Many patients with LASIK complications cannot be rehabilitated even after spending thousands of dollars and many years searching for comfortable RGP lenses. For these patients, another shot at surgery may be the only solution, though there are no guarantees. This simulation approximates the uncorrected vision of a patient with large pupils who received two short flaps, decentered ablations, and an optical zone smaller than his pupil diameter. Wavefront and topographies are included. A central zone of relatively greater acuity gives way to progressively greater levels of blur toward the periphery. Patient is currently scheduled to receive a retreat on the most advanced Visx platform available.
In normal, healthy eyes with good vision, blurry vision indicates a need for prescription lens that adds additional power or corrects astigmatism that distorts the natural optics of the eye. Unfortunately, blurred vision after refractive surgery may not be correctable, and can coexist with ghosting, smeared vision, or other visual abberations.
'Smeared' or 'streaked' vision is another perceptual phenomena sometimes reported by patients with complications from refractive surgery. Although 'smear' may seem to a less than technical term, many patients find that it nevertheless provides the best description of what they see. Some patients report their vision is smeared in two or more directions in a single eye. Like ghosts, smears vary in their transparency, with some being darker than others.
The term 'ghosting' was coined around 1957, and originally referred to the false image on a TV screen, caused by signal reflection. The perceptual effects of LASIK complications are often similar, but here, signal reflection results from irregularities in the corneal surface. Ghosts vary in terms of transparency, size, and colors ghosted. We have worked with patients with ten or more ghosts in low light conditions.
The term 'glare' is sometimes used to refer to any visual aberration resulting from refractive surgery. In the author's opinion, this usage is archaic, and reflects a lack of understanding of the perceptual phenomena that afflict those with complications. Here, the term is restricted to situations in which light seems to overflow, or 'seep outside,' its normal boundaries around light sources, or sources of reflected light, such as shiny objects.
Halos are another phenomena reported by some laser eye surgery patients, particularly at night. Halos are usually seen as huge globes of illuminated fog surrounding sources of light. Sometimes the globes seem to contain other globes, brighter and denser, nested two or more levels deep. From a simulation perspective, starbusts and halos exist on a continuum, with starbursts shading into halos as the rays become less distinct and diffuse into each other.
Loss of Contrast
Contrast sensitivity is something that individuals with normal vision take for granted. When contrast sensitivity is lost, the ability to distinguish between variations of hue and brightness is lost. Perceptually, this effect is similar to turning down the Contrast adjustment on your television of monitor: Eventually sharp boundaries are lost. Objects merge together,as if a haze of grey soup had been poured over one's visual field.
Some laser eye surgery patients see rays or fine filaments coming off lights, even during normal daytime lighting conditions. At night, these rays can become dramatically longer and denser, something referred to as 'starbursting.' Starbursts are highly variable between patients, differing in terms of their size and shape, length of rays, the density of rays, and transparency (whether the light source is visible through the starburst).
The floaters simulator was created on the basis of feedback from Floater suffers, including individuals facing vitrectomy. Some of these sufferers face floaters as a consequence of "natural causes," while others report increased floaters following LASIK surgery. Cutting the LASIK flap involves creating suction to pull the cornea up into the microkeratome. The resulting spike in intraocular pressure contributes to vitreous detachment, which in turn causes floaters, where none may have existed before.
A cataract is a clouding of the lens inside the eye. The lens is a clear structure behind the pupil that helps focus light on the retina. In the normal eye, the lens is completely transparent. Most cataracts are age-related, being much more common in older populations. A lens clouded by cataract produces vision that becomes progressively blurrier and more yellow or brownish over time. Eventually, ordinary activities such as reading and driving become impacted, lowering quality of life.
The receptors responsible for human vision are located on the retina, at the back of the eye. Information from these receptors is aggregated at the optic nerve, and sent on to the visual cortex for further processing and interpretation. Portions of the retina that are detached are no longer in communication with the brain, resulting in areas of blankness or blackness. Spatial distortions may exist at the margin of the detachment.
Glaucoma is a group of eye diseases that slowly steal sight, often with no immediately recognizable symptoms. Most often, vision loss is the result of increased pressure inside the eye, which causes damage to the optic nerve. As glaucoma progresses, peripheral vision becomes more and more compromised as the area of effective vision continues to shrink. How does pressure cause loss of sight? Think of the eye as a balloon filled with air. As more air is pumped in, the balloon expands. The eye, however, is too strong to expand. As the pressure increases, the eye gives at its weakest point, where the optic nerve leaves the eye.
Patients who complain of Visual Snow literally see what resembles "television snow," that is, specs or particles that blink on and off in their vision.
Hemianopia refers to loss of vision in one half of the visual field of both eyes, most commonly on the right side. Causes of hemianopia include injury to the brain (temporal or occipital lobe) or optic nerve pathways from accident, infection, stroke, or tumor. Hemianopia may also affect the upper or lower halves of the visual field.
Visual Quality Disparities
Patients with bilateral eye injury or LASIK complications may report different aberrations in each eye. With both eyes open, these aberrations are synthesized to yield a composite image. However, one eye usually contributes more to the resulting composite than the other, a phenomenon known as "ocular dominance." This simulation illustrates one possible scenario, in which vision in the left eye is blurred following LASIK, whereas vision in the right eye is ghosted.
Aberrations & Pupil Size
Patients with complications from refractive surgery often report that their vision seems much better in bright light than dim light. Not only does bright light help compensate for Loss of Contrast Sensitivity, it also shrinks the pupil, reducing the visual aberrations caused by an irregular cornea.