New gonioscopy system using only infrared light

PURPOSE: To describe an infrared gonioscopy system designed to observe the anterior chamber angle under natural mydriasis in a completely darkened room. METHODS: An infrared light filter was used to modify the light source of the slit-lamp microscope. A television monitor connected to a CCD monochrome camera was used to indirectly observe the angle. RESULTS: Use of the infrared system enabled observation of the angle under natural mydriasis in a completely darkened room. CONCLUSION: Infrared gonioscopy is a useful procedure for the observation of the angle under natural mydriasis.     

基于红外成像原理的睑板腺图像量化分析系统

目的:分析人眼的睑板腺形态学特征,探索睑板腺分析系统在眼表疾病的应用研究.方法:中山眼科中心入组正常受试者24例(42眼),进行睑板腺红外摄影.选取受试者中的10例(20眼)在同型号的设备上由二名操作员分别进行睑板腺红外摄影.图像通过自行设计的分析软件对上睑结膜中央5条腺体形态学参数进行定量分析,对数据进行重复性测试....     

Comparison of scotopic pupil measurement with slitlamp-based cobalt blue light and infrared video-based system

PURPOSE: To determine the accuracy and reproducibility of scotopic pupil measurements with a slitlamp-based cobalt blue light. SETTING: University of Texas Health Science Center-San Antonio, San Antonio, Texas, USA. METHODS: In a prospective experimental study, 2 independent observers measured 16 subjects' pupils with a standard slitlamp-based cobalt blue light. In the same setting, the accuracy and reproducibility of the measurements were compared with those obtained with an infrared video-based system. RESULTS: Measurements of pupil size using the infrared video-computer system were highly reproducible. With the slitlamp-based cobalt blue light, the 2 measurements obtained by observer 2 (n = 16) were very close to each other (mean difference 0.09 mm +/- 0.23 [SD]; P =.12), whereas those obtained by observer 1 (n = 16) were slightly different from each other (mean difference 0.18 +/- 0.33 mm; P =.043). The mean pupil diameter measured with cobalt blue light was not significantly different between the 2 observers (P >.05), and the measurements were highly correlated with each other (r = 0.96, P <.01). The mean difference between the measurements using cobalt blue light and the infrared video-computer system was 0.21 +/- 0.54 mm for observer 1 (P =.47) and 0.06 +/- 0.47 mm for observer 2 (P =.85). Good correlation was noted between the measurements taken from each measuring device for both observers (r = 0.87 and 0.90, P <.01). CONCLUSIONS: Slitlamp-based cobalt blue light provided a reasonably good measurement of scotopic pupil size. It correlated well with the infrared video system when used at the lowest setting by experienced personnel. However, the observed difference between the measurements obtained by the 2 devices indicates that the cobalt blue light should be used cautiously in the refractive surgery preoperative evaluation of patients with large pupils.     

蓝光滤过型人工晶状体的多色光高阶像差研究

目的 比较蓝光滤过型人工晶状体(IOL)与普通透明IOL多色光入射高阶像差,尤其是球差的大小.方法 实验研究.选取Alcon公司的+20D蓝光滤过型IOL(SN60AT)置于模型眼中,由短、中、长3个波段光源出射光分别通过模型眼光路成点阵图像,利用matlab程序分析得到Zemike多项式的7阶36项像差,取高阶像差进行分析,进一步得到调制传递函数(MTF)和点扩散函数(PSF),利用以上结果分析SN60AT IOL的色像差.选取+20D的透明IOL(SA60AT)做对照,比较2种IOL的高阶色像差.结果 蓝光滤过型IOL在486 nm成像时,MTF曲线在各个频率均低,在546 nm对焦时PSF图显示差别最小;蓝光滤过型IOL较透明IOL多色光高阶像差小,特别是球差更小,有显著差别.结论蓝光滤过型IOL较普通透明IOL多色光高阶像差、尤其是球差小,故成像质量较好.     

Clinical evaluation of an eccentric infrared photorefractor: the PowerRefractor

PURPOSE: To evaluate the viability of the PowerRefractor as a screening tool for examining refractive errors in large samples of children. METHODS: The variability of the PowerRefractor was estimated using four patients. The refractive error was determined using cyclopentolate and tropicamide as cycloplegic agents and compared to that determined in a non-cycloplegic situation. In a second study, the data provided by the PowerRefractor were compared to results obtained by autorefractor or retinoscopy for 150 children aged from 6 months to 5 years. RESULTS: Variability study. Statistical analysis showed a statistically significant difference between cycloplegic and non-cycloplegic refraction for spherical and cylindrical refractive errors (p<0.0001 in all cases). There was no significant difference between the measurements made using tropicamide and cyclopentolate (p=0.33 and p=0.18, respectively). Comparison study. In 142 of 150 patients the difference between data obtained by the PowerRefractor and an autorefractor was within 1 D (spherical equivalent). However, there was a considerable difference between the data generated by the two methods in the remaining eight patients (up to 16 D). CONCLUSIONS: The PowerRefractor proved to be a reliable tool for estimating refractive errors in young children. The apparatus is easy to handle and the simultaneous examination of both eyes makes the PowerRefractor ideal for obtaining data on refractive errors in large samples.     

Clinical investigation of an infrared digital scanning laser ophthalmoscope.

An infrared scanning laser ophthalmoscope (SLO) has been custom built in order to investigate the application of confocal and indirect mode SLO imaging to patients with fundus disease. Infrared light is reflected from the fundus to a greater extent than visible light permitting lower illumination power and, as it penetrates the retinal pigment epithelium, choroidal structures can be readily imaged. Furthermore, as conventional infrared illumination and detection systems are not well suited to ophthalmoscopy, this area is underdeveloped as a potential source of useful clinical data. Confocal, direct and indirect imaging modes have been used to image fundi of normal volunteers and patients with fundus disease. In comparison with conventional fundus photography confocal infrared SLO imaging improves visualisation of choroidal vasculature, retinal pigment epithelial abnormalities, laser photocoagulation scars, and optic disc pores in the lamina cribrosa. Direct infrared SLO imaging enables fundus visualisation through nuclear lens opacities. Furthermore, indirect mode imaging enhances significantly the appearance of macular drusen. The potential clinical benefit of these observations is discussed.     

Red light irradiation as an intervention for myopia

Myopia is one of the main causes of visual impairment worldwide. Preventing myopia and providing myopia-related interventions are of paramount importance. Based on a thorough review of the available literature, we conclude that red light irradiation can produce hyperopia, resulting in myopia prevention and control. Further, we suggest that red light irradiation may be a powerful tool for myopia prevention and control in the future. At the same time, red light has a protective effect on the cornea and retina at the cellular level, suggesting that red light irradiation may be a safe and effective modality for delaying myopia. Therefore, this form of irradiation is expected to play an important role in the prevention and control of myopia. However, more studies are needed to enhance the current state of knowledge and inform medical guidelines more comprehensively.     

Prototype of an ophthalmoscope for studying an upright image with light amplification

The instrument described here is the prototype of a direct ophthalmoscope with amplification of available light. The beam path has already been published and patented under reference number 3124305. It does not require drug-induced mydriasis, reduces light toxicity of the retina, and facilitates examination of pre-eclamptic and other patients who are sensitive to light. With this ophthalmoscope it may be possible to demonstrate the autofluorescence of the hyalocytes, described by Cremer-Bartels and Balacz.     

The use of an infrared eyetracker to measure fixation stability.

PURPOSE: To assess fixation stability in patients, a scanning laser ophthalmoscope (SLO) has typically been required. Disadvantages of this technique include the need for a fixed viewing distance and rigid head support. Some modern infrared eyetrackers do not have these constraints. The purpose of this study was to compare fixation stability measurements made with these instruments. METHODS: Normal subjects were asked to fixate a 2.5 degrees high cross while fixation was measured with a SLO and an infrared eyetracker. Bivariate contour ellipse areas were calculated. RESULTS: There was a linear relationship between the bivariate contour ellipse areas measured using each instrument. Bivariate contour ellipse areas returned from the eyetracker were larger. There was no difference in test-retest variability between the instruments. CONCLUSIONS: The eyetracker indicates fixation to be less stable than the SLO does, perhaps because of eye movements to compensate for small head movements. Our eyetracker can be used to analyze fixation when viewing images at any distance, without the need for head immobilization. The eyetracker and the SLO complement each other in the investigation of visual behavior.     

Treatment of an avulsed retinal vessel with infrared diode laser photocoagulation

PURPOSE: To report the use of the infrared diode laser with long-duration pulses to successfully treat a patient with recurrent vitreous hemorrhages due to an avulsed retinal arteriole. DESIGN: Interventional case report. METHODS: A 70-year-old man presented with repeated, visually significant vitreous hemorrhages due to an avulsed retinal arteriole. Infrared diode laser photocoagulation with long-duration, large, overlapping spots was performed on either side of the avulsed segment. RESULTS: Resolution of the hemorrhage occurred within 1 month, without further episodes of bleeding. Two-year follow-up with fluorescein angiography showed complete cessation of blood flow through the treated segment. CONCLUSIONS: Infrared diode laser photocoagulation with long-duration pulses may be an effective, minimally invasive treatment of the avulsed retinal vessel syndrome.     

Darkness enhancement in intermittent light: an experimental demonstration

An experimental arrangement for measuring changes of subjective darkness of low luminance periods during intermittent photic stimulation is described, and the manner in which subjective darkness depend upon flicker frequency was determined. The results proved the existence of a “darkness” enhancement effect, quite analogous to the well-known brightness enhancement or Brücke-Bartley effect. The theoretical implications of this finding are briefly discussed.     

Evaluation of a clinical glare test based on estimation of intraocular light scatter.

A glare test based on psychophysical estimation of intraocular light scatter and using a flickering, annular glare source was evaluated. The parameters determining the accuracy of the test were studied. In particular the influence of background light and flicker frequency were investigated and optimum values for best accuracy were found. Based on these findings a versatile and simple apparatus was constructed. Forty patients with various degrees of cataract were investigated in a clinical study. Patients, who subjectively experience severe glare problems, indeed show high glare values as measured with the apparatus. No obvious relation between visual acuity and glare score was found. In comparison with glare tests using a stationary glare source the use of a flickering glare source is advantageous in terms of sensitivity and accuracy.