CORNEAL CONUNDRUMS
Mark A. Terry, MD, Director, Corneal Services, Devers Eye Institute, and Scientific Director, Lions Vision
Research Laboratory of Oregon, Portland, OR
| ENDOTHELIAL KERATOPLASTY: CURRENT TECHNIQUES AND FUTURE DIRECTIONS
|
| Penetrating keratoplasty (PK): traditional method of replacing endothelium: short-term results do not guarantee
long-term safety; complications—retained sutures can cause endophthalmitis and total loss of vision; problems with PK
result from sutures on surface of cornea and full-thickness vertical wounds (unstable); solution—if corneal sutures eliminated,
no suture problems; if corneal surface incisions eliminated, no incision problems; consider endothelial keratoplasty
(EK; eg, deep lamellar endothelial keratoplasty [DLEK])
|
| DLEK (overview): split-thickness surgery to selectively replace diseased tissue; also known as posterior lamellar
keratoplasty (PLK); scleral incision; excise back surface of cornea, removing posterior 150 to 200 µm, along with diseased
endothelium; (creates bed for donor tissue); inject air bubble to hold tissue in place
|
| Current experience with ≈500 cases of EK (Terry et al, 2000-2006): EK procedures include DLEK, Descemet’s
stripping endothelial keratoplasty (DSEK), and Descemet’s stripping with automated endothelial keratoplasty
(DSAEK); Institutional Review Board (IRB) study—≈300 cases of DLEK (≈30 DSEK, ≈200 DSAEK)
|
| Longer-term endothelial survival with EK (first 100 cases of DLEK): large incision (9 mm; tissue applied
without folding); small incision (5 mm; includes cases in which tissue unfolded after insertion); endothelial cell loss—
25% cell loss at 6 mo postoperatively (26% at 1 yr, 37% at 2 yr); loss not unexpected (also occurs with PK)
|
| Folding tissue for EK kills endothelial cells: large-incision DLEK—9-mm incision; did not fold tissue; cell loss
22% or 23% at 1 yr (27% at 2 yr); small incision—28% cell loss at 1 yr (43% at 2 yr); comment—fold causes cells to
redistribute over time; studies on EK, including Descemet’s membrane endothelial keratoplasty (DMEK), need 1- and 2-
yr data
|
| Issues with EK (DLEK, DSEK, DSAEK): donor issues—disc dislocation; primary (iatrogenic) graft failure; visual
recovery (interface and residual tissue obstacles to achieving 20/20 vision)
|
| Smoothness of interface (DLEK vs DSEK; Terry et al, 2006): DLEK—in 10 of 10 eye bank eyes, very
smooth surface (fibers evenly cut); DSEK—smooth surface like glass; difference dramatic (better interface on recipient
side); cannot get surface as smooth on donor side of interface (cutting through stromal fibers); smoother surface of
DSEK/DSAEK may explain higher disc dislocation rate (in first 100 cases of DLEK, rate 4%; in first series of DSAEK
and DSEK, rate 50%); smoother surface may yield better optics
|
 | Using current technique: dislocated disc rare; simple procedure using viscoelastic (Healon); donor tissue usually precut;
if not precut, coat endothelium with viscoelastic; use corneal storage medium (Optisol) in Moria microkeratome system
so that nothing touches endothelium except Healon and Optisol; increase pressure after mounting tissue; use 300
µm head; do not want tissue too thin (120-170 µm ideal); make incision ≥9 mm diameter; if smaller, enlarge and extend
to periphery with Devers dissector to avoid problem of thick edges; put corneal cap back in place to protect interface
and to provide tectonic support; scleral incision stronger, safer, and more astigmatically neutral than clear corneal
incision
|
| Case: Healon filling anterior chamber (AC); in 500 cases, speaker has not had Healon in interface or disc dislocation due
to Healon; do not cut into stromal tissue; break through Descemet’s membrane (DM) and use blunt hook to score it;
with Healon filling chamber, tissue easily strips away (easiest part of procedure); sometimes takes only 1 or 2 motions
of reverse Sinskey hook to remove DM; size of circular marker depends on size of eye
|
| Scrape peripheral recipient bed: letting edges attach key to preventing disc dislocation; speaker uses Terry scraper; with maneuver,
dislocation rate reduced to <2%; get ring of scraping all around, leaving 7-mm center clear; remove Healon with
irrigation/aspiration (I/A) tip; dismount tissue, keeping it on post of AC; remove tissue carefully, making sure no damage
to endothelium; irrigate scleral rim (not endothelium) with Optisol; speaker uses Barron donor punch; tissue folded in anterior/posterior
ratio of 60%/40% (more recently using 40%/60% ratio and flipping tissue around to avoid having endothelium
touch plastic; grab tissue with Charles insertion forceps; AC filled with balanced salt solution (BSS); with
deepening of AC, donor tissue usually unfolds nicely
|
| If tissue not in position: deepen AC with irrigation and nudge from stromal side or massage it externally; slowly put in air
bubble; after tissue unfolds, inject air to lock it in place; once AC filled with air, remove interface fluid
|
| Sweeping maneuver described by Price et al: compress surface of eye with sweeper; turn lights out and wait for 10 min; leave
8- or 9-mm air bubble at end of surgery to avoid pupillary block (make sure bubble freely moving); if air bubble covering
only graft and edges, and freely moving, no pupillary block; best uncorrected visual acuity (BUVA) at 5 wk, 20/25 (achievable)
|
| Outcomes with DSAEK (studies by Terry)
|
| Visual results better with DSAEK than DLEK (study): at 6 mo, average visual acuity 20/37 (if eyes with retinal disease
disregarded, average 20/32); 90% 20/40 or better (30% 20/25 or better, 10% 20/20 or better [some 20/15])
|
| Complications: at 6 mo, no significant astigmatism induced; endothelial cell loss—35% with DSAEK (compared to
25% with DLEK; highly significant); following same curve, may have 60% loss at 2 yr; disc dislocation—in first
100 cases, 4 dislocations at 4 days postoperatively; however, no dislocations in AC in 80 most recent cases; rate ≤2%;
primary graft failure—rate 1% (none in 80 most recent cases); includes precut tissue
|
| How to safely transition from PK to EK: read peer-reviewed literature; view videos on EK available on American
Academy of Ophthalmology (AAO) Web site; speaker’s Web site dlek-dsek.com; attend hands-on course in EK surgery
|
| Conclusions about EK: selective replacement of diseased endothelium; provides faster and better visual rehabilitation
than PK; speaker recommends as first-choice therapy for patients with endothelial dysfunction (eg, Fuchs dystrophy);
procedure effective; low complication rate; patients happier
|
| Case presentation (patient SK): 43-yr-old man; referred for evaluation of only eye (right eye); 2 mo ago, herpes simplex
virus (HSV)-associated stromal keratitis with ulceration and secondary streptococcal bacterial keratitis; patient
treated appropriately, but subsequently presented with nonhealing corneal leukoma and epithelial defect; hand-motion vision;
over past 6 wk, received tobramycin and dexamethasone (TobraDex), vancomycin, and oral acyclovir; patient had
necrotic keratitis and chronic epithelial defect; thin vascularized cornea
|
| Evaluation: bacterial and viral cultures negative; B-scan of posterior pole normal; lateral tarsorrhaphy performed; steroids
decreased to twice-daily; punctal occlusion of lower eyelid; antibiotics discontinued; preservative-free ocular lubricant
(HypoTears ointment) used q1h; patient seen again at 1, 2, and 4 wk; slight epithelial healing to edge of lipoidal
degenerative area in first week (no movement over 3-4 wk); no dendrites or increase in inflammation; leukoma area with
early sterile melt at fourth week (eye moving quickly toward bad result); patient homeless (lives on street), with poor
compliance and hygiene; “disaster case”; in speaker’s view, only viable solution deep anterior lamellar keratoplasty
(DALK; total removal of cornea except for DM)
|
| Essential steps of DALK (Anwar and Shimmura): trephine to 75% depth at deepest portion of cornea; separate
DM from recipient cornea using injection of air or BSS; enter AC with limbal paracentesis to soften globe; remove anterior
75% of stroma; inject Healon into pocket to maintain space; move residual stromal tissue, creating 8-mm “iatrogenic
descemetocele”; suture in full-thickness donor button; adjust suture compression for astigmatism; PK not indicated (with
thin rim, surgeon would have to go to limbus; patient would have severe problems)
|
| Advantages of DALK over PK: safer procedure (not “open sky” [eye not open except for paracentesis site]); retained
recipient endothelium (no late endothelial cell loss; with PK, cells lost over life of graft); with DALK, some endothelial cell
loss at time of surgery, but at 1 to 5 yr (and further), no significant cell loss; no rejection issues with DALK; patients taken
off steroids in ≈6 wk (rather than years; avoids complications of long-term steroid use); sutures usually removed at ≈3 mo
after surgery; sutures can be removed within weeks (adjust astigmatism as needed); less risk for future rupture (DM intact);
procedure especially efficacious if surgeon worried about risk for mechanical or immunologic trauma postoperatively
|
| Disadvantages of DALK, compared to PK: smaller percentage of eyes attain 20/20 best corrected visual acuity
(BCVA) with DALK; however, equal percentage of eyes with 20/25 vision; DALK technically more demanding and
takes more time
|
| Anwar’s “big bubble” technique for macular dystrophy (case): patient with stromal dystrophy; trephinate to
≈70% depth; use 27- or 30-gauge needle to bevel into deep stroma (inject air); maintain paracentesis site; remove top part
of cornea; speaker injects Healon to maintain bubble (Anwar does not); DM on top of iris, completely detached; if detachment
past trephination, can excise with scissors, always softening globe to keep Healon pushing DM on iris; strip off
DM (use Weck cell or forceps); place tissue on top of DM; remove Healon (wash with BSS); speaker uses interrupted sutures
(tighter than with single continuous strength; adjust for astigmatism to get early visual rehabilitation in first few
weeks after surgery)
|
| DALK for complicated keratoplasty (patient SK revisited): speaker used Shimmura’s technique of using BSS
to detach DM; hand-held trephine used to cut down on thick portion of cornea; DM detached onto iris; during final excision
of patient’s stroma from DM, microperforation occurred at 5-o’clock position, peripheral edge of bed; management
of perforation—place air bubble in AC; eye rotated to get air bubble to cover perforated area (provides enough seal to
put donor tissue on); donor cornea sutured into position; air bubble now left in and patient’s head positioned so that air
bubble now at 5-o’clock position to cover perforation site; tarsorrhaphy redone; 1 wk after replacement of stromal
tissue—epithelial healing on surface “not pretty,” but eye safe; at 3 yr—few residual sutures; vision 20/50; vessels on
DM, some stroma and some irregular astigmatism; patient steroid-free; 6 mo later, phacoemulsification performed and
intraocular lens implanted; patient employed and “has a life”
|
| Conclusions: DALK surgery offers greater postoperative safety, faster visual rehabilitation, and freedom from long-term
risk of steroid use, suture retention, endothelial rejection and late endothelial failures seen with PK; in selected cases,
with healthy endothelium, DALK should be considered instead of standard PK (can always perform PK if DALK not
helpful)
|
| TRAUMATIC CATARACTS AND IRIS REPAIR
|
Blunt Trauma
| Case 1: presentation—traumatic mydriasis, white cortical cataract, count-fingers vision; treatment—goals 1) eliminate
white cataract and restore vision, and 2) reduce size of pupil; speaker does not use dilating drops at time of surgery (need
to see change in pupil size); administer trypan blue (VisionBlue); if zonular dialysis present, use intracapsular ring (possibly,
Cionni capsular tension ring if need to attach to ciliary sulcus); treat cataract first, then evaluate iris; administer
acetylcholine (Miochol-E) to reduce pupil size (however, pharmacologic therapy usually insufficient); fill chamber with
viscoelastic (Healon) and put in Sinskey hook; test rigidity of iris (if lax, iris repaired more easily); sometimes, simple
McCannel suture sufficient to bring superior iris together; in this case, upper eyelid will cover area where pupil not perfectly
round; if single suture not curative, more suturing needed (inferiorly, 1-4 McCannel sutures needed to close pupil
enough to prevent glare)
|
| Case 2: white cataract from punch in eye, iris dialysis, zonular dehiscence (iris dialysis almost assures that no zonules
present); use intracapsular ring to stabilize capsule
|
| Case 3: presentation—iris dialysis; cataract, 180° of zonular dehiscence; simple McCannel suture would not be curative;
sewing needle technique for closed repair of iris dialysis—first create scleral flap (take down conjunctiva to
bare sclera); engage iris edge with empty 30-gauge needle and insert 10-0 prolene into needle tip; exit under small
scleral flap; reengage iris with needle, carrying suture into AC and out; remove suture from needle; withdraw needle
without suture back into AC; reengage iris edge with needle; exit needle through sclera; reinsert suture into needle tip;
withdraw needle into AC with suture; reengage original iris edge and exit through original scleral flap bed; pull suture
end from needle and tie; close scleral flap over knot; elegant technique of completely closed AC
|
| Case 4: presentation—carpenter hit self in eye with hammer; iris dialysis, traumatic cataract, zonular dehiscence;
management—try to repair iris first (flopping around AC; if trying to do phacoemulsification first, obscures view); repair
with sewing needle technique; (treat cataract second); postoperatively, pupil not perfectly round, but looks fine and
patient happy with appearance; once healed, repair invisible under sclera
|
Chemical Trauma
| Case 5: presentation—lye burns to both eyes; corneal edema, peripheral anterior synechiae (PAS); anterior segment
reconstruction with iris repair—patient not candidate for EK (needs PK); after trephination, try to salvage as much
iris as possible; vitrectomy indicated; PAS present; perform lens removal and scar excision through open sky; dissect
PAS with sponge tips; once iris down, strip off fibrous membranes; intraocular cautery may be indicated to control bleeding;
speaker prefers purse string sutures; angle “shot” (patient will need glaucoma surgery to control intraocular pressure);
pulling iris down and making taut plane, can prevent further PAS formation; keep iris away from graft to prevent
rejection; Pseudomonas keratitis treated successfully; anterior segment reconstruction performed; outcome—clear cornea;
in some areas, iris totally gone (holes in iris due to adherence of PAS); postoperative vision 20/40
|
| Case 6: presentation—HSV infection, secondary bacterial infection, and leukoma scar; much PAS; treatment—anterior
segment reconstruction; purse string sutures not effective (not enough iris for coaptation), so suture placed across pupil (postoperatively,
will not be visible to patient); outcome—vision 20/25
|
| Iris repair in trauma cases (summary): perform full preoperative evaluation of extent of damage (assess PAS, posterior
synechiae, and iris tissue loss); perform intraoperative assessment of iris rigidity; use McCannel sutures (single or
multiple) liberally; perform anterior segment reconstruction with iris sphincter purse string suture or transpupillary sutures;
pupillary sutures may reduce PAS, iridocorneal adhesions and graft rejection
|
Suggested Reading
Melles GR et al: A surgical technique for posterior lamellar keratoplasty. Cornea 17:618, 1998; Melles GR et al:
The future of lamellar keratoplasty. Curr Opin Ophthalmol 10:253, 1999; Ousley PJ, Terry MA: Stability of vision,
topography, and endothelial cell density from 1 year to 2 years after deep lamellar endothelial keratoplasty surgery. Ophthalmology
112:50, 2005; Parker J et al: Videokeratography of keratoconus in monozygotic twins. J Refract Surg
12:180, 1996; Terry MA et al: A prospective study of endothelial cell loss during the 2 years after deep lamellar endothelial
keratoplasty. Ophthalmology 114:631, 2007; Terry MA et al: Deep lamellar endothelial keratoplasty: early complications
and their management. Cornea 25:37, 2006; Terry MA et al: Histology of dislocations in endothelial
keratoplasty (DSEK and DLEK): a laboratory-based surgical solution to dislocation in 100 consecutive DSEK cases. Cornea
25:926, 2006; Terry MA, Ousley PJ: Deep lamellar endothelial keratoplasty in the first United States patients:
early clinical results. Cornea 20:239, 2001; Terry MA, Ousley PJ: Small-incision deep lamellar endothelial keratoplasty
(DLEK): six-month results of the first prospective clinical study. Cornea 24:59, 2005; Terry MA: Endothelial replacement
without surface corneal incisions or sutures: topography of the deep endothelial keratoplasty procedures.
Cornea 20:14, 2001; Terry MA: The evolution of lamellar grafting techniques over twenty-five years. Cornea 19:611;
Waring GO 3rd et al: Results of anterior segment reconstruction for aphakic and pseudophakic corneal edema. Ophthalmology
95:836, 1988.
Educational Objectives
| The goal of this program is to improve the surgical management of patients with corneal disease. After hearing and assimilating
this program, the clinician will be better able to:
|
| 1. Identify potential complications of penetrating keratoplasty (PK).
|
| 2. Describe advantages and disadvantages of endothelial keratoplasty (EK) compared to PK.
|
| 3. Choose appropriate therapy for endothelial dysfunction due to, eg, Fuchs dystrophy.
|
| 4. Recognize indications for deep anterior lamellar keratoplasty (DALK).
|
| 5. Describe new methods for managing cataracts and for iris dialysis due to trauma.
|
Faculty Disclosure
In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty members to disclose relevant
financial relationships within the past 12 months that might create any personal conflicts of interest. Any identified
conflicts were resolved to ensure that this educational activity promotes quality in health care and not a proprietary business
or commercial interest. For this program, the following has been disclosed: Dr. Terry has received royalties from Bausch
and Lomb Surgical for instruments he has designed.
Acknowledgments
Dr. Terry was recorded at Controversies in Ophthalmology, presented January 13, 2007, in Los Angeles, CA, by the Research
Study Club of Los Angeles, and at the 30th Annual UC Davis Ophthalmology Symposium, Cornea: The Cutting
Edge, presented May 18-20, 2007, in Napa, CA, by the UC Davis Health System, the Office of Continuing Medical Education,
and Department of Ophthalmology and Vision Science. The Audio-Digest Foundation thanks Dr. Terry and the sponsors
for their cooperation in the production of this program.
|
