The Effect of Haptic Feedback on Efficiency and Safety During Preretinal Membrane Peeling Simulation.

PurposeWe determine whether haptic feedback improves surgical performance and outcome during simulated a preretinal membrane peeling procedure.MethodsA haptic-enabled virtual reality preretinal membrane peeling simulator was developed using a surgical cockpit with two multifinger haptic devices. Six subjects (three trained retina surgeons and three nonsurgeons) performed the preretinal membrane peeling surgical procedure using two modes of operation: visual and haptic feedback, and visual feedback only.ResultsTask completion time, tool tip path trajectory, tool-retina collision force, and retinal damage were all reduced with haptic feedback used and compared to modes where haptic feedback was disabled.ConclusionsHaptic feedback improves efficiency and safety during preretinal membrane peeling simulation.Translational relevanceThese findings highlight the potential benefit of haptic feedback for improving performance and safety of vitreoretinal surgery

Semiautomated optical coherence tomography-guided robotic surgery for porcine lens removal.

PurposeTo evaluate semiautomated surgical lens extraction procedures using the optical coherence tomography (OCT)-integrated Intraocular Robotic Interventional Surgical System.SettingStein Eye Institute and Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, USA.DesignExperimental study.MethodsSemiautomated lens extraction was performed on postmortem pig eyes using a robotic platform integrated with an OCT imaging system. Lens extraction was performed using a series of automated steps including robot-to-eye alignment, irrigation/aspiration (I/A) handpiece insertion, anatomic modeling, surgical path planning, and I/A handpiece navigation. Intraoperative surgical supervision and human intervention were enabled by real-time OCT image feedback to the surgeon via a graphical user interface. Manual preparation of the pig-eye models, including the corneal incision and capsulorhexis, was performed by a trained cataract surgeon before the semiautomated lens extraction procedures. A scoring system was used to assess surgical complications in a postoperative evaluation.ResultsComplete lens extraction was achieved in 25 of 30 eyes. In the remaining 5 eyes, small lens pieces (≤1.0 mm3) were detected near the lens equator, where transpupillary OCT could not image. No posterior capsule rupture or corneal leakage occurred. The mean surgical duration was 277 seconds ± 42 (SD). Based on a 3-point scale (0 = no damage), damage to the iris was 0.33 ± 0.20, damage to the cornea was 1.47 ± 0.20 (due to tissue dehydration), and stress at the incision was 0.97 ± 0.11.ConclusionsNo posterior capsule rupture was reported. Complete lens removal was achieved in 25 trials without significant surgical complications. Refinements to the procedures are required before fully automated lens extraction can be realized

Bilateral Acquired Progressive Retinal Nerve Fiber Layer Myelination.

The authors present the multimodal imaging findings of an unusual case of bilateral acquired progressive myelination of the optic disc during a 10-year follow-up period in a hyperopic adolescent patient in the absence of an underlying ocular or systemic abnormality. Myelination of the left optic disc was noted at age 7 and of the right optic disc at age 13, but no other ocular or systemic abnormalities were identified. Cross-sectional optical coherence tomography (OCT) and en face OCT angiography confirmed the presence of myelination of the retinal nerve fiber layer and excluded other etiologic possibilities including an astrocytic hamartoma. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:e147-e150.]

Bilateral Acquired Progressive Retinal Nerve Fiber Layer Myelination

The authors present the multimodal imaging findings of an unusual case of bilateral acquired progressive myelination of the optic disc during a 10-year follow-up period in a hyperopic adolescent patient in the absence of an underlying ocular or systemic abnormality. Myelination of the left optic disc was noted at age 7 and of the right optic disc at age 13, but no other ocular or systemic abnormalities were identified. Cross-sectional optical coherence tomography (OCT) and en face OCT angiography confirmed the presence of myelination of the retinal nerve fiber layer and excluded other etiologic possibilities including an astrocytic hamartoma. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:e147-e150.]

The Effect of Haptic Feedback on Efficiency and Safety During Preretinal Membrane Peeling Simulation.

PurposeWe determine whether haptic feedback improves surgical performance and outcome during simulated a preretinal membrane peeling procedure.MethodsA haptic-enabled virtual reality preretinal membrane peeling simulator was developed using a surgical cockpit with two multifinger haptic devices. Six subjects (three trained retina surgeons and three nonsurgeons) performed the preretinal membrane peeling surgical procedure using two modes of operation: visual and haptic feedback, and visual feedback only.ResultsTask completion time, tool tip path trajectory, tool-retina collision force, and retinal damage were all reduced with haptic feedback used and compared to modes where haptic feedback was disabled.ConclusionsHaptic feedback improves efficiency and safety during preretinal membrane peeling simulation.Translational relevanceThese findings highlight the potential benefit of haptic feedback for improving performance and safety of vitreoretinal surgery

Effects of Collagenase type II on Vitreous Humor, an in-situ Rheological Study.

The purpose of this study is to quantify the impact of enzyme activity on the vitreous humor structure over time to understand the mechanical characteristics of the vitreous humor gel. Changes in the mechanical behavior of the vitreous occur to many reasons including aging, which may lead to many vitreoretinal diseases. The degeneration of the vitreous has been studied; however, in-situ experimental procedures to validate the existing hypotheses are limited. We examined thirty-eight porcine eyes using in-situ rheological creep tests to measure the mechanical properties of the vitreous humor of the eyes prior to, 1 and 24 hours after the intravitreal injection. Eyes in one group were injected with collagenase type II solution and eyes in the control group were injected with Phosphate Buffered Saline solution with calcium and magnesium chloride. Prior to the injection, viscosity and creep compliance intercept values between both groups were not statistically different. At 1 hour and 24 hours after the injection, vitreous properties in eyes from the first group showed a statistically significant increase in the J intercept (representing the inverse of elasticity) values compared with the control group. In addition, 1 and 24 hours after the injection, vitreous viscosity was lower in eyes from the first group than in eyes from the control group. These findings are a foundation for future studies on the effectiveness of intravitreal drugs to modify the mechanical properties of the vitreous humor

Evaluation of non-exudative microcystoid macular abnormalities secondary to retinal vein occlusion.

PurposeWe aimed to investigate non-exudative microcystoid macular abnormalities for visual and anatomical outcome in patients with retinal vein occlusion (RVO) with and without glaucomatous optic neuropathy (GON).MethodsMedical records of 124 eyes (105 patients) with RVO were reviewed and analyzed. Eyes demonstrating microcystoid macular abnormalities were divided into 2 groups, those with evidence of glaucoma (group A) and those without glaucoma (group B). Best-corrected visual acuity (BCVA), the prevalence and number of microcystoid macular abnormalities, and number of intravitreal anti-vascular endothelial growth factor (anti-VEGF) injections were compared at baseline and follow-up.ResultsSeventy-one out of 105 eyes (67.6%) with RVO displayed microcystoid macular abnormalities. Thirty-eight out of 71 eyes (53.5%) presented with concomitant glaucoma (group A), while the remaining 33 eyes (42.6%) had no history of glaucoma (group B). At the end of the follow-up period, mean BCVA was worse in group A versus group B (20/80 versus 20/40, respectively; p = .003). The mean number of anti-VEGF injections was 10.1 ± 9.2 in group A versus 5.9 ± 6.9 in group B (p = .03).ConclusionEyes with RVO and concomitant glaucoma exhibited a significantly higher number of microcystoid macular abnormalities and worse BCVA versus eyes with RVO without glaucoma

Retrospective comparative analysis of intraocular lens calculation formulas after hyperopic refractive surgery.

PURPOSE:To compare the intraocular lens calculation formulas and evaluate postoperative refractive results of patients with previous hyperopic corneal refractive surgery. DESIGN:Retrospective, comparative, observational study. SETTING:Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA. METHODS:Clinical charts and optical biometric data of 39 eyes from 24 consecutive patients diagnosed with previous hyperopic laser vision correction and cataract surgery were reviewed and analyzed. The Intraocular lens (IOL) power calculation using the Holladay 2 formula (Lenstar) and the American Society of Cataract and Refractive Surgery (ASCRS) Post-Refractive IOL Calculator (version 4.9, 2017) were compared to the actual manifest refractive spherical equivalent (MRSE) following cataract surgery. No pre-Lasik / PRK or post-Lasik / PRK information was used in any of the calculations. The IOL prediction error, the mean IOL prediction error, the median absolute refractive prediction error, and the percentages of eyes within ±0.50 diopter (D) and ±1.00 D of the predicted refraction were calculated. RESULTS:The Holladay 2 formula produced a mean arithmetic IOL prediction error significantly different from zero (P = 0.003). Surprisingly, the mean arithmetic IOL prediction errors generated by Shammas, Haigis-L and Barret True K No History formulas were not significantly different from zero (P = 0.14, P = 0.49, P = 0.81, respectively).There were no significant differences in the median absolute refractive prediction error or percentage of eyes within ± 0.50 D or ± 1.00 D of the predicted refraction between formulas or methods. CONCLUSION:In eyes with previous hyperopic LASIK/PRK and no prior data, there were no significant differences in the accuracy of IOL power calculation between the Holladay 2 formula and the ASCRS Post-refractive IOL calculator

Effects of Collagenase Type II on Vitreous Humor-An In Situ Rheological Study.

The purpose of this study is to quantify the impact of enzyme activity on the vitreous humor structure over time to understand the mechanical characteristics of the vitreous humor gel. Changes in the mechanical behavior of the vitreous occur due to many reasons including aging, which may lead to many vitreoretinal diseases. The degeneration process of the vitreous has been studied; however, in situ experimental procedures to validate the existing hypotheses are limited. We examined thirty-eight porcine eyes using in situ rheological creep tests to measure the mechanical properties of the vitreous humor of the eyes prior to, 1 h and 24 h after the intravitreal injection. Eyes in one group were injected with collagenase type II solution and eyes in the control group were injected with phosphate buffered saline solution (PBS) with calcium and magnesium chloride. Prior to the injection, viscosity and creep compliance intercept values between both groups were not statistically different. At 1 h and 24 h after the injection, vitreous properties in the eyes from the first group showed a statistically significant increase in the J intercept values (representing the inverse of elasticity) compared to the control group. In addition, 1 h and 24 h after the injection, vitreous viscosity was lower in the eyes from the first group than in the eyes from the control group. These findings are a foundation for future studies on the effectiveness of intravitreal drugs that modify the mechanical properties of the vitreous humor