- Email: [email protected]
Is Myopia Related to Amplitude of Accommodation?
Table 2. Lod Scores From Linkage Analysis of Chromosome 1 Marker Data for Family UM:GL57. Marker Spacing
Recombination Fraction .10
.20
.30
.40
e
z
0.89
1.22
1.23
0.92
0.43
0.15
1.28
-0.85
-0.20
0.03
0.18
0.19
0.13
0.26
0.20
D1S196
1.95
1.81
1.63
1.24
0.80
0.32
0.00
1.98
D1S431
3.69
3.44
3.13
2.43
1.65
0.78
0.00
3.75
D1S433
3.39
3.17
2.87
2.23
1.51
0.71
0.00
3.45
D1S452
1.74
1.63
1.49
1.19
0.85
0.46
0.00
1.76
D1S218
0.59
0.56
0.51
0.41
0.29
0.16
0.00
0.60
D1S212
3.34
3,10
2.80
2.15
1.42
0.65
0.00
3.40
D1S191
1.78
1.67
1.53
1.22
0.87
0.47
0.00
1.81
D1S306
0.54
1.22
1.40
1.33
1.00
0.55
0.13
1.42
Locus
.01
D1S252
-0.30
D1S305
.05
8.5 cMo 22.3 cMo 0.8 cMo 0.0 cMo 6.6 cMo 2.7 cMo 2.1 cMo 6.5 cMo 14.1 cMo
8 = estimated recombination fraction; 2 =: maximum lod (logarithm of the odds ratio) score; cMo == centimorgan.
adds Panama as a country of origin for GLC1A families to the previously reported German,1,4 En glish,4 Irish,4 Danish,5 French,6 and French Canadian3 origins.
onset glaucoma family and evidence of genetic heterogeneity. Hum Genet 1995;96:285-289. 6. Meyer A, Valtot F, Bechetoille A, et al. Liaison du glaucome juvenile au chromosome lq dans deux families francaises. C R Acad Sci (III) 1994;317:565-570.
ACKNOWLEDGEMENT
Our thanks to Frank S. Ashburn, Jr, MD, for pro viding the initial contact with the proband. REFERENCES
Donald S. Fong, MD, MPH
1. Sheffield VC, Stone EM, Alward WLM, et al. Genetic linkage of familial open-angle glaucoma to chromosome Iq21-q31. Nat Genet 1993;4:47-50. 2. Johnson AT, Richards JE, Boehnke M, et al. Clinical phenotype of juvenile-onset primary open-angle glaucoma linked to chromosome lq. Ophthalmology 1996;103:808-814. 3. Morissette J, Cote G, Anctil J-L, et al. A common gene for juvenile and adult-onset primary open-angle glaucomas con fined on chromosome lq. Am J Hum Genet 1995;56: 1431-1442. 4. Wiggs JL, Del Bono EA, Schuman JS, Hutchinson BT, Walton DS. Clinical features offivepedigrees genetically linked to the juvenile glaucoma locus on chromosome Iq21-q31. Ophthal mology 1995;102:1782-1789. 5. Graff C, Urback SF, Jerndal T, Wadelius C. Confirmation of linkage to lq21-31 in a Danish autosomal dominant juvenile-
416
Is Myopia Related to Amplitude of Accommodation? PURPOSE: To report the association between am plitude of accommodation and refractive error. METHODS: Refractive error and amplitudes of accommodation were measured in 1,148 eyes of 696 patients as part of the Early Treatment Diabet ic Retinopathy Study. RESULTS: Eyes with myopia, denned as those with a refractive error of —0.75 diopter or more, have lower accommodative amplitudes (P = .005). After multivariate logistic regression analysis ad justing for age, occupation, and white race, lower
AMERICAN JOURNAL OF OPHTHALMOLOGY
MARCH
1997
Table 1. Comparison of Accommodation and Other Characteristics Between Patients With Myopia (Refractive Error a - 0 . 7 5 Diopter) and Patients Without Myopia Nonmyopic
Ocular characteristics No. of eyes Mean refraction (D) Mean amplitude of accommodation Percent with visual acuity of 20/40 Mean intraocular pressure (mm Hg) Percent with proliferative diabetic retinopathy Systemic characteristics No. of patients or subjects Mean age (yrs) Mean duration of diabetes (yrs) Mean glycosylated hemoglobin Percent with type I diabetes Percent male Percent white Percent professional
696 -0.2 4.33 98.9 16.0 33.04 348 26.3 16.7 10.3 95.1 61.7 92.2 18.8
Myopic
—
1,148 -2.6 4.03 98.2 16.1 30.73
.0001 .0049 .258 .4152 .465
574 27.2 16.6 10.1 94.3 57.6 95.0 26.4
.0042 .8139 .4314 .603 .220 .086 .009
•Comparison of proportions is done by chi-square and of means, by f test.
amplitudes of accommodation remained associated with myopia (P = .03). CONCLUSIONS: Eyes with lower amplitudes of accommodation must use more of their accommo dative reserve for near work. Myopia may be an adaptation that develops in eyes with reduced accommodative amplitudes.
I
N THE OPHTHALMIC LITERATURE, THERE HAS BEEN extensive discussion whether myopia is caused by hereditary or environmental factors. Our study sug gests that myopia may develop in eyes with lower accommodation as an adaptation to reduce the de mands of near work. The Early Treatment Diabetic Retinopathy Study, a randomized clinical trial, was designed to study the timing of photocoagulation and aspirin therapy for diabetic retinopathy.1 A test of accommodation was performed at baseline in patients who were younger than 46 years and had best-corrected visual acuity of 20/40 or better.2 For the present analyses, myopia was Accepted for publication Oct 23, 1996. King/Drew Medical Center, Jules Stein Eye Institute, UCLA School of Medicine. Inquiries to Donald S. Fong, MD, MPH, Jules Stein Eye Institute, 100 Stein Plaza, Los Angeles, CA 90095; fax: (310) 206-3652; e-mail: [email protected]
VOL.123, N o . 3
defined as a refractive error of —0.75 diopter or more. Because amplitudes of accommodation from a diabet ic population are lower and because diabetic patients aged 35 years have amplitudes equal to nondiabetic persons aged 60 years,2 two analyses were performed only on Early Treatment Diabetic Retinopathy Study participants younger than 35 years. Amplitude of accommodation was measured in 1,148 eyes of 696 persons who participated in the Early Treatment Diabetic Retinopathy Study. Univariate analyses disclosed that the populations with and without myopia were very similar (Table 1). However, persons with myopia tended to be older and more likely to report their occupations as professional. Additionally, persons with myopia had a lower mean amplitude of accommodation. To determine the relative contribution of variables identified in the univariate analysis, a multivariate logistic regression analysis was performed to model the risk of developing a refractive error of —0.75 diopter or more. Using both eyes of participants, we found that lower amplitudes of accommodation were statistically significant predictors of myopia, even after adjusting for age, white race, and occupation (Table 2). Because eyes from the same person correlate, a generalized estimating equation analysis also was
BRIEF REPORTS
417
REFERENCES Table 2. Logistic Regression Modeling the Risk of Myopia (Refractive Error >-0.75 Diopter) and Various Risk Factors* Risk Factor
Odds Ratio (P)
Amplitude of accommodation Reported age (yrs) White Occupation of professional
0.94 (.0318)
1. Early Treatment Diabetic Retinopathy Study Research Group. Early Treatment Diabetic Retinopathy Study design and baseline patient characteristics: ETDRS report number 7. Ophthalmology 1991;98(suppl):741-756. 2. Braun CI, Benson WE, Remaley NA, Chew EY, Ferris FL III. Accommodative amplitudes in the Early Treatment Diabetic Retinopathy Study. Retina 1995;15:275-281.
1.05 (.0003) 1.58 (.0496) 1.32 (.0437)
*Data are based on both eyes.
High-altitude Retinopathy Gabriele E. Lang, MD, and Gabriele B. Kuba, MD
performed, and this confirmed that higher accommo dative amplitudes protect against the development of myopia (odds ratio = 0.9), although the relationship was not statistically significant (P = .10). Compared with those eyes with higher amplitudes, eyes with lower amplitudes of accommodation use more of their accommodative reserve for near work. For each distance of near work, myopic eyes use less accommodation than do emmetropic eyes. The my opic state could therefore be considered to benefit eyes that have lower amplitudes of accommodation. One limitation of this study is that the study population was composed entirely of persons with diabetic retinopathy and lower amplitudes of accom modation. However, a study population with lower amplitudes of accommodation would only lower the likelihood of finding an association and would not lead to biases affecting the direction of observed associations. Similar levels of glycosylated hemoglobin and retinopathy severity in those with and without myopia provide additional evidence that the observed difference in amplitudes of accommodation is not caused by differences in severity of diabetes. Our study shows that eyes with myopia have lower amplitudes of accommodation. One possible explana tion for these findings is that myopia develops as a response to accommodation demands. Further studies will be needed to determine whether the association between myopia and lower amplitudes of accommo dation also occurs in other populations. Prospective studies measuring accommodative amplitudes at baseline and monitoring the development of refrac tive error are needed to determine whether lower amplitudes of accommodation lead to myopia. 418
PURPOSE: To report a patient with high-altitude retinopathy. METHODS: A 30-year-old man with high-altitude retinopathy was examined and treated. RESULTS: After spending 2 weeks at an altitude of 7,000 meters and then descending to sea level, the patient's visual acuity was RE, 20/20 and LE, 20/50. Intraretinal hemorrhages in both eyes and a scotoma in the left eye were found. Blood cell count was normal, but hematocrit had increased to 53%. The patient was treated with isovolemic hemodilution, pentoxifylline, and aspirin, which reduced hematocrit to 4 1 % . Visual acuity and visual field returned to normal, and intraretinal hemorrhages resolved. CONCLUSION: High-altitude hemoconcentration should be treated in patients with high-altitude retinopathy.
H
IGH-ALTITUDE HEMOCONCENTRATION IS CAUSED
by excessive water loss resulting from humidify ing cold air and loss in expiration of up to 8 liters per day.1 Hemoconcentration and hypoxia may rapidly become hazardous because they cause acute moun tain sickness, high-altitude cerebral edema, pulmo nary edema, thromboembolism, and high-altitude retinopathy.1'5 Young people1 and people who have
Accepted for publication Oct 7, 1996. Department of Ophthalmology and University Eye Hospital, Universi ty of Ulm. Inquiries to Gabriele E. Lang, MD, Department of Ophthalmology, University of Ulm, Prittwitzstr 43, 89075 Ulm, Germany; fax: 0049-7315027544; e-mail: [email protected]
AMERICAN JOURNAL OF O P H T H A L M O L O G Y
MARCH
1997
Recombination Fraction .10
.20
.30
.40
e
z
0.89
1.22
1.23
0.92
0.43
0.15
1.28
-0.85
-0.20
0.03
0.18
0.19
0.13
0.26
0.20
D1S196
1.95
1.81
1.63
1.24
0.80
0.32
0.00
1.98
D1S431
3.69
3.44
3.13
2.43
1.65
0.78
0.00
3.75
D1S433
3.39
3.17
2.87
2.23
1.51
0.71
0.00
3.45
D1S452
1.74
1.63
1.49
1.19
0.85
0.46
0.00
1.76
D1S218
0.59
0.56
0.51
0.41
0.29
0.16
0.00
0.60
D1S212
3.34
3,10
2.80
2.15
1.42
0.65
0.00
3.40
D1S191
1.78
1.67
1.53
1.22
0.87
0.47
0.00
1.81
D1S306
0.54
1.22
1.40
1.33
1.00
0.55
0.13
1.42
Locus
.01
D1S252
-0.30
D1S305
.05
8.5 cMo 22.3 cMo 0.8 cMo 0.0 cMo 6.6 cMo 2.7 cMo 2.1 cMo 6.5 cMo 14.1 cMo
8 = estimated recombination fraction; 2 =: maximum lod (logarithm of the odds ratio) score; cMo == centimorgan.
adds Panama as a country of origin for GLC1A families to the previously reported German,1,4 En glish,4 Irish,4 Danish,5 French,6 and French Canadian3 origins.
onset glaucoma family and evidence of genetic heterogeneity. Hum Genet 1995;96:285-289. 6. Meyer A, Valtot F, Bechetoille A, et al. Liaison du glaucome juvenile au chromosome lq dans deux families francaises. C R Acad Sci (III) 1994;317:565-570.
ACKNOWLEDGEMENT
Our thanks to Frank S. Ashburn, Jr, MD, for pro viding the initial contact with the proband. REFERENCES
Donald S. Fong, MD, MPH
1. Sheffield VC, Stone EM, Alward WLM, et al. Genetic linkage of familial open-angle glaucoma to chromosome Iq21-q31. Nat Genet 1993;4:47-50. 2. Johnson AT, Richards JE, Boehnke M, et al. Clinical phenotype of juvenile-onset primary open-angle glaucoma linked to chromosome lq. Ophthalmology 1996;103:808-814. 3. Morissette J, Cote G, Anctil J-L, et al. A common gene for juvenile and adult-onset primary open-angle glaucomas con fined on chromosome lq. Am J Hum Genet 1995;56: 1431-1442. 4. Wiggs JL, Del Bono EA, Schuman JS, Hutchinson BT, Walton DS. Clinical features offivepedigrees genetically linked to the juvenile glaucoma locus on chromosome Iq21-q31. Ophthal mology 1995;102:1782-1789. 5. Graff C, Urback SF, Jerndal T, Wadelius C. Confirmation of linkage to lq21-31 in a Danish autosomal dominant juvenile-
416
Is Myopia Related to Amplitude of Accommodation? PURPOSE: To report the association between am plitude of accommodation and refractive error. METHODS: Refractive error and amplitudes of accommodation were measured in 1,148 eyes of 696 patients as part of the Early Treatment Diabet ic Retinopathy Study. RESULTS: Eyes with myopia, denned as those with a refractive error of —0.75 diopter or more, have lower accommodative amplitudes (P = .005). After multivariate logistic regression analysis ad justing for age, occupation, and white race, lower
AMERICAN JOURNAL OF OPHTHALMOLOGY
MARCH
1997
Table 1. Comparison of Accommodation and Other Characteristics Between Patients With Myopia (Refractive Error a - 0 . 7 5 Diopter) and Patients Without Myopia Nonmyopic
Ocular characteristics No. of eyes Mean refraction (D) Mean amplitude of accommodation Percent with visual acuity of 20/40 Mean intraocular pressure (mm Hg) Percent with proliferative diabetic retinopathy Systemic characteristics No. of patients or subjects Mean age (yrs) Mean duration of diabetes (yrs) Mean glycosylated hemoglobin Percent with type I diabetes Percent male Percent white Percent professional
696 -0.2 4.33 98.9 16.0 33.04 348 26.3 16.7 10.3 95.1 61.7 92.2 18.8
Myopic
—
1,148 -2.6 4.03 98.2 16.1 30.73
.0001 .0049 .258 .4152 .465
574 27.2 16.6 10.1 94.3 57.6 95.0 26.4
.0042 .8139 .4314 .603 .220 .086 .009
•Comparison of proportions is done by chi-square and of means, by f test.
amplitudes of accommodation remained associated with myopia (P = .03). CONCLUSIONS: Eyes with lower amplitudes of accommodation must use more of their accommo dative reserve for near work. Myopia may be an adaptation that develops in eyes with reduced accommodative amplitudes.
I
N THE OPHTHALMIC LITERATURE, THERE HAS BEEN extensive discussion whether myopia is caused by hereditary or environmental factors. Our study sug gests that myopia may develop in eyes with lower accommodation as an adaptation to reduce the de mands of near work. The Early Treatment Diabetic Retinopathy Study, a randomized clinical trial, was designed to study the timing of photocoagulation and aspirin therapy for diabetic retinopathy.1 A test of accommodation was performed at baseline in patients who were younger than 46 years and had best-corrected visual acuity of 20/40 or better.2 For the present analyses, myopia was Accepted for publication Oct 23, 1996. King/Drew Medical Center, Jules Stein Eye Institute, UCLA School of Medicine. Inquiries to Donald S. Fong, MD, MPH, Jules Stein Eye Institute, 100 Stein Plaza, Los Angeles, CA 90095; fax: (310) 206-3652; e-mail: [email protected]
VOL.123, N o . 3
defined as a refractive error of —0.75 diopter or more. Because amplitudes of accommodation from a diabet ic population are lower and because diabetic patients aged 35 years have amplitudes equal to nondiabetic persons aged 60 years,2 two analyses were performed only on Early Treatment Diabetic Retinopathy Study participants younger than 35 years. Amplitude of accommodation was measured in 1,148 eyes of 696 persons who participated in the Early Treatment Diabetic Retinopathy Study. Univariate analyses disclosed that the populations with and without myopia were very similar (Table 1). However, persons with myopia tended to be older and more likely to report their occupations as professional. Additionally, persons with myopia had a lower mean amplitude of accommodation. To determine the relative contribution of variables identified in the univariate analysis, a multivariate logistic regression analysis was performed to model the risk of developing a refractive error of —0.75 diopter or more. Using both eyes of participants, we found that lower amplitudes of accommodation were statistically significant predictors of myopia, even after adjusting for age, white race, and occupation (Table 2). Because eyes from the same person correlate, a generalized estimating equation analysis also was
BRIEF REPORTS
417
REFERENCES Table 2. Logistic Regression Modeling the Risk of Myopia (Refractive Error >-0.75 Diopter) and Various Risk Factors* Risk Factor
Odds Ratio (P)
Amplitude of accommodation Reported age (yrs) White Occupation of professional
0.94 (.0318)
1. Early Treatment Diabetic Retinopathy Study Research Group. Early Treatment Diabetic Retinopathy Study design and baseline patient characteristics: ETDRS report number 7. Ophthalmology 1991;98(suppl):741-756. 2. Braun CI, Benson WE, Remaley NA, Chew EY, Ferris FL III. Accommodative amplitudes in the Early Treatment Diabetic Retinopathy Study. Retina 1995;15:275-281.
1.05 (.0003) 1.58 (.0496) 1.32 (.0437)
*Data are based on both eyes.
High-altitude Retinopathy Gabriele E. Lang, MD, and Gabriele B. Kuba, MD
performed, and this confirmed that higher accommo dative amplitudes protect against the development of myopia (odds ratio = 0.9), although the relationship was not statistically significant (P = .10). Compared with those eyes with higher amplitudes, eyes with lower amplitudes of accommodation use more of their accommodative reserve for near work. For each distance of near work, myopic eyes use less accommodation than do emmetropic eyes. The my opic state could therefore be considered to benefit eyes that have lower amplitudes of accommodation. One limitation of this study is that the study population was composed entirely of persons with diabetic retinopathy and lower amplitudes of accom modation. However, a study population with lower amplitudes of accommodation would only lower the likelihood of finding an association and would not lead to biases affecting the direction of observed associations. Similar levels of glycosylated hemoglobin and retinopathy severity in those with and without myopia provide additional evidence that the observed difference in amplitudes of accommodation is not caused by differences in severity of diabetes. Our study shows that eyes with myopia have lower amplitudes of accommodation. One possible explana tion for these findings is that myopia develops as a response to accommodation demands. Further studies will be needed to determine whether the association between myopia and lower amplitudes of accommo dation also occurs in other populations. Prospective studies measuring accommodative amplitudes at baseline and monitoring the development of refrac tive error are needed to determine whether lower amplitudes of accommodation lead to myopia. 418
PURPOSE: To report a patient with high-altitude retinopathy. METHODS: A 30-year-old man with high-altitude retinopathy was examined and treated. RESULTS: After spending 2 weeks at an altitude of 7,000 meters and then descending to sea level, the patient's visual acuity was RE, 20/20 and LE, 20/50. Intraretinal hemorrhages in both eyes and a scotoma in the left eye were found. Blood cell count was normal, but hematocrit had increased to 53%. The patient was treated with isovolemic hemodilution, pentoxifylline, and aspirin, which reduced hematocrit to 4 1 % . Visual acuity and visual field returned to normal, and intraretinal hemorrhages resolved. CONCLUSION: High-altitude hemoconcentration should be treated in patients with high-altitude retinopathy.
H
IGH-ALTITUDE HEMOCONCENTRATION IS CAUSED
by excessive water loss resulting from humidify ing cold air and loss in expiration of up to 8 liters per day.1 Hemoconcentration and hypoxia may rapidly become hazardous because they cause acute moun tain sickness, high-altitude cerebral edema, pulmo nary edema, thromboembolism, and high-altitude retinopathy.1'5 Young people1 and people who have
Accepted for publication Oct 7, 1996. Department of Ophthalmology and University Eye Hospital, Universi ty of Ulm. Inquiries to Gabriele E. Lang, MD, Department of Ophthalmology, University of Ulm, Prittwitzstr 43, 89075 Ulm, Germany; fax: 0049-7315027544; e-mail: [email protected]
AMERICAN JOURNAL OF O P H T H A L M O L O G Y
MARCH
1997