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Deep Learning Technology: Sebastian Arnold, Betty van Aken, Paul Grundmann, Felix A. Gers and Alexander Löser. Learning Contextualized Document Representations for Healthcare Answer Retrieval. The Web Conference 2020 (WWW'20)
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While surgeries do exist to correct for severe cases of floaters, there are currently no medications (including eye drops) that can correct for this vitreous deterioration. Floaters are often caused by the normal aging process and will usually disappear as the brain learns to ignore them. Looking up/down and left/right will cause the floaters to leave the direct field of vision as the vitreous humour swirls around due to the sudden movement. If floaters significantly increase in numbers and/or severely affect vision, then one of the below surgeries may be necessary.
Currently, insufficient evidence is available to compare the safety and efficacy of surgical vitrectomy with laser vitreolysis for the treatment of floaters. A 2017 Cochrane Review did not find any relevant studies that compared the two treatments.
Aggressive marketing campaigns are currently promoting the use of laser vitreolysis for the treatment of floaters. No strong evidence currently exists for the treatment of floaters with laser vitreolysis. Currently, the strongest available evidence comparing these two treatment modalities are retrospective case series.
Laser vitreolysis is a possible treatment option for the removal of vitreous strands and opacities (floaters). In this procedure an ophthalmic laser (usually a yttrium aluminium garnet (YAG) laser) applies a series of nanosecond pulses of low-energy laser light to evaporate the vitreous opacities and to sever the vitreous strands. During this process, the laser energy evaporates the collagen and hyaluronin molecules to form a gas. (It is important to note that the laser energy applied during vitreolysis treatment does not simply break the floater into smaller pieces. Instead, the laser energy converts the floater material to a gas, which is then absorbed into the eye.) The end result is that the floater is removed and/or reduced to a size that no longer impedes vision.
Vitreolysis is an outpatient procedure, which is much less invasive to the eye than a vitrectomy. Side effects may include cataract and intraocular pressure (IOP) spike. It offers a very good degree of patient satisfaction. It can also delay or obviate surgery.
The technique of using YAG lasers to treat vitreous strands and opacities dates to the 1980s, when professors Aron Rosa (Paris, France) and Franz Fankhauser (Berne, Switzerland), pioneers in the use of YAG lasers, both published on their success with vitreolysis.
In a Dutch study by Cees van der Windt, MD, and colleagues, 100 eyes, with PVD-related floaters persisting for more than nine months, were treated with YAG laser vitreolysis ("n" = 65) or pars plana vitrectomy ("n" = 35). After all eyes were treated, both the YAG and vitrectomy groups reported an improvement in vision at 85% and 90% respectively. Furthermore, over a follow-up period of eight years, no complications were observed among YAG-treated patients. These findings support those of two small-scale 1990s studies conducted by Tsai, et al., and Toczolowski, et al.. In both studies, a near 100% rate of floater removal was achieved with vitreolysis, and no intra- or post-operative complications occurred in any patient.
The number of floaters treated during a treatment session depends on the type of floater(s) and the laser energy required to treat the floater(s) (that is, to convert the floater material into a gas). During treatment, the ophthalmologist will monitor the level of laser energy used for each shot, as well as the total amount of energy delivered to the eye. In order to ensure safe, effective treatment with minimal patient discomfort, if these energy levels fall outside a predetermined range then any remaining floaters will need to be treated in a subsequent treatment session.
Every eye is different and there are a number of variables that affect the outcome of treatment. Some floaters, for example, are located too close to the retina and cannot be safely treated. The majority of patients will need to undergo two or three treatment sessions in order to achieve a satisfactory result.
When performed with a YAG laser designed specifically for vitreolysis, reported side effects and complications associated with vitreolysis are rare. However, YAG lasers have traditionally been designed for use in the anterior portion of the eye, i.e. posterior capsulotomy and iridotomy treatments. As a result, they often provide a limited view of the vitreous, which can make it difficult to identify the targeted floaters and membranes. They also carry a high risk of damage to surrounding ocular tissue. Accordingly, vitreolysis is not widely practised, being performed by very few specialists. One of them, John Karickhoff, has performed the procedure more than 1,400 times and claims a 90 percent success rate. However, the MedicineNet web site states that "there is no evidence that this [laser treatment] is effective. The use of a laser also poses significant risks to the vision in what is otherwise a healthy eye." A YAG laser optimized for use in the posterior segment, in addition to use in the anterior segment, is recommended for vitreolysis. In order to visualize the floater and target accordingly, the laser's light source must be positioned in the same optical axis as the ophthalmologist's visual axis. Most conventional YAG lasers, in contrast, use a lower angle of illuminating light. Whilst these lasers are well-suited to use in the anterior part of the eye, they are ill-equipped for use in the vitreous chamber, and thereby make it difficult for the ophthalmologist to visualize (and treat) the floater(s).
Closed-eye hallucinations and closed-eye visualizations (CEV) are a distinct class of hallucination. These types of hallucinations generally only occur when one's eyes are closed or when one is in a darkened room. They can be a form of phosphene. Some people report closed-eye hallucinations under the influence of psychedelics. These are reportedly of a different nature than the "open-eye" hallucinations of the same compounds.
There are five known levels of CEV perception which can be achieved either through chemical stimuli or through meditative relaxation techniques. Level 1 and 2 are very common and often happen every day. It is still normal to experience level 3, and even level 4, but only a small percentage of the population does this without psychedelic drugs, meditation or extensive visualization training.