Aug 2016

with
Prof Charles McGhee
& A/Prof Dipika Patel
Series Editors
Preoperative risk assessments to reduce
cataract complications
BIA Z. KIM, DIPIKA V. PATEL AND CHARLES N.J. MCGHEE
Cataract surgery is highly successful but
complications do occur and internationally
studies report an overall complication rate of
approximately 5%. Although not all complications
lead to poor outcomes, the occasional severe
complication can be blinding. With over 30,000
cataract surgeries performed each year in New
Zealand, even a small percentage of moderate
adverse outcomes adds up to hundreds of patients.
Numerous factors increase the risk of a
complication during and after cataract surgery.
Unfortunately, many of these factors are intrinsic
and unavoidable but prior identification of these
risk factors may allow optometrists and ophthalmic
surgeons to appropriately advise patients.
Subsequently, it may be possible to take appropriate
perioperative precautions and adjust intraoperative
techniques to try to reduce these risks.
Corneal opacity
One of the most apparent risk factors on slit-lamp
examination is corneal scarring or haze. If the
opacity is sufficient to obscure fine iris detail on
slit-lamp examination, it may prove problematic
during surgery. To maximise the red reflex during
surgery to facilitate capsulorhexis, the eye may
be manipulated into a better position and the
background or direct co-axial microscope light may
be altered to minimise backscatter of light from
the cornea and cataract. In very severe cases of
scarring, an external light pipe may occasionally
be useful to illuminate structures tangentially to
enable a safe capsulorhexis.
White/dense/mature cataracts
A dense cataract can present multiple problems
during surgery. The large lens may create positive
pressure and tension on the capsule and may
significantly shallow the anterior chamber. The
anterior capsule is also very difficult to visualise over
a white or brunescent cataract, increasing the risk of
a capsule tear or irregular capsulotomy.
The view of the capsule can be improved using
tissue staining e.g. Vision Blue (trypan blue
ophthalmic solution) injected into the anterior
chamber and washed out after it has stained the
anterior capsule blue (Fig 1.). Furthermore, a dense
cataract will require more phacoemulsification
energy than a soft lens. Since total ultrasound
energy can be associated with postoperative
corneal oedema and intraocular inflammation, a
phaco-chop technique that generally requires less
energy may be preferable. 1
Fig 1. Intraoperative photograph during capsulorhexis - anterior lens
capsule stained with Vision Blue over congenital white cataract.
Fuch’s endothelial corneal dystrophy
(FECD)
Other risk factors may be more subtle. Individuals
with mild FECD may be asymptomatic or unaware
of minor changes in vision. However, patients with
FECD are at greater risk of corneal decompensation
and need to be aware of the possible longer-term
consequences such as a corneal transplant. Thus
all corneas need to be examined carefully for signs
of FECD eg. guttata and increased pachymetry
(Fig 2.). A preoperative central corneal thickness
12 NEW ZEALAND OPTICS August 2016.indd
(CCT) greater than 620µm is associated with
an increased probability of requiring a corneal
transplant following cataract surgery and for each
10µm increase beyond 620µm, the odds of corneal
decompensation increase by 1.7 times 2 .
Damage to the compromised endothelium may
be prevented by reducing the flow of fluids in
the anterior chamber during surgery and using
a ‘soft-shell’ technique (a dispersive viscoelastic
device coats and protects the endothelium
while a cohesive viscoelastic deepens the
anterior chamber and maintains the working
space) 3 . Furthermore, torsional rather than
longitudinal phacoemulsification can reduce the
dissipated ultrasound energy, thereby minimising
endothelial injury 2 .
Pseudoexfoliation syndrome
Pseudoexfoliation is associated with a significant
number of problems in cataract surgery, including
poor pupillary dilation, zonular weakness
leading to zonular dialysis or lens dislocation
with vitreous loss, postoperative intraocular
pressure spikes, capsular phimosis, cystoid
macular oedema, prolonged inflammation, and
corneal decompensation. However, the white/
grey dandruff-like material mostly on the pupil
margin and anterior lens surface, indicative of
pseudoexfoliation, can be easily missed on casual
slit-lamp examination, especially with an undilated
pupil (Fig 3.). Peripupillary iris transillumination
and pigmented pupillary ruff atrophy may also
provide clues of underlying disease.
With prior knowledge of these risk factors the
patient can be better-informed and surgical
planning can be modified, eg. lower anterior
chamber irrigation rate, insertion of a capsular
tension ring, augmented pharmacological and/
or mechanical pupillary dilation (synechialysis, iris
hooks). Hydrodissection and hydrodelineation of
the cataract can cause further downward stress
and zonular compromise, thus should be performed
carefully. A zonule-friendly phaco-chop technique
and a gentle two-instrument rotation of the nucleus
are also helpful. It is also useful to work in the central
anterior chamber with copious viscoelastic, avoiding
the friable capsular periphery and shallowing of the
anterior chamber. Towards the end of the surgery,
thorough removal of viscoelastic is important in
minimising significant postoperative IOP spikes 4 .
Phacodonesis
Phacodonesis is the tremulousness or subtle
movement of the lens with eye movements,
which may occur due to a previous eye injury,
pseudoexfoliation or other causes of zonular
compromise or lens subluxation. Phacodonesis may
be detected by asking the patient to move their eye
quickly from side-to-side and up-and-down while
the clinician observes the eye on the slit-lamp. The
patient may also be asked to look directly ahead
while the clinician gently strikes the upright of
the slit-lamp head support 2-3 times (obviously
warning the patient beforehand). The transmitted
energy through the head/chin rest may produce a
flickering lens reflex or frank movement.
Similar adjustments can be made to surgical
techniques as previously highlighted in
pseudoexfoliation to reduce stress on the zonules
and also plan for additional techniques such as
sutured capsule tension segments or rings.
Anaesthetic
Generally, contemporary cataract surgery is
performed under regional (peri-bulbar/sub-
Tenon’s anaesthesia [STA]) or topical (drop/gel)
anaesthesia, with or without low-level oral or
intravenous sedation. A larger volume regional
anaesthesia may increase the intraocular pressure
and shallow the anterior chamber, occasionally
making surgery a little more difficult. Since an
incision is required in the infero-nasal conjunctiva
for STA it may be associated with subconjunctival
haemorrhage, that on occasion may be extensive.
Although not sight-threatening and self-resolving
over 7-14 days, the dramatic appearance may
Fig 2. Slit-lamp photograph showing corneal endothelium with guttata
in Fuch’s endothelial corneal dystrophy.
Fig 3. Slit-lamp photograph of white/grey pseudoexfoliative material on
pupil margin.
be unsettling for patients and relatives. Topical
anaesthesia may avoid any injections but requires
adequate patient cooperation, as the eye is able to
move much more freely during the procedure.
Therefore, preoperative assessments should
include potential language barriers, anxiety
levels, ability to lie flat for up to 30 minutes,
head tremors, and antiplatelet/anticoagulant
medications that may predispose to bleeding.
Systemic medications
Oral Doxazosin and similar alpha-blockers used
for prostatic and urinary symptoms are associated
with intraoperative “floppy iris syndrome” – the
iris billows and has a tendency to prolapse through
the surgical incisions whilst the pupil progressively
constricts during surgery. This can lead to extremely
complicated surgery and extensive iris damage.
Unfortunately, these issues are not resolved by
simply stopping the medication prior to surgery.
Thus ophthalmologists may need to consider a
number of strategies including: creating longer
corneal incisions and maintaining the anterior
chamber depth to prevent peripheral iris prolapse;
augmented pharmacological pupil dilation (e.g.
intra-cameral phenylephrine); and mechanical
dilation/iris stabilization (e.g. iris hooks or rings).
Inflammation
Intraocular inflammation such as chronic anterior
uveitis that is not entirely quiescent should
generally be controlled and stable for around six
months before embarking on cataract surgery.
Perioperatively, patients may require an increased
dose of corticosteroid or other immunosuppressive
therapy to reduce the risk of significant
postoperative inflammation and flare-ups.
Risk stratification
Complication rates generally decrease with
increasing experience of surgeons 5 . Thus, it is
imperative that cases are allocated appropriately,
especially in teaching hospitals where there is a
vast range of surgeon experience. Preoperative
risk stratification systems have been devised to
assess the risk of complications for individual
patients. They may help minimise complications
by identifying and allocating the higher risk cases
to appropriate surgeons in a standardised manner.
In a recent study in Auckland, two preoperative
risk stratification systems were evaluated – one
system devised by Muhtaseb et al 6 and another
system used in the Buckinghamshire NHS Trust.
Each system takes into account different risk factors
and a final risk score is calculated by adding up the
risk factors in each case (Table 1). Subsequently,
the Muhtaseb system was implemented to assist
allocation of cases to registrars, fellows and
consultants and further analyses are underway to
examine the impact on complication rates.
It is imperative that risk factors are identified and
documented preoperatively for such cataract risk
stratification systems to work effectively. Apart
from allocating cases to appropriately experienced
surgeons, they support surgeons of all levels to
take precautions in order to reduce complications.
It also allows practitioners involved in preoperative
assessments to focus discussions on specific risks
with individual patients, which is critical in providing
the best quality of cataract surgery, and most useful
in postoperative management. ▀
Table 1. Preoperative risk factors as per the Muhtaseb and
Buckinghamshire risk stratification systems for cataract surgery.
RISK FACTORS M-SCORE B-SCORE
Age (years) >88 1
Ametropia (>6 D of
myopia or hyperopia)
Axial length -
Brunescent/white/
dense/total cataract/no
fundus view
1 -
80-90 years 1
90+ years 2
26mm 1
>30mm 2
3 3
Corneal scarring 1 -
Diabetic retinopathy - 1
Fuchs endothelial
dystrophy
- 1
Only eye - 1
Oral alpha-receptor
antagonist
Phacodonesis 3
Pseudoexfoliation 3
-
Doxazosin 1
Tamsulosin
or similar
Posterior capsule plaque 1 -
Posterior polar cataract 1 -
Previous vitrectomy 1 1
Shallow anterior chamber
(