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.     

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.     

Computerized calculation scheme for bitoric eikonic intraocular lenses

Despite full correction of the corneal astigmatism with toric intraocular lenses, the retinal image is distorted and the lateral image-object magnification is different in different meridians. The purpose of this study is to describe an iteration strategy for tracing an axial pencil of rays through the 'optical system eye' containing astigmatic refractive surfaces with their axes at random to calculate a thick bitoric lens implant which eliminates image distortion. The capabilities of this computing scheme are demonstrated with two clinical examples. We present a mathematically straightforward computer-based strategy for the calculation of thick bitoric eikonic lens implants. The iteration algorithm is initialized with a spherical front and a toric back surface and stepwise decreases the image distortion by adding cylinder lenses to the front lens surface corrected by the toric lens back surface. Total magnification can be modulated by varying the front-to-back surface power of the thick lens.     

Posterior chamber intraocular lens in the anterior chamber

BACKGROUND: The choice of design for intraocular lenses (IOLs) mainly depends on the selected location for the implant. HISTORY AND SIGNS: We report the case of dislocation of a foldable open-loop posterior chamber IOL into the anterior chamber during retinal detachment surgery. After several vitreoretinal interventions visual acuity was hand movements. THERAPY AND OUTCOME: The IOL remained in the anterior chamber without complications such as IOP rise or endothelial decompensation for several years. CONCLUSIONS: Foldable open-loop posterior chamber IOLs can be left in suitable anterior chambers for years without complications such as rise of intraocular pressure or corneal endothelial damage. Repeated measurements of endothelial cell density can provide an informative basis for the operative removal of this lens.     

Image size magnification and power and dilation factors for optical instruments in general

Traditional treatments of spectacle magnification for distant objects consider only stigmatic spectacle lenses and they compare the retinal image size in a refractively fully compensated eye with the image size in the uncompensated eye. Spectacle magnification is expressed as a product of two factors, the power and shape factors of the lens. The power factor depends on the position of the entrance pupil of the eye. For an eye with an astigmatic cornea, however, the position of the entrance pupil is not well defined. Thus, the traditional approach to spectacle magnification does not generalize properly to allow for astigmatism. Within the constraints of linear optics and subject to the restriction that the eye's iris remains the aperture stop, this paper provides a complete, unified and exact treatment for optical instruments in general. It compares retinal image size in a generalized sense (including image shape and orientation) for any instrument in front of an eye with that of the eye alone irrespective of whether the instrument compensates or not. The approach does not make use of the concept of the entrance pupil at all and it allows for astigmatism and for non-alignment of refracting elements in the instrument and in the eye. The concept of spectacle magnification generalizes to the concept of instrument size magnification. Instrument size magnification can be expressed as the product of two matrix factors one of which can be interpreted as a power factor (as back-vertex power) and the other factor for which the name dilation factor is more appropriate in general. The general treatment is then applied to a number of special cases including afocal instruments, spectacle lenses (including obliquely crossing thick bitoric lenses), contact lenses, stigmatic systems and stigmatic eyes. In the case of spectacle lenses, the dilation factor reduces to the usual shape factor.     

Image quality in wearers of a centre distance concentric design bifocal contact lens

The optical performance of eyes wearing bifocal concentric contact lens was studied using the double-pass technique. Retinal image quality was measured for four subjects wearing CIBA Bisoft contact lenses presenting the central zone for correcting distance vision. Lenses with two different central optic zone diameter (COZD), 3.2 and 3.8 mm, were studied and the influence of pupil diameter and viewing distance were analysed. Results show that the best optical performance is obtained for far vision conditions when no lens is worn even if the pupil coverage by the COZD is complete. For near vision conditions, the optical performance when the lens is worn is, in general, better than when no lens is worn. When the lens is worn the best optical performance corresponds to a pupil diameter of 3 mm and far vision conditions. For this pupil diameter, variations in the situations analysed can be explained by changes in the percentage of pupil coverage corresponding to the far or the near vision zone of the lens. For a pupil diameter of 5 mm, the retinal image quality is more similar in all situations studied and pupil coverage alone cannot explain the results obtained and the influence of other parameters related to the design or contact lens fitting characteristics must be considered.     

Effects of myopic correction by replacement of spectacles, laser in situ keratomileusis, and phakic intraocular lens implantation on modulation transfer function and retinal magnification

PURPOSE: To compare the modulation transfer function and the retinal magnification after myopic correction by replacement of spectacles, laser in situ keratomileusis (LASIK), or phakic intraocular lens (phakic IOL) implantation. MATERIALS AND METHODS: Using the ray tracing method, we measured the modulation transfer function and the retinal magnification after these myopic corrections in a Gullstrand eye model. RESULTS: The modulation transfer function (3-mm pupil, 100 cycles/mm) after phakic IOL implantation for the correction of low, moderate, and high myopia was 45%, 44%, and 44%, respectively. These same measurements after LASIK were 50%, 47%, and 46%, respectively, and the same measurements after spectacle correction were 41%, 32%, and 21%, respectively. The retinal magnification was least changed by the amount of myopic correction after phakic IOL implantation, more changed by LASIK, and most changed by spectacle correction. Specifically, the improvement in the retinal magnification after phakic IOL implantation, LASIK, and spectacle correction for the correction of high myopia was 1.00, 0.97, and 0.88 times, respectively. CONCLUSIONS: There were no significant differences in the modulation transfer function after phakic IOL implantation and LASIK. On the other hand, the modulation transfer function was significantly decreased after spectacle correction, especially when the amount of myopic correction was large. The retinal magnification was least affected by phakic IOL implantation, more affected by LASIK, and most affected by spectacle correction. Phakic IOL implantation and LASIK are considered to be optically excellent correction methods.     

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。     

Dynamic simulation of the effect of soft toric contact lenses movement on retinal image quality.

PURPOSE: To report the development of a tool designed to dynamically simulate the effect of soft toric contact lens movement on retinal image quality, initial findings on three eyes, and the next steps to be taken to improve the utility of the tool. METHODS: Three eyes of two subjects wearing soft toric contact lenses were cyclopleged with 1% cyclopentolate and 2.5% phenylephrine. Four hundred wavefront aberration measurements over a 5-mm pupil were recorded during soft contact lens wear at 30 Hz using a complete ophthalmic analysis system aberrometer. Each wavefront error measurement was input into Visual Optics Laboratory (version 7.15, Sarver and Associates, Inc.) to generate a retinal simulation of a high contrast log MAR visual acuity chart. The individual simulations were combined into a single dynamic movie using a custom MatLab PsychToolbox program. Visual acuity was measured for each eye reading the movie with best cycloplegic spectacle correction through a 3-mm artificial pupil to minimize the influence of the eyes' uncorrected aberrations. Comparison of the simulated acuity was made to values recorded while the subject read unaberrated charts with contact lenses through a 5-mm artificial pupil. RESULTS: For one study eye, average acuity was the same as the natural contact lens viewing condition. For the other two study eyes visual acuity of the best simulation was more than one line worse than natural viewing conditions. CONCLUSIONS: Dynamic simulation of retinal image quality, although not yet perfect, is a promising technique for visually illustrating the optical effects on image quality because of the movements of alignment-sensitive corrections.     

Centurion白内障智能超声乳化手术系统处理晶状体半脱位的临床观察

目的 评价晶状体半脱位白内障超声乳化术中应用Centurion白内障智能超声乳化手术系统的安全性和有效性.方法 回顾性分析15眼晶状体半脱位患者,应用Centurion白内障智能超声乳化手术系统的效果,观察术后视力、眼压、角膜内皮细胞计数、黄斑中心凹视网膜厚度、人工晶状体位置及术中、术后并发症发生情况.结果 术后3个月,10眼(66.7％)最佳矫正视力≥0.6,其余5眼最佳矫正视力≥0.2 ～0.6,矫正不良的主要原因是由高度近视或外伤所致的黄斑病变.术后角膜内皮细胞计数及黄斑中心凹视网膜厚度与术前比较差异均有统计学意义(均为P ＜0.05),术后3个月复查均未发现视网膜脱离、人工晶状体脱位、脉络膜上腔出血、黄斑囊样水肿等严重并发症.结论 应用Centurion白内障智能超声乳化手术系可安全、有效地完成晶状体半脱位的超声乳化手术,避免玻璃体视网膜并发症的出现.     

Retinal laser optical aids.

Knowledge of optics, comparative magnification and working field of view is essential for rational use of ophthalmoscopic contact lenses for retinal photocoagulation. The three commonly used contact lenses are described and compared.     

Quality of image of grating target placed in vitreous of isolated pig eyes photographed through different implanted multifocal intraocular lenses

Purpose: To determine the quality of the image of a grating target placed in the vitreous of isolated pig eyes and photographed through implanted refractive and diffractive multifocal intraocular lenses (IOL). Methods: Refractive multifocal (NXG1, PY60MV), diffractive multifocal (ZM900, SA60D3) and monofocal (SA60AT, ZA9003) IOL were implanted in the capsular bag of isolated pig eyes. A grating target was placed in the vitreous and photographed through a flat or a wide‐field viewing contact lens. The contrast of the grating targets of different spatial frequencies was measured. Results: With the flat corneal contact lens, the gratings appeared clear and not distorted when viewed through the optics of the NXG1 and PY60MV for far vision but were distorted with reduced contrast when viewed through the optical zone for near vision. The images through the diffractive zone of the ZM900 and SA60D3 were more defocused than with the monofocal IOL (p < 0.005). Ghost images oriented centrifugally of the original image were seen with the ZM900 resulting in lower contrast at higher spatial frequencies than with the SA60D3 with less defocused images only in the central area. With the wide‐field viewing contact lens, the images were less defocused and the contrast was comparable to both refractive and diffractive multifocal IOL. Conclusion: Both refractive and diffractive multifocal IOL reduced the contrast of the retinal image when viewed through a flat corneal contact lens but less defocused when viewed through a wide‐field viewing contact lens.     

Comparison of the AcrySof IQ aspheric blue light filter and the AcrySof SA60AT intraocular lenses

PURPOSE: The development of aspheric intraocular lenses (IOL) designed to compensate for the positive spherical aberration of the cornea has been shown to improve the image quality of pseudophakic eyes. This prospective clinical study compared an aspheric IOL with a blue light filter (AcrySof IQ) with its spherical platform--the SA60AT IOL with conventional optic. METHODS: After uneventful phacoemulsification, 42 and 20 eyes were implanted with the AcrySof IQ aspheric lens and the SA60AT, respectively. Six weeks after surgery, higher order aberrations, visual acuity, contrast sensitivity, depth of focus, pupil size, and corneal asphericity were assessed. RESULTS: Visual acuity was good with both IOLs. A significant difference was found regarding spherical aberration. Mean values of spherical aberration, calculated for a 5-mm pupil were 0.20 +/- 0.06 microm with the SA60AT and 0.04 +/- 0.05 microm with the AcrySof IQ lens. Contrast sensitivity was significantly superior in the AcrySof IQ group in 7 of 15 measurement conditions. Asphericity of the cornea proved to be correlated with postoperative ocular spherical aberration. CONCLUSIONS: The aspheric optic design of the AcrySof IQ results in significant reduction of postoperative ocular spherical aberration and improved contrast vision. Measuring the corneal asphericity allows estimation of postoperative ocular spherical aberration.     

人工晶体脱入玻璃体腔的手术处理

探讨后房型人工晶体后脱一段玻璃体腔的处理方法。方法对１５例人工晶体严重后位的患者玻璃体手机加人工晶体取出术;玻璃体手术加全氟化碳液人工晶体取出术;玻璃体手术加工人晶体取出及人工晶体睫状沟固定等手术,观察手术疗效及并发症。     

Sclerally fixated intraocular lens implant associated with vitrectomy: a study of 50 cases

INTRODUCTION: We present a retrospective study of 50 cases of scleral fixation of intraocular lenses (IOLs) associated with vitrectomy. MATERIALS AND METHODS: From January 1996 to June 2001, 50 consecutive patients who underwent surgery with insertion of a sclerally fixated intraocular lens implant associated with vitrectomy were studied. Indications included luxated lenses due to ocular contusion, cataract surgery complicated by capsular rupture and luxated nucleus or implant into the vitreous, and replacement of anterior chamber lenses. The implant was sutured 2 mm behind the limbus into the scleral sulcus with 10.0 Prolene. Vitrectomy was performed to treat pre-existing maculopathy, remove the lens or lens fragments luxated into the vitreous or to remove a luxated implant, and to provide for complete retinal examination during the operation. RESULTS: With a mean follow-up of 30 months, the mean postoperative visual acuity was 20/30. For 95% of cases, final visual acuity was improved compared to preoperative visual acuity. No postoperative complications due to the implant were encountered. There were four cases of cystoid macular edema and two cases of retinal detachment. DISCUSSION: Despite the macula edema and retinal detachments, there was no loss of visual acuity compared to the preoperative state. There were eight cases of raised intraocular pressure; seven were controlled medically and one after hemi-cyclocryo-therapy. CONCLUSIONS: Scleral fixation of an IOL is a reliable means of correcting aphakia in the absence of capsular support and may be associated with a vitrectomy with very little risk.     

Image formation in fundus cameras.

Imaging in a fundus camera depends more on design of the system than on correction of the first fundus image as formed by the ophthalmoscopic lens. We show here that the designer may use the free parameters of the ophthalmoscopic lens (contact or noncontact) to correct the latter for observation and illumination of the fundus. In both contact and noncontact systems the fundus is illuminated by forming a ring of light on the patient's cornea around a central area (the corneal window) reserved for observation. On the first surface of the crystalline lens, the light also forms a ring which must accomodate the total entrance pupil (TEP) of the observation system in its middle and which is limited on the outside by the patient's iris. The restrictions that result from this situation define the entrance pupil of the bundle of rays that image the marginal point of the retina. The limits of this bundle are imposed by the choice of the angular field of view and by the size of the patient's pupil.     

Optical performance of multifocal intraocular lenses

The optical performance of one monofocal and five multifocal lenses was evaluated in the laboratory and photographically. The laboratory testing included determination of the modulation transfer function (MTF), through focus response (TFR), resolution efficiency, and Strehl ratio of each lens. The photographic testing included photographs of the Regan high contrast acuity chart at ten feet with clearest focus and 18 additional photographs in which the image was defocused using minus trial lenses in 0.25 diopter increments. A color photograph of the Kodak color chart was also taken using each lens. All testing was conducted using a 3 mm artificial pupil under ideal implant conditions with no decentration or tilt. The laboratory and photographic results demonstrate that all the multifocal lenses had a two- to three-fold increase in the depth of field with at least a 50% lower contrast in the retinal image. The photographic testing revealed a one to two line better resolution limit with the monofocal lens, which corresponded to the 12% to 41% better MTF cut-off value with the monofocal lens by laboratory testing. The measured resolution efficiencies of all six lenses were comparable. The color photographs revealed color mixing of adjacent colors with the multifocal lenses, whereas the colors appeared unchanged from the original with the monofocal lens.     

人工晶状体植入术后视网膜脱离的手术治疗

目的探讨人工晶状体植入术后视网膜脱离的手术方法并评价其疗效。方法2000年1月～2002年6月经玻璃体视网膜联合术治疗人工晶状体植入术后视网膜脱离31例(31眼)的临床资料作回顾分析。手术采取玻璃体切除、剥离视网膜前膜、激光封闭视网膜裂孔及眼内长效气体或硅油填充等方式。结果随访期为12～39月，平均22月。随访时视网膜复位29眼，占93．55％。有27眼(占87．11％)视力提高，其中≥0．1者22眼，最好视力为0．8。结论人工晶状体植入术后视网膜脱离使眼内病变复杂，易致严重PVR。应用玻璃体视网膜联合术，可使视网膜得以有效复位。     

Anterior chamber intra ocular lens implantation

The role of A.C. IOL in modern implant surgery has become somewhat debatable, since, the choice procedure to day is undoubtedly an ECCE with a PC lens implant preferably in the capsular bag. Even so, anterior chamber lens implantation has its definite indications. As such it is necessary for the implant surgeon to be familiar with the latest technique in this modality of surgery as well. Many of the complications of earlier rigid model AC IOLs were mainly due to defective lens design. With the advent of new generation flexible one-piece PMMA AC lenses, many of these complications have been eliminated. A.C. IOL implantation, although less frequently done now, has its own legitimate place in modern IOL surgery.