CHAPTER XI Tue Lens (Part 1)

CHAPTER XI Tue Lens Our attention may be called to the lens by a white spot in the eye, which is quite apt to have been noticed by the patient himself and associated by him with an impairment of his vision, or we may be led to investigate its condition by a history of visual trouble that followed a traumatism; but, unless the changes have produced a whitish opacity which is apparent to anyone, an affection of this organ is not unlikely to escape observation, because the subjective symptoms induced by it are extremely diverse, and, as a rule, not characteristic. For this reason we should make a systematic ex- amination of the lens whenever a patient presents any visual or other anomaly of the eye that is not accounted for otherwise, or has a vague feeling of discomfort, or easily induced weariness. Some of the abnormal conditions met with are congenital, others are acquired. Some demand immediate operative intervention, others are not urgent, but are curable by operation, while still others had better be left alone. The lens may be displaced from its normal position in the patellar fossa, its transparency may be impaired, it may be irregular in form, and it may be swollen or shrunken. DISLOCATION OF THE LENS When the lens is displaced from its normal position it is said to be dislocated. This condition may be congenital, when it is called ectopia, or appear during later life, either spontaneously or as the result of traumatism, when we refer to it as luxation if the lens has been dislocated completely, or as subluxation if a part of it remains in the patellar fossa. Possibly ectopia should be held to include spontaneous dislocations which appear in children after birth, and are dependent on a congenital fault. Luxation and Subluxation If we find the anterior chamber of an eye deeper on one side than on the other and the iris in the deeper portion to be tremulous, 24:7 248 DIAGNOSIS FROM OCULAR SYMPTOMS we know that the iris at this place does not receive its normal support from the lens. We then turn our attention to the pupil, perhaps after dilating it with a mydriatic, and see if we can find it divided by a sharply defined curved line which separates a very dark gray portion within its concavity from a deep black one on its outer side. This line is bright and shining when it is viewed by oblique illumination, black when seen with the ophthalmoscope, and is the edge of the dislocated lens. The refraction is widely different in the two parts of the pupil, highly hypermetropic in the deep black outer portion, because the eye is aphakic at this place, while it is very likely to be myopic and irregularly astigmatic in the other, slightly grayish portion, because this part is occupied by a lens which has been allowed to assume as nearly a spherical form as its age will permit by the rupture of the zonule. This is a subluxation of the lens. The lens has been moved from the center of the fossa patellaris, decentered from the rest of the re- fractive media, and perhaps tilted so that one edge looks forward more or less. If the subluxation is enough to permit the edge of the lens to divide the undilated pupil, the patient probably has monocular diplopia; otherwise his vision is simply blurred, pro- vided that no other trouble is present. In another case we find the anterior chamber evenly deep, the entire iris tremulous, the pupil a deep black, the refraction highly hypermetropic, and then we know that the lens is wholly absent from the fossa patellaris. It may have been removed or extruded from the eye, but if it remains anywhere within the organ it is said to have been luxated. Both subluxation and luxation may be either spontaneous, or the result of traumatism. In the former case we need to look for a disease that would cause a degeneration of the zonule, such as a high degree of myopia, or a choroiditis, but we must remember that after the zonule has been weakened by disease the actual dislocation often is produced by a jolt or jerk of the head caused perhaps by a sneeze, or by a concussion that did not affect the eye directly. This is a point of medicolegal importance, and it is only when such an accident can be ruled out that a dislocation of the lens should be called spontaneous. ; The lens may be luxated backward into the vitreous, where it may do little damage, or may act as a foreign body and set up a destructive inflammation, or it may be luxated forward. If the THE LENS 249 anterior chamber is unevenly deep, while the pupil is large, oval, and immobile, it is practically certain that the lens lies in the aper- ture formed by the pupil with one part, projecting into the anterior chamber, and it is likely that we can see the shining edge of this part by oblique illumination. In another case the anterior chamber is very deep everywhere and we can see by oblique illumination that the aqueous has been largely replaced by something that re- sembles a drop of oil with a bright margin; then we know that the whole lens has been luxated into the anterior chamber. In both of these cases the vision of the eye is much impaired, the patient complains of severe pain that radiates through the side of the head, and a ciliary injection soon appears. These symptoms increase steadily in severity, the tension of the eye rises, and secondary glaucoma rapidly supervenes. Ordinarily the lens loses its trans- parency quickly and then we can see it more easily. By its pres- ence in the anterior chamber it will destroy the eye very soon, and its removal is a matter of urgency. The lens is luxated forward sometimes as the result of a sudden perforation of a corneal ulcer, and can even be extruded from the eye when the opening is large enough, as happens occasionally in ophthalmia neonatorum. It can also be extruded through a rent in the capsule of the eye caused by a contusion. Sometimes, though very seldom, a luxated lens that falls back into the vitreous when the patient lies upon his back may be made to pass through the pupil into the anterior chamber when he shakes his head while he holds it bent forward. Such a lens must be shrunken, and the difficulty of extraction is lessened if we can get it into the anterior chamber and secure it there by contracting the pupil with eserine. A luxated or subluxated lens may remain transparent, but is very apt to become opaque after a short or long interval. It is at all times a source of danger to the eye, yet its extraction is not an operation to be undertaken lightly, for in many cases it is one of the most difficult in ophthalmic surgery to bring to a successful conclusion. Ectopia A traumatic or spontaneous dislocation of the lens rarely is bilateral, and when it is present in both eyes the displacement is very unlikely to be symmetrical, but these conditions are reversed 250 DIAGNOSIS FROM OCULAR SYMPTOMS when we have to deal with what is known as congenital ectopia. | Frequently this is detected during early life in children who belong to families in which it is hereditary, or when it occurs in associa- tion with corectopia, irideremia, or nystagmus, but often it remains unsuspected until the child goes to school and is found to have poor vision. ‘Then he may be thought to be nearsighted and a series of experiences with opticians and optometrists may precede his coming under our observation. The condition may not be apparent at first unless we notice that the lower part of each anterior chamber is deeper than the upper, and that the lower part of the iris is tremulous. The child may seem to be simply amblyopic, but when we dilate the pupils for the purpose of retinoscopy our attention is attracted by a dark curved line in the lower part of each, and we find the lenses subluxated, usually symmetrically up- ward, perhaps with an inclination outward or inward from the median line of the eye. We are likely to recognize the condition more quickly if the patient has corectopia, which usually is upward with the lenses, irideremia, or coloboma of the iris, or if he com- plains of polyopia. In the last case we shall probably find the edge of the lens to be visible in the undilated pupil. It is only in rare cases that the lenses are displaced downward, inward, or outward, and still more rarely is the displacement asymmetrical. The lenses seldom if ever are tilted. Ectopia is hereditary, and the particular type seems to be trans- mitted from one generation to another, but we occasionally meet with sporadic cases. The prognosis is uncertain. The lenses may remain clear and not change position for many years, perhaps not for life, but they are luxated more readily and by slighter traumatisms than those which occupy their normal positions. Many of them exhibit a tendency to move upward slowly, to shrink, and to become cata- ractous. Sometimes it is difficult to say that an ectopia of the lens was actually congenital, for a perfectly typical case may develop during childhood. In an irideremic girl five years old I found the lenses clear and in normal position, the eyes rather amblyopic, but no refractive error except a simple myopic astigmatism. Three years later there was considerable myopia, the lenses were slightly ectopic upward and exhibited strie of opacity, a condition that differed in no way from a congenital ectopia with commencing cataracts. THE LENS 251 COLOBOMA OF THE LENS A. coloboma is a notch or concavity in the lower margin of the lens, rarely elsewhere, and in about half of the cases in which it is found it is associated with a coloboma of the iris, of the choroid, or of both. A very large one may give rise to irregular astig- matism, but a small one causes no visual trouble and is discovered accidentally, as a rule. Sometimes a narrow strip seems to have been cut away in so wide a sweep that the lower margin appears in the pupil, when it is dilated, as a nearly horizontal line, and this may readily suggest ectopia, or subluxation upward. The differentiation can be made usually from the absence of visual trouble, from the lack of a history or of any symptoms pointing to traumatism, from the lack of a disease likely to affect the zonule, and from its presence in one eye only. The cause of such a flatten- ing of the margin of the lens is problematical, though various theories have been propounded. LENTICONUS Occasionally a child is brought to be fitted with glasses because of nearsightedness, and we find that while the refraction near the center of the pupil is highly myopic, that in the periphery is much less so, perhaps emmetropic, or hypermetropic. An adult may inform us that he has become nearsighted recently, and show a similar condition of his refraction; if he is quite elderly he may be jubilant over his “second sight,” as he is able to read without glasses again, and he may not be aware that he cannot see well at a distance, for old people often are oblivious to such a fact. We first examine the cornea in each case to exclude keratoconus, and if its curvature is normal we know that the fault is in the lens. In the child we are likely to find that either the posterior or the anterior surface of the lens projects in the form of a cone, less often in that of a sphere, a congenital fault of development which is not apt to change and is called posterior or anterior lenticonus. The posterior is by far the more common, and usually is associated with an opacity at the posterior pole, sometimes with opacities elsewhere in the lens. In the adult it is more likely that a change has taken place which has produced an abnormal difference between 252 DIAGNOSIS FROM OCULAR SYMPTOMS the indices of the cortex and of the nucleus, a condition called false lenticonus as the form of the lens is not changed. In the majority of cases false lenticonus is a forerunner of cataract, but occasionally an old man retains his second sight for a long time. The differentiation between these forms of lenticonus can be made by means of Purkinje’s images. If the posterior one is very small at a certain place and becomes elongated when the light is moved a little to one side, the condition is one of posterior lenticonus. If the anterior image behaves in the same way the condition is one of anterior lenticonus, and we may be able to make out the conical shape of the anterior surface of the lens by oblique illumina- tion. If both images are of their normal sizes but the posterior one is unusually bright, we know that the patient has a false lenticonus. CATARACT Any opacity of the crystalline lens, of its capsule, or of both, is known as a cataract. Such an opacity may appear at any time during life from before birth to extreme old age, may be caused by traumatism, may be symptomatic of disease, or may develop spontaneously as the result of processes with which we are at best imperfectly acquainted. The consistency of the lens varies with the age of the patient; it is soft in childhood and develops in early manhood a small hard nucleus which increases in size until it renders the lens almost wholly hard in old age; so a cataract may be accordingly soft, without or with a hard nucleus, or hard. Sometimes a cataractous lens degenerates and its fibers become liquefied, while lime salts may be deposited in it or its capsule, so as to form a fluid, or a calcareous cataract, and occasionally the fluid becomes absorbed until little is left of the lens except its capsules, which form a sort of membrane. The color in the great majority of cases is white or gray, when the lens is visible as a white spot in the pupil posterior to the plane of the iris, but exceptionally it is amber or brown, as in black cataract. The opacity may occupy the whole lens, or only a portion of it, and in the latter case may have many situations, as is seen in the different varieties of congenital cataract. When it is secondary to, or is complicated by, an intraocular inflammation, the cataract is said to be complicated, otherwise it is simple. A cataract that develops in an elderly person from an unknown cause is called senile, THE LENS 253 and may be observed in its incipient, immature, mature, or hyper* mature stages, according to the period of its development. Congenital Cataract We are unable to differentiate a cataract that was present at birth from one that developed during the first few years of life, unless informed by the history, so we are accustomed to call all which appear during childhood congenital when they cannot be ex- plained as the results of traumatism, or of disease. The patient is a child, as a rule, but sometimes is an adult who states that he has had the trouble ever since he can remember. Ordinarily the diagnosis is not difficult, whatever may be the age of the patient. Congenital cataract affects both eyes almost invariably, and most of its forms are so characteristic that they are recognized as such at once when they are bilateral, unless there is evidence that they were produced by a known cause. A cataract in one eye alone is so very likely to have been acquired that it can be called con- genital only when it is positively known to have been present at or shortly after birth, to have not changed for a long time, and that the eye has not suffered from traumatism or disease. Zonular or Lamellar Cataract The most common form of congenital cataract is the zonular or lamellar. We see by oblique illumination a round gray opacity, the center of which appears to be less dense than the rest, sur- rounded by a transparent zone, behind the plane of the pupil in both eyes. After we have dilated the pupils with a mydriatic we see with the ophthalmoscope that this opacity forms a disk lying in transparent lens tissue, that its center really is less opaque than its margin, and that little dentations extend out from the latter into the clear tissue. If we use a high magnifying power we can see that the opacity consists of mnumerable minute points and larger grayish clouds, while part of the dentations seem to ride on the margin, having two legs, one coming from the anterior, the other from the posterior layer. Some of these riders are separated from the opacity and lie in the clear tissue, where they indicate the commencement of a new layer. Occasionally one or two opaque ‘zones may be seen about the principal opacity. The size of the opacity varies; it may be so small as to impair 254 DIAGNOSIS FROM OCULAR SYMPTOMS the vision only a little, and a very few have been reported as rudimentary, but, as a rule, it is large enough to nearly or quite fill the pupil. It is developed uniformly in both eyes almost always, and the only cases in which a‘ question arises as to its congenital origin are the rare ones in which the cataracts are unequal, or are not present in both eyes; then we have to make a careful inquiry to ascertain whether the eye has