(Naval.txt) A PROPOSED NAVAL STUDY: THE ANNAPOLIS PILOT VISION MAINTENANCE PROGRAM A Preventive Proposal for THE UNITED STATES NAVAL ACADEMY Otis S. Brown General Electric, Space Division Goddard Space Flight Center Greenbelt, Maryland 20771 Dr. Peter R. Greene Department of Biomedical Engineering Homewood Campus THE JOHNS HOPKINS UNIVERSITY Baltimore, Maryland 21218 THE ANNAPOLIS PILOT VISION MAINTENANCE PROGRAM This proposal is dedicated to the Midshipman's right to make a decision regarding myopia avoidance. Topics for Discussion 1. Abstract 2. Background 3. Objectives 4. The Prevention Technique 5. Cockpit Myopia 6. Specific Instructions to the Midshipman 7. A Dichotomy in Eye Research and Method of Practice 8. The Right of the Midshipman to make a Decision Regarding Nearsightedness Avoidance 9. Scientific Rigor Vs. The Midshipman's Right to Know and Choose 10. The Placebo Summary 11. The Group Affected 12. The Cost of the Program 13. The Principal Investigator 14. Two Theories of the Eye's Focal Growth 15. Scientific Measurement 17. Summary 16. A Physiological Model for Demonstration 18. References THE ANNAPOLIS PILOT VISION MAINTENANCE PROGRAM ABSTRACT The Naval Academy requires 20/20 vision for admission of freshmen. Prospective pilots are required to have 20/20 vision on graduation from the Academy. A substantial number of midshipmen, entering with 20/20, become nearsighted during their four years of study at the Academy. An engineering analysis of the eye's control action predicts that a large percentage of the midshipmen could -- in fact -- avoid the problem if they wear convex lenses while reading. This analysis is supported by direct experimental evidence. (l) (2) BACKGROUND 20/20 does not fully define the eye's focal status. A more meaningful measure is a quality described as "hyperopic reserve". The quality is easily measured with an eye chart and a positive (convex) lens. In a study at the Naval Academy, conducted by Dr. Hayden, it was determined that the confined (reading) environment resulted in a steady movement towards and into myopia. (3) This movement towards nearsightedness is not measured in the eyes of primitive (Eskimo) men. (4) If the visual environment of the midshipmen is changed from a near environment to a "far" environment by use of a positive lens for reading, the movement towards myopia will stop, and the midshipmen will avoid the problem of myopia. (5) OBJECTIVES The major objective of the proposed program is to demonstrate that midshipmen, who are on the verge of becoming nearsighted, (zero diopters hyperopic reserve) will completely avoid the problem. It has been documented that military cadets will develop approximately 1.3 diopters of nearsightedness after four years at the West Point Military Academy, if no preventative action is taken. (7) The objective of the prevention technique is to demonstrate that at least half of the midshipmen who assiduously wear the plus lens will avoid becoming myopic during their four years at the academy. The 50% figure is a minimum acceptable performance figure -- the actual results should be considerably better. THE PREVENTION TECHNIQUE The reading (confined) visual environment can be neutralized by a positive lens. The convex lens makes diverging rays of light parallel, thus simulating the effect of a "distant" visual environment. The eye's internal lens is thereby adjusted to infinity, rather than the actual near-by object. The specific lens strength chosen will be determined by the midshipman's habitual reading distance. For instance, if the habitual reading distance is 20 inches, a lens with focal length of 23 inches (+ 1.75 diopters) will neutralize most of the "near" visual environment. Obviously, habitual reading distance determines the selection of the convex lens strength. A POSITIVE LENS MAKES DIVERGING RAYS OF LIGHT PARALLEL THUS SIMULATING A DISTANT OBJECT FOR THE EYE COCKPIT MYOPIA The wearing of a convex lens for reading will have one immediate beneficial effect - - the ending of the problem of cockpit myopia. This condition occurs after prolonged close work. When the individual looks up, distant objects are blurred, and it can take a considerable amount of time before distant objects become clear again. By wearing a positive lens for all close work, the accommodation system is already set at infinity, and the eye will be in immediate clear focus for distant objects, thus completely ending this particular problem. SPECIFIC INSTRUCTIONS TO THE MIDSHIPMAN Once the positive lens is chosen, the Midshipman must be instructed to push his reading material away from his eyes until the work blurs -- accommodation set at infinity -- and then move the work inward slightly. This procedure will effectively place the reading material at infinity, so that the positive lens will have the maximum neutralization effect. If he does not do this, he may inadvertently hold his work somewhat closer than necessary -- which will partially negate the effeect of the positive lens. THE DICHOTOMY IN EYE RESEARCH AND METHOD OF PRACTICE There are two major opinions held by the eye care profession. They are: 1. The Negative-lens Theory: The visual environment and/or lens has absolutely no effect on the focal status of the normal eye. 2. The Dynamic Theory: Both the visual environment and/or a lens have a direct bearing on the eye's focal status. The eye continually sets its long-term focus by reference to the average value of accommodation. These two contradictory opinions result in two contradictory methods of practice. 1. The eye becomes nearsighted -- not because of a near environment --but by pure genetic cause. Since this factor makes nearsightedness incurable, no attempt should be made to solve the problem, and when the eye fails the eye chart, a negative lens must be prescribed. 2. The preventative (positive lens) technique advocates nearsightedness avoidance by neutralizing the effect of a confined visual environment. This technique -- or some variant -- is used by 20% of the eye care profession. Nearsighted avoidance (and recovery) is a recognized technique that is established by the fact that it is practiced by 20 percent of the profession. THE RIGHT OF THE MIDSHIPMAN TO MAKE A DECISION REGARDING NEARSIGHTEDNESS AVOIDANCE Since midshipmen with hyperopic reserve of 0 to + 0.25 diopters will become nearsighted one or two years after matriculation, it follows that the midshipmen who wish to enter Naval Air on graduation should be given the opportunity to make the decision to avoid becoming myopic by use of the positive lens technique. The visual records of the incoming class should be culled for visual focal status from 0 to + 0.5 diopters, Those individuals in this group shall be informed of their right to make this decision. Once the decision is made by the midshipman, his focal status shall be monitored to verify the effectiveness of the preventative technique. SCIENTIFIC RIGOR VERSUS THE MIDSHIPMAN'S RIGHT TO KNOWN AND CHOOSE The major purpose of this study is to provide the midshipman with the opportunity to avoid myopia. A further purpose is to provide him with the supporting focal status measurements obtained from his own eyes, to validate the effectiveness of the technique. To carry out the preventative technique, the cadet must be given information regarding the characteristics of a plus and minus lens -- and the expected results of these two techniques. The availability of this information will preclude the use of placebo (plate glass) group, since the placebo group will quickly become aware that their lens can have no effect on their developing case of nearsightedness. Not all of the 300 midshipmen who are in imminent danger of becoming nearsighted will wish to be part of the preventative group. This group will be the control group. This group will only establish a fact that is already known -- that if you do nothing, your focal status will move towards nearsightedness at the rate of 1/3 diopters per year. (3) THE PLACEBO SUMMARY The right of the midshipman to know and to choose is more important than the need for a placebo group. The standard rate of focal change (-.33 diopters per year) is an already known value. The placebo group would interfere with our ability to provide information about the use of the plus lens -- which is essential for the success of the project. The midshipmen who are not part of the preventative program will serve as the placebo group. THE GROUP AFFECTED The Naval Academy accepts 1,000 freshmen per year with 20/20 vision. This group has an approximately gaussian distribution of hyperopic reserve -- from 0 to +2.0 diopters. Approximately 30% of this group will have hyperopic reserve of from 0 to +.5 diopters. (i.e. They are on the edge of nearsightedness.) Almost all midshipmen in this group will become nearsighted if nothing is done. This fact is confirmed by a previous measurement study conducted at the Naval Academy. (3) This group will be identified from their visual records, and will be given the opportunity to join the myopia avoidance effort. THE COST OF THE PROGRAM The preventative (positive) lens is relatively inexpensive, since it is a "standard" item available in larger drug stores for about $8. The initial outlay is relatively modest to support the program. In addition, these lenses need not be changed for the 5 years of the program. The midshipmen who avoid nearsightedness by the prevention technique, will also avoid the expense of prescription ground lenses which typically sell for $40, and are changed every one or two years. The prevention technique will result in a considerable dollar saving for the Naval Academy. THE PRINCIPAL INVESTIGATOR Dr. Karel Montor; Director, Division of Applied Sciences, USNA, is conversant with this proposal. We recommend that he be asked to serve as the principal investigator. TWO THEORIES OF THE EYE'S FOCAL GROWTH Nearsightedness is a medical problem, but it points to a much broader scientific question: "How does the human eye achieve and sustain a high level of focal accuracy?" There are only two possible explanations. 1. The Negative-lens Theory: The eye's long-term focus is genetically controlled. All optical components are pre-determined from birth. 2. The Dynamic Theory: The eye is subject to continuous focal micro-perturbations. The effect of these perturbations is to randomize the eye's focal status. The eye has a long-term focal control system which is directed by the accommodation system. Only the existence of a focal dynamic system can account for the high level of accuracy seen in the human and primate eye. These two theories are reasonable, but they lead to predictions that are directly contradictory. A scientific approach calls for the testing of two theories by direct experimentation, Dr. Francis Young has carried out a visual environment test on monkeys. A theoretical review of this experiment demonstrates that the predictions of a dynamic theory are an order of magnitude more accurate than the negative-lens theory. (2) The theory that has the greater predictive accuracy ultimately becomes the preferred theory for scientific research. Once initial confirmation is obtained, effective analysis of the eye can be obtained by use of a dynamic control theory. SCIENTIFIC MEASUREMENT The eye responds to the environment (6). The eye's focal status will, necessarily, move towards nearsightedness if placed in a confined visual environment. The purpose of the plus lens is to substantially alter the eye's average value of accommodation. The equation which relates the average value of accommodation to the eye's focal status is: Focus = Focus + ( Offset + Accommodation - Focus ) - Perturbation ---------------------------------- TAU (This is an iterative equation) The required parameter for this equation is the eye's average value of accommodation on a daily basis. Since the midshipman is mature enough to monitor his usage of a plus lens, we can ask him to estimate: 1. The number of hours per day that he spends looking at distant objects. (i.e. Athletics) 2. The number of hours he spends doing close work, and the number of hours he actually used the plus lens to neutralize the confined visual environment. To calculate the eye's focal status we need to know: 1. The distance he holds his reading material from his eyes, and the strength of the plus lens. 2. The number of hours he uses the reading glass for close work. From this supplied information we will calculate: 1. The midshipman's average visual environment. 2. The midshipman's visual environment if he had not worn the plus lens. By use of the piecewise (iterative) equation we may then predict his eye's focal status, and compare the measured focal status against the predicted focal status. It should be clearly understood that the predictions of the iterative equation have previously been confirmed by direct experimental work with monkeys. (l) (2) SUMMARY Nearsightedness prevention is a difficult problem. It will take a major commitment to carry out an effective prevention program, testing whether the negative-lens or dynamic eye concept is the correct (most accurate) theory for the long-term growth of the eye. We have limited resources to deal with the problem. We should not divide our efforts. Either the plus lens is or is not effective in halting the movement towards myopia. An effort to prevent myopia should produce clear results that allow us to conclude: 1. The plus lens is effective, and because of its demonstrated effectiveness, its use will be continued on a permanent basis. 2. There is absolutely no possibility that the plus lens has any effect on a developing case of nearsightedness. The predictive accuracy of a negative-lens theory is an order of magnitude more accurate than the predictive accuracy of a dynamic theory. A PHYSIOLOGICAL MODEL FOR DEMONSTRATION In order to explain the eye's dynamic action with clarity, it would be reasonable to build either an electronic or mechanical analog of this system. The building of a dynamic model is an option which could be pursued after the start of the nearsightedness prevention program. REFERENCES 1. Young, F. THE EFFECT OF RESTRICTED VISUAL SPACE ON THE PRIMATE EYE. American Journal of Ophthalmology, Volume 52, N.5, Part II (11/61) 2. Brown, 0. Young, F,, THE RESPONSE OF A SERVO CONTROLLED EYE TO A CONFINED VISUAL ENVIRONMENT. The 18th Annual Rocky Mountain Bioengineering Symposium. Laramie, Wyoming (4/81) 3. Hayden, R. DEVELOPMENT AND PREVENTION OF MYOPIA AT THE UNITED STATES NAVAL ACADEMY Archives of Ophthalmology Volume 25, (4/41) 4. Young, F. et al, THE TRANSMISSION OF REFRACTIVE ERRORS WITHIN ESKIMO FAMILIES Am. J. Optometry. & Arch. Am. Acad. Optometry., 49 (9): 675-685, 1969 5. Brown, 0. Young, F. THE EYE'S SERVO RESPONSE TO A CONVEX LENS The 10th Annual Northeast Bioengineering Conference (Submitted for publication) (4/82) 6. Brown, 0. Young, F. Berger, R, MEASURING THE EYE'S FOCAL ACCURACY: A HEURISTIC APPROACH, The 3rd Annual Conference of the IEEE Engineering in Medicine & Biology Society (9/81) 7. Gmelin, R. T., MYOPIA AT WEST POINT: PAST AND PRESENT, Military Medicine 141 (8) 542-3 (Aug 76) (Measurements made over a 4 year period indicate that the average movement towards and into nearsightedness is -1.37 diopters, with a range of -1.12 to -1.69 diopters.) cc: Dr. Karel Montor Director: Division of Applied Sciences Chauvenet Hall The United States Naval Academy Annapolis, Maryland 21402