Mark A. Latina

Selective targeting of trabecular meshwork cells: in vitro studies of pulsed and CW laser interactions.

The purpose of the present study was to selectively target pigmented trabecular meshwork cells without producing collateral damage to adjacent non-pigmented cells or structures. The ability to selectively target trabecular meshwork cells without coagulation, while preserving the structural integrity of the meshwork, could be a useful approach to study whether the biological response of non-coagulative damage to the trabecular meshwork and trabecular meshwork cells is similar to that seen with coagulative damage to the trabecular meshwork which occurs with argon laser trabeculoplasty. This approach also may be useful to non-invasively deplete trabecular meshwork cells while preserving the structural integrity of the trabecular meshwork in an animal model. A mixed cell culture of pigmented and non-pigmented trabecular meshwork cells were irradiated with Q-switched Nd-YAG and frequency-doubled Nd-YAG lasers, microsound pulsed dye-lasers, and an argon ion laser in order to define a regime where laser absorption would be confined to pigmented trabecular meshwork cells, thereby permitting selective targeting of these cells without producing collateral thermal damage to adjacent non-pigmented cells. Pulse durations ranged from 10 nsec to 0.1 sec. A fluorescent viability/cytotoxicity assay was used to evaluate laser effects and threshold energies, and cells were examined morphologically by light and TEM. Selective targeting of pigmented trabecular meshwork cells was achieved with pulse durations between 10 nsec and 1 microsec and 1 microsec without producing collateral thermal or structural damage to adjacent non-pigmented trabecular meshworks cells when examined by light and transmission electron microscopy. Pulse durations greater than 1 microsec resulted in non-selective killing of non-pigmented trabecular meshwork cells. Threshold radiant exposures were as low as 18 mJ cm-2, and increased at longer wavelengths, longer pulse durations and lower melanin contents within the cells. It is concluded that selective targeting of pigmented trabecular meshwork cells can be achieved using pulsed lasers with low threshold radiant exposures avoiding collateral thermal damage to adjacent non-pigmented trabecular meshwork cells. This approach can be readily applied in vivo.

Clinical Experience with the Baerveldt Glaucoma Drainage Implant

PURPOSE To assess clinical outcomes in patients who were treated with the Baerveldt glaucoma drainage implant. METHODS The authors performed a retrospective multicenter study of 100 patients (103 eyes) with medically uncontrollable glaucomas who underwent a one-stage implantation with either the 200-, 250-, 350-, or 500-mm2 Baerveldt implant. The authors defined surgical success as 5 mmHg less than intraocular pressure less than 22 mmHg without additional glaucoma surgery and without loss of light perception. RESULTS With a mean follow-up of 13.6 +/- 0.9 months (range, 4-37 months), 74 eyes (71.8%) had successful outcomes. Cumulative life-table success rates were 90.3% at 3 months (n = 103), 72.6% at 6 months (n = 84), and 60.3% at 24 months (n = 34). Intraocular pressure (IOP) was reduced from a mean of 38.5 +/- 1.4 mmHg with 2.2 +/- 0.1 antiglaucoma medications to 15.1 +/- 0.8 mmHg (P < 0.0005) with 0.5 +/- 0.1 antiglaucoma medications (P < 0.0005). Visual acuity was improved or remained within one line of the preoperative visual acuity in 90 eyes (87.4%). Complications occurred in 74 eyes (71.8%). A significant portion of these complications (45%) was transient, resolving without any intervention. Only 8% were serious sight-threatening complications. The most common complications included shallow anterior chamber or hypotony (32%), choroidal effusion or hemorrhage (20.4%), corneal decompensation or edema (17.5%), hyphema (14.1%), and tube obstruction (12.6%). CONCLUSION The Baerveldt implant is effective in lowering the IOP in patients with intractable glaucomas. Hypotony and other complications are common, which also have been reported in other nonvalved glaucoma drainage implants. However, the majority of these complications did not affect surgical outcome.

Selective cell killing by microparticle absorption of pulsed laser radiation

The mechanism of interaction between subcellular pigment microparticles and short pulse laser radiation was investigated with nanosecond time-resolved microscopy and fluorescence microscopy. Stroboscopic illumination was used to capture images of transient events induced in cells by laser pulses. Fluorescence microscopy enabled assessment of cell damage using fluorescent probes. Short-lived intracellular cavitation bubbles were directly visualized within nanoseconds after laser irradiation. Microbubble expansion and implosion took place on the timescale of 0.1-1 /spl mu/s and were confined entirely within pigmented cells with remarkable selectivity. Cells containing particles underwent cavitation and rapidly lost viability, while adjacent cells without particles remained viable. Nonpigmented cells can be targeted by labeling them with absorbing particles. Laser-pumped microparticles provide an efficient means of selective cell targeting.

Contact Transscleral Nd:YAG Laser Cyclophotocoagulation: Midterm Results

BACKGROUND Early reports of both contact and noncontact transscleral Nd:YAG laser cyclophotocoagulation have been encouraging; however, recent evidence indicates a significant incidence of hypotony, visual loss, and phthisis with the noncontact technique with more than 6 months of follow-up. The authors sought to determine the intermediate term effects of contact transscleral Nd:YAG laser cyclophotocoagulation (CYC). METHODS The authors followed 116 eyes of 114 patients for a minimum of 1 year after treatment of advanced glaucoma with CYC. RESULTS The mean preoperative intraocular pressure (IOP) of 35.0 +/- 1.0 mmHg decreased to 18.6 +/- 1.1 mmHg (P less than 0.0001) during the average follow-up of 19.0 +/- 0.6 months (range, 12 to 36 months). Intraocular pressure control of 3 to 25 mmHg was achieved in 72%, 3 to 22 mmHg in 65%, and 3 to 19 mmHg in 56% of eyes. Retreatment was required in 31 of the 116 eyes (27%). Intraocular pressure decreased to less than 3 mmHg in 9 eyes and to 0 mmHg in 6 of these 9 eyes. Nineteen eyes, all with initial visual acuity of counting fingers or worse, progressed to no light perception; 17 of 36 eyes (47%) with visual acuity of 20/200 or better lost 2 or more Snellen lines. CONCLUSION Midterm results of CYC continue to be encouraging but are tempered by a nearly 10% incidence of hypotony or phthisis and the progression of visual loss.

Selective laser trabeculoplasty: a new treatment option for open angle glaucoma.

Selective laser trabeculoplasty (SLT) is a safe and effective treatment modality for lowering the intraocular pressure in patients with open angle glaucoma. The preservation of the trabecular meshwork architecture and the demonstrated efficacy in lowering intraocular pressure makes the SLT a reasonable and safe alternative to argon laser trabeculoplasty. In addition, SLT is a potentially repeatable procedure because of the lack of coagulation damage to the trabecular meshwork and the demonstrated efficacy in patients with previously failed argon laser trabeculoplasty treatment. Furthermore, SLT can be considered as a primary treatment option in patients who cannot tolerate or are noncompliant with their glaucoma medications, while not interfering with the success of future surgery. Due to its nondestructive properties and low complication rate, SLT has the potential to evolve as an ideal first-line treatment in open angle glaucoma.

Neovascular Glaucoma: Etiology, Diagnosis and Prognosis

Neovascular glaucoma (NVG) is a severe form of glaucoma with devastating visual outcome attributed to new blood vessels obstructing aqueous humor outflow, usually secondary to widespread posterior segment ischemia. Invasion of the anterior chamber by a fibrovascular membrane initially obstructs aqueous outflow in an open-angle fashion and later contracts to produce secondary synechial angle-closure glaucoma. The full blown picture of NVG is characteristized by iris neovascularization, a closed anterior chamber angle, and extremely high intraocular pressure (IOP) with severe ocular pain and usually poor vision.

Neodymium:YAG Laser Trabeculopuncture in Juvenile Open-Angle Glaucoma

The authors performed neodymium:YAG (Nd:YAG) laser trabeculopuncture (YLT) in eight eyes of six patients with uncontrolled juvenile open-angle glaucoma. Two methods of treatment were evaluated: either two confluent trabeculotomies, each 1 clock hour in extent; or focal treatment in four quadrants. In six eyes (75%), the intraocular pressure (IOP) was controlled (less than or equal to 19 mmHg) after a mean follow-up period of 6 +/- 2 months. All successful treatments were associated with blood reflux from the site of trabeculopuncture into the anterior chamber at the time of the procedure. Energy levels required for a single trabeculotomy (1 clock hour in extent) and for one focal trabeculopuncture, were 156 +/- 59 mJ and 42 +/- 24 mJ, respectively. The clinical results suggested that confluent trabeculotomy may be superior to focal treatment. No major complications were encountered with either treatment. The authors propose the use of YLT in uncontrolled juvenile glaucoma before surgically invasive goniotomy or filtration operations.

A Comparison of the Intervisit Intraocular Pressure Fluctuation After 180 and 360 Degrees of Selective Laser Trabeculoplasty (slt) as a Primary Therapy in Primary Open Angle Glaucoma and Ocular Hypertension

ObjectiveTo determine and compare the effect of 180 and 360 degrees of selective laser trabeculoplasty (SLT) treatment as a primary therapy on the intervisit intraocular pressure (IOP) fluctuation in patients followed up for a period of 2 years without any further medical or surgical intervention. MethodsRetrospective chart review of patients with ocular hypertension and primary open angle glaucoma who received SLT as primary therapy without any subsequent medical or surgical intervention. IOP before SLT and postlaser IOP at all the visits during the follow-up period of months 6 to 24 was determined. The standard deviation (SD) of the mean IOP was used as a surrogate for IOP fluctuation. ResultsForty-one eyes were treated by SLT, 19 eyes in the 180-degree group and 22 eyes in the 360-degree group. The mean reduction in IOP at 2 years was 28% in 180-degree group and 35% in 360-degree SLT group. After the SLT, the 360-degree SLT group had a lower IOP fluctuation compared with the 180-degree SLT group over the follow-up period of months 6 to 24. The percentage of eyes with intervisit IOP fluctuation (SD) ≤2 mm Hg during the same follow-up period was significantly greater in 360-degree SLT treatment group (86%) than in the 180-degree SLT treatment group (52%), P=0.03. The odds of achieving IOP fluctuation ≤2 mm Hg were 5.7 times greater with 360 degrees than with 180-degree SLT during the follow-up period of months 6 to 24. ConclusionsThis study suggests that 360-degree SLT is more efficacious in achieving smaller IOP fluctuations than treatment with 180-degree SLT.

Long-term safety and efficacy of selective laser trabeculoplasty as primary therapy for the treatment of pseudoexfoliation glaucoma compared with primary open-angle glaucoma

Purpose To investigate the safety and efficacy of selective laser trabeculoplasty (SLT) to reduce intraocular pressure (IOP) in patients with pseudoexfoliation glaucoma (PXFG) compared with primary open-angle glaucoma (POAG). Design Non-randomized, prospective, clinical trial. Methods Nineteen eyes of 13 patients with POAG and 18 eyes of 13 patients with PXFG were treated with SLT. Patients were followed without antiglaucoma medications until additional medical, laser, or surgical intervention was initiated, at which time they were considered failures, had withdrawn from the study, or underwent a second SLT. Results The POAG and PXFG eyes showed similar reductions of IOP over the 49 months of follow-up. At 30 months of follow-up the POAG group showed a mean IOP of 17.6 ± 2.8 mmHg and a mean IOP reduction of 5.7 ± 2.1 mmHg; the PXFG group showed a mean IOP of 18.3 ± 4.7 and a mean IOP reduction of 5.3 ± 3.0 mmHg. Four eyes in the PXFG group and three eyes in the POAG group failed by 30 months. The cumulative probability of success was 74% for the PXFG group and 77% for the POAG group. Four PXFG eyes underwent a second SLT after 30 months of follow-up with a final IOP of 17.6 ± 2.8 mmHg. There were no serious adverse events. Conclusion SLT is a safe and effective method to lower IOP in patients with PXFG as initial glaucoma therapy. Both groups showed similar IOP reductions and failure rates.

Imaging of optic nerve head drusen: improvements with spectral domain optical coherence tomography.

ObjectiveTo demonstrate a new algorithm that can determine the shape, location, and volume of optic nerve head drusen (ONHD), which were imaged with spectral domain optical coherence tomography (SDOCT). MethodsOne exenteration patient and 4 glaucoma patients with bilateral ONHD were recruited from the Massachusetts Eye and Ear Infirmary and from a private practice office. Images were obtained using an experimental SDOCT system developed at the Wellman Center for Photomedicine, Massachusetts General Hospital. With axial resolutions of about 6 μm, SDOCT can obtain 2-dimensional images in 1/29 of a second, compared with commercially available time domain OCT instruments with 10 μm resolution images in 1.28 seconds. The volumes of ONHD were calculated with a new algorithm and were then correlated with visual field mean deviation. ResultsSDOCT can display 2-dimensional images comparable with histology and 3-dimensional videos of ONHD. ONHD are signal-poor regions with high-signaled borders. Larger ONHD volumes are directly correlated with larger mean deviation absolute values on Humphrey visual field testing. ConclusionsSDOCT is a potentially better technique for ONHD imaging and may improve the diagnosis and management of patients with both OHND and glaucoma.