Ablation of subretinal tissue with optical fiber delivered 266 nm laser pulses

New and more precise subretinal surgical techniques would be useful in a range of retinal diseases. The purpose of this study is to determine the feasibility of using fiberoptically delivered ultraviolet laser energy to transect or ablate subretinal tissues.Choroid segments dissected from fresh porcine eyes, with or without the retinal pigment epithelium (RPE), were clamped in a fluid bath. Pulsed fourth harmonic (266 nm) of a Nd:YAG laser radiation was delivered via an optical fiber probe at fluence levels between 0.08 and 0.40 J/cm². The tissue was then fixed and sectioned for histological examination. Radiation induced damage was categorized by the degree of tissue disruption and ablation depth.Tissue ablation and the severity of the tissue injury varied with both tissue properties and applied laser parameters. Disruption of Bruch’s membrane was typically induced by 10 pulses of 0.30 J/cm² or 2 pulses of 0.40 J/cm². Lower radiation doses did not disrupt Bruch’s membrane, but did damage the choroidal tissue and produce vacuoles in the underlying choroid. The full thickness of the choroid was ablated by 200 pulses of 0.40 J/cm². The presence of the RPE produced a shielding effect which was greater than would be expected for an equivalent thickness of choroidal tissue.Ablation characteristics of subretinal tissue are highly dependent on the laser parameters used and the type of tissue involved. To perform well controlled laser surgery on subretinal tissues both laser parameters and the properties of the target cells and tissues have to be considered.     

Excimer laser ablation of the human lens at 308 nm with a fiber delivery system

A 308 nm excimer laser has been used with a fiber delivery system to perform ablation of the human lens. Preliminary results demonstrate the system's ability to ablate lens nucleus and cortex selectively, preserving the anterior and posterior capsules. The total delivered energy necessary to ablate a human lens ranged from 35 to 63 joules. Laser tissue interaction and ablation rates were computed for the different components of the human lens (capsule, cortex, nucleus) for the operatively useful energy densities (fluences). Operative experience suggests that cortex and nucleus can be ablated while preserving the capsule if an adequate irrigation and aspiration system is developed. These results also suggest that this modality may be adequate for performing endocapsular cataract extraction. Laser tissue interactions were also computed at variable distances between the fiber tip and tissue. As this distance increased, the spread of the beam increased and a significant increase in energy was necessary to induce tissue ablation. This was due to the decrease in fluence with increasing distance to the target tissue and/or the absorption and scattering of the delivered energy within a short distance from the fiber tip by the ablated material. Evidence of a sonic effect was also present.     

Imaging retinal nerve fiber bundles using optical coherence tomography with adaptive optics

Early detection of axonal tissue loss in retinal nerve fiber layer (RNFL) is critical for effective treatment and management of diseases such as glaucoma. This study aims to evaluate the capability of ultrahigh-resolution optical coherence tomography with adaptive optics (UHR-AO-OCT) for imaging the RNFL axonal bundles (RNFBs) with 3 × 3 × 3 μm³ resolution in the eye. We used a research-grade UHR-AO-OCT system to acquire 3° × 3° volumes in four normal subjects and one subject with an arcuate retinal nerve fiber layer defect (n = 5; 29-62 years). Cross section (B-scans) and en face (C-scan) slices extracted from the volumes were used to assess visibility and size distribution of individual RNFBs. In one subject, we reimaged the same RNFBs twice over a 7 month interval and compared bundle width and thickness between the two imaging sessions. Lastly we compared images of an arcuate RNFL defect acquired with UHR-AO-OCT and commercial OCT (Heidelberg Spectralis). Individual RNFBs were distinguishable in all subjects at 3° retinal eccentricity in both cross-sectional and en face views (width: 30-50 μm, thickness: 10-15 μm). At 6° retinal eccentricity, RNFBs were distinguishable in three of the five subjects in both views (width: 30-45 μm, thickness: 20-40 μm). Width and thickness RNFB measurements taken 7 months apart were strongly correlated (p < 0.0005). Mean difference and standard deviation of the differences between the two measurement sessions were −0.1 ± 4.0 μm (width) and 0.3 ± 1.5 μm (thickness). UHR-AO-OCT outperformed commercial OCT in terms of clarity of the microscopic retina. To our knowledge, these are the first measurements of RNFB cross section reported in the living human eye.     

577nm阈下微脉冲激光与577nm激光光凝对兔视网膜组织影响的比较

背景 近年来研究表明,577 nm阈下微脉冲激光治疗视网膜疾病可达到传统577 nm激光光凝的治疗作用且对视网膜组织损伤小,但其具体作用机制和敏感的靶细胞尚未完全阐明. 目的 探讨和比较577 nm阈下微脉冲激光与577 nm激光光凝视网膜后成年中华黑兔视网膜组织形态学变化,为577 nm阈下微脉冲激光光凝在临床上的应用提供依据.方法 采用抽签法按照视网膜光凝条件不同将26只中华黑兔分为正常对照组(2只)、577 nm激光组(6只)和阈下微脉冲激光组(18只),其中阈下微脉冲激光组按照激光工作负载率的不同亚分为9％、12％和15％阈下微脉冲激光组,每组各6只,正常对照组不做任何处理.光凝后行彩色眼底照相及OCT检查,摘取兔眼球壁行苏木精-伊红染色,光学显微镜下观察兔脉络膜和视网膜组织结构的变化.结果 彩色眼底照相和OCT显示正常对照组兔眼视网膜组织结构清晰.9％阈下微脉冲激光组OCT扫描可见视网膜神经上皮层稍模糊;12％阈下微脉冲激光组光凝斑处视网膜神经上皮层轻度水肿,视网膜色素上皮(RPE)层稍模糊;15％阈下微脉冲激光组可见光凝斑处视网膜神经上皮层明显水肿,RPE层局限性隆起;各阈下微脉冲激光组彩色眼底照相均未见光凝斑.577 nm激光组兔眼彩色眼底照相可见灰白色光凝斑,OCT扫描层面可见视网膜呈多灶性隆起,视网膜各层组织结构模糊,伴浆液性神经上皮层脱离.视网膜组织病理学检查可见,与正常对照组兔眼相比,9％和12％阈下微脉冲激光组兔眼脉络膜血管变形或出血,但视细胞形态结构、双极细胞层和视网膜神经节细胞(RGC)层未见明显改变;15％阈下微脉冲激光组视细胞扁平状膜盘肿胀,双极细胞层和RGC层未见明显改变;577 nm激光组兔眼视细胞层、双极细胞层和RGC层结构紊乱,RPE层变薄.结论 577 nm阈下微脉冲激光对脉络膜层和RPE层具有高度选择性,视网膜光凝后对视网膜神经上皮层的损伤程度轻微,既可发挥治疗作用,又不损伤视网膜神经上皮;577 nm激光视网膜光凝可对视网膜全层造成损伤.     

Transscleral infrared laser for retinal ablation without retinal visualization in an experimental model

PURPOSE: To investigate whether transscleral diode laser can create retinal photocoagulation reliably without creating retinal holes under conditions simulating opaque media. METHODS: In New Zealand pigmented rabbits, optimal infrared diode laser power settings were determined, and transscleral retinal photocoagulation was then applied 4 mm and 6 mm from the limbus without retinal visualization. Transscleral testing was done using retina and cyclophotocoagulation probes placed directly on the sclera, on conjunctiva, and on silicone scleral buckles. RESULTS: A retina probe placed on the sclera achieved moderate retinal photocoagulation intensity in 75% of spots 4 mm from the limbus and in 50% of spots 6 mm from the limbus. Retinal holes were only formed when using the transscleral cyclophotocoagulation (TSCPC) probe. An association between burn intensity and the presence of conjunctiva was seen for the TSCPC probe (P = 0.0001) but not for the retina probe (P = 0.125). Photocoagulation spots did not exceed moderate intensity through any of the silicone scleral buckles tested. CONCLUSIONS: Transscleral infrared photocoagulation applied without retinal visualization did not cause retinal hole formation with a retina probe placed directly on conjunctiva, sclera, or scleral buckle material. A TSCPC probe created retinal holes when placed directly on sclera. A decrease in power was required for all treatments closer to the limbus.     

Experimental retinochoroidal tissue vaporization with a CO2 laser probe

The immediate and chronic effects of an intraocular carbon dioxide CO₂ laser probe used for tissue vaporization were studied in cynomolgus monkeys' eyes. Acute lesions produced necrosis (from superficial to deep) of the retina and choroid, depending on the amount of energy used. Chronic lesions showed disorganization of the retina and choroid, with scar formation. Extensive tissue vaporization produced tractional retinal detachment in the chronic stage. Tractional detachment was prevented if the area of CO₂ laser application was previously encircled with argon laser scars.This work was supported in part by PHS grant EYO 2377 from the National Eye Institute, National Institutes of Health, Bethesda, MD.     

Corneal ablation with new 193 nm solid-state laser: preliminary experiments

PURPOSE: To assess the ability of a newly developed 193 nm solid-state laser to ablate the cornea. SETTING: Osaka University, Osaka, Japan. METHODS: A prototype laser engine was developed by combining a 1547 nm laser diode, fiber amplifiers, and 5 stages of a frequency-conversion system using CsLiB6O10 crystals as the last stage. Poly(methyl methacrylate) (PMMA) plates were exposed to the prototype laser beam to determine the relationship between the fluence and ablation rate. Laser irradiation of porcine corneas was performed to induce morphological changes, and the quality of the lesions was determined by light and scanning electron microscopy. RESULTS: The relationship between the fluence and ablation rate of the 193 nm solid-state laser was comparable to that of the argon-fluoride excimer laser. Light and scanning electron microscopy of the porcine corneas showed that the linear and square lesions had sharp, clean edges. CONCLUSIONS: Smooth ablations of PMMA plates and porcine corneas were obtained by the laser. Further investigations must be conducted to determine whether this laser can be an alternative laser source for keratorefractive surgery.     

Assessment of retinal nerve fiber layer using optical coherence tomography and scanning laser polarimetry in progressive glaucomatous optic neuropathy

PURPOSE: To describe a case of progressive glaucomatous optic neuropathy using scanning laser polarimetry with fixed (SLP-FCC) and variable corneal compensation (SLP-VCC) and optical coherence tomography (OCT). DESIGN: Observational case report. METHODS: A 21-year-old male with juvenile primary open-angle glaucoma developed progression because of noncompliance with therapy. The patient underwent dilated stereoscopic examination and photography of the optic disk, standard automated perimetry (SAP), OCT, and SLP imaging with FCC and VCC at the baseline examination and after four years of follow-up. RESULTS: Optic disk, retinal nerve fiber layer (RNFL) atrophy, and SAP progression was observed. Reduction in mean RNFL thickness (average, superior, inferior) was 18, 18, and 27 microns (OCT); 22, 40, and 17 microns (SLP-FCC); and 6, 12, and 12 microns (SLP-VCC), respectively. CONCLUSIONS: This case demonstrates that digital imaging of the peripapillary RNFL is capable of documentation and measurement of progressive glaucomatous RNFL atrophy.     

倍频532nm激光治疗视网膜裂孔的临床观察

目的评价倍频532nm激光治疗视网膜裂孔的有效性。方法回顾性分析经临床确诊的58例(66眼)视网膜裂孔应用倍频532nm激光进行光凝治疗的临床疗效。其中有症状组32例(32眼);无症状组26例(34眼),随访时间3-6mo。结果有症状组成功封闭视网膜裂孔28眼,成功率87.5%;无症状组成功封闭视网膜裂孔32眼,成功率94.1%。两组成功率比较无显著性差异。结论倍频532nm激光治疗视网膜裂孔安全有效。     

倍频532nm激光治疗视网膜裂孔的临床观察

目的:评价倍频532nm激光在治疗视网膜裂孔中的临床疗效。方法:应用532nm激光治疗视网例膜裂孔患者52例62眼,追踪观察是否成功封闭视网膜裂孔、阻止视网膜脱离的发生。结果:随访6～24mo,成功封闭裂孔50例60眼,成功率96%,2例2眼裂孔封闭失败视网膜脱离范围扩大而改行视网膜冷凝术及外垫压术。结论:倍频532nm激光治疗封闭视网膜裂孔的方法安全有效,方便经济。     

Large optical ablation zone using the VISX S2 smoothscan excimer laser

PURPOSE: To prospectively evaluate the safety and efficacy of the new large-zone (6.5 mm) photoablation technology using the VISX S2 Smoothscan excimer laser. SETTING: University-based hospital, Stanford, California, USA. METHODS: Forty-two eyes of 21 patients with a mean preoperative spherical equivalent (SE) of-5.55 diopters (D)+/- 2.24 (SD) (range-2.13 to-10.75 D) had laser in situ keratomileusis (LASIK) using the VISX Smoothscan S2 excimer laser for simple myopia or compound myopic astigmatism. A 6.5 mm optical zone was used in all eyes. Patients were prospectively followed 1 day and 1 and 3 months postoperatively. RESULTS: At 3 months, the mean SE was reduced 94% to-0. 31+/- 0.55 D. Ninety-one percent of eyes had an uncorrected visual acuity of 20/40 or better. Eighty-eight percent were within+/-1.00 D of attempted correction and 84%, within +/-0.50 D. Stability within+/-0.50 D occurred after the first postoperative month. Vector analysis of eyes that had toric ablations demonstrated a difference vector within+/-1.00 D in 100% of eyes. The mean angle of error was-0.04+/- 6.37 degrees. Visually significant steep central islands associated with loss of best spectacle-corrected visual acuity was observed in 7.5% of eyes at 1 month. No eyes experienced significant glare or halos. CONCLUSIONS: The new large-zone (6.5 mm) photoablation technology with the VISX S2 Smoothscan resulted in effective reduction of simple myopia and compound myopic astigmatism. However, with the 6.5 mm zone, there may be an increased risk of developing symptomatic steep central islands in the early post-LASIK period compared with the standard 6.0 mm treatment zone.     

Diabetes-associated retinal nerve fiber damage evaluated with scanning laser polarimetry

PURPOSE: To evaluate retinal nerve fiber layer (RNFL) thickness in patients with diabetes mellitus compared with age-matched normal control subjects, to assess the correlation between the RNFL thickness and the severity of retinopathy, and to investigate whether diabetes mellitus is a potential source of abnormal results in glaucoma screening or evaluation with scanning laser polarimetry (SLP). DESIGN: Cross-sectional analysis of normal and diabetic eyes. METHODS: setting: Institutional clinical study. patients: One hundred twenty-eight subjects with type 2 diabetes mellitus and 50 age-matched normal control subjects without glaucoma or glaucoma-suspect. All patients underwent imaging with SLP and repeatable automated perimetry. Subjects with diabetes mellitus were classified into four stages on the basis of the severity of retinopathy that was assessed by dilated funduscopic examination, high-quality fundus color photography, and fluorescein angiography. MAIN OUTCOME MEASURES: The SLP (GDx VCC software, version 5.5.0) parameters. RESULTS: The RNFL thickness in patients with diabetes mellitus was reduced significantly compared with age-matched normal control eyes (P < .01). Moreover, all RNFL thickness parameters of the GDx VCC software decreased significantly as an exacerbation of diabetic retinopathy (P = .0019, P = .0045, P = .0010 for temporal-superior-nasal-inferior-temporal (TSNIT) average, superior average, inferior average, respectively). The nerve fiber indicator also increased significantly (P < .0001), despite an absence of glaucomatous optic nerve damages. CONCLUSION: The RNFL thickness in type 2 diabetes mellitus, which was measured by GDx VCC software, significantly decreased with the severity of diabetic retinopathy. The presence of diabetes mellitus can be a source of false-positive results and overestimation of glaucomatous optic neuropathy when eyes are screened with GDx VCC software.     

倍频532nm激光治疗视网膜裂孔89例

目的：观察倍频532nm激光治疗视网膜裂孔的治疗效果。方法：应用倍频532nm激光对89例98眼视网膜裂孔患进行治疗,其中大多数采用全包围式光凝裂孔周围。结果：随访6～30mo,裂孔封闭,视网膜下液吸收97眼,占99％。结论：倍频532nm激光治疗视网膜裂孔方便、组织损伤小、疗效高。     

Initial clinical experience using a diode red laser (670 nm) in the treatment of retinal disease

AIM: To investigate the clinical use of a 670-nm diode red laser in the treatment of a number of retinal conditions. METHODS: In all, 17 eyes of 17 patients were treated for conditions such as proliferative diabetic retinopathy, retinal neovascularization in central retinal vein occlusion, rhegmatogenous retinal lesions and retinal breaks, and prophylactic peripheral retinopexy prior to silicone oil removal after three port pars plana vitrectomy. RESULTS: Regression of neovascularization was observed in all the eyes treated for vascular proliferation at the 3-month follow-up visit. Adhesive pigmented scars were observed in the remaining eyes 1 month after treatment. No major complications were recorded. CONCLUSIONS: In this pilot study, the 670-nm diode laser appears to be a promising modality for laser photocoagulation of the retina.     

OCT和SLP定量检测视网膜神经纤维层的研究进展

研究表明青光眼的视网膜神经纤维层(retinal nerve fiber layer,RNFL)损害早于视野改变。视网膜神经纤维层结构性损害的检测是青光眼早期诊断的重要手段。现代激光及计算机技术可以作为青光眼监测的有效方式。本文对OCT和SLP在RNFL定量检测方面的临床研究进展情况进行了综述。