Ординатура / Офтальмология / Английские материалы / Pediatric Ophthalmology for Primary Care 3rd edition_Wright, Farzavandi_2008

secondary scar contraction that causes retinal traction. In the mild form, cicatricial ROP produces peripheral retinal traction that pulls the retinal vascular arcades temporally, straightening the vessels. More severe temporal traction will drag the macula temporally, which may or may not interfere with vision. The dragged macula causes the eye to turn out to view (fixate) and gives the false appearance of an exotropia. This is called a positive angle kappa. Severe fibrosis and traction can lead to retinal detachment, which may be partial (stage 4) or total (stage 5). Circumferential traction causes a funnel shaped retinal detachment as seen in Figure 19 8.

Figure 19 8.

Stage 5 retinopathy of prematurity with total retinal detachment. The red area in the cutaway of the closed funnel detachment shows retinal vessels inside the funnel. Note that the retrolental membrane is pushing the lens and iris diaphragm anteriorly. There is a high incidence of angle closure glaucoma in these patients.

Managing Retinopathy of Prematurity

The most important aspects of managing ROP are prevention and early detection. Careful curtailment of oxygen with the physiologic reduced oxygen protocol is important to prevent vaso obliteration and eventual development of severe ROP, and careful screening for ROP is critical to identifying severe ROP that requires laser treatment.

Preventing Severe Retinopathy of Prematurity

Oxygen is one of the most common therapies used daily in premature infants, and hyperoxia is an important factor in the pathophysiology of ROP. Virtually all cases of ROP are associated with hyperoxia. Providing a stable, controlled, physiologic low oxygen environment with oxygen saturation tar gets between 80% and 93% has been shown to reduce and in some centers

almost eliminate severe ROP (Tin et al; Chow, Wright et al; Wright et al; Vanderveen). Keeping the oxygen saturation relatively low better emulates the physiologic low oxygen environment of the developing fetus than the pre viously used high oxygen protocols. Developmental outcomes and mortality have remained stable or have improved with the physiologic reduced oxygen protocol (Deulofeut).

Maintaining the physiologic reduced oxygen protocol without large fluc tuations in oxygen saturations is, however, difficult at best and in some cases almost impossible. Despite the challenges of managing extremely low birth weight infants, the goal of the neonatal intensive care unit team is to keep oxygen low and stable. The most critical period for careful and strict oxygen management is early, before ROP develops. Low and stable oxygen saturation levels must be initiated at birth and continued until the retinal vessels reach the periphery to Zone III.

Retinopathy of Prematurity Screening

Screening examinations are important to monitor the development of ROP. The multicenter trial investigating cryotherapy for ROP has shown a 50% reduction in vision threatening sequelae to ROP when treatment is applied in the active stage before development of retinal detachment. The initial neo natal nursery examination should be performed at 4 to 6 weeks after birth for

infants weighing less than 1,500 grams because this is when ROP first becomes evident. Prior to the eye examination in the neonatal intensive care unit, the baby’s pupils are dilated with cyclopentolate/phenylephrine combination drops. Drops should be instilled twice at 5 minute intervals. The dilated retinal examination includes scleral depression to visualize the peripheral retina. The insertion of an eyelid speculum is required to do this testing. It is important to remember to inform the patient’s family and nurses of the ocular status and proposed follow up after the examination.

Table 19 5 summarizes the protocol for examining immature infants. The frequency of follow up eye examinations is determined by the ophthalmologist based on the retinal findings. If immature retina is found in Zone III on initial screening but with no ROP, the eye examination is repeated every month until a normal regression pattern is established. Once normal regression is complete, plan a long term follow up in 6 months for an ocular examination includ

ing cycloplegic refraction. If stage 1 or 2 ROP is found, a repeat examination

Table 19-5. Screening Protocol for Preterm Infants

A.First Screening

According to guidelines published by the AAP, AAPOS, and AAO

 •   Preterm infants ≤1,500 g

 •  Gestational age ≤28 weeks  

 •   Preterm infants >1,500 g with unstable course (high risk)

 •   First examination by 4 to 6 weeks chronological age, 31 to 33 weeks  post-conception

B.Follow up Examinations

Follow-up examinations are determined by the ophthalmologist. Early Treatment of Retinopathy of Prematurity study showed that plus disease is an important sign of high-risk ROP.

Signs of High risk ROP

Zone I, any stage, with plus Zone I, stage 3, without plus Zone II, stage 2 or 3, with plus

should be performed approximately every 2 weeks, depending on the sever ity and zone, to monitor for progression. Once a normal regression pattern is identified, follow up examinations can be approximately every month. Patients with plus disease must be monitored very closely because this is the most important sign that laser treatment is indicated (Good WV et al). Once the ophthalmologist identifies that laser treatment is indicated, it should be given within 72 hours.

Treatment of Active Retinopathy of Prematurity (Laser Therapy)

Laser therapy acts by obliterating peripheral hypoxic avascular retina, reducing the production of VEGF and thus reducing neovascularization. Laser therapy is reserved for high risk ROP, with plus disease and Zone I disease being the most important criteria as defined by the Early Treatment of Retinopathy of Prematurity study. Mild stages of ROP have a high incidence of spontaneous regression without treatment. Laser ablation therapy is given to the avascular retina, not directly to the shunt or neovascularization. If left untreated, thresh old disease is associated with an unfavorable outcome in approximately 45% of cases. Laser therapy has been shown to be more effective and is less invasive than cryotherapy.

Treatment of Cicatricial Retinopathy of Prematurity (Vitreoretinal Surgery)

The surgical management of retinal detachments (stage 4 or 5 ROP) is con troversial. Scleral buckling procedure may be indicated for some stage 4 cases. Stage 5 has an extremely poor prognosis even with modern vitreoretinal techniques, and postoperative visual function is universally poor. The “heroic” vitreoretinal surgery required to repair a stage 5 retinal detachment should be performed only after a full discussion with the parents to establish realistic expectations about the poor prognosis.

Late Complications of Retinopathy of Prematurity

Retinopathy of prematurity holds an increased incidence for myopia, astigmatism, anisometropia, amblyopia, and strabismus. Infants with ROP should have follow up appointments with an ophthalmologist for a full office examination. Late retinal detachment is a potential complication, especially in patients with high myopia.

Differential Diagnosis of Retinopathy of Prematurity

The differential diagnosis of ROP includes persistent hyperplastic primary vitreous (Chapter 22), Norrie disease (Chapter 6), familial exudative vitreo retinopathy (this chapter), incontinentia pigmenti (this chapter), and causes of leukocoria (Chapter 22). The diagnosis of ROP usually is straightforward based on the history of prematurity, oxygen exposure, and characteristic fundus findings. Nonetheless, the following are rare diseases that can be con fused with ROP.

Familial Exudative Vitreoretinopathy

This is an autosomal dominant, inherited peripheral retinopathy that in its early stage looks very similar to ROP. Findings include peripheral neovascu larization, avascular retina, and retinal exudates. The disease may evolve to produce retinal traction, macular dragging, retinal folds, retinal breaks, and retinal detachment.

Incontinentia Pigmenti

Incontinentia pigmenti is an X linked dominant disorder (gestational death in males). Females have linear erythema with bullae and vesicles appear ing over the skin of the torso and extremities within the first 2 weeks of life. Eosinophils in peripheral blood transiently occur, and intraepithelial eosino phils on skin biopsy are diagnostic. Verrucous plaques replace the bullae. Then at 4 to 6 months, a pattern of brown splashes of pigment with jagged borders appears on the torso and extremities. Ocular involvement occurs in 30% of cases and consists of peripheral fibrovascular proliferation and even tually retinal detachment. Treatment with laser or cryotherapy to the periph eral retina may prevent retinal detachment. A dilated fundus examination with the indirect ophthalmoscope is required to document the peripheral retinal findings. Systemic findings are related to ectodermal components including hair, teeth, nails, and the central nervous system. Alopecia (40%), spoon shaped nails (7%), and missing or pegged teeth (80%) are part of the syndrome. Neurologic disorders include mental retardation (30%), seizures, and paralytic motor problems.

Bibliography

1.Tin W, Milligan DW, Pennefather P, Hey E. Pulse oximetry, severe retinopathy, and outcome at one year in babies of less than 28 weeks gestation. Arch Dis Child Fetal Neonatal Ed. 2001;84:F106–F110

2.Chow LC, Wright KW, Sola A, and the CSMC Oxygen Administration Study Group. Can changes in clinical practice decrease the incidence of severe retinopathy of prematurity in very low birth weight infants? Pediatrics. 2003;111:339–345

3.Wright KW, Sami D, Thompson L, Ramanathan R, Joseph R, Farzavandi S. A physiologic reduced oxygen protocol decreases the incidence of threshold retinopathy of prematurity.

Trans Am Ophthalmol Soc. 2006;104:78–84

4.Vanderveen DK, Mansfield TA, Eichenwald EC. Lower oxygen saturation alarm limits decrease the severity of retinopathy of prematurity. J AAPOS. 2006;10:445–448

5.Palmer EA, Flynn JT, Hardy RJ, et al. Incidence and early course of retinopathy of prematu rity. The Cryotherapy for Retinopathy of Prematurity Cooperative Group. Ophthalmology. 1991;98:1628–1640

6.Kinsey VE, Hemphill FM. Etiology of retrolental fibroplasia and preliminary report of cooperative study of retrolental fibroplasia. Trans Am Acad Ophthalmol Otolaryngol. 1955;59:15–24

7.Cryotherapy for Retinopathy of Prematurity Cooperative Group. Multicenter trial of cryo therapy for retinopathy of prematurity. 3 1/2 year outcome—structure and function. Arch Ophthalmol. 1993;111:339–344

8.Deulofeut R, Critz A, Adams Chapman I, Sola A. Avoiding hyperoxia in infants < or = 1250 g is associated with improved short and long term outcomes. J Perinatol. 2006; 26:700–705

9.Good WV, and the Early Treatment for Retinopathy of Prematurity Cooperative Group. Final results of the Early Treatment for Retinopathy of Prematurity (ETROP) randomized trial. Trans Am Ophthalmol Soc. 2004;102:233–248

Chapter 20

Dyslexia and

Learning Disabilities

Dyslexia is difficulty reading. The exact reason some otherwise intelligent children have difficulty reading remains unknown. Characteristics of dyslexia include letter reversals (eg, b and d), word reversals (eg, was and saw), skip ping lines, and mirror writing. One of the hallmarks of dyslexia is poor spell ing, which usually stays with the child throughout life. Dyslexic children have difficulty processing words, but they do not specifically have a problem with visual processing. It is interesting that dyslexic children uniformly are great at video games and have no problem watching television. These children like visual input from movies or television as long as they do not have to read. Understanding that dyslexia is not a vision problem is important because this

helps direct the appropriate treatment. Remember, spelling is not a visual task. Because children with dyslexia often have normal or superior intelligence, teachers and parents often look to visual defects as the cause of poor read ing. In truth, there is no evidence of a relationship between visual abilities and reading problems (Helveston et al; Vellutino). Studies have consistently shown that normal readers and patients with dyslexia have similar incidences of visual defects. This concurs with the author’s clinical experience, noting numerous patients with poor visual function, limited ocular rotations (Duane syndrome), strabismus, and even nystagmus who still have excellent reading skills. On the other hand, the vast majority of children with dyslexia will have absolutely normal ocular examinations.

There are vision therapists who claim that children with dyslexia have an oculomotor deficit that disrupts the normal reading pattern. They go on to rationalize that eye exercises improve ocular coordination, thereby improving reading skills. Much of this thinking comes from early anecdotal publications in the 1950s. In contrast, studies by Goldberg and Schiffman at Johns Hop kins University using electronystagmography clearly demonstrated that ocular coordination and motility are normal in children with dyslexia. Additionally, they showed that the degree of comprehension produces the pattern of ocular movement, not that the innate ocular motility potential determines the degree

of comprehension. That is to say, children who have difficulty comprehending and reading have abnormal fixation and re fixation movements as they read; however, their ocular motility is normal. A patient who can read French flu ently has normal eye motility when reading French; however, the patient has abnormal eye movements when reading English. These and other studies have shown that reading and learning disabilities in children are not caused by a lack of ocular coordination.

In a joint organizational statement, executive committees from the Ameri can Academy of Pediatrics and the American Academy of Ophthalmology have stated that children with learning disabilities have the same incidence of ocular abnormalities as children who are normal achievers and are reading

at grade level. Visual training, eye muscle exercises, and reading therapy with tinted glasses frequently result in unwarranted expense and often misplace resources when they could be better used for reading, education, and tutors

(Metzger et al).

Even though the majority of children with dyslexia will have normal ophthalmologic examinations, they should have a complete eye examination, including dilating drops for a cycloplegic refraction. Convergence insufficiency and hypermetropia are conditions that may interfere with reading and lead to near fatigue and asthenopia, yet are not easily detected by routine screening examinations. Not all children with learning disabilities have pure dyslexia, defined as poor reading skills with normal intellect and appropriate age related behavior. Neuropsychology processes such as attention deficit/hyperactivity disorder, autism, mental retardation, and syndromes such as Williams can cause learning disabilities. A team evaluation by a neuropsychologist, a pedia trician, an educator, and an ophthalmologist is indicated for children with learning disabilities.

Dyslexia is a very difficult problem for children, parents, and teachers. This author is dyslexic and as a child went through the gamut of treatments including vision therapy. It is this author’s belief that commitment to a good reading program is the best treatment. It is not easy for a person with dyslexia to improve reading skills but with hard work, children with dyslexia can learn to read at grade level or better. Dyslexic children are often gifted in areas such as science and math. These children need encouragement, as they often are frustrated with school because of the difficulty with reading. Just because chil dren have difficulty reading does not mean they should be classified as “slow”

and tracked to the back of the class. Many intellectual geniuses were dyslexic including Albert Einstein, Thomas Edison, and General Patton. General Pat ton, suffering from dyslexia, took 5 years to graduate from West Point but rose to become adjutant of the Corps of Cadets (highest honor). It is interesting to this author that he was an excellent marksman, participating in the 1912 Olympics. No, I do not think dyslexics have a problem with visual processing!

Bibliography

1.Goldberg HK. Dyslexia/Learning Disabilities. 2nd ed. Philadelphia, PA: WB Saunders; 1983:1305–1318

2.Helveston EM, Weber JC, Miller K, et al. Visual function and academic performance. Am J Ophthalmol. 1985;99:346–355

3.Metzger RL, Werner DB. Use of visual training for reading disabilities: a review. Pediatrics. 1984;73:824–829

4.Vellutino FR. Dyslexia. Sci Am. 1987;256:34–41