Download managing residual refractive errors and

CATARACT SURGERY
MANAGING RESIDUAL
REFRACTIVE ERRORS AND
POSTOPERATIVE ASTIGMATISM
Proper understanding of the patient’s expectations and accurate measurement of
residual refractive error are key.
BY JILL S. ZAVERI, MD; AND JONATHAN B. RUBENSTEIN, MD
M
any cataract patients today expect emmetropia
and spectacle independence postoperatively.
In order to meet these expectations, an understanding of residual refractive errors and their
management is increasingly important.
Residual refractive errors can be related to a variety of factors. There may be errors in the preoperative assessments of
axial length and corneal power, an unknown history of prior
refractive surgery, incorrect IOL placement or positioning, or
residual regular or irregular corneal astigmatism. Decreased
visual acuity may also result from ocular surface pathology, posterior capsular opacity, and macular or optic nerve
pathology. Not meeting patient expectations can make even
small residual errors appear to be large ones.
ASSESSING THE ERROR
First and foremost, it is important to listen to the patient
to understand the exact nature of his or her complaints.
Does he or she desire improved distance vision, near vision,
or both? Is he or she amenable to spectacles or contact lenses, or is further surgery required to achieve satisfaction?
Proper assessment allows accurate patient counseling on
procedural options and helps set appropriate expectations.
Good ocular surface health is necessary to optimize postoperative results; conditions such as blepharitis and dry eye must be
cleared up and the refraction must be stable prior to planning
further surgery. Additionally, the surgeon must accurately assess
the spherical and astigmatic refractive error and differentiate
between regular and irregular astigmatism. Conveying to the
patient that enhancements are occasionally necessary is an
important part of both pre- and postoperative counseling.
CASE PRESENTATIONS: WHEN TO ENHANCE
The decision of when to enhance is not related to a particular
visual acuity. Enhancement becomes relevant when the patient
is unhappy with his or her postoperative outcome. Options for
enhancement include spectacles, limbal relaxing incisions (LRIs),
34 CATARACT & REFRACTIVE SURGERY TODAY EUROPE | JULY/AUGUST 2015
laser vision correction, IOL exchange, and piggyback IOL placement. The following five case presentations illustrate when to
utilize these options.
Patient No. 1. A 65-year-old man underwent uncomplicated
phacoemulsification in his left eye. At 1 month postoperative,
his UCVA was 20/50 OS. BCVA was 20/20 with a manifest
refraction of -1.00 +1.50 X 85º.
This case illustrates decreased visual acuity from residual astigmatism despite a spherical equivalent near plano. Therefore,
Patient No. 1 could be managed with paired LRI incisions on
the steep corneal axis. Because of the coupling effect, LRIs can
reduce astigmatism without changing the spherical power. This
patient’s spherical equivalent was -0.25 D, making him a good
candidate for this procedure. LRIs are relatively easy to perform,
fairly inexpensive for the patient, and can be done in a minor
operating room or at the slit lamp. Several LRI nomograms are
available, including those by Louis D. “Skip” Nichamin, MD; Eric
D. Donnenfeld, MD; and Douglas D. Koch, MD. The procedure
can be performed with a diamond blade or femtosecond laser.
Generally, the depth of the incision is 600 μm, depending on the
patient’s pachymetry. It is important to remember that these
procedures specifically treat postoperative refractive cylinder,
not corneal astigmatism alone. This patient required paired LRIs
with 40° of arc at the 85° axis to treat the refractive cylinder.
Patient No. 2. A 63-year-old pilot underwent cataract extraction and IOL implantation in both eyes. A monofocal implant
was placed in each eye, and postoperative UCVA was 20/40 OD
and 20/20 OS. A manifest refraction OD of -1.50 +1.25 X 80º
yielded 20/20 BCVA; however, the patient was not interested
in spectacle correction. Therefore, it was determined that the
residual myopic astigmatism would best be corrected with laser
vision correction. LASIK or PRK can be used in conjunction with
toric and nontoric monofocal IOLs but should be used selectively in patients with multifocal IOLs.1
Because Patient No. 2 had a myopic spherical equivalent, he
would not have been fully corrected by astigmatic keratotomy
alone. An excimer laser procedure can treat both residual
placed in the anterior chamber, or the leading haptic can be
placed into the ciliary sulcus. The trailing haptic is then inserted
into the eye and tucked under the iris using a hook. Positioning
the piggyback IOL in the sulcus should create separation
between the piggyback IOL and the IOL in the capsular bag.
There should also be a slight separation between the anterior
piggyback IOL and the posterior iris. Once the new IOL is in the
appropriate position, the OVD is removed from the eye and
corneal incisions are closed with either stromal hydration or
sutures. The learning curve is short for most surgeons because
the steps required to place a piggyback IOL are similar to the
steps used in most cataract and anterior segment surgeries.3
Patient No. 4. A 72-year-old woman reported decreased
vision in her left eye for 6 to 9 months. Her BCVA OS was
20/60 with manifest refraction of -6.25 +1.75 X 32º. Her
exam was consistent with decreased vision from cataract.
A standard surgical plan was created with biometry and
IOLMaster (Carl Zeiss Meditec) calculations. The axial length
of her left eye was 25.62 mm. The IOLMaster keratometry
(K) reading was 42.67 X 45.00 at 120° - ∆K = 2.23, which
was similar to the Orbscan (Bausch + Lomb) K reading of
43.1 X 45.3 at 122° - ∆K = 2.2. A Tecnis Toric ZCT400 one-piece
lens (Abbott Medical Optics) was calculated to be oriented at
115°, with anticipated residual cylinder of 0.04 D at 115°. Surgery
was uneventful, and a 17.00 D Tecnis Toric lens was placed at
115°. The target refraction for this patient was -1.60 D.
On postoperative day 1, Patient No. 4 achieved a near UCVA
of J3; however, she complained of double images and ghosting.
These symptoms could be caused by ocular surface irregularity,
induced astigmatism related to wound healing, IOL decentration
or tilt, axis alignment error, or an error in IOL power calculation.
After 10 days, the patient’s near UCVA was the same. On slitlamp exam, the IOL appeared to be oriented at 160° instead of
the intended 115°. Although estimation of the postoperative toric
IOL axis can be difficult, a slightly more precise measurement can
be made at the slit lamp using the iHandy Level (iHandy; https://
itunes.apple.com/us/app/ihandy-level-free/id299852753?mt=8)
or Axis Assistant (designed by José Miguel Varas, MD, and coded
AT A GLANCE
• Factors contributing to residual refractive errors can
include errors in the assessment of axial length and
corneal power, an unknown history of prior refractive
surgery, incorrect IOL placement or positioning, and
residual regular or irregular corneal astigmatism.
• Proper assessment allows accurate patient counseling on the
procedural options and helps set appropriate expectations.
• Spectacles, LRIs, LASIK or PRK, IOL exchange, or piggyback IOL implantation are all management options at the
surgeon’s disposal for solving postoperative refractive issues.
JULY/AUGUST 2015 | CATARACT & REFRACTIVE SURGERY TODAY EUROPE 35
CATARACT SURGERY
astigmatism and myopia, and this is currently one of the most
accurate methods of refractive enhancement.2 Although LASIK
leads to faster visual recovery and minimal discomfort, the procedure carries the potential for flap-related complications. PRK
does not require a flap and leads to fewer basement membrane
issues than LASIK; however, visual recovery is slower, and the
procedure is associated with more pain and the risk of transient
corneal haze. After a PRK enhancement, this patient was happy
and 20/20 by about 3 months postoperatively.
Patient No. 3. A 60-year-old woman presented with a history
of LASIK for myopia. She did not have access to any of her old
medical records and had visually significant cataracts in both
eyes. UCVA was 20/50 OD and 20/60 OS. The patient’s corneas
were clear, with LASIK flaps noted in both eyes. Also in both
eyes, the lenses had 2+ nuclear sclerosis, 2+ cortical spokes, and
1 to 2+ posterior subcapsular cataract changes. The remainder
of the exam was normal.
Cataract extraction with IOL placement OD was uneventful;
however, the postoperative UCVA in Patient No. 3 was 20/60
at 1 and 2 months postoperative. With 2.00 D of sphere, BCVA
was 20/20. The small degree of hyperopic refractive error without astigmatism made her an ideal candidate for piggyback IOL
implantation. Considerations for this procedure include adequate anterior chamber depth, healthy endothelium, a stable
refraction, and minimal astigmatism. Contraindications include
pigment dispersion syndrome, zonular weakness, pseudoexfoliation, presence of a capsular tension ring (CTR), low endothelial
cell count, and significant astigmatism (although toric piggyback
IOLs are available outside the United States).
Piggyback IOLs are usually of low power (-4.00 to 4.00 D). Two
commonly used lenses have been the Clariflex (Abbott Medical
Optics) and the STAAR AQ5010 (STAAR Surgical), although
the former is no longer available. The STAAR AQ5010 is a threepiece silicone IOL with a thin profile and a 6.3-mm optic. It has a
14-mm overall diameter with 10° of posterior angulation to keep
the lens optic away from the posterior iris. Silicone lenses avoid
interlenticular opacity with a bag-fixated acrylic IOL.
The piggyback IOL’s power is entirely dependent on the
pseudophakic manifest refraction. The spherical equivalent of
the manifest refraction and the A-constant of the piggyback IOL
are all that is necessary for power calculation. For patients with
postoperative hyperopic refractive error, the spherical equivalent
should be multiplied by 1.5 to find the proper piggyback IOL
power. For patients with postoperative myopic refractive error,
the spherical equivalent should be multiplied by 1.2 to find the
proper lens power. IOL power calculations can also be made
using the Holladay R formula, the Gills nomogram, or the refractive vergence formula from Warren E. Hill, MD. Because the postoperative manifest refraction in this case was 2.00 D of sphere,
the patient required a 3.00 D STAAR AQ5010V piggyback IOL.
The surgical technique for inserting a piggyback IOL is similar
to that for primary IOL implantation. A cohesive OVD is used
to distend the ciliary space. At this point, the entire lens can be
CATARACT SURGERY
“
Not meeting patient
expectations can make
even small residual
errors appear
to be large ones.
by Evandro Souza; https://itunes.apple.com/us/app/axis-assistant/
id843536178?mt=8) smartphone apps. With these apps, the
rotated slit beam is first oriented with the axis of the toric IOL.
Then, the axis of the virtual level is oriented with axis of the
rotated slit beam, at which point freezing the level in the app will
measure the exact axis.
In this scenario, a secondary surgery for IOL rotation should be
considered if the poor postoperative vision is secondary to the
IOL being off-axis. Higher toric corrections have a larger impact
on visual outcome; a 10° error in placement can lead to a 33%
loss of effectiveness in the final outcome.4 It is also important
to ensure that there is no significant spherical equivalent error.
If error in the spherical equivalent is the true cause of the postoperative refractive error, then rotating the IOL may not fully
alleviate the patient’s visual complaints. Surgical planning for IOL
rotation can be enhanced by using the Astigmatism Fix calculator (www.astigmatismfix.com) developed by John P. Berdahl,
MD, and David R. Hardten, MD, FACS. Lastly, posterior capsule
and zonular integrity is essential to successfully rotating an IOL.
IOL rotation is best done at 2 to 4 weeks postoperative when
refraction and measurements are stable. In the operating room,
the surgeon marks the intended axis, reinflates the bag with
cohesive OVD, and rotates the IOL until the lens is close to the
intended orientation. If intraoperative aberrometry is available,
this can be used to check for residual cylinder once the IOL has
been rotated. The OVD is carefully removed from around the
IOL, and the orientation of the IOL is confirmed once more. The
IOL can be left in the capsular bag, or reverse optic capture can be
used to stabilize the IOL with or without the use of a CTR.
In this case, IOL rotation was performed 2 weeks postoperatively with the placement of a CTR. On postoperative day 1,
near UCVA in Patient No. 4 was J1+ without ghosting. The IOL
was oriented at 118°, and refraction detected minimal residual
cylinder. After 2 weeks, her near UCVA was J1 with stable orientation of the IOL.
Patient No. 5. A 67-year-old engineer with recent multifocal IOL placement in both eyes presented with distance UCVA
of 20/25 and near UCVA of J1 in both eyes. He complained of
halos, glare, and trouble reading in low light. He was unhappy
with his overall quality of vision, which was not improved after
a trial in spectacles. Topography measurements and endothelial cell counts appeared normal. The patient wondered if an
36 CATARACT & REFRACTIVE SURGERY TODAY EUROPE | JULY/AUGUST 2015
Nd:YAG laser procedure might help him. The best option for
an unhappy patient after uncomplicated cataract surgery with
a normal corneal endothelium, normal topography, and good
distance and near refractive outcome may simply be an IOL
exchange. For Patient No. 5, an uncomplicated IOL exchange
did resolve the visual aberrations.
IOL exchange is useful if there is an error in the spherical or
cylindrical goal or if the patient is unhappy with the quality of
his or her vision, including glare and visual aberrations. If the
exchange is planned early in the postoperative course and the
bag is intact, an IOL exchange with placement of the new IOL in
the bag is an option. If the exchange is planned late in the postoperative course and the posterior capsule is open, an exchange
can be done with placement of the new IOL in the sulcus. The
need for anterior vitrectomy in this setting is significant.
Considerations for IOL exchange include the type and placement of the initial lens implant, the endothelial cell count, and
the presence of persistent inflammation. The need for microsurgical scissors and forceps, an anterior vitrectomy, use of suture
fixation, and CTRs or capsular tension segments should be
anticipated. Peribulbar local anesthesia should be considered, as
the case may require extensive manipulation. During the procedure, OVD is injected between the capsule and the existing IOL,
as this allows gentle rotation and prolapse of the IOL out of the
bag. The old IOL is cut or folded to remove it from the anterior
chamber, and the new IOL is placed in the sulcus or the bag
depending upon capsular integrity.
CONCLUSION
The key to managing residual postoperative refractive error
is listening to the patient, understanding his or her expectations, and accurately measuring the residual refractive error.
Ensure that the refractive error has stabilized before performing
further surgery. Also, always take corneal regularity, IOP, and
macular health into account prior to surgery or subsequent
intervention. Once the problem has been defined, spectacles,
LRIs, LASIK or PRK, IOL exchange, or piggyback IOL implantation are all management options at the surgeon’s disposal for
solving postoperative refractive issues. n
1. Piñero DR, Ayala Espinosa MF, Alió JL. LASIK outcomes following multifocal and monofocal intraocular lens implantation. J
Refract Surg. 2010; 26(8):569-577.
2. Alio JL, Abdelghany AA, Fernandez-Buenaga R. Management of residual refractive error after cataract surgery. Curr Opin
Ophthalmol. 2014;25(4):291-297.
3. Rubenstein JB. Piggyback IOLs for residual refractive error after cataract surgery. Cataract &Refractive Surgery Today. 2012;28-30.
4. Roach L. Toric IOLs: four options for addressing residual astigmatism. Eyenet. 2012;29-31.
Jill S. Zaveri, MD
phthalmology Resident, Rush University Medical Center, Chicago
O
[email protected] n Financial disclosure: None
n
n
Jonathan B. Rubenstein, MD
Vice Chairman and Deutsch Family Professor of Ophthalmology,
Rush University Medical Center, Chicago
n [email protected]
n Financial disclosure: None
n