 |
|
Effect of Retinal Ablative Therapy for Threshold Retinopathy of Prematurity
Results of Goldmann Perimetry at the Age of 10 Years
Cryotherapy for Retinopathy of Prematurity Cooperative Group
Arch Ophthalmol. 2001;119:1120-1125.
ABSTRACT
| |
Objective To examine monocular visual fields at the age of 10 years in children
with birth weights less than 1251 g in whom severe acute-phase retinopathy
of prematurity (ROP) developed in 1 or both eyes and who had random assignment
of eyes to cryotherapy (treated) or no cryotherapy (control) and in a comparison
group of children who did not develop ROP in the neonatal period.
Methods Subjects were 255 children who developed severe ROP and 104 children
who did not develop ROP. All were born between January 1, 1986, and November
30, 1987, and had birth weights of less than 1251 g. Goldmann perimetry was
used to measure visual field extent along 8 meridia (15°, 60°, 105°,
150°, 195°, 240°, 285°, and 330°) using the V4e and III4e
stimuli. Data were analyzed by quadrant and overall solid angle of the area
of the retina sensitive to the test stimulus.
Results When blind eyes were assigned a score of 0, visual field area was 24%
to 26% larger in treated eyes than in control eyes. When data from only patients
with 1 sighted treated eye and 1 sighted control eye were examined, visual
field area was 5% smaller in treated eyes than in control eyes. For these
patients, visual field area was reduced by 30% to 37% in treated eyes and
by 27% to 33% in control eyes compared with eyes with no ROP.
Conclusions Cryotherapy preserves peripheral vision in eyes with severe ROP by preserving
sight in these eyes. After excluding 70 blind treated and 102 blind control
eyes, data from eyes with quantifiable visual fields indicate that cryotherapy
produces a small reduction of visual field area in eyes with severe ROP. With
or without cryotherapy, visual field area is considerably smaller in eyes
that had severe acute-phase ROP than in eyes of preterm children who did not
develop ROP.
INTRODUCTION
TREATMENT for severe acute-phase (threshold) retinopathy of prematurity
(ROP) involves ablation of the peripheral retina and, as such, would be expected
to reduce peripheral visual field. Five previous reports1-5
have assessed visual field extent after laser photocoagulation or cryotherapy
for severe ROP. Two of these studies1, 3
used the white-sphere kinetic perimetry method described by Mohn and van Hof-van
Duin.6 This is a relatively simple technique
that uses a large peripheral target and is especially useful in infants and
young children. In 1992, Fetter et al1 reported
normal binocular visual field extent in 8 of 10 one-year-old children who
had undergone cryotherapy in both eyes for severe ROP. More recently, the
multicenter study of cryotherapy for ROP (CRYO-ROP) compared data from eyes
that had undergone cryotherapy for severe acute-phase ROP with data from eyes
with equivalent severity ROP that had not undergone cryotherapy in 78 children
aged 5 years.3 When only pairs of sighted
eyes were considered, visual fields of treated eyes were approximately 6°
smaller than those of control eyes.
Using the more standard technique of Goldmann kinetic perimetry, Tamai
et al5 showed visual field restriction in eyes
of 6 of 11 children, and Takayama et al4 showed
deficits in the eyes of 13 of 13 children who had received laser photocoagulation
or cryotherapy for severe ROP. However, both studies compared the results
of treated eyes with results of eyes that did not develop severe ROP. Therefore,
it is not possible from these studies to determine whether the visual field
abnormalities resulted from severe ROP itself or from treatment of the disease.
In another small case series, Quinn et al2
compared 8 treated with 6 control eyes of 8 patients and found that eyes that
had retinal structure and acuity preserved following cryotherapy for severe
ROP had somewhat smaller visual fields than the control eyes in which vision
was preserved. This result suggested that cryotherapy may produce a small
reduction in visual field extent in eyes with severe ROP.
The purpose of this article is to report Goldmann kinetic perimetry
results from the 10-year study examination of the CRYO-ROP study. Visual field
results from eyes with severe ROP that underwent cryotherapy are compared
with results from eyes with equivalent severity of ROP that did not undergo
cryotherapy. This analysis permits an assessment of whether the benefit in
using cryotherapy to preserve retinal structure is achieved at the cost of
a serious deficit in peripheral visual field extent. For further comparison,
visual field results are presented from a group of children in the CRYO-ROP
study who were not observed to develop ROP during the neonatal period (no
ROP). This allows an evaluation of the effect of serious ROP (with or without
cryotherapy) on visual field extent in children who had birth weights less
than 1251 g compared with a group of children who did not have ROP and who
also had birth weights less than 1251 g.
SUBJECTS AND METHODS
PATIENTS
Eligible subjects were the 255 survivors of the 291 infants who participated
in the randomized trial of CRYO-ROP. All subjects were born between January
1, 1986, and November 30, 1987, and had birth weights of less than 1251 g.
The 291 infants who participated in the randomized trial had developed threshold
ROP in 1 or both eyes during the neonatal period (threshold ROP was defined
as 5 contiguous or 8 cumulative clock hours of stage 3+ ROP in zone 1 or zone
2). Threshold ROP was found in both eyes at the same examination in 240 infants
(bilateral threshold ROP), and one eye was randomly assigned to undergo cryotherapy
and the other assigned to serve as a control. The remaining 51 infants developed
threshold ROP in only 1 eye, and that eye was randomly assigned to receive
cryotherapy or to serve as a control.7-8
At 1 participating center (Philadelphia, Pa), a comparison group of
104 CRYO-ROP study participants who did not develop ROP during the neonatal
period9 were eligible to participate in the
10-year study examination.
Informed consent was obtained from parents before each child's entry
into the study, before randomization if the child developed threshold ROP,
and at entry into both the 5-year and 10-year follow-up phases of
the study. Extensive descriptions of the study population have been published
elsewhere.8, 10-12
PROCEDURES
Goldmann Visual Field Testing
Monocular visual field extent was measured along the 15°, 60°,
105°, 150°, 195°, 240°, 285°, and 330° meridia using
a Goldmann perimeter that has a radius of 300 mm and a background luminance
of 31.5 apostilb. These meridia were selected because of mechanical limitations
of testing the horizontal and vertical meridia using the Goldmann apparatus.
Each subject's right eye was tested first, using the V4e stimulus followed
by the III4e stimulus. Then the left eye was tested with both the V4e and
III4e stimuli. Each stimulus was moved at approximately 3° per second,
and for each stimulus a nonsystematic order of testing at the 8 meridia was
used. Testing was performed after instillation of cycloplegic drops and without
spectacle correction.
Perimetry was conducted by a tester who was masked to the eye's treatment
status. During testing, the child was instructed to fixate on the black dot
at the center of the perimeter and to press the buzzer as soon as the stimulus
was visible in the periphery. The tester made 1 presentation on each meridian
for each target size. However, a second presentation was permitted if the
tester was not confident of the validity of the response (eg, the child showed
poor fixation). The second presentation could be performed at any time during
the test with that stimulus size.
Eye Examinations
Eye examinations, which included cycloplegic retinoscopy and assessment
of ROP residua, were performed by study-certified ophthalmologists. Cycloplegia
was achieved using 1% cyclopentolate hydrochloride. When cyclopentolate was
medically contraindicated, 1% tropicamide was used.
DATA ANALYSIS
Both treated and control eyes of children who participated in the randomized
trial are included in the analysis. For children in the no ROP group, 1 eye
was randomly selected for inclusion in the analysis.
Using a previously described visual field analysis program,13 the shape and extent of the peripheral visual field
were computed for each eye by mathematically projecting the distances and
directions of the isopters for the 8 meridia tested onto the surface of a
hemisphere and calculating the solid angles in square degrees of the polygon
this creates. This solid angle reflects the area of retina sensitive to the
test target used for each isopter and avoids the cartographic distortion inherent
in measurements taken directly from the Goldmann perimetry charts, which represent
azimuthal equidistant polar projections.
Because of the expected possible regionality of the disturbance of retinal
function by ROP and the possible regionality of any effect of cryotherapy,
regional function was assessed by quadrants. Isopters were constructed at
0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°
by non-Euclidean extrapolation of the closest adjacent data points. The solid
angle of the 4 quadrants created by the 45°, 135°, 225°, and 315°
isopters then was used to determine the relative retinal function of the superonasal,
superotemporal, inferotemporal, and inferonasal quadrants. To provide a graphic
representation and comparison of the visual field data from treated and control
eyes, data from left eyes were transposed and presented as if for right eyes.
Statistical analyses were done comparing treated eyes and control eyes.
The Wilcoxon signed rank test was used to test whether the groups had different
visual field areas.
RESULTS
Of the 255 eligible subjects who had threshold ROP, 247 children (96.9%)
completed the 10-year study examination. There were 202 children who had bilateral
threshold ROP, yielding data on 202 treated and 202 control eyes. Forty-five
children had unilateral threshold disease, yielding 25 treated and 20 control
eyes. Visual field data were obtained from 205 of the 227 treated eyes and
from 203 of the 222 control eyes. Visual field data were not obtained from
22 treated and 19 control eyes primarily due to developmental delay. Of the
104 eligible subjects in the no ROP group, 102 (98.1%) participated in the
10-year examination and visual field data were obtained from 85 of these children.
Goldmann perimetry could not be arranged for the remaining 17 children.
Table 1 presents, for the
V4e and III4e isopters, the mean temporal, inferior, nasal, and superior visual
field areas in square degrees for eyes in the no ROP group (left data column),
for all eyes in the treated and control groups (next 2 data columns), for
treated eyes and control eyes with quantifiable visual fields (next 2 data
columns), and for treated eyes and control eyes of patients with bilateral
threshold ROP who had measurable field in both eyes. When data from all eyes
in the treated, control, and no ROP groups are compared (first 3 data columns),
treated eyes have visual fields that are larger by about 24% to 26% than control
eyes, and both have smaller visual fields than eyes in the no ROP group. These
results are shown graphically in Figure 1A for the V4e isopter and Figure
1B for the III4e isopter.
|
|
|
|
Visual Field Area for Eyes That Had No Retinopathy of Prematurity (ROP)
During the Neonatal Period and for Eyes That Were Randomized to Receive Cryotherapy
or No Cryotherapy*
|
|
|
|
|
|
|
Figure 1. Visual field extent for all treated
eyes, all control eyes, and all eyes that did not develop retinopathy of prematurity
(ROP) tested using Goldmann kinetic perimetry with (A) V4e stimulus and (B)
III4e stimulus. For the purpose of presentation, data from left eyes were
transposed and presented as if for right eyes. Blind eyes are assigned a visual
field extent of 0° in all meridia. For the V4e stimulus, data from 205
treated eyes (dashed line), 203 control eyes (solid line), and 85 no ROP eyes
(labeled solid line) are presented. For the III4e stimulus, data from 202
treated eyes, 202 control eyes, and 85 no ROP eyes are presented.
|
|
|
In Table 1, data from treated
and control eyes with quantifiable visual fields are presented in the fourth
and fifth data columns. These data, in which results from 70 blind treated
and 102 blind control eyes have been excluded, suggest that treated eyes have
smaller visual field extent than control eyes by about 7%. Interpretation
of these data is confounded by the inclusion of 2 eyes from some patients
and 1 eye from other patients. Therefore, we examined data from the subset
of patients who had bilateral threshold ROP (1 treated eye and 1 control eye)
and in whom both eyes provided measurable visual fields (right 2 data columns).
These data indicate that treated eyes have smaller visual field extent than
control eyes by about 5%. Matched-pairs signed rank tests conducted on data
from this subset of patients indicated that visual field extent was significantly
smaller for treated than for control eyes only in the inferior visual field
(P<.05 for both isopters). Comparison of data
from eyes in this same subset of patients to data from eyes in the no ROP
group (left data column) showed that visual field extent was smaller in eyes
with severe ROP but had sufficient acuity to permit quantification of visual
field extent than in eyes that did not develop ROP. Data from treated and
control eyes in patients with bilateral threshold ROP who had measurable field
extent are shown graphically in Figure 2A
for the V4e isopter and in Figure 2B
for the III4e isopter. For comparison, data from the no ROP group that were
shown in Figure 1 are replotted
in Figure 2.
|
|
|
|
Figure 2. Quantifiable visual field results
(blind eyes excluded) of treated eyes, control eyes, and eyes that did not
develop retinopathy of prematurity (ROP). Eyes were tested with Goldmann kinetic
perimetry using (A) V4e stimulus and (B) III4e stimulus. For the purpose of
presentation, data from left eyes were transposed and presented as if for
right eyes. For the V4e stimulus, data from 135 treated eyes (dashed line),
101 control eyes (solid line), and 85 no ROP eyes (labeled solid line) are
presented. For the III4e stimulus, data from 132 treated eyes, 100 control
eyes, and 85 no ROP eyes are presented.
|
|
|
COMMENT
The present study used standard Goldmann kinetic perimetry to assess
visual fields of the children in the CRYO-ROP study who had severe ROP and
who were examined at the age of 10 years, as well as a comparison group of
CRYO-ROP study participants who did not develop ROP during the neonatal period.
The results indicated a benefit of cryotherapy in preserving peripheral vision
in eyes with severe ROP, with control eyes showing 24% to 26% smaller visual
field area than treated eyes (Figure 1,
comparison of treated and control eyes). Thus, cryotherapy preserves peripheral
vision in eyes with severe ROP by permitting eyes that would otherwise be
blind to retain a measurable visual field.
Comparison of visual fields in treated and control eyes in which vision
was preserved (Figure 2) showed
a 7% reduction in the area of the visual field in the treated eyes. This potential
adverse effect of cryotherapy is small and likely of little functional importance.
Thus, the results presented in Figure 1
support the benefit of cryotherapy, and the results presented in Figure 2 demonstrate a relatively small decrease
in visual field area in treated eyes in which vision was preserved.
In the present study, a large difference is noted between visual field
extent in eyes of low-birth-weight infants who did not develop ROP (CRYO-ROP
study patients from the Philadelphia participating center) and eyes of low-birth-weight
infants who developed threshold ROP (CRYO-ROP patients from all 23 participating
centers). As shown in Figure 1 and Figure 2, visual field extent was substantially
smaller in eyes that developed threshold ROP than in eyes that did not develop
ROP, irrespective of whether eyes with threshold ROP underwent cryotherapy.
Comparison of visual field area in eyes that did not develop ROP with visual
field area in sighted eyes with severe ROP that did not undergo cryotherapy
(control eyes, third column from right in Table 1) showed a reduction in the area of the visual field in control
eyes of 27.2% for the V4e stimulus and 34.5% for the III4e stimulus. The reduction
in visual field area was slightly larger in treated eyes with quantifiable
visual fields (32.2% for the V4e stimulus and 39.1% for the III4e stimulus).
Thus, among sighted eyes, severe ROP has a much more detrimental effect on
peripheral vision than does peripheral retinal ablation used to treat severe
ROP. However, this conclusion is only tentative because of differences in
demographic characteristics between CRYO-ROP study participants who did not
develop ROP and study participants who developed severe ROP. That is, although
all CRYO-ROP study participants had birth weights less than 1251 g, those
who did not develop ROP were generally of higher birth weight and had fewer
medical complications than did those who developed severe ROP.
Previously, we reported visual field results from a subset of 78 children
from 5 of the 23 CRYO-ROP study centers.3 These
children had developed severe acute-phase ROP during the neonatal period and
were tested with white sphere kinetic perimetry at the age of 5 years.
Results indicated a clear benefit of cryotherapy in preserving peripheral
vision in eyes with severe ROP, but suggested that an adverse effect of preservation
of vision was a small (10%) reduction in visual field extent compared with
sighted eyes with severe ROP that did not receive cryotherapy. The results
of the present study, conducted nearly 5 years later using a standard adult
perimetry procedure, confirmed the earlier report of a clear benefit of cryotherapy
in preserving peripheral vision in eyes with severe ROP. Similar to the results
at 5 years, there was a 5% to 7% reduction in the area of the visual
field among sighted eyes treated with cryotherapy compared with sighted control
eyes that had similar severity of ROP. Thus, even though different methods
were used to measure visual fields, both the 5- and 10-year results
produced essentially similar findings.
In contrast, the reduction in visual field area observed at the 10-year
examination in sighted eyes with severe ROP, compared with eyes that did not
develop ROP, was not observed in the visual field results from the 5-year
examination. At 5 years, sighted eyes with severe ROP showed visual
field extent that was nearly identical to that measured in the group of eyes
that did not develop ROP. This difference in visual field results at 5
and 10 years may be related to differences in methods. At the 5-year
examination, the stimulus was a relatively large (6°) white sphere mounted
on a black wire and moved centrally in front of a black background. In contrast,
the 2 stimuli used at the 10-year examination were small lights (V4e [approximately
2°] and II4e [approximately 0.5°]) that were moved centrally in front
of a white background. It is likely that using smaller, lower-contrast stimuli
at the 10-year examination may have demonstrated more subtle deficits in visual
field extent in sighted eyes with severe ROP.
Three previous studies have used Goldmann perimetry to examine peripheral
vision in children with severe ROP whose eyes underwent peripheral retinal
ablation. Tamai et al5 and Takayama et al4 both reported that visual field extent was smaller
in eyes with severe ROP that underwent peripheral retinal ablation than in
normal eyes. The results of the present study suggest that most of this deficit
was related to the presence of severe ROP rather than to the surgical intervention
(cryotherapy or laser ablation) for the disease. Quinn et al2
studied a small number of children with severe ROP and reported a visual field
deficit of approximately 20% in sighted eyes that received cryotherapy compared
with control eyes. Results of the present study confirmed that there is a
deficit in sighted, cryotherapy-treated eyes, but it is not of the magnitude
previously found by Quinn et al.2
In summary, the results of the present study show a reduction of approximately
5% to 7% in visual field area in the treated eyes of 10-year-old patients
with bilateral threshold ROP in whom both the treated and control eyes showed
quantifiable visual fields. This reduction is similar to the reduction of
approximately 10% in visual field extent observed in our visual field assessment
of the same study population at the age of 5 years. The consistency
of this finding, despite differences in age, methods, and data analysis techniques,
reinforces our earlier conclusion that cryotherapy of the peripheral avascular
retina in eyes with severe ROP may produce a small but measurable reduction
in visual field extent. The benefit of peripheral retinal ablation in preventing
retinal detachment in eyes with severe ROP clearly outweighs the risk of this
potential reduction in visual field extent. This is particularly apparent
when the blind eyes are assigned a score of 0 visual field area (Figure 1). However, caution is needed in
applying peripheral retinal ablation in eyes with less severe ROP, which have
a lower risk for blindness, because these eyes may develop visual field deficits
as a result of the surgical intervention.
An important finding in the present study is the marked (27% to 35%)
deficit in the area of the visual field noted in sighted eyes that had severe
ROP during the neonatal period but were not treated with cryotherapy. This
finding was not apparent until children could be tested with standard adult
perimetry. Thus, in addition to the ROP-related morbidity that can be observed
early in life, eg, retinal scarring, myopia, strabismus, and blindness,9-12 severe
ROP produces more subtle change that only becomes measurable later in life.
This finding underscores the necessity of observing the child with severe
ROP throughout life and supports the importance of continued efforts to prevent
severe ROP through improved medical and/or surgical management of the very
low-birth-weight infant.
AUTHOR INFORMATION
Accepted for publication June 16, 2000.
The CRYO-ROP study is supported by cooperative agreement U10 EY05874
from the National Eye Institute, National Institutes of Health, US Department
of Health and Human Services, Bethesda, Md.
We thank the writing committee for this article: Graham E. Quinn, MD
(chair); Velma Dobson, PhD, Richard Weleber, MD, Robert J. Hardy, PhD, Earl
A. Palmer, MD, Dale L. Phelps, MD, C. Gail Summers, MD, and Betty Tung, MS.
Corresponding author: Graham E. Quinn, MD, Division of Pediatric
Ophthalmology, The Children's Hospital of Philadelphia, First Floor, Wood
Bldg, Philadelphia, PA 19104. Reprints: Earl A. Palmer, MD, CRYO-ROP Headquarters,
Casey Eye Institute, Oregon Health Sciences University, 3375 SW Terwilliger
Blvd, Portland, OR 97201-4197.
From the CRYO-ROP Study Headquarters, the Casey Eye Institute, Oregon
Health Sciences University, Portland. A complete list of the members of the
Cryotherapy for Retinopathy of Prematurity Cooperative Group is published
in this issue (Arch Ophthalmol. 2001;119:1110-1118).
The authors have no affiliation with or financial interest in the subject
matter or materials discussed in the article (eg, employment, consultancies,
stock ownership, honoraria).
REFERENCES
| |
1. Fetter WP, van Hof-van Duin J, Baerts W, Heersema DJ, Wildervanck de Blecourt-Devilee M. Visual acuity and visual field development after cryocoagulation in
infants with retinopathy of prematurity. Acta Paediatr. 1992;81:25-28.
ISI
| PUBMED
2. Quinn GE, Miller DL, Evans JA, Tasman WE, McNamara JA, Schaffer DB. Measurement of Goldmann visual fields in older children who received
cryotherapy as infants for threshold retinopathy of prematurity. Arch Ophthalmol. 1996;114:425-428.
ABSTRACT
3. Quinn GE, Dobson V, Hardy RJ, Tung B, Phelps DL, Palmer EA. Visual fields measured with double-arc perimetry in eyes with threshold
retinopathy of prematurity from the Cryotherapy for Retinopathy of Prematurity
Trial. Ophthalmology. 1996;103:1432-1437.
ISI
| PUBMED
4. Takayama S, Tachibana H, Yamamoto M. Changes in the visual field after photocoagulation or cryotherapy in
children with retinopathy of prematurity. J Pediatr Ophthalmol Strabismus. 1991;28:96-100.
PUBMED
5. Tamai A, Iyota K, Ueno H, Noda K, Kishi S. A follow-up study of retinopathy of prematurity, with special reference
to the visual functions of the eyes treated by photocoagulation and/or cryocautery. Acta XXVI Int Congr Ophthalmol. 1983;1:417-420.
6. Mohn G, van Hof-van Duin J. Development of the binocular and monocular visual fields of human infants
during the first year of life. Clin Vis Sci. 1986;1:51-64.
7. Cryotherapy for Retinopathy of Prematurity Cooperative Group. Multicenter trial of cryotherapy for retinopathy of prematurity: preliminary
results. Arch Ophthalmol. 1988;106:471-479.
ABSTRACT
8. Cryotherapy for Retinopathy of Prematurity Cooperative Group. Multicenter trial of cryotherapy for retinopathy of prematurity: three-month
outcome. Arch Ophthalmol. 1990;108:195-204.
ABSTRACT
9. Cryotherapy for Retinopathy of Prematurity Cooperative Group. The natural ocular outcome of premature birth and retinopathy: status
at 1 year. Arch Ophthalmol. 1994;112:903-912.
ABSTRACT
10. Cryotherapy for Retinopathy of Prematurity Cooperative Group. Multicenter trial of cryotherapy for retinopathy of prematurity: one-year
outcome: structure and function. Arch Ophthalmol. 1990;108:1408-1416.
ABSTRACT
11. Cryotherapy for Retinopathy of Prematurity Cooperative Group. Multicenter trial of cryotherapy for retinopathy of prematurity: 3-year
outcome: structure and function. Arch Ophthalmol. 1993;111:339-344.
ABSTRACT
12. Cryotherapy for Retinopathy of Prematurity Cooperative Group. Multicenter trial of cryotherapy for retinopathy of prematurity: Snellen
visual acuity and structural outcome at 5 years after randomization. Arch Ophthalmol. 1996;114:417-424.
ABSTRACT
13. Weleber RG, Tobler WR. Computerized quantitative analysis of kinetic visual fields. Am J Ophthalmol. 1986;101:461-468.
ISI
| PUBMED
RELATED ARTICLES
Multicenter Trial of Cryotherapy for Retinopathy of Prematurity: Ophthalmological Outcomes at 10 Years
Cryotherapy for Retinopathy of Prematurity Cooperative Group
Arch Ophthalmol. 2001;119(8):1110-1118.
ABSTRACT
| FULL TEXT
Contrast Sensitivity at Age 10 Years in Children Who Had Threshold Retinopathy of Prematurity
Cryotherapy for Retinopathy of Prematurity Cooperative Group
Arch Ophthalmol. 2001;119(8):1129-1133.
ABSTRACT
| FULL TEXT
Ten-Year Follow-up From the CRYO-ROP Study
William Tasman
Arch Ophthalmol. 2001;119(8):1200-1201.
EXTRACT
| FULL TEXT
Archives of Ophthalmology Reader's Choice: Continuing Medical Education
Arch Ophthalmol. 2001;119(8):1234-1235.
FULL TEXT
THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES
|
Population-Based Assessments of Ophthalmologic and Audiologic Follow-up in Children With Very Low Birth Weight Enrolled in Medicaid: A Quality-of-Care Study
Wang et al.
Pediatrics 2008;121:e278-e285.
ABSTRACT
| FULL TEXT
Evaluating the Cryotherapy for Retinopathy of Prematurity Study (CRYO-ROP)
Mills
Arch Ophthalmol 2007;125:1276-1281.
FULL TEXT
Quality-of-Care Indicators for the Neurodevelopmental Follow-up of Very Low Birth Weight Children: Results of an Expert Panel Process.
Wang et al.
Pediatrics 2006;117:2080-2092.
ABSTRACT
| FULL TEXT
We Can Aim at Better Results in Coming Years--Reply
Palmer
Arch Ophthalmol 2006;124:605-606.
FULL TEXT
15-Year Outcomes Following Threshold Retinopathy of Prematurity: Final Results From the Multicenter Trial of Cryotherapy for Retinopathy of Prematurity
Cryotherapy for Retinopathy of Prematurity Coopera
Arch Ophthalmol 2005;123:311-318.
ABSTRACT
| FULL TEXT
Health-Related Quality of Life at Age 10 Years in Very Low-Birth-Weight Children With and Without Threshold Retinopathy of Prematurity
CRYO-ROP Cooperative Group
Arch Ophthalmol 2004;122:1659-1666.
ABSTRACT
| FULL TEXT
Educational and Social Competencies at 8 Years in Children With Threshold Retinopathy of Prematurity in the CRYO-ROP Multicenter Study
Msall et al.
Pediatrics 2004;113:790-799.
ABSTRACT
| FULL TEXT
Ten-Year Follow-up From the CRYO-ROP Study
Tasman
Arch Ophthalmol 2001;119:1200-1201.
FULL TEXT
|
