Original Article

The Long-term Visual Outcomes of Primary Congenital
Glaucoma

Hamed Esfandiari1,2, MD; Alisa Prager2, MD, MPH; Kiana Hassanpour3, MD, MPH; Sudhi P. Kurup1,2, MD
Rebecca Mets-Halgrimson1,2, MD; Hawke Yoon1,2, MD; Janice Lasky Zeid1,2, MD; Marilyn B. Mets1,2, MD

Bahram Rahmani1,2, MD, MPH

1Division of Ophthalmology, Ann & Robert H. Lurie Children’s Hospital of Chicago, Chicago, USA
2Department of Ophthalmology, Northwestern University Feinberg School of Medicine, Chicago, USA

3Ophthalmic Research Center, Institutue for Ophthalmology and Vision Science, Shahid Beheshti University of Medical
Sciences, Tehran, Iran

ORCID:
Hamed Esfandiari: https://orcid.org/0000-0001-7301-7047
Alisa Prager: https://orcid.org/0000-0002-8474-9398

Abstract
Purpose: To evaluate the long-term visual outcomes of ab externo trabeculotomy for primary
congenital glaucoma (PCG) at a single pediatric ophthalmology center.
Methods: In this retrospective single-center case series, data from 63 eyes of 40 patients
who underwent ab externo trabeculotomy between September 2006 and June 2018 were
included. The data were analyzed for best corrected visual acuity (BCVA), stereopsis, and
surgical success. Kaplan–Meier analysis was performed using the surgical success criteria
defined as intraocular pressure (IOP) ≤ 21 mmHg and ≥ 20% below baseline without the
need for additional glaucoma surgery.
Results: BCVA at the time of diagnosis was 0.37 ± 0.48 logMAR, which changed to 0.51
± 0.56 logMAR at the final follow-up (P = 0.08). Twenty-five percent of patients had BCVA
equal to or better than 20/40 at the final visit. The mean refraction at baseline was –4.78
± 5.87 diopters, which changed to less myopic refraction of –2.90 ± 3.83 diopters at the
final visit. Optical correction was prescribed in 66% of eyes at the final visit. The average
final stereopsis was 395.33 sec of arc. The linear regression model showed a significant
association between the surgery success rate and final BCVA as well as stereoacuity (P-
values: 0.04 and 0.03, respectively). Intraocular pressure (IOP) decreased significantly from
29.79 ± 7.67 mmHg at baseline to 16.13 ± 3.41 mmHg at the final follow-up (P = 0.001).
Conclusion: Patients with PCG can achieve an acceptable visual acuity and stereoacuity,
particularly in cases of timely intervention and close follow-up.

Keywords: Ab Externo Trabeculotomy; Long-term Outcomes; Primary Congenital Glaucoma;
Stereopsis; Visual Function

J Ophthalmic Vis Res 2020; 15 (3): 326–330

Correspondence to:

Alisa Prager, MD. Department of Ophthalmology,
Northwestern University Feinberg School of Medicine,
645 N Michigan Ave., Chicago, Illinois 60611, USA.
Email: alisa.prager@gmail.com
Received: 10-07-2019 Accepted: 02-01-2020

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DOI:
10.18502/jovr.v15i3.7451

INTRODUCTION
Primary congenital glaucoma (PCG) is the most
common type of childhood glaucoma and a
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How to cite this article: Esfandiari H, Prager A, Hassanpour K, Kurup SP,
Mets-Halgrimson R, Yoon H, Zeid JL, Mets MB, Rahmani B. The Long-term
Visual Outcomes of Primary Congenital Glaucoma. J Ophthalmic Vis Res
2020;15:326–330.

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Visual Outcomes of Congenital Glaucoma; Esfandiari et al

major cause of blindness in children.[1, 2] PCG is
secondary to angle dysgenesis and is primarily a
surgical condition.[3] Surgical options include angle
surgeries, trabeculectomy, glaucoma drainage
devices, and cyclodestructive procedures in
advanced cases.[4] Historically, the effect of angle
surgeries on the intraocular pressure (IOP) has
been considered the main outcome measure in
most studies on PCG.

While surgical outcomes are thoroughly
discussed in the literature, not much is known
about the visual outcomes of glaucoma surgery
in patients with PCG. Studies have shown that
unilateral disease, poor vision at the time
of diagnosis, multiple surgeries, and ocular
comorbidities are associated with poor visual
outcomes.[5] Even after a timely intervention,
these patients need treatment and monitoring for
amblyopia, which necessitate frequent visits or
examination under anesthesia. The final visual
outcome is strongly related to early diagnosis and
management of amblyopia. Frequent anesthesia
or sedation, complexity of the disease, and the
associated visual impairment could have significant
impact on children’s psychological behavior and
make the assessment of visual function more
complicated.[6] Thus, the ultimate goal of childhood
glaucoma management is lifelong control of IOP to
maintain visual function.[7, 8]

The purpose of this study was to report the
long-term visual outcomes (including Snellen visual
acuity and stereopsis) of patients with PCG, treated
with ab externo trabeculotomy at a single center.

METHODS

This study was approved by the Institutional Review
Board of the Ann & Robert H. Lurie Children’s
Hospital of Chicago. We followed the tenets of
the Declaration of Helsinki and regulations of
the Health Insurance Portability and Accountability
Act.

Patients who underwent ab externo
trabeculotomy for PCG at the Lurie Children’s
pediatric ophthalmology center between
September 2006 and June 2018 were identified
using current procedural terminology (CPT)
codes and included in the study. We collected
data such as preoperative IOP, baseline ocular
biometric characteristics including axial length (AL),
central corneal thickness (CCT), corneal diameter,

presence of Haab’s striae, number of preoperative
glaucoma medications, type of surgery, and
intra- and postoperative complications. The
severity of glaucoma was assessed using
three parameters: IOP, corneal diameter, and
corneal clarity. Each parameter was given a
score of 1–3, and the total score decided the
severity of PCG: mild (1–3), moderate (4–6),
or severe (7–9) PCG.[9] At each postoperative
visit, the best corrected visual acuity (BCVA),
stereopsis, IOP, glaucoma medications, and
complications were noted. Surgical success
criteria were defined as IOP ≤ 21 mmHg and
≥ 20% below the baseline without the need
for additional glaucoma surgery (except ab
externo trabeculotomy). The exclusion criteria
were as follows: history of intraocular surgery,
combined surgical procedures, any forms of
anterior segment dysgenesis, and a follow-up of
less than six-months.

Stereopsis was quantitatively assessed with
the Titmus test (Stereo Optical Inc., Chicago,
IL) with fly and graded circles. During the
examination, children wore their correction
under the Polaroid lenses, and the examiner
used his index finger to guide fixation. Patients
were asked to grab the wings of the fly and
point out to the circle that seemed to “jump”
out of the book. In the case of a wrong answer,
the immediately preceding target was repeated.
The last correct target identified was used as
the child’s stereopsis measurement. Vision was
measured with age-appropriate methods and
converted to logMAR for statistical analysis. All
patients underwent complete ophthalmologic
and orthoptic evaluation. Cycloplegic refraction
were performed by instilling two drops of 1%
cyclopentolate hydrochloride in each eye at 5-min
intervals.

All surgeries were performed under general
anesthesia. A fornix-based localized peritomy was
created in the temporal or superior quadrant.
Triangular or rectangular 3mm limbal base
superficial scleral flap was fashioned, followed
by a radial incision to expose the Schlemm
canal under high magnification. Scleral cut-
down was initiated from the blue zone up to
the white zone until aqueous was seen oozing
out from the cut ends of the canal. The Harms
Trabeculotome was then passed into each end
of the Schlemm canal to gently cut through
the canal in the anterior chamber. The scleral

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Visual Outcomes of Congenital Glaucoma; Esfandiari et al

flap and peritomy were sutured with Vicryl
sutures.

All statistical analyses were performed using
the SPSS software (SPSS Statistics for Windows,
Version 25, IM Corp., Armonk, NY, USA). To
compare the change in IOP, we used an interaction
analysis within a linear mixed model. To evaluate
the baseline differences, we used the T-test, Chi-
Square, and Fisher’s exact tests. Kaplan–Meier
survival plots were constructed to assess the long-
term survival rates; these were compared using the
log-rank test. Linear regression analysis was used
to evaluate the factors associated with surgical
success.

RESULTS

Sixty-three eyes of 40 patients were included in
this study. The mean age at diagnosis was 6.8
± 10.6 months and 62.5% of the patients were
male. The mean follow-up time was 85.7 ± 32.9
months (Table 1). The preoperative BCVA was 0.37
± 0.48, which changed to 0.51 ± 0.56 logMAR at
the final follow-up (P = 0.08). The baseline visual
acuity was measured with fixation and following
method in 27 eyes, Teller acuity card in 30, LEA
symbols in 4, and HOTV in 2. Twenty-five percent
of patients had BCVA ≥ 20/40 at the final visit.
The mean refraction of the patients was –4.78
± 5.87 diopter at baseline, which changed to
less myopic refraction of –2.90 ± 3.83 diopter
at the final visit. Sixty-six percent of eyes were
prescribed optical correction at the final visit.
The average final stereopsis was 395.33 sec of
arc (range, 40–800). The linear regression model
showed a significant association between surgical
success and final BCVA as well as stereoacuity
(P-values: 0.04 and 0.03, respectively). The final
stereoacuity corresponded to the final BCVA of
0.61 logMAR. The average baseline IOP was 29.7
± 7.6 mmHg, which decreased to 16.1 ± 3.4
mmHg at the final visit, corresponding to 44%
reduction from the baseline. The Kaplan–Meier
survival curves indicated a time to failure of 107.7
± 9.04 months. Among the baseline parameters,
only age at diagnosis of less than three months
was associated with a higher failure rate. Of the 63
eyes, 21 met the criteria for mild, 29 for moderate,
and 13 for severe PCG. While mild PCGs had
significantly better visual acuity and stereopsis
at the final follow-up (P < 0.05), there was no

significant difference between the moderate and
severe groups. Thirty-five eyes (56%) underwent
repeat trabeculotomy to treat a different area of
the trabecular meshwork because of inadequately
controlled IOP after the first session. Additional
glaucoma surgery (glaucoma shunt procedure) was
performed in seven patients.

DISCUSSION

The main goal of our study was to determine
the long-term visual outcome of ab externo
trabeculotomy for PCG. In our study, ab externo
trabeculotomy resulted in 44% reduction in the IOP
with a long-term success rate of 65%. Our success
rate is consistent with those in previous reports,
which ranged from 45% to 85%.[8, 9] The final visual
acuity in our study was 0.51 logMAR and 25% of
the patients had corrected vision better than 20/40
at the final visit. The visual outcome in our study
is comparable to that of other reports with similar
demographic data.[10, 11] However, we found better
final visual function than that reported previously
in the AlDarrab study in which 55% of the patients
had BCVA < 20/60.[6] Poor visual outcomes in their
study could be explained by more severe glaucoma
population, high prevalence of CYP1B1 mutation,
delayed diagnosis, and inadequate follow-up.[12]

Poor vision in children with PCG is multifactorial;
high IOP in early life causes structural changes in
the eye such as globe enlargement, corneal edema
and opacity, tears in the Descemet’s membrane
(Haab’s striae), high refractive error, anisometropia,
and glaucomatous optic neuropathy[13–15]. Corneal
edema was present in almost 55% of patients
at the time of diagnosis, which resolved after
surgery in all cases, but accompanying Haab’s
striae, with or without corneal edema, persisted in
two-third of our patients. Myopic refraction was the
most frequent refractive error at baseline, which
decreased with IOP reduction. The correlation
between myopia and glaucoma can be attributed
to the increase in the axial diameter of the eye as
a consequence of high IOP.[14] Sixty-six percent of
our patients needed optical correction for myopia
or myopic astigmatism at the final visit. Astigmatism
is usually related to asymmetric expansion of
the anterior chamber, corneal scar, and Haab’s
striae. In most cases, only optical correction was
prescribed, but in 7% of the eyes (5 eyes) optical
devices were needed. Telescopic systems (angular

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Visual Outcomes of Congenital Glaucoma; Esfandiari et al

Table 1. Baseline characteristics of the patients.

Clinical characteristics (Range)

Gender Male 25 (62.5%)

Unilateral disease Number (%) 17 (42.5%)

Age at the time of diagnosis Mean ± SD (Months) 6.89 ± 10.68 (0 – 63)
Follow-up Mean ± SD (Months) 85.74 ± 32.95 (3 – 156)
IOP Mean ± SD (mmHg) 29.79 ± 7.67 (11 – 54)
C/D ratio Mean ± SD 0.55 ± 0.22 (0.2 – 0.95)
Corneal diameter Mean ± SD (mm) 12.79 ± 1.26 (9.50 – 15.5)
Central corneal thickness Mean ± SD (Microns) 585.44 ± 76.57 (470 – 761)
Axial length Mean ± SD (mm) 22.37 ± 2.50 (17.50 – 28.50)
Refraction Mean ± SD (Diopters) –4.78 ± 5.87 (–25.0 – +5.50)
Time of diagnosis by category ≤ 3 Months 18 (31%)

3 < Age ≤ 6 months 26 (48%)
> 6 months 14 (24.1%)

Ocular signs Presence of Haab striae 45 (72.6%)

Buphthalmos 30 (83.3%)

Ocular symptoms Tearing 30 (93.8%)

Photophobia 24 (82.8%)

SD, standard deviation; IOP, intraocular pressure; C/D ratio, cup to disc ratio

magnification) were the most common aids used
for improving vision. Lower magnifications are
beneficial in constricted visual field and low image
illumination.[13] No patient needed optical aid for
near vision, probably due to the large range of
accommodation in children. Optical devices can
improve the visual function and promote daily
activities; therefore, they should be employed as
early as possible.[15]

We did not find any association between the age
at diagnosis and final visual acuity. This finding is
in contrast to other studies that showed a close
relationship between age at PCG diagnosis and
visual function.[13] However, we found a positive
association between IOP control and final visual
function. It is likely that timely intervention in
our cohort and close follow-up reversed the
detrimental effect of high IOP on the function and
structure of the eye.

The average final stereopsis in our study was
395.33 sec of arc. The relationship between visual
acuity of the amblyopic eye and stereoacuity
is complex.[16] In general, worse visual acuity is
associated with worse stereoacuity; however, it
largely depends on the etiology of amblyopia;

strabismic amblyopes have the worst stereoacuity,
while anisometropic amblyopes retain some
stereopsis.[17] Furthermore, the presence of
stereoacuity in patients with PCG can improve
the outcomes of amblyopia treatment.[18, 19] The
results of our study show that while stereoacuity
is not normal, it is nevertheless functional in many
patients.

Our study was limited by its retrospective
nature, variable follow-up duration, and multiple
examiners. Additionally, this study was conducted
at a single tertiary academic referral center,
and the results may not be generalizable to
other practice facilities. Baseline visual acuity
measurement was not optimal due to age, which
made the comparison of pre- and post-surgery
measurements less reliable. However, the aim of
our study was to present the long-term outcomes
of visual function of PCG. Such data for visual acuity
are scarce in the literature and there has been no
study on stereopsis outcome in PCG.

In summary, the result of our study showed that
patients with PCG can achieve an acceptable visual
acuity and stereoacuity with timely intervention
and close follow-up. Although our study was

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Visual Outcomes of Congenital Glaucoma; Esfandiari et al

not designed to compare the visual function
changes after ab externo trabeculotomy, we did
not observe any improvement in visual acuity as
this parameter could be reliably measured after
the procedure. This lack of significant improvement
should be discussed preoperatively to gauge the
expectations.

Financial Support and Sponsorship

None.

Conflicts of Interest

There are no conflicts of interest.

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