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a corneal perforation requires emergency treatment to avoid vision - threatening complications including bacterial endophthalmitis and hypotony [ 1 , 2 ] .
several materials such as cryopreserved   and hyperdried   amniotic membrane , sclera , and cornea   have been used as patch grafts to close perforations .
we report the case of a corneal perforation treated with cryopreserved partial - thickness corneal patch grafting . in this case
a 73-year - old woman , referred to a general ophthalmologist for a 1-week history of sudden tearing and decreased vision in her left eye ( os ) , presented to our hospital on the same day of the referral .
best corrected visual acuity and intraocular pressure in that eye were 0.15 and 2 mm hg , respectively . slit - lamp examination and ultrasound
biomicroscopy showed a corneal perforation about 1 mm in diameter superotemporally , iris plugging , and flat anterior chamber ( ac ) os ( fig .
1a , b ) ; fibrin formation and floating cells were in the ac , but endophthalmitis or an infectious corneal ulcer was not identified .
the past history included uneventful small - incisional cataract surgery os and vascular stent surgery for cardiac infarction several years previously . during farm work
2 months previously , the patient had reported a foreign - body sensation os that subsided within a few days .
the past history and blood / urinary laboratory examinations did not identify immunocompromised conditions , systemic infectious diseases , or steroid use .
cultures of scraped corneal tissue and ac fluid did not detect any microorganisms . the patient was diagnosed with a corneal perforation of undetermined etiology .
a residual partial - thickness corneal button cut using a 350-m microkeratome and an 8-mm - diameter donor punch during a previous descemet stripping automated endothelial keratoplasty ( dsaek ) surgery were used as a patch graft . until use
, the corneal button was stored at 80c in optisol gs ( bausch & lomb , rochester , n.y .
after the limbal peritomy , iris plugging was released by injection of a viscoelastic into the ac .
after dbridement of the perforation edge and deepithelialization of the surrounding cornea , the corneal button , trimmed to two thirds of its size , was secured with 8 interrupted 10 - 0 nylon sutures on the host cornea and adjacent perilimbal sclera to cover the corneal defect .
prophylactic antibiotic treatment included 1 intravitreal injection of 2 mg ceftazidime and 1 mg vancomycin , oral cefdinir 300 mg daily for 5 days , topical 0.3% ofloxacin ointment once daily for 5 days , and topical 1.5% levofloxacin 6 times daily for 2 weeks and then 4 times daily for 1 month .
topical 0.1% betamethasone was started 3 times daily and tapered gradually but continued once daily until the last visit 5 months postoperatively .
five days postoperatively , the ac was reformed and the perforation was masked by the donor cornea ( fig .
anterior - segment optical coherence tomography ( as - oct ) images showed a corneal defect under the donor cornea ( fig .
1d ) . during the next several weeks , gradual displacement of the anterior edge of the donor cornea in the limbal direction occurred .
seven weeks postoperatively , further displacement of the donor cornea resulted in unmasking of the perforated area ( fig .
at this time , the corneal defect was closed by stromal scar tissue and corneal epithelium ( fig .
1f ) ; corneal topographic maps obtained by a rotating scheimpflug camera ( pentacam ; oculus , wetzlar , germany ) showed no marked astigmatism ( fig .
five months postoperatively , best corrected visual acuity was 1.0 without marked astigmatism , and intraocular pressure was 9 mm hg os .
at the initial visit to our hospital , we observed marked corneal surface vascularization extending from the limbus toward the corneal defect , suggesting that the pathology had started several weeks before the perforation .
as reported by the patient , minor trauma 2 months previously could have been the etiology of the perforation .
based on the postsurgical observation , the anterior edge of the donor cornea seemed to be displaced by gradual melting of the donor tissue rather than shrinkage of the entire corneal button .
thus , sterile sclerocorneal melting is another possible underlying mechanism of corneal perforation in this case . as reported previously , 
split corneal transplantation that uses one donor cornea for two recipients by dsaek and lamellar keratoplasty was scheduled simultaneously   or dsaek was performed first followed by patch grafting a maximum of 4 weeks later using a remaining corneal flap stored at 4c .
thus , use of a dsaek - derived corneal flap stored at 80c as a patch graft for corneal perforation is unique . when using full - thickness sclera   or cornea , to adjust the thickness these were required to dissect before patch grafting .
accordingly , its  ready - to - use thickness and size seemed to be the merit of the dsaek flap as a patch graft .
previously , all 20 corneal flaps stored at 4c were structurally intact at least 19 months after patch grafting .
accordingly , we could not exclude the possibility that cryopreservation was related to the graft melting in the current case
. it can be difficult for scar tissue to fill scleral stroma , probably because of its relatively poor vascularity and cellularity ; however , it was reported that scleral patch grafting combined with a cyanoacrylate tissue adhesive for corneal perforations generally results in fibrous tissue formation .
we report that fibrous tissue formation can fill a corneal defect even after patch grafting , using a corneal button . from this case
, we learned that cryopreserved dsaek flaps stored longer than reported previously can be used as patch grafts to treat emergency conditions .
scar tissue can fill a corneal stromal defect 1 mm in diameter during temporary patch grafting for less than 2 months .
written informed consent was obtained from the patient for publication of this case report and any accompanying images .
the authors declare that there is no conflict of interest regarding the publication of this paper .
a 73-year - old woman with a corneal perforation of undetermined etiology was treated with corneal patch grafting . 
 a residual partial - thickness corneal button obtained during a previous descemet stripping automated endothelial keratoplasty ( dsaek ) surgery and stored at 80c in optisol gs for 3 months was used as a patch graft . 
 five days postoperatively , the anterior chamber was reformed and the perforation was masked by the donor cornea . during the next several weeks , gradual displacement of the anterior edge of the donor cornea in the limbal direction occurred . 
 seven weeks postoperatively , further displacement of the donor cornea resulted in unmasking of the perforated area . at this time 
 , the corneal defect was closed by stromal scar tissue and corneal epithelium . 
 five months postoperatively , best corrected visual acuity was 1.0 without marked astigmatism and intraocular pressure was 9 mm hg in the left eye . from this case , we learned that cryopreserved dsaek flaps stored longer than reported previously can be used as patch grafts to treat emergency conditions . 
 scar tissue can fill a corneal stromal defect 1 mm in diameter during temporary patch grafting for less than 2 months .