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Abstracts: October 2005 :: |
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Comparison
of the biomechanical behavior of foldable intraocular
lenses
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Lane SS, Burgi P, Milios GS, Orchowski MW,
Vaughan M, Schwarte E.
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J Cataract Refract Surg.
2004; 30: 2397-2402.
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A surgeon’s decision on which intraocular lens (IOL)
to use is based on maximizing clinical outcomes. The IOL
choice should takeinto
account characteristics such as ease of implantation,
consistency of postoperative
refractive results, and minimizing posterior capsule
opacification (PCX)) and intraocular inflammatory
response. As the
biomechanical performance of an IOL can
directly
affect
these clinical
outcomes,
these parameters must play an important role in the
surgeon’s choice of IOL.
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Haptic compression force and compression force decay are
part of the standardized testing of IOL performance
required to characterize the in vivo behavior of a given
lens. The haptics are designed to exert pressure on eye
structures to fixate the IOL. Because haptics are made
from polymeric material, a certain amount of stress
relaxation taken place when the haptics are compressed.
As stress relaxation occurs, the amount of pressure the
haptics exert decreases. The haptics should be designed
to provide sufficient pressure for fixation after the
haptic material has experienced stress relaxation.
Haptic compression force and haptic compression
force decay rests are designed to quantify the
change in the haptic force under simulated in vivo
conditions.
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The
purpose of this study was to compare a standardized
battery of biomechanical laboratory tests to assess the
performance of popular foldable intraocular lenses (lOLs).
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Using
industry-standard biomechanical testing techniques, 1
and 3 piece foldable lOLs (Alcon AcrySof MA60BM, MA30BA,
SA30AL, SA60AT; Allergan Sensar AR40, PhacoFlex II
SI-40NB; Bausch & Lomb Soflex LI61U; Pharmacia and
Upjohn CeeOn 920) and a 1-piece all-poly (methyl
methacrylate) (PMMA) IOL (Alcon MZ30BD) were tested
under identical conditions with regard to (1)
tensile/elastic properties by comparing haptic pull
strength and haptic elongation and (2) compression
properties by comparing haptic compression forces,
haptic compression force decay over time, and axial
displacement. All tests were performed with the lOLs
submersed in a controlled-temperature water bath (mean
35°C ± 2°C).
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Authors concluded with remarks that AcrySof 1-piece
SA30AL and SA60AT lOLs demonstrated superior
biomechanical characteristics over other foldable IOL
designs.
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Quality
of vision after AMO Array multifocal intraocular lens
implantation
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Sen HN, Sarikkola AU,
Uusitalo RJ, Laatikainen L.
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J Cataract Refract
Surg. 2004; 30:2483-93.
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Cataract
surgery and intraocular lenses (lOLs) have evolved significantly during the past decades. Despite
excellent restoration of visual acuity and good
biocompatibility of presently used foldable lOLs, there is no accommodation in
pseudophakic eyes and patients remain presbyopic after
surgery. This problem was partly solved by the
introduction of multifocal IOLs. These lenses represent an interesting approach by providing
the patient with normal distance vision
as well as adequate near vision without glasses. The Array SA40N (AMO) is the first multifocal IOL approved by the
U.S. Food and Drug Administration and
is reported to offer better outcomes, as demonstrated by
reduced dependence on glasses, increased range of vision
from near to far, and probably enhanced
quality of life. This lens is distance dominant,
with the central zone for distance and series of refractive
zones on the anterior surface. The distribution
of incoming light to more than 1 focus from these
zones theoretically and clinically decreases contrast
sensitivity and increases glare disability because
the image of a distinct focus is always overlapped by
out of focus images generated by the multifocal
principle. Therefore, it is important to evaluate the
quality of vision in patients with multifocal lOLs.
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The purpose of this study was to evaluate safety and
efficacy of Array SA40N multifocal intraocular lens (IOL)
(AMO) implantation in cataract surgery.
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In this prospective randomized
comparative trial, 80 patients scheduled for cataract
surgery were selected based on preoperative counseling
and randomized to have multifocal or monofocal IOL
implantation. Fifty-three eyes of 35 patients received a
multifocal IOL and 67 eyes of 40 patients, a monofocal
IOL. The incidence of complications and visual outcome
in the multifocal and monofocal IOL groups were
compared. Quality of vision was measured by comparing
the severity of visual symptoms (glare, halos, and
cataract symptoms score), changes in functional
impairment measured by a 7-item visual function test
(VF-7), changes in global measures of vision (trouble
and satisfaction with vision), and range of
accommodation and contrast sensitivity.
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Intraoperative and postoperative complications and
adverse events were few and required no further surgical
intervention. Both distance and near visual acuities
were significantly better in the multifocal group than
in the monofocal group; the difference was most
prominent in distance corrected near acuity (P<.001).
Thirty-five eyes (67.3%) in the multifocal group and 10
eyes (14.9%) in the monofocal group achieved a
distance corrected near acuity of J6 (20/40) or better;
30 eyes (56.6%) and 19 eyes (28.4%), respectively,
achieved a best corrected distance acuity of 20/20 or
better. Glare symptoms decreased postoperatively in both
groups but were slightly more common in the multifocal
group. In contrast, halos were significantly more common
at 1 month in the multifocal group (P<.001). Contrast
sensitivity values were slightly lower with multifocal
lOLs at almost all spatial frequencies, but the
difference was not significant. The change in the
quality of life postoperatively, measured with the VF-7,
was significant and identical in both groups.
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Near
vision restoration with refractive lens exchange and
pseudoaccommodating and multifocal refractive and
diffractive intraocular
lenses. |
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Alio JL, Tavolato M, Hoz FD, Claramonte P, Prats
JLR, Galal A |
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J Cataract Refract
Surg. 2004; 30:2494-2503 |
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Management of presbyopia is a challenge for refractive
surgeons. Options include scleral expansion surgery,
zonal photorefractive keratectomy, implantation
of corneal inlays, and implantation of multifocal and
bifocal intraocular lenses (lOLs) However, surgical
methods such as scleral expansion surgery are of limited
effect, and other methods do not have the potential to
fully restore accommodation. Studies of previous models
of multifocal and bifocal lOLs
seemed beneficial but were mainly used to reduce spectacle
dependence for near vision, restoring visual acuity
but decreasing contrast sensitivity |
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Recent designs
introduced by Payer and Gumming and Kammann provide
pseudoaccommodation by focus shift, by forward movement
of the lens optic. The
ability of these lOLs to restore near vision is dependent
on multicorrelated factors in the accommodation
process.
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The purpose of this study was to evaluate near visual
performance after implantation of a pseudoaccommodating
intraocular lens (IOL) (Crystalens AT-45, eyeonics) or a
multifocal IOL (refractive model, AMO Array; diffractive
model, AcriTec TwinSet) after lens surgery.
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Forty patients were included in this prospective
clinical comparative study. The patients were divided
into 3 groups according to the type of IOL implanted.
Group 1 included 24 eyes (12 patients) implanted with
the Crystalens IOL; Group 2, 32 eyes (16 patients) with
the Array IOL, and Group 3, 24 eyes (12 patients) with
the TwinSet IOL. Bilateral phacoemulsification and IOL
implantation were performed in all patients, and the
follow-up was 1 year. The postoperative main visual
outcome evaluations were uncorrected and best corrected
distance and near visual acuities, mean add for near,
and best distance-corrected near acuity.
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In Group 1, the mean uncorrected near acuity was 20/40
preoperatively and 20/25 after 1 year. The mean
preoperative best distance corrected near acuity was 20/32 and 20/25 after 1 year. In Group 2, the mean uncorrected near
acuity was 20/40 and 20/25, respectively. The
mean preoperative best distance-corrected near acuity
was 20/32 and 20/25 after 1 year. In Group 3, the mean
uncorrected near acuity was 20/63 preoperatively; after
1 year, it was approximately 20/25. The mean best
distance- corrected near acuity was 20/50 and 20/25,
respectively. A neodymium:YAG laser capsulotomy was
performed for posterior capsule opacification when
required, with no change in the refractive outcome.
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Authors concluded with remarks that implantation of
multifocal and pseudoaccommodating lOLs provides
adequate near vision restoration. The TwinSet IOL
provided faster recovery of near vision than the other 2
lOLs. The Crystalens IOL provided less postoperative
visual phenomena with favorable near vision. The Array
IOL achieved the most comfortable distance and near
vision.
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Assessment
of visual satisfaction and function after
cataract surgery |
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Pager CK |
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J
Cataract Refract Surg. 2004; 30:2510-16
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Although it is widely recognized that visual acuity is a poor
measure of the need for cataract surgery or its
successful outcome, a visual acuity of 6/12
continues to be cited as evidence of both5.
In fact, visual
acuity correlates poorly
with patient visual
satisfaction
and disability. Thus, patient-perceived outcomes
such as functional status are increasing being
accepted as the most useful measures. Although
appealing in theory, the widespread use of patient
centered outcomes has been difficult to implement in
practice. Physicians and patients rarely see eye-to-eye,
with doctor-patient assessments of visual
satisfaction and quality of life differing substantially.
This may explain why in 1 study,
17% of patients
listed for cataract surgery believed their visual problems
were so insignificant that surgery was not warranted. In
another study, 2% to 5% reported no trouble
with their
vision. In
addition,
expert panels agree
on the indications for surgery little
more than half the time and 2% to 16% of cataract
extractions may be inappropriate, especially in eyes
with a visual acuity better than 6/12.
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The purpose of the study was to examine the
relationships between importance, satisfaction, visual
acuity, and visual function in a sample of preoperative
cataract patients and to derive and prospectively
evaluate a shortened measure of visual function. |
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Two independent
samples of 111 and 121 patients were surveyed before and
after surgery with regard to their visual satisfaction,
trouble with vision, VF-14 visual function, overall
satisfaction, and importance of factors affecting
patient satisfaction. A 7-item scale of visual function
derived from the first sample's results was
prospectively tested against the second sample. Distance
and reading acuities were recorded from the patients’
charts.
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The 7-item
measure of visual function strongly correlated with the
VF-14 (r>0.9) and had predictive power equal to that
of the VF-14 for satisfaction and trouble with vision.
Distance visual acuity was not significantly correlated
with visual function, satisfaction, or trouble with
vision, although reading acuity was significantly
correlated with visual function and trouble with vision
(r = 0.31 and r = 0.32, respectively).
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Author
concluded with the remarks that a shortened measure of
visual function that had a predictive value equal to
that of the VF-14 can more practically be used in
everyday practice. Furthermore, the study showed that
regional factors matter and highlights the necessity of
basing measurement scales on factors important to the
population in question to ensure scale
validity. |
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Impact
factors on intraocular pressure measurement in healthy
subjects |
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Theelen
T, Meulendijks CFM, Geurts DEM, Leeuwen AV, Voet N B M, Deutn AF |
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Br J
Ophthalmol. 2004;88:1510-11. |
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Elevated intraocular
pressure (IOP) is generally accepted as
one of the primary risk factors for glaucoma. Accuracy of
IOP measurement may be altered by several factors, such
as breath holding, Valsalva manoeuvres, and tight
collars. Goldmann applanation tonometry is the
calculation method
used most widely. However, recent studies suggested that
IOP would not be calculated adequately if Goldmann
tonometry was applied on thin corneas. Tonometry by a portable electronic device (TonoPen), which appears to be of similar
reliability as the Goldmann method, is less dependent on
central corneal thickness because of a smaller area of
applanation. In addition, a portable system can be used independent from the patient’s pose. |
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The
purpose of this study was to evaluate whether
intraocular pressure (IOP) calculation by applanation
tonometry is determined more essentially by the
subject's neck position or by neck constriction. |
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Twenty three right eyes of 23 healthy subjects (12 male, 11 female)
were included. IOP was measured by applanation tonometry
with the TonoPen on sitting participants under four
different conditions: with open collar upright (A) or
with the head in the headrest of a slit lamp (B), with a
tight necktie upright (C) or in slit lamp position (D).
All measurements with neck constriction were performed 3
minutes after placing the necktie.
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Mean IOP was 16.9 (± 2.3) mm Hg (range 11-21 mm Hg) (A), 18.1 (±
2.2) mm Hg (range 14-22 mm Hg) (B), 17.9 (± 2.9) mm Hg
(range 12-25mmHg) (C) and 18.7 (± 2.7) mm Hg (range
13-24 mm Hg) (D). Mean IOP increased by 1.3 (SD 2.6) mm
Hg (p = 0.028, paired / test, range +0.2 to +2.4 mm Hg)
if subjects changed position from A to B. There was no
statistically significant difference between
measurements with or without neck constriction.
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Authors
concluded with remarks that an applanation tonometry may
be inaccurate if performed in slit lamp position. In
contrast, tight neckties do not significantly affect IOP
evaluation in healthy subjects |
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Is
screening for interferon retinopathy in hepatitis C
justified? |
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Cuthbertson
FM, Davies M, McKibbin M |
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Br J Ophthalmol.
2004;88:1518-20 |
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Hepatitis C is a blood borne
RNA virus that can cause chronic liver disease. In the
United Kingdom, the National
Institute for Clinical Excellence (NICE)
advocates treatment with a combination of
interferon alfa and ribavirin for patients with moderate to severe hepatitis C
infection. Treatment is recommended for all adults who
have not had previous interferon alfa monotherapy,
as well as for those who have had previous treatment
leading to an initial response and have then relapsed |
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Interferon associated retinopathy was
first described in 1990 by Ikebe et al. Features include
haemorrhages and cotton wool spots around the disc and
through the posterior pole, optic disc hyperaemia, and
macular oedema. In addition, fluorescein angiography may
demonstrate poorly perfused
areas of retina. The reported incidence of retinopathy
as a side effect of interferon varies widely in the
literature. There is some evidence to suggest that the incidence
of the retinopathy may be dose dependent. Treatment
regimens with subcutaneous doses of interferon varying
from 3xl06
units three times a week to 9xl06
units six times a week have been used for the hepatitis
viruses, with higher
doses used in the treatment of various malignancies.
Case series and reports have show increased incidence of
retinopathy in patients on higher more
frequent doses.
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Recently, a long acting form of interferon
alfa has developed,
known as pegylated or polyethylene glycol conjugated
interferon. This drug has slower absorption reduced volume of distribution, and lower elimination rates, as
well as showing a more sustained virological response. Plasma
levels of the drug are kept more stable, with a lower peak
level. The local treat-ment protocol in our area uses pegylated
interferon in combination with ribavirin. This encompasses a dose of 1.5 µg/kg of pegylated interferon, an average 70 kg person receiving 105 µg per week. The dose of ribavirin used is
also weight dependent with a total of 800 mg split over
the day for people weighing 30-64 kg, 1000 mg for 65-86
kg, and 1200 mg over 86 kg.
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The purpose of this study was to document the incidence and natural
history of the retinopathy in patients treated with a
long acting (pegylated) interferon and ribavirin for
hepatitis C and to assess the need to screen for retinal
complications.
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All patients started on treatment from September 2002 to August
2003 were invited to participate in the study. The past
medical and ocular history, visual symptoms, and the
results of a full ophthalmological assessment performed
3 months after starting treatment were noted. Any
patient with retinal changes was followed up at 3 month
intervals until the changes resolved.
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Of the 25 patients examined, four had evidence of retinopathy
including deep retinal haemorrhage and cotton wool
spots. Two of the patients were diabetic and one
hypertensive. None had any visual symptoms and in all
four the retinopathy resolved while the patients
completed their course of treatment.
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Authors concluded that the incidence of retinopathy with pegylated
interferon is low. The retinal complications resolve
while treatment is
continued and are asymptomatic. This study does not
support routine screening for retinopathy in patients
treated with pegylated interferon and ribavirin for
hepatitis C.
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Melanocytomas
of the optic disk
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Zografos L, Girard CBO, Desjardins L,
Schalenbourg A, Chamot L, Uffer S. |
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Am J
Ophthalmol. 2004; 138: 964-9. |
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Melanocytomas of the optic disc are benign tumors composed of large
deeply pigmented nevus cells, These tumors are typically
asymptomatic but sometimes show slow growth. In rare
cases, however, they can undergo malignant transformation
and can induce functional loss a attributable compressive
and vaso-occlusive phenomena or tumor necrosis.
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Melanocytomas occur generally in dark patients.
Because 40% to 50% of the cases of melanocytoma included
in statistical studies from the USA involve
Afro-American patients who rarely develop malignant
pigmented tumors.
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The purpose of this study was to evaluate
the various forms of clinical presentation, the
potential of growth, the risk of functional
loss and the possibility of malignant transformation of
optic disk melanocytomas in European patients.
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Evaluation
of 37 cases of optic disk melanocytomas identified in the
computer files of the ocular oncology unit of Jules
Gonin Hospital to determine the clinical presentation of
these tumors and the risk of complications. |
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The tumor was asymptomatic in 28 cases.
Visual acuity was normal in 26 cases, subnormal in 10 cases, and in one case it was reduced to 0.1. Visual field defects were
observed in 19 cases; the size and extent of the
tumor and the degree of papilledema appeared to
influence the severity of the visual field defect. Tumor
growth was demonstrated in 6 of the 9 cases in which
follow-up was for at least six years. In two cases there
was presumed
malignant transformation that was treated by
accelerated proton beam radiotherapy.
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Authors concluded
with remarks that melanocytomas in white Europeans and those of European derivation are rarely symptomatic, have only a moderate
effect on visual function and show a low rate of
progression over long observation. The risk of tumor progression, although sometimes
occurring as much as
several years after the initial diagnosis, justifies a
cautious approach with long-term regular surveillance of
these patients.
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Inter-eye
difference in diabetic macular edema after unilateral
intravitreal injection of triamcinolone
acetonide
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Jonas JB, Harder B,
Kamppeter BA |
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Am J Ophthalmol. 2004; 138: 970-7.
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Macular edema is one of the most important reasons for reduced
vision in patients with diabetic retinopathy. If there
is focal leakage of fluid
in the macular region, it can be treated by focal argon laser
coagulation of the leaking retinal area. If capillary leakage
and macular edema diffusely involve the posterior pole
of the fundus, the therapeutic value of scattered laser
coagulation of the macula has not conclusively shown
yet. Recent studies have suggested that intravitreal
triamcinolone acetonide may lead to a reduction of
macular edema, and depending on the degree of macular
ischemia, to an increase in visual acuity. These studies
were either case reports or non-comparative series
studies without control groups, or they did not clearly
reveal a significant change in visual acuity despite a
significant reduction of macular edema after an
intravitreal injection of 4 mg triamcinolone acetonide.
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The
purpose of this study was to report on visual outcome of
patients receiving intravitreal triamcinolone acetonide
for treatment of diffuse diabetic macular edema |
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The study included 25 consecutive patients (50 eyes)
with bilateral diabetic macular edema. Unilateral
intravitreal injection of about
20 mg triamcinolone acetonide into the eye (study group)
more severely affected by diabetic maculopathy. The
contralateral eyes served as control group. Mean follow-up was 7.1 ± 4.1 months.
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In the study group, visual acuity increased significantly (P <
.001) by 3.0 ± 2.6 Snellen lines to a peak
at two to six months after the injection, and decreased
significantly (P = .001) towards the end of follow up.
At the end of follow-up, visual acuity was higher,
not significantly (P = .18) higher, than at baseline.
An increase in visual acuity was found in 23 eyes (92%).
In the control group, differences between visual acuity at baseline and at any of the re-examinations during
follow-up were not significant (P > .10). In an intra-individual inter-eye comparison, gain in visual acuity was
significantly (P < .05) higher in the injected eyes,
for the measurements obtained up to four months after
injection.
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Authors concluded that with remarks that
intravitreal triamcinolone acetonide may
temporarily increase visual acuity in eyes with diabetic macular edema.
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