Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Subjective type
Reexamination Certificate
2002-08-30
2004-11-16
Casler, Brian L. (Department: 3737)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Subjective type
C351S239000, C351S246000, C434S178000, C434S179000
Reexamination Certificate
active
06817715
ABSTRACT:
The present invention relates to a method for measuring reading ability and specifically to a method wherein the test subject reads text passages of the same length at a specific distance from the test subject's eyes, the text size of the passages varying preferably stepwise in the order in which the text passages are read and the measurer assessing on the basis of what he hears the reading ability of the test subject.
This invention additionally relates to an auxiliary device intended for use not only in the above-mentioned measuring of reading ability, but also generally in measuring visual acuity, for positioning, and preferably also for maintaining, the test subject's eyes at the desired distance from the object being viewed, such as a text passage or a display screen, such as a so-called eye-test chart or E-chart.
In known methods for measuring reading ability, the test subject reads aloud sentences on paper or a display screen at a predetermined distance, the sentences making sense by their vocabulary, grammatical structure and train of thought.
When known methods for measuring reading ability are applied repeatedly to one and the same person, for example, when testing the effect of eyeglasses of different strengths on the reading ability, the measuring result is distorted, since the test subject may remember the contents of the sentences from a preceding measuring round and may, even the first time, to a varying degree guess correctly some of the words in the sentences.
When reading ability is being measured with a very small letter size, checking the correctness of the reading may be difficult, since it may be difficult for the measurer to see well a text in a very small letter size, and thus, following the test subject's reading may prove to be difficult. It is also difficult to observe when the test subject shifts to the subsequent text passage, written in a different letter size.
In known methods for measuring reading ability, the test subject reads the text aloud for the checking of the correctness of the reading. In this case the maximum speed of reading cannot be detected, since reading aloud slows down the reading.
In known methods for measuring reading ability, as well as visual acuity in general, it is important to know and maintain the distance of the test subject's eyes from the text passage or the so-called E-chart in general used for measuring visual acuity.
In known methods, visual acuity is calculated by dividing the freely selected viewing distance used by a numeric value indicated in meters, the value expressing the size of the letter or optotype viewed in so-called M-units. The size of the letter or optotype is 1 M-unit if the size of its detail at a distance of 1 meter is 1 minute of arc. This, however, requires a calculation, and another drawback is that, when the viewing distance is freely selected, it seldom corresponds to the established numeric values of visual acuity, which constitute a series decreasing from the normal visual acuity of 1.0 in steps having the magnitude of 0.1 log unit.
The object of the present invention is to eliminate the disadvantages mentioned above and to provide a method of the type cited in the preamble for measuring reading ability, wherein memorizing or guessing by the test subject will not distort the measuring results, reading aloud will not slow down the reading, and a text in a very small letter size will not make assessment by the measurer more difficult.
It is a further object of the invention to provide an auxiliary device for setting the viewing distance and preferably for maintaining it at such a distance from the object being viewed, such as a text passage, a letter or an optotype, that at all of the viewing distances that can be selected the calculated numeric values of visual acuity will comply with the above-mentioned established logarithmic numeric series. With the auxiliary device of the invention the viewing distance may additionally be altered rapidly so that at each level of visual acuity the test subject will be able to see a letter size precisely one step smaller if the viewing distance decreases by one step, and respectively a letter size one step larger if the viewing distance increases by one step.
The main characteristics of the invention are given in the enclosed claims.
In the method according to the invention for measuring reading ability there is thus in each text passage at least one written numeral word, which indicates the visual acuity required by the said text passage at the nominal distance of the eye-test chart. Thus a text a small letter size will not hamper the assessing of visual acuity by the measurer.
In the text passages there are, however, preferably many numeral words, each text passage starting with the same numeral word, which is not included in the numbers indicating visual acuity. Thus the measurer is able easily and reliably to note the transfer of the test subject from one text passage to another and to measure the reading time required of the test subject by each text passage.
The measurer is able easily to conclude the visual acuity required by each text passage, since the numeral word or words indicating it follow immediately the numeral word at the beginning of the passage, indicating the changing of the text passage. Any subsequent numeral words, on the other hand, may be random, but it is preferable to select them in order from a numeric series commonly used for indicating visual acuity. Since a person skilled in the art easily memorizes this numeric series, it is easy for him to observe the flawlessness of the reading by the test subject even if the numeric series were not visible to him anywhere.
The letter size, in M units, of successive text passages preferably varies in steps so that the numeric values of the letter size, when necessary as multiples of ten, are the same as in the numeric series used for indicating visual acuity and which is a numeric series decreasing from the normal visual acuity 1.0 in steps of the magnitude of 0.1 log unit.
The test subject is preferably requested to read aloud only the numeral words in the text passages, in which case reading aloud will slow down the reading speed as little as possible, but the test subject will, however, have to read the entire text in order to see where there are numeral words.
The words in the text passages are preferably random words picked out from a large number of normal sentences which make sense, and so the words cannot be guessed and their order cannot be easily remembered, since they do not come in a logical order.
The auxiliary device intended for use in the measuring of reading ability or visual acuity, for positioning the eyes of the test subject and, when necessary, for maintaining them at a specific distance from the object to be viewed, comprises according to the invention a series of parts of different lengths, to be linked to one another in succession, and by selecting from them and, when necessary, linking them together, a length corresponding to each desired distance is obtained and the distances thus need not be measured separately. The desired distances are predetermined in such a manner that at each level of visual acuity the test subject is able to see a letter size precisely one step smaller if the viewing distance decreases by one step, and respectively a letter size one step larger if the viewing distance increases by one step. The calculated numeric values of visual acuity at all the selectable viewing distances additionally follow the above-mentioned established logarithmic numeric series.
The lengths, in meters, of the separate parts linked successively therefore follow the established numeric values of visual acuity, i.e. they form a series decreasing from the normal value (1.0) at intervals of 0.1 log unit, when necessary, in multiples of ten.
The parts of the auxiliary device set are preferably elongated pegs having at one end an axial recess and at the opposite end a likewise axial projection the outer dimensions of which correspond to the inner dime
Lydon James C.
Sanders John R.
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