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Femtosecond laser-assisted cataract incisions: Architectural stability and reproducibility
CORRESPONDENCE
Femtosecond laser-assisted cataract incisions: Architectural stability and reproducibility Samuel Masket, MD, Melvin Sarayba, MD, Teresa Ignacio, MD, Nicole Fram, MD There is considerable interest in the potential relationship between postoperative endophthalmitis and clear corneal tunnel incisions for cataract surgery.1–4 Earlier work from Ernest et al.5 clearly demonstrated that incisions that are square in surface architecture are significantly more resistant to deformation and leakage than those that are rectangular. The purpose of this preliminary investigation was to determine whether corneal tunnel incisions could be constructed with femtosecond laser technology and in a manner that would preclude deformation and leakage at any intraocular pressure (IOP). MATERIALS AND METHODS Cadaver eyes subjected to partial-thickness clear corneal tunnel incisions constructed with an IntraLase femtosecond laser (model 1, Abbott Medical Optics, Inc.) were studied. A 15 kHz femtosecond laser was used to create 90% thickness corneal incisions; 3.0 mm wide, single plane–angled incisions were generated using the side-cut feature of the laser system. Incision tunnel lengths of 1.0 mm, 1.5 mm, and 2.0 mm were constructed (Video; available at www.jcrsjournal.org). A standard ophthalmodynamometer (ODM) was used to simulate deformation of the eye, similar to patient rubbing, following surgery. Manometric elevation and reduction of IOP was used to test incision integrity and various levels of pressure as the ODM device was applied near the equator of the globe. Incisions were observed for wound leakage determined by Seidel testing with a dry fluorescein strip (Figure 1).
RESULTS At variable tunnel lengths, the 3.0 mm 1.0 mm incision leaked at all levels of external pressure by the ODM unit and at all levels of IOP. The 3.0 mm 1.5 mm incision leaked with less external pressure by the ODM device and at lower levels of IOP; as IOP was raised manometrically, the incision exhibited a reduced tendency for leakage. The 3.0 mm 2.0 mm incision did not leak at any IOP despite deformation by the ODM at full levels of indentation pressure (Table 1).
Figure 1. A: Ophthalmodynamometer. B: The ODM calibrated standardized force (arrow) applied to equator of globe to simulate eye rubbing or pushing on the eye following surgery.
difficult to control the length and architecture of the incision tract. India ink penetration studies6,7 suggest that corneal incisions are potentially physically unstable, allowing leakage from deformation of the eye (eye rubbing, forceful blinking) early after surgery. This pilot study addressed the feasibility of using the femtosecond laser to construct reproducible and stable corneal incisions. The study validates that the femtosecond laser, although originally approved for lamellar corneal surgery, could be adapted to generate corneal incisions for cataract surgery as it has been adapted for use in penetrating keratoplasty.8
Table 1. Leakage at all tunnel lengths and IOP levels. Tunnel Length (mm) 1.0
1.5
DISCUSSION Femtosecond laser–assisted cataract incisions may offer added stability and reproducibility in cataract wound construction. Currently, corneal tunnel incisions are generated with ultra-sharp blades in a single pass (with or without a precut groove), making it 1048
Q 2010 ASCRS and ESCRS Published by Elsevier Inc.
2.0
IOP (mm Hg)
ODM (mmHg)
5 10 20 5 10 20 5 10 20
Leaked at all levels
58 60 70 No leakage at any level
IOP Z intraocular pressure; ODM Z ophthalmodynamometer
0886-3350/$dsee front matter doi:10.1016/j.jcrs.2010.03.027
CORRESPONDENCE
Although we believe that the current study is the first to describe use of a femtosecond laser to produce cataract incisions,A certain limitations of the investigation must be recognized. First, this is a pilot study with a small sample size. Second, the behavior of cadaver eyes may not mimic the clinical situation, as corneal thickness increases postmortem and could produce confounding results. Future studies should address these limitations and include OCT incision morphology as well as wound architecture and consider a comparison of standard keratome and femtosecond laser– generated corneal incisions. REFERENCES 1. Masket S. Is there a relationship between clear corneal cataract incisions and endophthalmitis? [guest editorial]. J Cataract Refract Surg 2005; 31:643–645 2. Cooper BA, Holekamp NM, Bohigian G, Thompson PA. Casecontrol study of endophthalmitis after cataract surgery comparing scleral tunnel and clear corneal wounds. Am J Ophthalmol 2003; 136:300–305 3. Nagaki Y, Hayasaka S, Kadoi C, Matsumoto M, Yanagisawa S, Watanabe K, Watanabe K, Hayasaka Y, Ikeda N, Sato S, Kataoka Y, Togashi M, Abe T. Bacterial endophthalmitis after small-incision cataract surgery; effect of incision placement and intraocular lens type. J Cataract Refract Surg 2003; 29:20–26 4. Wallin T, Parker J, Jin Y, Kefalopoulos G, Olson RJ. Cohort study of 27 cases of endophthalmitis at a single institution. J Cataract Refract Surg 2005; 31:735–741 5. Ernest PH, Kiessling LA, Lavery KT. Relative strength of cataract incisions in cadaver eyes. J Cataract Refract Surg 1991; 17:668–671 6. McDonnell PJ, Taban M, Sarayba MA, Rao B, Zhang J, Schiffman R, Chen Z. Dynamic morphology of clear corneal cataract incisions. Ophthalmology 2003; 110:2342–2348. Available at: http://chen.bli.uci.edu/publications/J50_Ophthalmology2003.pdf. pdf. Accessed February 20, 2010 7. Sarayba MA, Taban M, Ignacio T, Berens A, McDonnell PJ. Inflow of ocular surface fluid through clear corneal cataract incisions: a laboratory model. Am J Ophthalmol 2004; 138:206–210 8. Steinert RF, Ignacio TS, Sarayba MA. ‘‘Top hat’’–shaped penetrating keratoplasty using the femtosecond laser. Am J Ophthalmol 2007; 143:689–691
OTHER CITED MATERIAL A. Masket S. Use of the Intralase femtosecond laser for clear corneal cataract incisions. Presented at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, Washington, DC, USA, April 2005
Comparative effects of besifloxacin and other fluoroquinolones on corneal reepithelialization in the rabbit Jin-Zhong Zhang, PhD, Kathleen L. Krenzer, OD, PhD, Francisco J. Lo´pez, MD, PhD, Keith W. Ward, PhD Besifloxacin ophthalmic suspension 0.6% (Besivance), a newly approved fluoroquinolone for the treatment of bacterial conjunctivitis,1 has wide-spectrum
1049
and potent in vitro activity against common ocular pathogens.2 Topically applied besifloxacin 0.6% has a prolonged residence time on the ocular surface and minimal systemic exposure.3,4 In 2 vehicle-controlled phase III clinical studies,5,6 patients receiving besifloxacin 0.6% experienced significantly higher rates of microbial eradication and clinical resolution of bacterial conjunctivitis than patients receiving the vehicle control. Besifloxacin is designed to have a relatively balanced dual-targeting activity, blocking both DNA gyrase and topoisomerase IV, which suggests this drug may have a low incidence of bacterial resistance. This study investigated the effect of besifloxacin 0.6% on corneal reepithelialization in the rabbit. Three other topical ophthalmic fluoroquinolonesdlevofloxacin ophthalmic solution 1.5% (Iquix), moxifloxacin ophthalmic solution 0.5% (Vigamox), and gatifloxacin ophthalmic solution 0.3% (Zymar)dwere tested in parallel. Dexamethasone ophthalmic suspension 0.1% (Maxidex) was used to validate the model and serve as a positive control. Full-thickness corneal epithelial defects (9.5 mm in diameter) were created in the right eye of 10 New Zealand white rabbits.7 A drop of saline, besifloxacin, levofloxacin, gatifloxacin, moxifloxacin, or dexamethasone was applied to the eye 0.25, 0.50, 0.75, 1, 2, 3, 6, 12, 18, 24, 36, 48, 60, and 72 hours after surgery. Slitlamp photography was performed immediately after creation of the wound and staining by fluorescein and then after 12, 24, 36, 48, 60, and 72 hours. Images of the fluorescein-stained incisions were measured by planimetry, and the reepithelialization rate was determined. Dexamethasone significantly delayed corneal reepithelialization by 47% when the integrated response was compared with that in the saline control, indicating that this rabbit model can recapitulate the described effects of steroids on corneal reepithelialization. By 72 hours, most wounds in the saline and fluoroquinolone groups were completely reepithelialized (R95% of the cornea was reepithelialized compared with the 0-hour control) by clinical observation based on the lack of fluorescein staining, and no significant effects on corneal reepithelialization were observed with besifloxacin (Figure 1), gatifloxacin, moxifloxacin, or levofloxacin compared with those in the saline group at any time point. Integrated responses were also analyzed by calculating the areas under the curve for each treatment from 0 to 72 hours. No significant effects were seen when the effects with besifloxacin, gatifloxacin, moxifloxacin, and levofloxacin were compared with those in the saline group (Figure 2). The data in the present study demonstrate that in contrast to dexamethasone, which impedes corneal reepithelialization,8 besifloxacin as well as the other 3 fluoroquinolones did not alter the corneal
J CATARACT REFRACT SURG - VOL 36, JUNE 2010
Femtosecond laser-assisted cataract incisions: Architectural stability and reproducibility Samuel Masket, MD, Melvin Sarayba, MD, Teresa Ignacio, MD, Nicole Fram, MD There is considerable interest in the potential relationship between postoperative endophthalmitis and clear corneal tunnel incisions for cataract surgery.1–4 Earlier work from Ernest et al.5 clearly demonstrated that incisions that are square in surface architecture are significantly more resistant to deformation and leakage than those that are rectangular. The purpose of this preliminary investigation was to determine whether corneal tunnel incisions could be constructed with femtosecond laser technology and in a manner that would preclude deformation and leakage at any intraocular pressure (IOP). MATERIALS AND METHODS Cadaver eyes subjected to partial-thickness clear corneal tunnel incisions constructed with an IntraLase femtosecond laser (model 1, Abbott Medical Optics, Inc.) were studied. A 15 kHz femtosecond laser was used to create 90% thickness corneal incisions; 3.0 mm wide, single plane–angled incisions were generated using the side-cut feature of the laser system. Incision tunnel lengths of 1.0 mm, 1.5 mm, and 2.0 mm were constructed (Video; available at www.jcrsjournal.org). A standard ophthalmodynamometer (ODM) was used to simulate deformation of the eye, similar to patient rubbing, following surgery. Manometric elevation and reduction of IOP was used to test incision integrity and various levels of pressure as the ODM device was applied near the equator of the globe. Incisions were observed for wound leakage determined by Seidel testing with a dry fluorescein strip (Figure 1).
RESULTS At variable tunnel lengths, the 3.0 mm 1.0 mm incision leaked at all levels of external pressure by the ODM unit and at all levels of IOP. The 3.0 mm 1.5 mm incision leaked with less external pressure by the ODM device and at lower levels of IOP; as IOP was raised manometrically, the incision exhibited a reduced tendency for leakage. The 3.0 mm 2.0 mm incision did not leak at any IOP despite deformation by the ODM at full levels of indentation pressure (Table 1).
Figure 1. A: Ophthalmodynamometer. B: The ODM calibrated standardized force (arrow) applied to equator of globe to simulate eye rubbing or pushing on the eye following surgery.
difficult to control the length and architecture of the incision tract. India ink penetration studies6,7 suggest that corneal incisions are potentially physically unstable, allowing leakage from deformation of the eye (eye rubbing, forceful blinking) early after surgery. This pilot study addressed the feasibility of using the femtosecond laser to construct reproducible and stable corneal incisions. The study validates that the femtosecond laser, although originally approved for lamellar corneal surgery, could be adapted to generate corneal incisions for cataract surgery as it has been adapted for use in penetrating keratoplasty.8
Table 1. Leakage at all tunnel lengths and IOP levels. Tunnel Length (mm) 1.0
1.5
DISCUSSION Femtosecond laser–assisted cataract incisions may offer added stability and reproducibility in cataract wound construction. Currently, corneal tunnel incisions are generated with ultra-sharp blades in a single pass (with or without a precut groove), making it 1048
Q 2010 ASCRS and ESCRS Published by Elsevier Inc.
2.0
IOP (mm Hg)
ODM (mmHg)
5 10 20 5 10 20 5 10 20
Leaked at all levels
58 60 70 No leakage at any level
IOP Z intraocular pressure; ODM Z ophthalmodynamometer
0886-3350/$dsee front matter doi:10.1016/j.jcrs.2010.03.027
CORRESPONDENCE
Although we believe that the current study is the first to describe use of a femtosecond laser to produce cataract incisions,A certain limitations of the investigation must be recognized. First, this is a pilot study with a small sample size. Second, the behavior of cadaver eyes may not mimic the clinical situation, as corneal thickness increases postmortem and could produce confounding results. Future studies should address these limitations and include OCT incision morphology as well as wound architecture and consider a comparison of standard keratome and femtosecond laser– generated corneal incisions. REFERENCES 1. Masket S. Is there a relationship between clear corneal cataract incisions and endophthalmitis? [guest editorial]. J Cataract Refract Surg 2005; 31:643–645 2. Cooper BA, Holekamp NM, Bohigian G, Thompson PA. Casecontrol study of endophthalmitis after cataract surgery comparing scleral tunnel and clear corneal wounds. Am J Ophthalmol 2003; 136:300–305 3. Nagaki Y, Hayasaka S, Kadoi C, Matsumoto M, Yanagisawa S, Watanabe K, Watanabe K, Hayasaka Y, Ikeda N, Sato S, Kataoka Y, Togashi M, Abe T. Bacterial endophthalmitis after small-incision cataract surgery; effect of incision placement and intraocular lens type. J Cataract Refract Surg 2003; 29:20–26 4. Wallin T, Parker J, Jin Y, Kefalopoulos G, Olson RJ. Cohort study of 27 cases of endophthalmitis at a single institution. J Cataract Refract Surg 2005; 31:735–741 5. Ernest PH, Kiessling LA, Lavery KT. Relative strength of cataract incisions in cadaver eyes. J Cataract Refract Surg 1991; 17:668–671 6. McDonnell PJ, Taban M, Sarayba MA, Rao B, Zhang J, Schiffman R, Chen Z. Dynamic morphology of clear corneal cataract incisions. Ophthalmology 2003; 110:2342–2348. Available at: http://chen.bli.uci.edu/publications/J50_Ophthalmology2003.pdf. pdf. Accessed February 20, 2010 7. Sarayba MA, Taban M, Ignacio T, Berens A, McDonnell PJ. Inflow of ocular surface fluid through clear corneal cataract incisions: a laboratory model. Am J Ophthalmol 2004; 138:206–210 8. Steinert RF, Ignacio TS, Sarayba MA. ‘‘Top hat’’–shaped penetrating keratoplasty using the femtosecond laser. Am J Ophthalmol 2007; 143:689–691
OTHER CITED MATERIAL A. Masket S. Use of the Intralase femtosecond laser for clear corneal cataract incisions. Presented at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, Washington, DC, USA, April 2005
Comparative effects of besifloxacin and other fluoroquinolones on corneal reepithelialization in the rabbit Jin-Zhong Zhang, PhD, Kathleen L. Krenzer, OD, PhD, Francisco J. Lo´pez, MD, PhD, Keith W. Ward, PhD Besifloxacin ophthalmic suspension 0.6% (Besivance), a newly approved fluoroquinolone for the treatment of bacterial conjunctivitis,1 has wide-spectrum
1049
and potent in vitro activity against common ocular pathogens.2 Topically applied besifloxacin 0.6% has a prolonged residence time on the ocular surface and minimal systemic exposure.3,4 In 2 vehicle-controlled phase III clinical studies,5,6 patients receiving besifloxacin 0.6% experienced significantly higher rates of microbial eradication and clinical resolution of bacterial conjunctivitis than patients receiving the vehicle control. Besifloxacin is designed to have a relatively balanced dual-targeting activity, blocking both DNA gyrase and topoisomerase IV, which suggests this drug may have a low incidence of bacterial resistance. This study investigated the effect of besifloxacin 0.6% on corneal reepithelialization in the rabbit. Three other topical ophthalmic fluoroquinolonesdlevofloxacin ophthalmic solution 1.5% (Iquix), moxifloxacin ophthalmic solution 0.5% (Vigamox), and gatifloxacin ophthalmic solution 0.3% (Zymar)dwere tested in parallel. Dexamethasone ophthalmic suspension 0.1% (Maxidex) was used to validate the model and serve as a positive control. Full-thickness corneal epithelial defects (9.5 mm in diameter) were created in the right eye of 10 New Zealand white rabbits.7 A drop of saline, besifloxacin, levofloxacin, gatifloxacin, moxifloxacin, or dexamethasone was applied to the eye 0.25, 0.50, 0.75, 1, 2, 3, 6, 12, 18, 24, 36, 48, 60, and 72 hours after surgery. Slitlamp photography was performed immediately after creation of the wound and staining by fluorescein and then after 12, 24, 36, 48, 60, and 72 hours. Images of the fluorescein-stained incisions were measured by planimetry, and the reepithelialization rate was determined. Dexamethasone significantly delayed corneal reepithelialization by 47% when the integrated response was compared with that in the saline control, indicating that this rabbit model can recapitulate the described effects of steroids on corneal reepithelialization. By 72 hours, most wounds in the saline and fluoroquinolone groups were completely reepithelialized (R95% of the cornea was reepithelialized compared with the 0-hour control) by clinical observation based on the lack of fluorescein staining, and no significant effects on corneal reepithelialization were observed with besifloxacin (Figure 1), gatifloxacin, moxifloxacin, or levofloxacin compared with those in the saline group at any time point. Integrated responses were also analyzed by calculating the areas under the curve for each treatment from 0 to 72 hours. No significant effects were seen when the effects with besifloxacin, gatifloxacin, moxifloxacin, and levofloxacin were compared with those in the saline group (Figure 2). The data in the present study demonstrate that in contrast to dexamethasone, which impedes corneal reepithelialization,8 besifloxacin as well as the other 3 fluoroquinolones did not alter the corneal
J CATARACT REFRACT SURG - VOL 36, JUNE 2010