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Visual acuity outcomes following cataract extraction

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Visual acuity outcomes following cataract extraction

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VISUAL ACUITY OUTCOMES FOLLOWING CATARACT EXTRACTION
IN ADULT LATINOS: THE LOS ANGELES LATINO EYE STUDY

by

Kashif Mazhar

_____________________________________________________________

A Thesis Presented to the
FACULTY OF GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE
(APPLIED BIOTSTATISTICS AND EPIDEMIOLOGY)

August 2007

Copyright 2007 Kashif Mazhar

ii

Dedication

Dedicated to my parents (M.M.Haque and Kausar Jabeen) for always being
there for me and to Dr Stanley.P.Azen for his support and trust.

iii

Acknowledgements

To my co-authors Anne, Joanne Wu, Dr Stanley.P.Azen and Dr Rohit Varma.

iv

Table of Contents

Dedication ii

Acknowledgements iii

List of Tables v

Abstract vi

Introduction 1

Materials and Methods 3

Results 7

Discussion 16

Conclusion 22

Bibliography 23

v
List of Tables

Table 1a Visual Impairment in Worse Seeing
Cataract-Operated Eyes
13

Table 1b Visual Impairment in All Cataract-Operated
Eyes
14

Table 2a. Primary Cause of Visual Impairment in
Worse Seeing Cataract- Operated Eye

15

Table 2b. Primary Cause of Visual Impairment in All
Cataract-Operated Eyes

16

.

vi

Abstract
Purpose: To determine prevalence, primary causes, and risk indicators of
visual impairment (VI) in cataract-operated eyes.
Methods: Participants with cataract extraction underwent an in-home
interview and a comprehensive ophthalmologic examination. VI in the
cataract-operated eye was defined by: presenting visual acuity (PVA)<20/40
or best corrected visual acuity (BCVA)<20/40. The association of cataract
extraction status (aphakic, pseudophakic) and severity of VI was evaluated.
Risk indicators associated with VI by BCVA in the worse seeing cataract-
operated eye were evaluated.
Results: The prevalence of VI was 32.2% defined by BCVA vs. 48.1%
defined by PVA in all cataract-operated eyes. Uncorrected refractive error,
age-related macular degeneration and diabetic retinopathy were the major
primary causes of VI. History of glaucoma, barriers to eye care, and
unmarried participants were independent risk indicators associated with VI
(p<0.05).
Conclusions: Despite cataract surgery, a significant proportion of participants
had residual visual impairment demonstrating the need for regular
ophthalmologic exams in cataract-operated patients.
1

Introduction

Cataract is one of the principal causes of blindness in the world
19
and
is the leading cause of visual impairment in the United States (U.S.) among
Caucasians, African Americans and Latinos.
7
Since Latinos comprise the
fastest growing segment of the U.S. population, it is important to examine the
role of cataract in their visual health. According to Census 2000 data, 12% of
the residents in the U.S. are Latino or Hispanic, and by 2050 this number is
projected to grow to 25%.
23
A recent population-based study found the
prevalence of all lens changes to be as high as 19.5% in Latinos 40 years
and older,
27
and another study found that cataract and glaucoma are the
primary causes of vision loss in Latinos in the U.S.
16
Since the median age in
Latinos is 10 years less than that of the rest of the U.S. population, we must
plan in advance for healthcare as this population ages. To do so efficiently,
we need to assess not only the prevalence but also the outcomes of cataract
surgery in Latinos.
In 1999, 1.6 million cataract procedures costing $3 billion were
performed on Medicare beneficiaries. Cataract care consumes
approximately 60% of Medicare’s budget for vision and 12% of their total
budget.
6
Despite the enormous cost and burden of cataract surgery, there
are few population-based studies that evaluate postoperative visual
2
impairment and causes of visual impairment in cataract-operated
individuals. Most of these studies have been conducted in developing
countries.
3, 9,11,17, 20
To the best of our knowledge, there has been no such
study of the Latino population despite recent reports demonstrating that the
prevalence of pseudophakia / aphakia is higher in Hispanics than in
Caucasians or African Americans.
8
Therefore, it is important to evaluate the
visual acuity outcomes following cataract extraction in adult Latinos.
The Los Angles Latino Eye Study (LALES) is a population-based,
cross-sectional study that examines the prevalence of ocular disease, visual
impairment, and related risk indicators in Latinos, 40 years and older living in
Los Angeles County, California. The objectives of this article are: (1) to
compare the prevalence of visual impairment in cataract-operated
participants defined by presenting visual acuity and best corrected visual
acuity; (2) to assess the causes of visual impairment by best corrected visual
acuity in cataract-operated participants; (3) to determine the risk indicators
for visual impairment in cataract-operated participants.

3

Material and Methods

Study Population. The study population included self-identified Latinos 40
years and older living in La Puente, California. Six census tracts of La
Puente were chosen because they are representative of the demographic
and socioeconomic characteristics of the Latino population of Mexican origin
in Los Angeles County, California and the U.S. Details of the study design,
sampling plan and baseline data are presented elsewhere.
24
Briefly, between
February 2000 and May 2003, eligible residents were given information
about the study and invited to participate in the study. Prior to any data
collection, a written informed consent was obtained from each study
participant. Approval for conducting the study was obtained from the Los
Angeles County/University of Southern California Medical Center Institutional
Review Board. All study procedures adhered to the principles outlined in the
Declaration of Helsinki for research involving human subjects.
Sociodemographic and Clinical Examination Data. Details of the in-home
interview and clinical examination are presented elsewhere.
24
After obtaining
an informed consent from the participant, a trained interviewer conducted a
detailed in-home interview to obtain demographic information, risk factors,
history of ocular and medical conditions, access to care, acculturation and
insurance status. Barrier to care was measured by a one item questionnaire:
4
“During the past 12 months, was there any time when you needed eye care
or surgery but did not get it?” Eligible individuals were then scheduled for a
comprehensive eye examination at the LALES local eye examination center,
performed by an ophthalmologist and ophthalmic technicians. Presenting
visual acuity (PVA) and best corrected visual acuity (BCVA) were measured
according to the Early Treatment Diabetic Retinopathy Study (ETDRS)
protocol. Presenting visual acuity was measured for each eye (right eye first
followed by left eye) with the individual’s existing refractive correction at 4
meters. The ETDRS protocol was used with a retro illuminated, modified
ETDRS distance chart. PVA was scored as the total number of lines read
correctly. Near vision was measured with the participant’s present reading
prescription using the modified ETDRS near vision acuity chart.
Definitions of Visual Impairment. Visual impairment in the cataract-
operated eye was defined by two criteria: 1) a PVA of 20/40 or worse, or 2) a
BCVA of 20/40 or worse. The severity of visual impairment was classified as:
mild (20/40-20/63), moderate (20/80-20/160) and severe ( ≤20/200).
Determination of Primary Causes of Visual Impairment. Details of the
procedures to determinate the primary causes of visual impairment are
presented elsewhere.
4
Using standard clinical criteria, a thorough chart
review of all available clinical data was conducted, including clinical
examination findings, lens grading, fundus photographs, and all information
provided by the examining ophthalmologist, and a final determination of the
5
cause of vision loss for each eye was made. In addition to ocular diseases
being considered as the primary causes of visual impairment, uncorrected
refractive error was also considered as a cause. Uncorrected refractive error
in cataract operated eye was defined as visual acuity ≤20/40 by PVA but
visual acuity >20/40 by BCVA.
Determination of Risk Indicators for Visual Impairment. Anderson’s
Behavioral Model was used to evaluate the risk indicators for visual
impairment.
1, 2
This model suggest people’s use of health services is a
function of their predisposition to use services measured by demographic
and social factors; enabling factors that facilitate or impede use and need for
services as perceived by people or evaluated by health professional.
Predisposing variables include age, gender, marital status (married and living
with partner, not married or not living with partner), acculturation score, birth
place (US born, foreign born), generation status and language preference.
The enabling variables include education, income, and insurance status. The
need variables include distance vision, near vision, barrier to care and history
of eye disease.
Impact of Visual Impairment on Daily Living: Driving difficulties subscale
scores of National Eye Institute-Visual Function Questionnaire (NEI-VFQ-25)
were used as a surrogate to evaluate the impact of visual impairment on
activities of daily living. NEI-VFQ-25 questionnaire was administered either in
6
English or Spanish, according to participant’s language preference. Details
of the questionnaire and interviewers are presented elsewhere.
10, 24

Statistical Analysis. The prevalence of visual impairment defined by PVA
and BCVA were calculated for both the worse seeing cataract-operated eye
and all cataract-operated eyes. Chi-square analyses were conducted to
evaluate the associations of cataract extraction status
(aphakic/pseudophakic) with visual impairment (none, any visual
impairment). The causes of visual impairment defined by PVA were
assessed for the worse seeing cataract-operated eye and all cataract-
operated eyes. The worse seeing cataract-operated eye is defined according
to the following criteria: 1) eye with unilateral cataract extraction; or 2) eye
with worse visual acuity in bilateral cataract extractions.
Univariate and stepwise logistic regressions analyses were conducted to
assess the risk factors associated with visual impairment defined by BCVA in
the worst seeing cataract-operated eye. Analysis of covariance was used to
compare the driving difficulty subscale scores of NEI-VFQ-25 between
bilateral phakic with no visual impairment (i.e. all the LALES participants with
no cataract extraction and no visual impairment), bilateral pseudophakic with
no visual impairment, and bilateral pseudophakic with any visual impairment.
All analyses were performed using SAS statistical package (version 9.1, SAS
Institute Inc, Cary, N.C.) at the 0.05 significance level.
7

Results

Description of Study Cohort. Of the 7789 eligible participants identified for
LALES, 6357 completed the ophthalmic examination, resulting in a
participation rate of 82% (6357/7789). Of these 6357 participants, 265 (4.2%)
had at least one cataract extraction, of which 4 participants, who did not have
visual acuity data, were excluded from the analysis. Of the 261 participants,
100 (38%) participants had a unilateral cataract extraction (18 aphakic and
82 pseudophakic), and 161 (62%) participants had bilateral cataract
extractions (3 bilateral aphakic, 153 bilateral pseudophakic, and 5 aphakic in
one eye and pseudophakic in the other eye) resulting in a total of 422
cataract-operated eyes. Overall, 181 (69%) participants with cataract
extractions wore spectacles at the time of clinical examination, of these 11
(6%) were unilateral aphakic, 57 (31%) were unilateral pseudophakic, 3 (2%)
were bilateral aphakic, 108 (60%) were bilateral pseudophakic, and 2 (1%)
were bilateral cataract extractions with one eye aphakic and the other eye
pseudophakic.
Prevalence of Visual Impairment. Table 1a presents visual impairment
defined by PVA and BCVA in worst seeing cataract operated eyes. Among
the 261 cataract-operated participants, 158 (60.5%) had some form of visual
impairment defined by PVA, compared to 107 (41.0%) defined by BCVA for
8
distance vision. There was a higher proportion of visual impairment in all the
three visual impairment severity groups (mild, moderate, severe) when visual
impairment was defined by PVA as compared to when visual impairment was
defined by BCVA for distance vision.
Visual impairment defined by either PVA or BCVA was more prevalent
in the aphakic group compared to the pseudophakic group (p<0.0001); PVA
(96.0% vs. 56.8%); BCVA (88.0% vs. 36.0%) for distance vision. Moreover,
92% of aphakic and 14.4% of pseudophakic participants had severe visual
impairment (which met the U.S. definition of blindness) defined by PVA
compared to 72% aphakic and 10.6% pseudophakic participants defined by
BCVA.
Among the 259 cataract operated participant who had near vision
visual acuity data, 248 (95.8%) had some form of visual impairment defined
by PVA. Aphakics had a higher prevalence of visual impairment for near
vision compared to pseudophakics (100% vs 95.3%). Chi-square analyses
of the association of status of cataract extraction (aphakic, pseudophakic)
and visual impairment (no visual impairment vs. any visual impairment) were
significant for visual impairment defined either by PVA or BCVA for distance
vision and PVA for near vision (all p<0.0001).
Table 1b presents visual impairment defined by PVA and BCVA in all
cataract operated eyes. Of the 422 total cataract-operated eyes, 203 (48.1%)
eyes had any visual impairment defined by PVA, compared to 136 (32.2%)
9
cataract-operated eyes defined by BCVA for distance vision. Visual
impairment defined by either PVA or BCVA was more prevalent in the
aphakic eyes compared to the pseudophakic eyes (p<0.0001) for distance
vision. Of the 420 cataract operated eyes which had near vision visual acuity
data, 391 (93.1%) had visual impairment defined PVA.
Causes of Visual Impairment. As shown in Table 2a, the three major
primary causes of visual impairment in the worse seeing cataract-operated
eyes were uncorrected refractive error (27.2%), age-related macular
degeneration (AMD) (12.0%), and diabetic retinopathy (10.1%). This was
followed by, in descending order, corneal opacity (8.2%), posterior capsular
opacification (7.0%), open angle glaucoma (5.1%), retinal disorders other
than retinal detachment (5.1%), retinal detachment (3.8%), myopic
degeneration (3.8%), other eye disorders (1.9%), and amblyopia (0.6%).
Table 2b presents the primary cause of visual impairment in all
cataract-operated eyes. The three major primary cause of visual impairment
in all cataract operated eyes are the same as those in worse seeing cataract
operated eyes, which are uncorrected refractive error (33%), AMD (13.3%),
and diabetic retinopathy (10.8%).

10

Table 1a. Visual Impairment in Worse Seeing Cataract-Operated Eyes

Visual Impairment
*
Status of
Cataract
Extraction
None
(>20/40)
Any
( ≤20/40)
Mild
(20/40-
20/63)
Moderate
(20/80-
20/160)
Severe
( ≤20/200)
Visual Impairment Defined by Presenting Visual Acuity (PVA)
Aphakic
(n=25) 1(4.0) 24 (96.0) 0 (0) 1 (4.0) 23 (92.0)

Pseudophakic
(n=236) 102 (43.2) 134(56.8) 69 (29.2) 31 (13.1) 34 (14.4)
Total
(n=261) 103 (39.5) 158(60.5) 69 (26.4) 32 (12.3) 57 (21.8)
Visual Impairment Defined by Best Corrected Visual Acuity (BCVA)
Aphakic
(n=25) 3 (12.0) 22 (88.0) 4 (16.0) 0 (0) 18 (72.0)

Pseudophakic
(n=236) 151 (64.0) 85 (36.0) 40 (16.9) 20 (8.5) 25 (10.6)
Total
(n=261) 154 (59.0) 107(41.0) 44 (16.9) 20 (7.7) 43 (16.5)

Note: Data are presented as number (percentage). Chi-square tests of the association of
status of cataract extraction (aphakic, pseudophakic) and visual impairment (none vs. any
visual impairment) are significant (p<0.0001) for visual impairment defined by both
presenting and best corrected visual acuities.
*
Visual impairment was defined as presenting or best-corrected visual acuity of 20/40 or
worse in the worse seeing cataract-operated eye.

11
Table 1b. Visual Impairment in All Cataract-Operated Eyes

Visual Impairment*
Status of
Cataract
Extraction

None
(>20/40)
Any
( ≤20/40)
Mild
(20/40-
20/63)
Moderate
(20/80-
20/160)
Severe
( ≤20/200)
Visual Impairment Defined by Presenting Visual Acuity (PVA)
Aphakic
(N=29)
3 (10.3) 26(89.7) 0 (0.0) 1 (3.5) 25 (86.2)
Pseudophakic
(N=393)
216(55.0) 177(45.0) 96(24.4) 37 (9.4) 44 (11.2)
Total (N=422) 219(51.9) 203(48.1) 96 (22.8) 38 (9.0) 69 (16.4)
Visual Impairment Defined by Best Corrected Visual Acuity (BCVA)
Aphakic
(N=29)
6 (20.7) 23 (79.3) 4 (13.8) 0 (0.0) 19 (65.5)
Pseudophakic
(N=393)
280(71.3) 113(28.8) 53 (13.5) 26 (6.6) 34 (8.7)
Total (N=422) 286(67.8) 13 (32.2) 57 (13.5) 26 (6.2) 53 (12.6)

Note: Data are presented as number (percentage). Chi-square tests of the
association of status of cataract extraction (aphakic, pseudophakic) and the
severity of visual impairment (none vs. any visual impairment ) are significant
(all p<0.0001) for visual impairment defined by both presenting and best
corrected visual acuities.

*
Visual impairment was defined as presenting or best-corrected visual acuity
of 20/40 or worse in the cataract-operated eyes.

12
Table 2a. Primary Cause of Visual Impairment in Worse Seeing
Cataract-Operated Eye.

Visual Impairment in Worse Seeing
Cataract-Operated Eye*

Primary Cause of
Visual Impairment Mild
(20/40-
20/63)
Moderate
(20/80-
20/160)
Severe
(<=20/200)

TOTAL
Uncorrected Refractive
Error†
36 (52.2) 5 (15.6) 2 (3.5) 43 (27.2)
Age Related Macular
Degeneration
6 (8.7) 3 (9.4) 10 (17.5) 19 (12.0)
Diabetic Retinopathy 2 (2.9) 9 (28.1) 5 (8.8) 16 (10.1)
Corneal Opacity 2 (2.9) 4 (12.5) 7 (12.3) 13 (8.2)
Posterior Capsular
Opacification
6 (8.7) 2 (6.3) 3 (5.3) 11 (7.0)
Open Angle Glaucoma 3 (4.4) 2 (6.3) 3 (5.3) 8 (5.1)
Other Retinal Disorders 1 (1.5) 2 (6.3) 5 (8.8) 8 (5.1)
Retinal Detachment 0 (0.0) 1 (3.1) 5 (8.8) 6 (3.8)
Myopic Degeneration 1 (1.5) 1 (3.1) 4 (7.0) 6 (3.8)
Other 0 (0.0) 1 (3.1) 2 (3.5) 3 (1.9)
Amblyopia 0 (0.0) 0 (0.0) 1 (1.8) 1 (0.6)
Unknown 12 (17.4) 2 (6.3) 10 (17.5) 24 (15.2)
Note: Data are presented as number (percentage).
* Severity of visual impairment was determined by presenting visual acuity in
worse seeing cataract-operated eye.
† Uncorrected refractive error was defined as cataract-operated eye has
visual impairment when measured by PVA (visual acuity ≤20/40), but no
visual impairment when measured by BCVA (visual acuity >20/40).

13
Table 2b. Primary Cause of Visual Impairment in All Cataract-
Operated Eyes
Visual Impairment
Primary cause of Visual
Impairment
Mild
(20/40-
20/63)
Moderat
e
(20/80-
20/160)
Severe
(<=20/200)

Total
Uncorrected Refractive
Error
57 (59.4) 7 (18.4) 3 (4.4) 67 (33.0)
Age Related Macular
Degeneration
8 (8.3) 5 (13.2) 14 (20.3) 27 (13.3)
Diabetic Retinopathy 5 (5.2) 10 (26.3) 7 (10.1) 22 (10.8)
Unknown 5 (5.2) 1 (2.6) 12 (17.4) 18 (8.9)
Corneal Opacity 3 (3.1) 5 (13.2) 8 (11.6) 16 (7.9)
Posterior capsular
opacification
9 (9.4) 3 (7.9) 3 (4.4) 15 (7.4)
Glaucoma 5 (5.2) 2 (5.3) 4 (5.8) 11 (5.4)
Other Retinal Disorders 2 (2.1) 2 (5.3) 5 (7.3) 9 (4.4)
Myopic Degeneration 1(1.0) 1 (2.6) 5 (7.3) 7 (3.5)
Retinal Detachment 0 (0.0) 1 (2.6) 5 (7.3) 6 (3.0)
Other 1 (1.0) 1 (2.6) 2 (2.9) 4 (2)
Amblyopia 0 (0.0) 0 (0.0) 1 (1.5) 1 (0.5)

Note: Data are presented as number (percentage).
* Severity of visual impairment was determined by presenting visual acuity in
worse seeing cataract-operated eye.
† Uncorrected refractive error was defined as cataract-operated eye has
visual impairment when measured by PVA (visual acuity ≤20/40), but no
visual impairment when measured by BCVA (visual acuity >20/40).

14
The Association of Risk Indicators and Visual Impairment. In the
univariate analyses for the predictors of visual impairment defined by BCVA
in the worse seeing cataract-operated eye education, significant risk
indicators were: marital status, history of glaucoma, history of AMD, not
getting needed glasses, not getting needed eye care, and number of visits for
eye care in last 12 month (all p<0.05). These variables were then candidates
for the stepwise logistic regression, which revealed that three of them were
significant independent indicators of visual impairment defined by BCVA in
the worse seeing cataract-operated eye. First, the participants with a self-
reported history of glaucoma were approximately three times more likely to
have visual impairment in cataract-operated eyes compared to participants
who did not have glaucoma (OR=2.9, 95% CI=1.3-6.7). Second, participants
who reported having a barrier to care were more than two times as likely to
have visual impairment in cataract-operated eyes compared to participants
who did not have a barrier to care (OR=2.6, 95% CI =1.1-6.2). Third,
participants who were not married or were not living with their partners were
almost two times more likely to have visual impairment compared to
participants who were married and living with their partners (OR=1.9, 95%
CI= 1.01-3.4). There were no statistically significant interactions between the
risks indicators included in the model.
Impact of Visual Impairment on Daily Life Activities. The covariate
adjusted mean scores for driving difficulties from the NEI-VFQ-25
15
questionnaire were lower for bilateral pseudophakics with visual
impairment (mean=59.3, standard error=4.7) compared to bilateral
psueudophakics with no visual impairment (mean=80.7, standard error=2.1)
or compared to LALES participants with bilateral aphakia and no visual
impairment (mean=89.2, standard error=0.3) (p<0.05). The mean scores
were adjusted for number of co morbidities, sex and income.

16
Discussion

LALES is the largest U.S. population-based survey of eye disease in any
racial/ethnic group. The participation rate of 82% in the LALES study is
comparable to other population-based studies.
13-15, 28
To the best of our
knowledge, there is no published data on prevalence of visual impairment,
causes of visual impairment, and risk indicators for visual impairment in
cataract-operated eyes among the Latino population.
The prevalence of any visual impairment defined by PVA among the
cataract operated LALES participants is similar to those found in recent
population-based surveys in several countries.
5, 11,17, 20
The difference in the
prevalence of visual impairment defined by BCVA compared to PVA
indicates that visual impairment in 15 to 20% of the cataract-operated
participants can be improved by refractive correction alone. A chart review
revealed that 16% of aphakic participants were not wearing corrective lenses
at the time of clinical examination. Improper use of appropriate aphakic
spectacles could result in visual impairment in aphakic participants. Among
the pseudophakic participants, the prevalence of any visual impairment in the
worse seeing cataract-operated eye changed from 56.8% as defined by PVA
to 36 % as defined by BCVA, a difference of about 20%. This emphasizes
the need to ensure that the implanted intra-ocular lens is of appropriate
power and that post-operative pseudophakic cataract patients obtain
17
corrective lenses when necessary. However, among aphakic participants,
the prevalence of any visual impairment changed from 96% as defined by
PVA to 88% as defined by BCVA, a difference of only 8%. This indicates
that a significant portion of visual impairment among aphakics is due to
reasons other than refractive error. Overall, the prevalence of visual
impairment in pseudophakic participants is lower than in aphakic participants
indicating that pseudophakics have better visual acuity outcomes after
cataract extraction. This is similar with the findings by other studies.
18, 22, 23,
Although PVA is most indicative of an individual’s visual acuity while
performing daily activities, the use of BCVA to define visual impairment not
only provides information on the degree of improvement that can be
expected from refractive correction but also makes possible the comparative
evaluation of aphakic and pseudophakic participants by ensuring that there
will be no further improvement in visual acuity by refraction alone. The
absence of published data for near vision outcome after cataract surgery in
population-based studies makes it difficult for us to compare it other ethnic
populations.
The most common causes of visual impairment other than
uncorrected refractive errors in cataract-operated participants were AMD
followed by diabetic retinopathy, corneal opacity, posterior capsular
opacification, glaucoma and retinal disorders other than retinal detachment.
This correlates with the high prevalence of AMD (9.7% individuals showed
18
evidence of early AMD and 0.5% of advanced AMD) and diabetic
retinopathy (47% of individuals with definite diabetes mellitus) in a
population-based study of Latinos in Los Angeles.
25, 26
In addition, previous
studies have shown the most common causes of low vision to be cataract,
diabetic retinopathy and ARMD in the overall LALES cohort.
4
Uncorrected
refractive errors and posterior capsular opacification accounted for almost
40% of primary cause of visual impairment in the cataract-operated
participants. Uncorrected refractive errors can be treated easily in cataract-
operated participants by providing corrective lenses. Posterior capsular
opacification is a well-recognized, vision-impairing complication of cataract
extraction that is usually identified during a routine ophthalmologic exam and
can be resolved easily with a YAG laser capsulotomy. It can be difficult for a
patient to appreciate the difference between visual impairment due to failure
of cataract surgery and visual impairment due to undetected, co-existing or
new onset ocular pathology. The patient may mistakenly attribute visual
impairment to failure of cataract surgery and not seek future treatment for
cataract of the fellow eye or for other ocular disease. Therefore, it is
important to have a detailed preoperative examination that differentiates
between “visual impairment due to cataract” and “visual impairment with
cataract” in order to identify ocular pathologies that may cause visual
impairment after cataract extraction. Postoperative follow-up and regular
management of cataract surgery patients is essential in order to detect not
19
only postoperative complications and comorbid ocular disease but also to
identify and correct refractive errors. In this way, physicians and patients can
maximize the benefits of cataract extraction.
The biologic and socioeconomic risk indicators associated with visual
impairment in cataract-operated adult Latinos include history of glaucoma,
barrier to eye care and a marital status of single, separated, divorced or
widowed. It is not surprising that a positive history of glaucoma, which is a
vision-impairing ocular disease, was found to be a significant risk indicator.
Our study confirms the importance of this history as a marker for visual
impairment in individuals who have undergone cataract extraction.
The explanation for barrier to eye care as a risk indicator is likely to be
multifactorial and includes economic, cultural and educational influences.
Our study does not differentiate between these factors. However, in order to
address the barrier to eye care as a risk factor for visual impairment in
cataract-operated adult Latinos, it is important to develop educational and
behavioral change programs to encourage access to eye health services by
the Latino population.
Individuals who are single, separated, divorced or widowed are less
likely to have the social support needed for adequate eye care and access to
health services. Moreover, studies have shown that separated, divorced or
widowed individuals had worsened physical and mental health and negative
marital relationships have a direct influence on cardiovascular, endocrine,
20
immune and neurosensory mechanisms and an indirect influence on
health outcomes through depression and general health habits.
12, 21
Instituting a program to facilitate access to eye health services by Latinos, as
mentioned above, would provide a support system for those without spouses
or partners.
The lower mean scores of driving difficulty subscale of NEI-VFQ-25 in
bilateral pseudophakics with any visual impairment reflects the impact of
visual impairment in cataract operated participant’s daily life activity. An effort
should be made to evaluate the impact of visual impairment after cataract
surgery on health related quality of life and activities of daily living.
Study Strengths and Limitations. LALES is the largest population-based
epidemiological study of eye disease in Latinos in the US. The main strength
of the study is that it evaluates the outcomes of cataract surgery in a
population-based sample and in the “real world” situation rather than in a
sample of convenience in a medical center follow up study where better
outcomes are more likely. The large sample sizes (overall and by age group),
high participation rate and use of objective measures of visual acuity also
contribute to the strength of the study.
Limitations of LALES include a possible bias in the rates of visual
impairment due to high participation rates of females and older Latinos.
Although the LALES cohort’s age distribution was similar to the US Latino
population, 94.7% of participants were of Mexican ancestry whereas only
21
60% of the US Latino population is of Mexican descent. Therefore, our
data are primarily applicable to Latinos of Mexican-American descent, the
largest ethnic sub-group of Latinos in the US. Another limitation includes the
lack of information gathered regarding the time between surgery and the
study and intraoperative and postoperative complications. Therefore, we
cannot comment on these factors and their influence on the visual outcomes
of cataract surgery.

22
Conclusion.
In summary, our results have shown there remains a significant degree of
visual impairment after cataract extraction in adult Latinos. We have
demonstrated that many of the underlying causes of this visual impairment
are amenable to improvement or correction by careful clinical follow-up.
Finally, creating a program that facilitates access to ophthalmic healthcare
services by Latinos would address many of the risk indicators associated
with visual impairment in cataract-operated adult Latinos.

23
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Abstract (if available)

Abstract Purpose: To determine prevalence, primary causes, and risk indicators of visual impairment (VI) in cataract-operated eyes. -- Methods: Participants with cataract extraction underwent an in-home interview and a comprehensive ophthalmologic examination. VI in the cataract-operated eye was defined by: presenting visual acuity (PVA)<20/40 or best corrected visual acuity (BCVA)<20/40. The association of cataract extraction status (aphakic, pseudophakic) and severity of VI was evaluated. Risk indicators associated with VI by BCVA in the worse seeing cataract-operated eye were evaluated. -- Results: The prevalence of VI was 32.2% defined by BCVA vs. 48.1% defined by PVA in all cataract-operated eyes. Uncorrected refractive error, age-related macular degeneration and diabetic retinopathy were the major primary causes of VI. History of glaucoma, barriers to eye care, and unmarried participants were independent risk indicators associated with VI (p<0.05). -- Conclusions: Despite cataract surgery, a significant proportion of participants had residual visual impairment demonstrating the need for regular ophthalmologic exams in cataract-operated patients.

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Asset Metadata

Creator Mazhar, Kashif (author)

Core Title Visual acuity outcomes following cataract extraction

School Keck School of Medicine

Degree Master of Science

Degree Program Applied Biostatistics

Publication Date 08/01/2007

Defense Date 06/28/2007

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag cataract,OAI-PMH Harvest,visual impairment

Language English

Advisor Azen, Stanley Paul (committee chair), McKean-Cowdin, Roberta (committee member), Varma, Rohit (committee member)

Creator Email mazhar@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-m731

Unique identifier UC1272165

Identifier etd-Mazhar-20070801 (filename),usctheses-m40 (legacy collection record id),usctheses-c127-534537 (legacy record id),usctheses-m731 (legacy record id)

Legacy Identifier etd-Mazhar-20070801.pdf

Dmrecord 534537

Document Type Thesis

Rights Mazhar, Kashif

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Repository Name Libraries, University of Southern California

Repository Location Los Angeles, California

Repository Email cisadmin@lib.usc.edu