Autoclavable two-piece noncased wide-angle contact lens system for vitrectomy

PURPOSE: To describe an autoclavable wide-angle two-piece noncased contact lens system (two lenses: equatorial and wider-angle lens) for vitrectomy. DESIGN: The inferior lens is made of an autoclavable plastic with a concave contact surface of 7.7 mm and the superior lens is a convex glass lens. The superior lens is mounted on the inferior one to make the lens assembly. RESULT: The equatorial lens has a power of +81 D and a field of view of 80-96 degrees, while the wider-angle lens power is +151 D and the field 110-120 degrees. The lens is kept on the cornea upon a drop of viscoelastic substance. An assistant holds it with a conventional lens holder. The lens is easy to sterilize by autoclaving and does not require expensive gas sterilization or potentially injurious chemical sterilization. CONCLUSION: This lens system provides a panoramic wide-angle view of the retina during vitreous surgery. The autoclaving makes this lens system cost-effective and fast to reuse.     

Advantages of using newly developed quartz contact lens with slit illumination from operating microscope

The purpose of this article is to report the characteristics and advantages of using a newly designed quartz contact lens with slit illumination from an operating microscope for intraocular surgery. The new contact lens is made of quartz. The lens is convex–concave and is used in combination with slit illumination from an operating microscope. The optical properties of quartz make this lens less reflective with greater transmittance. The combination of a quartz contact lens with slit illumination provided a brighter and wider field of view than conventional lenses. This system enabled us to perform bimanual vitrectomy and scleral buckling surgery without indirect ophthalmoscope. Small intraocular structures in the posterior pole or in the periphery were detected more easily. In conclusion, the newly designed quartz lens with slit beam illumination from an operating microscope provided a bright, clear and wide surgical field, and allowed intraocular surgery to be performed more easily.     

A new high-power biconcave contact lens for observation and coagulation tasks of the posterior segment

BACKGROUND: At the present time, positive, wide-angle contact (and preset) lenses, having a large field of view, are widely used for inspecting and irradiating the fundus. They provide a real, inverted image of the fundus, but illuminate only the slit projected. The wide-field they provide (125 degrees ) is considered to be an advantage, but their image inversion and the lack of illumination of the whole field is disadvantageous. Contact lenses of the Goldmann type have a comparably restricted field of view (standard Goldmann: 46 degrees, CGR 3: 53 degrees). They illuminate the whole field inspected, but it is necessary to use internal mirrors when looking at the periphery. MATERIAL: The new contact lens has a lateral magnification of 0.44 and a field of view of 64 degrees. Owing to the prismatics of its biconcave structure, the field of view may be shifted by tilting the lens and/or by induced eye movements, beyond the ora serrata. CONCLUSIONS: The new contact lens CGR4 has an upright field of view of 64 degrees and tilting enables one to reach the equator with very little optical image degradation. The new lens has a negative power of - 139 dioptres. Safety during laser irradiation tasks is increased as compared to positive lenses because the irradiance at the crystalline part is significantly reduced. The lens is made of laser-resistant glass with a refractive index of 1,516 BK 7 (Schott).     

Retinal laser lenses: magnification, spot size, and field of view.

Proper use of ophthalmoscopic contact lenses for retinal photocoagulation requires knowledge of their comparative magnification, spot size, and field of view. We determined these parameters for four commonly used lenses, using data measured from optical components of the lenses and a commonly used photo-coagulator slit-lamp and spot size changer. A Krieger lens has 8% more working field of view and 29% less magnification than a Goldmann lens. A Panfundoscope lens has 84% more working field of view and 24% less magnification than a Goldmann lens. A Mainster lens has 58% more working field of view and 3% more magnification than a Goldmann lens. For Goldmann, Krieger, Panfundoscope, and Mainster lenses, respectively, retinal spot size is 8%, 53%, 41%, and 5% greater than photo-coagulator spot size settings. The field of view of each lens is increased in myopic and decreased in hyperopic patients. Anterior segment irradiance is higher than retinal irradiance for 1000 microns spot size settings with a Panfundoscope or Mainster lens, and this setting should be avoided, especially in patients with hazy ocular media.     

Lightweight autoclavable wide-angle contact lens for vitreous surgery.

The authors describe an autoclavable, self-stabilizing, lightweight wide-angle contact lens for vitrectomy. The lens has two optical pieces with perforated plastic casing to sustain a high temperature (150 degrees C) for autoclaving. The lens has a 106 degrees static and 127 degrees dynamic field of view. The footplates and reduced weight (2.4 grams) due to the plastic casing allow self-stabilization of the lens. The open lens design.with high temperature resistant plastic prevents fogging during autoclaving and surgery. The autoclavable, self-stabilizing, lightweight wide-angle contact lens allows visualization of the peripheral retina during surgery and faster sterilization by autoclaving between surgeries without the disadvantage of lens fogging.     

Two-piece, dual-purpose comprehensive contact lens for vitreous surgery

PURPOSE: To describe a dual-purpose lens that can be used both as a planoconcave direct-image lens and wide-angle lens. This lens provides good resolution, is autoclavable and self-stabilizing. DESIGN: New instrument design. METHOD: This lens has two components (lenses): the inferior element is a modification of the standard, self-stabilizing planoconcave, one-piece acrylic lens with 4 footplates and is used in a similar manner; the superior part is a biconvex glass lens in a high-temperature-resistant plastic casing. The superior plastic casing is screwed on the inferior lens to convert it into a wide-angle lens. The lens is used as a self-stabilizing, planoconcave or wide-angle lens and is sterilized by autoclaving. RESULT: The planoconcave direct-image inferior lens gives a high-resolution image with a field of view of 20 degrees. The wide-angle lens on assembly of the inferior and superior parts gives a static field of view of 80 degrees and a dynamic field of view of 98 degrees. CONCLUSION: The two-piece dual-purpose contact lens is an inexpensive substitute for both planoconcave and traditional wide-angle lens without compromising the stability and quality of the fundus image.     

广角观察系统在现代玻璃体视网膜手术的应用

常规玻璃体视网膜手术是在一组角膜接触镜下完成,术中术者及助手不但需要根据手术部位及手术目的不断地旋转接触镜,而且暴露的视野相当局限。对于存在角膜外伤及其它角膜病变者,常规的手术操作则更加繁琐。因为广角观察系统相比于传统方法具有独特的优点,如立体感强、观察角度广等,所以在临床上的应用越来越广泛,使很多复杂的眼底手术在广角观察系统下顺利完成。本文对广角观察系统在现代玻璃体视网膜手术中的应用发展概况进行介绍。     

Auxiliary lenses in fundus biomicroscopy--a comparison of fields of view

The use of the biomicroscope in fundus examination requires an auxiliary lens to overcome the high focal convergence of the eye. This study presents the results of subjective field of view determinations with a variety of auxiliary biomicroscopy lenses. Direct/mirror view Goldmann type contact lenses demonstrated the smallest field in the range of 25-30 degrees. Indirect view pre-corneal condensing lenses were about twice this amount in their field. Wide field indirect view lenses with contact lens elements (Rodenstock Panfunduscope, Mainster retinal lens, Volk Quadraspheric) range between 85 and 125 degrees d of field. The use of each type of lens in routine and specialized examination of the fundus as well as in photocoagulation are discussed.     

A new high-power biconcave contact lens for observation and coagulation of the posterior segment.

A wide-angle, high-power negative contact lens was designed for observation and coagulation of the retina and choroid. The new contact lens has a lateral magnification of 0.44 and a field of view of 64 degrees. Due to the prismatic of its biconcave structure, the field of view may be shifted by tilting the lens, induced eye movements beyond the equator of the retina, or both. Because only a negative refractive surface is required, optical aberrations are significantly reduced. Safety during laser irradiation tasks is increased compared with the use of positive wide-angle contact lenses because the irradiance of the crystalline lens is significantly reduced.     

Magnification limitations of a contact lens telescope

A contact lens telescope (CLTS) may have some applications as a low vision aid. In certain circumstances, it offers the possibility of a larger field of view and may simplify the optical alignment difficulties of the user who has a central scotoma. Such devices in the past have usually been limited to magnifications of 2X or less. I examined the magnification potential of these devices by using an unusually high contact lens power and measuring the actual visual acuity improvement (functional magnification) achievable by young, normally sighted subjects. The results show the functional magnification to be significantly reduced compared with the theoretical magnification calculated by the afocal telescope magnification formula. This degradation of functional magnification would be expected to be even greater when used by the visually impaired.     

Clinical application of the oxygen transmissibility of powered contact lenses

Stipulation of the oxygen transmissibility (Dk/L) of a contact lens based upon oxygen permeability (Dk) and nominal lens thickness (L) can be misleading since center thickness, average thickness, and hence Dk/L of a contact lens vary with lens power. While earlier confusion regarding determination of Dk has now been resolved, this data has yet to be fully incorporated into a clinically applicable model. We developed a graphical solution describing variations in Dk/L with power for a representative sample of currently available hydrogel and rigid contact lenses. The Dk/L is found to be optimal for lenses of low minus power (approximately -2.50 D). The model presented here will assist practitioners in assessing the potential oxygen performance of different lens designs with respect to a given power. We advocate that lens manufacturers print the average Dk/L on lens packaging, according to the model described in this paper, along with the parameters that are usually stated.     

Autoclavable wide-angle contact lens for vitreous surgery

PURPOSE: To evaluate an autoclavable self-stabilizing wide-angle contact lens for vitrectomy. DESIGN: Observational study. METHOD: The wide-angle contact lens has two lens pieces within a high temperature-resistant (150 C) plastic casing. The inferior lens with footplates is made of acrylic and the superior of glass. During surgery the lens is used as the self-stabilizing wide-angle contact lens with improved stability on the eye. RESULT: The lens enables the surgeon to address the peripheral retina with less dependence on the assistant. The lens is sterilizable by autoclaving. The field of view of the wide-angle lens is 106 degrees static and 127 degrees dynamic view. CONCLUSION: The autoclavable self-stabilizing wide-angle lens reduces the cost and time for sterilization.     

Ophthalmoscopic contact lenses for transpupillary thermotherapy

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.     

Ophthalmoscopic contact lenses for transpupillary thermotherapy

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° 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.     

Optics of wide-angle panoramic viewing system-assisted vitreous surgery

The purpose of the article is to describe the optics of the contact wide-angle lens system with stereo-reinverter for vitreous surgery. A panoramic viewing system is made up of two components; an indirect ophthalmoscopy lens system for fundus image viewing, which is placed on the patient's cornea as a contact lens, and a separate removable prism system for reinversion of the image mounted on the microscope above the zooming system. The system provides a 104 degrees field of view in a phakic emmetropic eye with minification, which can be magnified by the operating microscope. It permits a binocular stereoptic view even through a small pupil (3 mm) or larger. In an air-filled phakic eye, field of view increases to approximately 130 degrees. The obtained image of the patient's fundus is reinverted to form true, erect, stereoscopic image by the reinversion system. In conclusion, this system permits wide-angle panoramic view of the surgical field. The contact lens neutralizes the optical irregularities of the corneal surface and allows improved visualization in eyes with irregular astigmatism induced by corneal scars. Excellent visualization is achieved in complex clinical situations such as miotic pupils, lenticular opacities, and in air-filled phakic eyes.     

Biconcave contact lens for vitreous surgery.

I designed a biconcave floating contact lens used for trans pars plana vitreous surgery. The lens uses the prismatic power of strong optical lenses to bring into view portions of the fundus that otherwise would be difficult to see.     

New contact lens for observation and coagulation of the retina and choroid

The optical performance of a new contact lens for observation and irradiation of the retina and choroid represents a compromise between Goldmann's contact lens and a wide-angle system in regard to magnification, resolution, and size of the field of view.