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Tissue
Harvesting - Eye Ball Collection
(Enucleation) |
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Removal
of eye balls from a dead body done either by an ophthalmologist
or trained registered medical practitioner is known as Enucleation.
Before removal, the eyes are made aseptic by standard surgical
procedures. Maintaining aseptic conditions during and after
removal of the eyes is extremely important.
Sterilized instruments, sterile gloves, etc., are used for
enucleation. The time taken by an experienced doctor is about
20 to 30 minutes for both eyes. After the eyes have been removed,
a ball of cotton wool is tightly packed in the empty eye socket
or artificial eye balls are placed inside. The eye lids are
sometimes stitched with a black thread. This gives an appearance
as if the donor is asleep. There is absolutely no
disfigurement of the face after eyes are removed. The enucleated eye balls are transported in a special glass
bottle with a metal stand termed as Moist Chamber to the nearest
processing and evaluation centre. The Moist Chamber is transported
at 4 degrees centigrade.
According to the "Transplantation of Human Organs Act, 1994,"
applicable to the States of Maharashtra, Goa and Himachal
Pradesh and all Union Terrtories, only a registered medical
practitioner is permitted to "enucleate" the eyes from a dead
body. In Europe, U.S.A. and several other countries, a technician
trained can enucleate or perform an in-situ corneal excision
for the purpose of transplantation. This would bring down
the time gap between death and enucleation. The registered
medical practitioner would not have to rush to the location
of death while there are many patients waiting in his own
clinic for treatment. |
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Removal
of Corneas by Trained Technicians
(In-situ corneal excision) : |
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The most common method used in Europe,
USA and several other countries is In-situ corneal excision
(direct removal of corneas from the dead body). This method
not only saves time but also prevents the cornea from deterioration.
The cornea is cut and separated from the eyeball and stored
in a suitable nutritive medium. The whole eye ball is not
preserved. This medium helps in prolonging the life of a cornea
by about 3-4 days. Known today as M.K. Medium it is now available
from the L.V. Prasad Eye Institute, Hyderabad and all members
of the Eye Bank Association of India at a nominal charge.
While using MK medium, adequate care and precaution needs
to be taken while cutting and separating the cornea from the
eye ball and storing it in the medium so as to avoid contamination.
In other words, this must be done in a totally aseptic environment;
as otherwise, the ingredients of the medium whilst being useful
in prolonging the life of corneal tissue can also prove nutritive
to the harmful bacteria which can damage the tissue itself. |
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Tissue
Processing - Surgical Removal of Cornea
(Anterior Section) : |
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When whole eye balls are collected from
the donor, the corneas is cut and separated from the eyeball
and stored in a suitable nutritive medium. Stringent aseptic
conditions need to be maintained as in the case of In-situ
corneal excisions. The time gap between death and cornea preservation
in our country SHOULD NOT EXCEED 6 to 7 hours failing which the quality of the cornea is not suitable for
optical penetrating keratoplasty (surgery for restoring vision).Similar
observations have been made by the Santa Lucia Eye Bank in
Manila, Philippines where similar climatic conditions prevail. |
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Tissue
Evaluation using Slit Lamp : |
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Despite the introduction
of sophisticated equipment in Tissue Evaluation, the SLIT
LAMP continues to remain the most important tool for corneal
evaluation. It is very much a part & parcel of routine corneal
evaluation, including both whole eyeball and the excised corneal
button in the media.
A SLIT LAMP is an Ophthalmological tool consisting of a Microscope
combined with a rectangular light source that can be narrowed
into a Slit. Primarily it helps us to determine the suitability
of tissue for surgical Use. It enables the technologists to
study the layers of the cornea individually (Epithelium, Stroma
& Endothelium), bringing to limelight the intricate flaws
in the tissue and allowing us to inspect the Surface and the
deeper layers thoroughly. Corneal defects can be examined
with greater accuracy and more detail. It can reveal earlier
stages of Corneal pathology much better than are visible grossly.
Last but not the least it is especially valuable in Qualitative
Assessment of the health of the Endothelium, which is a critical
factor for corneal transplant. |
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Tissue
Analysis using Keratoanalyser : |
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'Endothelium’ is a single innermost layer
of cornea and is primarily responsible for the quality of
the vision after a cornea grafting surgery. Therefore, assessment
of its integrity is critical in making a judgement about its
utility for corneal grafting.
The structure can be studied by slit lamp examination which
provides reliable information. This is performed in most eye
banks by trained individuals. However, the technique of specular
microscopy allows direct high magnification of the endothelial
cells and consequently better judgement of its status by counting
the number of cells / mm square. . |
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Tissue
Screeing - Serology
(Mandatory Blood Tests) : |
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Serology has been routinely perfomed
to screen for infectious diseases such as AIDS (HIV), Hepatitis
(HBsAg), Sexually transmitted Diseases (VDRL), etc. Auto-analysers
have been implemented for the above tests in order to minimize
human errors from time to time. . |
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Tissue
Distribution as per Wait List : |
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Corneas
are distributed on a first-cum-first-serve basis although priority
is given to bilaterally blind recipients (blind in both eyes).
Online eye banking can be a useful tool to maintain acountability
and transparency at every level within every eye bank. |