1. Femtosecond Laser-assisted Bowman Layer Transplantation (BLT)
Purpose:
Halt progression of KC
Improve CLs tolerance
Achieve corneal flattening which may improve BCVA with spectacles as well as
CLs
Delay keratoplasty.
30% failure rate with manual BL graft prepartion hence prepare graft with
Femtosecond Laser (FSL).
Inclusion Criteria:
Grade 3 and 4 KC (Mean K atleast 58D and K max atleast 68-70D)
Documented Progression (≥ 1D change in simulated keratometry (SimK) values,
≥ 1D change in maximum keratometry (Kmax)– Debatable for our study /
Consider taking stable KC patients as well?
CCT > 250 microns but < 400 microns (consider CXL if CCT>400 microns)
Intolerant to RGP / Unsuitable for ISCRS
Acceptable vision with CLs – The patient determines the “acceptable vision”
Preferably clear central cornea
Quiet eyes / Treat VKC first.
No age/gender limitation
Pre and Post-procedure Investigations:
Examine / investigate both eyes.
Need to know KC grading of every case (Pre-op: BLT has been performed in
patients with a K max and Mean K of 77.2D and 64D respectively as well)
UCVA
BSCVA (best spectacle corrected visual acuity)
BCCLVA (best corrected contact lens visual acuity)
Coloured photograph of the anterior segment, especially cornea.
AS-OCT of cornea.
2. Specular microscopy (document all parameters)
G4 Scans (CCT, Thinnest corneal thickness, K-max, Anterior K values, Post K
values, aberrations profile, densitometry for light scatter)
IVCM (Only 1 case report published for a patient who had a BLT – the findings
can become another research paper)
Document any event like progression, development of haze, acute hydrops, BL
graft abnormalities etc.
POD1: Coloured photograph of the anterior segment, especially cornea.
AS-OCT of cornea.
Subsequent Visits: All the above-mentioned investigations to be repeated at 1 week, and
then every month for 1 year.
Post-op Regime: Standard topical antibiotic/steroid regime with a tapering schedule.
Counsel patients to avoid eye rubbing and treat ocular allergies aggressively.
Important Surgical Points:
BL is 8 to 12 microns.
Record all intraoperative and postoperative complications.
Donor Preparation: Mount globes in custom eye holders and remove the
epithelium. Trypan blue is then dripped over the corneas and then rinsed away
with saline. The Ziemer Z8 LDV FSL is then docked to achieve suction against the
corneoscleral limbus of each eye. After selecting the anterior lamellar
keratoplasty program, the maximum diameter cut size is chosen (10.0 mm) and
the depth of laser application is set to 20 μm. Automated cutting is then done
and, when complete, each graft is freed from the underlying stroma by the
delicate action of McPherson forceps. Once separated, each graft can
spontaneously curled into a roll, with the epithelial surface on the outside, owing
to the inherent elastic properties of the BL itself.
Melles showed that the thickness of the BL grafts prepared by FSL measured
37.1 (±8.6) μm.
3. Once the BL has been harvested, we place it in a 70% isopropyl alcohol solution
for 30 seconds to remove the remaining living cells. Finally, the BL is rinsed in a
saline solution.
Host Pocket: Use intrastromal pocket module with FSL and prepare a 9mm
pocket. Keep the diameter of the side incision at 5mm.
For inlay grafts, prepare stromal pocket in midstroma (50% of thinnest
pachymetry)
We would need fibrin glue, smile spatula and a surgical glide for FSL-assisted
BLT.
