peripheral retinal function. The Driver and Vehicle Licensing Centre (DVLC) states that when a patient volunteers that he or she has had photocoagulation, a questionnaire will then be sent to the patient's diabetic physician who can refer the patient for formal field testing. Of 30 patients who had PRP, 15 failed DVLC visual field regulations using the Esterman binocular field test on the Humphrey field analyser. The failures were more likely to have had treatment with a xenon laser, but there was no difference between the groups as regards age, number of burns or whether an argon or diode laser was used. The patients who failed were more likely to be hypertensive (p = 0.04). Two patients with unilateral PRP could not meet the driving regulations because of other field defects. Diabetes itself causes field defects, and therefore even with small amounts of laser, formal field testing may be necessary.

Diode laser iridotomy in rabbit and human eyes

We investigated the use of an infrared diode laser to perform iridotomies in 20 eyes of ten rabbits and 40 eyes of 24 patients with primary angle-closure glaucoma. We used a two-stage method with initial circular stretch burns and subsequent penetrating multiple burns. The iris was perforated in one session and remained patent through ten months in rabbits, and seven to nine months in humans. Transitory clinical complications included intraocular pressure increase of more than 10 mm Hg (20%, eight of 40 eyes), corneal endothelial changes (5%, two of 40 eyes), clouding of lens surface (60%, 24 of 40 eyes), localized cataract (5%, two of 40 eyes), and pupillary distortion (70%, 28 of 40 eyes). No retinal damage was observed. Diode laser can be used for peripheral iridotomy.

Field loss after pan retinal photocoagulation with diode and argon lasers

Argon and diode laser pan retinal photocoagulation are used in diabetic proliferative retinopathy. This is a prospective study of the effects of each laser type on peripheral field loss. It shows that diabetics have significantly reduced peripheral field prior to laser compared to normals (p = 0.006). With identical pan retinal photocoagulation with either argon or diode laser there is no difference in field loss.

Diode laser trabeculoplasty

Diode laser is a solid state Gallium Aluminium Arsenide (Ga AlAs) laser with a wavelength of approximately 800 nm (near infrared radiation). It has a similar penetration to, and absorption within the ocular tissues as, Krypton red. Diode laser trabeculoplasty (DLT) was carried out on 20 glaucomatous eyes resulting in a mean fall in intraocular pressure of 6.35 mmHg at one month and 6.45 mmHg at three months. Over this early period DLT has an effect similar to argon laser trabeculoplasty (ALT) in the management of open-angle glaucoma.

Diode laser compared with argon laser for trabeculoplasty

A randomized prospective study on two groups of ten patients compared the efficacy of diode laser and argon laser trabeculoplasty. In the diode laser group the intraocular pressure was 23.0 +/- 3.97 mm Hg before the treatment, 20.2 +/- 4.49 mm Hg at two hours, 16.3 +/- 3.13 at six months, and 16.9 +/- 2.80 mm Hg at one year. The differences from baseline were statistically significant at six months (P = .0001) and at one year (P = .0001) but not at two hours. In the argon laser group the intraocular pressure was 23.4 +/- 3.6 mm Hg before the treatment, 22.7 +/- 4.35 mm Hg at two hours, and 17.6 +/- 4.53 mm Hg at six months. One patient had uncontrolled mean high intraocular pressure and underwent surgery. In the nine patients who completed the study the intraocular pressure at one year was 16.7 +/- 3.00 mm Hg. The differences from baseline were significant at six months (N = 10; P = .0001) and 12 months (N = 9; P = .0001) but not at two hours. Differences between the two groups were not significant at two hours, six months, and one year. Laser trabeculoplasty may be effectively with a diode laser.

Iris clipping of a diode laser beam when performing retinal photocoagulation

The Microlase infrared diode laser has recently become available for retinal photocoagulation. It uses a laser beam with a large convergence angle (23 degrees). This gives rise to a laser beam with a relatively large cross section at the subject's pupil. In this study the pupillary area required to view the fundus at the slit-lamp with a 90-dioptre lens is determined. It is found that the pupillary area required to view the fundus is smaller than the cross section of the Microlase laser beam at the pupil. Thus iris clipping of the laser beam can occur even though the surgeon has a clear and bright view of the fundus. Care should be taken to use the Microlase only in the presence of a widely dilated pupil.

Diode laser trabeculoplasty (DLT) for primary open-angle glaucoma and ocular hypertension

A pilot study has been carried out to examine the efficacy of diode laser trabeculoplasty in the treatment of primary open-angle glaucoma and ocular hypertension. The device used was portable and could be attached to a standard slit-lamp microscope. Powers of 0.8-1.2 W were used, with a spot size of 100 microns and a pulse of 0.20 second. Laser trabeculoplasty carried out on 20 eyes for glaucoma resulted in a mean ocular hypotensive effect of 10.2 mmHG at two weeks after treatment and of 9.55 mmHg at 6 months. It is concluded that diode laser trabeculoplasty is an effective mode of treatment for eyes with open-angle glaucoma or with ocular hypertension.

Semiconductor diode laser photocoagulation in retinal vascular disease

The authors successfully performed clinical transpupillary retinal photocoagulation in 30 eyes of 26 patients with retinal vascular disease using a gallium-aluminium-arsenide (GaAlAs) diode laser emitting at 805 nm. Retinal photocoagulation was performed at treatment powers of 300 to 1300 mW and exposure durations of 0.2 to 0.5 seconds with a 200-microns diameter treatment spot. Patients treated with both diode and argon green lasers required 4.5 +/- 1.8 times greater mean laser energy with diode compared with argon to create ophthalmoscopically similar lesions. Parallel experimental retinal photocoagulation in Chinchilla rabbits required 3.1 +/- 0.9 times more power to create ophthalmoscopically similar lesions with the diode laser than with the argon laser. Intraoperative subretinal hemorrhage occurred rarely in patients with an incidence of 4 (0.44%) of 9021 treatment spots. Patients complained of moderate-to-marked pain in 10 (43%) of 23 treatments initiated under topical anesthesia. A transpupillary diode laser may be used clinically to perform therapeutic retinal photocoagulation.

Trans-scleral application of a semiconductor diode laser

We used a diode laser with an output power of 1 W through a fiberoptic light pipe (200 microns diameter) to deliver laser energy through the sclera of pigmented rabbits. Ciliary body destruction occurred with energy levels of 300-400 mW and exposure time of 0.5 sec. Retinal photocoagulation was achieved with energy levels of 200-500 mW in 0.5 sec. Histologic examination of acute lesions demonstrated thermal destruction of ciliary body processes and retina. Chorioretinal scar formation was observed clinically and histologically within 2-3 weeks. Our data indicate that the transscleral diode laser may be used for destruction of the ciliary body processes or peripheral retinal coagulation in pigmented eyes.