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Citation: Labiris G, Toli A, Perente A, Ntonti P,
Kozobolis VP. A systematic review of pseudophakic monovision for presbyopia
correction. Int J Ophthalmol
2017;10(6):992-1000
A systematic review of pseudophakic monovision for
presbyopia correction
Georgios Labiris1,2, Aspa Toli2,
Aslin Perente2, Panagiota Ntonti2, Vassilios P. Kozobolis1,2
1Department of
Ophthalmology, University Hospital of Alexandroupolis, Dragana, Alexandroupolis
68100, Greece
2Eye Institute of Thrace,
Alexandroupolis 68100, Greece
Correspondence to: Georgios Labiris. Department of Ophthalmology, University Hospital of
Alexandroupolis, Dragana, Alexandroupolis 68100, Greece. labiris@usa.net
Received: 2016-10-17
Accepted: 2017-02-23
Abstract
A
systematic review of the recent literature regarding pseudophakic monovision as
a reliable methods for presbyopia correction was performed based on the PubMed,
MEDLINE, Nature and the American Academy of Ophthalmology databases in July
2015 and data from 18 descriptive and 12 comparative studies were included in
this narrative review. Pseudophakic monosvision seems to be an effective method
for presbyopia with high rates of spectacles independence and minimal
dysphotopsia side-effects, that should be considered by the modern cataract
surgeons.
KEYWORDS: pseudophakic
monovision; presbyopia correction; cataract extraction; mini-monovision;
monofocal intraocular lens; lens implantation
DOI:10.18240/ijo.2017.06.24
Citation: Labiris G, Toli A, Perente A, Ntonti P,
Kozobolis VP. A systematic review of pseudophakic monovision for presbyopia
correction. Int J Ophthalmol
2017;10(6):992-1000
HISTORY OF PRESBYOPIA CORRECTION
Presbyopia is an age-related refractive condition, where the
accommodation of eyes progressively weakens, subsequently leading to impairment
of the ability to focus on near objects. The correction of presbyopia includes
reading spectacles, contact lenses and a series of surgical techniques. In
recent years, the patients have expressed a need for a spectacle-free life,
which in turn has given great emphasis on the need for advancement in the field
of the surgical correction of presbyopia.
Presbyopia symptoms are present in patients after cataract lens
extraction. The treatment of such patients is a main challenge of modern
ophthalmology. Pseudophakic presbyopia corrections primarily include: 1)
implantation of multifocal intraocular lens (IOLs); 2) implantation of
accommodative IOLs and; 3) pseudophakic monovision induced by monofocal IOLs[1].
Regarding monovision, one eye is corrected for distance vision and the
fellow for near vision. In the majority of the cases, the dominant eye is
corrected for distance vision and the recessive one for near vision
(conventional monovision). When the recessive eye is chosen for distance
vision, the technique is referred as crossed monovision. In the hybrid
monovision technique, a diffractive multifocal IOL is implanted in the
nondominant eye, whereas in the dominant eye a monofocal IOL is implanted[1].
Contact lenses monovision is known since the early 60s[2].
However, the first publication of pseudophakic monovision was performed in
1984, by Boerner and Thrasher[3]. In 1999,
conventional monovision was firstly used for the correction of the presbyopia
after cataract surgery[4-6].
Primary objective of this paper is to review published literature
regarding the efficacy of pseudophakic monovision in the correction of presbyopia
after cataract extraction, based on both subjective parameters of patients,
such as satisfaction, spectacle independence and dysphotopsia symptoms and also
clinical parameters, including visual acuity (VA) at all distances, contrast
sensitivity stereopsis and possible complications postoperatively.
LITERATURE RESEARCH AND EVALUATION
A systematic search for relative studies was carried out based on
PubMed, MEDLINE, Springer, Nature, Scopus, Journal of Cataract and
Refractive Surgery and American Academy of Ophthalmology databases
using the search terms below: pseudophakic monovision; monovision and
presbyopia; monovision and cataract; mini-monovision; monovision review;
monovision and monofocal IOLs; monovision and multifocal; monovision and lens implantation.
The search took place in July of 2015. The initial search was performed without
search filters and language restrictions. Afterwards, the results were checked
and only articles related to the subject were selected. Subsequently, the
eligible articles and abstracts were scanned diligently and the following data
were extracted: article information, surgical data, patient selection, clinical
parameters, spectacle independence, patients’ satisfaction and possible
complications. Both comparative and descriptive studies on adult patients were
included in this review. Articles covering only techniques for presbyopia
correction after cataract surgery, other than pseudophakic monovision or
referring to children patients, or not available in English were excluded. When
the eligible articles were not available in full text, abstracts were used as a
source of information.
Studies’ Design The present review included 18 descriptive[2-3,6-21], 12
comparative[22-33] studies.
Among them 10 were prospective studies[2,9,22,26-29,31-33] and 5 retrospective[3,10,15-16,19],
while there was not any relative statement in the rest of the studies. Nine[22-25,27,29-31,33] of the studies compared the
pseudophakic-monovision technique with the multifocal IOLs implantation technique,
using refractive[24] or diffractive[22,27,30-31,33] IOLs, as it was described in most of the studies.
Beiko[28] compared mini-monovision with
accommodating IOLs implantation, while two studies compared conventional
monovision with modified[26] or crossed[9,32] monovision (Table 1).
Table 1 Studies design
|
Studies |
Comparative studies |
Descriptive studies |
Prospective studies |
Retrospective studies |
|
References |
22, 33 |
2, 3, 6-21 |
2, 9, 22, 26-29, 31-33 |
3, 10, 15, 16, 19 |
|
No. of studies |
12 |
18 |
10 |
5 |
Patient Selection Patient selection was presented to be very crucial for the success of
pseudophakic monovision[14] and most surgeons
dealt thoroughly with patients’ inclusion and exclusion criteria.
The most frequent inclusion criterion was the desire for spectacle
independence[9,12,22,28]. Zhang et al[22]
excluded patients who did not have the demand to be spectacle free
postoperatively. Osher et al[20] included
only patients with cataract and longstanding acquired strabismus in order to
evaluate the efficacy of pseudophakic monovision in diplopia. Among the
exclusion criteria were the following: severe ocular disease, corneal
astigmatism, strong ocular dominance, large exophoria, and inability to
understand the concept of monovision design. Severe ocular disease was a common
reason for exclusion from the studies, as it was believed to have unfavorable
effect on visual rehabilitation[14]. Patients
with glaucoma, retinal pathology, optic neuropathy, amblyopia and other ocular pathology
that may affect visual performance were excluded from several studies[2,14,16,19,21,26,28-30].
Some of the studies had a restriction about corneal astigmatism. Most of them[21,24,28-30]
excluded patients with corneal astigmatism of 1.00 D or greater. Finkelman et
al[2] and Ito et al[10]
did not select patients with astigmatism of 1.50 D or greater, while Greenbaum[12] excluded patients with astigmatism of 2.00 D or
higher. Handa et al[6] studied the
importance of ocular dominance in patient selection. Strong ocular dominance
was reported to cause anisometropia and decrease of visual performance.
Therefore, weak ocular dominance was considered to be a significant parameter
for monovision success[14]. Patients with a
history of strabismus or large exophoria were excluded from 6 studies[10,14,16,19,21,24]. Zhang et al[22] set a pupillary diameter restriction of 5.00 mm or
larger, while other researchers excluded patients with pupil size smaller than
4.00 mm and 4.50 mm, respectively[26]. Finkelman et
al[2] excluded patients who could not
understand the concept of monovision design. In addition, another study
excluded patients who had poor knowledge of English[30].
Regarding patients’ age, only studies on adults were included in this
review. The participants’ age varied from 24[21]
to 94[20], while in 8[3,6-8,13,23,27,32] studies there were no age data
available. Ito et al[10-11,14] divided patients into three age-groups and analysed
comparatively their parameters. Conventional monovision was compared to
modified monovision by Hayashi et al[26]
and the outcomes were associated with age. Iida et al[21]
performed hybrid monovision technique and they found a significant association
between age and satisfaction rate.
Monovision Methods Some researchers dealt with the different types of monovision technique.
Kim et al[32] compared conventional with
crossed monovision, while Hayashi et al[26]
compared modified with conventional monovision. Iida et al[21] used a new technique called hybrid monovision, where
a monofocal IOL was implanted in the dominant eye and a diffractive multifocal
IOL in the nondominant eye.
Ito et al[10-11,14,16,19,24]
performed conventional method of pseudophakic monovision, correcting the dominant
eye as emmetropic (0.00 to +0.25 D) and the nondominant eye as myopic
(-2.00±0.50 D). Zhang et al[22,33]
adopted the traditional (conventional) monovision technique, with an
approximate difference of 2.00 D between two eyes, while comparing it to multifocal
IOL implantation. Stanojcic et al[31]
corrected the dominant eye for distance vision 0 to -0.50 D and the nondominant
for near vision -1.00 to -1.50 D in monovision group. Lubiński et al[18] used conventional pseudophakic monovision and
corrected the dominant eye to emmetropia and the non-dominant eye to -2.00 D.
Osher et al[20] evaluated the efficacy of
pseudophakic monovision in longstanding diplopia. They corrected the dominant
eye for distance vision and the non-dominant eye for near vision, with a mean
difference between two eyes’ correction of at least 3.00 D. Greebaum[12] selected the dominant eye for emmetropia correction
and the non dominant eye for myopia correction of -2.75 D. Wilkins et al[30] performed a comparative study, where the “distance’’
eye was corrected to emmetropia and the other eye between -1.00 and -1.50 D.
Finkelman et al[2] used modified monovision
in patients with second-eye cataract surgery, after successful surgery in the
first eye with emmetropia. They had a moderate myopic target refraction of
-1.00 to -1.50 D. Hayashi et al[26]
compared the modified monovision with conventional monovision with 0.75 and 1.75 D
anisometropia respectively. In another study[7]
they evaluated the optimal target anisometropia for successful pseudophakic
monovision to be circa 1.50 D. In Iida et al’s study[21]
for hybrid monovision, both eyes were corrected to emmetropia 0.00 to +0.25 D.
Marques et al[9] did not take into account
the ocular dominance while using pseudophakic monovision technique, but
corrected the first eye between -0.50 and +0.50 D and the second eye to -2.00
D. In Zettl et al[15] clinical trial for
pseudophakic monovision, there was a slight difference in correction between
the two eyes 0.50 to 1.75 D. Beiko[28] set a target
refraction between -0.25 and -0.75 D in the mini-monovision group, without
accounting the dominance of the eye. Chen et al[25]
adopted a mini-monovision formula, achieving correction of dominant eye for
distance vision and and that of nondominant for near vision of -0.50 to -1.25 D.
Labiris et al[29] corrected the dominant eye to -0.50 D and the
nondominant to -1.25 D, in the mini-monovision group of their trial.
The number of surgeons was mentioned in 9 studies[2,9,22,25-26,28-30,33]. In most
of these cases[9,22,25-26,28-29,33],
surgeries were performed by the same surgeon, while there was a second surgeon
in Finkelman et al’s study[2]. Wilkins et
al[30] reported the participation of 9
cataract surgeons in their study.
The kind of IOLs used in monovision design in the eligible studies was
reported in 18 studies. The IOLs used in each trial are presented in Table 2,
among them monofocal Acrysof SN60WF IOLs[22,25,27,33] and
monofocal IOL (AQ110NV, Canon-Staar)[10,16,19,24] were preferred in eight
studies.
Table 2 IOLs used in monovision technique
|
IOLs |
References |
No. of studies |
|
Monofocal Acrysof SN60WF IOLs |
22, 25, 27, 33 |
4 |
|
Monofocal
IOL (AQ110NV, Canon-Staar) |
10, 16, 19, 24 |
4 |
|
Acrysof monofocal IOL |
23 |
1 |
|
Hydrophobic
acrylic IOL (ZCBOO, Abbot Medical Optics) |
26 |
1 |
|
Tecnis
1-piece monofocal (nonaccomodating) control IOL , Abbott Medical Optics, Inc. |
28 |
1 |
|
Akreos
AO monofocal lenses (Bausch & Lomb, Rochester, NY) |
4, 30 |
2 |
|
Alcon SA60AT monofocal IOL |
18 |
1 |
|
Monofocal IOL (AQ31Ai) |
21, 25 |
2 |
|
Monofocal IOL (Sensar -AMO) |
9 |
1 |
|
Foldable
hydrophilic acrylic IOL (SN60WF, Alcon Laboratories, Inc.) |
29 |
1 |
Comparative Studies This review included twelve comparative studies, among them 8 studies
were prospective[22,26-29,31-33]. Methods compared to
pseudophakic monovision technique were presented in Table 3.
Table 3 Studies design: comparative studies
|
Techniques |
References |
No. of studies |
|
Multifocal
IOL implantation vs pseudophakic monovision |
22-25, 27, 29-31, 33 |
9 |
|
Diffractive multifocal
IOLs |
22, 27, 30, 31, 33 |
5 |
|
Refractive multifocal
IOLs |
24 |
1 |
|
Not stated |
23, 25, 29 |
3 |
|
Accommodating
IOLs implantation vs mini-monovision |
28 |
1 |
|
Modified
monovision vs conventional pseudophakic monovision |
26 |
1 |
|
Crossed
monovision vs conventional pseudophakic monovision |
32 |
1 |
Most of the studies compared the pseudophakic monovision with the
implantation of multifocal IOLs[22-25,27,29-31,33].
It was shown that distance VA was significantly better postoperatively after
both techniques[29,33].
Furthermore, between two groups there was not significant difference concerning
distance VA[22-25,27,29-30]. Chen et al[23,25] compared the Acrysof monofocal
IOL in mini-monovision with the ReSTOR multifocal IOL implantation and
demonstrated that patients of both groups could achieve 20/30 distance VA and
J3 near vision without spectacles after surgery.
Pseudophakic monovision and multifocal IOLs could achieve significant
improvement of unaided near VA postoperatively (P<0.001)[33]. According to three studies the above methods did not
show any statistically significant difference in postoperative near VA
evaluation comparatively[24,27,29]. On the other hand, Zhang et al[22] pointed out a significant difference between
monovision and multifocal groups in binocular uncorrected near visual acuity
(UNVA). In the multifocal group 90% of patients had 20/20 contrary to the
respective percentage of 59% in monovision patients (P=0.018). However,
there was no statistically significant difference between 2 groups in the
percentage of eyes with a UNVA of 20/25 or better (P=0.331). Wilkins et
al[30] found that binocular UNVA was
significantly better in the multifocal group [(-0.03) logMAR] than in
monovision group [(0.01) logMAR] (P=0.037).
Regarding the intermediate VA, Zhang et al[22]
found that 73% of patients in monovision group had 20/30 or better uncorrected
intermediate visual acuity (UIVA) in comparison with multifocal group (9%; P<001).
In Wilkins et al[30] trial, the monovision
arm showed significantly better UIVA than the multifocal arm (P=0.000).
However, Mu et al[27] did not find
significant difference in intermediate vision examination between multifocal
and monovision group.
Zhang et al[22] observed no
statistically significant difference between monovision and multifocal groups
in stereovision analysis results. On the other hand, Mu et al[27] pointed out significant differences between
monovision and multifocal groups in stereovision (Median: 150″, 525″; Z=-2.092,
P=0.036). Another study, showed significantly better stereovision with
multifocal IOLs, with mean binocular stereoacuity of 1.77 contrary to 1.99 of
monovision group (P=0.000)[30]. Wilkins et
al[30] compared the contrast sensitivity in
monovision and multifocal patients, with statistically better results in
monovision group (P=0.009).
According to Chen et al’s[25] study,
95% of ReSTOR multifocal patients and 35% of mini-monovision group achieved
spectacle independence (significant difference, P=0.013). It is worth
mentioning that they considered the patient was independent from spectacles, if
he/she declared independence from them. In another study, Chen et al[23] proposed Acrysof monofocal IOL using the mini
monovision formula as a good alternative to array multifocal IOLs implantation
for spectacle independence after cataract surgery, because monofocal group had
similar to slightly better outcomes than multifocal group in spectacle
independence. Mu et al[27] reported that
less than 10% of patients in groups of monovision and multifocal groups, were
spectacle dependent postoperatively. Labiris et al[29]
assessed the spectacle dependence using the VF-14 questionnaire. They reported
that patients of both groups had excellent spectacle independence for distance
vision, while the dependence for near vision was significantly less in the
multifocal arm of the study (P<0.01). In the total outcome, the
spectacle independence rate for the monofocal group was 31.40% and for the
multifocal group 65.70%. Wilkins et al[30]
used the VF-14 visual function questionnaire to evaluate the spectacle
independence postoperatively. According to their outcomes significantly more
patients in the multifocal group than in the monovision declared that they
never used glasses after surgery, with relative percentages of 71.30% and
25.80%, respectively (P<0.001). Another study[33]
demonstrated that patients of multifocal and monovision group had statistically
significant betterment in everyday life activities after surgery. Zhang et
al[22] reported no significant difference
between monovision and multifocal groups in the percentage of patients who
never needed glasses for computer work. However, significantly more patients in
monovision group reported no difficulty or little difficulty using computer
without glasses (P=0.048). There was no significant difference between 2
groups in the percentage of patients who never required glasses for newspaper
reading and for driving. Patient-reported driving problems and difficulty
during day and night driving were also without significant differences. The 14%
of monovision and 24% of multifocal patients reported they had moderate
difficulty in driving at night.
A trial of Ito et al[24] evaluated
the reading ability of patients who underwent bilateral cataract surgery with
pseudophakic monovision and refractive multifocal IOLs implantation. They
estimated the mean maximum reading speed, being not significantly different in
two groups. However, a significant difference in the mean reading speed was
observed in favor of the monovision team, at the character sizes from 0.30 to
0.10 logMAR (P<0.05). The researchers also evaluated the critical
character size and showed that it was significantly better in the monovision
group (P<0.05). Moreover, monovision group noted significantly better
reading acuity than multifocal group (P<0.01).
Regarding patients’ satisfaction, Wilkins et al[30] reported that there was no statistically significant
difference between the monovision group and the multifocal group (P=0.46).
Zhang et al[22] used VF-14 questionnaire
for the evaluation of patient satisfaction in their comparative study of
multifocal IOL implantation and pseudophakic monovision. They concluded that
there were no significant differences in satisfaction with specific elements,
including cost, willingness to recommend the procedure, and total satisfaction
with the surgery/IOL styles, between the 2 groups. However, monovision scores
were more auspicious in the above three elements.
Among the reasons for patients dissatisfaction was the presence of
dysphotopsia symptoms. The researchers[22] found
that significantly more patients in multifocal group than in monovision
presented halo and glare symptoms (P<0.01 and P=0.024). The
82% and 36% of monovision group reported having halo and glare symptoms none of
the time, respectively. On the other hand, 10% and 14% of multifocal group
reported they never had such symptoms. No significant difference was observed
in difficulty in day or night driving, or in driving with difficult conditions
between the two groups. Labiris et al[29]
mentioned that multifocal patients complained about significantly more unwanted
shadows (P=0.02) and insignificantly more glare (P=0.08) than
patients in mini-monovision group. Wilkins et al[30]
found that multifocal patients more often mentioned annoying or debilitating
glare or dazzle than monovision group (P<0.0001). Symptoms such as
unwanted images and unusual shadows did not differ significantly in both
groups.
Mini-monovision technique was compared with implantation of
accommodating IOL in Beiko et al’s[28]
study. They examined binocular distance, near/intermediate VA and
photopic/mesopic contrast sensitivity, without finding any significant
differences between two groups. Another study[32]
compared conventional monovision with crossed monovision. They analysed
binocular uncorrected distance and near VA, best corrected VA, stereopsis,
spectacle independence after surgery and patients’ satisfaction rate, without
any significant differences between two groups.
Stanojcic et al[31] performed an
exploratory study where they analysed the visual fields in monovision and
multifocal IOL patients. Although there was not statistically significant difference in their results (P=0.662),
3/10 monovision plots had suboptimal hemi-fields (distance-dominant eye) compared
with 0/15 multifocal plots.
Hayashi et al[26] compared
conventional monovision (1.75 D anisometropia) with modified monovision (0.75 D
anisometropia). They found that binocular intermediate VA at 1.00 m was
significantly better in the modified monovision group than in the conventional
monovision group (P=0.0001), while near VA and intermediate VA at 0.50 m
was significantly worse in the modified monovision group (P<0.0001).
On the other hand, there was no statistically significant difference between two
groups in binocular distance VA at 5.00 m. Regarding the mean binocular
photopic and mesopic contrast VA and glare VA the results tended to be better
in the modified monovision group, but the difference was not statistically
significant. In addition, it was reported that the mean stereoacuity was
significantly better with modified monovision (P=0.002). The researchers
correlated the outcomes with the age of patients. For the modified monovision
group, it was indicated that younger age was significantly correlated with
better binocular distance to intermediate VA (5.00, 3.00, 2.00, 1.00 m). There
was no significant association between age and binocular intermediate VA at
0.70 and 0.50 and near VA at 0.30 m. Significant but weak correlation was also
observed in conventional monovision group, between age and binocular
intermediate VA at 0.50 m. Both groups presented statistically important
correlation between younger age and better contrast VA with and without glare.
Descriptive Studies Ito et al[10-11,14,16,19] dealt
with pseudop-hakic monovision in five of the eligible descriptive studies. In
2009, they emphasized the important role of patient selection in the outcome of
pseudophakic monovision technique. They suggested that excellent UDVA in the
dominant eye; near exophoria no more than 10.00 prism diopters (Δ); and patients’ age over 60y were the principles for successful
monovision[14]. In other studies, Ito et al[10-11] divided patients in three age
groups: younger than 60y; 60 to 70y; older than 70y. They assessed the visual
performance (VA at all distances, contrast sensitivity, near stereopsis) and
patients’ satisfaction after pseudophakic monovision. Patients over 70 years
old presented higher percentage of satisfaction than the other age groups, while
the lowest percentage of satisfaction was in the youngest group. Moreover, the
highest rates of both dissatisfaction and spectacle use were measured in
patients younger than 60y. The main reasons for dissatisfaction were lack of
visual clarity, asthenopia, postoperative spectacle dependence and discomfort[10]. In a five-year clinical trial of 2012[19], the researchers supported that pseudophakic
monovision could provide an over time stability for the presbyopia correction.
During the follow-up period, patients showed good near stereopsis and VA
outcomes, while spectacle independence and patients’ satisfaction got better
gradually.
In 2014, Ito et al[16] correlated
visual function with ocular deviation in patients who underwent pseudophakic
monovision surgery. The patients were divided in two groups according to ocular
deviation: mild angle-exophoria (≤10.00 Δ) and
moderate angle-exophoria (>10.00 Δ). They
found that there was statistically significant difference in median value of
stereopsis, with better scores for patients with exophoria <10.00 Δ. Furthermore, they proved a statistically important positive
correlation between preoperative near exophoria angle and postoperative near
stereopsis, suggesting the preoperative exophoria as inclusion criterion for
successful pseudophakic monovision.
The optimal anisometropia for effective pseudophakic monovision was
valued in two studies[7,17].
Hayashi et al[7] indicated that
anisometropia of approximately 1.50 D was considered to be the optimal one for
successful monovision, providing profitable outcomes in visual performance.
Naeser et al[17] presumed that binocular
problems were minimized with anisometropia of 1.00 D, which was thought to be
ideal one.
Marques et al[9] reported the
effectiveness of pseudophakic monovision in visual performance and patient satisfaction.
The outcomes showed that 97.40% of patients had ≥20/30 UDVA and ≥J2 of UNVA.
Intermediate uncorrected VA of J3 was measured in 90% of patients. Most
patients (81.50%) presented an expected decrease of stereoacuity, but Titmus
test showed an average of 197″. The 97.30% of patients declared satisfied and
very satisfied with the monovision technique, intimating a high percentage of
spectacle independence. Only one patient reported discomfort while playing
soccer or driving at night and required optical correction.
In another study, Lubiński et al[18]
also assessed visual function and patient satisfaction after conventional
pseudophakic monovision. The outcomes showed very good visual function, without
any postoperative complications. There were high rates of spectacle
independence at all distances and patient satisfaction of 9.40/10.
Handa et al[6] amplified the
relationship between ocular dominance and patient satisfaction after monovision
with IOL implantation. Patients who underwent successful monovision presented
the reversal threshold only at low decreasing contrast. On the other hand, in
patients who were operated with monovision unsuccessfully the reversal
thresholds were at high decreasing contrast (20%) or not at all. However, all
patients revealed high rates of satisfaction. Ocular dominance significantly
affected patient satisfaction and monovision success.
Zettl et al[15] studied the contribution
of pseudophakic mini-monovision for spectacle free life in patients after
cataract surgery. All patients achieved good distance and intermediate visual
acuities (logMAR 0 and 0.10 respectively), while a remarkable reduction of near
vision was described (63.33% had logMAR 0.30). The reading ability outcomes
showed median average reading speed for binocular uncorrected reading under
photopic conditions of 145 words/min and under mesopic conditions 117
words/min, the critical font size was logRAD 0.60 (Jaeger 5-6), the anisoconia
at 2 % and stereopsis at 80 arc seconds. The overall spectacle dependence was
assessed to 13 %, postoperatively. The findings of high satisfaction scores
were considered to be comparable to those of full-monovision and multifocal IOL
implantation.
Osher et al[20] performed extreme
anisometropic pseudophakic monovision in patients with longstanding diplopia,
with excellent visual outcomes and high satisfaction for all patients. They
found that postoperatively only one patient had diplopia occasionally but he
was satisfied with the surgery. These findings made them suggest that extreme
pseudophakic monovision could possibly be effective for elimination of
diplopia.
Hybrid monovision was selected for presbyopia correction by Iida et
al[21]. The mean binocular VA at all
distances was at least 0.10 logMAR, with significantly better results for
binocular vision than monocular vision from 0.50 to 5 m (P<0.05). In
addition, binocular contrast sensitivity was better than monocular in the eye
with multifocal IOL. The 62.50% of patients achieved normal range of near
stereopsis. Evaluating the reading ability of patients, the researchers
estimated the mean reading acuity of 0.10±0.10 logMAR, the mean maximum reading
speed of 418.00±55.80 characters/min and the mean critical character size was
0.31±0.11 logMAR. The reading outcomes supported that patients could read
newsprint without problems. Only 18.80% of patients used glasses
postoperatively. The 84% of patients were satisfied with this technique. The
satisfaction rate was better in patients younger than 60y. Dysphotopsia
symptoms, such as glare, halo or waxy vision were not mentioned. However, lack
of intermediate or near visual clarity made some patients dissatisfied.
In another study[2] that dealt with
pseudophakic monovision technique, most patients achieved excellent visual
function (UDVA/UNVA, stereopsis,contrast sensitivity). Only 1 patient was
generally dependent on spectacles, but he had a satisfaction score of 8/10.
Patients who used spectacles occasionally, more often for near vision, remained
very satisfied. Although there was one patient who needed laser treatment for
retinal tear without retinal detachment postoperatively, none of patients
needed refractive correction.
Greenbaum[12] divided patients in two
groups (clear lens group and cataract group) and evaluated the outcome of
pseudophakic monovision correction. The 91% of cataract patients and 95% of
patients in clear lens group reported at least 20/30 or J1 or both for distance
and near vision without correction, respectively. The method was acceptable
with high percentages for both groups (90% for cataract group and 100% for
clear lens group). There was no morbidity related to pseudophakic monovision
technique.
DISCUSSION
The present review assessed several clinical trials of pseudophakic
monovision for presbyopia correction after cataract surgery. After an intensive
research, both descriptive and comparative studies were elected from the
scientific literature. In most comparative studies pseudophakic monovision
technique was compared with the implantation of multifocal IOLs[2,9,22,25-26,28-30,33],
while accommodating IOLs implantation was compared to mini-monovision technique
in one study[28]. The researchers of one comparative
study used conventional and crossed methods of pseudophakic monovision
technique[32].
The evaluation of visual performance postoperatively was an important
parameter that was worked out in many trials. It was demonstrated that
monovision technique could provide very good[18]
to excellent[15,19-20]
distance visual outcome, without statistically significant differences when
compared to multifocal or accommodating methods[28].
Pseudophakic monovision was considered to be an alternative option for
correction of near vision[9], as it was
significantly improved postoperatively. Researchers showed that there was not
statistically significant difference in UNVA between monovision patients and
multifocal or accommodating groups[24,27,29]. However, Wilkins et al[30]
resulted that multifocal group dominated in the assessment of near VA, with a
significant difference. Crossed monovision technique had similar results to the
conventional method in visual outcomes from near to far[32].
Another parameter examined by researchers[2,10,30] was contrast sensitivity. Some
data indicated that contrast sensitivity was decreased at high frequencies but
still remaining in normal range in some cases[2,10]. Wilkins et al[30]
showed that patients of monovision group had significantly better outcomes than
multifocal patients.
There is great concern about the effect of pseudophakic monovision in
stereovision. Hayashi et al[34] supported
that several parameters could influence the stereopsis outcomes of pseudophakic
patients, including age, differences in VA and spherical equivalent, axial
length between eyes, astigmatism, aniseikonia, pupil diameter, and IOL
decentration. Ito et al[16] found positive
correlation between preoperative near exophoria angle and postoperative near
stereopsis, as exophoria less than 10.00 D provided significantly better
stereopsis outcomes in pseudophakic monovision patients. In most trials[2,9-10,14,19,21], there was a relative reduction
of stereoacuity in monovision patients. The percentage of patients who were
within normal range of stereoacuity varied from 63%[19-20] to 87%[10,14],
however it did not affect the rate of satisfaction with the technique. Few
research data suggested that stereoacuity of patients postoperatively was significantly
better in multifocal group than in monovision group[22,30]. However, further studies are needed to clarify the
relationship of pseudophakic monovision and stereovision.
Spectacle independence after presbyopia correction remains the main
demand of patients who undergo pseudophakic monovision, which renders this a
challenge for contemporary ophthalmologists. Regarding this parameter,
pseudophakic monovision could provide great reduction of spectacle use
postoperatively[2-3,10,14-15,18-19,21], achieving comparable outcomes with the implantation
of multifocal IOLs[23,27,33]. However, there were studies that showed significant
superiority of multifocal technique in this field[25,29-30]. Results of another research
demonstrated that multifocal patients had significantly less dependence on
spectacles for near vision[29]. Further
investigation is required in order to draw safer conclusions about the effect
of monovision in spectacle independence, as the postoperative use of glasses
has a significant influence in everyday life and general satisfaction of
patients.
The effect of pseudophakic monovision in daily activities was one of the
elements examined in the eligible studies[15,22,24,33].
According to the outcomes, monovision patients had significantly less
difficulty during computer work without glasses[22,33]; they had also significantly better reading ability
than multifocal patients[24]. Regarding driving
the outcomes were slightly better for monovision group[22].
In order to come to a reliable conclusion, some researchers used
questionnaires to estimate the functionality of patients postoperatively, the
rate of spectacle use and possible complaints. The answers given affected the
overall satisfaction with the method of monovision. Patients after pseudophakic
monovision achieved high scores of general satisfaction[10-11,15,19,22,30-31,33],
especially in age groups over 70y[10-11,14]. Both mini-and full-monovision methods provided
similarly high levels of satisfaction, comparable to those of multifocal technique[15]. More specifically, pseudophakic monovision arm
presented slightly higher satisfaction with cost, willingness to propose the
procedure to family and total satisfaction as well[22],
without statistically significant difference comparatively with multifocal arm[22,30]. The comparison of conventional
and crossed monovision had similar outcomes concerning spectacle use and
patients’ satisfaction[32].
Main causes for dissatisfaction of monovision patients were spectacle
dependence, asthenopia and lack of visual clarity for intermediate and near
vision[14,19,21].
Patients younger than 60y had higher rate of dissatisfaction and spectacle use
postoperatively[10,14], so the
performance of monovision in these age groups should take place after careful patient selection. Among
the reasons for patients’ dissatisfaction were often dysphotopsia symptoms,
which were significantly more often in multifocal groups[22,29-30].
Postoperative complications after pseudophakic monovision were reported
in two of the eligible studies. In the first one[2],
the patient required laser treatment for a retinal tear without retinal
detachment 4mo after cataract surgery, without need for refractive correction
or IOL exchange. In the other study[30], one
patient received multifocal IOLs due to an administrative error and another
underwent LASIK surgery to reduce myopia in the “near” eye.
To our knowledge, only one study[8]
evaluated the effect of pupil size on VA in pseudophakic monovision technique.
Researchers indicated that decrease of pupil diameter and increase of myopia
gradually led to an improvement of near VA. We believe that these findings
should be taken into consideration and more investigation in this direction is
required to reveal a possible role of pupil size in the success of monovision
technique. Another parameter affecting success of monovision is the optimal
anisometropia which was estimated to be 1.00 to 1.50 D[7,17].
The new approach of hybrid monovision[21],
where a monofocal IOL is placed in the dominant eye and a diffractive
multifocal IOL in the non-dominant eye, was believed to be an effective option
for patients with presbyopia symptoms. Patients who underwent this method had
significantly better VA outcomes at all distances binocularly than monocularly.
This new technique may be a suitable option for patients younger than 60y, as
especially in this age group satisfaction rate was at high levels. Moreover,
this could be a promising method for patients with unclear vision after
multifocal IOLs implantation, as dysphotopsia symptoms did not appeared in the
participants of this study. Nevertheless, in cases where perfect near vision
would be essential for work or lifestyle requirements, hybrid monovision was
believed not to be the optimal
approach, as it was associated with the lack of visual clarity at near and
intermediate distances. However, to date, only few research data concerning
hybrid monovision is available in
literature.
In conclusion, pseudophakic monovision is a safe and promising
alternative for presbyopia correction after cataract surgery, with comparable
efficacy to other relative techniques. This review indicated that monovision
technique can achieve equally good visual outcomes and probably less
dysphotopsia symptoms than multifocal IOLs implantation. There is concern about
some visual functions such as stereoacuity and contrast sensitivity, as few
research data signified a relative decrease in postoperative evaluation.
Satisfaction was kept in very high rates, especially for elderly patients.
Spectacle independence rates were also high. There is some evidence that
multifocal patients were more independent, however, even patients who declared
not to be fully independent from glasses remained satisfied with monovision. Our review suggests that
pseudophakic monovision is a viable and effective method for presbyopia
correction after cataract extraction, approachable to all budgets[2,29,35]. However,
careful patient selection is crucial for successful outcomes. Further
investigation is required in order to clarify probable drawbacks, restrictions
and new directions of monovision technique.
ACKNOWLEDGEMENTS
Conflicts of Interest: Labiris G, None; Toli A, None; Perente A, None; Ntonti P, None; Kozobolis
VP, None.
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