Curiosities of Medical Experience

by J. G. Millingen

Ramazzini informs us that this affection is commonly observed among the Italian peasants, amongst whom he was not able to trace any other peculiarity than an enlargement of the pupil. This state of the vision, however, has been attributed to the peculiar brightness of the Italian sky, its clear atmosphere, and the relaxing warmth of the temperature. The Italian peasants are therefore constantly exposed to all those causes that tend to debilitate the iris, while they irritate the retina. We thus find these causes acting with renewed power at the season when the disease usually makes its attack,—the vernal equinox, when an increased flood of solar rays breaks on them. Such is the dimness that this brightness produces, that the peasantry frequently lose their way in the fields in the glare of day; but on the approach of night they can see distinctly. Hence are they obliged to remain for some weeks in the shade to recover their sight.

A deficiency of the black pigment of the eye is occasionally found in persons of a very fair complexion and light hair. This affection is therefore common in the Albinoes. This circumstance arises from the whiteness of the eyelashes and hair, whereby the retina is deprived of the natural shade that softens the light in its descent. This debilitated race generally inhabit warm and damp regions; they are seldom long-lived, and frequently low-spirited and morose. The iris is of a pink colour, and this circumstance, added to the constant winking that the weakness of the organ occasions, gives them a distressing appearance. In horses, this want of the dark pigment constitutes what is called the wall eye.

Acuteness in night vision is natural to most, if not to all, animals that prowl in the dark. In the feline genus we observe that the iris can be contracted much closer than in mankind, when exposed to a vivid glare; but they also expand to a much greater degree when obscurity sets in. Owls, bats, and many insects, possess a similar faculty.

Day sight, the nyctalopia of some authors, is said to be endemic in some countries,—Poland, the West Indies, Brazil, and various intertropical regions. This affection arises from causes totally different from the former one. Here the eye is habitually exposed to too great a flood of light, whence the retina becomes torpid. It has been said to be endemic in some districts of France, particularly in the neighbourhood of Roche Guyon, on the banks of the Seine; but here the soil is of a dazzling white: and as it makes its attacks in the spring, and continues for three months, it is supposed to arise from the keenness of the reflected light, after the dreary winter months.

This disease has also been commonly observed in Russia, especially in the summer, when the eye is exposed, with scarcely any intermission, to the constant action of light, as the sun dips but little below the horizon, and there is scarcely any interval of darkness. Hens are subject to this affection, and cannot see to pick up their food in the dusk of the evening. The complaint is, from this circumstance, called hen blindness.

Dr. Heberden has communicated the following curious case of this species of affection: “A man about forty years old had in the spring a tertian fever, for which he took too small a quantity of bark, so that the returns of it were weakened without being removed. Three days after his last fit, being then employed on board a ship in the river, he observed at sun-setting that all objects began to look blue, which blueness gradually thickened into a cloud; and not long after he became so blind as hardly to perceive the light of a candle. The next morning about sunrising his sight was restored as perfectly as ever. When the next night came on, he lost his sight again in the same manner, and this continued for twelve days and nights. He then came ashore, where the disorder of his eyes gradually abated, and in three days was entirely gone. A month after he went on board another ship, and after three days’ stay in it the night blindness returned as before, and lasted all the time of his remaining in the ship, which was nine nights. He then left the ship, and his blindness did not return while he was upon land. Some little time afterwards he went into another ship, in which he continued for ten days, during which time the blindness returned only two nights, and never afterwards.” It appears, however, that this individual had previously laboured under an affection produced by the use of lead, which had left him in a state of much nervous debility. Notwithstanding this circumstance, this case clearly proves that the affection is liable to be increased and brought on by local influence.

Long sight. In this species of vision the iris is habitually dilated, and not easily stimulated into contraction. Several varieties of this affection have been observed. Dr. Wells, in the Philosophical Transactions, relates the case of a young person who, from a permanent dilatation of the pupil, saw near objects with much difficulty and confusion, but remote bodies with singular accuracy. The power of moving the upper lid was completely lost. This dilatation of the pupil, which may be artificially produced by the application of belladonna, can be remedied by the use of convex glasses.

Short sight. In this case the iris is contracted, and the cornea, which in long sight is too much flattened, is too convex or polarised; therefore spectacles of an opposite character, and with concave glasses, become necessary. Mice are said to be short-sighted; hence the affection has been termed myopia or myopiasis, literally “mouse-sight.”

Skew sight, or sight askew, is a condition of our vision only accurate when the object is placed obliquely, in consequence of some partial obfuscation of the cornea, frequently from slight scars, scarcely, if at all, observable. In this lateral vision the axis of the eye affected usually coincides with that of the sound eye. In squinting, on the contrary, the two axes do not coincide.

In false sight, imaginary objects float before the sight; or, at other times, objects assume imaginary forms and qualities. The latter species has been divided in cases where the objects that are supposed to be seen have no real existence, and in cases where actual objects have assumed qualities that do not appertain to them. The first are termed ocular phantasms or spectres; the latter, ocular transmutations or illusions. These spectres sometimes form dark spots, called by physicians muscæ volitantes. In another species, a net-work seems to be spread before the eyes; hence called visus reticularis. In a third form sparks scintillate, and this appearance is experienced when the eye has been struck. The eye is also troubled with an imaginary sense of dazzling, constituting the myrmaryge of the Greek writers; at other times, an iridescent appearance, exhibiting the colours of the rainbow, is experienced, although sometimes this impression is confined to a single colour. Dr. Heberden relates the case of a lady of advanced age, lodging on the eastern coast of Kent, in a house that looked immediately upon the sea, and exposed to the glare of the morning sun. The curtains of her room were white, a circumstance which added to the intensity of the light. When she had been there about ten days, she observed one evening, at the time of sunset, that first the fringes of the clouds appeared red, and soon after the same colour was diffused over all the objects around her, especially if they were white. This lasted the whole night, but in the morning her sight was again perfect. This alternation of morbid and sound sight prevailed the whole time the lady resided on the coast, which was three weeks; and for nearly as long after she left it, at which time it ceased suddenly of its own accord.