S. Melamed

Confocal tomographic angiography of the optic nerve head in patients with glaucoma

PURPOSEnTo demonstrate the superficial and deep blood supply of the optic nerve using a new method, confocal tomographic angiography, which combines two new techniques, confocal laser scanning ophthalmoscopy and indocyanine green angiography, into one system.nnnMETHODSnIn a prospective study using confocal tomographic angiography, we evaluated the correlation between the vascular supply of the optic nerve and that of the visual field in 90 eyes of 49 subjects (25 eyes of 20 subjects with normal visual field and 65 glaucomatous eyes of 39 subjects with visual field defects; 10 subjects each had one eye with normal visual field and one with visual field defects).nnnRESULTSnIn 22 of 25 eyes with a normal visual field, a diffuse microvascular filling pattern of the optic disk area was apparent with no filling defects. The confocal tomographic angiography of 49 of 65 glaucomatous eyes had good correlation with their visual field defect location. In 20 of 27 eyes with superior visual field loss, an inferior vascular filling defect was detected. In 10 of 13 eyes with inferior visual field loss, a superior vascular filling defect was detected. In 10 of 15 eyes with superior and inferior visual field loss, inferior and superior vascular filling defects were detected. Finally, in nine of 10 eyes with total visual field loss, no vascularity of the optic disk could be detected.nnnCONCLUSIONnConfocal tomographic angiography is a new imaging technology that may be applied for the evaluation of the vascular supply of the optic nerve head.

A Comparative Study of Two Dose Regimens of Latanoprost in Patients with Elevated Intraocular Pressure

OBJECTIVEnThe purpose of the study was to determine whether latanoprost (13,14-dihydro-17-phenyl-18,19,20-trinor PGF2a-isopropyl ester), a new prostaglandin analogue that has been found effective in reducing intraocular pressure (IOP) in humans, is equally effective at lower concentrations than those currently employed.nnnDESIGN AND PARTICIPANTSnFifty patients with glaucoma or ocular hypertension were treated in a randomized, crossover, double-masked fashion with 1 drop of latanoprost (50 microg/ml once daily and 15 microg/ml twice daily) in the affected eye(s) for 3 weeks on each concentration. Tonometry was obtained at 8:00, 13:00, and 17:00 hours at baseline (untreated) and after 3 weeks on each concentration. Placebo (a buffer solution of latanoprost eye drop) was administered for complete masking of the study.nnnRESULTSnMean baseline (untreated) diurnal IOP for the entire sample was 24.7 mmHg. Intraocular pressure was reduced by 6.1 mmHg with latanoprost 15 microg/ml twice daily, and by 7.5 mmHg with 50 microg/ml once daily. Results with both regimens were significant (P < 0.001 each, Students t-test). However, the 50 microg/ml dose was significantly more effective than the 15 microg/ml dose, with a difference of 1.4 mmHg (P < 0.001, ANOVA). Both dose regimens were well tolerated, with little, predominantly mild, ocular discomfort. The higher dose did not cause more hyperemia at 3 weeks than the lower one, i.e., the lower dose yielded a slightly higher score (1.8 mm) on the visual analogue scale (P < 0.29, ANOVA).nnnCONCLUSIONSnLatanoprost administered at a concentration of 50 microg/ml once daily effectively reduces IOP in patients with elevated IOP. Administration of a lower concentration (15 microg/ml) twice daily is less effective, but still significant.

Phase-space beam summation for time-harmonic and time-dependent radiation from extended apertures: 3-D formulation

This paper is concerned with a general mathematical framework for the modeling and analysis of pulsed radiation from an extended source distribution. The radiated field is expressed as a continuous superposition of pulsed beam (PB) propagators which emanate from all points in the source plan and in all directions and initiation times. This phase-space distribution of PB is matched rigorously to the given time-depended source distribution via the new local Radon transform, which extracts the local space-time spectral (directional) properties of the source distribution. The representation integral emphasizes a priori the local radiation properties of the source distribution, thereby improves numerical efficiency and enhances physical interpretation. The basic concepts have been introduced recently for two-dimensional configurations. The present paper extends the representation to three dimensions, derives expressions for relevant transforms and propagators and discusses the additional phenomena introduced by the three dimensionality. This phase-space formulation should be contrasted with the alternative Hermite pulsed beam expansion scheme presented elsewhere in this issue, which applies only for well collimated radiation.

CO2 Laser-Assisted Deep Sclerectomy

CO2 laser-assisted deep sclerectomy (CLASS) is a procedure which enables an accurate dissection of the scleral wall and unroofing of the Schlemm’s canal by utilizing the unique physical properties of the CO2 laser and its ability to ablate dry tissue with almost complete absorption of the energy by percolating aqueous humor. By this, it protects deeper tissues like the trabecular meshwork from the laser energy and avoids penetrating the anterior chamber (making this procedure practically an extraocular procedure). It has an excellent safety and efficacy profile and enables the surgeon and patient to enjoy the advantages of a procedure with a very short learning curve.

Incisional Therapies: Trabeculectomy Surgery

Trabeculectomy with an antimetabolite is considered the “gold standard” for the surgical management of glaucoma. Surgical management for glaucoma was first described in 1857 by Von Graefe, who reported that by removing a large piece of the iris he could help many patients with glaucoma. In 1909, Elliot described a full-thickness filtering procedure by using a trephine to make an anterior sclerectomy under a conjunctival flap, coupled with a peripheral iridectomy. Uncontrolled transclerostomy flow with resulting hypotony was the trigger for most surgeons to switch from full-thickness sclerostomy to a partial-thickness fistula. The guarded fistula was first suggested in 1961 by Sugar but was only published in 1968 by Cairns. The obstruction of the aqueous humor was assumed to be at the juxtacanalicular portion of the trabecular meshwork, and the outflow system distal to the juxtacanalicular meshwork (primarily Schlemm’s canal and the distal collector channels) was thought to be normal in patients with glaucoma. Therefore, the primary goal of the trabeculectomy was to eliminate the obstruction to aqueous humor outflow at the inner aspect of Shlemm’s canal (Figs. 65.1 and 65.2).

Giant-pulse Nd:YAG laser sclerostomy: preliminary results

Laser sclerostomy is a surgical procedure which allows the formation of fistula associated with minimal tissue disturbance. Properly delivered laser energy can create functional sclerostomy, with minimal surrounding damage. Moreover, the laser is transmitted via fibers that cause minimal conjunctival disturbance while inserted beneath the conjunctiva to reach the intended sclerostomy site. At present, clinical experience using these lasers to create sclerostomies in humans is limited both in terms of number of eyes and extent of follow up, yet the overall success rate of all the lasers is clearly inferior to that typically achieved with trabeculectomy.