`thesoporificmushroom
12/14/09
Dupont Essay Rough Draft
Imagine a life of total blindness. This is the struggle many face every day because
of the failed attempts to treat ocular surface disorders. In the past, these disorders
were a huge problem for surgeons and patients and posed a challenge to treat
completely. Consider re-wording. The most common form of treatment for what? was a
complete corneal transplant, replacing the damaged cornea with healthy corneal tissue
from a donor. Patients with disorders and diseases What disorders and diseases? that
damage the corneal epithelium, the outer surface of the eye, and severely impair vision
and the quality of life, such as those with ocular burns and Steven-Johnson syndrome
required this transplant but continued to suffer because of its inefficiency (Tsai et al.,
2000). Run on sentence try to combine or make into two thoughts. Corneal transplants
have a rejection rate of up to 30 percent, require a long recovery time and often fail to
improve vision how long? (Burman & Sangwan, 2008). Ocular surface scarring,
vascularization, persistent epithelial defects and dry eye all can persist following a
corneal transplant. Explain what “Ocular surface scarring, vascularization, persistent
epithelial defects” are, I don’t know what they are. The integrity of the corneal
epithelium relies upon the existence of limbal stem cells. According to Dua & AzuaraBlanco (2000), stem cells are essential for cell regeneration and repair and help maintain
homeostasis. They have asymmetric self-renewal, simultaneously replicating and
producing cells with high fidelity, potency, differentiation into different cell lineages,
and slow cell cycling. These properties give them unique opportunities with regards to
ocular surface reconstruction. Pelligrini first used limbal stem cells in sheet form to treat
patients with corneal damage in 1997 (Sullivan & Clynes, 2007). Those limbal stem cell
transplants have yielded promising results and are now used to treat ocular surface
disorders by the medical community.
You do not have a true introduction paragraph and a thesis. Your introduction
should explain what is to come not just be a list of facts. This seems to be more of a
body paragraph to me. Also, a lot of the vocabulary and descriptions you use are
unfamiliar to the average person. Lastly, there are a lot of run-on sentences in this
paragraph. Try to combine more than one sentence, or make your ideas clearer.
Limbal stem cells are supported by a unique microenvironment called the stem
cell niche. Research by Charukamnoetkanok (2006) supports that the stem cell niche,
named the Palisades of Vogt, protects limbal cells and helps maintain their amazing
properties. Limbal stem cells are classified as “label retaining cells,” meaning that they
have a very slow cell cycling time. I have no idea what you are talking about you have to
explain what Limbal cells are and what they do first. Also what is a cell niche, what
makes Palisades of Vogt special extc. They also have asymmetric self-renewal,
simultaneously replicating and producing cells with high fidelity and can differentiate
into different cell lineages. Better but what is high fidelity?? This gives them the
property to replace whatever cell type needs them the most. (Li et al. 2007). There has
to be a better way to explain your thoughts in the first 5 sentences. It is very unclear and
is not understandable to someone who has some knowledge in the field. Limbal cells
have a higher in vitro proliferative rate what is that?? than corneal epithelial cells,
making them more effective in corneal transplants (Pfister, 1994). Why? The corneal
epithelium requires constant renewal, the source of this renewal comes from the limbus
what is a limbus? . Since many ocular disorders damage the epithelial surface of the
cornea, a limbal transplant will replace damaged cells because of its unique capabilities
as a stem cell. The limbal cells will differentiate into corneal epithelial cells after they
are transplanted, improving visual acuity.
You are VERY unclear. I have no idea what you are talking about half of the time. You
have to simplify your thoughts.
Scientists have begun exploring the potential of limbal stem cells in corneal
surface reconstruction. Again what is corneal surface reconstruction,. Use of autograft
and allograft transplantations of limbal stem cells as an alternative to corneal
transplants are increasing across the world. Unclear, explain the differences in very
SIMPLE terms at the start of the paragraph before you give deep dietals. Autograft
transplantations are used in patients with unilateral ocular damage. Limbal cells are
taken from the healthy contralateral eye and transplanted into the damaged eye. Limbal
stem cells can be expanded on an amniotic membrane and then transplanted but that
isn’t always required. Amniotic membrane use to expand limbal stem cells in
combination with this procedure allows for more rapid re-epitheliazation (use a simpler
word) and may help prevent infection (Meller et al., 2002). Allograft transplantations
are used in patients with bilateral ocular damage. THIS SHOULD BE AT THE BEGINNING.
Limbal cells are taken from relatives and transplanted into both eyes. Even though
tissue is HLA matched and living donors are preferred, immunosuppressants are still
required following the surgery and cyclosporine A the most commonly used
immunosuppressant. Why do they use immunosuppressants, why do they use family,
why are living donors preferred, what are immunosuppressants, you have to remember
you are writing to someone with limited knowledge. Both allograft and autograft
surgeries can be followed by additional ocular surgeries, like keratoplasties which
replace corneal tissue with healthy tissue from an eye bank, for improved visual clarity.
Both procedures have improved the corneal surface more than and have a shorter
follow-up period compared to standard corneal transplants (Ozdemir et al., 2004).
Personally, I have no idea what is going on in this paragraph. With that said I do not
have a lot of knowledge in the field of limbal cells, but I should at least understand what
you are writing about. I am VERY hard time understanding your vocabulary and
descriptions of the surgeries.
Research has shown that autograft transplants yield better outcomes than
allograft transplants. In an experiement by Ozdemir et al. (2004), limbal allograft
transplant patients had a follow up period that was 4 months longer than the autograft
patients and only 11% of transplants resulted in functional vision whereas with limbal
autografts it was 80%. The authors WHO GIVE CREDIT also explained how it is more
difficult to reduce corneal vascularization with allograft transplants. Corneal
vascularization (you still need to give a simple explanation for what that is) regressed in
all patients with autograft transplants but only in 4/9 patients who underwent allograft
transplantations. The authors WHO speculate the failure of many allograft
transplantations is due to the advanced stage of ocular surface destruction that the
patients in the allograft group in the experiment had. The rate of rejection is much
lower and visual clarity is higher. They WHO also consider that perhaps the role of
allograft transplantations, instead of to completely treat, should be to stabilize the
ocular surface for future surgeries. Keratoplasties (which is… for example you can say
blah blah blah blah which is known as kertoplasties) are usually performed 3 months
after surgery when the eye surface is stable. It decreases the risk of corneal graft
rejection by controlling inflammation. Many people do not have a choice between
autograft and allograft surgery. Autograft surgery is only available to those with
unilateral ocular surface disorder since the limbal cells must be derived from the healthy
contralateral eye. Allograft surgeries are probably less effective because the limbal cells
are derived from another person.
This is your best paragraph so far, but it still needs work, you can still make your
descriptions easier to understand and your sentence structure better
There have been significant advancements made towards a better
understanding of corneal surface disorders. This has led to the introduction of many
new and effective types of surgery being made available across the globe. Promising
research and studies have shown limbal allograft and limbal autograft surgeries to be
some of the most efficient types to treat ocular surface disorders. By continuing to
explore the vast potential of these limbal stem cells, further uses and applications can
be discovered. The full potential of limbal stem cells and their astonishing healing
properties has yet to be unearthed.
Great conclusion
Thecanadiansensation
References
Burman, S., & Sangwan, V. (2008). Cultivated Limbal Stem Cell Transplantation for
Ocular Surface Reconstruction. Clinical Ophthalmology, 2(3), 489-502.
Charukamnoetkanok, P. (2006). Corneal Stem Cells: Bridging the Knowledge Gap.
Seminars in Ophthalmology, 21, 1-7.
Dua, H.S., & Azura-Blanco, A. (2000). Limbal Stem Cells of the Corneal Epithelium.
Survey of Opthalmology, 44, 415-425.
Meller, D., Pires, R.T.F., & Tseng, S.C.G. (2002). Ex Vivo Preservation and Expansion of
Human Limbal Epithelial Stem Cells on Amniotic Membrane Cultures. Br J
Ophthalmol, 86, 463-471.
O’ Sullivan, F., & Clynes, M. (2007). Limbal Stem Cells, a Review of their Identification
and Culture for Clinical Use. Cytotechnology, 53(1-3), 101-106.
Ozdemir, O., Tekeli, O., Ornek, K., Arslanpence, A., & Yalcindag, N.F. (2004). Limbal
Autograft and Allograft Transplantations in Patients with Corneal Burns. Eye, 18,
241-248.
Pfister, R.R., (1994). Corneal Stem Cell Disease: Concepts, Categorization, and
Treatment by Auto-and Homotransplantation of Limbal Stem Cells. The Contact
Lens Association of Opthalmologists, 20, 64-72
Tsai, J., Li, L.,& Chen, J. (2000). Reconstruction of Damaged Corneas by
Transplantation of Autologous Limbal Epithelial Cells. The New England Journal
of Medicine, 343, 86-93.
Li,W., Hayashida, Y., Chen, Y., Tseng S. (2007). Niche regulation of corneal epithelial
stem cells at the limbus. Cell Research, 17, 26-36.