Tuesday, August 4th -inhales deeply in preparation-
Fasten your seatbelts and grab your dictionaries, friends. I'm going to try to make this whirlwind of information as concise and understandable as possible and provide as many links to definitions and further reading as I can but it's still gonna be a doozy of a post!
First, a little medical history.
When I was about two years old I was diagnosed with Retinitis Pigmentosa (RP), a genetic eye disorder that starts with receding tunnel vision, night blindness, and fluctuating (at best) depth perception. With this prognosis my family and I expected that I would eventually become completely blind. Clearly, though, this never occurred. Because my vision never displayed any of the progressions usually associated with RP Dr. Weleber at the Oregon Health Sciences University (OHSU) altered the diagnosis when I was in middle school to Leber's Congenital Amaurosis (LCA), another genetic retinal degenerative that isn't quite as violently progressive as RP. Leber's didn't quite fit what I have but it was the closest thing he knew about, and given Dr. Weleber's status as one of the top four researchers on genetic eye disorders in the world nobody argued. He promised to narrow down the diagnosis as soon as he could, but that meant I would have to see him yearly and allow him to take blood samples every so often to send to their genetic sequencing lab in Iowa. Fortunately our insurance covered these exams, so we agreed to the genetic sequencing. The purpose of the blood draws was to take DNA samples to scientists that would compare that DNA with other samples from people with the same condition to figure out what the common thread was. Dr. Weleber also took a sample from my mother because the condition was recessive.
Once the culprit gene was discovered they could sequence it (figure out the amino acid and protein line-up, essentially the building blocks of the gene) and synthesize a working replacement gene to give to children born with the condition. They might even figure out how to restore my vision through cellular/genetic therapy (I'm a little fuzzy on the details of how that works). This is, of course, decades down the road but it's at least on our horizon!
During the last couple of visits I've made to OHSU Dr. Weleber had made noise about some condition he called SECORD, Severe Early Childhood Onset Retinal Dystrophy. SECORD is extremely similar to Leber's with the exception of not being progressive (patient does not lose vision over time) at all and having to do with deficiencies in the cilia, a thin cellular layer between the two layers of optical receptors in your eye. This is just about as close to my condition as it gets so I FINALLY have a diagnosis! I have SECORD.
Recently updated to CRB-1-SECORD-LCA. Translation, the CRB-1 gene is what has caused Severe Early Childhood Onset Retinal Dystrophy, which is categorized as a rare form of Leber's Congenital Amaurosis. What a mouthful!
Now, to this last Tuesday. An eye exam at OHSU, but not a normal one. A normal appointment goes something like this:
1. Visual Field Test--mapping peripheral (or lack thereof) vision: The patient is seated at a table, upon which rests a somewhat squarish satellite-dish-shaped apparatus. The apparatus has a chin and forehead rest at the open end of the dish, at the center of which is a green light fixation target. The patient stares at the fixation target as a series of other computer-programmed lights appear in fixed locations at varying distances from the central target. When the dot reaches a visible brightness and appears close enough to the central point that the patient can see it, the patient clicks a button on a hand-held buzzer that sends an electrical impulse to the computer to mark the location of the visible dots around the central target point on a map. This map can be used to represent the patient's degree of peripheral vision. This test is done separately for each eye. The test continues when the technician uses the computer mouse to then take manual control of the dot of light and move it slowly across the fixation target in and out of the patient's field of vision. The patient clicks the buzzer thingy any time he or she sees the light and more data is collected. The data from this test can be used to represent a patient's ability to track moving objects, or to create another peripheral vision map, measuring the eye's ability to perceive movement ("out of the corner of her eye, she saw movement") This map is then usually overlayed with the one made by the previous test. The previous is generally referred to as a static field test and the second a kinetic test. Each one is done once for each eye so a total of 4 field tests are conducted in all.
2. Optical exam: "look at the chart, what do you see?" Yep, that one. This is your basic visual acuity test. Unfortunately, I was born with my dad's "beat the test" instinct, which should not apply to eye tests. For years, without realizing it, I had sat in that big chair and stared at the letters on the eye chart subconsciously calculating the odds that the circular mark was a C, O, or G. This, however, produces false results, and I had routinely scored higher on the acuity test than I should have. Once, I even scored as high as 20/60 instead of my average 20/200! When we got the results, Mom looked them over and then made the technician administer the test again because she'd figured out what I was doing. Since then I have concentrated on responding as quickly as possible to avoid thinking too hard about it. The goal is not a high score, but an accurate one. I'm probably closer to a 20/250 but I'm still teaching myself how to not involuntarily 'beat the exam.' *
3. Optical probe: this is the one where they dilate your eyes and then flash lights and lenses in front of you. Only for me, the dilating drops my doctor uses on my eyes are so powerful that they have to add two numbing drops to each eye before they add the dilating agent. Six drops total, and after the dilation reaches its peak any exposure to light is extremely painful to me for about twelve to eighteen hours. So, of course, as soon as my eyes are hyper-sensitive to light Dr. Weleber starts flashing bright little light-bulbs and lenses in my eyes!
*NOTE: Visual Acuity Scale/LogMAR chart
On these regular exams Dr. Weleber would occasionally take blood samples to send back to the lab in Iowa, or have a technician take digital pictures of my retinae when they were sufficiently dilated (NOT a pleasant experience, I saw after-images for hours!) These appointments lasted two, sometimes three hours.
THIS Exam:
1. Visual Field Test--same as above
2. Optical Exam and Probe: same as above, plus several extra drops for prep-work on the next section. At this point I've had 6 drops per eye, 12 total.
3. ERG, Electroretinograph: The fun part...add three more drops per eye, total of 18. The ERG tech clips an electrical grounding wire to my ear (after I remove my earrings) and then slides a plastic contact-electrode over each eyeball. It's like a giant contact lens with an electrode and a wire attached to it (yes, I had wires coming out of my eyes). Right eye first, followed by left eye, same procedure. Then she had me stare at a screen with randomly scattered hexagons on it. "Stare straight at the center of the screen--there's a little red X there but you can't see that. It's going to flicker and rearrange the hexagons very rapidly for about a minute. During that time the electrode will feed data back into this other computer over here. You just sit there and stare at the X you can't see. We'll do 8 of these tests per eye." The whole flickering and randomizing thing would have been quite hypnotic if I hadn't had an electrode stuck into my eye at the time. 16 tests later the technician guided me around the corner into an adjacent room and slid an electrode contact into each eye (plus 4 more eyedrops, 22 total now). Same routine, different screen, both eyes at the same time (previously the electrodes measured each eye separately).
4. Genetic Counseling: Yes, my genes have an identity crisis, they need serious counseling....just kidding. The genetic counselor's job is to inform me that a new laboratory is opening up in San Diego. If the Iowa lab doesn't sequence the Cep-290 gene (the one that Dr. Weleber says is causing my problems) within the year then Dr. Weleber would like my permission to send my DNA down to the new lab to get it done. So I got to sign a form and the vampire--I mean technician--got to suck some more of my blood.
I have since learned that genetic counseling is provided to make patients aware of their rights concerning genetic testing. For more information and history on this subject, read The Immortal Life of Henrietta Lacks by Rebecca Skloot.
5. Optical Coherence Tomography (OCT): We're graphing Tom's! Not quite, actually. This is the light-wave version of an ultrasound imaging process. I stare into another chin-rest/foreheat-rest apparatus facing into a little black boxy thing. At this point my eyes are so gooped out I can't really tell what the thing is. Inside the boxy thing a blue light expands into a nebulous luminosity, has a line going through it, moves around, changes size, and there's a red line above it. Essentially I stare into this vortex-ish light setup and blink whenever the OCT technician asks me to. This gives them a light-wave-generated image of my retinae, optical nerve, and cilia layers by bouncing light waves off of my retinae. OCT uses the same technology that astrophysicists use to look at the surface of distant stellar bodies like stars and planets--how cool is that? OCT is a system that I believe Dr. Weleber himself designed, and allows him to generate a three-dimensional image of the retina.
So.........all of this gadgetry and goopery is theoretically going to help Dr. Weleber develop methods of curing and preventing various retinal degenerative conditions. I told Dr. Weleber that he couldn't cure me until Prada retired 'cause I loved her too much and it wasn't fair to retire her early, and he assured me the solution to this whole mess was still a decade or three down the road. No worries there. Oh, and all this mess took about...8 hours. By the time I left there my eyes were so sore and sensitive that I had to hide in my parents' room with black-out curtains at home and couldn't look at ANYTHING. Lights off, no screens...
-exhales heavily- ok, got all that out. Sorry about the avalanche, there. If y'all have more questions about this material as always you are encouraged to ask whenever you like and I will answer and/or provide supplemental resources as soon as I can.
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