Ophthalmoscopic contact lenses for transpupillary thermotherapy

Abstract

Ophthalmoscopic contact lenses for transpupillary thermotherapy (TTT) must provide effective visualization of retinal treatment sites and transmission of infrared diode laser radiation. Selection and proper use of retinal laser lenses requires knowledge of their lateral magnification, laser beam magnification factor, field of view and resolution. Optical performance is analyzed for Goldmann-type lenses and a series of inverted image lenses of differing magnification. Goldmann lenses have the highest resolution, but inverted image lenses of comparable magnification have 2.5 times or more their field of view. Inverted image lenses of similar magnification can differ in resolution. They require 2-4% more incident laser power to produce the same retinal irradiance as a Goldmann lens, but this difference is small in comparison to other clinical variables. Tilting an ophthalmoscopic contact lens up to 15 degrees causes little distortion in the circularity of the retinal spot formed by a laser beam or difference in retinal irradiance across the spot. Inverted image lenses produce higher anterior segment irradiances than Goldmann-type lenses, but anterior segment injuries are less likely in TTT than conventional visible light, short-pulse retinal photocoagulation because of the comparatively low irradiances used in TTT and the decreased absorption of diode laser infrared radiation in ocular media and melanin.

Histological Effect and Protein Expression in Subthreshold TranspupillaryThermotherapy in Rabbit Eyes

“…6,11,12 For example, using the Goldmann lens and 810-nm radiation, the magnification factor is 1.247 in rabbits but only 1.08 in human eyes. 13 This results in an approximately 33% higher irradiance in human eyes than in rabbit eyes. There- fore, one would expect the tissue effects observed in rabbits to be more pronounced in human eyes using identical laser settings.…”

An innovative and simple method, clinically comparable to high-definition optical coherence tomography in quantifying posterior segment lesions in the retina

“…Magnification of this lens is higher than most of the contact lenses and condensing lenses that are used in evaluating the fundus. [ 22 ]…”

Scanning Laser Ophthalmoscopy and Angiography With a Wide-Field Contact Lens System

“…They produce excellent wide-field images, but since all available retinal detail is in the ophthalmoscopic image produced by their contact ophthalmoscopy lens, 20,21 magnifying that image optically and/or digitally cannot provide the additional detail available in high-resolution, smallerfield fundus camera or SLO images.…”

“…Vortex veins can be localized for guiding subsequent vitreoretinal surgery. Scanning laser ophthalmoscope fields comparable to those of wide-field contact laser lenses 21 can be recorded to facilitate photocoagulation. The wide-field SLO lens increases the utility of high-resolution SLO angiography and provides convenient static and dynamic re- …”

“…Contemporary wide-field contact cameras are independent, computer-automated imaging systems that offer dynamic, 90°to 110°digital images with higher resolution than the original Equator-plus camera. They produce excellent wide-field images, but since all available retinal detail is in the ophthalmoscopic image produced by their contact ophthalmoscopy lens, 20,21 magnifying that image optically and/or digitally cannot provide the additional detail available in high-resolution, smallerfield fundus camera or SLO images.…”