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Congenital cornea opacity is a rare occurrence which results not only in
blindness but which are associated with numerous related developmental
challenges. Obtaining a specific clinical diagnosis has been difficult and most
cases were attributed to generic categories of Peters Anomaly and Sclerocornea.
Much progress has been made recently in identifying specific genetic defects
which occur during the complex embryonic interactions resulting in the
development of the infant eye. Traditional therapy has involved attempts to
minimize amblyopia, optical iridectomy where feasible, therapy of associated
glaucoma and cornea transplantation. The active infant immune system causing
allograft rejection has been considered an impediment to cornea transplants in
most cases. The small size of the globe contributes to technical surgical
difficulties as well as a variety of post-operative complications.
Significant improvements in the design and implantation techniques of the
keratoprosthesis have occurred over the past decade. The success of the Boston
1 device in treating otherwise inoperable cornea pathology was the stimulus for
one group to begin implantation of these devices in infants afflicted with
congenital cornea opacity. While this team has developed what they feel is a
successful approach the procedure is considered controversial. Two publications
report poor results when employing the traditional approach conducted by a
single cornea surgeon as utilized in adults. They maintain that the technique
should not be undertaken.
The institution advocating the procedure has developed a
multidisciplinary team approach which it feels is essential to success in this
infant population. Cornea, vitreo-retinal, glaucoma and oculo-plastic surgeons
work together in evaluating prospective cases, performing the surgery, and
administering post-operative care. They are supported by a dedicated group of
nurses and technicians and a comprehensive administrative staff. Complications
must be anticipated and aggressively addressed. Not all cases can be successful
but it is possible to achieve long term results and the prospects for
improvements in devices and availability of new drugs are incentives to
continue this important work.
Keywords: Cornea
opacity, Infant, Keratoprosthesis, Ocular embryology
INTRODUCTION
Congenital cornea
opacity in infants and young children pose unique challenges with respect to
both diagnosis and treatment. Blindness which is present during early infancy
has been shown to have wide reaching implications [1-4]. Hearing is the only
distance sense available in these instances. Sound in order to be useful
requires tactile and motor interaction. Blind children require he presence of
sighted individuals to assist them mediate with their environment. Subsequent
sensory, motor, cognitive, social and language development are all adversely
affected in congenital cornea opacity. Thus the provision of vision during
infancy, even it was to be lost due to complications or disease progression, is
an enormous benefit. The prevention of childhood blindness is an important
aspect of the World Health Organization Declaration to eliminate preventable
blindness [4].
The initial recognition of a severe visual problem is most often made
by the mother who becomes aware that normal iris coloration has been replaced
by a white opacity. This is usually followed by a number of medical
examinations involving, neonatologists, ophthalmologists, pediatric
ophthalmologists and ultimately cornea surgeons. In mild or unilateral cases
patching the good eye, creating a larger pupillary opening may be of some
benefit. In cases of cornea opacity in the absence of other developmental
anomalies (dysgenesis) [8] a cornea transplant may be recommended. While this
procedure is associated with a high risk of subsequent graft failure as a
result of the intense immune response present in infants and young children
[9-11] many feel a single transplant should be attempted in these instances. It
is important to realize that even a clear graft will not afford ambulatory
vision if appropriate postoperative rehabilitation is not provided. In addition
the integrity of the macula and the optic nerve must enable transmission of
impulses to a healthy occipital cortex. However functional acuity with the
ability to independently play and eat does not require demonstrated Snellen
related competence. Other anomalies may present additional challenges to visual
function regardless of the success achieved in removing the cornea opacity.
Initial indications for keratoprosthesis were limited to irreversibly
blind adults with bilateral disease considered inoperable for standard cornea
replacement techniques [12-14]. The introduction of the Boston 1 device
dramatically altered the potential for intervention in adults [15-18]. The
Flaum group in consideration of the success of this new device in adults in
combination with the unfavorable prognosis for cornea transplantation in
infants began consideration of keratoprosthesis surgery in this population
[19]. The obstacles were formidable. The inflammatory response, technical
difficulties in dealing with a small eye, dysgenesis, multiple compromised
ocular systems and the ever present danger of amblyopia constitute significant
impediments. The introduction of this technique for infants has been met with
controversy [20,21]. One group of cornea surgeons has reported dismal results
in 11 cases divided between 3 centers. They reported 5 cases with no light
perception and complications including keratitis, endophthalmitis, glaucoma,
device extrusion and retinal detachment. The conclusion was that this procedure
should not be attempted [20].
The Flaum team has utilized a significantly different team approach
rather than a procedure performed by a single cornea surgeon. They maintain
that a multidisciplinary team of cornea, pediatric, glaucoma, vitreo-retinal
and ocular plastic ophthalmic surgeons working with dedicated administrative,
clinical and surgical support staff can achieve reasonable results [19]. While
these focused human and fiscal resources are difficult to achieve in any
institutional setting they are imperative if one is to deal with the many
preoperative, operative and post-operative challenges. While complications do
occur, some can be avoided, but all must be vigorously addressed in a timely
fashion. They advocate lens extraction, parsplana vitrectomy and insertion of
an aqueous shunt at initial surgery. Bandage contact lenses must remain in
place and not infrequently require a partial lateral tarrsoraphy [19].
Communication with caregivers and referring physicians must be maintained so
compliance with post-operative routines are insured, and frequent follow-up is
essential. A thick conjunctiva flap can be fashioned at surgery to reduce
surface melting [22]. Postoperatively prophylactic antibiotics and
anti-inflammatory agents are essential [23]. Topical steroids as well as the
recently available TNF alpha inhibitors are routine [24]. It is important to
keep the bandage lens well hydrated and often moist chamber goggles are
prescribed. Follow-up of one month, three months and after the first year every
six months must be maintained.
Complications encountered include surface melting and retro prosthetic
membrane [25,26]. Intraocular pressure must be monitored to avoid glaucoma;
ultrasound examinations can detect retinal detachment which is an ever present
danger. Thinning of donor tissue and retraction of the conjunctiva must be
addressed with surgical repair as soon as they are noticed. Endophthalmitis in
infants is related to noncompliance with antibiotic regimes [27]. The necessity
of compounding antibiotics is a burden for care givers. To address this Flaum
and others have reduced the dependence on compounded vancomycin and substituted
Polytrim (trimethoprim/bacitracin available in commercial pharmacies).
Not all are candidates for this surgery. Micophthalmic eyes, Stevens
Johnson and herpes simplex should not be attempted. Parents must be prepared
for management over a long term so an informed consent understanding is an
essential prerequisite. Arrangements must be made in advance for local
ophthalmologists to monitor progress and communicate with the surgical team. A
dedicated nurse coordinator is essential in maintaining communications with
all.
In the final analysis functional acuity is an enormous benefit to
future development and the capacity to provide this opportunity exists today
and will undoubtedly improve in the future with the development of improved
diagnostic techniques, devices, surgical procedures and drugs. It has been
suggested that a means to control the immune inflammatory response is required
but existent drugs have not been proven safe for utilization in infants and
young children.
The importance of accurate diagnosis has been confirmed by a study
indicating that eighty percent of these individuals with congenital disease
retained their prosthesis while only 50% with acquired opacity retained the
initial device. 44% of those with congenital disease demonstrated improved
vision while this dropped to 10% in those with acquired disease [22]. The
convention of reporting keratoprosthesis results as short term less than 2
years, intermediate term from 2 to 5 years and long term 5 years or more [28].
It is to be noted that the Flaum group reports a cadre in which the device has
been retain for periods of 10 to 17 years.
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