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Chapter 1
INTRODUCTION

Goals of this CD-ROM
As optometrists there are two general areas of knowledge in this course that you want to take away with you.  You're entering optometry at a time when there is a remarkable increase in the breadth of responsibilities of the profession.  Optometry is becoming a primary care provider and Optometrists serve as medical gate keepers.  They are responsible for detecting a wide variety of health disorders and refering their patients to the appropriate health care specialists.  Currently the areas in which Optometrists are trained to have expert diagnostic abilities include ocular pathology of the cornea and retina resulting primarily from systemic disease and degeneration of the retina and pigment epithelium.  Another relevant area is neurology in which you observe oculomotor disorders and diagnose anomalies of the central nervous system.  These anomalies can be congenital, developmental, or acquired.  This latter category includes a whole host of disorders including traumatic and toxic injuries, systemic and invasive diseases, and growths such as tumors.  Generally the congenital and developmental problems need attention to prevent any unnecessary interference with the normal developmental process and to improve the general quality of life.  The acquired problems need more urgent solutions because they can be life threatening.

The Optometristís job is to decide how urgent the condition is and who to send the patient to if further diagnosis or treatment is needed.   This needs to be done without alarming the patient unnecessarily.  This can be a very difficult problem because most of the obvious problems are detected by the patient themselves and they then self-refer to a neurologist.  An Optometrist must detect more subtle disorders.  An example of an obvious disorder is a patient who wakes up with ringing ears, vertigo, nausea, diplopia and uncontrolled head and eye movements and a severe headache is unlikely to run to the optometrist for help. 

This CD-ROM presents digitized video of some of these common neurological syndromes seen by neurologists that typify serious central nervous disorders.   The video also shows rare and subtle disorders such as ocular flutter that the patient may be totally unaware of.  For example, while conducting the standard eye mobility confrontation test a patient exhibits a slight horizontal flutter movement of her eyes when she attempted to followed a pen light upwards.  It was very subtle and she had no specific complaints about her eyes.  A neuro-ophthalmologist found  an operable tumor in the cerebellum.  Generally, ocular flutter is a sign of cerebellar tumors.  FMRI machines reveal these problems with little difficulty. 

An example of a less severe but common problem is paresis of an eye muscle due to head trauma.  The 6th nerve has the longest and most tortuous pathway of all ocular cranial nerves and is the most susceptible to trauma.  Yet you will probably never see one of these cases because the effects of marked esotropia are so obvious the patient usually self-selects an ophthalmic surgeon or neurologist to deal with the problem.  The most common motor paresis seen by Optometrists is the superior oblique due to damage to the 4th nerve.  These patients complain of transient diplopia which many can avoid with adopted head tilt postures.  Multiple sclerosis, the young adultsí disease, is another problem that Optometrists encounter in clinical practice.  It is a demyelination disease that is thought to be an autoamune disorder.  It can strike the CNS anywhere and therfore is hard to diagnose.  These problems are more subtle and are revealed during an optometric examination.  You're not going to get the easy cases, only the hard ones.

This CD-ROM will take you beyond the level of the cranial nerves into the programmed nuclei of the brain stem, the repair shop of the cerebellum, the posture-sensing vestibular system, the higher centers including the colliculus, occipital lobe, and frontal eye fields.  We will see what anomalies affecting these various regions look like and at the same time we will learn about their normal function.

The second facet of this CD-ROM is to provide expertise about the near response which is composed of accommodation, convergence and pupil constriction.  This near triad is interesting because stimulation of either accommodation with a lens or convergence with a prism evokes a response from all three motor components of the near triad.  Thus the three motor responses are cross-coupled.  This ensemble response is called a synkinesis or cross coupling and many problems arise because of excessive use of one system such as accommodation and its influence on the other components of the near triad.  For example suppose you are very hyperopic and you need lots of extra accommodation to see clearly at all distances.  This excessive accommodative effort could stimulate too much convergence and cause an accommodative esotropia (crossed eyes associated with accommodation effort).  Treatment consists of corrective lenses for the hyperopia, sometimes a bifocal to minimize accommodation at near distances, and eye exercises to enhance divergence so that it can compensate for excessive accommodative convergence.

If you want to appreciate this problem, just consider how hard it is to see depth in an autostereogram.  To fuse the figure properly and see the hidden stereo figure you usually need to uncross or diverge your eyes while you increase accommodation to focus the near target.  Thus you are diverging while you accommodate.   Given how hard this is to do, its amazing how popular these autostereograms have become.  Now imagine a patient who needs to perform these ocular gymnastics just to see the natural world.  Normally they avoid reading or give up stereopsis and simply suppress one eye, often without any conscious awareness.

Traditionally this area is considered as a cornerstone of Optometry.  It is an area where other professions, including ophthalmology, look to us for expertise.  Topics include infantile esotropia, accommodative esotropia, heterophoria or binocular imbalance, presbyopia, amblyopia, and motor problems associated with anisometropia.  Basically these are common congenital and developmental disorders.  You need to learn how to quantify the cross-link interactions, to evaluate the source of any weak or excessive interaction, and come up with ways to allow people to see clearly and singly at the same time using lenses, prisms, and eye exercises. 

Texts
The text material presented in this CD-ROM is suggested as the requirements for a course in Ocular Motility.  In addition, two textbooks are recommended: Adlerís Physiology of the Eye (9th edition) and Neurology of Eye Movements by Leigh and Zee.  The Adler text will be invaluable for National and State Board Exams, and the Neurology text will serve you as a reference book throughout your optometric career in private practice.  Several other textbooks are excellent resources for information of ocular motility:
 

  • Borish, Clinical Refraction.
  • Carpenter, RHS.  Movement of the Eyes.
  • Carpenter, RHS, Ed.  Eye Movements: Volume 8 in Vision and Vision Dysfunction.
  • Davson, The Eye, Vol 3
  • Grisham D. Management of nystagmus in young children in Problems in Optometry Vol 2, Number 3,
  • September 1990. Eds Scheiman and London, Lippincott p  496-527.
  • Miller, NR.  Walsh and Hoyt's Clinical Neuro-Ophthalmology.  Fourth Edition.  Volume Two.  Sections III and IV.  Baltimore: Williams and Wilkins.  1985.
  • Ogle, Martens, and Dyer, Binocular Oculomotor Imbalance.
  • Rosenbloom and Morgan, Principals and practice of pediatric optometry.
  • Schor and Ciuffreda, Eds. Binocular Vision: Basic and Clinical Aspects.


Preparation & Review
As preparation for the material presented in this CD-ROM, you may wish to review notes from Geometric Optics, Ocular Anatomy, and Neuro Anatomy courses.  The main aspect of your optics course to review is the Gaussian equation that predicts the image distance given object distance and focal length of a plus lens.  This knowledge is necessary when studying accommodation (and also if you conduct labs in which you measure the accommodative response with a Badal optometer).  You may also wish to review material on the origins and insertions of the 6 ocular muscles, primary, secondary and tertiary actions of these muscles, their cranial nerves, the substructure of striated muscle, the anatomy of the ciliary body, iris, lens zonules, lens capsule, and lens body.  You will also find it helpful to review material on pupil anomalies and some of the tests you conduct to analyze paretic muscles.

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