NavRpt2 Subject: How Can You Predict Nearsightedness Development at a Four Year College? Re: A question from Sci.med.vision. Otis -- If a person is slightly myopic (20/25) at the time they reach college (the USAF Academy) what are the chances that he will become more nearsighted from the required reading load? Has the USAF run any experiments to find out about this nearsightedness change in their personnel? Bill. REFERENCES 1. Reynolds Hayden, M.D., "Development and Prevention of Myopia at the United States Naval Academy", Volume 25, (old series Volume 82), Number 4., The American Medical Association. 2. Gmelin, Maj. Robert T., MSC, USA, "Myopia at West Point: Past and Present." Military Medicine, 141 (8) 542-3 Dear Bill, Let me rephrase your question as follows. If you know the refractive status of an "entering" student, can you predict the resultant refractive state after four years? The refractive status is easily measured with a trial-lens kit. Once you know a person's refractive status you can predict the resultant status change (degree of nearsightedness after four years in college. If you check the person's focal status, and find it to close to "zero" or "plano", on entry, (20/20) -- then what is the probability that that person will retain 20/20 for the four years. The probability is about one percent -- as stated by Dr. Hayden, and confirmed by a study at West Point. (References 1 and 2) Note: The natural eye can have a negative or positive refractive status depending on the visual environment. A positive status is called "hyperopia" or "hypermetropia" and a negative status is called "myopia", "nearsightedness". Here is the information that I have on your question about "base-line data" concerning the behavior of the natural healthy eye at the Naval Academy. OVER-ALL SYNOPSIS OF THESE MILITARY STUDIES OF THE EYE'S DOWNWARD MOVEMENT WHILE IN A FOUR YEAR COLLEGE. The studies of military cadets in the United States have shown that their vision changes over the years of their academic work. Records reveal that a large percentage of the cadets (39% of those at the U.S. Military Academy in 1956) [2] became nearsighted and needed a negative lens by graduation. Further, of those who developed 20/25 vision, only one percent recovered to 20/20 over the four years, [1]. In early years the cause of their degraded vision not known, and later, on any number of factors wear speculated, but the upshot of these studies was that none of these circumstance were really behind the cadet's loss of visual acuity. The development of nearsightedness (negative change of focal state) was a result of the fact that the natural eye controls its focal state to its average visual environment. Roughly, that is looking close, studying, reading, looking at books, for long periods of time -- rather than at distant objects. SUMMARIZED STATEMENTS FROM DR. HAYDEN, REFERENCE 1 "...For many years the high incidence of myopia which developed among midshipmen after admission to the United States Naval Academy with supposedly normal vision was a cause of serious concern to all those interested." Dr. Hayden stated that many methods and efforts were made to "save" the men with previously perfect vision. "...and by retaining may of them (who became nearsighted) in the Naval Academy for one to three years in the hope that their vision would improve." "...In the vast majority of cases their vision did not improve, and the midshipmen was forced to leave the naval service after two to four years in the Naval Academy. Experience showed that only about one percent of such men had 20/20 on their final physical examination." [In summary -- if their focal status became even SLIGHTLY negative (20/25) they had virtually no chance of clearing their distant vision to 20/20. At that time there was no attempt to offer systematic use of a strong plus lens for the purpose of recovery and prevention. Otis Brown] "...Furthermore, an excessive number of junior line officers were being retired because of defective vision, and the records showed that the vision of 3/4 of these had become defection defective (negative status, vision less than 20/20 for each eye) at the Naval Academy." "...Any candidate, however, who if found to have any degree of myopia following the use of a cycloplegic, even -0.12 or -0.25 diopters is rejected." [There are two methods of measuring refractive status of the natural eye, eye chart and induced paralysis or cycloplegia. They produce slightly different values for the refractive status of the eye. OSB] NECESSITY OF A POSITVE REFRACTIVE STATUS (HYPEROPIC RESERVE) ON ENTRY AS DEFINED BY DR. HAYDEN [I have paraphrased this rather long section. OSB] A review of the refraction of the eye of candidates at the time of preliminary entry physical examination showed that the great majority of candidates whose refraction was of the plano-type, (refractive state 0.0) to +0.25 diopters). At the first year their examination a significant number would show that they had myopia. Occasionally a candidate who showed as much as +0.5 diopters "hyper-metropia" on preliminary physical examination was found to have become -0.25 diopters of myopia in the first year. DR. HAYDEN STATES THAT EMMETROPIA IS NOT NORMAL FOR THE FOLLOWING REASONS [EMMETROPIA IS DEFINED AS NORMAL OR PERFECT BASED ON THE DONDERS-HELMHOLTZ CONCEPTUALIZATION -- OSB] "...As is well known, the emmetropic eye is for practical purpose is an abnormal eye -- the great majority of persons with so-called normal vision being actually hyper-metropic. Those candidates, then, whose refraction was of the plano (emmetropic -- focal status exactly zero) had borderline conditions definitely on the way to myopia. For all practical purposes, experience here has shown that patients with +1/4 diopters of hyper-metropia are in the same class." "In view of the experience at the Naval Academy during the past three years as described, it is evident that a reserve of preferably one diopter or at least 1/2 diopter is necessary at the time of preliminary refraction to be reasonably sure that the candidate will pass his physical examination for admission." "Furthermore, in order to be reasonably sure of being visually qualified for a commission in the line of the Navy after four years at the Naval Academy -- it is necessary that the student have a reserve (positive refractive status) of at least one diopter of hyper-metropia at the time of admission." "Of course, an occasional candidate will +1/4 to +1/2 diopter of hypermetropia at the time of admission will survive visually after four years and receive a commission, but that is exceptional." DR. HAYDEN THEN DISCUSSES ATROPINE A DRUG FOR INDUCING PARALYSIS FOR PURPOSE OF MEASUREMENT. He details the loss of people in various classes who were "emmetropic" (focal state zero) on entry, using various drugs and percentage mixtures of those drugs. It was hoped that different drugs would produce better results and these emmetropic eyes could be "saved". However the drug of choice for measurement and the results were the same. DR. HAYDEN PROVIDED SOME ADDITIONAL DISCUSSION OF ILLUMINATION LEVELS AND EFFORTS TO IMPROVE THESE LEVELS, BUT CONCLUDED THAT THIS HAD NO EFFECT. CONCLUSION BY DR. HAYDEN "It is considered that during the past three years the Naval Academy has definitely proved the necessity of midshipmen having a "hyperopic reserve" of at least one diopter at the time of admission to the Naval Academy, and of their meeting the present visual requirements if the visual standards of the Naval are to be maintained." "...Any candidate having less than 1/2 diopter of hyper-metropia at the time of a preliminary ocular refraction should be informed that, while visually qualified at the time, he has a borderline condition which may progress to a low degree of myopia by the time he takes his physical examination for admission to the Naval Academy, and may therefore be rejected." "Any candidate having from 1/2 to one diopters of hypermetropia at the time of a preliminary ocular refraction should be informed that, while he should pass the physical examination for entrance to the Naval Academy, he stands no better than an even chance of visually obtaining a commission in the line of the Navy on graduation." __________________________ The Gmelin Report Selected items: In the report by Maj McKenney "A Study of Refractive Trends at West Point", he concluded: 1. Pseudo-myopia during periods of stress associated with studying may result in blurred vision in cadets with little hyperopic reserve ** ** [Their refractive status was very close to zero] 2. The average increase in myopia was -1.37 diopters (the range being -1.12 diopters through -1.62 diopters). 3. 39 percent of the graduating class (1956) has less than 20/20 vision at graduation 4. Recommendation that the visual standard remain unchanged -- that hyperopia over +2.0 diopters and myopia over -1.5 diopters should be cause for ENTRANCE disqualification. ** The natural eye changes its refractive status in a negative at a rate of -1/3 diopter per year (where accurate records are maintained) in a four year college. *********************** Note 1: All these men had healthy retinas. All retinas had the capability of resolving 5 minute-of-angle targets at 20 feet. Their natural eye's behaved as expected. The controlled their focal state to the visual environment. For this reason an "undesired" focal state does no indicate an "organic defect" or words to that effect. For that reason I use the term focal state so their is no confusion in your mind about that point. Note 2: The words emmetropia and ametropia were introduced by Donders. Donders took the focal states of the normal eye to be DEFECTS of the eye. Any non-zero focal state of the eye was, by definition, a defect (ametropia). A focal state of EXACTLY zero was defined as "normal". Under this definition, very few, if any, animals or humans have eyes that are normal! _______________________________________________________ The Gmelin Summary: After a century of investigation, it has been established that the cadets at the United States Military Academy become progressively myopic (or less hyperopic) ** during their four years of education. Still to be accomplished however, is an in-depth study of myopia progression and prevention among these USMA Cadets. Dear Friends, Subject: 99 percent go "down" at West Point. MikeT> If you believe one percent survives four years without negative refractive change, then you believe 99% DID experience negative refractive change. MikeT> Is that how you arrived at 99%? Otis> It turns out that your are correct. Otis> Mike -- Actually 100 percent nearsighted got worse. Thus your 99 percent was not accurate -- it was 100 percent. No one "improved" to 20/20. Otis> Here are the figures for those cadets who are nearsightednss at West Point -- who were nearsighted on entry. __________________________________________________ Gmelin: Myopia at West Point: Past and Present Military Medicine, 141 (8) 542 - 3 Aug 76 2. The average increase in myopia was -1.37 diopters (the range being -1.12 diopters through -1.62 diopters (over four years). Otis> Always glad to "correct" your 99 percent got worse to 100 percent for those who were nearsighted at West Point. Best, Otis _______________________ Otis> Are you just playing dumb? I stated that the POPULATION AVERAGE moves "down" at a rate of -1/3 diopter per year. MikeT> Yes, but you also "stated": > Otis> It may be that he believes (a slightly nearsighted person at 20/25) that he will be the one-percent who survives four years with NO FURTHER NEGATIVE REFRACTIVE CHANGE. MikeT> If you believe one percent survives four years without negative refractive change, then you believe 99% DID experience negative refractive change. MikeT> Since it doesn't happen, we must assume you simply spout figures without understanding them. [I don't "spout figures". Here are the published values for those who "cleared" their vision from nearsightedness at West Point. In fact NONE did. OSB] Otis> It is true that even high school students can figure out the implications of that statement. MikeT> Is that how you arrived at 99%? Otis> Actually this West Point study is how I arrived at the percentage of myopes who went "down" at the college. How did YOU calculate the percentage? Best, Otis Engineer ___________________________________ Gmelin> The subject of progressive myopia among the cadets remained dormant at the USMA for ten year. Renewed interest in among the cadets remained dormant and not further investigations were made the subject of myopia was generated by the study of MAJ McKinney MC, on the Cadet Class of 1956. In his unpublished report, "A Study of Refractive Trends at West Point", MAJ McKinney concluded: 1. Pseudo-myopia during periods of stress associated with studying may result in blurred vision in cadets with little "hyperopic reserve". 2. The average increase in myopia was -1.37 diopters (the range being -1.12 diopters through -1.62 diopters (over four years). 3. 39 percent of the graduating cadets of the 1956 had less than 20/20 vision at graduation; and 4. Recommendation that the vision standards remain unchanged -- that hyperopia over +2 diopters and that myopia less than -1.5 diopters be cause for entrance disqualification. Best, Otis