Ординатура / Офтальмология / Английские материалы / Pediatric Ophthalmology Current Thought and A Practical Guide_Wilson, Saunders, Trivedi_2008

Figure 4.3 is a flow chart showing one method for monitoring and adjusting amounts of patching. If improvement stops after 2 h of prescribed patching, then the patching dose could be increased to 6 or more hours of prescribed patching. Some parents and children are initially enthusiastic but become fatigued after several months and compliance suffers. In these cases, switching to another treatment, such as atropine, may be useful. Some children stop

good compliance with patching. Once the maximum visual acuity has been established, treatment may be weaned while monitoring to insure that visual acuity does not worsen. For example, 6 h of daily patching might be weaned to 2 h daily patching for 6−8 weeks prior to stopping treatment. Treatment is stopped with or without weaning if amblyopia resolves, and one definition of resolution is visual acuity of the amblyopic eye within one line of the sound eye.

The most common reason for ineffectiveness of patching is non-compliance, since many children refuse to wear an eye patch. Some children, particularly those old enough to attend school, refuse to wear a patch because of the social stigma. Others have recurrent problems with skin irritation. However, the majority of non-compliant preschool children refuse to wear a patch because they do not like it, and their parents are unable or unwilling to force them to wear it. Awan et al. included compliance data in their report of a randomized controlled clinical trial of unilateral strabismic and mixed amblyopia using occlusion dose monitors [3]. They reported mean compliance rates of 58 and 41% for 3 and 6 h of prescribed daily patching, respectively. Other authors have reported that compliance is a major problem with regard to occlusion therapy [15, 23, 29, 47, 50].

the reduction in vision. Strabismus is sometimes a consideration when deciding whether to use atropine or not, since some physicians prefer to avoid atropine in the presence of esotropia, particularly when it has an accommodative component. However, one study found no difference in the occurrence of new strabismus or the resolution of existing strabismus in patients treated with patching versus those treated with atropine [35]. With regard to family dynamics, the physician or orthoptist can often get a sense at the first office visit whether or not patching is likely to be successful. If the child does not follow directions from the parent(s) and/or the parent(s) express concerns about being able to get the child to wear a patch, then penalization is likely to be the best choice for initial therapy.

4.4.8Penalization

As a result of poor compliance with patching among many children, other treatments collectively known as penalization are commonly used [5, 60]. Types of penalization include atropine eye drops [13, 14, 28, 43, 44, 51, 57], optical penalization using a plano (blank) lens or excessive plus power lens, atropine with a plano lens [66], Bangerter filters (or “foils”) [19, 22], and translucent tape. There are several factors to consider when deciding whether to prescribe patching versus penalization, including (1) age of the child, (2) depth of amblyopia, (3) need for glasses,

(4) amount of hyperopia, (5) presence or absence of strabismus, and (6) family dynamics. Age is an important consideration because penalization is used less frequently in preverbal children in whom visual acuity in the normal eye cannot be reliably measured and closely monitored. Penalization is rarely required in infants, because they are unable to successfully remove a patch. Depth of amblyopia is considered because some forms of penalization may not be successful in cases of severe amblyopia. The need for glasses is considered because some forms of penalization such as Bangerter foils rely on the patient wearing glasses. The amount of hyperopia is important when deciding whether to replace a prescription lens with

4.4.9Atropine

The most commonly used form of penalization is atropine. The dosage of atropine for amblyopia treatment is one drop of 1 or 0.5% in the fellow eye as infrequently as once weekly [48] or as frequently as once daily. The best patients to consider for atropine treatment are (1) those who refuse to wear a patch,

(2) those with hyperopia, and (3) those old enough to allow the sound eye visual acuity to be closely monitored. Patients with hyperopia are ideal candidates for atropine penalization. Even if glasses correct their full amount of hyperopia, their near vision is always blurred after atropine, and they cannot clear it by removing their glasses. One study found that mean visual acuity at 33 cm after cycloplegia in children wearing their full cycloplegic correction was 20/120

[61]. Conversely, myopic children using atropine can see well with their fellow eyes through their glasses at distance, and many of them can remove their glasses to see better with their fellow eyes at near, depending on the amount of myopia present.

Manycliniciansnowroutinelyuseatropineasfirstline amblyopia therapy. Several PEDIG studies have provided data on the effectiveness of atropine for amblyopia, and Table 4.3 summarizes the results of these and other PEDIG amblyopia studies [58].ATS1 randomized 419 children age 3 years to <7 years with amblyopic eye acuity of 20/40 to 20/100 to at least

Atropine and patching are equally effective as primary treatment for moderate amblyopia

6 h prescribed daily patching produces improvement similar to fulltime patching for severe amblyopia

2 or 6 h of prescribed daily patching produce similar improvement for moderate amblyopia

Weekend and daily atropine produce similar improvement for moderate amblyopia

After a period of spectacles wear, 2 h daily patching is superior to continuing spectacles alone

6 h of daily patching or to once daily atropine [35].

Treatment intensity was increased or decreased based on interim visual acuities. After 6 months, amblyopic eye acuity had improved about three lines in both groups. Improvement was initially faster with patching, but atropine was better tolerated by many families based on results of a questionnaire (the Amblyopia Treatment Index) [17].Among the non-strabismic children, sensory outcomes were similar after 2 years

[42].

Weekend or daily atropine dosing appears to provide similar improvement, and weekend dosing has

the advantage of providing a short break from blur late in the week for many children. Amblyopia Treatment Study 4 found that weekend (once on Saturday and Sunday) or daily atropine improved acuity an average of about two lines after 4 months in children age 3−7 years with moderate amblyopia [34]. Interestingly, age, iris color, sound eye refractive error, and visual acuity in the sound eye after cycloplegia were not predictive of visual acuity improvement.

Some physicians believe that atropine is not effective in patients with severe amblyopia, but this premise is controversial. Traditional teaching is that

the visual acuity of the sound eye after cycloplegia must be worse than that of the amblyopic eye in order to cause the switch in fixation to the amblyopic eye necessary for visual improvement [27, 49]; however, near visual acuity after cycloplegia was measured in ATS1 and ATS4, and it was found not to be predictive of success with atropine treatment [34, 35]. It is possible that the dynamic accommodative demands of everyday life are not simulated well by a static test of near visual acuity. Consequently, many patients for whom the cyclopleged sound eye acuity exceeds the amblyopic eye acuity probably still switch their fixation to the amblyopic eye under certain conditions that are not simulated by a near visual acuity test.

4.4.10 Optical Penalization

Optical penalization of the sound eye can be accomplished with or without atropine. When used with atropine, optical penalization is done by reducing or eliminating the hyperopic correction for the sound eye [20]. This method is most often used in patients with significant hyperopia whose amblyopic eye visual acuity has not improved with atropine alone. In those patients who are not hyperopic but who wear glasses for other reasons, it is possible to replace the fellow eye lens with one containing more minus power; however, this may encourage non-compliant children to remove the glasses. If atropine is not used, optical penalization can be attempted by replacing the lens over the fellow eye with a fogging plus lens

[11]. Another technique is sometimes useful in children with bilateral aphakia who wear contact lenses. To treat unilateral amblyopia, the contact lens of the better eye can be removed for a few weeks. The best patients to consider for optical penalization are (1) those who have stopped improving using atropine alone, (2) those already wearing glasses or contact lenses, and (3) those who are aphakic, pseudophakic, or unable to accommodate with the fellow eye for any reason (e.g., third-nerve palsy). Optical penalization can be particularly effective in patients who cannot accommodate, because they are dependent on optical correction to allow proper focus at various distances.

4.4.11 Bangerter Foils

Bangerter foils are blurring filters of different densities that can easily be placed on the back surface of a spectacle lens to degrade the visual acuity of the sound eye and promote use of the amblyopic eye [19, 22]. Clinicians use different techniques to determine the density of filter to use for amblyopia treatment. Some clinicians choose a filter that will reduce visual acuity in the fellow eye to a level below that of the amblyopic eye; others assess fixation preference and choose a filter that results in a fixation switch to the amblyopic eye. A third method is to choose the initial filter empirically, selecting, for example, a 0.2 filter as a starting point for all patients. The best patients to consider for Bangerter foils are (1) those already wearing glasses, (2) older children or teenagers who are averse to wearing a patch, (3) those with mild, residual amblyopia, and (4) those with a history of amblyopia recurring when treatment was stopped. Advocates of Bangerter foils believe that they are particularly beneficial in maintaining visual acuity improvement and in preventing recurrent amblyopia, but data are sparse comparing them to patching or atropine.

4.4.12Penalization Treatment Regimens

In general, penalization is used for similar lengths of time (weeks to months) as occlusion therapy and is continued until visual acuity stabilizes or amblyopia resolves. Bangerter filters are often prescribed for longer periods of time than occlusion, and they are often used as a form of maintenance therapy. Eyes penalized by Bangerter filters, atropine, or other techniques should be monitored the same way that patched eyes are monitored. Assessment of visual acuity and ocular alignment should be performed at least every

2−3 months during active treatment of older children and more frequently for younger children. It is useful to discontinue atropine at least one full week prior to each examination, or its lingering cycloplegic effect can prevent accurate assessment of both visual acuity and ocular alignment. Generally, breaks from treatment are not needed when using penalization unless

reverse amblyopia is confirmed in an older child or suspected in a young child who is unable to perform recognition visual acuity.

4.4.13Amblyopia Treatment

in Older Children and Teenagers

Many ophthalmologists were taught that amblyopia treatment is not effective beyond ages 7−10 years; however, recent evidence shows that some older children and teenagers will respond to amblyopia treatment, particularly if they have had no prior amblyopia treatment.Amblyopia Treatment Study 3 randomized 507 children age 7−18 years to optical correction alone or to augmented treatment with 2−6 h of prescribed daily patching (and daily atropine for those age 12 years or less) [39]. The results showed that treatment with patching and atropine was superior to optical treatment alone in children age 7−12 years, with 53% of those who had augmented treatment improving by at least two lines. There was a significant age effect, as younger children showed a greater effect of augmented treatment relative to control than the older children. Although there was no significant difference between augmented and optical treatment in children age 13−17 years, 47% percent of teenagers without prior treatment improved by at least two lines.

4.4.14Complications

of Amblyopia Treatment

Reverse (iatrogenic or occlusion) amblyopia is uncommon [6]. Test−retest studies of visual acuity assessment in children indicate that a one-line reduction in acuity is likely due to chance [18].Areduction in the sound eye by two or more lines may be due to reverse amblyopia or to other factors such as poor performance, residual cycloplegic effect, inadequate relaxation of accommodation, or incorrect spectacle prescription. If reduction in visual acuity of the sound eye is suspected, visual acuity can be retested after giving the child a break. Minus lenses may be held

over the glasses if persistent accommodative tone is suspected in a child with hyperopia. Finally, repeating a cycloplegic refraction may be useful, and if the sound eye visual acuity is still reduced by at least two lines, then reverse amblyopia should be suspected and treatment should be discontinued. It is extremely rare for reverse amblyopia to be permanent.

Patching can cause skin irritation, particularly if the patch is frequently removed and reapplied or if the child has sensitive skin. Some brands of patches are purported to be gentler to the skin, but they have a disadvantage of coming off more easily. Skin emollients, breaks from patching, and changing the orientation of the patch may be helpful if skin irritation is problematic.

Side effects of atropine are classically described as “hot as a hare, red as a beet, dry as a bone, blind as a bat, and mad as a wet hen” [25]. More specifically, adverse effects include dryness of the mouth and skin, fever, delirium, tachycardia, and development of amblyopia in the sound eye [1, 26, 31]. Atropine should be avoided in patients with a history of a topical allergic reaction to it. Sunglasses with ultraviolet protection and/or a hat with a brim should be used when atropine-treated patients are exposed to bright sunlight, since it can make them uncomfortable and there is a hypothetical risk of lens and/or retinal damage from ultraviolet light entering the eye through a dilated pupil. For this reason, other treatments may be preferable for children who are frequently outside, such as those who go to the swimming pool often in the summer months. Atropine should also be prescribed cautiously or dosed relatively infrequently for children in school, since continuous blurring of the sound eye can significantly impact their academic performance. In such cases, a bifocal for the sound eye may be prescribed for schoolwork. Finally, Down syndrome children may be more susceptible to the side effects of atropine [2].

4.4.15 Treatment Outcomes

After treatment with spectacles, patching, atropine, and/or other modalities, many children obtain normal or near-normal visual acuity of the amblyopic eye; however, a sizable proportion fail to achieve normal vision even after increasing the dosage or

switching treatments altogether. These patients have “residual” amblyopia, and it can be frustrating to parents who view normal vision as the goal of treatment. Two years after children were randomized into ATS1, 181 of 363 (50%) still had amblyopic eye acuity no better than 20/32 [35]. It is unknown whether an intensive final push with treatment such as combined patching and atropine with or without a plano lens for the sound eye will improve visual acuity in these cases.

Some children show little or no improvement with any type of amblyopia treatment. In these cases, a dilated examination should be repeated with attention to subtle signs of organic disease, such as macular pathology or optic nerve hypoplasia or atrophy. Patients with unilateral high myopia often respond poorly to amblyopia treatment, and it is likely due to associated retinal abnormalities. If amblyopic eye visual acuity fails to reach 20/40 or better with treatment, then protective polycarbonate lenses should be prescribed if they are not already worn.

4.4.16Amblyopia Recurrence

After Cessation of Treatment

Asizable proportion of children get recurrence of amblyopia after treatment is stopped. Amblyopia Treatment Study 2C prospectively followed 156 children who had improved at least three lines, and for whom investigators were ready to stop amblyopia treatment

[40]. During the 1-year follow-up, reduction of acuity of 2 lines or more occurred in 21% of patients, and

40% of these recurrences occurred in the first 5 weeks after treatment was stopped. For those patients who had been treated with 6−8 h of daily patching, weaning prior to cessation of treatment seemed to reduce the chance of recurrence.

4.5Effects of Amblyopia in Adulthood

Intuitively, it is better to have excellent vision in two eyes instead of only one eye; however, binocular vi-

Take Home Pearls

•Spectacles alone improve bestcorrected amblyopic eye visual acuity by about three lines, so many patients do not need additional treatment with patching or penalization.

•Penalization is a viable option to occlusive patching in most patients with amblyopia. Penalization methods include atropine eye drops, optical penalization using a plano (blank) lens or excessive plus power lens, atropine with a plano lens, and Bangerter foils.

•Atropine may successfully treat amblyopia even when there is no apparent fixation switch to the amblyopic eye and when the atropinized sound eye near visual acuity remains better than amblyopic eye acuity.

•After stopping patching or atropine, about one in four patients will lose two or more lines of amblyopic eye visual acuity over the next 1 year.

•Amblyopia treatment may have its greatest benefit in later life, when sound eyes

can sustain injuries or be afflicted by diseases of the macula or optic nerve.

sual acuity (i.e., measured with both eyes open) is typically unchanged with amblyopia treatment, so some parents may wonder what effect amblyopia treatment really has on their child’s quality of life. Many of the rewards of amblyopia treatment may not be recognized until much later in life. One study showed that the risk of serious injury to the normal eye is increased in patients with poor visual acuity in the other eye [53]. Older adults often develop eye diseases, such as macular degeneration or glaucoma, which reduce their functional capacity. These diseases are often asymmetrical, so that the amblyopic eye may become the eye with better visual acuity in

later life. In addition, amblyopia treatment is associated with improvement in stereopsis, which is an important component of depth perception. Finally, amblyopia often co-exists with strabismus, and it has been hypothesized that better visual acuity and stereopsis may be associated with better long-term alignment after strabismus surgery. For these and other reasons, the benefits of early screening and treatment of amblyopia are well worth the cost [4].

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Contents

5.2Sources of Data and Their Limitations  . . . . .   48

5.4Available Data on Causes  . . . . . . . .   49

5.5Reasons for the Variation in Prevalence  . .   51

5.9Magnitude by Cause  . . . . . . . . . .   58

5.10Changing Pattern of Causes  . . . . . . .   58 References  . . . . . . . . . . . . . . . . .   59

Core Messages

•The prevalence and cause of blindness in children are related to levels of socio-economic development and

the availability of primary health care and eye-care services.

•There are ten times as many blind children per million total population in poor communities compared with affluent communities.

•The major preventable causes of blindness in children are declining in poor countries as a result of large scale public health interventions and cataract is becoming a relatively more important avoidable cause.

•Retinopathy of prematurity is an important cause in Latin America and Eastern Europe and is increasing in the emerging economies of Asia.

•Control requires comprehensive eye-care services, from community interventions through to specialist tertiary levels services.

5.1Introduction

Although much rarer than blindness in adults, control of the avoidable causes of blindness in children is a priority of VISION2020 – the Right to Sight [15, 43].

VISION2020 is a global initiative of the World Health

Organization (WHO) and the International Agency for the Prevention of Blindness, the latter being an umbrella organization which includes professional groups, organizations of, and for, the blind and international non-governmental organizations who support prevention of blindness activities. Children have been included in this initiative because the causes of blindness are so different from those in adults, and different strategies are required, from community level through to tertiary eye-care services. Another factor to consider is that most blindness is age related, whereas blind children have a lifetime of blindness ahead.

5.2Sources of Data

and Their Limitations

Designing and carrying out population-based studies of rare conditions is challenging, as large sample sizes are required. As far as blindness in children is concerned, sample sizes of 20−30,000 children would be needed to provide precise estimates of the prevalence, and the sample would need to be increased even further to obtain meaningful data on causes. There are additional challenges when studying children since measurement of visual acuity in young children in a field setting can be extremely difficult and school going children are not at home during the day except during the school holidays. For all these epidemiological and practical reasons there are only limited prevalence data from population-based surveys [8, 14, 28]. The available data are also difficult to compare and compile as some of the studies were undertaken several decades ago and different definitions of childhood and of blindness have been used. Some highly developed countries maintain registers of the blind which include children, and these can provide data on the incidence and causes of blindness in newly diagnosed children [19, 20, 31]; however, as with all registers there is likely to be under-report-

ing, and many observers are involved in categorizing the causes which can lead to misclassification and observer bias. In the U.K., the British Ophthalmological Surveillance Unit provides a mechanism for ophthalmologists to report new cases of rare conditions, and a recent study provided national data on the incidence and cause of blindness in children [30].

More recently, some data have become available from population-based sources in poorly developed countries, e.g. from house-to-house surveys and from studies using Key Informants who identify children who are blind in their own communities [5, 24, 47].

In 1993 a new system for classifying the causes of blindness in children was adopted by WHO which uses a descriptive, anatomical classification as well as an aetiological classification [10]. Information on the anatomical site can be obtained from all children examined but obtaining information on the underlying cause, which depends on the time of onset of the condition leading to blindness, is far more difficult.

This is particularly true in poorly developed countries where the medical history may be difficult to obtain, where the child may present very late and the clinical signs may be difficult to illicit, and because facilities and expertise for diagnostic investigations are limited. Since the WHO classification system was published many thousands of blind children have been examined. Most of the data have come from examining children attending schools for the blind, the advantage being that a large number of children can be examined quickly and easily; however, these data are subject to bias, since in poorly developed countries it is estimated that less than 10% of blind children are receiving any kind of education: those who are in school may be blind from different conditions from those who do not attend school. Examining children enrolled in community-based rehabilitation programs provides community-based data on causes [37] as does data obtained from studies using Key Informants as case finders [25]. These population-based sources are likely to provide more reliable information than facility-based studies.

Amajor limitation of theWHO classification is that at the time of its development WHO classified blindness on the basis of “best-corrected” visual acuity rather than “presenting” visual acuity. This means that the data collected to date do not include uncorrected refractive error as a cause of blindness. To address this limitation the WHO has recently revised the categories