Eye’s higher order aberrations in 2020. Was the target of 20/10 set too far from reality?
Population-wise, approximately 1 out of 1000 individuals achieves 20/10 vision (Decimal 2, LogMAR of 0.3). In the late nineties, mostly due to the advancements in measuring higher order aberration, a goal has been set for the majority of people, normally experiencing 20/20 vision (Decimal 1, LogMAR of 0.0), to achieve such high level of visual acuity by the year 2010. At that time, it was thought that customized refractive surgery or customized contact lenses, both treatments having the potential of correcting higher order aberrations, would provide the means for this advancement. However, the eye is not a static system that can be corrected statically (with glasses, contact lenses, or refractive surgery). Until we can apply dynamic vision correction outside laboratories, the dynamics of the human eye optics must be well understood to objectively determine the optimal static correction. More importantly, mere annulation of higher order aberrations in the eye is not the solution for achieving higher levels of visual acuity because some of the aberrations and their dynamics may have constructive rather than destructive character in the visual process.
The 1st Conference Ophthalmology Film and Photography Festival, Gdynia, August 30-31, 2019
What does the eye want to tell us?
The ocular pulse concerns a number of phenomena related to the expansion of the eyeball caused by fluctuations of intraocular pressure, pulsed blood flow in the ocular circulation, as well as longitudinal eye movements in the orbit. Until recently, measurement of eye pulsation was associated with highly specialized instrumentation such as Colour Doppler Imaging, or, in the case of corneal pulse, with prototypes such as the ultrasonography device developed at Wrocław University of Science and Technology (WUST) by the team of Monika Danielewska. A new technology, initiated in the United States at MIT and improved at WUST, based on the enhancement of motion in video films (called Video Motion Magnification), allows the registration of corneal pulse with a standard digital camera or telephone. The film, entitled “What does the eye want to tell us?” is a form of promotion of this new technology, which may in the future, be used in the diagnosis of glaucoma and characterization of eye pulsation in individuals suspected of glaucoma.
Physics of a human eye in XXI century
The human eye is not a static system, but a complicated, dynamic optical system in which we observe temporal changes of wavefront aberration caused by microfluctuations of the accommodation, pulsation of the eye or temporal changes of eye surface characteristics (e.g., tear film dynamics, corneal deformations). Despite the observed dynamics, the current correction of eyesight (with glasses, contact lenses, or refractive surgery) is static. Until we can apply dynamic vision correction outside laboratories, the dynamics of the human eye optics must be well understood to objectively determine the optimal static correction. That is why research on the dynamics of wavefront aberration in the human eye is important. On the other hand, it is worth considering whether a perfectly corrected optical system of the eye, for example, using adaptive optics, will be the best solution in the visual process. It is over 50 years that have passed since the work of Lohmann and Paris, who studied the effect of longitudinal vibrations in the ideal optical system (periodic changes of the position of the image with respect to the focus). Interestingly, they found that the integrated quality of an image placed outside the focus increases in the presence of a defocus vibration. The presence of such a mechanism in the eye has been speculated for years by the speaker. We have recently demonstrated experimentally that both simulated retinal image quality and experimentally measured visual acuity improve when defocus vibrations are added to an emmetropic eye. The seminar ended up with an open, debatable question: does the small defocus naturally occurring in the eye contribute to better vision?
VIII International Controversies in Ophthalmology.
Should the accompanying eye in patient with unilateral glaucoma be treated?
In most cases, the unilateral glaucoma is secondary and a careful systematic examination will help detect the reason for hypertension. However, the case of unilateral primary open angle glaucoma is not always obvious. When it comes to prevalence, as early as in 1972, Etienne (Brit. J. Ophthal. (1972) 56, 258) examined 1373 cases from which 289 (28%) were unilateral. However, only 2.3% were diagnosed as primary. This included 33 cases of chronic simple glaucoma; 12 cases of exfoliation and glaucoma and one case of pigmentary glaucoma. Etienne argued that if one accepts a hydrodynamic definition of glaucoma, unilateral glaucoma does not exist: there are only asymmetrical glaucomatous eyes. Our recent findings show that glaucoma suspects have similar biomechanical characteristics to those of glaucoma patients, particularly in the shape of lamina cribrosa as well as in the parameters describing corneal microstructure. Moreover, it was found that seemingly nominal intraocular pressure in the suspects group is sufficiently high for the reorganization of the corneal microstructure of similar character to that exhibited in the glaucoma group. Similarly Hirneiß et al. (Acta Ophthalmol. 2011: 89: e189–e192) reported that corneal biomechanical properties do not differ in both eyes of patients with unilateral primary open angle glaucoma. All this indicates that in the rare case of unilateral primary open angle glaucoma the fellow eye needs to be carefully monitored and treated.
IV Scientific and Training Conference. OCT in Ophthalmology.
The use of information contained in the corneal OCT speckle in the diagnosis of glaucoma
Corneal imaging, especially by means of optical coherence tomography (OCT), is associated with glaucoma studies mainly with the measurement of the anterior chamber angles to determine the type of glaucoma (closed / open angle). Studies show that imaging of the anterior segment of the eye, especially the study of statistical parameters of speckle in OCT images of the cornea, can also help in understanding the aetiology of normal tension glaucoma and help physicians in the diagnosis. The lecture discussed the latest scientific research on the assessment of OCT speckle, and its relationship with changes in corneal microstructure associated with age, swelling and intraocular pressure. In addition, results of a study were presented that was conducted on three groups of subjects: (i) with open-angle glaucoma, (ii) suspects due to the appearance of the optic disc and (iii) controls, in which the assessment of the corneal OCT speckle gives new light to the problem of normal tension glaucoma.
Autumn Ophthalmology Workshop. Military Institute of Medicine.
Advanced methods of measuring the ocular pulse
The ocular pulse concerns a number of phenomena related to the expansion of the eyeball caused by fluctuations of intraocular pressure, pulsed blood flow in the ocular circulation, as well as longitudinal eye movements in the orbit. The lecture discussed the latest research related to advanced measurements of dynamic changes in the intraocular pressure using Dynamic Contour Tonometry and in the blood flow in the ocular circulation using Color Doppler Imaging. In particular, the emphasis was placed on the usefulness of these techniques to help diagnose glaucoma and characterize the ocular pulse in glaucoma suspects.