Cataract Surgery Following Corneal Transplant
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Cataract surgery following corneal transplant needs a lot of consideration.
It is important to plan the surgery as there are a number of variables to consider that will impact not only the quality of cataract surgery but also the long-term survival of the corneal graft. 
The concerns are planning the appropriate IOL power to be implanted, the need for appropriate visco elastics to protect the graft, maintaining endothelial integrity. Other factors to consider are Intra operative visualization, loss of epithelial integrity and strength of the graft host junction. Post operatively increased risk of rejection of the corneal transplant , combatting preoperative astigmatism brought about by the corneal sutures and careful wound closure becomes paramount.
• Formation of cataracts can be accelerated after penetrating keratoplasty (PK) and these eyes may require early cataract surgery 
• The reasons responsible for cataract development are:
o intraoperative manipulation during surgery
o use of air tamponade
o multiple surgeries
o postoperative long-term steroid use.
• Phakic patients with clinically significant cataract and endothelial dysfunction are probably better managed by performing simultaneous cataract surgery with endothelial keratoplasty.
• In paediatric patients, combined surgery is avoided in order to preserve accommodation.
• Cataract surgery in eyes which had undergone DSAEK previously is of concern as this may affect the graft adversely and threaten graft survival. 
• Two reports following DSEK showed presence of cataract in 40% at 1 year in one study.
• Studies following DMEK showed a 76% progression in cataract.
• Following DSEK/DMEK the endothelial cell loss rate can be as high as 56% in the first year and with standardized technique the cell loss has been reduced to less than 35%  
• In patients undergoing DMEK, the endothelial cell count loss at 1 year is around 25%. 
When to Operate :
• Penetrating Keratoplasty should be allowed to stabilize prior to cataract surgery. Keratometric stabilization of corneal grafts occurs 1-2 months after all sutures have been removed but approximately 12 months are required before performing cataract surgery. 
• But this also leads to fluctuation of visual acuity and delay in visual rehabilitation in such patients.
Pre operative Considerations
• IOL POWER CALCULATION becomes difficult. Due to induced astigmatism in PK/ DALK, the need Toric IOL calculation is important.
• Use of topography to assess the graft becomes mandatory. In patients after Endothelial Keratoplasty there has been documented hyperopic and myopic shifts .The amount of shift varies from surgeon to surgeon and is likely due to donor graft thickness and shape, incision size and other variables. 
• In full thickness grafts all sutures are preferably removed before cataract surgery.
• In low astigmatism or orthogonal astigmatism , selective suture removal can be done to prevent sudden increase of astigmatism.
• Toric IOLs/ other customized IOL’s may be required to correct post-keratoplasty astigmatism.
• Endothelial cell count to be assessed by specular microscopy
• The site of internal incision in relation to the edge of the lamellar graft.
• Reduced working space in the anterior chamber should be kept in mind in post corneal transplant cases.
• Proper Continuous Curvilinear Capsulorhexis.
• Reduction of phaco energy while operating.The main goal of the surgeon should always be not to cause any kind of endothelial injury. It is reported that phacoemulsification-related endothelial cell loss in transplanted corneas is higher than that in normal corneas.
• Turbulence during insertion of the phaco handpiece with irrigation, which can potentially lead to graft dislodgement..
• Cold phaco technique using torsional phaco.
• Phaco Chop technique.
• Avoid longitudinal phaco.
• Use of high density viscoelastic.
• Avoid fluctuation in the AC.
• Soft shell technique. Use a high density visco elastic surrounded by low density to protect the endothelium
• Lower infusion pressure to avoid placing stress in the graft-host junction in the corneal tissue.
• Avoid touching endothelium.
• During nucleus removal, ultrasound time to be minimized. The mechanical energy released with ultrasound use as well as free radical formation and deflected nuclear fragments; small bubbles can also cause damage to the endothelium. Emphasis on mechanical forces as well as working in the capsular bag (very posteriorly) are means of minimizing endothelial damage during this important phase.
• Wound closure to minimize risk of leakage
Post operative Considerations
• Start frequent topical steroids to minimize inflammation.
• Will need long term low dose steroids even after the cataract post op period is over to prevent graft rejection.
• Delayed visual rehabilitation
• Patient has to undergo a second surgical procedure for cataract extraction
• Cost and risks of Anaesthesia
• Increased risk of endothelial cell loss
When cataract surgery is indicated following penetrating keratoplasty, the following principles are observed
• The interval between keratoplasty and cataract extraction should be at least 6 months and preferably 12 months
• The eye is made hypotensive before surgery with aid of oral dorzolamide & IV mannitol given half hour before surgery.
• Stable regular refraction
• Good graft clarity
• Use of visco-elastic to protect the graft
• Customized Toric IOL
• Good surgical technique
• Effort is made to avoid touching the endothelium
• Tight wound closure should be ensured
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