Abstracts
Purpose:
To evaluate the efficacy and reliability of a low-energy femtosecond laser with a high repetition rate for construction of deep anterior donor corneal lamellae.
Methods:
This was a prospective laboratory investigation. Twenty-five human corneal buttons were femtosecond laser cut to create thick anterior lamellae (diameter, 10mm; thickness, 500µm). The laser cuts were made using an LDV® femtosecond laser in a Ziemer® anterior chamber. To obtain a better edge, the lamellae were trephined with an 8mm trephine (Katena®). The central corneal thickness and the anterior lamellae were measured using a Mitutoyo® thickness gauge with an accuracy of 0.001mm.
Results:
The central thickness of the 25 corneas ranged from 500 to 705µm (mean, 584 ± 51µm). The thickness of the anterior lamellae ranged from 420 to 480µm (mean, 455 ± 12.7µm). The anterior lamellae diameters were 7.90 ± 0.1mm, and all laser cuts were round. The lamellar interfaces appeared regular by surgical microscopy. There were no cases of inter-lamellar adhesion.
Conclusion:
The LDV® femtosecond laser appears to be a safe and reliable instrument for cutting deep anterior lamellae from donor corneoscleral buttons. Minimal variation in donor lamellar depth with the laser will be useful for creating donor corneal tissue for deeper anterior lamellar keratoplasty or endothelial keratoplasty surgery or both from a single donor cornea.
Cornea; Corneal transplantation; Corneal pachymetry; Endothelium; Lasers
Objetivo:
Avaliar a eficácia e segurança de um laser de femtossegundo de baixa energia e alta taxa de repetição para confecção de lamelas corneanas doadoras anteriores profundas.
Métodos:
Este é um estudo prospectivo de investigação laboratorial. Vinte e cinco botões corneanos foram cortados com laser de femtossegundo para criar lamelas corneanas doadoras anteriores profundas (diâmetro, 10mm; espessura, 500µm). O corte a laser foi realizado com femtosecond laser LDV® na câmara anterior artificial da Ziemer®. Para obter-se uma melhor borda, as lamelas foram trepanadas com um trépano de 8mm da Katena®. A paquimetria corneana central e as lamelas anteriores foram aferidas utilizando o paquímetro Mitutoyo®, com acurácia de 0.001mm.
Resultados:
A paquimetria central das 25 córneas variou de 500 a 705µm (média de 584 ± 51µm). A espessura das lamelas anteriores variou de 420 a 480µm (media de 455 ± 12.7µm). O diâmetro das lamelas corneanas doadoras foi 7.90 ± 0,1mm, sendo todos os cortes redondos. As interfaces lamelares apresentaram-se regular ao microscópio cirúrgico. Não houve casos de adesão interlamelar.
Conclusão:
O laser de femtossegundo LDV® mostrou-se seguro e eficaz para confeccionar lamelas corneanas doadoras a partir de botões córneo-esclerais. Mínima variação na espessura das lamelas doadoras confeccionadas com o laser será útil para criação de tecidos corneanos doadores para ceratoplastia lamelar anterior profunda ou ceratoplastia endoteliais, ou ambas, a partir de uma só córnea.
Córnea; Transplante de córnea; Paquimetria corneana; Lasers; Endotélio
INTRODUCTION
Improvements in instrumentation and surgical techniques have restored interest in deep
lamellar transplantation and endothelial keratoplasty(11. Reinhart WJ, Musch DC, Jacobs DS, Lee WB, Kaufman SC, Shtein RM. Deep
anterior lamellar keratoplasty as an alternative to penetrating keratoplasty a report
by the american academy of ophthalmology. Ophthalmology. 2011;118(1):209-18.
Review.). Important elements in this progress have been the use
of an artificial anterior chamber(22. Behrens A, Dolorico AM, Kara DT, Novick LH, McDonnell PJ, Chao LC, et
al. Precision and accuracy of an artificial anterior chamber system in obtaining
corneal lenticules for lamellar keratoplasty. J Cataract Refract Surg.
2001;27(10):1679-87.
3. Springs CL, Joseph MA, Odom JV, Wiley LA. Predictability of donor
lamellar graft diameter and thickness in an artificial anterior chamber system.
Cornea. 2002;21(7):696-9.
4. Victor G, Faria e Sousa SJ, Alves MR, Nosé W. [MALKS: specifications
and development].Arq Bras Oftalmol. 2006;69(2):151-5. Portuguese.-55. Victor G, Sousa SJ, Alves MR, Nosé W. Evaluation of a new system for
obtaining donor lamellar grafts. Cornea. 2007;26(2):151-3.), automated
microkeratome(66. Pallikaris IG, Papatzanaki ME, Stathi EZ, Frenschock O, Georgiadis A.
Laser in situ keratomileusis. Lasers Surg Med. 1990;10(5):463-8.
7. Buratto L, Ferrari M, Rama P. Excimer laser intrastromal
keratomileusis. Am J Ophthalmol. 1992;113(3):291-5.
8. Azar DT, Jain S, Sambursky R, Strauss L. Microkeratome-assisted
posterior keratoplasty. J Cataract Refract Surg. 2001;27(3):353-6.
9. Busin M, Zambianchi L, Arffa RC. Microkeratome-assisted lamellar
keratoplasty for the surgical treatment of keratoconus. Ophthalmology.
2005;112(6):987-97.
10. Kang PC, McEntire MW, Thompson CJ, Moshirfar M. Preparation of donor
lamellar tissue for deep lamellar endothelial keratoplasty using a microkeratome and
artificial anterior chamber system: endothelial cell loss and predictability of
lamellar thickness. Ophthalmic Surg Lasers Imaging.
2005;36(5):381-5.-1111. Behrens A, Ellis K, Li L, Sweet PM, Chuck RS. Endothelial lamellar
keratoplasty using an artificial anterior chamber and a microkeratome. Arch
Ophthalmol. 2003;121(4):503-8.), and both in
combination(22. Behrens A, Dolorico AM, Kara DT, Novick LH, McDonnell PJ, Chao LC, et
al. Precision and accuracy of an artificial anterior chamber system in obtaining
corneal lenticules for lamellar keratoplasty. J Cataract Refract Surg.
2001;27(10):1679-87.
3. Springs CL, Joseph MA, Odom JV, Wiley LA. Predictability of donor
lamellar graft diameter and thickness in an artificial anterior chamber system.
Cornea. 2002;21(7):696-9.
4. Victor G, Faria e Sousa SJ, Alves MR, Nosé W. [MALKS: specifications
and development].Arq Bras Oftalmol. 2006;69(2):151-5. Portuguese.-55. Victor G, Sousa SJ, Alves MR, Nosé W. Evaluation of a new system for
obtaining donor lamellar grafts. Cornea. 2007;26(2):151-3.,1212. Maguen E, Azen SP, Pinhas S, Villaseñor RA, Nesburn AB. Evaluation
of sources of variation on the accuracy and reproducibility of microkeratome sections
with the modified artificial anterior chamber. Ophthalmic Surg.
1982;13(3):217-20.). This was an important technical advance, since cutting
irregularities have been considered a major impediment to the visual outcome of lamellar
transplantation(1010. Kang PC, McEntire MW, Thompson CJ, Moshirfar M. Preparation of donor
lamellar tissue for deep lamellar endothelial keratoplasty using a microkeratome and
artificial anterior chamber system: endothelial cell loss and predictability of
lamellar thickness. Ophthalmic Surg Lasers Imaging.
2005;36(5):381-5.,1111. Behrens A, Ellis K, Li L, Sweet PM, Chuck RS. Endothelial lamellar
keratoplasty using an artificial anterior chamber and a microkeratome. Arch
Ophthalmol. 2003;121(4):503-8.). However, one disadvantage of
mechanical microkeratomes is the unpredictable depth of cut(1313. Thiel MA, Kaufmann C, Dedes W, Bochmann F, Becht CN, Schipper I.
Predictability of microkeratome-dependent flap thickness for DSAEK. Klin Monbl
Augenheilkd. 2009;226(4):230-3.). This is a major consideration in
transplantations where the endothelium is accompanied by a thin layer of the posterior
stroma, as in Descemet stripping automated endothelial keratoplasty (DSAEK). The
thickness of the posterior layer is ultimately determined by the thickness of the
anterior layer, cut by the microkeratome.
If the principal reason for microkeratome depth cut variability is the result of
interactions between the corneal substance and mechanical characteristics of the cutting
blade (sharpness, inclination, distance from applanation platform, and velocity), the
ability to alter this variance are small. Hence, the consideration of the femtosecond
laser keratome. This laser delivers pulses of infrared radiation into the tissue while
the pulse energy and interval varies with the brand. The tissue is ablated and cleaved
with minimal heating, leaving in place parallel rows of microcavities through the
process of photodisruption. These cavities define the plane of cleavage and the ensuing
cut is thus more accurate, homogeneous, and replicable than a mechanical
cut(1414. Lubatschowski H. Overview of commercially available femtosecond
lasers in refractive surgery. J Refract Surg. 2008;24(1):S102-7.
15. Santhiago MR, Wilson SE. Cellular effects after laser in situ
keratomileusis flap formation with femtosecond lasers: a review. Cornea.
2012;31(2):198-205. Review.
16. Salomão MQ, Wilson SE. Femtosecond laser in laser in situ
keratomileusis. J Cataract Refract Surg. 2010;36(6):1024-32. Review.-1717. Ahn H, Kim JK, Kim CK, Han GH, Seo KY, Kim EK, et al. Comparison of
laser in situ keratomileusis flaps created by 3 femtosecond lasers and a
microkeratome. J Cataract Refract Surg. 2011;37(2):349-57.).
Femtosecond lasers are divided into two groups: those with high energy and low frequency
firing (ex. IntraLase®, Abbott Medical Optics, Illinois, USA and Perfect
Vision®, Bausch&Lomb, München, Germany), and those with low energy and
high frequency of firing (LDV®, Ziemer® Ophthalmic System AG,
Port, Switzerland and Visumax®, Carl Zeiss Meditec AG, Berlin,
Germany)(1414. Lubatschowski H. Overview of commercially available femtosecond
lasers in refractive surgery. J Refract Surg. 2008;24(1):S102-7.
15. Santhiago MR, Wilson SE. Cellular effects after laser in situ
keratomileusis flap formation with femtosecond lasers: a review. Cornea.
2012;31(2):198-205. Review.
16. Salomão MQ, Wilson SE. Femtosecond laser in laser in situ
keratomileusis. J Cataract Refract Surg. 2010;36(6):1024-32. Review.
17. Ahn H, Kim JK, Kim CK, Han GH, Seo KY, Kim EK, et al. Comparison of
laser in situ keratomileusis flaps created by 3 femtosecond lasers and a
microkeratome. J Cataract Refract Surg. 2011;37(2):349-57.
18. de Medeiros FW, Kaur H, Agrawal V, Chaurasia SS, Hammel J, Dupps WJ
Jr, et al. Effect of femtosecond laser energy level on corneal stromal cell death and
inflammation. J Refract Surg. 2009;25(10):869-74.-1919. Moshirfar M, Gardiner JP, Schliesser JA, Espandar L, Feiz V, Mifflin
MD, et al. Laser in situ keratomileusis flap complications using mechanical
microkeratome versus femtosecond laser: retrospective comparison. J Cataract Refract
Surg. 2010;36(11):1925-33.). This second group of femtosecond
lasers tends to make smoother, more homogeneous, and replicable cuts than the first
group due to increased firing rate and the reduced size of cavitation(1414. Lubatschowski H. Overview of commercially available femtosecond
lasers in refractive surgery. J Refract Surg. 2008;24(1):S102-7.
15. Santhiago MR, Wilson SE. Cellular effects after laser in situ
keratomileusis flap formation with femtosecond lasers: a review. Cornea.
2012;31(2):198-205. Review.-1616. Salomão MQ, Wilson SE. Femtosecond laser in laser in situ
keratomileusis. J Cataract Refract Surg. 2010;36(6):1024-32. Review.). They also tend to cause less inflammation and cellular
necrosis due to the lower energy delivered(1414. Lubatschowski H. Overview of commercially available femtosecond
lasers in refractive surgery. J Refract Surg. 2008;24(1):S102-7.
15. Santhiago MR, Wilson SE. Cellular effects after laser in situ
keratomileusis flap formation with femtosecond lasers: a review. Cornea.
2012;31(2):198-205. Review.
16. Salomão MQ, Wilson SE. Femtosecond laser in laser in situ
keratomileusis. J Cataract Refract Surg. 2010;36(6):1024-32. Review.
17. Ahn H, Kim JK, Kim CK, Han GH, Seo KY, Kim EK, et al. Comparison of
laser in situ keratomileusis flaps created by 3 femtosecond lasers and a
microkeratome. J Cataract Refract Surg. 2011;37(2):349-57.
18. de Medeiros FW, Kaur H, Agrawal V, Chaurasia SS, Hammel J, Dupps WJ
Jr, et al. Effect of femtosecond laser energy level on corneal stromal cell death and
inflammation. J Refract Surg. 2009;25(10):869-74.-1919. Moshirfar M, Gardiner JP, Schliesser JA, Espandar L, Feiz V, Mifflin
MD, et al. Laser in situ keratomileusis flap complications using mechanical
microkeratome versus femtosecond laser: retrospective comparison. J Cataract Refract
Surg. 2010;36(11):1925-33.).
Therefore, theoretically, they are the best alternative to mechanical microkeratomes.
The objective of this study was to evaluate the efficacy and reliability of a low
energy-high repetition rate femtosecond laser keratome in the construction of deep
anterior corneal lamellae.
Materials and methods
The ethics committee of Universidade de São Paulo, School of Medicine approved this prospective and laboratory investigation. Twenty-five human corneal buttons were cut to produce deep anterior lamellae. The corneal tissue was procured from eyes having failed eye-bank serological tests. The anterior lamellae parameters were 10mm in diameter and 500µm in thickness. The cuts were carried out using an LDV® femtosecond laser (classic model). The pulse frequency of this laser operates in the megahertz range with high-aperture optics, a time exposure per pulse of 200-300 femtoseconds, and a spot diameter of 2µm. The shots were overlapped to avoid leaving areas without treatment. The energy per pulse was 30 nJ(1414. Lubatschowski H. Overview of commercially available femtosecond lasers in refractive surgery. J Refract Surg. 2008;24(1):S102-7.,1515. Santhiago MR, Wilson SE. Cellular effects after laser in situ keratomileusis flap formation with femtosecond lasers: a review. Cornea. 2012;31(2):198-205. Review.,2020. Ziemer FEMTO LDV Operator manual. Document No. FL5910-000-0046-32.). The time of construction for each anterior lamellae was approximately 50 seconds. All surgeries were performed at the Eye Clinic Day Hospital, São Paulo, SP, Brazil.
To construct the deep anterior corneal lamellae with the femtosecond laser, the corneas were first attached to the Ziemer® anterior chamber and then flattened using the head of the keratome. After completion of the laser treatment, the corneas were manually trephined from the endothelial side using an 8mm trephine blade (Katena® Products, Denville, NJ, USA). Next, the anterior and posterior lamellae were separated by holding the edge of the posterior cornea lamella with forceps and gently sliding the anterior corneal lamella by using the tip of a Merocel® (Medtronic®, Connecticut, USA) sponge.
The central corneal thickness and the anterior lamellae were measured with a mechanical thickness gauge with accuracy of 0.001mm using a 2110S-10 Mitutoyo® (Mitutoyo®, São Paulo, Brazil) (figure 1). Each measurement was determined from the average of three readings. The diameter of each lamella was measured with a strabismus caliper. The features of the lamellar interface were examined under a surgical microscope. Differences between the observed and expected measurements were analyzed using the Bland-Altman method(2121. Bland JM, Altman DG. Measuring agreement in method comparison studies. Stat Methods Med Res. 1999;8(2):135-60. Review.).
Mitutoyo® (Mitutoyo®, São Paulo, Brazil) 2110S-10 thickness gauge, with an accuracy of 0.001mm
The ethics committee of Universidade de São Paulo School of Medicine approved this prospective and laboratory investigation (study nº 242/11, approved on 06/22/2011).
RESULTS
The central thickness of the twenty-five whole corneas ranged from 500 to 705µm (mean, 584 ± 51µm), while the thickness of the anterior lamellae ranged from 420 to 480µm (mean, 455 ± 12.7µm). For each lamella that was cut, differences in central thickness between the observed and expected values were noted.The distribution of these differences is shown in table 1 and figure 2.
Analysis of the difference between observed and expected anterior lamella thickness obtained from an LDV® femtosecond laser adjusted to cuts 500μm in depth
Differences between the observed and expected thickness of the anterior lamellae cut by the LDV® femtosecond laser
Since the differences between the observed and expected lamellae thickness were normally distributed (Shapiro-Wilk Wtest; Prob<W=0.1280), 95% of them were within two standard deviations (s) of the mean (d). In figure 1, (d) + 2s is the upper limit of agreement while (d) - 2s is the lower limit of agreement. figure 1 also shows a linear regression of these data. The fact that this regression line is almost parallel to the x-axis suggests that the differences were not influenced by the magnitude of corneal thickness (r2=0.002658, Prob>F=0.8067). This qualifies (d) as a consistent bias that can be neutralized by adjustments to the cutting depth of the instrument. Provided this is done, the remaining differences represent the random error of the method which is about ± 2s.
Regarding the diameter of the lamellae, there were no discrepancies between the observed and expected measurements. All cuts were round, with 7,90 ± 0,1mm diameter. The lamellar interfaces appeared regular by surgical microscopy. There were no cases of inter-lamellar adhesion. Figure 3 shows corneal lamellae separation.
DISCUSSION
Historically, full-thickness penetrating keratoplasty has been the mainstay of therapy to address most forms of stromal and endothelial corneal pathology. However, over the past decade, there has been significant progress in performing site-specific corneal surgery such as endothelial keratoplasty and anterior lamellar keratoplasty. Interest in refining these procedures and improving surgical techniques has ensued. The application of fem to second laser in these procedures is being explored(2222. Rousseau A, Bensalem A, Garnier V, Savoldelli M, Saragoussi JJ, Renard G, et al. Interface quality of endothelial keratoplasty buttons obtained with optimised femtosecond laser settings. Br J Ophthalmol. 2012;96(1):122-7.,2323. Mehta JS, Shilbayeh R, Por YM, Cajucom-Uy H, Beuerman RW, Tan DT. Femtosecond laser creation of donor cornea buttons for Descemetstripping endothelial keratoplasty. J Cataract Refract Surg. 2008;34(11):1970-5.). This study evaluated the use of the the LDV® femtosecond laser for constructing deep anterior lamellae from donor corneoscleral buttons.
Several points should be highlighted in this study. Mechanical rather than ultrasound pachymetry was used in this study. Mitutoyo® micrometer measurements was comparable with Sonogage® ultrasonic pachymeter(2424. Weitkamp JW, Marsden HJ, Berke W, Daijo G. Agreement and repeatability of the Sonogage ultrasound pachometer compared with a Mitutoyo micrometer. Optom Vis Sci. 2008;85(5):359-63.), the only ultrasonic pachymeter capable of measuring epithelial thickness beyond total cornea thickness, then it can improved the accuracy of the measurements.
Using the LDV® femtosecond laser, a deep cut generates a thick anterior lamella and a thin posterior lamella. In our experience, using available resources of ultrasonic pachymetry for corneal buttons leads to poor performance when the lamellae are less than 150µm thick and has, frequently, more than 10µm of standard deviation. For this reason, all measurements were done on the anterior lamellae and whole corneas. Usually, the thickness of the posterior lamella is obtained by subtracting the former from the latter. The drawback to this approach is that the value of the posterior lamella is simultaneously corrupted by the measurement errors for the whole cornea and anterior lamella. Hence, the use of posterior lamellar thickness to assess the performance of keratomes is problematic, even if actually measured with an ultrasonic pachymeter. This is because current ultrasonic pachymeters are not well-suited for measuring thin lamellae, and, even more importantly, because the total error would always be the sum of the errors generated by two components: the whole cornea and the lamella. This is probably why the literature does not show good predictability for the residual stromal bed, based on preoperative measurements(2222. Rousseau A, Bensalem A, Garnier V, Savoldelli M, Saragoussi JJ, Renard G, et al. Interface quality of endothelial keratoplasty buttons obtained with optimised femtosecond laser settings. Br J Ophthalmol. 2012;96(1):122-7.,2323. Mehta JS, Shilbayeh R, Por YM, Cajucom-Uy H, Beuerman RW, Tan DT. Femtosecond laser creation of donor cornea buttons for Descemetstripping endothelial keratoplasty. J Cataract Refract Surg. 2008;34(11):1970-5.). To work appropriately with the least variability, the cut depth would have to be set from the endothelial side.
In a study(2525. Jones YJ, Goins KM, Sutphin JE, Mullins R, Skeie JM. Comparison of the femtosecond laser (IntraLase) versus manual microkeratome (Moria ALTK) in dissection of the donor in endothelial keratoplasty: initial study in eye bank eyes. Cornea. 2008;27(1):88-93.) comparing manual microkeratome (Moria® ALTK) versus a femtosecond laser (Intralase® to create a precut donnor lamellae, the femtosecond laser was more accurate than microkeratome. Programmed to cut 400 µm donnor lamellae, it cut 400 ± 41µm, while the microkeratome was programmed to cut 350µm, and did 446 ± 25µm. But were 8 eyes in each group. Other study(2626. Suwan-Apichon O, Reyes JM, Griffin NB, Barker J, Gore P, Chuck RS. Microkeratome versus femtosecond laser predissection of corneal grafts for anterior and posterior lamellar keratoplasty. Cornea. 2006;25(8):966-8.) made the same comparison (same equipament than study(2525. Jones YJ, Goins KM, Sutphin JE, Mullins R, Skeie JM. Comparison of the femtosecond laser (IntraLase) versus manual microkeratome (Moria ALTK) in dissection of the donor in endothelial keratoplasty: initial study in eye bank eyes. Cornea. 2008;27(1):88-93.) with programming donor lamella thickness of 350µm. The microkeratome group cut 361 ± 68µm, and the femtosecond laser group did 324 ± 112µm. But, were 5 eyes in each group. Both studies use US pachymetry. The present study shows lower standard deviation than those.
In our sample, about 95% of the measurements of the anterior lamellae were 71 to 19µm less than expected. The mean difference (d) was -45µm. There are three reasons why this femtosecond mean error (bias) was -45µm: 1) because of pachymetric errors, 2) because a safety margin of the company, or 3) combination of both.
The safety margin is a systematic error to the effective value of cut to be less than the programmed value, in order to increase the safety limit of cutting depth. If the average of effective depth of cut of the femtosecond laser coincide with the average programmed value, surely half the normal random error would be greater than it, and may exceed the safety limit, in borderline cases. So, in planning the thickness of the residual bed for DSAEK, the surgeon has to consider four variables: the thickness of the whole cornea, the error in the corneal measurement, the thickness of the anterior lamella, and the error in its measurement. At present this is not an easy task, mostly due to the lack of reliable ultrasonic pachymetry for corneal lamellae.
The problem with the above reasoning is that it may apply only to the present sample. A second sample would give a different mean and different limit of agreement. The important question is how these differences would look for the general population. That is where the confidence intervals of the mean and of the upper and lower limits of agreement are helpful (table 1). The logic of the confidence intervals for the limits of agreement is exactly the same as for the mean. The only difference is that all possible combinations of the upper and lower limits should be considered to construct the agreement intervals. For example, in the worst-case scenario, the difference between the observed and expected anterior lamellae thicknesses would range from -77 to -13µm.
At least theoretically, the interactions between the corneal substance and laser beam should be significantly smaller than that expected for the metal blade of a mechanical keratome. It is conceivable that most cutting errors are in reality errors of pachymetry. If this is true, the accuracy of this method could be greatly improved by upgrading the technology of pachymetry.
In summary, the LDV® femtosecond laser seems to be a safe and reliable instrument for constructing deep anterior lamellae from donor corneoscleral buttons.
This study was support by the Fundação de Amparo 'a Pesquisa do Estado de São Paulo - FAPESP - São Paulo (SP), Brazil, process number 2011/14699-0.
REFERENCES
-
1Reinhart WJ, Musch DC, Jacobs DS, Lee WB, Kaufman SC, Shtein RM. Deep anterior lamellar keratoplasty as an alternative to penetrating keratoplasty a report by the american academy of ophthalmology. Ophthalmology. 2011;118(1):209-18. Review.
-
2Behrens A, Dolorico AM, Kara DT, Novick LH, McDonnell PJ, Chao LC, et al. Precision and accuracy of an artificial anterior chamber system in obtaining corneal lenticules for lamellar keratoplasty. J Cataract Refract Surg. 2001;27(10):1679-87.
-
3Springs CL, Joseph MA, Odom JV, Wiley LA. Predictability of donor lamellar graft diameter and thickness in an artificial anterior chamber system. Cornea. 2002;21(7):696-9.
-
4Victor G, Faria e Sousa SJ, Alves MR, Nosé W. [MALKS: specifications and development].Arq Bras Oftalmol. 2006;69(2):151-5. Portuguese.
-
5Victor G, Sousa SJ, Alves MR, Nosé W. Evaluation of a new system for obtaining donor lamellar grafts. Cornea. 2007;26(2):151-3.
-
6Pallikaris IG, Papatzanaki ME, Stathi EZ, Frenschock O, Georgiadis A. Laser in situ keratomileusis. Lasers Surg Med. 1990;10(5):463-8.
-
7Buratto L, Ferrari M, Rama P. Excimer laser intrastromal keratomileusis. Am J Ophthalmol. 1992;113(3):291-5.
-
8Azar DT, Jain S, Sambursky R, Strauss L. Microkeratome-assisted posterior keratoplasty. J Cataract Refract Surg. 2001;27(3):353-6.
-
9Busin M, Zambianchi L, Arffa RC. Microkeratome-assisted lamellar keratoplasty for the surgical treatment of keratoconus. Ophthalmology. 2005;112(6):987-97.
-
10Kang PC, McEntire MW, Thompson CJ, Moshirfar M. Preparation of donor lamellar tissue for deep lamellar endothelial keratoplasty using a microkeratome and artificial anterior chamber system: endothelial cell loss and predictability of lamellar thickness. Ophthalmic Surg Lasers Imaging. 2005;36(5):381-5.
-
11Behrens A, Ellis K, Li L, Sweet PM, Chuck RS. Endothelial lamellar keratoplasty using an artificial anterior chamber and a microkeratome. Arch Ophthalmol. 2003;121(4):503-8.
-
12Maguen E, Azen SP, Pinhas S, Villaseñor RA, Nesburn AB. Evaluation of sources of variation on the accuracy and reproducibility of microkeratome sections with the modified artificial anterior chamber. Ophthalmic Surg. 1982;13(3):217-20.
-
13Thiel MA, Kaufmann C, Dedes W, Bochmann F, Becht CN, Schipper I. Predictability of microkeratome-dependent flap thickness for DSAEK. Klin Monbl Augenheilkd. 2009;226(4):230-3.
-
14Lubatschowski H. Overview of commercially available femtosecond lasers in refractive surgery. J Refract Surg. 2008;24(1):S102-7.
-
15Santhiago MR, Wilson SE. Cellular effects after laser in situ keratomileusis flap formation with femtosecond lasers: a review. Cornea. 2012;31(2):198-205. Review.
-
16Salomão MQ, Wilson SE. Femtosecond laser in laser in situ keratomileusis. J Cataract Refract Surg. 2010;36(6):1024-32. Review.
-
17Ahn H, Kim JK, Kim CK, Han GH, Seo KY, Kim EK, et al. Comparison of laser in situ keratomileusis flaps created by 3 femtosecond lasers and a microkeratome. J Cataract Refract Surg. 2011;37(2):349-57.
-
18de Medeiros FW, Kaur H, Agrawal V, Chaurasia SS, Hammel J, Dupps WJ Jr, et al. Effect of femtosecond laser energy level on corneal stromal cell death and inflammation. J Refract Surg. 2009;25(10):869-74.
-
19Moshirfar M, Gardiner JP, Schliesser JA, Espandar L, Feiz V, Mifflin MD, et al. Laser in situ keratomileusis flap complications using mechanical microkeratome versus femtosecond laser: retrospective comparison. J Cataract Refract Surg. 2010;36(11):1925-33.
-
20Ziemer FEMTO LDV Operator manual. Document No. FL5910-000-0046-32.
-
21Bland JM, Altman DG. Measuring agreement in method comparison studies. Stat Methods Med Res. 1999;8(2):135-60. Review.
-
22Rousseau A, Bensalem A, Garnier V, Savoldelli M, Saragoussi JJ, Renard G, et al. Interface quality of endothelial keratoplasty buttons obtained with optimised femtosecond laser settings. Br J Ophthalmol. 2012;96(1):122-7.
-
23Mehta JS, Shilbayeh R, Por YM, Cajucom-Uy H, Beuerman RW, Tan DT. Femtosecond laser creation of donor cornea buttons for Descemetstripping endothelial keratoplasty. J Cataract Refract Surg. 2008;34(11):1970-5.
-
24Weitkamp JW, Marsden HJ, Berke W, Daijo G. Agreement and repeatability of the Sonogage ultrasound pachometer compared with a Mitutoyo micrometer. Optom Vis Sci. 2008;85(5):359-63.
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25Jones YJ, Goins KM, Sutphin JE, Mullins R, Skeie JM. Comparison of the femtosecond laser (IntraLase) versus manual microkeratome (Moria ALTK) in dissection of the donor in endothelial keratoplasty: initial study in eye bank eyes. Cornea. 2008;27(1):88-93.
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26Suwan-Apichon O, Reyes JM, Griffin NB, Barker J, Gore P, Chuck RS. Microkeratome versus femtosecond laser predissection of corneal grafts for anterior and posterior lamellar keratoplasty. Cornea. 2006;25(8):966-8.
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This study was support by the Foundation for Research Support of the State of Sao Paulo (FAPESP), www.fapesp.br (acknowledgment). The ethics committee of Universidade de São Paulo School of Medicine approved this prospective and laboratory investigation (study nº 242/11, approved on 06/22/2011)
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Errata
No artigo Victor G, Nosé W, Souza SJ, Pineda R, Alves MR. Analysis of low-energy and high-frequency femtosecond laser for the construction of deep anterior donor corneal lamellae. Rev Bras Oftalmol. 2014;73(2): 71-4, para afiliações leia-se:Gustavo Victor1, Walton Nosé2, Sidney Julio de Faria e Sousa3, Roberto Pineda4, Milton Ruiz Alves11 Department of Ophthalmology, Universidade de São Paulo, São Paulo, SP, Brazil;2 Department of Ophthalmology, Universidade Federal de São Paulo, São Paulo, SP, Brazil;3 Department of Ophthalmology, Universidade de São Paulo, Ribeirão Preto, Ribeirão Preto, SP, Brazil;4 Department of Ophthalmology, Harvard Medical School, Boston, MA. EUA.
Publication Dates
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Publication in this collection
Mar-Apr 2014
History
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Received
15 May 2013 -
Accepted
13 Dec 2013