EVALUATION OF DEEP ANTERIOR LAMELLAR KERATOPLASTY VERSUS INTRACORNEAL RING SEGMENTS IN TREATING MODERATE KERATOCONUS

Abstract

Background: Keratoconus can cause gradual distortion of vision due to
progressive myopia and irregular astigmatism. keratoconus is classified into four
stages. The treatment is stage specific starting from glasses or hard contact lenses
in the very early stages passing to intra corneal ring segments(ICRS) with or
without collagen cross linking(CXL) in the second stage then deep anterior
lamellar keratoplasty (DALK) or intra corneal ring segments in the third stage
ending with penetrating keratoplasty in the fourth stage.
Patients and Methods: This study included 50 Patients from attendants to
outpatient clinic Ophthalmology Department, Zagazig University. Those patients
were diagnosed as moderate keratoconus according to modified Amsler
classification. The patients were divided randomly into 2 equal groups each one
involved 25 eyes. The patients of the first group had DALK using the double
bubble modification of the Big Bubble (BB) technique while patients of second
group had femto assisted intrastromal corneal ring segment (KERA) implantation.
The patients were followed up for 12 months. This prospective randomized
interventional study aimed to evaluate and compare intracorneal ring segments
(ICRS) versus deep anterior lamellar keratoplasty (DALK) in treating moderate
keratoconus. A complete ophthalmic examination was performed, including visual
acuity, refraction, and keratometric readings.
Results: The primary outcome measure in this study was the best corrected visual
acuity (BCVA) at the end of follow up period which is 12 months while the
secondary outcome measures were the uncorrected visual acuity (UCVA), mean
spherical and mean K value. In the first group (DALK group) the mean UCVA
preoperatively was 0.05 ± 0.001 and mean BCVA preoperatively was 0.08 ±
0.001while postoperatively the mean UCVA was 0.1 ± 0.02 and mean BCVA
postoperatively in the 3rd month was 0.25 ± 0.02 and in the 6th month visit was
0.5 ± 0.02. In the second group (ICRS group), the mean preoperative uncorrected
visual acuity (Pre UCVA) was 0.06± 0.001 while mean preoperative best
corrected visual acuity (Pre BCVA) was 0.08± 0.001. The mean postoperative
uncorrected visual acuity (post UCVA) was 0.21 ± 0.02 while the mean
postoperative best-corrected visual acuity (post BCVA) was 0.4 ± 0.01. All
patients of both group had progressive visual improvement in their BCVA
compared to the preoperative one. In both groups also, the spherical equivalent,
spectacle astigmatism and mean central K value showed significant improvement
postoperative compared to preoperative.
Conclusion: Both femtoassisted intracorneal ring segments and deep anterior
lamellar keratoplasty are safe and effective surgical alternatives in treating
patients with moderate keratoconus. Both of them lead to progressive
improvement in the visual outcome of keratoconus patients. Achieving the
deepest possible interface to reduce scarring, achieve a posterior layer of uniform
thickness, perform smooth surface sectioning of both the graft and bed, make the
graft tissue of appropriate thickness, obtain the highest quality donor material,
insure good coaptation of the edges and uniform traction of the sutures, and make
sure there is perfect cleanliness of the interface are the factors of obtaining best
visual results after DALK procedure.
Key notes: moderate keratoconus, deep anterior lamellar keratoplasty,
intracorneal ring segment.