This study has been an effort to learn more about the nature of myopia. Of primary concern was the development of a method of measuring refractive change in a sample of young adult myopes. This study was designed as a retrospective investigation, not an experiment, and was based on records collected over the past six years (1971-1977). The author was interested in learning the extent to which myopia is a fixed or flexible condition. But before meaningful statements can be made about myopic change, the relevant variables must be isolated. Factors such as age, gender, amount of initial refractive error, or the speed with which the refractive error is changing, are important to explore. If a method of analysis can provide meaningful ways of comparing myopic behavior then further studies can be conducted to test for relationships and for the effects of remedial vision therapy. This chapter describes research questions, subject, method of data collection, and procedures used in data analysis.
RESEARCH QUESTIONS
- What are the most important variables to consider in analyzing changes in refractive error?
- What are the most sensitive methods of measuring refractive change?
- Do the results tend to support Bates and the conclusions of Chapter Two?
- Are future studies of dynamic change in refractive error worthwhile?
- Have baseline data been established which can be used in future studies concerning variables which influence changes in refractive error?
DESCRIPTION OF SUBJECTS
The control subjects were selected from record cards of three optometric offices in Santa Rosa, California. All patients were between the ages of twenty and thirty, were nearsighted and had less than two diopters of astigmatism (see Definition of Terms). Contact lens patients, i.e., any patient who had worn contact lenses at any time, were excluded from the sample because contact lenses often lead to changes in the optical properties of the cornea. Wearers often experience great, unpredictable fluctuations in vision and refraction after switching back to regular spectacles.
All patients from three optometric offices who met the criteria were included in the control population. There were 442 patients from Gottlieb’s office, 211 patients from the records
of Campbell, and 99 patients from Shipley. The distribution of refractive errors for the three control populations was compared with the distribution of refractive errors of the study population from Gottlieb’s office to insure that the study population was not unusual.
A study population was selected from Gottlieb’s records. The patients who met the criteria stated above, and who returned to the office for a second examination, were included in this study population. Normal optometric procedures of the office include the collection of data on each patient. This study was a search through the data which have been collected over the last six years (1971-1977).
The size of the sample was determined by the number of patients who fit the required description and were recorded in the files. There were fifty-two subjects (or 104 eyes) in the sample. The numerical adequacy will be discussed under statistical methods.
The frequency distribution for refractive error is displayed in Figure 10. Data for the control samples is also plotted in the Figure.
The age of the subjects was recorded at the time of the initial refraction. Since the interval between the first and second refraction was as much as 68 months, some of the patients were over thirty at the time of the second examination.
All the patients were caucasian.
There were 28 females and 24 males in the study. Female and male subjects were analyzed separately and in combination.
SPECIAL CHARACTERISTICS OF THE SAMPLE
Sixty-five percent of the subjects in the study sample were medically indigent, and were on Medicaid. The statewide percentage of Medicaid is fifteen percent (Campbell, 1977). This unusually high percentage indicates the uniqueness in the characteristics of patients in the sample.
Most of the patients in this study were exploring “alternative life styles,” i.e., they tended to use marijuana and LSD, had sexually “open” attitudes, worked and lived in low-pressure situations, and tended to be interested in growth-oriented activities such as yoga, meditation, massage, group and individual psychotherapy, “natural foods” etc. The patients had been exposed to ideas and methods of vision improvement (such as Bates) and/or came to the office for advice because they knew of the examiner’s interest in Bates and vision improvement. Generally they came expecting to be counselled on vision improvement.
No data was available to distinguish between patients so involved and patients who were not involved. The number of patients who fell into this category is not known.
RESEARCH INSTRUMENTATION
EQUIPMENT
Refractive information and patient history was recorded on a standard optometric form.
An American optical 590 minus cylinder phoropter was used to aid in determining the prescription. This instrument contains 14,OOO,OOO different combination of lenses.
VARIABLES MEASURED
Date. Date of exam was recorded.
Patient History. Age, gender, and contact lens history were ascertained.
Refractive Error. Data were recorded for each eye separately. The prescription was determined using common techniques of refraction (Borish, 1954). In determining the lens power for any patient, there is a choice of prescriptions available. The optometrist can prescribe the least power lens which allows the patient to-see 20/20 size letters on the distance test chart (see Definition of Terms). A maximum acuity prescription also can be measured by asking the patient which lens power gives the maximum sense, of clearness. The range of lens power from minimum 20/20 to maximum clarity is usually 0.75 diopter (D) (Hirsch, – 1963). This range varies among different patients. The patients who practiced the Bates’ exercises often had a range of 1.50 to 2.00 or more between minimum 20/20 and maximum clarity.
Some vision professionals give the maximum clarity lenses routinely, others give the slightly weaker prescription, i.e.,
0.25 D Less than maximum. This latter procedure is the most common because patients will often experience strain with the strongest prescription (Hirsch, 1963). Some patients demand the strongest and others demand the weakest lens power to give 20120 acuity.
The maximum acuity lens were chosen in all cases in all three offices including both exams of the study sample. This procedure was considered necessary by the examiner since it was not known whether the previous practitioner used the maximum or the slightly reduced prescription for the patient’s lenses. The maximum acuity lens tended to bias the data in the direction of an apparent increase in myopia but this was the only procedure which was guaranteed not to prejudice the results in favor of supporting Bates. Therefore, the examiner assumed it was the proper choice to make.
The actual prescription was modified in some cases where there was an astigmatic component to the myopia. ‘There is a standard formula which converts the astigmatic component into what is known as the equivalent sphere (Borish, 1952). In this modified form the prescription
represents the average amount of myopia present and was much easier to use in comparing eyes and in computing the data.
The following is an example of the procedure for obtaining the average refractive error for each subject. For an eye with 1.00 diopter of myopia combined with 0.50 diopter of myopic astigmatism, the spherical equivalent was determined as follows: one half the astigmatism is considered to be equal to the average spherical refractive error, hence, 0.50/2=0.25 diopters of myopia. This is then added to the existing myopia, 1.00 + 0.25 = 1.25
diopters of myopia (equivalent sphere) for the eye.
REFRACTIVE DRUGS
No ophthalmic drugs were used in the examination. This included cycloplegics which are often used in refraction to expand the pupil and eliminate accommodation. The literature comparing cycloplegic with noneycloplegic data for adults show no difference in refraction (Baldwin, 1964)
SAMPLE TIME
The patients returned from five to sixty-eight months later for a second examination as they felt the need for it. The average interval was twenty-four months. Some returned to obtain a new frame or because they had broken a lens or lost their glasses. Some came because they felt their glasses were too strong, others because they felt too weak. Thus, sample time was determined by the patient. Since that dates of each examination were recorded, the sample time was easily obtainable.
METHODS OF ADMINISTRATION OF TESTING
STANDARD TESTING-PROCEDURES
Eye examinations last approximately one hour. Standard directions and methods of testing were used which are similar to those used by most optometrists and which have been described in detail by Borish (1953). Using the phoropter (see Research Instrumentation), the spherical and astigmatic components of the prescription are determined for each eye separately. Both eyes are then examined simultaneously for proper balance. A routine examination progresses through various steps using objective measures and psychophysical techniques until the prescription is determined.
VARIATIONS IN PROCEDURES
The mechanics of determining the refractive error were equivalent to the standard procedures used by other optometrists. However, Gottlieb’s manner of conducting the examination does differ somewhat from the typical eye examination. This difference is essentially one of style and it is in keeping with the characteristics of the alternate style of life of many of the patients. The atmosphere in the office is casual, relaxed, and non-authoritarian. There is an emphasis upon patient responsibility and the information found in the examination is discussed openly with the patient so that the determination of the final prescription power of lenses is a mutual decision. Because of the orientation towards humanistic health care (i.e., that the whole patient is being examined and not just the eyes and that
the emotional state of the patient is an important factor in the determination of the refractive error). Gottlieb is especially sensitive to the feelings and level of relaxation of the patient. An eye examination requires a close scrutinization of the patient and some patients experience great anxiety during an examination for that reason. The manner and procedure is often altered in order to allow the patient to be comfortable so that a valid measurement could be obtained. Fluctuations of over one diopter on many occasions have been observed as the patient changed moods during an examination. Since the style of examination did not change during the time of the experiment, the internal consistency of the data for each examination (the first and second) was not affected.
VARIABLES NOT CONSIDERED
Data were not recorded to differentiate between those who did or did not practice self-improvement or vision improvement methods. Attempts to gather these data were made and later abandoned because of the wide variety of factors involved. Some patients choose to go without their glasses or to wear them as little as possible. Some wear their glasses all the time. Some prefer to do vision improvement exercises routinely every morning or evening for a set number of minutes; some do exercises only a few days each week; others do little formal exercise but remember to be aware of their breathing and eye relaxation and the association between these processes and improved vision. Many individuals had done little or no work on their eyes, others had read books or had even attended classes with Bates teachers.
Some patients were involved in a variety of psychological, physical, nutritional, spiritual, or other therapies; others took no interest in such procedures. Some patients did not work, others held full-time jobs, and some were students.
Recording data on such a variety of items seemed impossible, and isolating any one factor would have yielded only fragmented, meaningless information of the existing state of knowledge and methods of analysis. It seemed more reasonable to group all patients together, the interested and the disinclined, the four eyed with the near blind, the private-payers and the welfare patients, the meditators, and the yogis.
At the time of the initial examination those who were interested received counseling on vision and health awareness, with an emphasis on breathing. They were also given instructions in regard to Bates’ exercises (see Appendix One for a handout given to most patients). Data on who did or did not participate in this procedure were not recorded in a way useful for this study.
The prescription the patient received was generally less than the maximum which could have been given. This was due to the author’s observation that patients who received weakened prescriptions tended to get better more easily than patients who received stronger lenses.
TREATMENT OF THE DATA
SYNTHETIC PROCEDURES
In order to cover as many aspects of analysis as possible, the treatment method is a hybrid of parametric statistical as well as dynamic analysis (visual curve fitting). Correlation coefficients and tests of significance were computed.
ANALYSIS MODEL
The development of a method of analyzing data for populations of Subjects such as the one in this study is a major interest of the author. Several studies which review methods of data analysis have been presented in Chapter Two. These studies show refractive changes over time. The methods of analyzing the data allow for a visual interpretation of refractive trends. Dynamic changes in refractive error are obtained in the studies which plot the refractive velocity (Bucklers, 1953 and Hofstetter, 1953) and the rate of change of the refractive velocity over time (Slataper, 1950). These methods of analysis are especially valuable for small sample populations which are being used as probes for directing the course of ongoing research. Small changes over relatively snort periods of time are amplified and the dynamics of the changes can be directly inferred from the graphs. The data in the present study will be analyzed according to the methods described.
RELIABILITY
Standard equipment and standard techniques were used in the examination and the tester was educated at an accredited school of optometry and holds a license to practice optometry in the State of California. This, by definition, establishes the reliability of the data.
VALIDITY
Neither the tester nor the patient was concerned with the current study because it was done retrospectively. Since the style of the examination and the instrumentation was the same in the first and second examination, any uniqueness of the data due to unusual attitudes or examination style would tend to be deemphasized. On the basis of these considerations the findings are considered valid.
It must be noted at this point, however, that peculiarities of professional and of patient population characteristics such as those which have been described in this study make it important that the data base established in this study be considered as unique. The data base is designed to be used only in assessing further research with a similar population and in comparing this population with others.