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Study shows multifocal IOL implantation provides good binocular
vision
Stefanie Petrou-Binder MD in Ludwigshafen
PATIENTS implanted with distance-dominant multifocal IOLs in one
or both eyes experience good stereoacuity that does not benefit
from additional near-vision correction, report German researchers.
Andreas Reuland MD and his colleagues conducted a clinical study
that investigated near-oriented stereoacuity in 33 patients who
received multifocal IOLs in one or both eyes. The surgeons performed
uncomplicated cataract surgery in each patient and implanted 50
SA 40 N, AMO Array IOLs (Advanced Medical Optics). The AMO Array
is a distant-dominant, multizonal, refractive silicone multifocal
IOL.
Sixteen patients, mean age 55 years, received the multifocal IOL
in one eye. Another seventeen patients, mean age 59 years, underwent
bilateral implantation of the lens. Their ages averaged 59 ±
12 years. The study excluded patients with amblyopia or unusual
orthoptic conditions.
The researchers tested stereoscopic vision at various times between
three months and three years after multifocal implantation. They
implemented the Lang Test ("cat" 1200 sec. arc, "star"
600 sec. arc, "car" 550 sec. arc) and the TNO random dot
stereo-test (480-15 sec. arc), with and without near visual correction.
Dr Reuland explained that smaller sec. arc. values indicate better
stereoacuity. The Lang test uses like images, slightly set apart,
that eyes with stereoscopic vision should be able to superimpose,
forming one image. Therefore the cat is the easiest to superimpose
requiring 1200 sec. arc., while the car can be superimposed at 500
sec. arc.
The sixteen eyes with unilateral multifocal IOL implantation achieved
uncorrected near visual acuity of 0.4 (± 0.2). Their best
corrected near visual acuity was 0.6 (± 0.2). Twelve of the
sixteen one-sided study participants recognised the car image (550
sec. arc) in the Lang test. Two additional patients recognised the
car image with the aid of near visual correction.
The TNO Stereo-test results revealed that nine out of sixteen unilateral
patients achieved stereoscopic visual acuity of 140 (± 80)
sec. arc. Seven patients could not recognize anything. Two of these
patients profited from near visual correction. With the help of
near visual correction, ten of the sixteen patients in this group
attained stereoacuity of 130 (± 70) sec. arc.
The
investigators measured the uncorrected near visual acuity of the
seventeen bilaterally implanted patients at 0.45 (± 0.2).
Their corrected near visual acuity averaged at 0.7 (± 0.3).
The Lang Test revealed that fourteen patients in that group could
recognise the car (550 sec. arc). One further patient recognised
the car with near visual correction.
Ten of the seventeen patients achieved stereoscopic visual acuity
results of 180 (± 140) sec. arc in the TNO Stereo-test. As
in the unilateral group, seven of the binocular group patients recognised
nothing. Another three profited from near visual correction. With
near visual correction, eleven out of seventeen patients had stereoacuity
of 160 ± 150 sec. arc.
Dr Reuland explained that older patients who receive monofocal IOLs
have reduced stereoacuity. Binocular vision is one of the visual
functions that researchers have often neglected to include in their
functional study results after cataract surgery. He pointed out
that few studies as yet can attest to the effects on stereoacuity
following multifocal IOL implantation in one or both eyes.
He noted that the development of so-called 'comfort IOLs' such as
aspherical and blue-filter IOLs (AcrySof Natural) have called an
increasing amount of attention to high scoring visual acuity and
functional tests that do not, however, necessarily include binocular
visual acuity.
He emphasised that his study showed that some two-thirds of the
patients in both the patient groups achieved good functional stereoscopic
visual acuity without additional visual aids. Near visual correction
did not provide a significant improvement in either group.
Dr Reuland suggested that stereoscopic visual tests be carried out
on elderly patients receiving monofocal IOLs, as well.
Although H Burkhard Dick, MD has not been testing IOL recipients
for stereoacuity at the Mainz University Eye Clinic, he does consider
Dr Reuland's multifocal investigation promising.
"Patient age decreases the quality of stereopsis. Older patients,
like those in Dr Reuland's investigation, are not expected to have
good near stereoacuity. The study results highlight another interesting
aspect of multifocal efficacy, which provides these patients with
an improved quality of life."
Dr Dick contended however that it may be better to implant multifocal
IOLs bilaterally, as studies have affirmed an advantage, primarily
for improving anisometropia, as well as providing better stereoacuity
outcomes.
He said that including stereoacuity in the roster of functional
tests that ophthalmologists perform post-operatively might swamp
clinicians. Stereoacuity investigations are more interesting from
a scientific than every-day viewpoint.
Not all trials seem to concur with that of Dr Reuland in terms of
a unilateral/bilateral advantage for improved stereoacuity results.
Anja Liekfeld MD investigated stereoscopic vision in eyes implanted
with different lens types, both mono- and multifocal, in a trial
involving 153 young and older phakic patients (Ophthalmologe 2002,
Jan;99(1):20-4). Lenses were implanted uni- and bilaterally.
The outcome of her investigation revealed that all of the patients
with both bilaterally implanted multifocal IOLs and bilaterally
implanted monofocal IOLs had good binocular vision, for far and
near. The patients with unilaterally implanted lenses scored lowest.
Andreas
Reuland MD
Ruprecht-Karls-University Heidelberg Eye Clinic
Heidelberg, Germany
andreas.reuland@med.uni-heidelberg.de
H Burkhard Dick MD
Mainz University Eye Clinic, Mainz, Germany
bdick@mail.uni-mainz.de
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