A Bench-to-Bedside Pipeline Story
L.F. Dell’Osso, Ph.D.
I study eye movements from an engineer's control system point of view and specifically study ocular motor oscillations (nystagmus and saccadic). In my thinking and modelling, I consider mainly function and signal/information processing, rather than anatomy.
In 1978 I was documenting the effects of the Anderson-Kestenbaum surgery on patients with congenital nystagmus (CN). Briefly, the extraocular muscles are cut off the globe and relocated in such a way that patients who used a head turn to look at things at a gaze angle where their CN was minimal could then do so while looking in primary position. It's described as moving the null region to straight ahead. My data showed that in addition to doing that, the operation also reduced (damped) the CN over a broader range of gaze angles than the preop null region and also damped the CN at gaze angles lateral to the null.
These secondary benefits were not previously known and were unexplained. After getting a description of just how the surgery was done, I hypothesized that the simple act of cutting the tendon off the globe and sewing it back was causing these beneficial secondary effects. I further reasoned that for the many CN patients who did not exhibit a null region and had no surgical option, a simple "cut-and-sew" procedure would damp their CN, allowing better vision.
Waiting in the Pipeline: (1979 – 1992)
Needless to say, no surgeon was eager to operate and ‘do nothing’ (medical-legal fears) so I continued my nystagmus research while looking for an animal model.
Later in the Pipeline: (1992 – 1998)
It wasn't until about 14 years later when studying achiasmatic Belgian sheepdogs with CN in Memphis that I had the opportunity to put my old hypothesis to the test. I convinced an ophthalmologist/friend (Rich Hertle) to forgo his lucrative practice income for a few days and fly to Memphis at his own expense to try my 'tenotomy' operation out on the 4 horizontal rectus muscles of the last dog we had, before he was sacrificed for anatomical studies. He assured me it wouldn't work but humored me and, with me as an assistant, performed the surgery while continually stating that it could not work and would be mal-practice if he were doing this on a human (it's all on video tape).
The next day we checked on the dog in the animal facility and his eyes were almost still. Rich insisted that the lack of nystagmus was due to the anesthesia, which he claimed had not worn off. I said, "Fine, we'll check again tomorrow." Well, the CN was still very small and the dog's behavior was suddenly more like that of a normal dog, so much so that the caretakers thought we had switched dogs on them. Since the dog also had vertical see-saw nystagmus (SSN) I convinced him to meet me in Memphis four months later to do the tenotomy on the 4 vertical recti and 4 oblique muscles. The results were even more spectacular; no SSN remained.
The light at the End of the Pipeline: (1999 –2003)
On the basis of my original hypothesis from human data and that one dog, the NEI sponsored a masked clinical trial on 10 adults and 5 children with CN. The positive results (improved CN waveforms and visual function) was published for the adults and are in press for the children. I hypothesized that we had interfered with a proprioceptive feedback loop that maintains muscle tension, effectively reducing the small-signal gain of the ocular motor plant to the central nystagmus signal. The anatomists said, "that can't be; there are no neural cells at the distal end (enthesis) of the tendon." I replied, "look again." Well, they did and there were. There are all manner of neural cells there, supporting my hypothesis. I further hypothesized that since this mechanism is independent of the specific type of nystagmus, it should work for acquired types and reduce intractable oscillopsia. Again, the naysayers (this time ophthalmologists and neurologists) said that it would not work because CN was 'different' than acquired (adult) nystagmus, ignoring the hypothesized mechanism of action which was independent of the type of nystagmus.
We recently tried out the tenotomy procedure on an adult with MS, acquired pendular nystagmus and intractable oscillopsia and reduced his nystagmus by 78%. We now have a viable therapy for acquired nystagmus and intractable oscillopsia.
Dr. Story Landis, in a lecture a Case Western Reserve University, said that although highly desirable, actual stories of research that led directly from the lab to the bedside were rare. Those who demand ‘relevance’ of research do not understand research or how its results often prove useful in ways not envisioned by the investigator. Never-the-less, the above sequence of events constitute such a story with promising benefits to patients with nystagmus.