Transcript Management of Keratoconus

Prospective Study of Intrastromal
Corneal Ring Segments for
Keratoconus
Scott X. Stevens, MD
Bend Ophthalmology, LLC
Author has no financial interest.
Purpose
Keratoconus is an abnormal thinning of the
central and inferior paracentral cornea and is
a frequent indication for penetrating
keratoplasty. Long-term risks have
prompted intrastromal ring segments as an
alternative. A prospective independent
clinical study was initiated for patients with
keratoconus or post-LASIK ectasia.
Prospective Study of Intrastromal Corneal Ring Segments for Keratoconus
Methods
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FDA HDE guidelines established in 2004 were utilized in this
independent clinical study. The study was initiated February, 2004.
An IRB for the surgeon has been in place. The HDE guidelines
directed that an eye with less than -3D spherical equivalent have a
0.25 ring placed superiorly and a 0.30 ring placed inferiorly. Patient
eyes with more than -3D spherical equivalent have a 0.30 ring
placed superiorly and a 0.35 ring placed inferiorly. The rings are
160o and placed at the 7mm optical zone. All surgeries were
completed by the author. Eyes with central corneal scarring were
excluded from enrollment. Temporal corneal pachymetry was >450
microns. UCVA, BCVA, Keratometry, corneal topography, central
corneal pachymetry were acquired. All eyes had become contact
lens intolerant. Baseline BCVA included piggyback/ gas-permeable
contact lens over-refraction at enrollment. BCVA post-op was
acquired with the patient’s everyday visual aid (ie glasses, contact
lens, manifest refraction). Lasik-ectasia eyes were treated in the
same fashion
as keratoconus eyes.
Prospective Study of Intrastromal Corneal Ring Segments for Keratoconus
Methods

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Fifty-three eyes have been enrolled to date.
5 eyes are no-longer enrolled. Two patients (2 eyes) have
failed to make any follow-up visits. One eye 3-months postop with LASIK-ectasia had the LASIK flap removed by an
ER physician requiring DALK to restore vision (currently
BCVA=20/20). One patient lost his eye secondary to blunt
trauma. The final eye was removed from the study
secondary to eye-rubbing which required removal of the
ring segments as they were exposed for one week.
Visual acuity is the outcome variable. UCVA and BCVA are
presented at Baseline, 6-months, 1-year and 2-year gates.
Statistical comparison was accomplished using a matched
t-test.
Prospective Study of Intrastromal Corneal Ring Segments for Keratoconus
Results
Baseline = 20/260
6-Month = 20/140
t=6.2775, p<0.01
Prospective Study of Intrastromal Corneal Ring Segments for Keratoconus
Results
Prospective Study of Intrastromal Corneal Ring Segments for Keratoconus
Results
Baseline = 20/230
2-Year = 20/120
t=7.2307, p<0.01
Prospective Study of Intrastromal Corneal Ring Segments for Keratoconus
Results
36.1% are 20/20 or better
77.8% are 20/25 or better
83.4% are 20/30 or better
94.5% are 20/40 or better
Prospective Study of Intrastromal Corneal Ring Segments for Keratoconus
Results
71.0% are 20/20 or better
86.8% are 20/25 or better
94.7% are 20/30 or better
100% are 20/40 or better
t=8.6634, p<0.01
Prospective Study of Intrastromal Corneal Ring Segments for Keratoconus
Results
73.7% are 20/20 or better
89.9% are 20/25 or better
100% are 20/30 or better
Prospective Study of Intrastromal Corneal Ring Segments for Keratoconus
Results
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3 eyes lost 1 line of BCVA from Baseline to 6-months. 7
eyes had no improvement.
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1 eye lost 2 lines of BCVA from Baseline to 1-Year. All
remaining eyes improved by at least one line.
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20/30 – 20/40 (n=2)
20/25 – 20/30 (n=1)
20/25-20/40 (n=1)
1 eye lost 1 line of BCVA from Baseline to 2-Year. All
remaining eyes improved by at least one line.

20/25 – 20/30 (n=1)
Prospective Study of Intrastromal Corneal Ring Segments for Keratoconus
Conclusions
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Intrastromal ring segments significantly improve UCVA
and BCVA at every gate (p<0.01)
BCVA improves over time.
At the 2-year gate (n=38), BCVA is 20/30 or better in all
eyes. Seventy-three percent are 20/20 or better.
One eye has needed DALK to repair the damage from
removal of the LASIK flap. The eye was 20/16 BCVA
prior to the event and currently sees 20/20 BCVA.
No eye has needed penetrating keratoplasty to date.
Prospective Study of Intrastromal Corneal Ring Segments for Keratoconus