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1. Preoperative assessment
(1) Systemic assessment：
- Take extra caution with patients with diabetes and immune diseases as the postoperative corneal re-epithelialization may be slower and sensitivity to the sutures may cause rejection and hence cause incomplete epithelization or graft dissolution
- Key points for eye examination: a. Visual function assessment: Corrected visual acuity, vision-related quality of life (especially for corneal endothelium transplant patients), etc. b. Ocular surface and appendages examination: Presence or absence of ocular protrusion, ptosis in the upper eyelids, incomplete closure of eyelids, scars and movement disorders of the eye, tear film function, and lacrimal passage function. c. Slit lamp microscopy: affected eye and contralateral eye conditions, extend and location of lesions, depth of lesions, corneal edema severity, corneal neovascularization, corneal fluorescein staining, presence of keratic precipitates, depth of anterior chamber, anteroposterior adhesion, condition of pupil, transparency and position of lens, condition of retina and optic nerve
(2). Laboratory examination
Sensible and necessary lab tests are conducive to early and definitive diagnosis, and for the determination of the severity of the conditions. Routine lab tests for infectious keratitis as follows:
a. Corneal scraping test: Including pathogen examination under smear microscopy, microbial culture and drug sensitivity test;
b. Confocal microscopy：Valuable diagnostic tool for fungal and amoebic keratitis, recommend hospitals that can support this examination to conduct the test；
c. AS-OCT：Assessment of the size and depth of lesion to assist in development of surgical protocols;
d. Ultrasound：To better understand the condition of the anterior chamber, angle opening degree, conditions of lens and suspensory ligament, of great diagnostic value for pre-adherent corneal leukoplakia and congenital leukoplakia;
e. Intraocular pressure management: If the intraocular pressure is too high, should first lower the IOP to lower the risk of the operation and enhance the success rate;
f. Corneal topography： to assess keratoconus and other corneal degenerative diseases;
g. Other tests: Anterior segment photography, B ultrasound, orbital X-ray examination, etc.
To summarize: Ultrasonic examination of the thickness of the cornea must be performed. Careful examination under the slit lamp is also important. The surgeon should comprehensively evaluate the results from the ultrasound and slit lamp to decide how deep to dissect in-op to prevent perforation. Currently, AS-OCT can show the relationship between the corneal thickness and disease, making it one of the most important pre-op examinations.
2. Surgical Procedures
Basic Principle: For infectious keratopathy, remove the infected lesion as much as possible, control the infection, promote corneal tissue repair and reduce scar formation; For non-infectious keratopathy, take into account the size of the lesion and the possibility of post-op immune rejection to determine the extent of resection.
➢Open the outside cardboard packaging
➢ Under sterile conditions, tear open the inner plastic packaging.
➢ Open the upper lid and inject saline. Allow to soak for approximately 60 seconds for 300micrometers graft (90seconds for 450micrometers) and then open the top lid to get the graft for use.
➢ Make sure to strictly control the soaking duration (60 seconds). Do not soak for too long. Use a trephine to tailor the graft accordingly after soaking.
A. Fixate the eyeball：
Recession of rectus muscle by suture or Flieringa scleral support ring.
B. Preparing the corneal bed:
a. To improve visual acuity, when selecting the corneal bed, center on the optical center of the cornea as much as possible;
b. When using the trephine, make sure to cut through evenly;
c. Use trephine, vacuum trephine, or femto-second laser to prepare the corneal bed and graft;
d. The edge of the corneal bed should be perpendicular to the bed surface and not diagonal;
e. For LKP, the depth of dissection is generally required to be more than ½ of the corneal thickness
C. Suturing the graft onto the corneal bed：
a. Suture methods include interrupted and running sutures;
b. Usually use 10-0 nylon sutures;
c. Avoid damaging the endothelium of the graft during surgery
d. Suture at around 4/5 of the depth of the cornea or above, the suture should span approx. 3mm
3. Intraoperative points to note,
a. Flush conjunctival sac to ensure sterility
b. Remove all ulcers, try to dissect all the way to the Descemet’s membrane
c. According to the type of infection, flush with appropriate medications in-op
d. Try to avoid or cover the central iris area to achieve better optical effect
e. Communicate with the company pre-op to inquire the rehydration time required for the graft
f. For graft bed > 8mm, use of Acornea is not recommended
g. Graft and bed diameter should be equal
h. When suturing, ensure the graft and the bed is on the same level and make sure to keep the interface smooth to allow better re-epithelialization and repair