Aphakia of the eye

Aphakia is the absence of a lens. An eye without a lens is called aphakic. Congenital aphakia is rare.

Usually the lens is removed surgically due to its clouding or dislocation. There are known cases of lens loss due to penetrating wounds.

A pathological condition of the visual apparatus, in which the eye lacks a lens, is aphakia. Let's consider its features, causes, symptoms and treatment.

According to the International Classification of Diseases, Tenth Revision ICD-10, aphakia belongs to two categories simultaneously:

1. Acquired form

VII Diseases of the eye and adnexa (H00-H59).

• H25-H28 Diseases of the lens.

2. Congenital form

XVII Congenital anomalies (malformations), deformations and chromosomal disorders (Q00-Q99).

Q10-Q18 Congenital malformations of the eye, ear, face and neck.

• Q12 Congenital anomalies (developmental defects) of the lens.
  • Q12.3 Congenital aphakia.

The absence of a lens in the eyeball is an ophthalmological disease that very often occurs with a deepening of the anterior chamber of the eye. Against this background, a pathological bulge is formed - a hernia. Aphakia is characterized by trembling of the iris, that is, iridodonesis. This symptom also manifests itself when part of the lens is preserved. The trembling of the membrane is aimed at restraining the jolts of the vitreous body when moving the eye.

The disease can be either acquired or congenital. It can develop after surgery, in which the eye was injured. The aphakic eye is characterized by a violation of the refractive power of the visual structure. There is also a significant decrease in visual acuity and a lack of accommodation.

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Epidemiology

Medical statistics indicate that about 200 thousand people are diagnosed with aphakia every year. This pathology is not fatal, so there are no cases of fatal outcome.

The disease is diagnosed 27% more often in men than in women. The risk group includes elderly patients, people whose work is associated with the risk of eye injuries. The congenital form is associated with abnormal pregnancy and infectious diseases suffered by the expectant mother during pregnancy.

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Causes aphakia

The main causes of aphakia are related to trauma to the visual apparatus. Penetrating wounds and injuries can lead to the loss of the lens and the development of blindness. In medicine, cases of congenital defects have been recorded when a child is born with this pathology.

Based on this, the causes of the disease can be congenital and acquired. In ophthalmology, the following types of congenital pathology are distinguished:

• Primary – caused by lens aplasia.
• Secondary – develops during the period of intrauterine lens resorption.

Depending on the prevalence, the disorder can be monocular (one-sided) or binocular (bilateral).

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Risk factors

Risk factors for aphakia directly depend on the form of the disease: congenital and acquired. The latter is most often associated with the following factors:

• Spontaneous loss of the lens as a result of injury to the eyeball.
• Dislocation of the lens, requiring its removal or surgical treatment of cataracts.

Congenital pathology is associated with developmental disorders of the fetus during the intrauterine formation of all organs and systems.

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Pathogenesis

The mechanism of origin and development of aphakia depends on its causes. The pathogenesis of the primary congenital form is based on a disorder in the PAX6 and BMP4 genes. Due to the delay in the development of the structure of the eyeball at the stage of corneal-lens contact, pathology develops.

The secondary form of the disease is associated with idiopathic absorption of the lens. Its pathogenesis is based on mutation and disruption of the formation of the basement membrane from which the lens capsule develops.

As for the pathogenesis of acquired ophthalmological pathology, the main attention is paid to dislocation and subluxation of the lens, surgical extraction of cataracts, penetrating wounds or contusion of the eyeball.

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Symptoms aphakia

Ophthalmologic pathology has its own characteristic signs. Symptoms of aphakia are manifested by impaired binocular vision and lack of accommodation. Against the background of iris trembling due to the absence of the lens, visual acuity decreases.

Patients complain of fog before their eyes, poor ability to fix double vision, headaches, weakness, irritability, and general deterioration of health often occur.

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First signs

Visual impairment has different causes of origin. The first signs of the disease largely depend on the factors that caused it. Let's consider the main clinical manifestations of the pathology:

• Deepening of the anterior chamber of the eyeball.
• Remnants of the lens in the iris area.
• Trembling of the iris when moving the eyes.
• Formation of a hernia.

The above symptoms are a reason to immediately consult a doctor. Without timely medical care, the disease can lead to complete loss of vision.

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Stages

Aphakia has certain stages, which are determined by the degree of damage to the lens and the impairment of visual acuity.

Let's consider the main stages of ophthalmological disease and their characteristics:

Degree of violation	Characteristics of violations	Disability group
I	Monocular aphakia. Mild impairment. Visual acuity decrease within 0.4-1.0 diopters with the possibility of correction in the better seeing eye.	VKK limitation
II	Monocular or binocular aphakia. Significant reduction in visual acuity in the better seeing eye, but with the possibility of correction. In the monocular form of the disease, pathological narrowing of the field and visual acuity is possible, which is not subject to correction.	Group III
III	The absence of a lens in the eyeball occurs with other diseases that affect the healthy eye. Visual acuity is within 0.04 - 0.08 with the possibility of correction in the better seeing eye.	II group
IV	Monocular and binocular forms of pathology with severe changes in various ophthalmological structures. Pathological decrease in visual acuity.	Group I

Depending on the stage of the disease and the degree of impairment, treatment methods, i.e. vision correction, are selected.

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Forms

The absence of a lens in the eyeball is a pathological condition that leads to radical changes in refraction and a decrease in visual acuity. The types of the disease depend on whether both eyes or one are affected.

Aphakia is divided into two types:

• Unilateral (monocular) – diagnosed most often, characterized by the absence of a lens in only one eye. May be accompanied by aniseikonia. That is, seeing objects of different sizes, both with the diseased and healthy eye. This significantly complicates the quality of life.
• Bilateral (binocular) – most often occurs as a result of a severe form of cataract, which has caused deformation of the lenses of both eyes. Characterized by a violation of the refractive power of the visual structure. There is no accommodation, that is, clear vision of objects at different distances, visual acuity decreases.

As the disease progresses, it can develop various complications. Complete loss of vision in one or both eyes is possible.

Monocular aphakia

Unilateral or monocular aphakia is characterized by the presence of a healthy lens in only one eye. All moving objects and items that fall into the field of vision can be perceived by only one eye. Monocular vision provides information about the shape and size of the image. While binocular vision is characterized by the perception of an image in space, that is, the ability to record at what distance from the eyes the object is located, its volume and a number of other characteristics.

There are two types of monocular aphakia. In the first case, visual information is fully perceived by one eye. In the second case, monocular alternating vision is observed, i.e. aniseikonia. The patient sees alternately with one eye and then the other.

In addition to aphakia, there are other pathologies with a monocular type of vision:

• Monocular diplopia – due to the deviation of the visual axis, objects in the visual field appear double. Double vision occurs with partial clouding or displacement (subluxation) of the lens. This occurs with congenital pathologies or eye injuries.
• Monocular strabismus is an abnormal violation of the parallelism of one of the visual axes. Only one eye squints, its visual acuity drops sharply. The brain is rebuilt to receive information only from the healthy eye. Because of this, the visual functions of the diseased eye are reduced even more. In some cases, alternating strabismus is diagnosed, when a person alternately sees with one eye and then the other.
• Monocular blindness – this pathology is characterized by temporary attacks of blindness. It occurs due to many diseases. Most often, these are vascular and non-vascular lesions of the retina, optic nerve or brain diseases.

Diagnosis of monocular aphakia is not difficult. Various methods and devices are used for this. Regardless of the cause, the pathology requires specialized medical treatment.

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Aphakia, pseudophakia

A disorder of the visual apparatus in which the eye lacks a lens is aphakia. Pseudophakia is the presence of an artificial lens in the eye. Its implantation is performed to correct aphakia. The advantage of this treatment method over glasses is the normalization of the visual field, prevention of distortion of objects, and the formation of an image of normal size.

Today, there are many designs of lenses. There are three main types, which differ in the principle of attachment in the eye chambers:

1. Prechamber lenses are placed in the anterior chamber of the eye, resting on its angle. They contact the iris and cornea, that is, the most sensitive tissues of the eye. They can cause the formation of synechia in the angle of the anterior chamber.
2. Pupillary or iris-clip lenses. They are inserted into the pupil like a clip and are fixed with the help of front and back support elements. The main disadvantage of this type of lens is the risk of dislocation of the support elements or the entire artificial lens.
3. Posterior chamber – placed in the lens bag after complete removal of its nucleus with cortical masses. Take the place of the natural prototype in the optical system of the eye. Provide the highest quality of vision, strengthen the connection between the anterior and posterior barrier of the organ. Prevent the development of postoperative complications: secondary glaucoma, retinal detachment, etc. Contact only with the lens capsule, which has no nerve endings and does not cause inflammatory reactions.

Artificial lenses for pseudophakia in aphakia are made of soft (hydrogel, silicone, collagen copolymer) and hard (polymethyl methacrylate, leucosapphire) materials. They can be multifocal or made in the form of a prism. Treatment is carried out by surgical methods that are based on enhancing the refractive power of the cornea.

Post-traumatic aphakia

One of the causes of aphakic eye is trauma and injury. Posttraumatic aphakia develops due to the destruction of the lens or its loss with extensive corneal or corneoscleral injuries. In some cases, dislocation of the lens under the conjunctiva was diagnosed with contusion ruptures of the sclera.

Very often, the pathological condition develops when removing a traumatic cataract or when the lens is dislocated after a contusion injury. Traumatic cataract can cause sphincter ruptures and mydriasis, formation of scars on the iris, appearance of traumatic colobomas, ectopia of the pupil, aniridia.

In addition to aphakia, secondary membranous cataract leads to clouding of the vitreous body, partial atrophy of the optic nerve. Cicatricial changes in the choroid and retina, peripheral chorioretinal foci are also possible. Various correction methods and optical reconstructive surgeries are used for treatment.

Complications and consequences

A pathological condition in which the eye lacks a lens causes serious consequences and complications. First of all, it should be noted that in the complete absence of the lens, the vitreous body is held by its anterior border membrane. This leads to the formation of a protrusion in the pupil area, i.e. a vitreous hernia. Progression of the hernia is dangerous due to rupture of the anterior border membrane and the release of vitreous fibers into the anterior chamber of the eye. Another common complication of ophthalmological disease is clouding and edema of the cornea.

The monocular form of the disease is often complicated by aniseikonia. This complication is characterized by the image of different sizes being produced by the sick and healthy eye. This greatly complicates the patient's life. The congenital form of aphakia or the disease caused by the removal of the lens in childhood can be complicated by microphthalmia. Without appropriate treatment, the pathology leads to a significant deterioration in vision, loss of working capacity and even disability.

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Diagnostics aphakia

Diagnosis of an aphakic eye is not difficult, as the absence of the lens is visually noticeable. Diagnosis of aphakia begins with examination of the fundus using a microscope and a slit lamp. Examinations are necessary to determine the severity and stage of the disease, as well as to choose a method of treatment and correction.

The main diagnostic methods used for visual apparatus disorders:

• Ophthalmoscopy
• Refractometry
• Slit lamp biomicroscopy
• Ultrasound (to rule out retinal detachment)
• Visometry
• Gonioscopy

Visometry determines the degree of visual acuity reduction. Gonioscopy is used to determine the severity of the deepening of the anterior chamber of the eye. Ophthalmoscopy can reveal concomitant pathologies, as well as cicatricial changes in the retina, choroid, and optic nerve atrophy.

The main diagnostic criteria of aphakia are: trembling of the iris when moving the eye, lack of supporting function of the lens, deep anterior chamber, astigmatism. If there was surgical intervention, a scar is determined.

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Tests

Laboratory diagnostics of visual apparatus disorders is carried out both at the stage of diagnosis and during treatment. Tests for aphakia consist of:

• Complete blood count
• Blood sugar test
• Blood for RW and Hbs-antigen
• General urine analysis

Based on the results of the studies, the doctor draws up a treatment plan for both the underlying disease and any associated ones.

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Instrumental diagnostics

Examinations for aphakia, conducted with the help of various mechanical devices, are instrumental diagnostics. In ophthalmological diseases, the following methods are used: visometry, perimetry (determining the boundaries of the visual field), biomicroscopy, tonometry (intraocular pressure), ophthalmoscopy, ultrasound examinations. They allow determining the severity of the disease and other features of its course.

When examining an aphakic eye, attention is drawn to the deep anterior chamber and trembling of the iris (iridodonesis). If the posterior capsule of the lens is preserved in the eye, it restrains the jolts of the vitreous body during eye movements and the trembling of the iris is expressed less strongly. During biomicroscopy, a light section reveals the location of the capsule, as well as the degree of its transparency. In the absence of a lens bag, the vitreous body, held only by the anterior limiting membrane, is pressed and slightly protrudes into the pupil area. This condition is called a vitreous hernia. When the membrane ruptures, vitreous fibers come out into the anterior chamber. This is a complicated hernia.

Differential diagnosis

In most cases, anamnesis is sufficient to establish a diagnosis of aphakia. Differential diagnostics are performed for both congenital and acquired forms of the disease. Monocular and binocular types of pathology require differentiation. The disorder is compared with ophthalmological disorders with similar symptoms.

The aphakic eye is characterized by the following signs:

• Deterioration and change in visual function.
• A sensation of a foreign body in the eye, spots and a veil before the eyes.
• Blurred and unfocused vision due to impaired accommodation.
• Trembling of the iris and vitreous body.
• Destruction of the posterior lens capsule and extrusion of the vitreous body or parts of the lens through the pupil.
• Cicatricial changes in the cornea (if the disease is caused by severe forms of conjunctivitis).
• Coloboma in the upper parts of the iris.

For differentiation, both instrumental and laboratory diagnostic methods are used.

Treatment aphakia

After the removal of the lens, the refraction of the eye changes dramatically. High degree hyperopia occurs.

The refractive power of the lost lens must be compensated by optical means - glasses, a contact lens or an artificial lens.

Spectacle and contact correction of aphakia are rarely used nowadays. To correct aphakia of an emmetropic eye, a spectacle lens with a power of +10.0 Dptr is required, which is significantly less than the refractive power of the removed crystalline lens, which is on average 19.0 Dptr. This difference is explained primarily by the fact that the spectacle lens occupies a different place in the complex optical system of the eye. In addition, a glass lens is surrounded by air, while the crystalline lens is surrounded by liquid, with which it has almost the same refractive index of light. For a hypermetropic person, the glass power must be increased by the required number of diopters, while for a myopic person, on the contrary, it will be thinner and have a lower optical power. If before the operation myopia was close to 19.0 Dptr, then after the operation, the too strong optics of nearsighted eyes are neutralized by removing the crystalline lens and the patient will do without glasses for distance vision.

The aphakic eye is not capable of accommodation, so for working at close range, glasses are prescribed that are 3.0 D stronger than for distance. Spectacle correction cannot be used for monocular aphakia. A +10.0 D lens is a strong magnifying glass. If it is placed in front of one eye, then the images in the two eyes will be too different in size, they will not merge into a single image. For monocular aphakia, contact or intraocular correction is possible.

Intraocular correction of aphakia is a surgical operation, the essence of which is that a clouded or dislocated natural lens is replaced with an artificial lens of the appropriate power. The calculation of the dioptric power of the new optics of the eye is performed by a doctor using special tables, nomograms or a computer program. The following parameters are required for the calculation: refractive power of the cornea, depth of the anterior chamber of the eye, thickness of the lens and length of the eyeball. The general refraction of the eye is planned taking into account the wishes of the patients. For those of them who drive a car and lead an active life, emmetropia is most often prescribed. Low-degree myopic refraction can be planned if the second eye is nearsighted, as well as for those patients who spend most of the working day at a desk, want to write and read or do other precision work without glasses.

Correction of aphakia in children

To achieve high visual acuity in children with aphakia, careful correction of refractive errors is necessary. As the eye grows and its refraction decreases, periodic replacement of contact lenses is required. Correction of aphakia can be carried out using the following methods.

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Glasses

This is the main method of correcting bilateral aphakia, but in unilateral aphakia, glasses are rarely used, only in cases of intolerance to contact correction. One of the advantages of glasses is their relatively low cost. Disadvantages include the difficulty of fitting heavy glasses to a young child, as a small nose cannot support many spectacle frames.

Contact lenses

Contact lenses remain the primary method of correcting both unilateral and bilateral aphakia. Soft gas-permeable and even rigid contact lenses are used for children in this group. Silicone contact lenses are especially effective in the first months of life. Frequent lens loss and the need to replace them as the eye grows increase the cost of this correction method. Although there are reports of keratitis and corneal scarring in children with aphakia, these problems are extremely rare.

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Epikeratophakia

This procedure using a superficial lamellar corneal graft has proven to be inappropriate and is now rarely used.

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Intraocular lenses

In children, intraocular lenses are more often used to correct aphakia after removal of progressive and post-traumatic, less often congenital cataracts. Many authors indicate the possibility of their implantation even in children aged 2 years. At this time, the growth of the eye basically ends and it becomes possible to calculate the lens power for a child as for an adult patient. The issue of implantation of intraocular lenses for congenital cataracts is still controversial.

Implantation in the first weeks of life during primary surgery is not advisable. The upcoming growth of the eye complicates the problem of calculating the power of the intraocular lens; in addition, this pathology is often accompanied by microphthalmos. There is a question whether the intraocular lens itself affects the physiological growth of the eyeball.

Thus, in most cases, primary implantation is not recommended for true congenital cataracts, although secondary intraocular lens implantation in older children and those with high visual acuity is becoming increasingly popular.

In older children with traumatic cataract, intraocular lens implantation is a common treatment method. Currently, the most common method is intracapsular fixation of a monolithic PMMA IOL.

Prevention

There are no specific methods for preventing the congenital form of aphakia. Prevention is necessary for acquired pathologies of the visual apparatus. For this, it is recommended to undergo annual examinations by an ophthalmologist. The doctor will be able to promptly identify diseases that require surgical removal of the lens. For people who are at risk of eye injuries due to the specifics of their profession, prevention consists of using protective masks and glasses.

To maintain healthy vision, you must adhere to the following rules:

• Balanced nutrition.
• A good night's rest.
• Minimum visual overload.
• The correct mode of working at the computer.
• Conducting eye exercises.
• Regular preventive examinations by an ophthalmologist.
• Observe safety precautions when performing work that is hazardous to the eyes.
• Protecting eyes from ultraviolet radiation.

Aphakia is a serious disease that can lead to vision loss. Preventive measures can minimize the risk of this pathology.

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Forecast

The most unfavorable prognosis is for the unilateral form of aphakia. This is due to the risk of complications with aniseikonia. Congenital forms are characterized by a progressive decrease in visual acuity, which without timely treatment can cause blindness. As for the post-traumatic form of the disease, it is characterized by an increase in symptoms with early pain syndrome, pronounced local edema and a progressive decrease in visual acuity.

Aphakia leads to temporary disability, and in some cases to permanent disability. If there are no changes in the eye's neuroperceiving apparatus and correct optical correction is performed, the prognosis is favorable, since high visual acuity and ability to work are preserved.

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