Vitreo-retinal biomicroscopy using bilaterally aspherical Volk lenses (+78 D, +90 D)]

Aspherical+ Volk lenses allow a full realization of El Bayadi conception of use of a great power a positive lens for the indirect ophthalmoscopy by means of a biomicroscope. The authors compared the techniques of ophthalmoscopy with utilization of a biomicroscope pointing to following advantages of the Volk lens: the lack of contact with the patient's eye (avoidance of eventual transmission of infection), possibility of examination of the entire area of the fundus, a detailed evaluation of the vitreous, possibility of examination even by narrow pupil, a high comfort of examination for the patient. These advantages were confirmed during the examination of 51 eyes with retinal detachment, pathological changes of the macula and the optic disc and with intraocular tumors.     

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.     

Magnification-corrected photodynamic therapy

Background To present a method for performing photodynamic therapy (PDT) with a constant predictable light fluence based on actual laser spot magnification. Methods A calibrated Gullstrand-type model eye with a scale of half circles in the centre of the artificial fundus was used for this study. The axial length of the model eye was set to different values ranging from 20 to 31 mm, and the actual laser spot magnification of four indirect condensing laser lenses were determined using a PDT laser unit. Results Equations for determining the actual laser spot magnification were calculated for each laser lens. The total change in laser spot magnification from hyperopia (axial length 20 mm) to myopia (axial length 31 mm) was −20% to +24.8% for Mainster Standard lens (Ocular Instruments Inc, Bellevue, Washington, USA), −15.7% to +27.7% for Mainster Wide Field lens (Ocular Instruments Inc), −16.3% to +33.1% for Volk Transequator lens (Volk Optical Inc, Mentor, Ohio, USA), and −19.2% to +24.4% for Volk PDT Laser lens (Volk Optical Inc). Conclusions Axial length of the eye has a considerable effect on PDT laser spot magnification when an indirect laser lens is used. By calculating the actual laser spot magnification in conjunction with knowledge of the true greatest linear dimension of the neovascular lesion, the clinician may be able to deliver a constant predictable amount of light fluence to the fundus independent of the axial length of the PDT treating eye. No Grant/Financial Support. The authors have no financial interest in any of the products discussed in this article.     

90 D Volk fundus lens

The 90 D lens is used in conjunction with a slit lamp biomicroscope to provide a stereoscopic indirect view of the ocular fundus. The clinical picture is an indirect view of the posterior pole and as far anterior as the equator. Being hand-held, it requires some practice to maintain alignment but does not require contact with the globe. Table 1 summarizes the clinical advantages and disadvantages of the 90 D lens.     

Ultra wide field fundus biomicroscopy with the Volk Quadraspheric lens

Fundus biomicroscopy as a clinical technique has been enhanced significantly by the addition of indirect view condensing lenses. The combination of this type of lens with a corneal contact element allows higher power and better stability so that a wider field can be obtained. The Panfunduscope of Schlegel and the Mainster retinal lens are examples of this design that have been successfully applied to both examination and to pan-retinal photocoagulation. Volk has recently introduced a new aspheric design indirect contact lens system which is higher in power and provides a wider field of view (125 degrees) than previously obtainable. This article describes the optical properties and use of the Quadraspheric lens.     

Flächenbestimmung der Papille mittels indirekter Ophthalmoskopie

PURPOSE: The aim of this study was to assess the accuracy of measuring the optic disc area by indirect ophthalmoscopy. PATIENTS AND METHODS: In a prospective clinical trial, 57 eyes of 29 subjects (age 57.3+/-12.1 years) were examined. The refractive error was -0.67+/-2.69D (+3.75D to -8D).The vertical and horizontal disc diameters (DD) were measured using a Haag-Streit slit lamp and 60D-, 78D-, 90D-, and Super Field lenses (Volk Optical, Mentor, USA). Afterwards the disc area was calculated by an ellipse formula (horizontal DD x vertical DD x pi/4). The magnification factor given by the manufacturer was taken into account for each lens: 1.15x (60D lens), 0.93x (78D lens), 0.76x (90D lens), and 0.76x (Super Field lens), respectively. As reference for the disc size, the same eyes were examined by HRT II (Heidelberg Engineering, Heidelberg, Germany). Bland-Altman plots were used to assess the agreement between measurements obtained by indirect ophthalmoscopy and HRT. RESULTS: The results of the disc estimate compared with the HRT measurements were as follows: 0.119+/-0.51 mm(2) (60D lens), 0.224+/-0.57 mm(2) (78D lens), 0.10+/-0.51 mm(2) (90D lens), and -0.07 s+/-0.47 mm(2) (Super Field lens). Differences were not statistically significant for the 60D (p=0.083), 90D (p=0.147), or Super Field lenses (p=0.257). However, the difference between the 78D lens and HRT was statistically significant (Student's t-test; P=0.004). CONCLUSION: Measuring the disc size by indirect ophthalmoscopy is possible. The 90D lens showed the smallest and the 78D lens the largest deviation.     

Monocular vs. stereoscopic measurement of cup-to-disc ratios

Stereoscopic viewing of the optic nerve head and cup has been reported to provide more reliable cup-to-disc (C/D) ratio estimates. We investigated the variability in C/D ratio estimates among three experienced optometric clinicians using conventional direct ophthalmoscopy and indirect biomicroscopy with the Volk 90 D lens. The pupils of 21 subjects were dilated and the discs assessed randomly by each examiner for the determination of the C/D ratio. Analysis of variance indicates that the two methods are not significantly different from each other when comparing interexaminer reliability. However, for a particular examiner, one method may be more effective than the other.     

The optics of fundus examination

It has been 140 years since the invention of the ophthalmoscope in 1851 by Herman von Helmholtz. Since then, a considerable amount of time and effort has been devoted to improving the clinician's view of the fundus both for diagnostic and therapeutic reasons. Recently, there have been some notable advances in this respect, such as the 90 diopter lens, the “2.2 pan retinal” lens, and numerous “wide angle” fundus-viewing contact lenses to which the Volk Quadraspheric fundus lens has been the most recent addition. This paper is a review of the optical principles underlying the methods of fundus examination currently available.     

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.     

Indirect biomicroscopy techniques

An improved method of biomicroscopic examination of the ocular fundus has been made possible with the use of a +90 diopter condensing lens. Formation of a superb aerial image provides a magnified, stereoscopic view of the posterior fundus to the equatorial area when used in conjunction with the slit lamp biomicroscope. This non-contact method of evaluating the fundus provides superior optics, improved patient comfort and compliance, and an enhanced field of view compared to other available methods of biomicroscopic funduscopy.     

Noncontact retinal photocoagulation at the slit-lamp biomicroscope

Four patients had either ocular conditions that made the use of a contact lens for retinal photocoagulation undesirable, or optical aberrations of the ocular media that made photocoagulation with a conventional contact lens difficult. A hand-held 90-diopter lens permitted retinal photocoagulation to be performed at a conventional slit-lamp biomicroscope laser without corneal contact and assisted in delivering laser burns under physical or optical circumstances that would be difficult or impossible with conventional contact lenses. Four patients without ocular surface or media abnormalities were also treated by this method.     

Ultra-wide field imaging system and traditional retinal examinations for screening fundus changes after cataract surgery

AIM: To compare the results of non-mydriatic ultra-wide field imaging system, mydriatic slit-lamp lens (Volk +90 D) and mydriatic Goldmann three-mirror contact lens examinations in screening fundus lesions among patients after cataract surgery. METHODS: Non-mydriatic images were obtained with an Optomap panoramic 200Tx (Optomap 200Tx) 3d after surgery and graded by a blinded ophthalmologist. A mydriatic slit-lamp lens examination was performed by another blinded retinal specialist on the same day. A third blinded retinal specialist examined patients two weeks after surgery using a Goldmann three-mirror contact lens. RESULTS: In total, 160 patients (184 eyes) were examined, and 66, 69, and 75 cases of retinal lesion(s) were identified using the Optomap 200Tx, slit-lamp lens, and Goldmann three-mirror contact lens, respectively. In 13 cases, fundus changes were sight-threatening. The results obtained by Optomap 200Tx examination and by mydriatic slit-lamp lens examination have good consistency (P=0.375, Kappa=0.942). The mydriatic Goldmann three-mirror lens examination revealed more fundus lesions but are consistent with Optomap 200Tx (P=0.004, Kappa=0.897) and mydriatic slit-lamp lens examination (P=0.031, Kappa=0.932). CONCLUSION: Early post-operative fundus screening in cataract patients is extremely important and necessary to prevent further vision loss. Wide-field imaging is a feasible and convenient tool for fundus examination that can be used as a primary screening method among patients after cataract surgery.     

糖尿病黄斑水肿的临床诊断方法比较

目的 对比分析糖尿病黄斑水肿患者光学相干断层扫描(optical coherence tomo-graphy,OCT)、荧光素眼底血管造影(fluorescein fundus angiography,FFA)及裂隙灯显微镜下+90 D前置镜检查所观察到的图像特征,探讨3种检查方法的诊断价值.方法 分析51例(94眼)临床确诊为糖尿病视网膜病变患者的OCT、FFA及裂隙灯显微镜下+90 D前置镜检查结果,将结果进行一致性比较,并观察分析OCT、FFA图像特征,所得结果行单因紊方差分析.结果 OCT与FFA及FFA与+90 D前置镜检查结果有较好的一致性,符合率分别为88.3%、69.1%.OCT、FFA与+90 D前置镜裂隙灯显微镜下检查结果对糖尿病黄斑水肿的检出率分别是86.2%、83.0%及62.8%.OCT所测得的黄斑中心凹平均视网膜厚度值在无渗漏时最低,并随局限性渗漏、弥漫性渗漏、局限合并弥漫性渗漏、黄斑囊样水肿依次增加,经比较它们之间的差异均具有统计学意义(F=40,P均<0.05).结论 OCT能客观的提供糖尿病患者黄斑区结构的变化,尤其对+90D前置镜裂隙灯显微镜下检查及FFA还没有明确变化的早期黄斑水肿诊断敏感.三者的联合应用为揭示糖尿病病理机制、临床诊断糖尿病黄斑水肿、判断糖尿病黄斑水肿的类型及其最佳治疗方案提供参考依据.     

Biomicroscopy of the fundus oculi using a 90 diopter lens

An improved method of indirect biomicroscopic examination of the ocular fundus has been made possible with the use of a + 90 D lens since 1985. Its special optical characteristics make it a very useful instrument. During this study of 220 retinal detachments we compared this instrument with other methods for examining the ocular fundus (Goldmann fundus contact lens, panfundoscope, binocular indirect ophthalmoscope with a 20 D lens). Other uses for the lens are described. This non-contact examining technique provides excellent visualisation, a wide field of vision, and good patient tolerance. The 90 D lens is particularly useful in vitreo-retinal management of retinal detachment both during and immediately after surgery.     

Photographic and other uses of the QuadrAspheric Fundus Lens

The new QuadrAspheric Fundus Lens by Volk Optical is an ultra wide field lens that has many uses as a specialty lens. Photography can be accomplished through the lens but light reflexes are always present to a greater or lesser extent. Techniques to eliminate as many of the unwanted reflexes as possible are discussed. The lens also is very useful when the patient's pupil is not widely dilated and the clinician can even obtain a view through an undilated pupil (though this is difficult to achieve). Lastly, proper cleaning procedures are presented.     

Safe exposure times for slit-lamp fundus biomicroscopy with high plus lenses.

PURPOSE: The purpose of this study was to calculate the retinal irradiance and maximum permissible exposure time (MPE) using high plus fundus biomicroscopy lenses. METHODS: Four Volk handheld condensing lenses (+78 D, +90 D, Superfield NC, and Super 66) were tested with biomicroscopes from three manufacturers (Nikon, Topcon, and Zeiss) on both high and medium illumination. Using the conservation of radiance theorem, the retinal irradiance was calculated and. with guidelines from the American National Standard Institute (ANSI). the maximum permissible exposure time was determined. RESULTS: The range of MPE time across all lenses and biomicroscopes was from 23 seconds to 74 seconds on high illumination setting. The average MPE times were: for the +78 D, 36 seconds; the Superfield NC, 57 seconds; the Super 66, 32 seconds; and the +90 D, 52 seconds. CONCLUSION: Retinal irradiances and safe exposure times are useful guidelines in both the clinical and academic setting. Fundus biomicroscopy with non-contact high plus condensing lenses produced calculated retinal irradiances and MPE times similar to those of other commonly used ophthalmic equipment. Awareness of the maximum permissible exposure time increases the safety of this valuable technique.     

Magnification characteristic of a +90-diopter double-aspheric fundus examination lens

PURPOSE: To investigate the magnification characteristic of the +90-D double-aspheric fundus examination lens for biomicroscopic measurement of the optic disc. METHODS: A calibrated Gullstrand-type model eye adjusted for axial ametropia between -12.5 and +12.6 D was used to measure the change in magnification of the system with refractive error and variation in fundus lens position. A correction factor p (in degrees per millimeter) at different axial ametropias was also calculated. RESULTS: The total change in magnification of the system from myopia to hyperopia was -15.1% to +13.7%. When the fundus lens position was altered with respect to the model eye by +/-2 mm under myopic conditions, the change in magnification of the system was -4.8% to +8.1%. In the hyperopic condition the change was -4.8% to +6.0%. The fundus lens exhibited a linear relationship between p and the degree of ametropia of the model eye and a constant relationship between p and ametropia of -5 to +5 D. CONCLUSIONS: Axial ametropia has a significant effect on biomicroscopic measurement of the optic disc with the +90-D lens. Therefore, a correction factor (p) was calculated that can be used in calculations for determining true optic disc size. These findings may be important for improving clinical disc biometry.     

超声生物显微镜在眼前段挫伤的应用

目的探讨超声生物显微镜在眼前段挫伤中的临床应用价值。方法对83例（83眼）眼前段挫伤进行眼科常规检查、传统眼科B超和超声生物显微镜检查。结果超声生物显微镜可清晰地显示前房角后退、虹膜根部断离、睫状体分离、晶状体悬韧带断裂不全脱位，还可显示出传统B超所不能显示的睫状体和脉络膜浅脱离。结论超声生物显微镜在眼前段外伤中有极好的应用价值，尤其是在屈光介质浑浊、睫状体分离低眼压和隐藏在虹膜后的病变时，它可显示出采用常规检查所不能揭示的病变，它的应用可为眼前段挫伤的诊断和治疗提供确切的指导。     

The effect of axial length on photodynamic therapy

PURPOSE: To determine the effect of the axial length of the eye on photodynamic therapy (PDT) light fluence. DESIGN: Laboratory investigation. METHODS: A calibrated Gullstrand-type model eye was used for this study. The axial length of the model eye was set to different values ranging from 20 to 31 mm, and the light fluence rate for treating a spot of 4 mm was recorded and compared with a fluence rate of 600 mW/cm2 with four indirect condensing laser lenses. RESULTS: The axial length of the eye is inversely related to light fluence. From myopia to hyperopia, the total deviation from 600 mW/cm2 was -37.7% to +53.8% (Mainster Standard; Ocular Instruments Inc, Bellevue, Washington, USA), and -48.3% to +20.5% (Mainster Wide Field; Ocular Instruments Inc), -52.3% to +16.7% (Volk Transequator; Volk Optical Inc, Mentor, Ohio, USA), and -52.3% to +15.3% (Volk PDT Laser; Volk Optical Inc). CONCLUSIONS: Axial length of the eye has a considerable effect on PDT light fluence rate in this model. These findings may be important for optimizing PDT, particularly in eyes with high refractive errors.