Florence Cabot

Femtosecond laser-assisted cataract surgery.

Femtosecond laser-assisted cataract surgery provides surgeons an exciting new option to potentially improve patient outcomes and safety. Over the past 2 years, 4 unique laser platforms have been introduced into the marketplace. The introduction of this new technology has been accompanied by a host of new clinical, logistical, and financial challenges for surgeons. This article describes the evolution of femtosecond laser technology for use in cataract surgery. It reviews the available laser platforms and discusses the necessary modifications in cataract surgery technique and the logistics of incorporating a femtosecond laser into ones practice.

The Quality of Vision questionnaire: subscale interchangeability.

Purpose The purpose of this study is to evaluate the interchangeability of the three subscales of the Quality of Vision (QoV) questionnaire: Frequency, Severity and Bothersome. This will indicate if any of the subscales are predictive of one another and whether respondents need to complete all three subscales. Methods Data from four studies were pooled together, totaling 1930 completed questionnaires. Patient groups consisted of spectacle wearers, contact lens wearers, post–laser refractive surgery (including laser in situ keratomileusis, laser-assisted subepithelial keratectomy, and photorefractive keratectomy surgeries for various refractive errors), patients with cataract, and patients having undergone lens implantation surgery (consisting of monofocal, multifocal, and pseudoaccommodative intraocular lenses). The Bland-Altman limits of agreement (LoA) method was used to assess the interchangeability between the three subscales of the QoV questionnaire. Results The mean difference, standard deviation of the differences, and the LoA for the Frequency versus Severity subscale was 2.8570, 6.784, and −10.4397 to 16.1537, respectively. The mean difference, standard deviation of the differences, and the LoA for the Frequency versus Bothersome subscale was 5.4674, 12.5768, and −19.1831 to 30.1179, respectively. The mean difference, standard deviation of the differences, and the LoA for the Severity versus Bothersome subscale was 2.6104, 9.4444, and −15.9006 to 21.1213, respectively. Conclusions The wide LoA found in this study indicate that the three subscales of the QoV questionnaire (Frequency, Severity and Bothersome.) measure different aspects of the latent trait, quality of vision. Users should continue to use all three subscales of the questionnaire to achieve a comprehensive assessment of subjective quality of vision.

The use of Bowman's layer vertical topographic thickness map in the diagnosis of keratoconus.

PURPOSE To evaluate the use of Bowmans layer (BL) vertical topographic thickness maps in diagnosing keratoconus (KC). DESIGN Prospective, case control, interventional case series. PARTICIPANTS A total of 42 eyes: 22 eyes of 15 normal subjects and 20 eyes of 15 patients with KC. INTERVENTION Bowmans layer 2-dimensional 9-mm vertical topographic thickness maps were created using custom-made ultra high-resolution optical coherence tomography. MAIN OUTCOME MEASURES Bowmans layer average and minimum thicknesses of the inferior half of the cornea, Bowmans ectasia index (BEI; defined as BL minimum thickness of the inferior half of the cornea divided by BL average thickness of the superior half of the cornea multiplied by 100), BEI-Max (defined as BL minimum thickness of the inferior half of the cornea divided by BL maximum thickness of the superior half of the cornea multiplied by 100), keratometric astigmatism (Ast-K) of patients with KC, and average keratometric (Avg-K) readings. RESULTS In patients with KC, BL vertical thickness maps disclosed localized relative inferior thinning of the BL. Inferior BL average thickness (normal = 15±2, KC = 12±3 μm), inferior BL minimum thickness (normal = 13±2, KC = 7±3 μm), BEI (normal = 91±7, KC = 48±14), and BEI-Max (normal = 75±8; KC = 40±13) all showed highly significant differences in KC compared with normal subjects (P< 0.001). Receiver operating characteristic (ROC) curve analysis showed excellent predictive accuracy for BEI and BEI-Max with 100% sensitivity and specificity (area under the curve [AUC] of 1) with cutoff values of 80 and 60, respectively. The AUC of inferior BL average thickness and minimum thickness were 0.87 and 0.96 with a sensitivity of 80% and 93%, respectively, and a specificity of 93% and 93%, respectively. Inferior BL average thickness, inferior BL minimum thickness, BEI, and BEI-Max correlated highly to Ast-K (R = -0.72, -0.82, -0.84, and -0.82, respectively; P< 0.001) and to Avg-K (R = -0.62, P< 0.001; R = -0.59, P = 0.001; R = -0.60, P< 0.001; and R = -0.59, P = 0.001, respectively). CONCLUSIONS Bowmans layer vertical topographic thickness maps of patients with KC disclose characteristic localized relative inferior thinning. Inferior BL average thickness, inferior BL minimum thickness, BEI, and BEI-Max are qualitative and quantitative indices for the diagnosis of KC that accurately correlate with the severity of KC. In our pilot study, BEI and BEI-Max showed excellent accuracy, sensitivity, and specificity in the diagnosis of KC.

Comparison of IOL power calculation methods and intraoperative wavefront aberrometer in eyes after refractive surgery.

PURPOSE To compare preoperative methods for calculating intraocular lens (IOL) power versus the intraoperative wavefront aberrometer in eyes with a history of refractive surgery. METHODS A retrospective study of 46 eyes (33 patients) with previous refractive surgery that underwent subsequent cataract surgery was conducted. Suggested IOL power predicted by ORange intraoperative wavefront aberrometer (WaveTec Vision Systems, Inc., Aliso Viejo, CA) was compared to power predicted by the (1) SRK-T formula using keratometry and axial length measurements from the IOLMaster (Carl Zeiss Meditec, Dublin, CA), (2) average central keratometry (Avg K) from corneal topography, and (3) average IOL power predicted by the American Society of Cataract and Refractive Surgery (ASCRS) web site. No historical information was used for the calculations. IOL power required for emmetropia was back-calculated using manifest refraction and implanted IOL power after cataract surgery. RESULTS Mean age was 60 ± 7.9 years. Fifteen percent had a history of myopic photorefractive keratectomy (n = 7), 57% myopic LASIK (n = 26), 13% hyperopic LASIK (n = 6), and 22% radial keratectomy (RK) (n = 10). In 37% of cases, ORange predicted IOL power to within ±0.50 diopters (D) of emmetropia, compared to 30% for IOLMaster keratometry, 26% for Avg K, and 17% for ASCRS web site. In eyes after myopic treatment, ORange, IOLMaster, Avg K, and ASCRS web site predicted within ±0.50 D of emmetropia in 39%, 27%, 24%, and 18%, respectively, and within ±1.0 D in 60%, 39%, 39%, and 51%, respectively. In eyes after RK, ORange, Avg K, and ASCRS web site predicted to within ±0.50 D of emmetropia in 14% and the IOLMaster in 43% cases. CONCLUSIONS Although the ORange most often predicted to within ±0.5 D of emmetropia, no method was able to achieve this accuracy more than 50% of the time. Predictions for eyes after RK were worse than for other types of refractive procedures.

Surface quality of human corneal lenticules after SMILE assessed using environmental scanning electron microscopy.

PURPOSE To assess the cut quality of the anterior and posterior surfaces of intrastromal refractive lenticules removed during small incision lenticule extraction (SMILE). METHODS The VisuMax femtosecond laser (500 kHz; Carl Zeiss Meditec, Dublin, CA) was used to perform SMILE on 8 eyes of 5 individuals to correct only myopia (no cylinder). The cut energy index was 26 (equivalent to an energy of 130 nJ) with a 2.5 × 2.5 μm spot/track separation. The lenticule diameter was 6.5 mm with a minimum edge thickness of 15 μm and the cap diameter was 7.3 mm with an intended thickness of 120 μm. After laser treatment, the lenticule was loosened with a spatula and removed with forceps. The extracted lenticules were placed in 2% formalin and sent for imaging with an environmental scanning electron microscope. Images of the anterior and posterior surfaces of the lenticules were obtained at multiple magnifications (100×, 250×, and 500×). Surface quality was evaluated by an investigator who specializes in electron microscopy using three criteria: overall surface regularity, percent of surface irregularity, and position of irregular area. RESULTS Both the anterior and posterior surfaces of the extracted lenticules were smooth and absent of surface irregularities. The cut edges also appeared uniform. Jagged edges were seen in several images, but were clearly caused by the forceps during extraction. CONCLUSIONS Using the VisuMax laser to perform SMILE produces smooth cuts absent of surface irregularities.

Assessment of rose bengal versus riboflavin photodynamic therapy for inhibition of fungal keratitis isolates.

PURPOSE To compare the in vitro effect of rose bengal and riboflavin as photosensitizing agents for photodynamic therapy (PDT) on fungal isolates that are common causes of fungal keratitis. DESIGN Experimental study. METHODS Three isolates (Fusarium solani, Aspergillus fumigatus, Candida albicans) recovered from patients with confirmed fungal keratitis were used in the experiments. Isolates were grown on Sabouraud-Dextrose agar, swabbed, and prepared in suspension, and 1 mL aliquots were inoculated onto test plates in triplicate. Test plates were separated into 5 groups: Group 1, no treatment; Group 2, 0.1% rose bengal alone; Group 3, 518 nm irradiation alone; Group 4, riboflavin PDT (riboflavin + 375 nm irradiation); and Group 5, rose bengal PDT (rose bengal + 518 nm irradiation). Irradiation was performed over a circular area using either a green light-emitting diode (LED) array (peak wavelength: 518 nm) or an ultraviolet-A LED array (peak wavelength: 375 nm). Test plates were irradiated with an energy density of 5.4 J/cm(2). Later, plates were placed in a 30 C incubator and observed for growth. RESULTS Rose bengal-mediated PDT successfully inhibited the growth of all 3 fungal isolates in the irradiated area. All other groups exhibited unrestricted growth throughout the plate. CONCLUSIONS Rose bengal-mediated PDT successfully inhibited the growth of 3 types of fungi. No other experimental groups, including riboflavin-mediated PDT, had any inhibitory effect on the isolates. The results might be useful for the treatment of patients suffering from corneal infection.

Comparison of surgically induced astigmatism between femtosecond laser and manual clear corneal incisions for cataract surgery

Purpose To assess the surgically induced corneal astigmatism (SIA) introduced by femtosecond laser–assisted clear corneal incisions (CCIs) for cataract extraction and to compare it with the SIA of manually created CCIs. Setting Bascom Palmer Eye Institute, Miller School of Medicine, Miami, Florida, USA. Design Prospective nonrandomized comparative case series. Methods Eyes received femtosecond laser–assisted CCIs (Group 1) or manual CCIs (Group 2). The surgical plan included 1 primary and 1 secondary port; the sites of the incisions were the same in both groups and were diametrically opposed between the right eye and left eye. The SIA was assessed using the preoperative and 1‐month postoperative keratometric values obtained from corneal topography examinations. Results This study included 72 eyes of 68 patients with a mean age of 69.0 years ± 9.87 (SD) (range 36 to 90 years). Thirty‐six eyes received femtosecond laser–assisted CCIs (Group 1) and 36 received manual CCIs (Group 2). The mean preoperative topographic corneal astigmatism was −1.19 ± 0.68 diopters (D) (range 0 to 2.50 D) and −0.92 ± 0.63 D (range 0.10 to 2.45 D) for Group 1 and Group 2, respectively, whereas, 1 month after cataract surgery, it was −1.16 ± 0.63 D (range 0.20 to 2.57 D) and −0.95 ± 0.64 D (range 0.21 to 2.37 D), respectively. Multivariate vector analysis revealed no statistically significant difference between the 2 groups for preoperative astigmatism, postoperative astigmatism, and SIA (P > .05 for all comparisons between Group 1 and Group 2). Conclusion Femtosecond laser–assisted and manual corneal incisions for cataract surgery did not appear to significantly alter corneal astigmatism, whereas they showed comparable SIA. Financial Disclosure Drs. Yoo and Donaldson are speakers for and consultants to Alcon Surgical, Inc., and Abbott Medical Optics, Inc. No other author has a financial or proprietary interest in any material or method mentioned.

Calculation of Ophthalmic Viscoelastic Device–Induced Focus Shift During Femtosecond Laser–Assisted Cataract Surgery

PURPOSE To assess if a change in refractive index of the anterior chamber during femtosecond laser-assisted cataract surgery can affect the laser beam focus position. METHODS The index of refraction and chromatic dispersion of six ophthalmic viscoelastic devices (OVDs) was measured with an Abbe refractometer. Using the Gullstrand eye model, the index values were used to predict the error in the depth of a femtosecond laser cut when the anterior chamber is filled with OVD. Two sources of error produced by the change in refractive index were evaluated: the error in anterior capsule position measured with optical coherence tomography biometry and the shift in femtosecond laser beam focus depth. RESULTS The refractive indices of the OVDs measured ranged from 1.335 to 1.341 in the visible light (at 587 nm). The error in depth measurement of the refilled anterior chamber ranged from -5 to +7 μm. The OVD produced a shift of the femtosecond laser focus ranging from -1 to +6 μm. Replacement of the aqueous humor with OVDs with the densest compound produced a predicted error in cut depth of 13 μm anterior to the expected cut. CONCLUSIONS Our calculations show that the change in refractive index due to anterior chamber refilling does not sufficiently shift the laser beam focus position to cause the incomplete capsulotomies reported during femtosecond laser-assisted cataract surgery.

Persistent corneal opacity after descemet stripping automated endothelial keratoplasty suggesting inert material deposits into the interface

Purpose: To report a case of interface deposits after Descemet stripping automated endothelial keratoplasty (DSAEK) imaged by means of an electron microscope. Methods: An 88-year-old man was referred with a history of corneal edema resulting from pseudophakic bullous keratopathy. A DSAEK was performed on his left eye without complications; however, the follow-up examination revealed a well-attached graft with persistent interface opacities at the donor–recipient interface. The DSAEK was repeated in this eye 1 year after the first surgery because of these corneal opacities that interfered with his vision. Results: In the immediate postoperative period, the patient had adequate visual acuity with intact graft placement and a clear interface. Pathology and electron microscope analysis were performed on the removed endothelial graft, which revealed diffuse particles on the stromal surface of the endothelial graft. Conclusions: A repeated DSAEK procedure sufficiently removed this patients corneal opacities and improved the visual acuity. The opacity is believed to have occurred because of residual viscoelastic material, which was used to maintain anterior chamber volume during surgery. This solution must be thoroughly removed to avoid similar complications.

Effects of Femtosecond Laser-Assisted Cataract Pretreatment on Pupil Diameter: A Comparison Between Three Laser Platforms

PURPOSE To assess pupil diameter before and after femtosecond laser-assisted cataract surgery (FLACS) pretreatment and compare the outcomes of three laser platforms. METHODS This prospective observational case series included consecutive patients scheduled to undergo cataract extraction using FLACS between August 2013 and February 2015. All eyes received FLACS pretreatment using three laser platforms: LenSx (Alcon Laboratories, Inc., Fort Worth, TX), Catalys (Abbott Medical Optics Inc., Santa Ana, CA), and Victus (Bausch & Lomb, Inc., Rochester, NY). The same protocol for preoperative medical mydriasis was used for all patients, and pupil diameter was assessed immediately before and 3 minutes after FLACS using a surgical ruler. RESULTS A total of 198 eyes of 161 patients were included in the study. Mean pupillary miosis was 1.42 ± 1.26 mm for the LenSx, 0.66 ± 0.89 mm for the Catalys, and 0.14 ± 0.34 mm for the Victus groups. Furthermore, 8 of the 198 eyes (4.0%) demonstrated a pupil diameter of less than 5 mm after FLACS and 48 eyes (24.24%) demonstrated a pupil diameter of 6 mm or less. There was a statistically significant decrease in pupil diameter for all groups individually (P < .05). There was also a statistically significant difference among the three groups (P < .05), with LenSx inducing the highest degree of miosis, followed by Catalys, and finally Victus. A correlation between the pupil diameter before FLACS and degree of FLACS-induced miosis was demonstrated (P < .05), with larger pupil diameter before FLACS associated with greater miosis. CONCLUSIONS FLACS pretreatment seems to induce significant pupillary miosis with all laser platforms assessed in this study. The decrease in pupil diameter after FLACS reached clinical significance for cataract extraction (< 5 mm) in 4.0% of cases, whereas 20.2% of eyes demonstrated small pupil diameter (≤ 6 mm) after FLACS pretreatment.