Article

Prevalence of undercorrection of refractive error in rural Central India The Central India eye and medical study

Suraj Eye Institute, Nagpur, Maharashtra, India Department of Ophthalmology, Medical Faculty Mannheim of the Ruprecht-Karls-University Heidelberg, Mannheim, Germany.
Acta ophthalmologica (Impact Factor: 2.84). 04/2011; 90(2):e166-167. DOI: 10.1111/j.1755-3768.2010.02073.x
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Available from: Vinay Nangia, Aug 04, 2015
The International Standards Organi-
zation (ISO) permits a defined range
of error in the accuracy of loading
according to their nominal capacity or
the size of the syringe. The conven-
tional capacity tolerance of any
syringe is defined by the sum of its
nominal maximal capacity V1 and the
actually expelled volume V2. For
example, if a 1.0-cc syringe is filled up
to the 0.05-ml graduation line for an
IVT, the tolerance for nominal capac-
ity V1 is 1.5% and the tolerance for
the expelled volume V2 is 2% [Erstad
et al. 2006]. IVT in ophthalmology
are mainly performed using 1.0-cc
syringes, which are frequently filled by
0.05 ml. The calculated tolerance
for an intravitreal injection of 0.05 ml
applied in a 1.0-cc syringe is (1.0 ml ·
0.015) + (0.05 ml · 0.02) = 0.016 ml.
Thus, the calculated standard variance
of the actual volume of 0.05 ml of
ranibizumab follows the equation
0.05 ± 0.016 or an applied volume
between 0.034 and 0.066 ml. Our
experimental results highly agree with
these calculations. Following this
assumption and a known specific
weight of 1.04 mg ml for ranibizumab
would imply an actual delivered mean
dose of (0.5375 ml · 1.04 mg ml) =
0.58 mg ± 0.17 (range 0.41 ) 0.75 mg)
ranibizumab per injection.
Gerding & Timmermann (2010)
analyzed the accuracy and precision of
0.5 mg dose ranibizumab injections.
The application was performed in 3
different modes: 1) after preadjustment
of the desired dose in the syringes with
normal (PA) and 2) with forced injec-
tion (PAF), and 3) by differential
volume reduction from an overdose
filled syringe (DI). The mean injection
of DI mode was 0.5059 mg (95% confi-
dence interval [CI]: 0.4903 ) 0.5214).
PA resulted in a lower dose (mean:
0.4542, CI: 0.4339 ) 0.4744) and the
PAF mode in a higher dose (0.5335,
CI: 0.5130 ) 0.5540). They concluded
that the routinely used Lucentis injec-
tion sets results in a relatively uncon-
trolled application of ranibizumab
doses and recommended to use smaller
syringes, thus confirming the estab-
lished ISO standard range of error for
the loading, which primarily depends
on size of a syringe. For example, if a
0.5-ml syringe is filled by 0.05 ml, the
calculated tolerance is (0.5 ml ·
0.0075)+(0.05 ml · 0.01)=0.00875 ml.
Thus, the calculated standard variance
of the actual volume of 0.05 ml in
a 0.5-cc syringe follows the equation
0.05 ± 0.0087 ml or an applied vol-
ume between 0.0413 and 0.0587 ml. All
these examples demonstrate that the
accuracy and precision of the current
manual approach to prepare the cor-
rect dose in a syringe remain limited.
In conclusion, treating physicians
need confidence that the intended dos-
age of the drug is actually delivered
[Wolf et al. 2010]. However, we deter-
mined a significant variance in the
accuracy, precision and repeatability
to prepare a proposed dose for IVT.
Our findings may have potentially
important clinical implications as our
data indicate a considerable variation
of the applied mass using the standard
equipment for IVT.
References
Erstad AJ, Erstad BL & Nix DE (2006):
Accuracy and reproducibility of small-vol-
ume injections from various-sized syringes.
Am J Health Syst Pharm 63: 748–750.
Gerding H & Timmermann M (2010): Accu-
racy and precision of intravitreally injected
ranibizumab doses: an experimental study.
Klin Monbl Augenheilkd 227: 269–272.
Meyer CH, Krohne TU & Holz FG (2010):
Concentrations of unbound bevacizumab
in the aqueous of untreated fellow eyes
after a single intravitreal injection in
humans. Acta Ophthalmol. [Epub ahead of
print].
Raju JR & Weinberg DV (2002): Accuracy
and precision of intraocular injection vol-
ume. Am J Ophthalmol 133: 564–566.
Wolf A, Gandorfer A, Haritoglou C, Koller
C, Thalmeier A & Kampik A (2010):
Volumenberechnungen zur aktuellen intra-
vitrealen Injektion von Lucentis. Ophthal-
mologe 107: 435–438.
Correspondence:
Carsten H. Meyer
Department of Ophthalmology
University of Bonn
Ernst-Abbe-Street 2
53127 Bonn
Germany
Email: meyer_eye@yahoo.com
Prevalence of
undercorrection of
refractive error in rural
Central India
The Central India eye and
medical study
Vinay Nangia,
1
Jost B. Jonas,
1,2
Ajit
Sinha,
1
Rajesh Gupta
1
and Krishna
Bhojwani
1
1
Suraj Eye Institute, Nagpur, Maha-
rashtra, India
2
Department of Ophthalmology, Medi-
cal Faculty Mannheim of the Ruprecht-
Karls-University Heidelberg, Mannheim,
Germany
doi: 10.1111/j.1755-3768.2010.02073.x
Vinay Nangia and Jost B. Jonas contributed
equally to this work.
Fig. 3. The repeatability among all 11 partici-
pants had a mean accuracy of 4.8 mg ±3.1.
There was no statistical difference in the
reproducibility between both groups.
Fig. 4. In reference to an expected mass of
50 mg or 0.05 ml distilled water our measure-
ments determined a mean of 53.75 mg dis-
tilled water (range 24.6–65.5 mg) with a
normal distribution of measured values for
all 11 participants (440 syringes). Forty four
samples contained less than 47 mg, 52 sam-
ples more than 60 mg.
Acta Ophthalmologica 2012
e166
Page 1
Dear Editor
O
ne of the most frequently
encountered reasons for visual
impairment has been undercorrection
of refractive errors (Klaver et al. 1998;
Xu et al. 2006; Gunnlaugsdottir et al.
2010). As frequency and reasons of
visual impairment may differ between
regions and populations, it was the
purpose of the present study to evalu-
ate the frequency of undercorrection
of refractive errors in an adult rural
population in Central India.
The Central India Eye and Medical
Study (CIEMS) is a population-based
cross-sectional study in Central India.
The Medical Ethics Committee of the
Medical Faculty Mannheim of the
Ruprecht-Karls-University Heidelberg
and the ethical committee of Suraj
Eye Institute Nagpur approved the
study, and all participants gave
informed consent, according to the
Declaration of Helsinki. Inclusion cri-
terion was an age of 30+ years. The
study included 4711 participants. The
response rate was 80.1%. All examin-
ations were carried out in the hospital.
The study design was described in
detail recently (Jonas et al. 2009; Nan-
gia et al. 2010). We measured uncor-
rected visual acuity, visual acuity with
the subjects’ glasses (habitual visual
acuity) and best corrected visual acu-
ity. Undercorrected refractive error
was defined as an improvement in pre-
senting or habitual visual acuity of
the better eye by at least two lines
with best refractive correction.
Visual acuity measurements were
available for 4699 (99.7%) subjects.
The mean age was 59.5 ± 13.4 years
(range: 30–100 years). An undercor-
rection of refractive error was detected
in 1588 subjects. The rate of undercor-
rection was 33.8 ± 0.07% (95% con-
fidence interval: 32.4, 35.2). In
multivariate analysis, refractive under-
correction was significantly associated
with higher age (p < 0.001; odds
ratio (OR): 1.06 (95% CI: 1.05, 1.07),
female gender (p < 0.001; OR: 1.41
(95% CI: 1.20, 1.67), lower level of
education (p < 0.001; OR: 0.87 (95%
CI: 0.81, 0.93), higher hyperopic
refractive error (p = 0.001; OR: 1.09
(95% CI: 1.04, 1.14), higher corneal
refractive power (p = 0.006; OR: 1.09
(95% CI: 1.05, 1.07), and higher astig-
matic refractive error (p < 0.001; OR:
2.15 (95% CI: 1.92, 2.40). It was no
longer significantly associated with
best corrected visual acuity, axial
length, anterior chamber depth, lens
thickness, and central corneal thick-
ness. Among the subjects with under-
correction, 38.1% of the subjects were
myopic (i.e. a myopic refractive error
of more than )0.50 dioptres). Using
the World Health Organization
(WHO) definition of visual impair-
ment and blindness for habitual visual
acuity, 819 (51.6%) subjects out of
the 1588 subjects with refractive un-
dercorrection had visual impairment
(habitual visual acuity in the better
eye <20 60 and 20 400). One sub-
ject fulfilled the criteria of blindness
(habitual visual acuity <20 400).
After best correction of the refractive
error, 120 (14.6%) subjects out of the
820 subjects with visual impairment or
blindness (based on the habitual visual
acuity) remained visually impaired.
For all other 700 (85.6%) subjects,
best corrected visual acuity in the bet-
ter eye was higher than 20 60.
In conclusion, the rate of refractive
undercorrection was 33.8 ± 0.07% in
rural Central India. Refractive under-
correction was significantly associated
with higher age, female gender, lower
level of education, hyperopic refrac-
tive error , corneal refractive power
and higher astigmatic refractive error.
About 50% of the subjects with
refractive undercorrection were visu-
ally impaired. After supplying best
possible correction of the refractive
error, 85% the subjects with habitual
visual impairment were no longer
visually impaired. It may show that
refractometry and supplying adequate
glasses may be the most efficient and
cheapest way to reduce the prevalence
of visual impairment in rural Central
India.
References
Gunnlaugsdottir E, Arnarsson A & Jonasson
F (2010): Five-year incidence of visual
impairment and blindness in older Iceland-
ers: the Reykjavik Eye Study. Acta Oph-
thalmol 88: 358–366.
Jonas JB, Nangia V, Matin A, Kulkarni M &
Bhojwani K (2009): Prevalence of keratoc-
onus in rural Maharashtra in Central
India: the Central India Eye and Medical
Study. Am J Ophthalmol 148: 760–765.
Klaver CC, Wolfs RC, Vingerling JR, Hof-
man A & de Jong PTVM (1998): Age-spe-
cific prevalence and causes of blindness and
visual impairment in an older population:
the Rotterdam Study. Arch Ophthalmol
116: 653–658.
Nangia V, Jonas JB, Sinha A, Matin A &
Kulkarni M (2010): Refractive error in
Central India. The Central India Eye and
Medical Study. Ophthalmology 117: 693–
699.
Xu L, Li J, Cui T & Jonas JB (2006): Fre-
quency of undercorrected refractive error
in elderly Chinese in Beijing. Graef Arch
Clin Exp Ophthalmol 244: 871–873.
Correspondence:
Dr. Vinay Nangia
Suraj Eye Institute
Plot No 559 New Colony
Nagpur, 440004
Maharashtra
India
Tel: 0091 712 2595600
Fax: 0091 712 2595796
Email: nagpursuraj@gmail.com
Acta Ophth almologica 2012
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