Download treating cataracts and Irregular Astigmatism

Cataract SURGERY
Treating Cataracts and
Irregular Astigmatism
Irregular astigmatism can be addressed before, during, or after surgery, with the best choice
depending on the patient’s individual characteristics.
By Justin Schweitzer, OD
C
ataracts and irregular corneal astigmatism are
conditions that are often encountered simultaneously by eye care providers. Conditions such
as Salzmann nodular degeneration, pterygium,
epithelial basement membrane dystrophy (EBMD), keratoconus, corneal ectasia, corneal scars, and ocular surface disease often induce irregular astigmatism.1,2 These
conditions present additional challenges when cataract
surgery is imminent.
Depending on its cause and severity, irregular astigmatism can be addressed before surgery with phototherapeutic keratectomy (PTK), at the time of cataract surgery
with astigmatic keratotomy (AK) or toric IOLs, or after
surgery with specialty contact lenses. Each technology is
indicated in different conditions and situations.
Preoperative Evaluation
A detailed cataract workup should be performed on
all patients prior to surgery. Workups include corneal
topography, optical biometry measurement to calculate
IOL power, and evaluation of the anterior and posterior
segments.
Conditions such as keratoconus, corneal ectasia,
and other subtle irregularities of the cornea are best
discovered with corneal topography. Corneal topographers provide the best assessment of the degree of
astigmatism present,
its location, and the
severity of the irregularity. Topographers
also assist in obtaining
accurate corneal curvature measurements
that can be used in
determining the correct IOL power for
the patient. Salzmann
nodular degeneration,
pterygia, EBMD, corneal
scars and other corneal
dystrophies will usually
be seen on slit-lamp
examination, and the
amount of astigmatism
can be quantified with
topography. If the
irregularities are subtle
and the astigmatism
Figure 1. An 85-year-old patient presented with decreased vision (20/40) with a topography that
is regular, the eye care
exhibits irregular astigmatism and a questionable early keratoconic pattern. Anterior segment
provider can move
examination revealed significant ocular surface disease.
forward with preparing
July/August 2014 Advanced ocular care 1
Cataract SURGERY
Treatment
of Irregular
Astigmatism
at the Time
of Cataract
Surgery
Toric IOLs and
AK are important
tools in the arsenal
for treating cataracts
and astigmatism at
the time of surgery.6
The arcuate incisions used in AK
can be a powerful
tool for correcting
regular astigmatic
corneas, but when
the cornea is irregular they can further
destabilize the cornea and cause more
irregularities.7 Toric
Figure 2. Same patient as Figure 1 after 4 weeks of aggressive dry eye treatment. The irregularity of the IOLs have the ability
cornea has decreased, and it is now beginning to have a more symmetric, regular topographic pattern.
to correct
1.00 D to slightly
the patient for cataract surgery. In situations in which
more than 4.00 D of astigmatism.6,8 These implants
the irregularities are significant, treatment may be necwork best in eyes that have regular astigmatism, but in
essary before surgery to facilitate accurate IOL power
some situations they can be used in eyes that have a
calculations.
mild amount of irregular corneal astigmatism.
Patients with mild irregularities who have recently
Treatment of Irregular Astigmatism
done well with spectacle correction are good candibefore Cataract Surgery
dates to consider for a toric IOL. Those who achieve
Accurate IOL power calculations can be difficult to
good vision with spectacles have fairly regular and symobtain with many conditions that cause irregular astigmetric corneal astigmatism, as eyeglasses will not fully
matism. In certain situations, treating the corneal surface correct irregular astigmatism.9
Certain corneal conditions that show irregularities
first and then repeating IOL calculations and corneal
topography maximizes accuracy. Patients with advanced on corneal topography, such as mild keratoconus and
mild corneal ectasia, can also do well with a toric IOL.
Salzmann nodules or EBMD may benefit from a PTK to
Evaluating the central 3 to 5 mm on corneal topograreduce the irregularities of the corneal surface.3,4 Ocular
surface disease can cause significant changes to the corphy helps to determine the degree of irregularity overneal surface and should be treated aggressively before
lying the pupil. Regardless of irregularities in peripheral
cataract surgery (Figures 1 and 2).2 A pterygium can
zones, if the central 3- to 5-mm zone is reasonably
induce several diopters of irregular astigmatism, and it
regular the patient will likely do well with a toric IOL
may warrant surgical removal before moving forward
(Figure 3).10
5
with cataract surgery.
Treatment of Irregular Astigmatism
Once these conditions are treated, repeating IOL calAfter Cataract Surgery
culations and corneal topography is necessary. In some
Patients who present with keratoconus, corneal ectacases previously irregular corneas will return to a regular
sia, corneal scars, and other irregularities may benefit
astigmatic shape. The eye care provider can then profrom a specialty contact lens fitting after implantation
ceed with choosing a surgical plan based on accurate
of a nontoric monofocal IOL. Looking closely at corneal
biometric data to ensure good patient outcomes.
2 Advanced ocular care July/August 2014
Cataract SURGERY
(Figure 4). If the patient
has previously worn a
specialty contact lens,
such as a rigid gas permeable (RGP) lens, and
he or she wants to continue wearing contacts
after cataract surgery,
then a nontoric IOL
may be the best choice
for cataract surgery. If a
toric IOL is implanted
and the patient wants to
continue wearing a specialty contact lens, the
contact lens will mask
the corneal astigmatism
and thus unmask the
lenticular astigmatism
from the toric IOL. The
design of the specialty
contact lens would then
Figure 3. Topography of a 49-year-old man with previous PKP preparing to have cataract surhave to have an anterior
gery. Note the regularity of the central 3- to 5-mm zone. The decision was made to implant a
toric surface to balance
toric IOL because of the regular nature of the central 3- to 5-mm zone.
out the unmasked toric
IOL effect.11,12
Certain patients will present with corneas that are
highly irregular or unstable. In these cases the eye care
provider must decide if a specialty contact lens fitting
will be possible after cataract surgery or if the patient
would benefit from penetrating keratoplasty (PKP)
with subsequent cataract surgery.13 A discussion with
the patient is imperative to set expectations and determine the patient’s comfort level for proceeding with
a specialty contact lens fitting after cataract surgery. If
the eye care provider believes that an accurate contact
lens fit will not be attainable or the patient does not
have a desire to wear a contact lens, then PKP with
subsequent cataract surgery will likely yield the best
outcome, despite the long postoperative recovery.
Figure 4. A 16-mm diameter scleral contact lens fit on a
47-year-old man with keratoconus who underwent cataract
surgery.
topography readings, considering any previous corneal
surgery, and determining if the patient is capable of
wearing a specialty contact lens will help in making this
decision.
Cataract surgery with a planned postoperative contact lens fitting can be a powerful tool in cases in which
significant corneal irregularity exists but it is difficult
to decide in what axis the toric IOL should be placed
Case Study
A 47-year-old man was referred to our center with
complaints of decreased near and distance visual acuity,
glare and halos at night. He had a history of keratoconus and successful RGP contact lens wear over the past
15 years. He wondered if a corneal transplant and cataract surgery would help his vision.
Three years before the patient presented to our center, his BCVA with RGP contact lenses was 20/20 in the
right eye and 20/60+ in the left. His BCVA at this visit
was 20/40 in the right eye and 20/400 in the left. RGP
July/August 2014 Advanced ocular care 3
Cataract SURGERY
Figure 5. Topography OD showing keratoconus.
Figure 6. Topography OS showing keratoconus.
over-refraction improved the BCVA in his right eye to
20/20 but showed no improvement in the left.
Brightness acuity testing was 20/400 in the right eye
and was not performed in the left. Intraocular pressures were 7 mm Hg in the right eye and 8 mm Hg in
the left. Ultrasound pachymetry was thin at 513 µm in
the right eye and 534 µm in the left.
Corneal topography (Pentacam; Oculus) confirmed
4 Advanced ocular care July/August 2014
significant keratoconus in
both eyes (Figures 5 and
6). Examining the topographies closely showed
inferior steepening in both
eyes, and, more important,
steepening and irregularity
in the central 3- to 5-mm
zone. Topography confirmed irregular, asymmetric astigmatism of nearly
10.00 D in the right eye
and 6.00 D in the left.
Anterior segment evaluation showed mild central
scarring consistent with
keratoconus in each eye.
Examination through a
dilated pupil revealed a
2+ posterior subcapsular
cataract in the right eye
and a 3+ posterior subcapsular cataract in the left.
Examination of the fundus
was normal.
Properly addressing the
irregular astigmatism was
the key decision point
in this case. A toric IOL
was not the best option
because of the significant
irregularity of his cornea
in the central 3- to 5-mm
zone on corneal topography and the mild corneal
scarring present centrally.
A combined procedure of a
corneal transplant plus cataract extraction is a consideration, but avoiding the
morbidity of PKP would be
desirable. Finally, cataract
extraction followed by a
specialty contact lens fitting postoperatively could be a likely solution. Because
this patient had worn contacts successfully for the
past 15 years and he has significant cataracts in both
eyes, it was felt that there was a good chance removing his cataracts and fitting him with a contact would
provide quality vision.
The patient agreed, and uneventful cataract surgery
was performed in the left eye. Three weeks postopera-
Cataract SURGERY
tively, the patient was successfully fit with a 16-mm
diameter scleral lens in the left eye, and his subsequent BCVA was 20/20. Uneventful cataract surgery
was then scheduled and performed in the right eye.
Three weeks postoperatively a 16 mm diameter scleral
lens was successfully fit in the right eye, and BCVA was
20/20.
Conclusion
Patients with cataracts and irregular corneal astigmatism present unique challenges in making cataract surgical decisions. Treatment of irregular astigmatism must
be personalized for each patient. Treatment of irregular
astigmatism preoperatively can be beneficial in obtaining more accurate IOL calculations. At times, patients
with mild irregularities or asymmetry in the central 3
to 5 mm of the cornea will be able to move forward
with surgery with consideration of implanting a toric
IOL. In other cases, patients with significant irregular
astigmatism may benefit from cataract extraction and a
postoperative specialty contact lens fitting. It is crucial
that eye care providers customize treatment for each
patient with cataracts and irregular corneal astigmatism. If irregular astigmatism is properly addressed,
successful surgical outcomes will be achieved to restore
vision. n
Justin Schweitzer, OD, is in practice at
Vance Thompson Vision in Sioux Falls, South
Dakota. He acknowledged no financial interest
in the product or company mentioned herein.
Dr. Schweitzer may be reached at [email protected].
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