KERATOCONUS SURGERY
From Corneal Transplantation in the 21st Century, presented October 9, 2004, by the San Diego Eye Bank
Yaron S. Rabinowitz, MD, Clinical Professor of Ophthalmology, David Geffen School of Medicine at the University
of California, Los Angeles, and Director of Ophthalmology Research, Cedars-Sinai Medical Center, Los Angeles
| SURGICAL TREATMENT OF KERATOCONUS
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| Indications for corneal transplantation surgery: contact lens intolerance; best corrected visual acuity (BCVA)
<20/50; either contact lens intolerance or BCVA <20/50 and will not consider intrastromal corneal ring segments (Intacs)
or not candidate for Intacs; central corneal scarring
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| Contraindications for Intacs: unrealistic expectations; cornea thinner than 450 µm at 7-mm optical zone; central corneal
scarring; maximum keratometry (K) reading 57 diopters (D)
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| Corneal transplantation: advantages—most successful organ transplantation procedure; in keratoconus, success rate
96% to 98%; excellent option for patients who are contact lens intolerant, have central scarring, or want to be rid of contacts
permanently; most patients still require glasses or contacts, but quality of vision much improved; disadvantages—long visual
recovery (can take 3 mo to 1 yr); frequent use of drops; multiple visits to see physician; chance of rejection, infection,
Urrets-Zavalia syndrome (permanently dilated pupil), and postoperative myopia and astigmatism; possible loss of eye due to
expulsive hemorrhage or endophthalmitis; clinical experience—speaker performs 50 to 60 grafts per year for keratoconus;
100% of patients achieve BCVA 20/30 or better; 75% achieve BCVA 20/20; in last 60 patients, 1 rejection episode reversed
with drops, 1 suture infection, and 3 regrafts; 35% of patients totally independent of contact lenses after refractive surgery
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| Epikeratoplasty: not widely used; few cases meet indications; in majority of cases, BCVA between 20/25 and 20/40;
surface interface main problem; indicated for patients with Down’s syndrome and others unable to take care of graft
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| Limbus-to-limbus tectonic keratoplasty: indicated for patients with keratoglobus; challenging to perform
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| Deep lamellar keratoplasty: technically difficult; involves splitting cornea at level of Descemet’s membrane, followed
by hydrodissection; risk for perforation; speaker believes technique needs perfecting
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| Penetrating keratoplasty (PKP)
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 | Preoperative preparations: lid hygiene; topical nonsteroidal anti-inflammatory drug (NSAID) and antibiotic for 3 days
preoperatively; speaker likes eye to be soft and uses pilocarpine 1%; speaker prefers general anesthetic; topography determines
presence of central or oval cone
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| Intra- and postoperative procedures: speaker uses Barron-Hessburg trephine system, and 12 interrupted 10-0 nylon sutures;
sutures selectively removed at 3 mo, with all sutures removed by 6 mo; speaker does not use dilation because of potential
for postoperative Urrets-Zavalia syndrome; patients placed on steroids immediately after operation, beginning with every
hour, then every 2 hr, and tapering to qid
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| Potential complications: steroid-induced glaucoma and cataract; graft rejection; graft failure; wound dehiscence (avoided if
care taken with graft; more likely to affect older patients); high astigmatism; anisometropia
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| Transplantation technique: typically, speaker transplants 7.5-mm donor button into 7.5-mm host; others use 8-mm or
8.25-mm buttons; study shows higher incidence of rejection with buttons ≥8 mm; acceptable to wear contact lenses;
leave patients with with-the-rule astigmatism to allow better contact lens fit; after removal of stitches, most patients
elect to have refractive surgery
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| Residual myopic astigmatism: most patients left with residual myopic astigmatism; most patients with keratoconus tend to be
myopic (measure axial length before deciding whether to transplant same-size button; short axial length may require bigger
button to avoid hyperopia); laser in situ keratomileusis (LASIK) in patients with residual myopic astigmatism—
done in 2 stages; first, correct astigmatism >4 D with astigmatic keratotomy (AK) and interrupted sutures; remove sutures
after 6 wk; after further 6 wk, cut flap; wait another 6 wk, then treat with combination of mixed myopic cylinder and
smoothing technique; patients likely to regress, and touch-up required after 6 mo; case example—25-yr-old man with
central corneal scarring and advanced keratoconus; after removal of sutures, patient had 18 D of cylinder; speaker placed
cuts in steep area and put sutures in opposite meridian; after removal of sutures, patient had 3 D of cylinder; LASIK then
performed, resulting in uncorrected visual acuity (UCVA) 20/25
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| Post-LASIK ectasia: behaves like keratoconus; occurs because of missed early keratoconus suspect, missed early pellucid
marginal degeneration, or stromal bed <250 µm
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| Pellucid marginal degeneration: keratoconus variant; transplantation problematic because being too close to limbus
can result in rejection; topography characterized by “crab-claw” appearance; speaker developed technique where crescentic
lamellar transplant followed by central penetrating corneal transplant, which makes tissue thicker so penetrating transplant
not so close to limbus
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| Hydrops: do not perform grafts on patients with hydrops; wait until hydrops resolves and scar clears (vision often improves)
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Gene Expression Studies of Keratoconus Corneas
| Corneal gene library: important to remove cornea immediately after PKP to preserve messenger RNA; using 7 keratoconus
buttons, first corneal gene library established (available at http://neibank.nei.nih.gov), containing information on
name, function, and location of 4109 corneal genes
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| Pathogenesis of keratoconus: apoptosis (programmed cell death)—attributed as potential cause; 365 apoptosis
genes identified in keratoconus corneas; KC-6 gene—novel gene identified in cornea; thought to be cornea-specific stem cell
gene; possible that keratoconus preprogrammed; decreased expression of KC-6 in keratoconus; aquaporins—water-channel
proteins; 3 aquaporins in cornea (aquaporin 5 [AQP5] in epithelium, aquaporins 1 and 3 in endothelium); AQP5 absent in
keratoconus; potential defect in water transport into cornea from epithelium, causing cornea to thin; may be marker for keratoconus
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| NONKERATOPLASTY SURGERY IN KERATOCONUS
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| Post-LASIK ectasia: most dreaded complication after LASIK; can be progressive, resulting in loss of BCVA; high
chance for litigation
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| Prevention of ectasia: preoperative screening to rule out subtle topographic abnormalities, specifically, early keratoconus,
keratoconus suspect, and early pellucid marginal degeneration; preoperative and intraoperative pachymetry to ensure
residual host bed ≥250 µm
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| Variations in normal topography: study—10 different classifiable shapes in normal topography (namely, normal
round eye, normal oval eye, normal irregular eye, normal eye with inferior steepening, normal eye with superior steepening,
symmetric bow-tie pattern, symmetric bow-tie pattern with superior steepening, symmetric bow-tie pattern with inferior
steepening, symmetric bow-tie pattern with slightly skewed radial axis, and asymmetric bow-tie pattern with skewed
radial axis above and below horizontal meridian); asymmetric bow-tie pattern with skewed radial axis occurs rarely in normal
eyes (1 in 200) but commonly in keratoconus eyes; majority of normal patients have symmetric patterns, within eyes
and between eyes
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| Detecting early keratoconus and keratoconus suspect: rule out contact lens warpage; look for asymmetric bow-
tie pattern with skewed radial axis; if in doubt, perform dilated cycloplegic retinoscopy (scissoring indicates abnormality);
speaker follows patients for 6 wk to 8 wk with topography and ensures stability 2 wk apart (can take 1 yr to stabilize
from rigid contact lens wear); soft contact lens warpage rare, but has been recorded
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| Indices: KISA% index combines K value (central steepening), inferior-superior (I-S) value, and skewed radial axis (SRAX)
value; I-S value—average of 5 superior data points subtracted from average of 5 inferior data points; should be close to zero
for normal eyes; SD -1.2 to 1.2; KISA% index—published in Journal of Cataract and Refractive Surgery; <100% indicates
normal; >100% indicates keratoconus; 60% to 100% indicates keratoconus suspect; in series of patients, KISA% index increased
in step with 5-yr progression of normal eye to keratoconus
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| Pachymetry: preoperative pachymetry can detect thin corneas not suitable for LASIK; differential pachymetry can confirm
presence of pellucid marginal degeneration (cornea should be thicker closer to periphery; thinning cornea indicates pellucid
marginal degeneration); large variation in ultimate flap thickness vs. intended flap thickness with almost all microkeratomes;
study—compared Moria CB to Hansatome; SD shown to be significant; for Moria CB, minimum thickness 100 µm and maximum
203 µm; for Hansatome, minimum 69 µm, maximum 207 µm; important to do intraoperative pachymetry on all patients
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| Algorithm to prevent ectasia: careful slit lamp evaluation; videokeratography; if pattern indicates keratoconus suspect,
do dilated retinoscopy; if normal, consider contact lens warpage; do preoperative and intraoperative pachymetry; always
do intraoperative pachymetry on enhancements
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| Excimer laser treatment: mostly contraindicated; phototherapeutic keratectomy (PTK) acceptable for removal of
scars and nebulae; LASIK definitely contraindicated
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| Photorefractive keratoplasty (PRK): may be option before consideration of corneal transplantation; contraindicated
in patients <40 yr of age because of disease progression, does not address irregular astigmatism, increased risk of
scarring, and increased risk of thinning of cornea, possibly resulting in perforation; may have role in patients >40 yr of
age who are contact lens intolerant because disease does not progress after 40 yr of age; PRK can give similar results to
glasses; if it fails, transplantation performed
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| Prospective study: PRK performed on 13 eyes of patients diagnosed with early keratoconus or keratoconus suspect referred
for corneal transplantation; patients contact lens intolerant; selection criteria—no evidence of disease progression,
pachymetry ≥400 µm, no central scarring, and realistic expectations; technique—PRK with smoothing technique
(PRK-Sm) used; smoothing addresses irregular astigmatism; initial treatment—no touch with LADAR small spot;
second treatment—broad-beam VISX using 20% hyaluronic acid (Healon) as smoothing solution; results—for 6
eyes with early keratoconus at 9- to 36-mo follow-up, UCVA 20/25 to 20/50; no patients required corneal transplant at
5-yr follow-up; for 7 eyes with keratoconus suspect at 12- to 54-mo follow-up, results varied from 20/15 to 20/20
UCVA; no scarring or progression; results similar to normals; conclusion—in carefully selected patients >40 yr of
age, PRK-Sm might be good alternative to corneal transplantation in patients who are contact lens intolerant
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Intacs for Keratoconus with IntraLase
| Goals of Intacs for keratoconus: primary goal—make patient contact lens tolerant, thus preventing need for corneal
transplantation; secondary goal—may allow for transition from rigid to soft toric lenses; may allow for improved
acuity with spectacles only; realistic expectations—still will be dependent on visual aids; no evidence Intacs retards
disease progression; may not have benefit and may make vision worse
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| Intacs using mechanical technique: study—Intacs performed on 10 eyes; UCVA improved 3 lines (range 0 to 7);
BCVA improved 2.4 lines (range -2ע); spherical equivalent reduced 3.0 D (range 0.50-5.75 D); astigmatism reduced
1.43 D; surface regularity index (SRI) and minimum K reduced
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| Intacs using IntraLase (study): technique—goal to insert Intacs to bisect thinnest area of cornea; avoid superior incision
to prevent neovascularization; thickness of Intacs chosen based on spherical equivalent and desired effect; all entry
wounds sutured with 10.0 nylon; parameters—maximum depth with IntraLase 400 µm; length of cut 1.4 mm, width 1
mm; in United States, only 0.25-mm to 0.35-mm Intacs segments approved (in Europe, segments up to 0.45 mm approved);
asymmetric Intacs segments used in oval cones, 0.3 mm above and 0.35 mm below; symmetric segments used in
nipple cones; single segment sometimes used for mild cones; results—6-mo follow-up available for 6 eyes, 3-mo follow-up
available for 14 eyes; average K reduced 2.2 D (range 0.5-4.6 D); spherical equivalent reduced 3.56 D (range 1.5-
7.0 D); UCVA improved 3.42 lines (range 1 to 7); BCVA improved 3.35 lines (range 0-7); SRI and surface asymmetry index
(SAI) improved; ring size vs. effect—with 1-mm width channels, effect size 0.73 D; with 0.5-mm width channels,
effect size 0.83 D; with 0.4-mm width channels, effect size 2.94 D; conclusion—nomogram requires refinement; the
tighter the channels, the more effect achieved
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| IntraLase vs mechanical technique: Colin study—results for mechanical technique improved over time (results at
1 yr better than at 3 mo); Rabinowitz study—average K, spherical equivalent, UCVA, and BCVA better with IntraLase;
Colin study vs Rabinowitz study—greater reduction in average K achieved with Colin’s mechanical technique; UCVA
and BCVA better with IntraLase, despite using smaller (0.35 mm) segments; Rabinowitz study vs Siganos study—
average K, spherical equivalent, UCVA, and BCVA better with IntraLase in Rabinowitz study, and patients more advanced,
despite using smaller (0.35 mm) segments; overall—mechanical techniques achieve slightly more flattening,
but spherical equivalent, UCVA, and BCVA better with IntraLase; contact lens and glasses tolerance—at 6 mo, 100%
of IntraLase patients had BCVA 20/20 to 20/40; only 70% of mechanical procedures successful (2 eyes required transplant,
1 required explant); at 3 mo, 53% of IntraLase patients contact lens tolerant and no explants required; advantages
of IntraLase—at 3 to 6 mo, UCVA and BCVA better than any documented mechanical procedure; can guarantee depth
of placement; high patient satisfaction rate at 6 mo (100% of patients happy with vision achieved with glasses or contact
lenses); quicker procedure; fewer epithelial defects; less pain; quicker recovery; can recut channels at different depth; patient
more likely to prefer laser; potential for intralamellar astigmatic manipulation
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| Conclusion: Intacs using IntraLase quick and simple procedure effective for patients with keratoconus; improves contact
lens tolerance, UCVA, and BCVA
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Educational Objectives
| The goal of this program is to educate the listener about keratoconus surgery. After hearing and assimilating this program,
the clinician will be better able to:
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| 1. Describe the surgical treatment options for keratoconus.
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| 2. Use penetrating keratoplasty for treatment of keratoconus.
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| 3. Discuss the genetics and pathogenesis of keratoconus.
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| 4. Prevent post-laser in situ keratomileusis (LASIK) ectasia.
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| 5. Discuss the evidence supporting the use of IntraLase with intrastromal corneal ring segments (Intacs).
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Discussed on This Program
Pilocarpine Ocular Therapeutic System [Ocusert Pilo-20, Ocusert Pilo-40]
Suggested Reading
Amoils SP et al: Iatrogenic keratectasia after laser in situ keratomileusis for less than -4.0 to -7.0 diopters of myopia. J
Cataract Refract Surg 26(7):967, 2000; Boxer Wachler BS et al: Intacs for keratoconus. Ophthalmology
110(5):1031, 2003; Buratto L et al: Excimer laser lamellar keratoplasty of augmented thickness for keratoconus. J Refract
Surg 14(5):517, 1998; Colin J et al: INTACS inserts for treating keratoconus: one-year results. Ophthalmology
108(8):1409, 2001; Colin J et al: Correcting keratoconus with intracorneal rings. J Cataract Refract Surg 26(8):1117,
2000; Colin J, Velou S: Implantation of Intacs and a refractive intraocular lens to correct keratoconus. J Cataract Refract
Surg 29(4):832, 2003; Fernandez-Velazquez FJ: Management of a post-ELLKAT keratectasia with a gas permeable
contact lens. Clin Exp Optom 88(3):181, 2005; Funnell CL et al: Comparative cohort study of the outcomes of deep
lamellar keratoplasty and penetrating keratoplasty for keratoconus. Eye May 6; Epub ahead of print, 2005; Hellstedt T et
al: Treating keratoconus with intacs corneal ring segments. J Refract Surg 21(3):236, 2005; Kim WJ et al: Keratocyte
apoptosis associated with keratoconus. Exp Eye Res 69(5):475, 1999; Kymionis GD et al: Intacs for early pellucid marginal
degeneration. J Cataract Refract Surg 30(1):230, 2004; Kymionis GD et al: Management of post-LASIK corneal
ectasia with Intacs inserts: one-year results. Arch Ophthalmol 121(3):322, 2003; McDonald MB et al: Laser in situ
keratomileusis for myopia up to -11 diopters with up to -5 diopters of astigmatism with the summit autonomous LADARVision
excimer laser system. Ophthalmology 108(2):309, 2001; Rabinowitz YS: The genetics of keratoconus. Ophthalmol
Clin North Am 16(4):607, 2003; Rabinowitz YS, Rasheed K: KISA% index: a quantitative videokeratography algorithm
embodying minimal topographic criteria for diagnosing keratoconus. J Cataract Refract Surg 25(10):1327, 1999;
Rabinowitz YS et al: Gene expression profile studies of human keratoconus cornea for NEIBank: a novel cornea-expressed
gene and the absence of transcripts for aquaporin 5. Invest Ophthalmol Vis Sci 46(4):1239, 2005; Sakai R et al:
Construction of human corneal endothelial cDNA library and identification of novel active genes. Invest Ophthalmol Vis Sci
43(6):1749, 2002; Siganos CS et al: Management of keratoconus with Intacs. Am J Ophthalmol 135(1):64, 2003;
Wang Y et al: Genetic epidemiological study of keratoconus: evidence for major gene determination. Am J Med Genet
93(5):403, 2000; Watson SL et al: Comparison of deep lamellar keratoplasty and penetrating keratoplasty in patients with
keratoconus. Ophthalmology 111(9):1676, 2004; Shimmura S et al: Deep lamellar keratoplasty (DLKP) in keratoconus
patients using viscoadaptive viscoelastics. Cornea 24(2):178, 2005.
Faculty Disclosure
In adherence to ACCME guidelines, the Audio-Digest Foundation requests all lecturers to disclose any significant financial relationship
with the manufacturer or provider of any commercial product or service discussed. For this issue, the faculty reported
nothing to disclose.
Dr. Rabinowitz was recorded at Corneal Transplantation in the 21st Century, presented October 9, 2004, by the San
Diego Eye Bank. The Audio-Digest Foundation thanks Dr. Rabinowitz and the San Diego Eye Bank for their cooperation
in the production of this program.
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