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Biomedical subjects

M A Mainster

Publications and source records attributed to M A Mainster.

At least 55 records · Page 3Linked to original sources
PubMed1983

Contact lenses for laser applications.

Contact lenses for anterior and posterior segment laser applications are described. Commercially available lenses are classified according to design, application, manufacturer and cost.

Contact Lenses↗
PubMed1983

Potential retinal hazards. Instrument and environmental light sources.

Light can cause retinal damage by mechanical, thermal, or photochemical mechanisms. Mechanical and thermal injury require a very intense light exposure, but photochemical injury is caused by a prolonged exposure to light levels that probably would be well tolerated if experienced only transiently. The existence of photochemical retinal damage has prompted concern about its possible role in macular degeneration, and reexamination of the safety of clinical light sources. An analysis of the potential hazardousness of these light sources is presented, in addition to a review of retinal damage mechanisms, and suggestions for pertinent patient counseling.

Animals↗
PubMed1983

Laser photodisruptors. Damage mechanisms, instrument design and safety.

Short-pulse neodymium: YAG clinical laser systems permit noninvasive incision of transparent intraocular structures. Selection and safe use of these photodisruptors, however, require a limited understanding of certain basic physical principles. These principles are reviewed and applied in a series of optical experiments designed to study the performance and safety of clinical, short-pulse laser systems. The results of these experiments are presented, in addition to an analysis of current and proposed photodisruptors.

Eye↗
PubMed1982

Scanning laser ophthalmoscopy. Clinical applications.

The scanning laser ophthalmoscope (SLO) provides a high-quality television image of the retina using less than 1/1000 of the light required for conventional indirect ophthalmoscopy. The SLO employs a new ophthalmoscopic principle in which a dim laser beam scans across the fundus, and light is collected only from one retinal point at a time. Since the instrument is highly light efficient, illumination levels are comfortable for the patient, and fluorescein angiography can be performed with one tenth of the usual fluorescein dose. Since a continuous, large depth of field view is displayed on the SLO screen and stored on video tape, repeated dynamic inspection of the vitreous, retina and vitreoretinal interface is afforded. In addition, any graphical material that can be displayed on a microcomputer monitor (such as text of video games) can also be impressed on the retinal pattern formed by the sweeping laser beam. The graphical material is thus observed directly by the patient and on the patient's retina by the clinician. Since the exact retinal locus of each point in the graphical material is viewed directly, it is possible to perform perimetry directly on the retina, to measure acuity at arbitrary retinal loci, to study how patients with macular disease use residual functional retina for reading, and to perform distortometry with a retinal (Amsler-type) grid.

Fluorescein Angiography↗
PubMed1982

Macular photocoagulation. Optimal wavelength selection.

Relative merits of different laser wavelengths for macular photocoagulation are analyzed in terms of light scattering and light absorption in hemoglobin, melanin, and macular xanthophyll. Disadvantages of inner retinal damage in the macula caused by the blue-green argon photocoagulators in standard clinical use are discussed, along with advantages of argon green and krypton yellow light. Results of treatment of subretinal neovascularization in disciform macular degeneration are presented. A repetitive treatment, close follow-up protocol was employed with the objectives of closing neovasculature and preserving central visual field. In 74 successive patients treated with monochromatic argon green radiation, neovasculature was closed in 93%, central visual field loss was reduced or stabilized in 76%, and visual acuity was improved or stabilized in 70%. Results were analyzed in terms of location and size of the neovascular membrane, and it was found that best results were obtained with neovascularization farther than 600 microns from the foveola and smaller than 2 mm2. In 17 patients with neovascular membranes more than 600 microns from the foveola, neovasculature was closed in 100%, central visual field loss was reduced or stabilized in 94%, and visual acuity was improved or stabilized in 88%. Similar results were obtained with monochromatic krypton yellow radiation.

Humans↗
PubMed1982

Retinal localization of scotomata by scanning laser ophthalmoscopy.

The scanning laser ophthalmoscope (SLO) system has been modified to permit direct retinal perimetry. A movable pinhole in a retinal conjugate plane furnishes a mapping stimulus whose retinal locus is directly observable on a video image of the fundus. Scotoma maps in patients with macular disease and physiologic scotomata associated with normal optic discs are presented. Clinical applications of the method are discussed.

Humans↗
PubMed1981

Automated variable contrast acuity testing.

The results of clinical trials with a simple system for automating visual acuity measurements are presented. An inexpensive microcomputer: (1) presents acuity targets on a television screen, (2) uses patients' responses entered through a remote response box to control a staircase testing procedure, and (3) prepares a printed record of a patient's mean visual acuity and its standard deviation. The automated method: (1) offers a stable measure of visual performance, (2) provides an immediate analysis of the statistical significance of changes measured in visual acuity from one office visit to the next, and (3) gives results that are in general agreement with conventional chart testing methods when high contrast targets are used on the television screen. In addition, when medium and low contrast targets are used, the automated method provides a variable contrast acuity profile (VCAP), which describes visual performance at contrast levels that are vital to a patient's performance in daily life but not examined in conventional chart testing. VCAPs are measured clinically, and it is shown that the extent that a patient's acuity declines with decreasing contrast cannot be predicted from the patient's high contrast acuity. Automated variable contrast acuity testing is found to provide a simple, reproducible, clinically practicable method of documenting and quantitating the extent of a patient's visual difficulties at medium and low contrasts.

Adolescent↗
PubMed1980

Automated clinical visual acuity testing.

We developed a method for testing visual acuity using a general-purpose microcomputer which displays visual acuity targets on a television monitor, controls a staircase psychophysical testing procedure, and provides a printed record of mean visual acuity and standard deviation. This automated procedure can be used to increase the precision of clinical visual acuity testing and to determine if changes in a patient's visual acuity are statistically significant.

Adolescent↗
PubMed1979

Ophthalmic applications of infrared lasers -- thermal considerations.

An analysis of the thermal response of clear ocular media to infrared laser radiation is presented. It is shown that from a thermodynamic viewpoint, it should be feasible to use infrared lasers in both vitrectomy and thermokeratoplasty. In vitrectomy, temperature elevations from vitreous vaporization with an intraocular CO2 laser probe would be well below retinal damage threshold levels at distances greater than 2 mm from the center of the beam. In thermokeratoplasty, peak temperature elevations could be moved from the corneal epithelium back into the corneal stroma where collagen shrinkage is desired. Other potential applications for infrared lasers are presented, and the value of accurate measurement of the infrared optical properties of ocular media is emphasized.

Cornea↗
PubMed1978

Spectral transmittance of intraocular lenses and retinal damage from intense light sources.

I measured the spectral transmittance of clear polymethylmethacrylate intraocular lenses in the 300- to 700-nm range. The near-ultraviolet transmittance of the polymethylmethacrylate lens was significantly greater than that of the crystalline lens. Therefore, the pseudophakic eye is more susceptible to retinal damage from intense near-ultraviolet light sources than the normal eye. Retinal thermal response of the pseudophakic eye was compared with that of the normal eye for near-ultraviolet radiation, and retinal thermal response to near-ultraviolet radiation was compared with that to visible light for the pseudophakic eye. Additionally, because there was no significant difference between polymethylmethacrylate and crystalline lens in visible and near-infrared transmittance, thresholds for thermal retinal damage at a given wavelength are similar for the pseudophakic and the intact eye in these spectral regions.

Humans↗