What is the impact of intraoperative microscope-integrated oct in ophthalmic surgery? Relevant applications and outcomes. a systematic review

Background: Optical coherence tomography (OCT) has recently been introduced in the operating theatre. The aim of this review is to present the actual role of microscope-integrated optical coherence tomography (MI-OCT) in ophthalmology. Method: A total of 314 studies were identified, following a literature search adhering to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. After full-text evaluation, 81 studies discussing MI-OCT applications in ophthalmology were included. Results: At present, three microscope-integrated optical coherence tomography systems are commercially available. MI-OCT can help anterior and posterior segment surgeons in the decision-making process, providing direct visualization of anatomic planes before and after surgical manoeuvres, assisting in complex cases, and detecting or confirming intraoperative complications. Applications range from corneal transplant to macular surgery, including cataract surgery, glaucoma surgery, paediatric examination, proliferative diabetic retinopathy surgery, and retinal detachment surgery. Conclusion: The use of MI-OCT in ophthalmic surgery is becoming increasingly prevalent and has been applied in almost all procedures. However, there are still limitations to be overcome and the technology involved remains difficult to access and use

Astigmatism and Pseudoaccommodation in Pseudophakic Eyes

noAdvanced IOLs with circumferential zones of different power provide pseudoaccommodation. We investigated the potential for power variation with meridian, namely astigmatism, to provide pseudo-accommodation. With appropriate power and axis orientations, acceptable pseudo-accommodation can be achieved

Depth-resolved full-field measurement of corneal deformation by optical coherence tomography and digital volume correlation

The study of vertebrate eye cornea is an interdisciplinary subject and the research on its mechanical properties has significant importance in ophthalmology. The measurement of depth-resolved 3D full-field deformation behaviour of cornea under changing intraocular pressure is a useful method to study the local corneal mechanical properties. In this work, optical coherence tomography was adopted to reconstruct the internal structure of a porcine cornea inflated from 15 to 18.75 mmHg (close to the physical porcine intraocular pressure) in the form of 3D image sequences. An effective method has been developed to correct the commonly seen refraction induced distortions in the optical coherence tomography reconstructions, based on Fermat’s principle. The 3D deformation field was then determined by performing digital volume correlation on these corrected 3D reconstructions. A simple finite element model of the inflation test was developed and the predicted values were compared against digital volume correlation results, showing good overall agreement

Ophthalmic engineering:the development of novel instrumentation to further research in the field

The principle theme of this thesis is the advancement and expansion of ophthalmic research via the collaboration between professional Engineers and professional Optometrists. The aim has been to develop new and novel approaches and solutions to contemporary problems in the field. The work is sub divided into three areas of investigation; 1) High technology systems, 2) Modification of current systems to increase functionality, and 3) Development of smaller more portable and cost effective systems. High Technology Systems: A novel high speed Optical Coherence Tomography (OCT) system with integrated simultaneous high speed photography was developed achieving better operational speed than is currently available commercially. The mechanical design of the system featured a novel 8 axis alignment system. A full set of capture, analysis, and post processing software was developed providing custom analysis systems for ophthalmic OCT imaging, expanding the current capabilities of the technology. A large clinical trial was undertaken to test the dynamics of contact lens edge interaction with the cornea in-vivo. The interaction between lens edge design, lens base curvature, post insertion times and edge positions was investigated. A novel method for correction of optical distortion when assessing lens indentation was also demonstrated. Modification of Current Systems: A commercial autorefractor, the WAM-5500, was modified with the addition of extra hardware and a custom software and firmware solution to produce a system that was capable of measuring dynamic accommodative response to various stimuli in real time. A novel software package to control the data capture process was developed allowing real time monitoring of data by the practitioner, adding considerable functionality of the instrument further to the standard system. The device was used to assess the accommodative response differences between subjects who had worn UV blocking contact lens for 5 years, verses a control group that had not worn UV blocking lenses. While the standard static measurement of accommodation showed no differences between the two groups, it was determined that the UV blocking group did show better accommodative rise and fall times (faster), thus demonstrating the benefits of the modification of this commercially available instrumentation. Portable and Cost effective Systems: A new instrument was developed to expand the capability of the now defunct Keeler Tearscope. A device was developed that provided a similar capability in allowing observation of the reflected mires from the tear film surface, but with the added advantage of being able to record the observations. The device was tested comparatively with the tearscope and other tear film break-up techniques, demonstrating its potential. In Conclusion: This work has successfully demonstrated the advantages of interdisciplinary research between engineering and ophthalmic research has provided new and novel instrumented solutions as well as having added to the sum of scientific understanding in the ophthalmic field

Femtosecond lasers in corneal and refractive surgery

Femtosecond lasers were introduced in ophthalmology initially for flap creation for LASIK. This thesis describes a body of work undertaken by the author exploring the possibility of using these lasers in corneal and refractive surgery. The use of the femtosecond laser in corneal and refractive surgery offered the prospect of better precision with respect to their accuracy in depth cut, and the smoothest of lamellar interface. The development of multiple laser platforms allowed us to perform comparative studies in both ex vivo/animal and clinical studies and to explore the prospect of a new refractive procedure, lenticule extraction and also lenticule re-implantation. The laser proved to be accurate in its vertical depth cutting and following optimization was able to cut a smoothe lamellar interface. The clinical study showed the laser to be safe and effective. The comparative studies showed the superiority of the lower energy femtosecond laser on IOP rise, without compromising on clinical outcomes, which were the same for both lasers. Femtosecond laser lenticule creation was optimised in animal models and then shown to be safe and efficacious in a clinical study. The wound healing benefits of an ‘all in one’ femtosecond laser procedure were evident, in both animal as well clinical studies. Lenticule reimplantation was shown to be effective in both the rabbit and monkey models. The use of the femtosecond laser is set to increase in ophthalmology. The work in this thesis has provided fundmental ex vivo, animal and clinical benefits on the the use of femtosecond lasers in corneal and refractive surgery. It has also envisioned a concept of lenticule re-implantation for future clinical use

NOVEL METHODS OF MERIDIONAL AND CIRCUMFERENTIAL ANTERIOR CHAMBER ANGLE IMAGING

Ph.DDOCTOR OF PHILOSOPH