Visante OCT

Anterior segment optical coherence tomography (OCT) has become an important tool for evaluating the cornea and the anterior segment or front portion of the eye. Cross sectional tissue images of these ocular structures can be generated in vivo, for detailed analysis.

The clinical applications of anterior segment OCT are extremely important and useful. Cross-sectional images of the cornea, anterior chamber, crystalline lens and iris can be obtained in a manner that no other technology can provide. These images can be invaluable in the diagnosis and management of many anterior segment diseases and conditions such as keratoconus, corneal transplants, corneal ectasia, narrow angle glaucoma, and many other corneal dystrophies and degenerations.

In addition to the above uses of this technology, our specialty lens practice uses optical coherence tomography to assist us in gaining a better understanding of many of the complex corneal conditions that we see and treat. We are using OCT technology to help us create more sophisticated scleral lens designs for specific corneal conditions and diseases. Our goal is to use this technology and new emerging technologies that we possess to allow our “hi need” patients regain useful functional vision along with excellent comfort.

Note in the attached images how the OCT allows the fit of the lens to be assessed at all points along the cornea and sclera.

The instrument seen here is an aberrometer and the technology that it provides us in known as “aberrometry”. This is a new technology that allows us to design a scleral lens with superior optics when compared to previous scleral lens designs. There are millions of patients around the world who have lost quality vision due to refractive surgery, keratoconus, corneal transplant surgery and corneal disease who suffer varying degrees of vision defects known as “higher order aberrations” or simply “HOA’S”. HOA’S are complex vision disorders responsible for patients experiencing ghosting, double vision, starbursts and halos around lights. Measuring these aberrations cannot be done by simply scanning the anterior surface of the eye. In order to identify and measure these aberrations, the aberrometer seen here is used to send a light into the eye. This light passes through the cornea and the lens of the eye and is reflected back to the retina. The reflected light is then identified and measured by the aberrometer. Finally, these aberrations (HOA’S) are displayed in 3D on the aberrometer’s computer screen. How the light passes through the eye is known as wavefront technology. The resulting aberration profiles are uploaded to a special laboratory that embeds this information into the surface of a highly oxygen permeable so that these HOA’S can be eliminated
and the patient’s vision improved.

Last year we introduced an exciting piece of technology that has allowed us to custom design a scleral lens much more accurately. It is the SMAP 3D, which is a computer attached to a dedicated camera that allows us to obtain a 3 dimensional image of the entire front surface of the eye, including the cornea and the surrounding white portion of the eye (the sclera). Up until now there has not been any technology that would allow us to measure
the ocular curvatures outside the cornea. The SMAP allows us to do this. Because the scleral lens rests on the white portion of the eye it is very important to have this information. Most eyes have scleral surfaces that are asymmetric. That is. the scleral curves vary depending on what part of the white portion of the eye your are looking at. These surface curvatures also vary between eyes of the same patient. The SMAP measures over 1 million points along the ocular surface with a precision of less than 10 microns. We are even able to obtain scleral surface measurements beneath the eyelids. The information provided by the SMAP allows us to design a scleral lens with the back surface curvatures of the scleral lens matching the front surface curvatures of each individual eye.

To obtain a 3 dimensional image of the ocular surface, 3 separate images are taken of each eye, with the patient looking in a different direction with each image taken. The 3 images obtained are stitched together to obtain on 3 dimensional image. These images are uploaded to our scleral lens lab where special computers are able to create a scleral lens where every aspect of the patient’s ocular surface is replicated onto the back surface of the scleral lens. The vision and comfort provided to our patients is always excellent with all day comfortable lens wear.

The images below are computer enhanced 3-D models of 2 different corneas that underwent refractive eye surgery. The first image is of an eye that was extremely nearsighted (-17.00 diopters) before undergoing LASIK surgery. Instead of having a smooth rounded curvature to it, this cornea is as flat as a table top. The 2nd 3-D image is of a cornea that underwent both RK (radial keratotomy) surgery followed by LASIK surgery many years later. The center of this cornea is extremely depressed as depicted by the blue area in the center of this image. Both of these corneas are so distorted that eyeglasses and conventional contact lenses are not able to provide these patients with functional vision with these eyes. Both of these eyes were fit with scleral lenses which replace these corneas as an optical surface. In other words, scleral lenses behave like new corneas. I am posting these images to drive home the fact that refractive eye surgeries present many risks to patients including life long vision loss. Once corneal damage takes place there is no surgery that can undo the damage and restore quality vision once again. My comments also apply to any new refractive surgeries that recently received FDA approval.

Below are 2 sets (or slides) of topographical ring and “point spread function images” (PSF) of the same pair of eyes of a patient that underwent both RK and LASIK surgery.

Although you can see the distorted ring images on the photos (slide) on top, what is most interesting are the “point spread function images” (PSF) that can be seen in the upper portions of both sets of images. Look carefully at both the upper and lower sets of PSF images. These images show how a very small beam of light “spreads” after passing through a pair post-surgical (LASIK) corneas and on the same corneas with scleral lenses (lower set of slides). The very small red dot represents a fine beam of light. In the upper set of images, note the white-grey “web-like” patterns around the red beam of light. This represents how light is “spread out” when passing through a distorted post-LASIK cornea. Note how the left PSF image (the image on the right side of the slide) is significantly more distorted than the right PSF image. This is because the left cornea is more distorted than the right cornea. This is why eyeglasses and soft contact lenses cannot provide the post-LASIK distorted cornea with clear, crisp vision. Note the PSF images of same pair of eyes with scleral lenses on the lower set of slides. Note that the small beam of light has virtually no distortion after passing through the scleral lenses. Also note that the ring images in the lower half of the bottom set of slides are perfectly round. Note how the topographical rings in the lower half of the upper set of slides are significantly distorted. Scleral lenses in effect replace the cornea as an optical surface.

The Radiuscope is an essential instrument for measuring the curvature of a contact or scleral lens to the second decimal place. In addition if a lens should have an slight irregular curvature, we can detect it with the use of this instrument. Every lens that comes into our office is checked and double checked to make sure that all of the lens specifications are exactly as ordered. In this photo, you see one of our student doctors examining a scleral lens to make sure that all of the lens curvatures are exact.

What you are seeing in this image is a cross sectional view of the macula and retina. Optical Coherence Tomography is the only technology that will allow us to study all of the ocular structures in the back portion of the eye in such great detail.

Frequency Doubling Technology (FDT) provides a rapid method of detecting visual field abnormalities seen in ocular disease such as glaucoma, certain brain tumors and optic nerve disease. This instrument has a high level of sensitivity and specificity allowing us to detect visual field abnormalities at a very early stage.

Zeiss Anterior Segment Ocular Coherence Tomography allows the structures in the front section of the eye to be examined

This instrument allows us to visualize and measure the anterior structures of the eye including the cornea, anterior chamber, iris, and lens. We have found this technology invaluable in helping us design with great accuracy specialized contact and scleral lenses for patients suffering vision loss due to keratoconus, post refractive surgical complications such as LASIK and RK complications,
corneal transplant surgeries, dry eyes and other ocular diseases and conditions.

Zeiss Anterior Segment Ocular Coherence Tomography allows the structures in the front section of the eye to be examined
Zeiss Anterior Segment Ocular Coherence Tomography allows the structures in the front section of the eye to be examined