Abstract:
A gonioscopy lens is a contact lens that is used to observe and assess the anterior chamber angle (ACA) of the eye. A gonioscopy assembly ( 100 ) advantageously includes a gonioscopy lens adapted for connection to a tonometer. The gonioscopy assembly includes an eye contact portion ( 41 ) which is positioned in contact with the eye by moving the tonometer, which also holds the gonioscopy assembly in place to maintain it in contact with the eye. When the gonioscopy assembly is provided with one or more mirrors, all four quadrants of the ACA may be viewed simultaneously, without repositioning the slit lamp or the gonioscopy assembly ( 100 ). For increased convenience, stability and precision, the tonometer may optionally form part of the tonometer arm of a slit lamp.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority under 35 U.S.C. § 119 (e) based on U.S. Provisional Application Ser. No. 60/338,016, filed on Nov. 7, 2001, the entire disclosure of which is hereby incorporated by reference as if set forth fully herein. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to the field of medical examination of the eye, specifically to gonioscopy, that is, the examination of the anterior chamber angle of the eye.  
         [0004]     2. Description of the Related Technology  
         [0005]     The determination of the pressure within the eye, or intraocular pressure, is an important part of the medical examination of the eye. Glaucoma, for example, is a leading cause of blindness worldwide that is usually associated with abnormally high internal pressure in the eye.  
         [0006]     Intraocular pressure is measured directly with a tonometer. Tonometers are classified as contact or non-contact tonometers. A non-contact tonometer, for example an air-puff tonometer, does not touch the eye during the intraocular pressure measurement. Alternatively, applanation tonometers, for example a Goldmann tonometer, must be brought into contact with the eye in order to properly measure intraocular pressure. This type of tonometer measures the force required to flatten a known area of the cornea. A greater force is required when the pressure inside the eye is increased; conversely, a smaller force is required when the intraocular pressure is decreased.  
         [0007]     Contact tonometers share the characteristic of placing and holding an object against the eye using a small, measurable, continuously variable, and controllable force. These are sensitive instruments, finely calibrated, and they are specifically designed to eliminate excessive pressure on the eye during the determination of intraocular pressure.  
         [0008]     In a typical ocular examination, the medical practitioner will use a slit lamp, also known as a biomicroscope. The slit lamp provides the illumination and magnification necessary to observe the eye&#39;s structure, particularly its interior structure. The mechanism of the slit lamp allows its focal plane to be manipulated in three dimensions to obtain clear views of the eye. In addition to optical and lighting components, a slit lamp also comprises a slit lamp base for positioning the apparatus relative to the patient and the practitioner, and for providing stability to the other components of the apparatus.  
         [0009]     A tonometer may optionally be attached to a slit lamp apparatus. The attachment may be removable, as in the case of a Goldmann tonometer, for example. When the tonometer is movably or rotatably attached to the slit lamp apparatus, and the attachment is permanent, the apparatus is often referred to as a tonometer arm. Advantageously, a tonometer used in conjunction with a slit lamp allows the medical practitioner to assess intraocular pressure with greater accuracy and precision. In addition, attaching the tonometer to a stable base, for example a slit lamp base, will improve the measurability, constancy and controllability of the applied force.  
         [0010]     The anterior chamber angle (ACA) of the eye is the angle formed at the junction of the cornea and the iris. The ACA houses the trabecular meshwork, which is the structure that is responsible for draining the aqueous fluid produced by the ciliary body. Thus, the trabecular meshwork ultimately regulates the intraocular pressure. It is important, therefore, in diagnosing illnesses such as glaucoma, to evaluate the ACA, since anatomical differences, both physiological and pathological, can affect its integrity and function. Observation of the ACA is also important in assessing the extent of traumatic injuries to the eye. For example, an eye injury can cause a hyphema, that is, bleeding into the anterior chamber, or iridodialysis, that is, tearing of the iris at the scleral spur, either of which can affect the proper functioning of the ACA.  
         [0011]     The ACA, however, cannot be viewed by direct observation through a slit lamp, because the ACA image, in the form of light, is trapped within the eye by total internal reflection. Thus, medical examiners wishing to evaluate the ACA using methods current in the art use a contact lens called as a gonioscopy lens, also known as a gonioprism. The index of refraction and the geometry of the gonioscopy lens are such that the problem of total internal reflection is overcome. To evaluate the ACA, the practitioner holds the gonioscopy lens against the cornea manually, usually after the administration of an appropriate topical anaesthetic. The practitioner adjusts the magnification, illumination, focus, and positioning of the slit lamp to view a section of the ACA.  
         [0012]     Certain gonioscopy lenses, because of their design, are rotated manually until the practitioner has observed all four quadrants (superior, temporal, inferior, and nasal) of the ACA. Other hand-held gonioscopy lenses include four mirrors. When using such lenses, the practitioner need not rotate the lens to view all four quadrants of the ACA; however, the slit lamp must be repositioned, as the images in the mirrors are too far apart to be viewed simultaneously through the oculars of the slit lamp. Each repositioning may also require refocusing the slit lamp.  
         [0013]     It is apparent that the use of hand-held gonioscopy lenses necessitates manual positioning and constant manual repositioning of the lens and/or the slit lamp to accomplish an examination of the entire ACA. A manual gonioscopy exam is time consuming, and usually results in patient discomfort. The manual handling of the gonioscopy lens may also result in an inaccurate assessment, as excessive force applied to the eye via the gonioscopy lens can change the orientation of the iris relative to the cornea. In cases of acute trauma to the eye, gonioscopy is usually not performed for several weeks after the injury, due to the probability that the gonioscopy procedure itself will further injure the eye. This delay in obtaining critical information can hamper appropriate diagnosis, and can affect prognosis and proper management of the injury.  
         [0014]     U.S. Patent Application Publication No. 2002/0085173 sets forth an alternative system for measuring the depth of the ACA. In this system, the eye is mapped by determining the distance between the cornea and the iris at several locations. After the eye is mapped in this way, a computer performs calculations, using the distance and location data, to obtain the ACA depth. This system does not allow for direct observation of the ACA and its substructure.  
         [0015]     U.S. Pat. No. 6,019,472 describes a system including a liquid, a contact lens having a recess capable of holding a volume of the liquid against a cornea of an eye, and a microscope objective connected to a series of lenses, including the contact lens element. This system is used for examining and treating certain parts of the eye, particularly the retina, and seeks to decrease optical aberration in ocular examinations. The tonometer does not form part of this system.  
         [0016]     Thus, gonioscopy as now practiced by those of skill in the art presents several drawbacks, including prolonged time of examinations, inability to view all four quadrants of the ACA simultaneously, patient discomfort due to excessive pressure and manipulation of the lens, the likelihood of causing further damage in cases of severe trauma to the eye, and the likelihood of inaccurate assessment through distortion of the iris position.  
         [0017]     Therefore, there is a need in the art for a gonioscopy lens that reduces the length of ocular examinations, increases the accuracy of ACA assessments, allows for simultaneous viewing of all four quadrants of the ACA, minimizes patient discomfort, and minimizes the likelihood of producing further injury in cases of acute trauma.  
       SUMMARY OF THE INVENTION  
       [0018]     Accordingly, it is an object of the invention to provide a gonioscopy assembly that reduces the length of ocular examinations, increases the accuracy of ACA assessments, allows for simultaneous viewing of all four quadrants of the ACA, minimizes patient discomfort, and minimizes the likelihood of producing further injury in cases of acute trauma.  
         [0019]     In order to achieve the above and other objects of the invention, a gonioscopy assembly, comprising a gonioscopy lens and an adapter for connection to a tonometer, is provided.  
         [0020]     According to a second aspect of the invention, an apparatus for observing the anterior chamber angle of the eye is provided. The apparatus comprises a gonioscopy lens connected to a tonometer.  
         [0021]     According to a third aspect of the invention, a method of observing the anterior chamber angle of an eye is provided. In this method, a gonioscopy lens attached to a tonometer is provided, the tonometer is used to position the gonioscopy lens in contact with the eye, and the anterior chamber angle is observed through the gonioscopy lens.  
         [0022]     According to a fourth aspect of the invention, a method of retrofitting a tonometer to perform gonioscopic examinations is provided. In this method, a gonioscopy assembly comprising a gonioscopy lens is connected to a tonometer, and the anterior chamber angle is observed through the gonioscopy lens. The gonioscopy assembly may also include an adapter for connecting the lens to the tonometer.  
         [0023]     According to a fifth aspect of the invention, a gonioscopy lens having an eye contact portion with an opaque posterior surface is provided.  
         [0024]     In these and other embodiments of the invention, the tonometer may optionally be movably or rotatably attached to a slit lamp.  
         [0025]     These and various other advantages and features of novelty that characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]      FIG. 1  is a fragmentary side view of an eye.  
         [0027]      FIG. 2  is a fragmentary side view of a gonioscopy lens in contact with the eye.  
         [0028]      FIG. 3  is a perspective view of a gonioscopy assembly of the invention.  
         [0029]      FIG. 4  is an expanded fragmentary front view of the eye contact portion of the gonioscopy assembly.  
         [0030]      FIG. 5  is an expanded fragmentary side view of the eye contact portion of the gonioscopy assembly, along a viewing axis orthogonal to that of  FIG. 4 .  
         [0031]      FIGS. 6A through 6F  are fragmentary side views of the reflective portion of the gonioscopy assembly. Each embodiment is shown in a perspective view and in a rear view along the central axis of the gonioscopy assembly.  
         [0032]      FIG. 7  is a fragmentary side view of the gonioscopy assembly of the invention connected to a tonometer ring and in contact with an eye. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]     Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views, and referring in particular to  FIG. 1 , the ACA  10  is formed by the junction of the cornea  20  and the iris  30 .  
         [0034]     In  FIG. 2 , a gonioscopy lens  1  positioned in contact with the cornea  20  is shown. The gonioscopy lens may optionally be equipped with one or more mirrors  2  to facilitate viewing the ACA  10 .  
         [0035]      FIG. 3  depicts a gonioscopy assembly  100  of the invention. The assembly  100  includes an eye contact portion  40 , a reflecting portion  50 , and an image transmitting portion  60 . Image transmitting portion  60  transmits the image of the ACA  10  towards the medical practitioner. Preferably, the shape of image transmitting portion  60  is cylindrical, its length is preferably up to about 25 mm, and its diameter is preferably between about 10 and about 12 mm, more preferably about 10.65 mm. Image transmitting portion  60  may be formed of a solid piece of the clear medium, but may alternatively be hollow, for example. Its construction is suitable so long as the medical practitioner is capable of viewing the ACA  10 .  
         [0036]     Still referring to  FIG. 3 , the eye contact portion  40  of the assembly  100  includes a lens portion  41  having a central concave surface  42  and an optional peripheral curve  44 . The thickness of eye contact portion  40  is preferably about 0.5 mm to about 4 mm. The central concave surface  42  is intended to contact the patient&#39;s eye. The diameter of eye contact portion  40  is preferably about 6.5 to about 11.5 mm, more preferably about 9 mm, and the base curve radius of concave surface  42  is preferably about 7.4 to about 9.4 mm, more preferably about 8.4 mm. The base curve radius of the optional peripheral curve  44  is preferably about 8.5 to about 10.5 mm, and more preferably about 9.5 mm.  
         [0037]     The posterior surface  43  of eye contact portion  40  is preferably opaque. Posterior surface  43  may be rendered opaque by any means known in the art. When posterior surface  43  is opaque, light directed from the temporal side of lens portion  41  is diffused throughout the entire circumference of eye contact portion  40 . Advantageously, this diffusion results in illumination of the entire circumference of the ACA.  
         [0038]     The illumination for the opaque posterior surface  43  may be supplemented further by external mirrors attached to either the contact portion  40 , the reflecting portion  50  or both. These mirrors will serve to redirect the slit lamp&#39;s light source and provide additional illumination to the circumference of the ACA.  
         [0039]     The illumination of the opaque posterior surface  43  may be supplemented by one or more fiber optic light sources. For example, two banks of fibers may be mounted on either side of the reflecting portion  50  of the assembly  100  such that light directed from the temporal side of the eye under examination is carried to the fibers&#39; terminal ends, which preferably surround the outer edge of lens portion  41  of the lens. The light supplied by these fibers would be directed anteriorly and thus provide additional light to improve the image of the ACA.  
         [0040]     Still referring to  FIG. 3 , image transmission portion  60  has at least one diameter,  62 . If the diameter  62  is inappropriate for connection to a tonometer, an adaptation may be made by including optional notch  65 , thus producing a second diameter  68 . Second diameter  68  may be larger or smaller than diameter  62 .  
         [0041]     Referring now to  FIG. 4 , concave surface  42  may further include a peripheral curve  44  preferably having a radius of about 8.5 to about 10.5 mm, more preferably about 9.5 mm. Peripheral curve  44  has a thickness of preferably about 0.1 to about 0.4 mm, more preferably about 0.2 mm. Peripheral curve  44  facilitates removal of the assembly  100  from the patient&#39;s eye by decreasing the force necessary to overcome the vacuum formed when eye contact portion  40  is pulled away from the cornea  20 .  
         [0042]      FIG. 5  is front view of the eye contact portion  40 , from the patient&#39;s perspective, showing the full circumference of the central concave surface  42  and the peripheral curve  44 .  
         [0043]     Referring now to  FIGS. 6A through 6F , light transmitted from the ACA  10  through the lens portion  41  enters the reflecting portion  50 , which houses one or more mirrors  55  whose reflecting surfaces face the interior of the gonioscopy assembly  100 . Methods of placing mirrors on the surface of lenses, or embedding them in lenses, are well known in the art.  
         [0044]     If the mirror or mirrors  55  are embedded in the reflecting portion  50 , the exterior of reflecting portion  50  need not derive its shape from the number or placement of the mirror or mirrors  55 . The shape of reflecting portion  50  could, for example, be a spherocylindrical continuation of image transmitting portion  60 , provided that the mirror or mirrors  55  are positioned so that the medical practitioner may view the ACA  10 .  
         [0045]      FIGS. 6A, 6C , and  6 E depict embodiments of the invention in which the reflecting portion  50  is equipped with one, four, and five mirrors  55 , respectively, on the exterior surface of reflecting portion  50 .  FIGS. 6B, 6D , and  6 F, are rear views along the central axes, showing the medical practitioner&#39;s perspective of the embodiments shown in  FIGS. 6A, 6C , and  6 E, respectively.  
         [0046]     The reflecting surfaces or mirrors  55  may be placed in any position that permits the medical examiner to view the ACA  10 . Preferably, the plane of each mirror  55  forms an angle of between about 50° and about 75° with the plane of the patient&#39;s iris  30 . More preferably, the angle between the plane of each mirror  55  and the plane of the iris  30  is about 68°. In the embodiment depicted in  FIGS. 6A and 6B , preferably the mirror  55  is conical with a taper angle between about 50° and about 75°, more preferably about 68°.  
         [0047]     The overall length of reflecting portion  50  is preferably between about 3 mm and about 9 mm. The anterior width of reflecting portion  50 , that is, the width at the intersection of eye contact portion  41  and reflecting portion  50 , is preferably between about 3 mm and about 7 mm. The posterior width of reflecting portion  50 , that is, the width at the intersection of reflecting portion  50  and image transmitting portion  60 , is preferably between about 9.5 mm and about 11.5 mm, and more preferably about 10.65 mm.  
         [0048]     Referring now to  FIG. 7 , contact tonometers are typically equipped with a tonometer ring  70 , which is the portion of the tonometer or tonometer arm that contacts the patient&#39;s eye, or that holds an object intended to contact the eye. Goldman tonometers, in particular, include a tonometer ring. Preferably, the outer diameter of image transmitting portion  60  is equal to or slightly smaller than the inner diameter of the tonometer ring  70  such that the image transmitting portion  60  fits securely within the tonometer ring  70 . The gonioscopy assembly  100  may then be held within the tonometer ring  70  by the force of friction between the image transmitting portion  60  and the tonometer ring  70 .  
         [0049]     When diameter  62  of image transmitting portion  60  is too large or too small to allow gonioscopy assembly  100  to lodge conveniently within the inner diameter of tonometer ring  70 , second diameter  68  may be provided by including an optional notch  65 . When notch  65  results in a smaller second diameter  68 , advantageously, larger diameter  62  will prevent the gonioscopy assembly  100  from being pushed backwards through the tonometer ring  70 .  
         [0050]     Alternatively, other mechanical fastening means may secure the assembly  100  to the tonometer ring  70 . Preferably, the fastening means are easily reversible, so that the tonometer retains its original function and is conveniently interconverted between uses.  
         [0051]     When the diameter of the image transmitting portion  60  does not permit the gonioscopy assembly  100  to be fitted directly into the tonometer ring  70 , an adapter comprising a female part fitted to the outer diameter of the image transmitting portion  60  and a male part fitted to the inner diameter of the tonometer ring  70  may be used.  
         [0052]     In a further example of suitable fastening means, a removable clip extends over at least a portion of the tonometer ring  70  and the image transmitting portion  60 , which may be adapted to receive the clip and retain it more efficiently.  
         [0053]     In another example, the image transmitting portion  60  is threaded for connection to a threaded tonometer ring  70 , or to a threaded adapter for connecting the tonometer ring  70  to the image transmitting portion  60 .  
         [0054]     In another example, the outer diameter of image transmitting portion  60  is magnetized so that it can be removably attached to a tonometer ring  70  fashioned of a ferric metal. Alternatively, the tonometer ring  70  may be magnetized, or it may be equipped with a magnetic adapter to mate with a magnetized image transmitting portion  60 .  
         [0055]     Gonioscopy lenses of the present invention may be made using materials and methods that are known in the art. Preferably, the gonioscopy lens is made of a glass or a clear plastic or resin. Optional mirrors may be made of any reflective material, preferably a thin metal film.  
         [0056]     Also provided by the present invention is a method for observing the ACA. In the method of the invention, a gonioscopy assembly  100  of the invention is attached to a tonometer. The tonometer is used to position the gonioscopy assembly  100  in contact with the eye, and the medical practitioner observes the ACA  10  through the gonioscopy assembly  100 . The medical practitioner will most likely wish to observe the ACA  10  with the aid of a slit lamp. Conveniently, the tonometer may optionally form part of the tonometer arm of a slit lamp.  
         [0057]     Also provided by the present invention is a method of retrofitting a tonometer to perform gonioscopic examinations. In this method, a gonioscopy assembly comprising a gonioscopy lens is connected to a tonometer, and the anterior chamber angle is observed through the gonioscopy lens. The gonioscopy assembly may also include an adapter for connecting the lens to the tonometer.  
         [0058]     The many features and advantages of the invention include the prevention of inaccurate assessments of the ACA  10  due to excessive pressure applied by a gonioscopic lens held manually against the eye. This advantage accrues from the connection of the lens to the tonometer, which is a sensitive instrument specifically designed to apply a small, calibrated force to the cornea. Reducing excessive pressure on the eye will also reduce the patient&#39;s discomfort resulting from the gonioscopic examination, and, in cases of severe trauma to the eye, will enable the practitioner to evaluate the condition of the ACA sooner and with less risk of further injury.  
         [0059]     When the tonometer is part of the tonometer arm of a slit lamp, the gonioscopy assembly  100  of the invention is capable of “hands-free” positioning. While maintaining all the advantages of connecting the gonioscopic assembly  100  to the tonometer, this configuration provides the additional advantage of providing a convenient light source. Moreover, the gonioscopy assembly  100  may positioned directly in line with the medical practitioner&#39;s view through the slit lamp. Also, the focal point of the slit lamp is in proximity to the ACA. The result of this proximity is that the ACA may be brought into sharp focus by a slight motion of the slit lamp along the cylindrical axis of the gonioscopy assembly  100 . By contrast, hand-held gonioscopy lenses require constant refocusing throughout the course of an examination.  
         [0060]     When the tonometer is capable of being reversibly retrofitted to perform gonioscopic examinations, medical practitioners can maximize the return on their investment in a sophisticated piece of diagnostic equipment. The benefits are increased when the tonometer is part of an even more expensive apparatus such as a slit lamp.  
         [0061]     Another feature of the invention is that the optional mirrors provide the ability to view all four quadrants of the ACA  10  simultaneously. This feature serves to reduce the overall length of the examination, thereby also minimizing the patient&#39;s discomfort. In addition, the entire ACA  10  may advantageously be photographed in one frame, facilitating more comprehensive analysis of the condition of the ACA  10  from one examination to the next.  
         [0062]     It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.