“Every day’s observation shews how far some men may be carried from
the most evident and obvious truths, to support a new hypothesis,
which has no foundation either in nature or reason; but truth will
ever control and prevail over error, though supported with all the
powers of rhetoric and novelty.”—B. MARTIN.
Where distance, or any other cause, prevents our having access to
persons who are competent to suit us properly with spectacles, great
care should be exercised to choose those which cause the print of a
newspaper, or the ordinary types of a book, to appear of their natural
and proper size, while they are viewed at the distance most agreeable
for reading, viz., twelve inches from the eye. It is evidently better
to “try spectacles” on such ordinary printing as they will be generally
exercised upon, than to test them by the very small print with which
persons frequently provide themselves. To decipher this, a greater
power is demanded than is requisite for usual reading, writing, and
needlework, which are the purposes for which we require them, and not
for microscopic observation, nor for distant views.
The eyes in which no malformation or disease exists, but which simply
partake of constitutional decay, or, from too continued application
to sedentary and studious pursuits, are beginning to feel a want of
assistance, should have spectacles of sixty-inch focus, which is an
exceedingly slight magnifying power; and if these are found to be
insufficient to afford an agreeable and natural perception (not an
enlarged or magnified image of the letters of a book, &c., held in
the hand at the distance of twelve or fourteen inches from the eye),
then apply those of the next power, viz., forty-eight inches’ focus.
If these again are unequal to supply the loss of power or incapacity
of the eye to converge the light to a point at the instant it reaches
the retina, then lenses of thirty-six inches focus are to be had
recourse to; and when these fail to afford agreeable vision, thirty,
twenty-eight, twenty-four, twenty, must be progressively adopted, thus
gradually descending the scale until the eyes receive such compensation
for their progressive decay and loss of power, as spectacles carefully
suited to the sight are capable so effectually to supply.
The period at which the sight begins to fail does not at all depend
on age, but varies in different persons according to the formation of
the eyes, the treatment they have received, and the constitutional
capability; therefore, the age of the person requiring spectacles gives
but a vague general idea to the optician as to what is required, unless
other particulars are stated; such as whether glasses have been used
before; the distance at which writing and printing is seen pleasantly
without assistance, the focus of those last used, or sending even but a
broken piece of the same.
“The proper selection of spectacles for imperfect vision is a point
of much deeper importance than is generally believed. An _oculist_
who is only acquainted with the diseases of the human eye, without
possessing any knowledge of it as an optical instrument, is often led
professionally to recommend glasses when they ought not to be used, or
to fix on focal lengths entirely unfit for the purpose to which they
are applied, and the _mere vender_ of spectacles and lenses is still
more frequently in the habit of proffering such counsel.”—BREWSTER.
The near-sighted, or those who require concave spectacles should
use those of the slightest power; No. 0, or No. 1, will generally
be sufficient at first, but this, by the aid of the trial box,
can readily be determined by the wearer himself. There is such an
immense benefit experienced by the short-sighted from spectacles
which suit their sight, that to argue for their adoption of them
would be quite superfluous. Without spectacles they are excluded from
observing beautiful landscapes, recognizing individuals, or viewing to
advantage any of the crowd of interesting objects around them; but by
adopting them they are placed on a par with the long-sighted in such
circumstances, while the sharp and microscopic character of their sight
_without_ spectacles, gives them many advantages over those possessing
ordinary vision.
The short, or near-sighted eyes, have the cornea, and often the
crystalline lens, more convex or arched out than in long-sighted eyes.
This formation causes the rays to converge to a focus before they reach
the retina, but by the application of a concave lens the difficulty is
corrected, and the rays are carried on to their proper point for giving
a perfect representation on the retina.
This character of sight is very frequent, and is more particularly
remarkable among those whose mode of life restricts them to crowded
cities, sedentary employments, and confined situations. Those whose
infantine and youthful years have been passed in the country, or where
the eyes have had a free range of view, not circumscribed by the walls
of the nursery, or limited to the observation of objects near at hand,
rarely require concave spectacles.[4]
The spectacle-frames next demand our attention, as our utmost care in
judiciously selecting lenses of the proper focus for our sight will be
neutralized if the frame or mounting in which they are placed does not
apply comfortably to the head, leaving the lenses they carry fair and
parallel before the eyes. If the front of a pair of spectacles is too
short for the wearer’s face, he will look upon the edge of the lens,
and a portion of the exterior rim of the frame; if they are too long
his eye will meet the opposite edge and inner curve of the rim.
Spectacle-frames are fashioned to suit the variety of formation in
different individuals, and therefore such should be applied as adapt
themselves pleasantly to the temples, across the forehead and before
the eyes. The pupil of the eye should, when looking at an object
directly before it, see through the centre of the spectacle-eye, so
that if the whole of the glass, except the small centre, were painted
black, the rays of light would pass through it without distortion of
the pupil. The bridge or nose-part of the spectacle-frame should be
arched out, made like the crank of a lathe, or perfectly parallel with
the knuckles of the sides, according to the formation of the wearer’s
nose, otherwise the spectacles sit awkwardly on the face too far from
or too near to the eye-lashes, with their centres too high or too low
for the natural exercise of sight. Trifling as these particulars may
seem, they cannot be neglected with impunity. Where these defects
are unattended to, the eye is tortured by straining to overcome the
difficulty, and striving to accommodate itself to them, instead of
their being shaped to meet its requirements. Some old-fashioned
spectacles have short side-pieces, which press most unpleasantly on
one point of the temples, and when closed scratch and rub the lenses.
Others have very cumbrous and heavy sides, with double lift or common
hinge-joints. These also scratch the lenses when folded up, and can
only be worn with any degree of comfort when the head is uncovered.
Decidedly the best constructed spectacle-frames are those which,
without being clumsy, have enough strength to admit of the sides being
extended the full width of the face without bending the front, with
single sides rather longer than their front for ladies’ use, and with
turnpin sides (an extending joint, turning on a pivot,) for gentlemen.
The material of which they are composed should be either gold, silver,
or enamelled blue steel. Tortoiseshell, also, when well made, is very
light and pleasant to wear, particularly for ladies. There is no
advantage in large size, or round-eye spectacles, to compensate for
their clumsy appearance and great weight; we get a sufficient expanse
of observation with the oval-shape glasses without harassing the eye
with an excess of light, which the large glasses admit.
Solid blue steel mountings are a decided improvement, and are
invaluable for persons who constantly require spectacles. They are
wrought from a plate of steel, and shaped as light and uniform as any
other town-made elastic blue-steel spectacles, with the advantage of
being more durable, and eventually less expensive; for as they have no
soldering in their composition, it is scarcely possible to break them,
and therefore they rarely want repairing. Blue steel spectacles, in
consequence of their being so much in request, are coarsely imitated,
and vast numbers are sold by the pretended cheap shops, at apparently
low prices which the wearer will find to be immensely beyond their real
value. There are thirteen different qualities of the spectacles termed
blue steel. The chief part are country made, and roughly put together,
some being all iron, others having iron fronts and steel sides;
others again bear a tolerably close resemblance to the best town-made
articles, and unless the two are compared together, are likely to
deceive a casual observer.[5]
The fine elastic blue steel, of the best quality, are exceedingly
light, highly polished, and beautifully enamelled. They will retain
their appearance for two or three years, when carefully used; and they
can be restored to their original appearance at any time for a few
shillings’ expense.
The anti-pressure spectacles are made of gold, silver, or the elastic
steel. They are not adapted for ladies’ use, but for gentlemen have
been much in demand, as they obviate the necessity of opening and
closing a second joint or lengthening piece, and do not press or annoy
the nose or temples, but by an equal tenacity preserve their proper
position before the eyes.
Single eye-glasses, though very convenient for occasional use, are not
to be compared with spectacles for the agreeable and natural assistance
they give to vision. The eye should not be dependent on them for
continuous assistance. Those who persist in using them should do so as
little as possible; but the wiser course is to discard them entirely,
and adopt the double eye-glasses where it would be tedious to apply
spectacles of the usual kind.
That the vision is more natural and perfect when both eyes are employed
than when one glass only is used, must be self-evident, as the axis of
each glass, placed as they should be in the spectacles, coincides with
the axis of each eye, and the rays of light are thus equally refracted
to the eye. Again, the eyes have a most acute and sensitive sympathy
with each other, and when a single eye-glass is constantly used they
are unnaturally exercised, and prevented from acting in concert. One
eye (generally the right eye) has the glass perpetually applied to
it; and very frequently, in consequence of this pernicious practice,
becomes of a different focus to the other. Mr. George Adams informs us
that he did not recollect an instance of a short-sighted person who had
occasion to increase the focus of his concaves if he began by wearing
spectacles, but that the cases were frequent, where a single eye-glass
had been used, in which the persons had frequently required a change of
glasses.
The prices of spectacles are diversified and fluctuating, like all
other manufactures, so that to publish a list of prices would only tend
to mislead and deceive my readers. For instance, the price of a pair
of pebbles, used formerly to be one guinea extra to the charge for
glasses; they are now reduced to half that sum. A pair of pebbles, of
the concave or of the periscopic figure, were at the same time charged
twenty-five shillings. These have been reduced in the same proportion.
And it cannot be too universally known, that a person can have a pair
of good convex glasses fitted into his spectacles, and correctly suited
to his sight, at from one shilling and sixpence to two shillings
per pair, by any respectable optician. The poorest person may be
defended against the tender mercies of the spectacle speculators; for
he really can obtain a better article for his money, both in quality
and suitableness to his sight, of the respectable optician, and, upon
an average, at _a less cost_ than the cheat contrives, by dint of
manœuvring, to extract from him. Good lenses, in plain frames, or, in
other words, a good pair of spectacles, may be had, correctly suited
to the sight, for two shillings and sixpence. Who then, knowing this,
would suffer his sight to be tampered with? Truly, those who would
stickle for a shilling in the price of such valuable and essential
instruments
“Deserve not the comfort they shed o’er the soul.”
Yet, at the same time, there is no reason why those exorbitant charges
should be submitted to, which are often paid without hesitation by the
delighted purchaser, when a pair of spectacles appears to suit his
sight.
The love of the marvellous, and the insane thirst for novelties, are
strikingly displayed in many inquirers for spectacles. The honest,
straight-forward, and disinterested counsel of the established
tradesman, is looked upon with scowling suspicion; but the
preposterous and shallow pretensions of the empiric, decked with all
the paraphernalia of fudge and falsehood, are listened to with eager
curiosity. If the writer looked to self-interest as his guiding star,
his course would be to preserve silence on these subjects; since it
needs not to be demonstrated, that the practice and the profit of the
regular practitioner are increased by the patched-up and mangled cases,
which are, as it were, provided for him, over and above the number who
_legitimately require_ the exercise of his skill. But he despises such
mercenary calculations, and contends that “The happiness of mankind at
large is a principle that ought to be followed out by all individuals
at every personal cost, and against every kind of opposition.”—_Medical
Examiner._
FOOTNOTES:
[4] In Russia the person having short sight is seated in a chair for
several hours daily, with the head placed in a natural position for
reading, but prevented from pressing forward. The page is at first
placed at the short distance at which the eyes have been accustomed to
observe; but this distance is gradually extended, until the humours of
the eyes, constantly exercised in endeavouring to accommodate their
powers to the gently increased demand upon them, at length acquire the
capability of observing at the usual distance.
It is undoubtedly the fact that this character of sight may be
acquired; many instances could be adduced of watchmakers and others,
whose employments are of a sedentary or studious character, becoming
short-sighted.
[5] It will be perceived that it is the workmanship and nice finish of
the best town-made spectacle-frames which necessarily increases the
price. Thus, a single pound of pig iron, which costs one penny, can be
manufactured into watch-springs of the value of £240.