to report two cases of femtosecond laser - assisted small incision deep lamellar endothelial keratoplasty ( dlek ) for patients with corneal endothelial decompensation by fuchs dystrophy and glaucoma
irvine , ca ) with 15 khz of repetition rate , was used for a 9.5 mm diameter by 400 m thickness donor corneal lamellar dissection .
in case 1 , the graft was clear and compact without interface haze , orbscan showed smooth and regular corneal surface , specular microscopy was unremarkable without sign of corneal endothelial damage , and optical coherence tomography showed uniform graft well attached to recipient stroma with minimal interface reflection at 2 months postoperation . in case 2 , the graft was clear and compact with minimal interface haze at 1 month postoperation .
femtosecond laser - assisted small incision dlek was safe and technically feasible in our cases ; however , further evaluation is required to determine long - term effects .
the donor corneoscleral button was mounted in a dedicated artificial anterior chamber ( bausch & lomb , st .
this was to assure a donor corneal thickness between 500 and 565 m , in order to approximate a graft thickness of 100 to 165 m . the femtosecond laser ( intralase ; intralase corp . , irvine , ca ) was then used to create a corneal flap of 9.5 mm diameter and 400 m thickness .
femtosecond laser parameter settings were as follows : raster energy 3.6 j , spot separation 10 m , line separation 10 m , side cut energy 3.8 j , spot size 2.4 m , and repetition rate 15 khz .
after laser application , stromal and side cut adhesions were fully released and the anterior corneal flap was fully lifted .
the donor corneoscleral button was then placed in medium and transported to the operating room , where the anterior flap was excised with scissors and an 8.0 mm trephine ( katena products , inc . , denville , nj ) was used to punch out the posterior donor corneoscleral button . the recipient corneal lamellar dissection and graft transplantation
was performed as previously described.5,6 briefly , following an 8.0 mm epithelial marking and 5.0 mm scleral incision , a deep lamellar pocket was created to approximately 75 - 85% of corneal thickness .
the posterior recipient disc was then excised with cindy scissors ( bausch & lomb ) using the 8.0 mm epithelial mark as a template .
the excised posterior recipient disc was removed from the lamellar pocket and spread over recipient corneal epithelium to verify size .
an 8.0 mm pre - prepared posterior donor disc was then folded , endothelial side inside , with a layer of viscoelastic ( healon ; pharmacia , peapack , nj ) coating the endothelium and inserted into the anterior chamber through the small incision using forceps .
the folded donor disc was opened and attached to the recipient stromal bed by injecting air underneath the graft .
the scleral wound was closed with 2 or 3 interrupted 10 - 0 nylon sutures and air was replaced with balanced salt solution to normalize intraocular pressure ( iop ) .
femtosecond laser - assisted small incision dlek was performed in the right eye of a 73-year - old male with fuchs dystrophy ( fig .
1 ) . preoperative uncorrected visual acuity ( ucva ) and best spectacle corrected visual acuity ( bscva ) was 20/100 and 20/80 respectively and manifest refraction was + 0.75 -1.7530 .
donor corneoscleral button lamellar dissection was performed using intralase femtosecond laser ( intralase corp . ) , set at a depth of 400 m and flap diameter of 9.5 mm .
ucva and bscva was 20/150 and 20/100 respectively and manifest refraction was + 2.75 -1.0050 .
corneal topography showed smooth and regular corneal surface and specular microscopy was unremarkable without sign of corneal endothelial damage ( fig .
optical coherence tomography ( oct ) findings showed compact and uniform graft , well attached to the recipient stromal bed with minimal interface reflection ( fig .
3 ) . femtosecond laser - assisted small incision dlek was performed in the left eye of a 94-year - old female with corneal edema , glaucoma , and dry type age - related macular degeneration ( armd ) .
her preoperative ucva and bscva was 20/400 and 20/200 respectively and her manifest refraction was -1.00 -1.7595 .
iop was well controlled with topical medication ( cosopt ; merck & co. , whitehouse station , nj ) .
postoperation , the graft was clear and compact , iop was 19 mmhg , and ucva was 20/400 .
at one month , the graft was clear and compact with minimal interface haze ; iop measured 31 mmhg .
anti - glaucoma medication ( alphagan ; allergan , irvine , ca ) was added and topical steroid tapered .
we were not able to perform further examinations due to follow - up loss at two months postoperation .
all methods adhered to the declaration of helsinki of the world medical association for research involving human subjects .
the donor corneoscleral button was mounted in a dedicated artificial anterior chamber ( bausch & lomb , st .
this was to assure a donor corneal thickness between 500 and 565 m , in order to approximate a graft thickness of 100 to 165 m . the femtosecond laser ( intralase ; intralase corp . , irvine , ca ) was then used to create a corneal flap of 9.5 mm diameter and 400 m thickness .
femtosecond laser parameter settings were as follows : raster energy 3.6 j , spot separation 10 m , line separation 10 m , side cut energy 3.8 j , spot size 2.4 m , and repetition rate 15 khz .
after laser application , stromal and side cut adhesions were fully released and the anterior corneal flap was fully lifted .
the donor corneoscleral button was then placed in medium and transported to the operating room , where the anterior flap was excised with scissors and an 8.0 mm trephine ( katena products , inc . , denville , nj ) was used to punch out the posterior donor corneoscleral button . the recipient corneal lamellar dissection and graft transplantation
was performed as previously described.5,6 briefly , following an 8.0 mm epithelial marking and 5.0 mm scleral incision , a deep lamellar pocket was created to approximately 75 - 85% of corneal thickness .
the posterior recipient disc was then excised with cindy scissors ( bausch & lomb ) using the 8.0 mm epithelial mark as a template .
the excised posterior recipient disc was removed from the lamellar pocket and spread over recipient corneal epithelium to verify size .
an 8.0 mm pre - prepared posterior donor disc was then folded , endothelial side inside , with a layer of viscoelastic ( healon ; pharmacia , peapack , nj ) coating the endothelium and inserted into the anterior chamber through the small incision using forceps .
the folded donor disc was opened and attached to the recipient stromal bed by injecting air underneath the graft .
the scleral wound was closed with 2 or 3 interrupted 10 - 0 nylon sutures and air was replaced with balanced salt solution to normalize intraocular pressure ( iop ) .
femtosecond laser - assisted small incision dlek was performed in the right eye of a 73-year - old male with fuchs dystrophy ( fig .
preoperative uncorrected visual acuity ( ucva ) and best spectacle corrected visual acuity ( bscva ) was 20/100 and 20/80 respectively and manifest refraction was + 0.75 -1.7530 .
donor corneoscleral button lamellar dissection was performed using intralase femtosecond laser ( intralase corp . ) , set at a depth of 400 m and flap diameter of 9.5 mm .
ucva and bscva was 20/150 and 20/100 respectively and manifest refraction was + 2.75 -1.0050 .
corneal topography showed smooth and regular corneal surface and specular microscopy was unremarkable without sign of corneal endothelial damage ( fig .
2b and c ) . optical coherence tomography ( oct ) findings showed compact and uniform graft , well attached to the recipient stromal bed with minimal interface reflection ( fig .
femtosecond laser - assisted small incision dlek was performed in the left eye of a 94-year - old female with corneal edema , glaucoma , and dry type age - related macular degeneration ( armd ) .
her preoperative ucva and bscva was 20/400 and 20/200 respectively and her manifest refraction was -1.00 -1.7595 .
iop was well controlled with topical medication ( cosopt ; merck & co. , whitehouse station , nj ) .
postoperation , the graft was clear and compact , iop was 19 mmhg , and ucva was 20/400 .
at one month , the graft was clear and compact with minimal interface haze ; iop measured 31 mmhg .
anti - glaucoma medication ( alphagan ; allergan , irvine , ca ) was added and topical steroid tapered .
we were not able to perform further examinations due to follow - up loss at two months postoperation .
all methods adhered to the declaration of helsinki of the world medical association for research involving human subjects .
posterior keratoplasty refers to removal of diseased posterior corneal layers ( endothelium , descemet 's membrane , and posterior stroma ) and replacement by partial - thickness donor tissue .
this procedure can be an attractive alternative to penetrating keratoplasty ( pkp ) in treating corneal endothelial diseases such as fuchs dystrophy and aphakic and pseudophakic bullous keratopathy.13 - 15 the endothelial replacement technique via scleral incision was first described by melles and later modified by terry and ousley to ' deep lamellar endothelial keratoplasty ' ( dlek).3,4 recent modification includes introducing the folded donor disc through the a small incision.6 one problem in performing dlek is the technical difficulty associated with manual lamellar dissection .
it is not only time consuming , but also has the potential risk of corneal perforation.8 moreover , even with uncomplicated dissection , the plane may not be smooth and uniform , which results in interface scarring and reduction in potential best vision.6,7 in a recent paper , azar and coauthors described microkeratome - assisted posterior keratoplasty.16 given that laser - assisted in situ keratomileusis ( lasik ) shows almost no interface haze on the cornea,17,18 this technique 's potential advantage is less interface scarring than manual dissection .
however , microkeratome - assisted lamellar dissection does have the risk of corneal perforation in deeper dissection .
recently , the femtosecond laser was introduced in refractive surgery fields for lasik flap creation . according to recent papers
, it demonstrated improved flap uniformity and better flap thickness predictability than mechanical microkeratomes.9 - 12,19 similar to the microkeratome , femtosecond laser technology has evolved .
after initial procedures with a 2 khz laser in 1996 , 15 khz ( 2003 ) , 30 khz ( 2005 ) , and soon after , 60 khz ( 2006 ) engines were introduced .
pulses are scanned and placed in a vertical pattern for trephination ( side ) cuts or in a spiral or raster ( zigzag ) pattern to achieve lamellar cuts .
the smoothness of optical surfaces is determined by programmable parameters : energy per pulse , separation of adjacent laser spots ( spot separation ) , and raster pattern row spacing ( line separation ) .
the closer the laser spots , the less energy required.20 the intralase system scans tissue at a repetition rate which depends on laser engine capacity .
higher repetition rates allow use of lower pulse energy and closer spot / line separation settings , which results in a smoother lamellar interface , an easier anterior corneal flap lift , and a faster procedure .
the newer 60 khz engine permits a line / spot separation down to 66 m and energy less than 1 j per pulse , which may show superior efficiency for harvesting the posterior corneal disk.21 one concern during preoperative femtosecond laser - assisted donor eye posterior lamellar discs ( plds ) preparation is the possibility of endothelial cell loss ( ecl ) .
ecl has been reported at 4% after 150 to 200 m thick endothelial side plds preparations , and did not appear to be caused by laser pulse energy.22 another in vitro study reported 4.3% versus 7.7% ecl after 30 khz laser lamellar cutting compared to 15 khz laser for horizontal lamellar cuts at corneal depth of 400 m and 9.5 mm diameter.23 favorable outcomes are consistent with histological results showing adjacent thermal damage to be on the order of 1   m.24 clinical results from case 1 showed relatively intact postoperative endothelium status , which was comparable to previous reports .
moreover , the femtosecond laser is expected to be applied in full - thickness pkp .
cuts are customizable to achieve different graft geometric configurations , potentially allowing for sutureless , self - adhesive , or shaped keratoplasty .
two or more side / lamellar cut segments can be combined to create patterns for shaped keratoplasty , including top - hat ( larger diameter cut posteriorly ) , mushroom ( larger diameter cut anteriorly ) , zigzag , and christmas tree patterns.25 peripheral wound edge shaping can provide stronger healing by increasing surface area , reduce corneal astigmatism by decreasing suture number , reduce donor - host topographic distortion disparity , and quicken visual recovery .
following we describe small incision dlek by femtosecond laser for donor corneal lamellar dissection . before performing femtosecond laser - assisted donor lamellar dissection , we measured donor corneal thickness by ultrasound pachymetry .
if corneal thickness was thicker than 565 m , glycerin was applied to dehydrate the cornea , and avoid a thinner graft than intended , as well as to ascertain graft thickness of 100 to 165 m for transplantation .
the laser was then used to create a corneal flap of 9.5 mm diameter and 400 m thickness .
afterwards , two possible methods to obtain the posterior donor disc were used . in the first method ,
this bi - hinged donor corneoscleral button is then placed in medium , transported to the operating room , and punched out with an 8.0 mm trephine .
separation of the anterior and posterior donor corneal disc follows . in the second method , stromal and side cut adhesions
this donor corneoscleral button is placed in medium and transported ; following , the anterior flap is excised using scissors and the posterior part is punched out with an 8.0 mm trephine . in our cases
although the disadvantage is using scissors for anterior cap removal , there are other advantages . by removing the anterior cap ,
it is easier to visualize the posterior donor button edge , which may reduce a decentered donor cut .
furthermore , anterior and posterior donor disc separation is much easier , since the anterior flap is fully lifted and removed before trephination .
case 1 clinical results showed a clear and compact graft without interface haze at two months postoperation .
these findings were further confirmed in oct , which showed a clear and uniform graft with minimal interface reflection and good graft attachment . despite good clinical findings , postop visual acuity was not as expected .
however , the patient was satisfied and his vision fluctuation ( previously worse in the morning ) was eliminated .
considering findings and short - term follow - up , we may expect further improvement with time .
however , postop visual acuity did not improve because of low visual potential from dry armd and glaucoma .
unfortunately , this patient had an iop increase at one month postoperation and was unable to follow - up .
visual acuity after either pkp or dlek is mainly a function of retinal macular potential and cornea optical quality . in studies of pkp in young patients with keratoconus , postoperative visual results
are uniformly better compared to results in older fuchs ' dystrophy patients , despite similar graft problems of high or irregular astigmatism.26 this suggests that older maculas , may play a role in visual loss after any form of corneal transplantation , including dlek .
in contrast to pkp where the cornea contributes to refractive visual loss , often resulting from high or irregular astigmatism , in dlek , topography is usually normal and corneal visual loss is most likely attributed to the donor - recipient stromal interface .
the interface in dlek may account , on average , for 1 line of visual loss compared to the individual macular potential vision.27 other potential corneal factors include increased corneal thickness and posterior corneal curvature .
how this irregularity influences visual acuity requires further investigation . due to lack of long term follow - up and small case number
, we can not fully determine potential advantages of ' femtosecond laser - assisted small incision dlek ' .
however , these cases demonstrate graft uniformity , technical feasibility , and potential application of femtosecond laser in lamellar keratoplasty .
further evaluation with longer follow - up and more cases would reveal potential advantages . unfortunately , the use of femtosecond laser in recipient corneas is currently limited by the institutional review board .
also the femtosecond laser is not approved for cuts deeper than 400 m ; therefore recipient cornea posterior lip creation requires scissors .
hopefully in the near future , we can use the femtosecond laser and perform both donor and recipient corneal lamellar dissection .
 purposeto report two cases of femtosecond laser - assisted small incision deep lamellar endothelial keratoplasty ( dlek ) for patients with corneal endothelial decompensation by fuchs dystrophy and glaucomamethodsfemtosecond laser ( intralase ; intralase corp . , 
 irvine , ca ) with 15 khz of repetition rate , was used for a 9.5 mm diameter by 400 m thickness donor corneal lamellar dissection.resultsin case 1 , the graft was clear and compact without interface haze , orbscan showed smooth and regular corneal surface , specular microscopy was unremarkable without sign of corneal endothelial damage , and optical coherence tomography showed uniform graft well attached to recipient stroma with minimal interface reflection at 2 months postoperation . in case 2 , the graft was clear and compact with minimal interface haze at 1 month postoperation . 
 femtosecond laser - assisted small incision dlek was safe and technically feasible in our cases ; however , further evaluation is required to determine long - term effects . 
Purpose
Methods
Results
Case Report
Surgical Procedure
Case 1
Case 2
Discussion