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NR 4-6/2006
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Multifocal
diffractive intraocular lenses in cataract surgery – preliminary
report
Wieloogniskowe dyfrakcyjne
soczewki wewnątrzgałkowe w chirurgii zaćmy – doniesienie wstępne
Marek Rękas, Beata Żelichowska
From the Departament of Ophthalmology, Military Health Service
Institute in Warsaw
The Head of the Clinic: professor Andrzej Stankiewicz, Ph.D.,
M.D. |
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| Summary: |
Purpose: evaluation
of the efficacy of multifocal, diffractive intraocular
lenses in cataract surgery.
Material and Methods: 20 eyes in 10 patients,
mean age 64 ±9 years, included in the study, undergoing
phacoemulsification of the cataract with implantation of
diffractive MIOL (AcrySof ReSTOR, SA60D3, Alcon).
Follow-up was performed for a period of 6 months.
Postoperative evaluation performed five times included:
visual acuity for distance and near without and with
best correction, contrast sensitivity, patient
satisfaction in 10-grade scale, degree of independence
from glasses and frequency of lighting effects.
Results: After 6 months from surgery uncorrected
distance visual acuity ≥1.0 was achieved in 55% of
operated eyes (6/11), and the best corrected in 91%
(10/11). Uncorrected near visual acuity in 2-6 months
after surgery was achieved in all patients. Contrast
sensitivity for spatial frequencies in the range 12 and
18cdg was decreased, but in 6 cdg was normalized after 6
months of observation, and in 3 cdg was normal.
Subjective patient satisfaction in 10-grade scale was on
average in the first day after surgery 7.9 points and
after 6 months 9.3. The necessity to use glasses (30%)
and lighting effects had no bearing on subjective
patient satisfaction perception.
Conclusions: Multifocal diffractive lens implants
are able to restore good visual acuity independent of
distance and is effective and safe method in cataract
surgery. |
| Słowa kluczowe: |
wieloogniskowe soczewki
wewnątrzgałkowe, dyfrakcyjne soczewki wewnątrzgałkowe,
operacje zaćmy. |
| Key words: |
Multifocal intraocular
lens, diffractive intraocular lens, cataract surgery. |
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Introduction:
First surgeries to implant intraocular lenses were performed in
1949 by Herold Ridley (1). Since that time dynamic development
of microsurgery as well as introduction of new materials and
biomedical technologies made it possible to perform effective
and safe operations and restoring fast full visual acuity.
Nowadays standard in cataract surgery is monofocal intraocular
lens implant, which results in loss of near vision.
The idea of diffractive cataract surgery is more important in
recent years. This is a new method especially for people with
active lifestyle, which is capable to correct inducted by
cataract surgery presbyopia and reduce or eliminate dependence
on glasses.
One of the surgical methods to correct presbyopia with the use
of monofocal intraocular lenses is to create monovision
conditions. This involves creation in the dominant eye
emmetropic conditions to use for far and in the other eye
correction in the range from –1.5 to –3.0 D for near. It is
important to emphasize that about 30% of patients are unable to
tolerate monovision, due to loss of binocular vision, which is
in direct correlation with the degree of anisometropy (2,3,4).
The next step in the development of presbyopia correction was
introduction of diffractive or multifocal intraocular lenses (MIOL).
First surgeries with MIOLs, originally as models of 2-3 zones,
were performed already in 1986 (5). Amongst currently used MIOLs
there are two basic types: refractive lenses and diffractive
lenses. Diffractive lenses are characterized by quick
achievement of near vision, and also less frequent side effects
in the form of lighting phenomena in comparison to refractive
lenses (4,6,7).
The aim of this study is evaluation of effectiveness of
multifocal, diffractive intraocular lens implants in cataract
surgery. Analysis of visual acuity, contrast sensitivity and
subjective satisfaction of patients, lighting side effects and
dependence on glasses was performed.
Material and Methods
Studied material includes post-surgical evaluation after 20
phacoemulsification of senile cataracts and multifocal,
diffractive intraocular lenses implants (AcrySof ReSTOR, SA60D3,
Alcon). The implant surgeries of MIOLs were performed in both
eyes in all patients about four weeks apart between procedures.
It was a group of 4 men and 6 women, 49 to 74 years old (mean 64
±9).
Diagnosis of bilateral cataract was the requirement for
operation and inclusion in the study. Qualification of patients
for MIOL implants besides typical ophthalmologic exam included
extensive interview to assess motivation towards MIOL implant,
desire to get independent of glasses and level of daily activity.
All patients received information about surgical therapy of
cataract, MIOL specification, possible complications, and
specifically about necessity of neuroadaptation to new vision
system and consciously consented to surgery as well as
post-surgical evaluation. Exclusions from MIOL implants were
narrowed to ophthalmic pathology that could influence
achievement of good visual acuity and included irregular
astigmatism, corneal cone, corneal decompensation, severe dry
eye syndrome, eccentric, non reactive pupil, diabetic
retinopathy, macular degeneration, high risk of retinal
detachment, poorly controlled glaucoma, previous laser or other
eye surgery, monofocal intraocular lens in one eye and required
power of MIOL beyond availability. Calculation of MIOL power was
done by ultrasonograpphic measurement of the eyeball axis by the
contact method with the use of SRK/T formula (constant A=118.2).
The goal of the refraction was scheduled for emmetropic (±0.25
D). The same surgeon performed all surgical procedures. In one
patient, because of bilateral with the rule astigmatism at the
level 1.8-2.0 D limbal relaxing incision (LRI) was done at the
same time.
In the study protocol, post-surgical evaluation was scheduled
five times in the following intervals from the surgery: 1 day, 1
week, 1 month, 2 months and 6 months. Protocol of the study
included examination of distance and near visual acuity with
Snellen tables without correction (UCVA) and with the best
correction (BCVA), tonometry, examination of anterior chamber
with the slit lamp, ophthalmoscopy, corneal topography, and
subjective evaluation of the quality of vision and satisfaction
level graded from 1 (minimal satisfaction) to 10 (maximal),
dependence on glasses and side effects (like effect “halo”,
lighting phenomena and difficulty in adaptation to the new
visual system). Additionally in every patient with visual acuity
≥1.0 (Snellen), the curve of contrast sensitivity was determined
with table CSV-1000.
Results
In subject group pre-operation mean uncorrected distance
visual acuity was 0.3 ±0.18 and 0.5 ±0.26 with the best
correction. Range of pre-operation refraction in spherical
equivalent was from –3.5 to +4.0 D.
Uncorrected distance visual acuity (UCVA) after 1 day
post-surgery was in the range 0.3-1.0 (mean 0.6 ±0.2), after 1
week 0.6-1.0 (mean 0.8 ±0.2), and subsequently after 1-6 months
0.7-1.0 (mean 0.9 ±0.1). Results of the uncorrected distance
visual acuity are shown in figure 1.
Full uncorrected visual acuity (UCVA) ≥1.0 1 day after operation
were achieved by 10% (2/20) of the operated eyes, after 1 week
40% (8/20), after 1 month 50% (8/16), after 2 months 50% (7/14),
and after 6 months 55% (6/11). The best corrected distance
visual acuity (BCVA) ≥1.0 after 1 week was noticed in 65%
(13/20) of the operated eyes, and after 6 months in 91 % (10/11)
respectively. Specific information is shown in table 1.
Uncorrected near visual acuity at the level 0.5 according to
Snellen chart 1 day after operation was found in 45% (9/20) of
the operated eyes, after 1 week in 75% (15/20), after 1 month in
94% (15/16) of the operated eyes, and after 2-6 months in all
the patients (figure 2)
One month after operation in 31% (5/16) of the operated eyes
mean spherical equivalent was +0.45 ±0.11 D (range to +0.5 D),
and after 6 months +0.25 ±0.47 D (range from -0.25 to +0.75 D).
In the intraoperative time and immediately after no essential
side effects connected to MIOL implant were observed.
Intraocular pressure during the study was never recorded higher
than 21 mmHg in all patients. Examination of the anterior
chamber with slit lamp did not show misplacement of MIOL.
Warping of the posterior capsule was noted after 1 month from
surgery in 44% (7/16) of the operated eyes.
Results of the contrast sensitivity are shown in figure 3.
General subjective level of the patient satisfaction using 10
grade scale was after 1 day 7.9 ± 2.3 pts, after 1 week 8.9
±1.3, after 1 month 9.0 ±1.4, after 2 months 9.4 ±1.2, and after
6 months 9.3 ±0.8 pts. Subjective near visual acuity was
slightly lower but statistically insignificant in comparison
with distance visual acuity in particular steps of observation
(p>0.05) (figure 4).
History data showed that 3 out of 10 operated patients were
using intermittently glasses for reading, generally with being
tired in the evening hours or during precision required vision
for near sight.
4 out of 10 patients reported lighting phenomena around
artificial light sources, but it was substantially reduced in
1-4 weeks after implantation of MIOL in the second eye. Patients
reported lighting intensity as moderate or low without essential
interference on quality of vision. In 6 out of 10 studied after
MIOL implantation in both eyes it appeared “halo” phenomenon
during reading in the evening hours, described by patients as
“shadow” of the letters or diplopia.
Discussion
In our work we concluded, that distance uncorrected visual
acuity ≥0.8 [≥20/25 Snellen, ≥0.1 log MAR] after 2 months from
MIOL implant was achieved in 79% (11/14) of the operated eyes,
and after 6 months 100% of the operated eyes. These results
point out that multifocal, diffractive intraocular lenses
implants enables good distance visual acuity. In the available
bibliography there are a very few publications evaluating
effectiveness and post-operation period after implants of
diffractive lenses of the type AcrySof ReSTOR. In the recently
published work by Roch KM et al. evaluation of visual acuity,
aberration and contrast sensitivity after AcrySof ReSTOR lens
implant was performed as well as 3 types of monofocal lenses. In
evaluation of visual acuity after 2 months of observation in 90%
of the eyes (45/50) with diffractive lenses ≥20/25 [≥0.8 Snellen]
best-corrected visual acuity (BCVA) was achieved (8).
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Our own
study, although using small group of patients shows that all the
patients after 2 months achieved distance BCVA ≥0.8. For proper
interpretation of the results it is important to consider time
frame of the visual acuity correction in the post-operation
period. Therefore the best reference should be comparison of the
visual acuity in analogical time compartments. Unfortunately in
many papers the final evaluation of the visual acuity is
presented, after observation period that is frequently variable.
It is directly connected with neuroadaptation process to the new
visual system, which lasts about 3 months (9). It seems, that
earlier analyses mirror only the time necessary for full
adaptation, but reliable evaluation should involve longer
observation period. Walkow T. et al. present such data in paper
with the use of different than AcrySof ReSTOR diffractive lens
(10). In this work it was shown, that after 12 months distance
uncorrected visual acuity (UCVA) ≥0.8 was achieved in 73.4%
(47/64) of the studied eyes, and best corrected visual acuity (BCVA)
>0.8 in all patients. Interesting communication is the work by
Slagsvold with multiyear (7.9 ±1.3 years) observation period
after diffractive lens implant 3M (11). Despite the fact, that
during such a long observation period, quality of visual acuity
in older group of patients (78.1 ±6.8 years) may be influenced
by many systemic factors, the author found distance uncorrected
visual acuity (UCVA) ≥0.8 in 69.9% of the eyes (53/76).
For a full assessment of the neuroadaptation process it is
important to know time to achieve correction of the visual
acuity with differences for distance and near. In own material
we noticed difference in the dynamic of correction of the visual
acuity for distance in comparison to near. Uncorrected distance
visual acuity ≥1.0 1 day after surgery was achieved by only 10%
of the operated eyes, but near visual acuity at the level 0.5
according to Snellen chart was achieved by 45% of the operated
eyes. Results after 1 week are 40% for distance and 75% for near,
and after 1 month 94-100% of the operated eyes achieve 0.5 (Snellen
chart) uncorrected near visual acuity, and 50-55% uncorrected
distance visual acuity, and corrected 81-91%. Our results may
suggest that neuroadaptation process for near in that kind of
lenses is more rapid. In the available literature there is no
data on dynamic return of visual acuity after MIOL implant type
AcrySof ReSTOR. Communication evaluating dynamic improvement in
the visual acuity for near is work by Alio JL. et al. comparing
diffractive lens TwinSet with accommodative and refractive
lenses (7). In this communication after 12 months observation
period it was determined that return to near visual acuity was
faster with diffractive lens than any other. Achievement of
better visual acuity for near as compared to distance could be
interpreted in connection to construction of the optical part of
diffractive MIOL, comprised of central 3.6 mm zone of
diffractive rings with added power for near.
Another problem that we assessed in our work was contrast
sensitivity. According to some communications, implants of every
type MIOL result in decrease in contrast sensitivity (3,13,14).
In our material we determined, that within 12 and 18 cdg
contrast sensitivity values are diminished in the entire 6
months observation period. Lowering of the contrast sensitivity
in frequency range from 6 to 18 cdg was noted by Slagsvold, who
was evaluating diffractive lenses 3M, however results were
assessed after about 7.9 years from the surgery (11). Analyzing
results within frequency 6 cdg we noted substantial improvement
of contrast sensitivity between second and sixth months of
observation. In turn contrast sensitivity values for frequency 3
cdg remained in the age referenced norm. Stated improvement of
the contrast sensitivity could be the effect of neuroadaptation
and points at, that optimal time for reliable assessment of
contrast sensitivity is 6 months after surgery. Similar
conclusions were suggested in the work by Montes-Mico et al.
evaluating contrast sensitivity for refractive model of MIOLs.
He also noticed improvement in the contrast sensitivity in the
period from 3 to 6 months after MIOL implant (12).
Subjective satisfaction level of patients was very high already
in the first week after MIOL implant. So high satisfaction level
in the studied group was not connected with the necessity of use
of the glasses for near by 3/10 patients. The remainder of
patients (70%) in the 6 months observation period never used
glasses. This data is close to the ones obtained by Walkow et
al., according to whom 80.6% of operated patients never used
glasses (10). Slightly worse results were obtained after implant
of diffractive lenses 3M, where in the group of 72 patients only
39 (54.2%) never used glasses (11). Subjectively worse
evaluation for near in our group was influenced by lighting side
effect “halo” in 60% of operated patients during reading.
Side effects like flashes observed in this work in 4/10 patients
estimated as mild or moderate did not have any influence on
subjective assessment of vision quality. Reduction of lighting
effects in comparison to refractive MIOLs may stem from gradual
connection of optical elements in diffractive central part of
the lens and from refractive peripheral zone.
We emphasize, that our observations are preliminary and for
reliable comparison the number of patients should be higher and
observation period should be longer.
Conclusions
The use of diffractive MIOL allows achievement of good
visual acuity independent from distance with slight advantage
for near as a result of faster return of visual acuity.
Contrast sensitivity after implant of diffractive MIOL is
decreased in the range of higher frequencies, but it normalizes
for lower frequencies in 6 months observation period.
After implant of diffractive MIOL patient satisfaction was high,
independent from few lighting phenomena and sporadic correction
with glasses.
References
1. Jacobi PC, Dietlein TS, Luke C, Jacobi FK: Multifocal
Intraocular Lens Implantation in Presbyopic Patients with
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2. Wang JC, Tan AWT, Monatosh R, Chew PTK: Experience with ARRAY
multifocal lenses in a Singapore population. Singapore Med J.
2005; 46(11):616-620.
3. Montés-Micó R, Espana E, Bueno I, Charman WN, Menezo JL:
Visual performance with multifocal intraocular lenses: mesopic
contrast sensitivity and near conditions. Ophthalmology. 2004
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Surg. 1998; 24: 663-5.
7. Alió JL, Tavolato M, de la Hoz F: Near vision restoration
with refractive lens exchange and pseudoaccommodating and
multifocal refractive and diffractive intraocular lenses.
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30(12): 2494-2503.
8. Rocha KM, Chalita MR, Souza CE, Soriano ES, Freitas LL,
Muccioli C, Belfort R Jr; Postoperative wavefront analysis and
contrast sensivity of a multifocal apodized diffractive IOL (ReSTOR)
and three monofocal IOLs. J. Refract Surg. 2005, 21: S808-12.
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10. Walkow T, Klemen UM: Patent satisfaction after implantation
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11. Slagsvold JE: 3M diffractive multifocal intraocular lens:
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12. Montés-Micó R, Alió JL: Distance and near contrast
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13. Lee ES, Lee SY, Jeong SY, Moon YS, Chin HS, Cho SJ, Oh JH:
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Adres do korespondencji (Reprint
requests to):
dr n. med. Marek Rękas
ul. Trapezowa 51
08-521 Dęblin |
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