Aditya Jyot Eye Hospital inaugurated its new LASIK machine- Wavelight Allegretto Wave Eye-Q Laser on 14th January 2015.
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| New LASIK Machine |
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Case:-
A
71-year-old, male came to Aditya Jyot Eye Hospital with complaints
of diminution of vision in both eyes since few years.
His best
corrected visual acuity was Hand movement close to face, >N48 in
the right eye and 6/18, N8 in the left eye.
On anterior
segment examination right eye was showing corneal edema, flat anterior
chamber, silicon oil in anterior chamber, aphakia and left eye was
showing clear cornea, quiet anterior chamber with PCIOL.
On posterior
segment examination right eye showed media grade
2-3, silicon oil filled globe, retina attached, left eye showed
epiretinal memebrane.
UBM done
which showed iris plastered to cornea, aphakia, silicon oil filled globe.
He underwent
right eye AuroKpro on 28 November 2014.
He is doing
well post-operatively.
Introduction:-
The approach of using an
artificial material to replace an opaque cornea was first described by Pellier
de Quengsy, more than 200 years ago. Since that time, several attempts to
develop a modern keratoprosthesis to treat patients with corneal blindness and
a poor prognosis for penetrating keratoplasty have been developed,
with various models using different material, innovative designs and surgical
techniques. Despite progress in conception of keratoprosthesis, the
heterogeneity of results related to different devices and the
serious complications historically described, hampered the acceptance of the
keratoprosthesis as a safe option for surgical treatment.
Currently, considering
modifications made to the designs, and improvements in surgical technique and
postoperative management, the keratoprosthesis emerged as a
viable alternative in patients at high risk for conventional
keratoplasty. One of the most commonly used device is the Boston type I
keratoprosthesis (BKPro), developed initially by Dohlman et al., in 1974 and
approved by the Food and Drug Administration in 1992.
Boston keratoprosthesis devices
The Boston
keratoprosthesis has a collar button design, made of polymethyl methacrylate
(PMMA).
The BKPro has 2
configurations.
·
The type I device, which
is the most frequently used type, consists of a PMMA optical front
plate and stem, which is inserted through a fresh corneal donor graft, locking
into a larger back plate. It is usually recommended for patients with good lid
anatomy and blink to preserve a healthy ocular surface.
·
The type II Boston KPro
has a similar design, with an added 2 mm long anterior cylinder that protrudes
through the lids or between a tarsorraphy. It is reserved for cicatrizing
corneal diseases with poor tear function.
The type I BKPro
dioptric power is polished into its front plate power, and the devices differ
based on the eye phakic status: one design for aphakia and the other
for pseudophakia. The device for aphakia is custom based on the
axial length of the recipient eye. Advances in type I BKPro design have
improved its retention rate. The latest version approved by the Food and Drug
Administration (FDA) for marketing presents 8 holes of 1.3 mm diameter in the
back plate to allow aqueous nutrition for the corneal button sandwiched between
the front and back plate, protecting the tissue from necrosis and melt.
Moreover, the
addition of a titanium locking ring, on the portion of the front plate
protruding from the back plate, helps to prevent latter intraocular unscrewing
of the BKPro complex. Alternatively, the back plate can also be made of
titanium, which seems to cause less postoperative reaction than PMMA. The type
I BKPro is indicated for patients with refractory corneal blindness and poor
prognosis for penetrating keratoplasty. It is usually reserved for patients
with multiple graft failure and those with ocular surface disease in which
conventional corneal transplantation is considered of high risk.
Although the most
favorable BKPro indications are multiple failed corneal grafts, other ocular
conditions have been suitable for BKPro use. Expanding indications include-
·
Cases of ocular trauma,
·
Chemical burns,
·
Herpetic keratitis,
·
Aniridia,
·
Pediatric corneal opacities,
·
autoimmune ocular
disorders, and
·
Severe corneal
vascularization.
The expected outcomes
are influenced by the primary indication, with best results observed
in noncicatrizing conditions, while patients with autoimmune diseases, such as
StevensJohnson syndrome (SJS), usually present a less encouraging prognosis.
Surgical Procedure:-
The technique for implanting
the type I BKPro has been previously described by Dohlman et al. First of
all, a corneal donor button is prepared (8.5 9.0 mm) and a central 3 mm hole
is trephined. For better BKPro centration the 3 mm central trephination can be
performed before the outer diameter punch is used.
The donor button is then
placed over the stem of the front plate, and the back plate is placed on top of
this complex. A titanium locking ring is then snapped into place.
The recipient cornea is
prepared as for traditional penetrating keratoplasty, with a usual host
trephine measuring 0.5 mm less in diameter than the donor graft. The donor
button is then sutured with multiple interrupted 100 nylon stitches.
Postoperative management and complications:-
Postoperative care
includes the use of soft contact lens over the keratoprosthesis in all patients
for an indefinite time, with regular replacement. The addition of a continue
use of a bandage contact lens over the BKPro has been of great benefit for
better hydratation of the exposed tissues, enhancing the device retention and
preven ting complications as dellen formation, epithelial defects and corneal
melt. Postoperatively, all patients need a topical
regimen of steroids with dosage tapering over the first weeks. A maintenance
dose can be adopted according to levels of intraocular inflammation.
An indefinitely
prophylactic antibiotic regimen is recommended for infectious
complications prevention. The recommended prophylaxis routine includes the use
of daily topical fluoroquinolone drops, with a recent addition of topical 1.4%
vancomycin, especially in cases of autoimmune diseases.
The inclusion of topical
vancomycin to the standard prophylactic regimen has dramatically reduced the
incidence of bacterial
endophthalmitis in BKPro eyes. The continued use of bandage contact lenses and
the longterm use of broadspectrum antibiotics and corticosteroids, however,
have the potential of altering the ocular microbiota and predispose fungal
colonization. Considering the low rate of fungal infection, there.
Nowadays, one of the
most common BKPro problems is the de velopment of a retroprosthetic membrane
(RPM), occurring in 2565% of patients within a year after the
device implantation. It can usually be treated with yttriumaluminumgarnet
(YAG) laser membranotomy, with few cases requiring a surgical mebranectomy.
The etiology of RPM is
unknown; authors have reported that the performance of other intraocular
surgery at the time of keratoprosthesis implantation, increased
anterior segment inflammation, diabetes, hypertension, and rate
increase the risk of RPM formation. Results from a Multicenter Study regarding
this issue reported that eyes at the highest risk for retroprosthetic membrane
development are those receiving corneal replacement for infectious keratitis
and aniridia.(y) Stacy et al., characterized retroprosthetic membrane as
a fibrous membrane originated from the host’s corneal stroma by
light microscopy.
This data suggest that
stromal down growth might be the major element of the retro KPro membranes. The
visual recovery and long term outcomes of BKPro patients can also be severely
limited by retina and glaucoma pathologies. Posterior segment abnormalities may
be present prior to BKPro implantation or may occur during or after the
surgical procedure.The related incidence of retinal detachment after BKPro
implantation range from 3.5 to 8% of cases. Modified vitreoretinal
surgical techniques, due to anatomical difficulties frequently encountered
during surgical procedure, can be effectively and safely used to treat
posterior segment complications in these patients.
Glaucoma can severely
compromise visual rehabilitation. The onset and/or progression of glaucoma
remain ongoing challenges in the management of patients with BKPro.
The diagnosis of glaucoma
in these patients is made difficult by the absence of a reliable tool to
measure the intraocular pressure (IOP), with digital finger palpation
being the most used method of estimating the IO. Rigorous perioperative
management of elevated IOP is essential for long- term success of
BKPro surgery. These patients should be followed closely by a
multidisciplinary team, including glaucoma and retina specialists. Regular visual
fields and photo documentation of the optic nerve should be
performed.
Results:
Several studies have
been published to report the outcomes with Boston type I
keratoprosthesis. Results from the first multicenter study, including 136 eyes
with this device, were relevant diffusing this surgical technique,
demonstrating improvements in the retention rate (95% in 8.5 months of followup)
and in the visual prognosis.
The main postoperative
complication observed was RPM formation (25%), followed by an increase of
IOP (15%).
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