Journal of Pediatric Ophthalmology and Strabismus

OCCLUSION THERAPY FOR SEVERE STRUCTURAL ABNORMALITIES 

Reappraisal of Occlusion Therapy for Severe Structural Abnormalities of the Optic Disc and Macula

Lucy L H Yang, MD; Scott R Lambert, MD

Abstract

ABSTRACT

The visual function of some children with structural defects of the macula or optic nerve has previously been shown to improve with occlusion therapy. The charts of five children, ages 4 to 8 years, who had various types of severe structural abnormalities were reviewed. Two patients had optic nerve hypoplasia; there was one case each of foveal hypoplasia, posterior persistent hyperplastic primary vitreous, and retinopathy of prematurity. All the patients had undergone extensive amblyopia therapy prior to referral.

In three children, occlusion therapy had been initiated and continued intensively for several months or longer without recognizing the presence of a severe, underlying structural abnormality. In none of the five children was there any clear-cut evidence of visual improvement. In some cases, the long period of enforced iatrogenic vision impairment resulted in significant psychosocial harm and developmental delay. In all five cases, it was structural changes rather than amblyopia that ultimately accounted for visual loss.

The authors stress the importance of a meticulous fundus examination directed at finding organic defects prior to patching. Close, periodic monitoring of visual function should then follow. To spare the child unnecessary psychosocial impairment, it is advisable to follow established recommended thresholds for terminating occlusion therapy.

Abstract

ABSTRACT

The visual function of some children with structural defects of the macula or optic nerve has previously been shown to improve with occlusion therapy. The charts of five children, ages 4 to 8 years, who had various types of severe structural abnormalities were reviewed. Two patients had optic nerve hypoplasia; there was one case each of foveal hypoplasia, posterior persistent hyperplastic primary vitreous, and retinopathy of prematurity. All the patients had undergone extensive amblyopia therapy prior to referral.

In three children, occlusion therapy had been initiated and continued intensively for several months or longer without recognizing the presence of a severe, underlying structural abnormality. In none of the five children was there any clear-cut evidence of visual improvement. In some cases, the long period of enforced iatrogenic vision impairment resulted in significant psychosocial harm and developmental delay. In all five cases, it was structural changes rather than amblyopia that ultimately accounted for visual loss.

The authors stress the importance of a meticulous fundus examination directed at finding organic defects prior to patching. Close, periodic monitoring of visual function should then follow. To spare the child unnecessary psychosocial impairment, it is advisable to follow established recommended thresholds for terminating occlusion therapy.

INTRODUCTION

The visual function of some children with structural defects of the macula or optic nerve has previously been shown to improve with occlusion therapy, thereby demonstrating that amblyopia superimposed on organic causes of decreased vision may be successfully treated.1"6 Previous studies on the subject of patching in eyes with structural abnormalities have focused primarily on the potential benefit of improved visual function with little, if any, attention to the possible harmful effects.1'6 This report reappraises the role of occlusion therapy for severe abnormalities of the optic disc and macula. The goal is to foster an increased awareness of the potentially adverse psychosocial consequences of protracted occlusion therapy for presumed coexisting amblyopia, especially when the visual loss is caused by severe structural defects in either the macula or optic nerve.

MATERIALS AND METHODS

The charts of five children who were examined between the ages of 4 and 8 were reviewed. All of the children had severe structural abnormalities of the optic disc or macula and visual loss, which had been previously treated with extensive patching of the better eye. Two patients had optic nerve hypoplasia; there was one case each of foveal hypoplasia, posterior persistent hyperplastic primary vitreous (PHPV), and retinopathy of prematurity (ROP). The structural abnormality was unilateral except in the child with ROP in whom there was asymmetric bilateral involvement. All five patients had been treated for amblyopia with full-time or part-time patching alone or patching combined with a refractive correction. Three of the five received penalization therapy with atropine eye drops. Ages at onset and cessation of treatment were noted. Past patching compliance was assessed by history as given by the parents. Initial, best, and final visual acuities were recorded.

Complete ophthalmological evaluations were performed on all the children. Monocular visual acuity was measured using Alien pictures or Snellen letters at 20 feet. Motility was assessed by cover-uncover testing when possible; otherwise Krimsky or Hirschberg testing was used. All patients underwent pupillary, slit lamp, and dilated funduscopic examinations. Refractions were done with two doses of 1% cyclopentolatc and 2.5% phenylephrine hydrochloride (Neo-synephrine).

FIGURE 1: Case 1. Left fundus showing foveal hypoplasia.

FIGURE 1: Case 1. Left fundus showing foveal hypoplasia.

RESULTS

Strabismus was present in all five patients, anisometropia was present in two patients, and two patients had afferent pupillary defects. The duration of patching had a mean of 24.8 months and a range of 5 to 44 months.

In three children (Cases 1, 4, and 5), the referral diagnosis had to be revised. In these cases, occlusion therapy for presumed amblyopia had been initiated and continued for several months or longer without recognizing the presence of a severe, underlying structural abnormality. In none of these children was there ever any clear-cut, objective visual improvement. In the two cases in which the specific structural defects were known, intensive patching for suspected, concurrent functional visual deficit was continued for years with no evidence of any visual rehabilitation. In some cases, the long period of enforced iatrogenic vision impairment resulted in significant psychosocial harm and developmental delay. In all five cases it was structural changes rather than amblyopia that ultimately accounted for visual loss.

CASE REPORTS

Case 1. A girl, 6 years 8 months of age, was referred for a second opinion regarding patching therapy for the left eye. The right eye had been patched since age 4 for presumed strabismic amblyopia. Birth and development had been entirely normal. Her visual acuity prior to patehing was 20/30 in the right eye and 20/200 in the left eye. Vessels, maculae, and discs were described as normal in both eyes.

Patching had been poorly tolerated, but was consistently enforced by the mother. When the patient was almost 5 years of age, the family relocated. The ophthalmologist who took over her care diagnosed congenital right superior oblique palsy for which the patient underwent a recession of the right inferior oblique followed by a recession of the left inferior rectus. At the time, visual acuity remained 20/30 in the right eye and 20/200 in the Jeft eye, CyclopJegic refraction was + 0.25 on the right and piano on the left. The fundus exam was again described as normal in both eyes. She continued to receive full-time occlusion of the right eye. Best-recorded visual acuity in the left eye was 20/80 on one visit after the operation.

For the mother, compliance was a constant battle. Tb prevent her daughter from peeking, she resorted on many occasions to bandaging the whole head like a mummy's, leaving only a small opening for the left eye. While patched, the patient would be in tears, complain of headaches, bump into things, and refuse to watch television. She became withdrawn and easily discouraged. The mother continued to enforce the treatment despite her daughter's protestations. She recalls her daughter's failure to improve visit after visit to the doctor, and how she would blame herself and leave the office in tears. Then a year later, when the patient was 6 fe-years-old, the mother was told that the vision in the left eye was not going to improve. Hoping for another treatment option, she decided to seek a second opinion.

At the time of examination the child, 6 years 8 months of age, had been patched for 32 months. Her visual acuity with linear Snellen letters was 20/20 in the right eye and was still 20/200 in the left eye. Cycloplegic refraction was + 0.50 in each eye. A small incomitant right hypeitropia was present at distance and near. There was no nystagmus. Pupillary responses were normal, as were the anterior segments. The right fundus was normal. The left fundus, however, showed fcweaJ bypopJasia (Fig IA JDuorescein angiography confirmed the diagnosis (Fig 2). Occlusion treatment was discontinued at this time.

Four months later, the mother recounted how sorry she had felt for her daughter during this time and related how much she had disliked her role as enforcer. She described the enormous sense of relief she had felt when patching was finally terminated.

Case 2. A boy, 4 years 8 months of age, with ROP was referred for a second opinion regarding patching therapy for the left eye that was begun when he was 12 months old. The right eye had been patched part-time, alternating the patch with atropine penalization, for 3 years and full-time for the past 8 months. He had never tolerated the occlusion therapy well. The patient was a twin, delivered after a 29 week gestation with a birth weight of 720 g. His brother, whose birth weight had been 1273 g, had no eye problems.

His best-corrected visual acuity was 20/200 in the right eye with Aiien cards and counting fingers at 3 feet in the left eye. He was wearing a refractive correction of -14.00 + 2.25 X 05° in the right eye and -7.25 + 2.75 X 125° in the left eye. Overrefraction was the same. A 20 prism diopter left hypertropia was present at distance and near. Both a manifest and latent nystagmus were present. The pupillary responses and anterior segments were normal. Fundus exam revealed moderate macular ectopia in the right eye and severe macular ectopia in the left eye with almost complete straightening of the temporal retinal vessels (Fig 3).

FIGURE 2: Cose 1. (A) Right fundus. (B) Left fundus. Fluorescein angiogrophy, red-free photographs showing lack of macula luteal pigment in the left eye as compared to the right. (C) Fluorescein angiogram of left fundus. Note distortion, irregularity, and small size of foveal avascular zone. There is mottled hyperfluorescence where the fovea should be.

FIGURE 2: Cose 1. (A) Right fundus. (B) Left fundus. Fluorescein angiogrophy, red-free photographs showing lack of macula luteal pigment in the left eye as compared to the right. (C) Fluorescein angiogram of left fundus. Note distortion, irregularity, and small size of foveal avascular zone. There is mottled hyperfluorescence where the fovea should be.

The parents described a bright and bubbly 4-year-old, who liked his glasses so much as to ask for them first thing each morning. In contrast, he did not like wearing the patch at all. He would say, "Please don't put it on." Once patched, hie whole personality underwent a transformation. He would sit down, suck his thumb, and ask for his blanket. He refused to play, became easily discouraged, and appeared depressed. The patching regime involved aü waking hours except for time spent hi school. He was having difficulty in preschool. He was very far behind, especially in coloring and writing, and could not maintain more than a short-lived interest hi any visual activity. When compared to his twin, who had no visual problems, he was lagging both developmentally and socially. Developmental milestones, especially gross motor and fine motor skills, were delayed about a year. Because the decreased visual acuity in the left eye was believed to be primarily related to structural changes rather than to amblyopia, and because of psychosocial and developmental problems, occlusion therapy was discontinued. At that time, he had undergone a total of 44 months of treatment.

One year later, the mother reported that her son had improved so significantly in his language skills that he was now almost on par with his classmates. Visual acuity in the left eye remained counting fingers. Recalling the trials of many months of occlusion therapy, the mother confided that there were times when she had serious doubts about patching, but had pushed aside her feelings because she felt it was her duty to cany out the doctor's orders. She says that the hardest thing for her was when she would take off the patch each evening and her son would say, "Thank you, Mommy, I can see now"

The remaining three cases are summarized in the Table.

DISCUSSION

Most authors who have evaluated occlusion therapy in children with organic pathology advocate a trial of patching in eyes with structural abnormalities, including eyes with severe defects of the macula and disc.1,3,4-6-7 When amblyopia is superimposed on a structural abnormality, patching may result in a significant improvement in visual acuity in some cases. Often, however, it is impossible to determine which eyes are likely to benefit from amblyopia treatment.1'6 For one thing, there are no uniformly reliable, objective methods for detecting the presence of concurrent amblyopia in eyes with structural abnormalities. This is especially true for lesions of the optic disc and macula. While the crowding phenomenon8 and absence of further reduction in visual acuity with neutral density filters9 may both suggest the presence of amblyopia in a wide variety of organic ocular abnormalities,3'4 these tests have not proven to be as consistently helpful in detecting amblyopia in eyes with coexisting optic disc or macular abnormalities.4 Pupillary responses and visual evoked potentials also have been shown to have limited usefulness.4 Moreover, it is acknowledged that in eyes with macular or optic disc defects, the degree of abnormality perceived by the examiner does not necessarily correlate with the eye's visual potential.1,4,6,10 For example, it has been observed that even central acuity can be spared despite a fundus appearance of striking optic nerve hypoplasia.1,10 It is likewise difficult to estimate accurately visual prognosis in patients with macular pathology,5'6 and cases have been reported where better vision was achieved with patching than was originally anticipated based on appearance alone.6

Table

TABLEPatient Data

TABLE

Patient Data

FIGURE 3: Case 2. (A) Bight fundus showing moderate macular ectopia. (B) Left fundas showing severe macular ectopia. Note almost complete straightening of temporal retinal vessels.

FIGURE 3: Case 2. (A) Bight fundus showing moderate macular ectopia. (B) Left fundas showing severe macular ectopia. Note almost complete straightening of temporal retinal vessels.

It is precisely the inadequacy of reliable objective tests for amblyopia and the absence of sure prognostic signs for visual rehabilitation that furnish both the rationale and incentive for initiating trials of occlusion therapy in eyes with severe organic causes of decreased vision. In some cases, only a successful trial of occlusion therapy can confirm the presence of a coexisting amblyopia.4,6,8 In the five cases reported here, patching for presumed concurrent amblyopia was unsuccessful inasmuch as structural defects rather than amblyopia accounted for the children's visual loss. The importance of a meticulous fundus exam directed at finding structural defects prior to patching must be stressed. In three of the children (Cases 1, 4, and 5), earlier recognition of organic pathology might have resulted in a less protracted course of patching. Although there are no perfect patching protocols, most clinicians believe that frequent visits at regular intervals, based on the age of the patient, are necessary to monitor the patient's sound and amblyopic eyes during treatment.6,8 Within this framework, modifications and allowances can be made for individual situations. Likewise, various protocols have been set forth for terminating amblyopia treatment. For example, it has been advocated that occlusion therapy be discontinued after equal visual acuity is attained in the amblyopic eye, or after three consecutive, compliant episodes of full-time occlusion without further visual improvement.6'11 When the decreased visual acuity is primarily related to structural changes rather than to amblyopia, it is advisable to follow established recommended thresholds for terminating occlusion therapy both to spare the child and family months or even years of fruitless patching, and more importantly, to spare the child unnecessary psychosocial impairment.

In retrospect, the uniformly poor outcome in the five children reported here naturally raises the question of whether the better option would have been to have withheld amblyopia treatment in the first place. This may be the preferred course of action in select children with severe structural abnormalities of the optic disc or macula. Candidates for exclusion might include patients with excellent vision in the sound eye contrasteda with severe, unilateral involvement of the optic nerve or macula accompanied by very poor initial or baseline visual function in the defective eye (exemplified by Cases 1, 3, 4, and 5). Even in the best of circumstances, one could reasonably expect patching to only partly bridge the visual gap between the two eyes. Insofar as the sound eye would continue to be used exclusively for seeing, the defective eye would serve at most as a back-up. Also to be considered for exclusion might be patients with bilateral though asymmetric involvement, especially in cases where the better eye also sees poorly (exemplified by Case 2). In this situation, the child may already be functioning at the outer limit of useful vision and barely be coping as it is. To impose further visual handicap might risk psychic damage. One could argue, in general, for withholding patching in patients whose emotional vulnerability would seem to place them at risk for developing psychosocial problems brought about by the demands of the therapy. Finally, one might withhold patching in patients with severe optic disc or macula defects for whom a trial of occlusion is being considered simply because no other treatment alternative exists. Where patching and all its attendant demands are concerned, to do something may not always be better than to do nothing. One must always keep in mind that the sensitive period for patching happens to coincide with critical stages of cognitive, psychosocial, and physical development in the child, and that any attempts to rehabilitate the eye must not interfere with the greater development of the whole child.

REFERENCES

1. Gardner HB, Irvine AR. Optic nerve hypoplasia with good visual acuity. Anh Ophtkalmol. 1972;88:255-258.

2. Scott WE, Stratton VB, Fabre J. Pull-time occlusion therapy for amblyopia. American Orthoptic Journal. 1980 ;30: 125 -130.

3. Kushner BJ. Functional amblyopia associated with organic ocular disease. Am J Ophthalmol. 1981 ;9 1:39-45.

4. Kushner BJ. Functional amblyopia associated with abnormalities of the optic nerve. Arch Ophthalmol. 1984; 102: 683-685.

5. Summers CG, Romig L, Lavoie JD. Unexpected good results after therapy for anisometropic amblyopia associated with unilateral peripapillary myelinated nerve fibers. J Pediatr Ophthalmol Strabismus. 1991 i28:134-136.

6. Bradford GM, Kutachke PJ, Scott WE. Results of amblyopia therapy in eyes with unilateral structural abnormalities. Ophthalmology. 1992;99: 1616-1621.

7. Kushner BJ. Functional amblyopia: a purely practical pediatrie patching protocol. In: Reinecke RD, ed. Ophthalmology Annual 1988. New York, NY: Raven Press; 1988:173-198.

8. Stuart JA, Burian HM. A study of separation difficulty. Its relationship to visual acuity in normal and amblyopic eyes. Am J Ophthalmol. 1962;53:471-477.

9. von Noorden GK, Burian HM. Visual acuity in normal and amblyopic patients under reduced illumination, 1. Behavior of visual acuity with and without neutral density filter. Arch Ophthalmol. 1959;6 1:533-535.

10. Bjork A, Laurell CG, Laurell U. Bilateral optic nerve hypoplasia with normal visual acuity. Am J Ophthalmol. 1 9 78 ;86: 524-529.

11. Kutschke PJ, Scott WE, Keech RV. Anisometropic amblyopia. Ophthalmology. 1991;98:258-263.

TABLE

Patient Data

10.3928/0191-3913-19950101-09

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