The use of a scoring system can help practitioners predict a potential
LASIK patients risk for developing postoperative ectasia, according to a
presenter at the San Francisco Optometric Continuing Education Symposium.
D. Rex Hamilton, MD, emphasized the importance of accurate screening and
careful patient selection when recommending LASIK and endorsed the use of the
Randleman Risk Score criteria to assess a patients risk for ectasia.
Randleman Risk Score criteria
According to Randleman Risk Score criteria, risk factors for ectasia
include: abnormal topography, thin residual stromal bed, preoperative thin
corneas, high refractive correction and young age. The risk score, although
controversial, Dr. Hamilton said, can be used to assess the patients
overall risk for postoperative ectasia by assigning a score to each potential
risk factor which, when added together, generate a final risk score.
Patients with a cumulative risk score of 0 to 2 are at low risk for
ectasia and can proceed with LASIK, according to this system. Patients with a
cumulative risk score of 3 are at moderate risk for ectasia. Surface ablation,
such as PRK may be considered in these patients. Patients with a risk score of
4 are at high risk, and laser vision correction needs to be approached with
|Figure 1. Waveform (red) generated by the Ocular Response
Analyzer in response to noncontact applanation (green). Corneal hysteresis (CH)
and corneal resistance factor (CRF) are calculated from the graph. Normal CH
and CRF values range from 10 to 12. CH and CRF values in eyes with keratoconus
or forme fruste keratoconus are typically less than 9.
Images: Pacific Vision
|Figure 2. Age vs. hormone and pro-inflammatory mediator levels.
With age, the levels of sex hormones DHEA, testosterone, estradiol and adrenal
androgens decrease. The levels of inflammatory mediators catecholamines,
glucocorticoids and interleukin-6 increase.
Dr. Hamilton pointed out that in this system, topographical
abnormalities of the anterior corneal curvature are the highest risk factor for
ectasia. Such topographic findings, however, can be subtle and their
To help further assess corneal suitability for LASIK, topographic
systems that measure the posterior corneal surface can offer additional
information for detecting early forms of keratoconus (e.g., forme fruste) over
placido-only systems (e.g., anterior cornea measurement only). These systems
provide posterior elevation information and an optical pachymetry map that
shows thickness values across the cornea, specifically the thinnest location.
All of this data results in improved detection of an abnormal cornea.
Dr. Hamilton pointed out that topography, both anterior and posterior,
provides only a static measurement of corneal anatomy. Sometimes the
topographic abnormality is so subtle that it can be difficult to distinguish
between a normal cornea and the cornea at risk for ectasia.
Measure corneal biomechanics
To help improve screening accuracy, Dr. Hamilton recommended including
corneal biomechanics measurement in the preoperative assessment protocol for
patients considering LASIK. Biomechanics is a dynamic measurement that
describes a behavior of a viscoelastic system, such as the cornea, and includes
several parameters. One parameter represents static resistance or elasticity as
with a coil spring and another represents viscous resistance or dampening as
with a shock absorber.
The Ocular Response Analyzer (Reichert Technologies, Buffalo, N.Y.)
measures biomechanics using a noncontact tonometric system. The measurement is
taken by measuring the corneal response to an air pulse delivered by the
instrument. Two parameters, corneal resistance factor (CRF) and corneal
hysteresis (CH), are derived from the waveform. CRF represents the cumulative
effect of both the viscous and elastic resistance encountered by the air jet
while deforming the corneal surface. CH represents viscous damping of the
In a study conducted by Dr. Hamilton comparing CH and CRF values in
normal, forme fruste and keratoconus eyes, he found that eyes with forme fruste
keratoconus have, on average, lower CH and CRF values than normal corneas. In
fact, CH and CRF values in the forme fruste keratoconus eyes are more similar
to those in eyes with frank keratoconus on topography than to topographically
normal eyes. The correlation was independent of patients age, gender and
central corneal thickness.
These results, used together with topography and other risk factors, can
better direct a decision to proceed with LASIK or switch to PRK.
Post-LASIK dry eye
Post-LASIK patients who experience dry eye, regardless of the severity
of their symptoms, should be treated with a four-step approach, Ella G.
Faktorovich, MD, reported.
Practitioners should: listen, not dismiss, diagnose accurately and treat
to cure, she said. Dr. Faktorovich emphasized that regardless of how mild the
findings may seem to the doctor, if the patient perceives their symptoms as
significant, this needs to be acknowledged, and adequate attention needs to be
given to the patient to help him or her through the healing period.
She further described her diagnostic and treatment approach to dry eye
based on the patients age and gender. Rather than simply attribute dry
eye to LASIK, the patients overall health needs be assessed, and careful
medication history needs to be taken to rule out systemic conditions and
medications that may contribute to the symptoms.
Treating women for dry eye
In older women, for example, hormonal changes need to be considered in
diagnosing dry eye. Changes in systemic medications, such as discontinuation of
hormone replacement therapy, may coincide with LASIK and may result in dryness
that may erroneously be attributed to LASIK. Tricyclic antidepressants, such as
desipramine, for example, can cause dryness.
Dr. Faktorovich also recommended a thorough review of systems,
specifically asking about oral and vaginal dryness. Desipramine, for example,
is associated with oral dryness. Sjögrens syndrome needs to be ruled
out in these patients as well. In men and younger women, lid disease frequently
contributes to dryness. Combined with a pursuit of outdoor activities, the
evaporative component can be aggravated. Also, the patients face needs to
be examined for signs of rosacea.
Identifying the specific cause of dryness can help formulate a specific
treatment plan. Rather than simply providing palliative measures with frequent
artificial tears, the plan should aim to cure, Dr. Faktorovich said. She
recommended working with the patients primary care provider to treat
systemic conditions and, if possible, discontinue systemic medications that may
be contributing to the patients symptoms.
Her treatment plan for older women is different than that for men. In
older women, the levels of the sex hormone DHEA decline more significantly than
in men. Declining levels of the hormone result in decreased functioning of many
target organs, including lacrimal and meibomian glands. The levels of
inflammatory mediators, however, increase with age.
The pathogenesis of tear deficiency and evaporative dry eye can,
therefore, be a combination of declining hormone levels and increasing
inflammation in the target organs.
Dr. Faktorovich recommended starting patients on a mild
anti-inflammatory regimen first with FML (fluorometholone 0.1%, Allergan) and
Restasis (cyclosporine A 0.05%, Allergan). If the symptoms persist, a more
potent steroid may be considered, such as dexamethasone 0.1%, for example, as
well as cyclosporine A increased to 1% strength (formulated at Leiters
pharmacy, San Jose, Calif.).
If the symptoms persist or the patient does not tolerate steroid or
cyclosporine, Dr. Faktorovich recommended considering topical hormone therapy
with DHEA, medroxyprogesterone, or progesterone/testosterone, for example.
Treating men for dry eye
In men, Dr. Faktorovich found lid disease to be the primary factor in
pathogenesis of dry eye. She, therefore, recommended treating lid disease first
with a combination of lid scrubs and oral doxycycline or with topical Azasite
(azithromycin 1%, Inspire).
Azasite alone may improve meibomian gland function and result in
increased stability of the tear film due to its antibacterial and
anti-inflammatory action and its excellent penetration of the lid margins,
resulting in a long half-life. by Jennifer Le Coq
- Randleman JB, Woodward M, Lynn MJ, Stulting RD. Risk assessment for
ectasia after corneal refractive surgery. Ophthalmology.
- D. Rex Hamilton, MD, is associate professor of ophthalmology and
director of UCLA Laser Refractive Center, Jules Stein Eye Institute, UCLA
School of Medicine. He can be reached at 100 Stein Plaza, Los Angeles, CA
90095; (310) 825-2737; email@example.com.
- Ella Faktorovich, MD, is founder and director of Pacific Vision
Institute. She can be reached at 1 Daniel Burnham Court, San Francisco, CA
94109; (415) 922-9500; firstname.lastname@example.org;