Editing Cornea (section)

===Management===
[[File:Cornea.jpg|thumb|[[Slit lamp]] image of the cornea, iris and lens (showing mild [[cataract]])]]

====Surgical procedures====

Various [[refractive eye surgery]] techniques change the shape of the cornea in order to reduce the need for corrective lenses or otherwise improve the refractive state of the eye. In many of the techniques used today, reshaping of the cornea is performed by photoablation using the [[excimer laser]].

There are also synthetic corneas (keratoprostheses) in development.  Most are merely plastic inserts, but there are also those composed of biocompatible synthetic materials that encourage tissue ingrowth into the synthetic cornea, thereby promoting biointegration. Other methods, such as magnetic deformable membranes<ref>{{cite journal |first1=Steven M. |last1=Jones |first2=Sandra E. |last2=Balderas-Mata |first3=Sylwia M. |last3=Maliszewska |first4=Scot S. |last4=Olivier |first5=John S. |last5=Werner |title=Performance of 97-elements ALPAO membrane magnetic deformable mirror in Adaptive Optics - Optical Coherence Tomography system for ''in vivo'' imaging of human retina |journal=Photonics Letters of Poland |volume=3 |issue=4 |year=2011 |pages=147–9 |url=http://photonics.pl/PLP/index.php/letters/article/view/3-52}}</ref> and optically coherent [[transcranial magnetic stimulation]] of the [[Retina|human retina]]<ref>{{cite book |doi=10.1109/IEMBS.2010.5627660 |pmid=21097016 |chapter=Towards direct head navigation for robot-guided Transcranial Magnetic Stimulation using 3D laserscans: Idea, setup and feasibility |title=2010 Annual International Conference of the IEEE Engineering in Medicine and Biology |volume=2010 |year=2010 |last1=Richter |first1=Lars |last2=Bruder |first2=Ralf |last3=Schlaefer |first3=Alexander |last4=Schweikard |first4=Achim |isbn=978-1-4244-4123-5 |pages=2283–86|s2cid=3092563 }}</ref> are still in very early stages of research.

====Other procedures====
[[Orthokeratology]] is a method using specialized hard or rigid gas-permeable [[contact lens]]es to transiently reshape the cornea in order to improve the refractive state of the eye or reduce the need for eyeglasses and contact lenses.

In 2009, researchers at the University of Pittsburgh Medical center demonstrated that [[stem cell]] collected from human corneas can restore transparency without provoking a rejection response in mice with corneal damage.<ref>{{cite journal |last1=Du |first1=Yiqin |last2=Carlson |first2=Eric C. |last3=Funderburgh |first3=Martha L. |last4=Birk |first4=David E. |last5=Pearlman |first5=Eric |last6=Guo |first6=Naxin |last7=Kao |first7=Winston W.-Y. |last8=Funderburgh |first8=James L. |year=2009 |title=Stem Cell Therapy Restores Transparency to Defective Murine Corneas |journal=Stem Cells |volume=27 |issue=7 |pages=1635–42 |pmid=19544455 |pmc=2877374 |doi=10.1002/stem.91}}
* {{cite news |date=13 April 2009 |title=Stem Cell Therapy Makes Cloudy Corneas Clear, According To Pitt Researchers |work=Medical News Today |url=http://www.medicalnewstoday.com/releases/145528.php}}</ref> For corneal epithelial diseases such as Stevens Johnson Syndrome, persistent corneal ulcer etc., the autologous contralateral (normal) suprabasal limbus derived in vitro expanded corneal limbal stem cells are found to be effective<ref>{{cite journal |doi=10.1089/ten.tea.2008.0041 |title=''Ex Vivo'' Cultivation of Corneal Limbal Epithelial Cells in a Thermoreversible Polymer (Mebiol Gel) and Their Transplantation in Rabbits: An Animal Model |year=2009 |last1=Sitalakshmi |first1=G. |last2=Sudha |first2=B. |last3=Madhavan |first3=H.N. |last4=Vinay |first4=S. |last5=Krishnakumar |first5=S. |last6=Mori |first6=Yuichi |last7=Yoshioka |first7=Hiroshi |last8=Abraham |first8=Samuel |journal=Tissue Engineering Part A |volume=15 |issue=2 |pages=407–15 |pmid=18724830}}</ref>  as amniotic membrane based expansion is controversial.<ref>{{cite journal |doi=10.1001/archopht.124.12.1734 |title=Inherent Risks Associated with Manufacture of Bioengineered Ocular Surface Tissue |year=2006 |last1=Schwab |first1=Ivan R. |journal=Archives of Ophthalmology |volume=124 |issue=12 |pages=1734–40 |pmid=17159033 |last2=Johnson |first2=NT |last3=Harkin |first3=DG|doi-access=free }}</ref> For endothelial diseases, such as bullous keratopathy, cadaver corneal endothelial precursor cells have been proven to be efficient. Recently emerging tissue engineering technologies are expected to be capable of making one cadaver-donor's corneal cells be expanded and be usable in more than one patient's eye.<ref>{{cite journal |pmid=18246029 |year=2008 |last1=Hitani |first1=K |last2=Yokoo |first2=S |last3=Honda |first3=N |last4=Usui |first4=T |last5=Yamagami |first5=S |last6=Amano |first6=S |title=Transplantation of a sheet of human corneal endothelial cell in a rabbit model |volume=14 |pages=1–9 |pmc=2267690 |journal=Molecular Vision}}</ref><ref>{{cite journal |last1=Parikumar |first1=Periyasamy |last2=Haraguchi |first2=Kazutoshi |last3=Ohbayashi |first3=Akira |last4=Senthilkumar |first4=Rajappa |last5=Abraham |first5=Samuel J. K. |year=2014 |title=Successful Transplantation of ''In Vitro'' Expanded Human Cadaver Corneal Endothelial Precursor Cells On to a Cadaver Bovine's Eye Using a Nanocomposite Gel Sheet |journal=Current Eye Research |volume=39 |issue=5 |pages=522–6 |pmid=24144454 |doi=10.3109/02713683.2013.838633|s2cid=23131826 }}</ref>

====Corneal retention and permeability in topical drug delivery to the eye====
The majority of ocular therapeutic agents are administered to the eye via the topical route. Cornea is one of the main barriers for drug diffusion because of its highly impermeable nature. Its continuous irrigation with a tear fluid also results in poor retention of the therapeutic agents on the ocular surface. Poor permeability of the cornea and quick wash out of therapeutic agents from ocular surface result in very low bioavailability of the drugs administered via topical route (typically less than 5%). Poor retention of formulations on ocular surfaces could potentially be improved with the use of mucoadhesive polymers.<ref>{{Cite journal|last=Ludwig|first=Annick|date=2005-11-03|title=The use of mucoadhesive polymers in ocular drug delivery|journal=Advanced Drug Delivery Reviews|series=Mucoadhesive Polymers: Strategies, Achievements and Future Challenges|volume=57|issue=11|pages=1595–1639|doi=10.1016/j.addr.2005.07.005|pmid=16198021|issn=0169-409X}}</ref> Drug permeability through the cornea could be facilitated with addition of penetration enhancers into topical formulations.<ref>{{Cite journal|last1=Khutoryanskiy|first1=Vitaliy V.|last2=Steele|first2=Fraser|last3=Morrison|first3=Peter W. J.|last4=Moiseev|first4=Roman V.|date=July 2019|title=Penetration Enhancers in Ocular Drug Delivery|journal=Pharmaceutics|volume=11|issue=7|pages=321|doi=10.3390/pharmaceutics11070321|pmid=31324063|pmc=6681039|doi-access=free}}</ref>