Optical correction is one of the oldest methods of vision correction. Usually it is utilized at the initial stage of the treatment of amblyopia, strabismus and refractive disorders. It helps stimulate visual functions in children, contributing to the normalization of binocular functions development. Using optical correction is possible from the age of 6 months old. Objective parameters of cycloplegic refraction must be taken into account. Cycloplegia allows to “turn off” accommodation process temporarily in order to evaluate the refraction in the child carefully and precisely. The doctor evaluates all the data obtained, takes into account the existing complaints of parents and patient to choose the appropriate treatment.
There are several options of optical correction:
1. Spectacles – one of the most popular method of optical correction in children of preschool age
- high degree of congenital hyperopia (for prevention of development of strabismus and amblyopia);
- congenital myopia (or acquired in an early age);
- amblyopia and strabismus (of any kind);
- prevention of amblyopia
- intolerance to contact lenses vision correction (after congenital cataract surgery);
- anisometropia of moderate degrees (if the difference in the refraction between two eyes is greater than 3 diopters, correction by spectacles is quite easily tolerated in childhood);
- psychological instability of a child, a pronounced discomfort (risk of trauma to the child’s eyes, the formation of a psychological “block” for any further manipulations).
Fitting and use:
Fitting is carried out in one or several stages, depending on the age of the child and the existing vision disorders.
The first stage is the assessment of refraction under conditions of cycloplegia (wide pupil, induced paralysis of the ciliary muscle). For cycloplegia, a 1% cycloplentolate solution or 0.1-1% atropine solution is used. The most common instillation scheme is as follows: 1 drop in both eyes (twofold) with an interval of 10-15 minutes. Sometimes, the doctor may prescribe instillation of this drug at home for 3-5 days in cases of:
- the lack of effect of instillation during examination (increased tone with hyperopia, difficulty installing the drug into the conjunctival cavity of infants);
- insufficient effect (usually associated with the color of the eyes of the child, in carie-eyed cycloplegia is achieved more slowly than in light-eyed children);
- accommodative strabismus in children with hyperopia;
- psychological instability (fear of doctor) or mental disorders (instillation of the drug at home does not cause stress and does not cause fear of visiting the doctor’s office).
The second stage is fitting in order to check visual acuity taking into account the obtained values of refraction, assessment of refraction after 3-5 days of cycloplegia, assessing the position of the eyes with objective correction (when lenses’ power is not taking into account visual acuity) in children with strabismus.
The duration of wearing spectacles is determined by the doctor depending on the pathology, but most often ophthalmologists advocate the principle of constant wearing with follow-up visits once every 2-3 months. During these visits, the position of the eyes, visual acuity and the overall state of the child are assessed.
2. Contact lenses vision correction. Some parents still consider contact lenses harmful to chilren’s eyes, but any ophthalmologist or optometrist will say that this is not the case. Advancement of contact lens materials and possibility of customization allow doctors fit contact lenses in children as young as several months old.
- complex refractive disorders (refractive errors of high degrees), anisometropia greater than 3 diopters, severe astigmatism, post-surgery aphakia, congenital aphakia)
- therapeutic purposes (need for occluding soft contact lenses)
- convergence excess
- cosmetic purposes in case of congenital or acquired anomalies of the anterior segment of the eye (congenital aniridia, post-traumatic aniridia, post-burn corneal leukoma, congenital corneal dystrophy, etc.)
- the impossibility of using spectacles due to an active lifestyle
- psychological factors (reluctance to use spectacles for vision correction)
- intolerance to contact lenses (allergic reactions, excessive discomfort, risk of hypoxic complications, etc.);
- acute or chronic inflammatory diseases of the anterior segment of the eye (seasonal conjunctivitis due to allergies);
- profession or hobby that may limit the use of soft contact lenses;
- insufficient adherence to treatment by parents, inability to strictly follow the guidelines as to use and care;
- latent strabismus (relative contraindication).
Fitting and use
The approach is patient-specific. Most optometrists consider that for children, especially young, the best option is to use daily replacement soft contact lenses or frequent replacement lenses (replacement is more frequent than once a month). Such lenses minimize the risk of secondary complications (conjunctivitis, keratitis), which may be due to improper care of the lenses during scheduled replacement or violations of the lens installation technique. The latter is most applicable to parents who help or fit contact lenses in children themselves. It was revealed that children are able to look after contact lenses better than many adults. Scheduled replacement lenses (replacement is less frequent than once a month) or extended wear contact lenses can also be used in children, but the using such lenses requires an even more careful monitoring, due to a relatively higher risk of complications.
Fitting contact lenses in children of 6-7 years old is not very different from fitting lenses in adult patients. In children of a younger age group, the fitting is often carried out empirically when the doctor evaluates several main parameters:
- corneal diameter;
- corneal curvature (keratometry);
After the examination, necessary parameters of the contact lenses are calculated (base curvature – BC and lens diameter – Dia). Fitting soft contact lenses is carried out without instillation of drugs that dilate the pupil. Leneses are fit (by the doctor himself), then the fit, lens mobility and centration are evaluated. If necessary, the lens parameters are changed and a second examination is carried out.
In infants, this fitting method is not applicable and usually, after calculation of lens parameters, the doctor fits lenses, assesses the fit, instructs parents regarding the lens installation and removal technique and schedules a second appointment to evaluate how well treatment was working.
3. Vision therapy
A set of various exercises and physical therapy that help normalize and stimulate visual functions. The choice of a particular treatment depends on the vision disorder. In Russia, several types of vision therapy are usually distinguished:
a. Pleoptic treatment – system of methods aimed at the treatment of amblyopia:
i. Occlusion – the method the essence of which is to cover (occlude) a better seeing eye to improve the vision in the lazy eye. It is important to explain to parents that this procedure does not correct refractive errors and does not cure strabismus, which was the reason for the formation of amblyopia. Occlusion is best used in conjunction with optical correction.
Principles of use
The use of occlusion is possible from the very birth, if the doctor has identified the appropriate indications – congenital strabismus, severe refractive errors (high hyperopia, high myopia, anisometropia).
- monocular occlusion, when only one, better seeing eye is covered;
- alternating occlusion, when both eyes are alternately covered (used in children with a high risk of amblyopia, strabismus, to simultaneously stimulate both eyes or in the absence of a dominant eye);
- direct, when the better seeing eye is occluded
- inverse, when the worse seeing eye is occluded
- full-time – during an entire day
- part-time – during 3-4 hours
The duration and type of occlusion is determined for each patient individually and may vary during treatment based on its course. The most common occluders are made of plastic that are attached to the spectacle frame, or various home-made occluders of various types. Occluders can be opaque, translucent, depending on the task and the psychological state of the child.
In most cases, occlusion therapy requires incredible patience as children tend to put off the occluders, glasses with occluders, especially in cases of severe degrees of amblyopia (visual acuity < 0.1), which negatively affects the healing process. In this case, the doctor can choose the so-called "occluding contact lenses" These are soft contact lenses that are colored in a central optical zone either partly (from 3 mm) or fully (up to 12.5 mm). This method was first tested in the USA and is being successfully applied at present.
The research has shown significant efficacy of utilizing such lenses and an improvement in children’s adherence to treatment, due to a decrease in cosmetic discomfort compared to wearing patches (Collins, McChesney et al, 2008).
Specifics of the method
In cases of a full-time monocular occlusion, visual acuity of the better seeing eye may decrease. In such cases, it is advisable to switch to alternate occlusion. Alternating occlusion schemes imply, for example, 6 days occlusion of a better seeing eye and 1 day occlusion of an amblyopic eye.
Occlusion therapy is performed in series of repeated courses, each lasting at least 2-3 weeks, depending on the severity of amblyopia and the presence or absence of visual fixation disorders. Courses can be repeated up to 6 times a year, depending on the observed dynamics.
Occlusion does not treat strabismus, but it improves and evens out the visual acuity of both eyes, which is usually a good sign and increases the likelihood of maintaining the correct position of the eyes after surgical treatment. After occlusion therapy is cancelled, visual acuity of the squinting eye may again deteriorate, albeit slightly.
It is important to keep in mind that a prolonged occlusion can disrupt binocular functions, so it is important to use the tactics of a gradual transition to other stages and methods of treatment such as penalization. Recommended duration of a single course of occlusion therapy is 14-20 days.
ii. Penalization is a method of pleoptic treatment of amblyopia, which implies creation of artificial anisometropia (difference in refraction between the eyes greater than 1 diopter), which leads to a decrease in visual acuity of the dominant eye and the development of visual fixation in an amblyopic eye.
Principles of use
A distinctive feature of penalization is that the better seeing eye maintains spatial perception and remains uncovered while its visual acuity decreases. This result can be achieved in the following ways:
- Pharmacologic penalization implies instillation of atropine into the sound eye to prevent accommodation. It is thought to operate by blurring vision in the sound eye at near, thus forcing the amblyopic eye to be used preferentially for near vision tasks. When the sound eye is hypermetropic, the penalization effect can be potentiated by prescribing less than the full hyperopic correction for the sound eye, blurring its vision at both near and distance fixation. Pharmacologic penalization has been usually advocated for mild or moderate amblyopia (20/100 or better), because it is thought to be insufficient when acuity in the amblyopic eye is worse than 20/100;
- Optical penalization implies adding plus correction to cycloplegic refraction in the sound eye (until fixation at distance shifts to the amblyopic eye); it is a useful alternative to occlusion for treating amblyopia, and as maintenance therapy following occlusion. It is particularly useful in cases of patching noncompliance. The major key to patient acceptance is choosing the minimal amount of penalization necessary, while still ensuring that the patient actually switches fixation to the amblyopic eye.
Specifics of the method
This method allows you to connect the amblyopic eye to active work and not exclude (as in case of occlusion) the fixing eye from seeing. In case of a severe amblyopia (visual acuity of the amblyopic eye lower than 0.1), the child may refuse to use the classic occlude. In this case, penalization may be the best and sometimes the only applicable method of pleoptic treatment.
iii. After-image method – use of images occuring after a blinding retinal glare and visible with eyes open and closed
The visible image will correspond to the source that caused this blinding light (for example, the flash of the camera, the letters of the board, the bright light of the lamp). After light, during blinking, the alternation of light (negative) and dark (positive) sequential images takes place.
Principles of use
The child is wearing an occludor on the better seeing eye, spectacles are put on; then the gaze is fixated on a round black mark located on a white, luminous screen from at distance of about 10-15 cm. The child looks at the fixation mark during 20-30 seconds to blind the peripheral retina.
After turning off the screen, the child can return to his or her activities, you can even ask to draw an image that is now visible. When blinking, images alternate from positive (dark) to negative (light).
The procedure is repeated after the child noted the disappearance of the visible image. On average, up to 30 exposures take place during one session. Up to 15-20 sessions per day can be performed. The duration of each session is within 60 minutes. The duration this treatment depends on the results obtained and the overall treatment dynamics.
Specifics of the method
The need for a good intellectual level of development of the child to understand the consequences of this method. Therefore, this method is not most commonly used.
iv. Red light therapy – method based on the fact that red light selectively stimulates the cones of the retina. Thus, the fovea with its exclusive cone component is predominantly stimulated by the light which passes through a red filter.
It is recommended for patients:
- with very unstable visual fixation;
- of 3-4 years old with any fixation;
- of5-6 years old with central fixation, but suffering from an increased motor tension;
- with nystagmus.
Treatment is performed under conditions of a full correction, with occlusion, 1-2 times a day during 60 minutes. During the procedure, the most important thing is to maintain the activity of the child.
v. Cross-strobing (by Pospelov) is used for treatment of strabismus. It is based on the principle of the aspiration of the human brain to combine received, slightly heterogeneous images into a single image.
This mechanism is disturbed in children with strabismus, when the brain receives pronounced asymmetric visual information from both eyes, which leads to further suppression of the image from the squinting eye and there is an alternate perception of the right or left image. Contraindication for this method is a pronounced eccentric (off-center) visual fixation.
Principles of use
The treatment method is very easy to use and is often prescribed for home practice. A flashlight (preferably a diode) is covered in front by an opaque shutter with a slot, like a keyhole. Parents are asked to fix the child’s gaze on the switched on flashlight – which is located 10-15 cm away – through the center of the keyhole. The duration of fixation is 20-30 seconds, for one eye the keyhole is horizontal, while for the other it is vertical. After exposure, the child is asked to close his eyes and, in order for him to recognize the obtained images, direct the light from the flashlight to his eyes. When the child understands what he sees, they ask him to open his eyes and sketch the picture he saw, according to which his perception is evaluated. Treatment is successful if, according to the results of the courses, the child sees a figure in the form of a cross (+) and can hold images in the form of this figure for some time. This indicates the achievement of a bifoveal fusion and the absence of physiological and pathological blind spots in the field of view of the child, even in the presence of strabismus.
A similar method is used after surgical treatment as an additional method of stimulation.
- increased intracranial pressure;
- malignant neoplasms;
- motor anxiety (hyperactivity disorder).
vi. Laser speckle contrast imaging (LSCI) is based on the use of low-intensity laser radiation projected into the central zone of the retina (macula) and has a tangible stimulating effect, which contributes to the improvement of visual functions.
Principles of use
This method is not applicable for home use and is an integral part of the vision therapy cabinets. The main principle of treatment by laser stimulation devices is that the child fixes his gaze on the sources of laser radiation fixed at various distances (depending on the settings of the device, the installed power and the degree of vision disorder), guided by the doctor or nurse throughout the course of treatment. The duration of one session does not exceed 10 minutes, 1 course comprises from 10 to 15 sessions, depending on the severity of vision disorder and the child’s readiness for similar medical procedures. During the treatment process, in addition to the distance to the laser radiation source, the doctor or nurse can change the power and frequency of the laser radiation to enhance the therapeutic effect.
Specifics of the method
This treatment method requires careful selection of patients, since a long fixation at one point is required during the treatment process, which is not possible for all young patients, even under the supervision of a specialist and parents. Without proper attention and interest of the child, the laser will not be able to focus on the central area of the retina and the effect of the treatment will be extremely low.
In most cases, laser stimulation does not act as the leading and only treatment, and is usually prescribed in combination with other methods.
Psychogenic factors, hyperactivity, age under 4-5 years, presence of concomitant neurological disorders, impaired transparency of the optical media of the eye (after injuries, surgical interventions, inflammatory processes).
vii. Stimulation methods utilizing digital devices. These methods are relatively young and have recently started attracting attention of ophthalmologists around the world. The development of multimedia technologies encourages creation of more and more portable gadgets that attract the attention and help treatment of the visual system. Some gadgets not only help develop visual functions, but also motor skills, enhance perseverance, which also positively affects the overall results of treatment.
- Pleoptica-3 is the most famous computer software for visual stimulation in the Russian Federation and some CIS countries. It includes a large selection of simple, easy-to-understand programs that help stimulate visual functions. Most programs are built on a frequency, contrast or color effect. Despite its advantages (simplicity), based on the practical observations of many experts, these programs are significantly inferior in developing the child’s interest and commitment to treatment compared to any games that are now created for digital devices.
- AmblyoPlay – a vision therapy solution for children with lazy eye, mild strabismus or convergence insufficiency that is performed through playing therapeutic games and exercises every day for 30 minutes.
- SEN SWITCHER – a web resource of Ian Bean, one of the leading experts in the field of communication training and exposure to computers and other devices of children with severe psycho-neurological impairments. This resource is filled with many different programs rather auxiliary than stimulating in nature. Often this resource is used to advise parents in order to develop the child’s desire to engage in and conduct therapy, allows you to quickly go through the adaptation to occlusion, penalizing and captivating the child with various simple games that require attention and tactile action.
b. Orthoptic therapy is a program of eye exercises designed to help people with eye-focusing problems. These exercises are mostly prescribed for children with convergence and/or accommodative insufficiency.
This method is usually a next step after occlusion or penalization, since the main condition for orthoptic treatment is the presence of almost symmetric indicators of visual acuity in both eyes. Orthoptic treatment is carried out under conditions of haploscopy (separation of the visual fields of the right and left eye).
Synoptophore – a device designed for the diagnosis and treatment of various types of oculomotor disorders (strabismus). The device utilizes principle of artificial separation of visual fields (haploscopy) by presenting various test objects separately for each eye through special optical heads. In orthoptics, in addition to diagnostic aspects, a synoptophore is used for developing the amplitude of eye movements, develop fusional reserves (reserves that allow you to keep two different images visible by the right and left eye), stimulate and maintain binocular functions (eliminate functional blind spots, asymmetric binocular vision, bifoveal image merging).
Principles of use
The device is applicable if visual acuity in both eyes is not lower than 0.4 (as per decimal scale) and the difference between the visual acuity of both eyes does not exceed 1 line. Initially, the following parameters are determined:
- objective strabismus angle — the angle determined without taking into account the subjective perception of the image by the child
- subjective strabismus angle — the angle determined after the objective angle that takes into account the presence or absence of a combined (“merged”) image in front of the eyes, which indicates the presence of bifoveal fusion of images when set in accordance with the strabismus angle
These are two main parameters, based on which the doctor suggests a treatment plan and evaluates the prospect of a further need for a surgical treatment. Since the synoptophore does not correct strabismus, it creates artificial conditions for enhancement of binocular functions, thereby it trains the visual analyzer and prepares for the simultaneous perception of two images after surgical treatment, when both eyes will be in the correct position.
If such stimulation was not performed in a timely manner or was not performed at all, after surgical treatment there may be a relapse and resumption of the strabismus angle, since the eye does not take into account the images entering the squinting eye.
Having determined the objective and subjective strabismus angle, the doctor compares the results obtained, which is important for assessing the prospects of treatment:
- If objective squint angle (OSI) = subjective angle (SSI), then identical (corresponding) areas of the retina of both eyes are stimulated and the central area of the retina of the squinting eye is functioning correctly. If OSI = SSI = 0, then strabismus is absent;
- IF OSI is not equal to SSI, but the difference is not more than 3-4 degrees, then there is an abnormal retinal correspondence, which is typical for small strabismus angles, when adaptation does not stimulate the central fossa of the retina of the squinting eye, but the areas located nearby. In this case, two main options are possible: an abnormal retinal correspondence of harmonic type or non-harmonic type;
- The presence or absence of a functional suppression scotoma.
The minimum number of sessions is 15-20 per course. To achieve long lasting positive results, at least 4 courses per year are required, especially considering the fact that the first course is always introductory to the child and the effect of its implementation is minimal.
Specifics of the method
Therapeutic tactics are based on subjective indications (responses of the child), which affects the results of treatment and diagnostics, as well as the results of repeated studies, when the values obtained change. Other features of the device include its limited effect on the oculomotor system. Usually doctors can most effectively influence the oculomotor system and improve binocular functions in children up to 3-4 years old, however this device cannot be used in patients that young, since verbal contact with the child is difficult and the specialist cannot obtain the results of the subjective strabismus angle. At an older age, chances of dramatically affecting binocular functions are reduced and the synoptophore gains more diagnostic value than therapeutic value.
- early age of the patient
- psychomotor disturbances
- hyperactivity, restlessness, distracted attention syndrome
- asymmetric visual acuity (difference in VA between the eyes is greater than 1 line)
- large squint angles (> 35 degrees)
- non-harmonic abnormal retinal correspondence
c. Diploptic treatment is a term first proposed in the 1980s by academician E.S. Avetisov, describing a set of measures aimed at restoring, developing and stabilizing a normal binocular vision (in children with normal retinal correspondence).
Unlike orthoptic treatment, diploptic treatment is performed in natural conditions, without separation of the fields of view (haploscopy). Treatment suggests achieving of doubling (diplopia) by irritating various parts of the retina with the help of prisms and developing the ability to merge double images. The main condition and indication for diploptic treatment is the visual acuity of both eyes of at least 0.5 (as per decimal scale) and the presence of a bifoveal fusion.
There are several methods of diplopic treatment:
i. A training method with prismatic lenses. One of the main methods of diploptic treatment using trial prismatic lenses, conventionally divided into several stages:
- 1st stage – induction of double vision (diplopia). On average, the stage lasts 2-3 days. At this stage, the child is presented with a test object (drawing, a symbol for checking eyesight) at a distance of 1-2 meters, at which the child fixes his gaze, in the selected optical vision correction tool and with prismatic lenses installed on top (in front of a better seeing eye);
- 2nd stage – the development of the binocular fixation reflex (bifixation, the ability to merge images perceived with two eyes). If the child notes the appearance of double vision, then we proceed to the second stage of treatment. The goal of this step is to make the sensorimotor system stop induced ghosting by fusing the two images. To facilitate the treatment at this stage, you can use larger test objects for fixation and increase the time of presentation in front of a better-seeing eye prism (up to 5 seconds). The duration of the second stage usually lasts no longer than 15 days.
- 3rd stage – fixing the reflex of bifixation. In case there is positive dynamics and the development of suppression of induced diplopia, we proceed to the stage of consolidating the results and the development of the ability to retain the bi-fixation of double images in conditions of increasing visual load. We use prismatic lenses with a power of 8-10 diopters, increasing the frequency of their presentation to 2-3 seconds. In addition, we gradually move the test objects away (from 1 to 4 meters).
- Upon achieving positive and sustainable results, we proceed to the final stages:
- development of fusional reserves (FR, positive for convergence, negative for divergence), using a synoptophore;
- stimulation of the development of stereoscopic vision using the Worth’s test, programs using anaglyph (and / or 3D glasses).