reader and industry forum
What Keratoconus Patients Say and Interpreting What's Said
BY BEZALEL SCHENDOWICH, OD, FIACLE
While we all know detail by detail what keratoconus looks like, how many of us pay enough attention to our patients to understand what keratoconus sounds like? With each patient presentation and follow-up visit, we meet daily with countless varieties of subjective patient observations. Aside from our professional interest in clarifying vision, we have the responsibility to allay fears attendant upon progressive reduction of visual acuity.
Keratoconus Patient Sayings
I have compiled a list of 10 of these presentations, many of which occur with GP lenses. The vast majority occur with patients whose vision had been so poor before the new lenses that the problems seem associated with the lenses and not with the disease. I will discuss my interpretation of these observations.
1. The right lens feels better than the left. One of my favorite keratoconus patients is a 72-yearold woman whom I've had the honor to treat for around 10 years. She had already been wearing contact lenses for many years when we first met. For various reasons, I began the refitting process. It was with this patient that I began to learn how relatively flat the midperipheral zone can become in a cornea that has a very steep, small, and central cone.
After redesigning her lenses, she would come in for follow ups and report that the "right lens is far more comfortable than the left." Upon examination I would see that the comfortable lens was bound through an impression ring to her cornea's flat midperipheral zone. It had become essentially part of her eye: there was no lens edge-to-lid interaction. The "bad" lens would show a very acceptable lens-to-cornea relationship with normal up-down translation. She would always be surprised when told which lens needed redesigning.
I learned many years ago by comparing topography maps that as cone apices steepen, the midperipheral zone flattens. I think that conservation of collagen fiber length in the stroma can at least partially explain this effect.
2. It hurts when I apply and remove my lenses. This pain is a symptom of a poorly designed or manufactured lens. The edge is too steep or sharp for the area of the cornea upon which it settles. The pain upon application results from the sharp edge scratching the cornea. After a while the lens is more comfortable as it begins to take a fixed position, so it becomes more like a part of the cornea than like a separate entity. The pain upon removal comes from prying the lens out of the cornea. For these patients, redesign or re-edge the offending lenses.
3. My vision is elongated obliquely. Commonly, patients who have high degrees of regular or irregular astigmatism that previously went uncorrected will report that their view of the world is stretched when you do correct their astigmatism, even partially. Some say that this is the view of the world that El Greco shared with us in his paintings.
4. My vision is swimming. A contact lens that exhibits acceptable translation can give a patient the feeling that his vision is moving unstably as tear fluid moves around his cone under the lens when he blinks. You could consider redesigning the lens to stabilize the fit for such patients.
5. My vision is hazy. There are several possibilities to explain the observation of hazy vision. The obvious first choice is haze on the surface of the lens, which occurs when debris (primarily protein) has built up on the lens surface. Additional sources of debris are other dried tear components, mascara or other makeup, and finger grease.
In addition, haze might be the perception of dimple veiling over the pupil. Dimple veiling is a common finding in mild-to-advanced keratoconus that results from a large lens that rests too flatly on the cone apex. A fairly deep tear pool will inevitably develop superior to the touch-point. This is one of the great contact lens incongruities: to treat a relatively steep area — the pool superior to the cone apex — you must steepen the lens and possibly reduce the optic zone diameter to conform more to the cone apex. Also, the secondary curves must be flattened to begin following the much flatter periphery. This combination will reduce the sagittal height over the tear pooling location and thus reduce the tendency for dimple veiling.
6. There's "spit" under my lens. One of my patients claimed that using his post-graft lenses gave him the feeling that he was looking through saliva. Upon examination he had a thick froth under his lenses that was an excellent copy of what saliva might have looked like. And no, he never wetted his lenses in his mouth.
7. I see (more than) double. Around 20 years ago we began treating a patient who, from the moment he began lens wear, reported monocular diplopia that he had never noticed prior to lens wear because of the pronounced blur from the keratoconus. Over the years we tried redesigning his lenses, but we never managed to resolve his diplopia.
This year, we fit a bi-aspheric design. Using it as a monovision fitting, we resolved both the diplopia and the incipient presbyopia simultaneously.
Incidently, some aesthetically inclined patients may find that monocular multiplopia can offer an enhanced view of life. Some keratoconus patients have reported that on winter nights they enjoy viewing holiday season tree lights that appear multiplied so as to reach in number that of the stars.
8. I see haloes around lights (especially when driving at night). This complaint has driven many keratoconus patients to abandon nighttime driving. The irregularities of a keratoconic cornea's topography play many refractive tricks with the patient's vision. Areas of pooling and minimal clearance under a firm contact lens as well as various areas of thinning all provide different degrees of focus and defocus. During the day a normal pupil constricts, reducing the entrance of peripheral light and allowing more refined sight through the pupil's center. Under mesopic to scotopic conditions, a mildly dilated pupil allows more peripheral rays to enter the pupil along with a variety of refractions that will not all come to a focus on the retina. The resultant perceived blur is observed as haloes around lights.
9. After a long lens-wearing day, my eyes will not bear my contact lenses the following day (or two). We understand this patient to be essentially overwearing his contact lenses, pushing his wearing time in an attempt to achieve new records for contact lens-on-eye time. He manages to reach the wee hours with some minor irritation, but he is too tired to bother much about it. The next day he is again successful, but within a few days the minor insult that his epithelium is constantly suffering will cause his eyes to seemingly reject the contact lenses.
This patient needs a break from lens wear or at least severely reduced wearing hours. He also needs re-instruction regarding a more structured use of his lenses.
10. Last month I had several bad contact lens days. Differing somewhat from the good eye days and subsequent bad eye days of contact lens overwear is this story that your 'normal hours' patient reports. On the basis of observations I made of one of my patients who suffers from a clearly cyclic case of keratoconus (in the Readers' Forum article "A Case of Cyclic Keratoconus" from the December 2008 issue), I would like to surmise that cyclic keratoconus exists more frequently than might be supposed and that a "well-fitting" lens that spontaneously becomes unwearable and then comfortable again is pathognomonic of this condition.
As eyecare practitioners working with patients who suffer from vision-distorting conditions, we need to understand what can cause these observations and others like them. We need to be able to explain them in terms our patients can understand, because understanding helps the distraught to cope. And finally, we need to be able to assuage as far possible these disturbances to sharpen vision and to reduce the frustrations that these patients face daily. CLS
The author would like to express a deeply felt thank you to his patients, without whom this article would not have been possible.
Dr. Schendowich is a member of the Medical Advisory Board of the National Keratoconus Foundation, a Fellow of the International Association of Contact Lens Educators and staff optometrist and specialty contact lens fitter in the ophthalmology clinic at the Sha'are Zedek Medical Center in Jerusalem, Israel.