Anisometropic Amblyopia PAMELA J. KUTSCHKE, CO, WILLIAM E. SCOTT, MD, RONALD V. KEECH, MD
Abstract: One hundred twenty-four patients with anisometropia of 1 diopter or greater and amblyopia were reviewed as to the type and amount of anisometropia, whether or not they had consulted with an ophthalmologist, visual acuity before and after treatment, and type of treatment. The patient population was divided into five groups according to the type of anisometropia. Eighty-two percent of all patients reached a visual acuity of 20/40 or better. Eighteen percent of all patients reached a visual acuity of 20/20. The best visual acuity obtained was not found to be related to the degree of anisometropia or the age at which treatment was begun. Patients with myopic and compound myopic astigmatism/mixed astigmatism anisometropia had poorer visual outcomes. There was a strong positive correlation between the initial visual acuity and the best visual acuity obtained (P = 0.0001). Ophthalmology 1991; 98:258-263
Anisometropia, or the difference in the refractive error between the two eyes of an individual, is a well known cause of amblyopia. Anisometropic amblyopia may go undetected until late in childhood as many patients do not have strabismus or other apparent signs of an eye problem thus presenting a difficult treatment problem for the ophthalmologist Anisometropic amblyopia has been evaluated in numerous studies_ Most of these reports have emphasized the type ofrefractive error l - 7 or the rate of incidence 8- 11 with little attention to treatment To our knowledge, no previous study has included all types of anisometropic amblyopia with and without strabismus and discussed treatment and results_ The purpose of this study was to examine the patient characteristics influencing the treatment outcome of a large population of people with anisometropic amblyopia.
MATERIALS AND METHODS Over two thousand charts of amblyopic patients seen at the University of Iowa Pediatric Ophthalmology clinic between 1970 and 1988 were retrospectively reviewed. All patients included in the study had amblyopia and anisometropia with or without strabismus. Anisometropia
Originally received: September 27, 1989. Revision accepted: July 19, 1990. From the Department of Ophthalmology, The University of Iowa Hospitals & Clinics, Iowa City, IA. Reprint requests to Pamela J. Kutschke, CO, The University of Iowa, Department of Ophthalmology, Iowa City, IA 52242.
258
was defined as a difference in refractive error of 1_00 D or greater of sphere or cylinder. Anisometropia in the compound hyperopic and compound myopic/mixed astigmatism groups was defined as a difference in both the sphere and cylinder ofO. 75 D or greater. Only patients whose treatment was followed at the University of Iowa for at least 2 months were included_ Patients with possibly organic causes of amblyopia were excluded. All significant refractive errors were corrected based on cycloplegic refraction prior to the assessment of vision, when possible, and ocular alignment. Cycloplegic refractions were performed by instilling two drops of 1.0% cyclopentolate hydrochloride in each eye five minutes apart. Refractions were repeated on later examinations until retinoscopic findings agreed within 0.5 D. Retinoscopy was performed yearly. Monocular visual acuity was measured using the Snellen letter, illiterate E, or Allen picture chart at 20 feet. Amblyopia was defined as a difference in vision of two lines or greater with the acuity of the amblyopic eye being less than 20/40. Vision in preverbal children was evaluated by the fixation pattern technique with or without an inducing prism. These tests are similar to those described by Zipfl2 and Wright l3 and were in use at the University of Iowa prior to their published description. Amblyopia was defined as the inability to hold fixation through a blink with either test All patients studied were amblyopic in the eye with the greatest refractive error. Treatment consisted of full time occlusion using adhesive patches worn 24 hrs/day or all waking hours. This was discontinued after equal visual acuity was obtained or after three consecutive, compliant episodes of FTO without further increase in vision. Part time occlusion of 4 to 8 hrs/day was instituted to maintain the level of visual acuity attained in the amblyopic eye. Some patients with-
KUTSCHKE et al
•
ANISOMETROPIC AMBLYOPIA
Table 1. Patient Population
RESULTS
No. of Patients Type of Anisometropia
Strabismic
Non-strabismic
Total (%)
Myopia Hyperopia Astigmatism Compound myopic astigmatism/mixed astigmatism Compound hyperopic astigmatism
13 9 12
10 33 13
23 (18.5) 42 (33.8) 25 (20.2)
9
9
18 (14.5)
6
10
16 (12.9)
49 (40)
75 (60)
124 (100.0)
Total (%)
Table 2. Refraction Type
Mean
(range)
Myopia (0) Hyperopia (0) Astigmatism (0)
-8.05 +2.46 +1.96
(-2.00 to -22.00) (+0.75 to +5.25) (+1.00 to +4.75)
o = diopters. Table 3. Type of Treatment No. of Patients
Type Myopia Hyperopia Astigmatism Compound astigmatism myopic astigmatism/ mixed astigmatism Compound hyperopic astigmatism Total (%)
Glasses Only
Glasses, then Patch
Glasses and Patch Simultaneously
0 4 4
5 7 6
18 31 15
4
4
10
2
13
24 (19.2)
87 (70.2)
13 (10.4)
out strabismus were given their refractive correction without patching for six weeks. If vision improved, they continued without patching and were followed to monitor visual acuity. Full time occlusion was prescribed if vision did not improve. Patients were divided into strabismic and nonstrabismic groups. Strabismic patients had manifest deviations with glasses by prism cover test on an accommodative target. Patients with fully accommodative esotropia are listed in the nonstrabismic group. Patient records were reviewed as to the type and amount of anisometropia, presentation, age at onset of treatment, laterality, initial, best and final visual acuity, sensory status, motility, and type and duration of treatment.
Of the over 2,000 charts of amblyopic patients reviewed, 264 patients were identified as having anisometropia. One hundred twenty-four patients had anisometropic amblyopia and met inclusion criteria. These are divided by type of anisometropia into five groups and subdivided into strabismic and nonstrabismic groups in Table 1. The compound myopic/mixed astigmatism (CMA/MA) group consisted of 16 CMA patients and 2 mixed astigmatism patients. These two patients did not appear clinically different from the rest of the group. Fifty-one patients (41 %) were amblyopic in the right eye and 73 (59%) were amblyopic of the left. The difference in the refraction of the two eyes of each patient determined the amount of anisometropia. The mean amount and ranges of anisometropia for the myopia, hyperopia, and astigmatism groups are listed in Table 2. In the astigmatism and compound/mixed astigmatism groups, refractive error was determined in plus cylinder form. Mean refractive errors were not determined for the compound myopic/mixed and hyperopic astigmatism groups as spherical equivalents did not adequately represent the amount of anisometropia. Presenting complaints of these patients varied. Fiftyone patients (41 %) presented because strabismus was noted. Twenty-one patients (17%) were referred by another physician for amblyopia treatment. Thirty-five patients (28%) were referred after failing their school screening eye examination. Seventeen patients (14%) were seen for various reasons including limbal dermoid, positive family history of strabismus, amblyopia or refractive error, child abuse, or routine examination. Thirty-eight percent had prior treatment elsewhere consisting of either patching without refractive correction (10%), refractive correction alone (10%), or refractive correction combined with patching (18%). Treatment at the University of Iowa was determined by the patient's alignment, amount of anisometropia, age, and previous treatment (Table 3). Previously treated and strabismic patients were prescribed anisometropic refractive correction and full time occlusion simultaneously. Thirty patients were prescribed FTO simultaneously with their refractive correction although they had no prior treatment or strabismus. These included very young patients with only a 'fixation pattern visual assessment and some older patients with amblyopic vision of 20/200 or less. The ranges and means of the duration of full time occlusion needed to reach the best visual acuity are listed in Table 4. The longest time needed to reach best visual acuity was 48 months with an average of 6.4 months. Neither the initial visual acuity, nor the degree of anisometropia were related to the duration of occlusion therapy needed to reach the best visual acuity using the Kendall's Tau test (P = 0.1668) and ANOV A test (P = 0.2158 to 0.5975) respectively. 259
OPHTHALMOLOGY
•
FEBRUARY 1991
•
VOLUME 98
Maximum Visual Acuity (n = 104)*
Type Myopia Hyperopia Astigmatism Compound myopic astigmatism/mixed astigmatism Compound hyperopic astigmatism Total * Thirteen
acuity.
No. of Patients
Mean
(range)
21 38 20
8.5 4.9 5.1
(0.5-33) (1-20) (1-12)
11
8.5
(1.5-48)
14
7.6
(3-20)
104
6.4
(0.5-48)
patients were never patched. Seven did not increase visual
The age at onset of treatment at the University ofIowa was examined for its effect on the initial visual acuity, the best visual acuity achieved and the duration of occlusion (Tables 5 and 6). Age range was 11 months to 111 months. No relationship was found between any of these parameters by Kendall's Tau test (P = 0.2829, P = 0.6548 and P = 0.9373, respectively). Stability of the visual result can be seen in Table 7. Sixty-six of 124 patients completed all occlusion therapy (i.e., full and part time occlusion). Fifty patients remained stable while sixteen patients (24.2%) slipped two or more lines of visual acuity after cessation of occlusion therapy. Full time occlusion was reinstituted in seven of these with a return to prior visual acuity. Nine patients did not have further occlusion due to either noncompliance or age. Patching was discontinued in all 66 patients at a mean age of 7.04 years. The mean time elapsed since patching was 37.9 months, with a range of 1 to 138 months. Fortyfive patients are still patching. The remaining 13 patients never required occlusion therapy. One patient developed strabismus after occlusion therapy. A 6 1h-year-old child with anisometropic hyperopia with no history of strabismus developed a constant 30'" esotropia. This occurred after a single noncompliant episode of part time occlusion was associated with a decrease in visual acuity to 20/50 in the amblyopic eye. Seven and one half months of prior full time occlusion and refractive correction resulted in visual acuity of 20/20 in the right eye and 20/30+ in the left. Full time occlusion was instituted to regain visual acuity. The deviation was stable for three months. She was prism adapted 14 and surgically corrected. Prior to developing strabismus, the patient fused at near on the Worth four dot with a questionable response at distance and had 100 seconds of arc of stereopsis on the Titmus test. While strabismic, the patient demonstrated uncrossed diplopia on the near Worth four dot. Six months postoperatively, she was orthophoric with fix260
NUMBER 2
Table 5. Age at Onset of Treatment versus Best Visual Acuity in 124 Patients
Table 4. Duration of Occlusion and Range
Duration of Occlusion (mos)
•
Visual Acuity
No. of Patients
Age at Onset of Treatment (mos)
Initial (mean Snellen)
Best (mean Snellen)
6 27 61 21 9
0-24 25-48 49-72 73-96 >96
20/200 20/182 20/135 20/128 20/156
20/36 20/36 20/30 20/32 20/37
Table 6. Age at Onset of Treatment versus Duration of Occlusion Maximum Visual Acuity (n = 104)* No. of Patients
Age at Onset of Treatment (mos)
Mean Duration of Occlusion (mos)
5 21 52 18 8
0-24 25-48 49-72 73-96 >96
9.7 8.2
5.7
6.1 4.9
* Thirteen patients were never patched; seven did not increase visual acuity.
Table 7. Patching Results No. of Patients (%) Type Myopia Hyperopia Astigmatism Compound myopic astigmatism/mixed astigmatism Compound hyperopic astigmatism Total
No. of Patients
Slipped :2::2 Lines after Stopping Patch
Still Patching
Never Patched
3/13 (23.1) 0/21 (0) 0/16 (0)
10 17 5
0 4 4
5/9 (55)
5
4
1/7 (14.3)
8
9/66 (13.6)
45
13
ation on a distance and near target and her fusional status was equal to that found before the onset of esotropia. The mean ages of the patients at the onset of treatment at the University ofIowa were calculated for each type of anisometropia (Table 8). The means for each group were not significantly different. The age at treatment onset related to the reason for presentation was calculated. Patients presenting due to strabismus began treatment earlier (4.01 years) than those who presented due to failure ofschool screening examinations (5.70 years) or amblyopia (5.83 years). Initial, final, and best achieved visual acuities were recorded for each patient. Statistical analysis was performed
KUTSCHKE et al
•
ANISOMETROPIC AMBLYOPIA
Table 8. Age at Onset of Treatment Patients with Prior Treatment
Patients without Prior Treatment
Type
No.
Mean (yrs)
(range, mos)
No.
Mean (yrs)
(range, mos)
Myopia Hyperopia Astigmatism Compound myopic astigmatism/mixed astigmatism Compound hyperopic astigmatism
8 15 9
5.45 5.90 5.28
(20-102) (44-101) (39-96)
15 27 16
3.28 5.10 5.10
(14-66) (15-97) (11-110)
7 9
4 2. 6 5.66
(44-72) (43-107)
11 7
4.99 6.83
(27-91) (40-111)
Total
48
5.42
(20-107)
76
4.88
(11 -111)
:
Table 9. Mean Visual Acuity Results Mean Snellen Visual Acuity Type
Initial
Best
Myopia Hyperopia Astigmatism Compound myopic astigmatism/mixed astigmatism Compound hyperopic astigmatism
20/200 20/136 20/81
20/40 20/26 20/27
20/220 20/187
20/56 20/33
Total
20/147
20/32
by transposing the Snellen visual acuity to the logarithm of the minimal angle of resolution (LogMAR) visual acuity.15 The mean initial and best visual acuities for the five types of anisometropia are listed in Table 9. The best achieved visual acuity for all groups combined was significantly related to the initial visual acuity by the Spearman's correlation test (P = 0.0001). Six patients who began with counts fingers vision in their amblyopic eye, however, regained vision to 20/40 or better. Neither the best nor the initial visual acuity was related to the alignment of the patient. Patients with strabismus had a mean initial visual acuity of20/124 and a mean best visual acuity of 20/37, while non strabismic patients had a mean initial visual acuity of20/137 and a mean best visual acuity of 20/30. The relationships between the degree of an-
isometropia and the initial vision and best vision achieved were examined for the myopia, hyperopia, and astigmatism groups. The initial and best visual acuities were not related to the degree of anisometropia using the ANOV A test. Visual outcome was not related to the presence or absence of prior treatment elsewhere. Visual results as related to the type of treatment are listed in Table 10. Twenty-seven non-strabismic patients were given the opportunity to improve visual acuity without patching. Of these, 11 (41 %) obtained good vision with glasses alone. Sixteen needed patching as well as glasses to improve vision. Forty-eight non-strabismic patients were simultaneously prescribed patching and glasses. Thirty of these had had no previous therapy. Forty attained 20/40 or better visual acuity. Two strabismic patients attained a visual acuity of 20/40 or better with glasses alone. One of these patients had intermittent exotropia and the other was a monofixator following esotropia surgery. One hundred three (83.1 %) patients obtained a visual acuity of20/40 or better after amblyopia therapy. Of these, 34 (27.4%) reached a level of 20/20. Further breakdown of vision results 20/40 or better are listed in Table 11. Fourteen (11.3%) achieved visual acuity between 20/50 and 20/80. Seven patients (5.6%) showed no increase in visual acuity after amblyopia therapy and are listed in the
Abstract: One hundred twenty-four patients with anisometropia of 1 diopter or greater and amblyopia were reviewed as to the type and amount of anisometropia, whether or not they had consulted with an ophthalmologist, visual acuity before and after treatment, and type of treatment. The patient population was divided into five groups according to the type of anisometropia. Eighty-two percent of all patients reached a visual acuity of 20/40 or better. Eighteen percent of all patients reached a visual acuity of 20/20. The best visual acuity obtained was not found to be related to the degree of anisometropia or the age at which treatment was begun. Patients with myopic and compound myopic astigmatism/mixed astigmatism anisometropia had poorer visual outcomes. There was a strong positive correlation between the initial visual acuity and the best visual acuity obtained (P = 0.0001). Ophthalmology 1991; 98:258-263
Anisometropia, or the difference in the refractive error between the two eyes of an individual, is a well known cause of amblyopia. Anisometropic amblyopia may go undetected until late in childhood as many patients do not have strabismus or other apparent signs of an eye problem thus presenting a difficult treatment problem for the ophthalmologist Anisometropic amblyopia has been evaluated in numerous studies_ Most of these reports have emphasized the type ofrefractive error l - 7 or the rate of incidence 8- 11 with little attention to treatment To our knowledge, no previous study has included all types of anisometropic amblyopia with and without strabismus and discussed treatment and results_ The purpose of this study was to examine the patient characteristics influencing the treatment outcome of a large population of people with anisometropic amblyopia.
MATERIALS AND METHODS Over two thousand charts of amblyopic patients seen at the University of Iowa Pediatric Ophthalmology clinic between 1970 and 1988 were retrospectively reviewed. All patients included in the study had amblyopia and anisometropia with or without strabismus. Anisometropia
Originally received: September 27, 1989. Revision accepted: July 19, 1990. From the Department of Ophthalmology, The University of Iowa Hospitals & Clinics, Iowa City, IA. Reprint requests to Pamela J. Kutschke, CO, The University of Iowa, Department of Ophthalmology, Iowa City, IA 52242.
258
was defined as a difference in refractive error of 1_00 D or greater of sphere or cylinder. Anisometropia in the compound hyperopic and compound myopic/mixed astigmatism groups was defined as a difference in both the sphere and cylinder ofO. 75 D or greater. Only patients whose treatment was followed at the University of Iowa for at least 2 months were included_ Patients with possibly organic causes of amblyopia were excluded. All significant refractive errors were corrected based on cycloplegic refraction prior to the assessment of vision, when possible, and ocular alignment. Cycloplegic refractions were performed by instilling two drops of 1.0% cyclopentolate hydrochloride in each eye five minutes apart. Refractions were repeated on later examinations until retinoscopic findings agreed within 0.5 D. Retinoscopy was performed yearly. Monocular visual acuity was measured using the Snellen letter, illiterate E, or Allen picture chart at 20 feet. Amblyopia was defined as a difference in vision of two lines or greater with the acuity of the amblyopic eye being less than 20/40. Vision in preverbal children was evaluated by the fixation pattern technique with or without an inducing prism. These tests are similar to those described by Zipfl2 and Wright l3 and were in use at the University of Iowa prior to their published description. Amblyopia was defined as the inability to hold fixation through a blink with either test All patients studied were amblyopic in the eye with the greatest refractive error. Treatment consisted of full time occlusion using adhesive patches worn 24 hrs/day or all waking hours. This was discontinued after equal visual acuity was obtained or after three consecutive, compliant episodes of FTO without further increase in vision. Part time occlusion of 4 to 8 hrs/day was instituted to maintain the level of visual acuity attained in the amblyopic eye. Some patients with-
KUTSCHKE et al
•
ANISOMETROPIC AMBLYOPIA
Table 1. Patient Population
RESULTS
No. of Patients Type of Anisometropia
Strabismic
Non-strabismic
Total (%)
Myopia Hyperopia Astigmatism Compound myopic astigmatism/mixed astigmatism Compound hyperopic astigmatism
13 9 12
10 33 13
23 (18.5) 42 (33.8) 25 (20.2)
9
9
18 (14.5)
6
10
16 (12.9)
49 (40)
75 (60)
124 (100.0)
Total (%)
Table 2. Refraction Type
Mean
(range)
Myopia (0) Hyperopia (0) Astigmatism (0)
-8.05 +2.46 +1.96
(-2.00 to -22.00) (+0.75 to +5.25) (+1.00 to +4.75)
o = diopters. Table 3. Type of Treatment No. of Patients
Type Myopia Hyperopia Astigmatism Compound astigmatism myopic astigmatism/ mixed astigmatism Compound hyperopic astigmatism Total (%)
Glasses Only
Glasses, then Patch
Glasses and Patch Simultaneously
0 4 4
5 7 6
18 31 15
4
4
10
2
13
24 (19.2)
87 (70.2)
13 (10.4)
out strabismus were given their refractive correction without patching for six weeks. If vision improved, they continued without patching and were followed to monitor visual acuity. Full time occlusion was prescribed if vision did not improve. Patients were divided into strabismic and nonstrabismic groups. Strabismic patients had manifest deviations with glasses by prism cover test on an accommodative target. Patients with fully accommodative esotropia are listed in the nonstrabismic group. Patient records were reviewed as to the type and amount of anisometropia, presentation, age at onset of treatment, laterality, initial, best and final visual acuity, sensory status, motility, and type and duration of treatment.
Of the over 2,000 charts of amblyopic patients reviewed, 264 patients were identified as having anisometropia. One hundred twenty-four patients had anisometropic amblyopia and met inclusion criteria. These are divided by type of anisometropia into five groups and subdivided into strabismic and nonstrabismic groups in Table 1. The compound myopic/mixed astigmatism (CMA/MA) group consisted of 16 CMA patients and 2 mixed astigmatism patients. These two patients did not appear clinically different from the rest of the group. Fifty-one patients (41 %) were amblyopic in the right eye and 73 (59%) were amblyopic of the left. The difference in the refraction of the two eyes of each patient determined the amount of anisometropia. The mean amount and ranges of anisometropia for the myopia, hyperopia, and astigmatism groups are listed in Table 2. In the astigmatism and compound/mixed astigmatism groups, refractive error was determined in plus cylinder form. Mean refractive errors were not determined for the compound myopic/mixed and hyperopic astigmatism groups as spherical equivalents did not adequately represent the amount of anisometropia. Presenting complaints of these patients varied. Fiftyone patients (41 %) presented because strabismus was noted. Twenty-one patients (17%) were referred by another physician for amblyopia treatment. Thirty-five patients (28%) were referred after failing their school screening eye examination. Seventeen patients (14%) were seen for various reasons including limbal dermoid, positive family history of strabismus, amblyopia or refractive error, child abuse, or routine examination. Thirty-eight percent had prior treatment elsewhere consisting of either patching without refractive correction (10%), refractive correction alone (10%), or refractive correction combined with patching (18%). Treatment at the University of Iowa was determined by the patient's alignment, amount of anisometropia, age, and previous treatment (Table 3). Previously treated and strabismic patients were prescribed anisometropic refractive correction and full time occlusion simultaneously. Thirty patients were prescribed FTO simultaneously with their refractive correction although they had no prior treatment or strabismus. These included very young patients with only a 'fixation pattern visual assessment and some older patients with amblyopic vision of 20/200 or less. The ranges and means of the duration of full time occlusion needed to reach the best visual acuity are listed in Table 4. The longest time needed to reach best visual acuity was 48 months with an average of 6.4 months. Neither the initial visual acuity, nor the degree of anisometropia were related to the duration of occlusion therapy needed to reach the best visual acuity using the Kendall's Tau test (P = 0.1668) and ANOV A test (P = 0.2158 to 0.5975) respectively. 259
OPHTHALMOLOGY
•
FEBRUARY 1991
•
VOLUME 98
Maximum Visual Acuity (n = 104)*
Type Myopia Hyperopia Astigmatism Compound myopic astigmatism/mixed astigmatism Compound hyperopic astigmatism Total * Thirteen
acuity.
No. of Patients
Mean
(range)
21 38 20
8.5 4.9 5.1
(0.5-33) (1-20) (1-12)
11
8.5
(1.5-48)
14
7.6
(3-20)
104
6.4
(0.5-48)
patients were never patched. Seven did not increase visual
The age at onset of treatment at the University ofIowa was examined for its effect on the initial visual acuity, the best visual acuity achieved and the duration of occlusion (Tables 5 and 6). Age range was 11 months to 111 months. No relationship was found between any of these parameters by Kendall's Tau test (P = 0.2829, P = 0.6548 and P = 0.9373, respectively). Stability of the visual result can be seen in Table 7. Sixty-six of 124 patients completed all occlusion therapy (i.e., full and part time occlusion). Fifty patients remained stable while sixteen patients (24.2%) slipped two or more lines of visual acuity after cessation of occlusion therapy. Full time occlusion was reinstituted in seven of these with a return to prior visual acuity. Nine patients did not have further occlusion due to either noncompliance or age. Patching was discontinued in all 66 patients at a mean age of 7.04 years. The mean time elapsed since patching was 37.9 months, with a range of 1 to 138 months. Fortyfive patients are still patching. The remaining 13 patients never required occlusion therapy. One patient developed strabismus after occlusion therapy. A 6 1h-year-old child with anisometropic hyperopia with no history of strabismus developed a constant 30'" esotropia. This occurred after a single noncompliant episode of part time occlusion was associated with a decrease in visual acuity to 20/50 in the amblyopic eye. Seven and one half months of prior full time occlusion and refractive correction resulted in visual acuity of 20/20 in the right eye and 20/30+ in the left. Full time occlusion was instituted to regain visual acuity. The deviation was stable for three months. She was prism adapted 14 and surgically corrected. Prior to developing strabismus, the patient fused at near on the Worth four dot with a questionable response at distance and had 100 seconds of arc of stereopsis on the Titmus test. While strabismic, the patient demonstrated uncrossed diplopia on the near Worth four dot. Six months postoperatively, she was orthophoric with fix260
NUMBER 2
Table 5. Age at Onset of Treatment versus Best Visual Acuity in 124 Patients
Table 4. Duration of Occlusion and Range
Duration of Occlusion (mos)
•
Visual Acuity
No. of Patients
Age at Onset of Treatment (mos)
Initial (mean Snellen)
Best (mean Snellen)
6 27 61 21 9
0-24 25-48 49-72 73-96 >96
20/200 20/182 20/135 20/128 20/156
20/36 20/36 20/30 20/32 20/37
Table 6. Age at Onset of Treatment versus Duration of Occlusion Maximum Visual Acuity (n = 104)* No. of Patients
Age at Onset of Treatment (mos)
Mean Duration of Occlusion (mos)
5 21 52 18 8
0-24 25-48 49-72 73-96 >96
9.7 8.2
5.7
6.1 4.9
* Thirteen patients were never patched; seven did not increase visual acuity.
Table 7. Patching Results No. of Patients (%) Type Myopia Hyperopia Astigmatism Compound myopic astigmatism/mixed astigmatism Compound hyperopic astigmatism Total
No. of Patients
Slipped :2::2 Lines after Stopping Patch
Still Patching
Never Patched
3/13 (23.1) 0/21 (0) 0/16 (0)
10 17 5
0 4 4
5/9 (55)
5
4
1/7 (14.3)
8
9/66 (13.6)
45
13
ation on a distance and near target and her fusional status was equal to that found before the onset of esotropia. The mean ages of the patients at the onset of treatment at the University ofIowa were calculated for each type of anisometropia (Table 8). The means for each group were not significantly different. The age at treatment onset related to the reason for presentation was calculated. Patients presenting due to strabismus began treatment earlier (4.01 years) than those who presented due to failure ofschool screening examinations (5.70 years) or amblyopia (5.83 years). Initial, final, and best achieved visual acuities were recorded for each patient. Statistical analysis was performed
KUTSCHKE et al
•
ANISOMETROPIC AMBLYOPIA
Table 8. Age at Onset of Treatment Patients with Prior Treatment
Patients without Prior Treatment
Type
No.
Mean (yrs)
(range, mos)
No.
Mean (yrs)
(range, mos)
Myopia Hyperopia Astigmatism Compound myopic astigmatism/mixed astigmatism Compound hyperopic astigmatism
8 15 9
5.45 5.90 5.28
(20-102) (44-101) (39-96)
15 27 16
3.28 5.10 5.10
(14-66) (15-97) (11-110)
7 9
4 2. 6 5.66
(44-72) (43-107)
11 7
4.99 6.83
(27-91) (40-111)
Total
48
5.42
(20-107)
76
4.88
(11 -111)
:
Table 9. Mean Visual Acuity Results Mean Snellen Visual Acuity Type
Initial
Best
Myopia Hyperopia Astigmatism Compound myopic astigmatism/mixed astigmatism Compound hyperopic astigmatism
20/200 20/136 20/81
20/40 20/26 20/27
20/220 20/187
20/56 20/33
Total
20/147
20/32
by transposing the Snellen visual acuity to the logarithm of the minimal angle of resolution (LogMAR) visual acuity.15 The mean initial and best visual acuities for the five types of anisometropia are listed in Table 9. The best achieved visual acuity for all groups combined was significantly related to the initial visual acuity by the Spearman's correlation test (P = 0.0001). Six patients who began with counts fingers vision in their amblyopic eye, however, regained vision to 20/40 or better. Neither the best nor the initial visual acuity was related to the alignment of the patient. Patients with strabismus had a mean initial visual acuity of20/124 and a mean best visual acuity of 20/37, while non strabismic patients had a mean initial visual acuity of20/137 and a mean best visual acuity of 20/30. The relationships between the degree of an-
isometropia and the initial vision and best vision achieved were examined for the myopia, hyperopia, and astigmatism groups. The initial and best visual acuities were not related to the degree of anisometropia using the ANOV A test. Visual outcome was not related to the presence or absence of prior treatment elsewhere. Visual results as related to the type of treatment are listed in Table 10. Twenty-seven non-strabismic patients were given the opportunity to improve visual acuity without patching. Of these, 11 (41 %) obtained good vision with glasses alone. Sixteen needed patching as well as glasses to improve vision. Forty-eight non-strabismic patients were simultaneously prescribed patching and glasses. Thirty of these had had no previous therapy. Forty attained 20/40 or better visual acuity. Two strabismic patients attained a visual acuity of 20/40 or better with glasses alone. One of these patients had intermittent exotropia and the other was a monofixator following esotropia surgery. One hundred three (83.1 %) patients obtained a visual acuity of20/40 or better after amblyopia therapy. Of these, 34 (27.4%) reached a level of 20/20. Further breakdown of vision results 20/40 or better are listed in Table 11. Fourteen (11.3%) achieved visual acuity between 20/50 and 20/80. Seven patients (5.6%) showed no increase in visual acuity after amblyopia therapy and are listed in the
