Michael S. Berlin

Stress wave amplitudes during laser surgery of the cornea

PURPOSE To determine the stress wave amplitudes generated during photoablation of the cornea using an argon fluoride excimer laser. DESIGN Experimental study using porcine eyes. METHODS Profiles of the stress wave amplitudes and enucleated human eyes along the axis of symmetry of porcine eyes and enucleated human eyes were measured using a miniature piezoelectric transducer. The ablation parameters, fluence, and ablation diameters were varied within the range of clinical application. MAIN OUTCOME MEASURES Stress wave amplitudes generated during photoablation. RESULTS The stress waves pass through a pressure focus located in the posterior lens and anterior vitreous, where amplitudes of up to 100 atm were measured with a 6-mm or larger ablation zone. Posterior to this focus, the stress wave amplitudes rapidly decrease to less than 10 atm at the retinal site. Small diameter excimer laser spots (< or =1.5 mm) produce a declining stress wave with no pressure focus at the lens and anterior vitreous. CONCLUSIONS Stress waves may be potentially hazardous to anterior structures of the human eye, including the corneal endothelium, lens and anterior vitreous face. They peak at the lens and vitreous with a broad beam, but not with small spot laser ablation. At posterior retinal and subretinal structures, they may be considered harmless.

Histopathologic correlation of the three-layered intravascular ultrasound appearance of normal adult human muscular arteries

The purpose of this study was to correlate intravascular ultrasound images from normal peripheral muscular arteries with the microscopic arterial components by using surgical microdissection techniques. There has been uncertainty about the precise anatomic constituents that are represented by the intravascular ultrasound three-layer image in human peripheral arteries. Forty of 66 grossly normal human femoropopliteal arterial segments obtained at autopsy were found to have a three-layered appearance and were subjected to selective surgical microdissection of intima, media, or adventitia. After microdissection, arteries were imaged with a 30 MHz intravascular ultrasound system; two observers blindly reviewed video tapes to assess for the presence or absence of a one-, two-, or three-layered arterial appearance. Removal of internal elastic lamina and/or intima results in a weak but evident inner ultrasound acoustic interface as a result of the media, which is normally echo-lucent. Removal of the adventitia and/or external elastic lamina results in a weak outer ultrasound acoustic interface. Isolated removal of the media does not alter the three-layered ultrasound image. In normal adult human femoropopliteal arteries the inner bright acoustic reflection (layer) is derived from the interface of blood with the intima and internal elastic lamina and the second bright interface (third layer) is from the external elastic lamina and adventitia. The mid-echo-lucent zone is the result of the media. However, any portion of the arterial wall, including muscular media, can act as an acoustic interface.

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

ABSTRACT A 308 nm excimer laser has been used with a fiber delivery system to perform ablation of the human lens. Preliminary results demonstrate the systems 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.

The role of laser sclerostomy in glaucoma surgery.

&NA; With the recent propagation of laser systems for the treatment of glaucoma, we logically seek to understand the rationale for the application of laser energy to glaucoma filtering procedures. If lasers can provide a better means of controlling open‐angle glaucoma than is currently available by the use of medications, topically or orally, or by the currently employed surgical methods, we must then ask‐which lasers and techniques are currently employed to utilize this technology? In particular what is the role of laser sclerostomy in treating glaucoma? What are the advantages and disadvantages of the various lasers, procedures, and techniques for treating glaucoma? What information does it provide us for future applications of laser surgery in glaucoma? This article addresses these issues.

EP3/FP dual receptor agonist ONO-9054 administered morning or evening to patients with open-angle glaucoma or ocular hypertension: results of a randomised crossover study.

Background/aims The novel prostaglandin E (EP) 3 and prostaglandin F (FP) receptor agonist ONO-9054 is effective in lowering intraocular pressure (IOP) in patients with ocular hypertension and open-angle glaucoma when administered once daily. This study compares the effects of morning (AM) versus evening (PM) dosing of ONO-9054 on tolerability and IOP lowering. Methods This was a single-centre, randomised, double-masked, two-sequence, placebo-controlled crossover study in 12 subjects with bilateral primary open-angle glaucoma or ocular hypertension. Two 14-day crossover regimens were separated by a 2-week washout: ONO-9054 (1 drop to each eye) in the morning (07:00) and vehicle in the evening (19:00) and vice versa. IOP was measured multiple times during select days. Ocular examinations also evaluated safety and tolerability. Results Mild ocular hyperaemia, reported by six subjects with PM dosing, was the most frequent adverse event. Mild to moderate dryness was also slightly more frequent after PM dosing. Maximum IOP reduction from baseline occurred on day 2 with decreases from baseline of −7.4 mm Hg (−30.8%) for AM dosing and −9.1 mm Hg, (−38.0%) for PM dosing; after 14 days, mean reduction in IOP was −6.8 mm Hg (−28.6%) for AM dosing and −7.5 mm Hg (−31.0%) for PM dosing. Conclusions PM dosing of ONO-0954 was associated with a slightly increased frequency of mild hyperaemia and mild to moderate dryness. Both dosing schedules provided sustained reduction in IOP. Trial registration number NCT01670266.

Review of laser applications in glaucoma filtering surgery

Laser sclerostomy is currently being evaluated as an approach which can possibly provide a better means of controlling open angle glaucoma than by conventional filtering surgery. This article will introduce various laser systems and their applications in glaucoma filtering surgery.

Increasing healthcare costs: can we influence the costs of glaucoma care?

Purpose of review Despite a decrease in real average growth rates per capita since 2009, healthcare costs continue to rise worldwide. Numerous patient-related and doctor-related factors have contributed to this rise. Glaucoma is the leading cause of irreversible blindness and requires chronic, usually lifelong treatment. As with other chronic diseases, the adherence to prescribed treatment is often low and maybe influenced by the cost of the therapy. The purpose of this review is to seek potential solutions to best control the escalating costs of glaucoma care. Recent findings The studies we selected for this review can be divided into four different categories: costs of diagnostic tests; costs of direct comparisons between drugs or laser and conventional surgery; patient-related factors (such as adherence); and general aspects regarding costs: theoretical models and calculations. Summary It is challenging to find reliable studies concerning this subject matter. As patients are under the umbrellas of variously organized healthcare systems which span different cultures, the costs between countries are difficult to compare. However, one common aspect to lower costs in glaucoma care is to improve patient adherence. Theoretical models with actual patient studies could enable cost reductions by comparing multiple diagnostic and therapeutic scenarios. Video abstract http://links.lww.com/COOP/A22.

NEW DEVELOPMENTS IN GLAUCOMA LASER SURGICAL PROCEDURES

Recent years have seen unprecedented growth in the applications of laser technology in glaucoma. There are now multiple lasers, delivery systems, and techniques that are common in glaucoma diagnostics and surgery. The most popular techniques in glaucoma laser surgery are extensively documented and have changed little since the late 1980s. These include iridectomy, trabeculoplasty, gonioplasty, and trabeculectomy flap suture lysis. In recent years, a large number of new glaucoma laser procedures have been proposed, including goniophotoablation, cyclophotoablation, endocyclophotocoagulation, trabecular ablation, selective laser trabeculoplasty, bleb remodeling, bleb reopening, hyaloidotomy, and sphincterotomy. This review addresses the most promising of these proposed and underdevelopment procedures. Some of these techniques will possibly go the way of goniodiathermy, trabeculopuncture, and sinusotomy, but others may well enter widespread clinical use.

Preliminary results of VISX excimer laser myopic photorefractive keratectomy at Cedars-Sinai Medical Center

Sixty-two eyes underwent excimer laser photorefractive keratectomy (PRK) for the correction of myopia at Cedars-Sinai-Medical-Center. The first group of 12 patients are presented with follow up data of ten months postoperatively. The second group of 50 patients are presented with follow up data of three months postoperatively. An in-depth comparison of pre and postoperative refractive data is presented. Comparisons between pre and postoperative corrected and uncorrected Snellen visual acuities are provided in order to asses the functional visual result of the procedure.