Papers by (a) Dr. Francis Young and (b) Dr. Peter Greene
You can read selected papers by Dr. Young, under, “RESEARCH”, on this site.
(a) Dr. Young did a life-time of work in prevention.
His work is critical in understanding why plus-prevention would be wise — for the person with a mild prescription and a strong desire to succeed. Prevention (with recovery) is possible for that person. But early prevention is never easy or fast.
- Dr. Francis Young’s published papers:
Here is list of the his numerous papers on prevention for your interest.
New Reference Site:
The critical paper is, “Bifocal Control of Myopia”. This paper showed that prevention is possible with a intelligently worn plus lens.
New Reference Site:
This shows the wisdom, of “early prevention”. But it also suggests that the person must go though an educational process (when at 20/40), to correctly wear a plus for all close work. If the person does not understand the need and wisdom of wearing a plus – he simply will not do it.
It takes a strong, wise, and motivated person to truly START with the plus at 20/40.
2. Why the pilot must understand plus-wear instructions.
Remarks about a pure-plus study (while all persons have 20/50 to 20/40). We might guess that the fundamental eye (having refractive states, not failures) is dynamic.
Has a plus-prevention study ever been attempted – and exactly what were the results?
How can you get a 10 year-old child to EVER wear a plus lens – so you could even ATTEMPT to conduct a “prevention only” study?
I will use the term “Refractive State”, which means the individual is personally responsible for the measurement.
This is to avoid the some of the medical bias that almost always over-prescribes a minus lens.
You simply can not “prescribe prevention — because the child can not be instructed to wear the preventive plus correctly. For a mature pilot – who understand WHY it is necessary – you can expect that he will wear the plus consistently. At 20/40 (self-measured -1 diopter) he could probably get to 20/20 in about one year. That is how difficult prevention is.
Dr. Young’s existing study that shows, by “existing practice” how to get as close to that ideal as possible.
For me, the OD does not have “the time” to help me, with the required explanation. (The minus is so easy – and prevention requires so much from the individual – as to make prevention impossible in the context of optometry.)
I accept that ONLY prevention is possible. Intense use of the plus – is out-of-scope for any medical person sitting in an office – prescribing a strong minus – for all who enter.
Details of “Bifocal Control of Myopia”
Author: Dr. Francis Young, Dr. Kenneth H. Oakley
In the 1975 Issue of the, “American Journal of Optometry and Physiological Optics”
Let me clarify. What we need to know, in a plus-group versus minus-group, what the effect was over a five year period – on the totally natural eye. (A natural eye can and does have negative and positive refractive states. With a positive state, you have 20/20 or better – if you measure it yourself.)
Since a child can not be trusted to wear “just the plus” alone, a “bifocal” was prescribed. This is not a plus-prevention study as such, but with some intelligence and wisdom on the part of the person himself – it would be perceived that prevention would be possible at 20/40 and -1.0 diopters.
Here was the protocol for children:
Young> … the parents were offered a discussion about the fitting of a “reading lens” or bifocal which would provide 3/4 to 1 diopter (D), of plus lens magnification over the minus distance prescription which was usually under-corrected by 0.5 diopter.
Young> For example if the children’s refraction indicated -1.0 diopter, the prescription would be written for a -.5 diopter with a plus 1.5 diopter add.
Otis> What this study FAILED to do – was to EXPLAIN the need and wisdom of wearing the plus “correctly”. The child, not understanding WHY he should wear a plus – simply ignores looking though it. Even with that difficult limitation, this study showed that, with motivation, long-term prevention is possible.
Otis> If you give a young man a plus – but do not tell him WHAT he is doing or WHY he is doing it, you will find that, when he puts the plus on (say a +2 for reading), and then he will LEAN FORWARD to about 13 inches. When he does this – he totally CANCELS OUT THE INTENDED, AND DESIRED EFFECT OF THE PLUS.
Otis> This would ruin the study – as a practical manner. But still, even NOT TELLING the child to “push print” (the study DID have a highly significant effect.)
This does not mean “cure”. It does not mean you can ever “prescribe it”. Further, I limit myself to those who understand these difficulties.
But this study did proven that a plus (used before you go below 20/40, and -1.0 diopters) could have a MILD “recovery effect”.
That is the reason why, for a study with intelligent, motivated pilots, you could get recovery from 20/40. But you would have to TRUST both the intelligence and motivation of each person in the study.
NOT ONE STUDY ever extended that type of trust to the person himself.
Until THAT is done, all intentional plus-prevention studies will fail.
Tragically, no OD wants to give you that type of authority and competence to work on prevention (with you in control) because if you succeed, the entire “science” that he thinks SUPPORTS a prescription – will be proven wrong.
3. An educated person – must make his own measurements.
Subject: If you wish for a person to believe in his own results – then insist he make the critical refractive measurements himself.
Personally, I measure my refractive state myself. (See my videos on how to do it.)
It just takes some training, logic, and persistence. Obviously a young child can not do this – so no preventive study could be conducted with children.
But a mature person, at 20/40 and -1.0 diopter, could participate in a preventive study, by personally understanding the facts concerning the proven behavior of the natural eye.
My measurement accuracy, is to 0.25 diopters. For a person with this type of training, you can trust the person’s accuracy – after he makes a consistent series of measurements.
A serious study of prevention would require that the person be deeply involved in this type of science. This is not medicine, nor a “medical study”, as such.
It would be conducted by the wisdom and fortitude of each engineer in the study. That is the reason why each person must understand the nature and statistics developed by Dr. Young’s study of the dynamic behavior of the fundamental eye
4. The need for the pilot to understand statistics of his own study.
I always acknowledge this: Statistics can never solve a problem. Only the human mind can solve the problem of the natural eye with self-measured negative status – of about -1.0 diopters.
Statistics can do this for all of you – if you understand them, and measure your refractive state yourself (as a group of scientists).
Statistics can prove, early success, in the the group that is totally committed to wearing the plus – can get out of it (change their status from -1.0 diopters to +0.5 diopters.)
The implication of Francis Young’s study – is exactly that way. The value of his study was the establishment of the REASONABLE standard-deviation (Sigma) for a large group of people.
If the person is to be the, “intellectual leader” in his own study (either test or control group) for nine months then, BOTH GROUPS WILL SUCCEED.
But each man must fully understand the conditions and difficulties of Dr. Young’s seminal study of the eye.
NO STUDY HAS EVER BEEN ATTEMPTED – WITH EDUCATED PEOPLE WHO WILL MAKE THE REQUIRED MEASUREMENTS.
In Dr. Young’s relied ONLY CHILDREN with NO INSTRUCTSIONS on how to use, or correctly-wear the plus lens. That is truly understandable, if you deal with a child in an “office”. The result can never be truly effective if the child “leans forward” by several inches, effectively cancelling the desired effect of the plus lens.
We must get ourselves out of the “confines” of that office. I would ask the that the people in that “office”, acknowledge these problems. Extend a friendly and helpful hand to all of us in this effort. Even though it can drastically change the man’s practice, “in his office”. This is for the betterment of ALL OF US.
If the person develops growing, educated wisdom, and is prepared to examine a study that shows (statistically) that the plus had a strong effect on the refractive state of the natural eye (p < 10E-6) for all groups – I would believe that a person fully “invested” in his own study, would show the required change in refractive state from -1.0 diopters to +0.5 diopters in about eight months.
Today, that type of scientific, informed study, is effectively blocked by the “powers that be”. I can not change that fact. I wish I could.
5. A proposed study – with pilots.
A Aeronautical College would be ideal for a prevention study.
In the final analysis, the pilot must have the insight and, above all else – the motivation to wear the plus to go from self-measured 20/40 to 20/20. Dr. Young’s study shows that it is indeed possible to do it.
6. For additional details, please read, “STUDY”.
(b) Papers and Abstracts by Peter Greene and Antonio Medina
1 REVIEW: PREVALENCE & INCIDENCE of MYOPIA
Peter R. Greene, Ph.D., Edward S. Vigneau, B.S., Judith Greene, M.P.H.
Purpose. Herein we relate prevalence-time data, incidence rate data, age of onset, system plateau level, and system time constant, using exponential equations, as they apply to progressive myopia, potentially useful over a wide age range.
Methods. Cross-sectional refraction data is analyzed, N=9 studies, total number of subjects N = (345, 981, 7.6K, 39, 421K, 383, 2K, 12K, 255) = 444.6K , age range 5 to 39 years. Basic exponential equations allow calculation of the prevalence vs. time function Pr(t) [%] and the incidence rate function In(t) [%/yr] , system time constant t0 [yrs.], onset age t1 [yrs.], and saturation plateau level <S> [%] .
Results. The myopia prevalence as a function of time Pr(t) [yrs] and myopia incidence as a function of time In(t) [%/yr] are continuously generated and compared with prevalence/incidence data from various reports investigating student populations. For a general medical condition, typical values for time constant t0 may range from one week to 5 years, depending on the health condition. Typical plateau levels may range from 35% to 95% . Data from recent demographic studies of myopia, N=9, are calculated for prevalence Pr(t) with accuracy +/-14% , and incidence In(t) within +/-2.6 %/yr., onset t1 = 1.5 yr., time constant t0 = 4.5 yr. By comparison, linear regression can predict myopia prevalence Pr(t) within +/- 11% , and estimates a constant myopia incidence rate In(t) = 4.7 % per year , [ 95% CI: 2.1 to 7.3 % /yr.].
Conclusions. The initial incidence rate at onset age In(t1) and system time constant t0 are inversely related. For myopia, onset age, time constant, and saturation plateau level are fundamental system parameters derived from age specific prevalence and incidence data.
2. Progressive Myopia and Lid Suture Myopia are Explained by the Same Feedback Process: a Mathematical Model of Myopia
Antonio Medina and Peter R. Greene
OBJECTIVE: Progressive myopia in humans and lid-sutured myopia in primates have been considered to be different processes. This report seeks to establish the connection between progressive myopia in humans and lid suture myopia in macaque monkeys.
METHODS: We followed the axial length of 4 lid-sutured macaque monkeys over an 18 month period. Their axial length is directly related to myopia. We also studied the myopia progression in corrected human subjects. Macaques and humans exhibit a linear time course of myopia progression when lid-sutured or corrected with lenses, respectively.
RESULTS: A linear progression is observed in lid-sutured eyes of four macaques, r = 0.94, p < 0.05. Human progressive myopia and lid-suture myopia can be modeled by the same feedback process. In both cases the functional equivalent is the opening of the feedback loop.
CONCLUSIONS: The open loop feedback process predicts a linear progression of myopia. This prediction was confirmed in human subjects and it is now confirmed in our macaque subjects. This process also explains the very rapid rate of myopia progression of lid sutured eyes.
3. Review: Exploring Reading Glasses to Stabilize College Myopia.
Peter R. Greene, Ph.D., Antonio Medina, O.D., Ph.D.
Reference: Proposed Preventive Study at the U. S. Naval Academy
College students often become -1.0 to -2.0 diopters more myopic, so reading glasses were explored, using theory and experiment, to partially cancel the effects of the study environment. Three computer models are developed to predict refraction R (t) versus time. N = 25 different sets of (+) Add lenses are evaluated, for required adjustment period and reading comfort, and endurance. Basic control system equations predict exponential myopia shift of refractive state R (t) with time constant to = 60 – 100 days, as observed experimentally. Linear, exponential and Gompertz computer results are compared calculating refraction R (t) during the college years, showing correlation coefficients |r| = 0.96 to 0.97, accurate within +/- 0.31 D. over a 14 year interval. The experimental design phase of a pilot study at Annapolis is described, using reading glasses, +1.5 D. to +3.0 D. to alleviate college myopia. Typical college myopia rate is – 0.3 to -0.4 D/yr. Reading glasses may be a simple, practical solution to stabilize college myopia.
4. Emmetropia Approach Dynamics with Diurnal Dual-Phase Cycling
PETER R. GREENE, OTIS S. BROWN, ANTONIO P. MEDINA, HARRY B. GRAUPNER
Numerical experiments are performed on a first order exponential response function subjected to a diurnal square wave visual environment with variable duty cycle. The model is directly applicable to exponential drift of focal status. A two-state square wave is employed as the forcing function with high B for time Hand low A for time L. Duty cycles of (1/3), (1/2) and (2/3) are calculated in detail. Results show the following standard linear system response: (1) Unless the system runs into the stops, the steady state equilibrium settling level is always between A and B. The level is linearly proportional to a time-weighted average of the high and low states. (2) The effective time constant t(eff) varies hyperbolically with duty cycle. For DC = (1/3) and t = 100 days, the effective time constant is lengthened to 300 days. An asymptote is encountered under certain circumstances where t(eff) approaches infinity. (3) Effective time constants and steady state equilibria are independent of square wave frequency f, animal time constant t1, magnitude and sign of A & B, and diurnal sequencing of the highs and lows. By presenting results on dimensionless coordinates, we can predict the drift rates of some animal experiments. Agreement between theory and experiment has a correlation coefficient r = 0.97 for 12 Macaca nemestrinaeyes.