Month: June 2019

The latter is probably more applicable to keratomes with lower oscillation rates. Similarly, flat corneas may result in a thin and/or small flap as they could be below the adequate cutting level in certain locations. Inadequate blade to cornea coupling is often due to poor suction (sunken globe/small diameter corneas with inadequate suction ring placement, conjunctival incarceration in the suction port…). Non-angled blades have equal chances of moving upwards towards the surface or downwards towards the stromal side if faced with resistance. On the other hand, inferiorly angled blades are more likely to be driven towards the stroma. If a buttonhole is encountered (especially centrally), most surgeons prefer to abort the procedure, replace the flap and re cut a deeper flap (20-60 ?m deeper) approximately 10-12 weeks later. While some advocate proceeding with scraping the epithelium and performing a PRK laser ablation, we believe this approach may not be feasible in higher myopes due to the appearance of unexpected haze.

A higher index for epithelial ingrowth should maintained around the margins of the buttonhole. The incidence of perforated flaps (as well as thin and irregular ones) may be reduced if the surgeon ensures adequate suction, inspects the blades and adjusts the keratome plate thickness according to corneal curvature. Other helpful measures include ensuring adequate intraocular pressure before cutting the flap. Measurement may be most valuable with a pneumotonometer as other means were reported to provide imprecise readings at times. Care should be taken to avoid conjunctival clogging in the suction port, which could lead to discrepancy between the intraocular pressure and the suction pressure recorded on the microkeratome vacuum console. Newer microkeratomes have a safety mechanism to automatically abort the procedure or to activate additional suction but are also prone to similar problems if IOP measurements are not obtained to ensure adequate suction. Some surgeons inspect the microkeratome blade under the operating microscope before engaging it in the suction ring in order to rule out manufacturing or other preoperative damage to the blade. It is best to keep the microkeratome away from hard surfaces after assembly to avoid subsequent blade damage.

Nuts

Nuts have a lot of omega 3 fatty acids. According to the research, these fatty acids can slow down age-related macular degeneration. They can also help avoid dry eyes as they are also known to preserve the moisture of the eyes.

Almonds are especially rich in vitamin E and are excellent to slow down age-related eye damages. A handful of almonds every day are enough to keep both your vision and over-all health sharp.

Carrots

Carrots do not have a direct effect on eye-sight but they improve over-all eye health. Carrots have a compound in them which is known as beta-carotene. Beta-carotene is the primary source of vitamin A in the body.

According to WHO, Vitamin A deficiency is one of the leading causes of blindness in the world. Thus, carrots can substantially decrease the risk of blindness, especially for people living in developing countries.

Spinach

Spinach is rich in a compound called lutein. Lutein is one of the pigments present in the macula. Macular pigments are crucial for vision and they are vulnerable to degeneration. Consuming the green leafy spinach can help you replenish this pigment.

In other words, spinach is ideal if you want to avoid macular degeneration and even age-related cataracts. It is also important that you eat raw spinach because cooked spinach is likely to lose all of its nutritional benefits.

Blueberries

Blueberries are one of the healthiest food available naturally. They are rich in anti-oxidants known as anthocyanin. Anthocyanin’s not only give blueberries their purple colour, but they also act as anti-viral and anti-inflammatory agents for the human body.

So, eating blueberries enhances immunity and as a byproduct gives resilience to eyes against infections. Blueberries can thus protect the retina against damaging UV rays in the sunlight. They can also protect the eyes from oxygen damage.

Egg Yolks

Egg yolks can also slow down the process of macular degeneration. They are rich in both zeaxanthin and lutein pigments which are crucial in keeping the vision sharp. Lutein and zeaxanthin accumulate in the middle of the macula and cancels out all the free-radicals, filtering the blue light out. We need around 6mg of these anti-oxidants every day. One egg yolk has around 0.25 mg of the antioxidant pigments and can thus be an ideal source.

Macular degeneration is one of the leading causes of poor eye-sight. The foods mentioned in this article do not prevent macular degeneration but they can certainly slow the process down.

The Retinal Implant

An eye is a precious part of a human which plays an integral sensory role for the visual capability of the vision. Because of many factors this part may come to loose its visionary sensing power in some human beings. For example, Age-Related Macular Degeneration (ARMD) is a progressive disease of the retina wherein the light-sensing cells in the central area of vision (the macula) stop working and eventually die. By replacing the dead part of retina with the retinal implants, theoretically and practically, the diseases related with retina can hopefully be controlled.

The principle and working of an Eye

The construction of the Eye is similar to that of a camera. In principle, the visible light is focused by a lens on a screen called the retina and the image is realized. Fig.1 (please find at http://webvision.med.utah.edu/sretina.html) shows a cross-section of human eye ball with its different parts. The Retina, being the most significant in the functioning of the eye, is composed of layers with different cells as shown in Fig. 2 (please find at [http://www.farlops.com/images/photos/retina.jpg] )
The light first enters the Nerve Fiber Layer and the Ganglion Cell Layer, under which most of the nourishing and aiding blood vessels of the retina are located. This is where the nerve begins, picking up the impulses of the acquired image from the retina and transmitting them to the brain. The light is received by the Photoreceptor cells called Rods and the Cones. These cells convert light into nerve impulses, which are then processed by the retina and sent though nerve fibers to the brain. The nerve fibers exit the eyeball at the Blind spot and reach the brain through the Optic nerve. The further anatomical details can be found elsewhere.

The Retinal Implant Functionality

To help visually impaired patients, a visual prosthesis could be designed to be placed in the eye, either under or on the retinal surface, sub retinal areas, etc, in the optic nerve, or in the visual cortex of the brain. Each approach has certain advantages and disadvantages.
Based on the above principal idea, the light is sensed by a large assembly of photo-receptor diodes integrated on a Chip connected with the electrodes for the electrical power. This chip collects the information of the sketched image fall on it and triggers the family of cells grown on this chip. The function of this chip/implant is the same as the retinal photoreceptor cells which are connected with the bipolar cells and ganglions and transmitting the photo signal to the respective part of the optic nerve [Ref. 4]. It is not easy to explicate the phenomena for the transmission of the sensed sketch produced in the chip of photoreceptor diodes to the grown cells of the retina, and from them to the optic nerve. Biologists and chemistry people are trying to resolve these phenomenons into a simple, explainable and electronically feasible for the best possible performance of the retinal implants.

Conclusion and Future work

There are certain flaws for the In-vivo application of retinal implants. Bio-compatibility, one of the first main issue, of an Implants means especially the metal electrodes and the whole chip (the electronics) must be able to resist the body environment. The electrolytic properties of the blood, pH and ionic behavior of the In-vivo environment are some crucial parameters, nowadays faced by the scientists. The compatible implants should also be longtime susceptible to the animals as well as to the human beings.
Similarly, the diffusion of liquids through the sealing and packed retinal implant is also a great challenge that limits the working period (life) of an implant. For the commercial available synthetic materials, (plastic foils, etc) the permeability rate of water vapors is 5*10-3 g/m2/day. Scientists are seeking the best possible material with the least permeation which would in turn enhance the life time stability and bio compatibility of the implant in the body.
Besides the state-of-the-art device fabrication improvements, a visual prosthesis must receive two types of inputs, information about the visual signal from the retinal implant and the power to run this whole electronic assembly. It is detrimental for the purposes of long-term implantation to have wires penetrating the body or imbedded batteries that could corrode and have to be replaced if not properly sealed as mentioned above. Alternatively, one can send the visual signal and power to the implant without the use of wires. Wireless communication can be accomplished with laser light or radiofrequency transmission.
Before performing experiments on the human eye, it is necessary to perform laboratory experiments to determine safe methods of device implantation and electrical stimulation of the retina. These studies are performed in vitro (i.e. outside the animal; using tissue preparations) and in vivo (i.e. in the living body). In order to carry out such experiments, approval must be obtained and granted from committees that monitor experimentation with animals and humans from all the over the world.

The pigment lutein (LOO-teen) (from the Latin lutea, meaning “yellow”) is one of over 600 known naturally occurring carotenoids. It’s found in corn, egg yolk, and other yellow and green fruits and vegetables, but it also occurs in some eye tissues, specifically the pigment of the retina and parts of the lens.

Lutein may play a role in slowing the age-related degeneration of these tissues, both directly as an antioxidant, and indirectly by absorbing blue light. In fact, various research indicates that a direct relationship exists between lutein intake and pigmentation in the eye, and studies show that it may reduce blue light intensity by up to 90%. It’s one of the secret weapons plants use to protect themselves from the sun.

Most people consume lutein as part of a normal diet containing fruits and vegetables, but elderly and ill people can gain from taking a lutein supplement, because their digestive systems may not be functioning at an optimal level. In addition, much of the food grown and distributed today lacks a healthy nutritional content, on account of pollution, poor soil, long storage periods and so on. That means most people could well benefit from supplementing with lutein.

Another superb antioxidant particularly appreciated by your eyes is Vaccinium myrtillus, more commonly known as bilberry (and also as whortleberry, blaeberry, whinberry/winberry, whortleberry, fraughan, and myrtle blueberry!) Bilberry shrubs grow in the world’s temperate regions and produce a fruit that’s eaten fresh or used to make desserts, preserves and drinks. It’s leaves have also historically been used to treat a range of gastrointestinal disorders.

One particular plus point of gorging on bilberries, is that they are said to improve night vision, and rumour has it that RAF pilots in World War II used them specifically for that purpose. Studies have shown they may also reduce or reverse the effects of MD, probably due to the effects on blood capilliaries of their antioxidant chemicals, called anthocyanidin flavonoids.

Anthocyanidin flavonoid compounds are derivatives of the pigments that cause the blue, violet, or red colours in flowers and fruits. At least fifteen different versions have been identified in bilberry extracts, which means bilberry supplements can deliver a powerful dose of them right to where they are needed most: in your eyes.

Aside from lutein and bilberry, another excellent ‘eye supplement’ is zeaxanthin. It’s one of the most common carotenoid alcohols found in nature, and is the pigment that gives saffron, corn and other yellow plants their characteristic colour.

More importantly, zeaxanthin is one of the two carotenoids contained in the retina (the other being lutein, as we saw previously). Experiments have shown that low levels of zeaxanthin can have a detrimental an effect on the eye, in the same way that a lack of lutein can. For that reason, some studies support the view that supplemental lutein and/or zeaxanthin helps protect against AMD. There’s also a fair bit of evidence that increasing your intake of lutein and zeaxanthin will lower your risk of developing cataracts.

Aside from lutein, zeaxanthin and bilberry, The Age-Related Eye Disease Study (a clinical trial sponsored by the U.S. National Institutes of Health) shows that a combination of high-dose beta-carotene, zinc, vitamin E, and vitamin C can reduce the risk of developing advanced AMD by around 25%.

Dr. Tom Tooma, an eye surgeon and specialist practicing in Newport Beach, California, has made a name for himself mastering the LASIK vision correction method. By utilizing a medical laser, a trained surgeon, like Dr. Tooma, can permanently correct the vision of anyone who meets the surgery’s requirements. Eligibility can be determined by a quick, painless appointment. He has corrected the vision of more than 60,000 patients since the mid-1990s. His intimate knowledge of the process has resulted in various improvements and breakthroughs concerning the LASIK procedure. Indeed, his research and guidance helped LASIK garner FDA approval.

He was the first doctor in California to perform LASIK surgery and the first to perform Custom Wavefront Guided LASIK. In fact, it is contended that he has performed more CustomLASIK procedures with the Alcon LadarVision laser than any surgeon in the world. Moreover, Dr. Tooma was the first doctor in the world to use the Femtosecond Laser (IntraLase FS30). Using the IntraLase laser rather than the blade (microkeratome) makes the procedure safer and more precise, and increases the chance of 20/20 or better vision.

In addition to LASIK procedures, Dr. Tooma also performs radical new procedures that utilize radio waves. Incredibly, this correction procedure takes only 3 minutes and entails the reshaping of the cornea. Known in medical circles as keratoplasty, most patients feel no discomfort and can resume their daily activities almost immediately.

What toric lenses do is provide a correction that compensates for the shape of the cornea. Since contacts float on top of the eye and turn as you blink, a toric has a small, invisible weight at the bottom of each lens that constantly helps the contact rotate back into the proper position needed to provide the wearer with clear vision. This makes it important for wearers of torics to do the following to ensure their lenses float freely:

• Blink frequently to rewet the eyes.
• Use rewetting drops as needed to resolve dry eye issues.
• Keep contacts clean and free of debris or buildup which may throw off the balance of the lens on the eye.

Because of the added correction for astigmatism in toric lenses, they typically cost more than the average contact lens and are often made of a more sturdy material. Additionally, many find that wearing torics for extended periods results in discomfort and blurred vision because they cannot keep their contacts wet enough to float freely on the eyes. Another cause is the buildup that naturally occurs from wearing contacts created by the counterweight, which keeps the lens from staying in the position needed for proper correction.

The best way to decide whether toric contact lenses are right for you is to discuss it with your optometrist who may also be able to provide you with a free trial pair of disposable torics before you make your final decision. This will allow you to wear a pair for a while before spending your money on a product that may not work for you.

There are many eye problems that are commonly found in children. The major problem is the refractive error, the common mode of presentation is that the child is not able to see the distant objects usually seen in the school where the child fails to see clearly the letters written by the teacher on the blackboard. Most of the time the child holds the book very close to the eyes while reading. And also child watches TV and Computers from a very close distance.

The other problems are – Vitamin A deficiency, Squint eyes and Retinoblastoma (Eye Cancer).

Refractive Errors:

There are mainly three types of refractive errors. Myopia, Hypermetropia and Astigmatism.

Myopia : This is the most common refractive error found in children. Usually it is detected when the child is having problem in seeing distant objects. Occasionally the child may have a slight pain in the eyes after reading for many hours. The light rays are focused in front of the retina in myopia with the result that the objects appear hazy.( If we have to see a clear object it has to be focused on the retina.) Sometimes it has a strong family history. The eye has to be properly examined by a competent Ophthalmologist (not by an Optometrist) and suitable glasses prescribed at the earliest. Regular follow – up is also a must in these children.

Astigmatism is another refractive error seen in children not as frequently as Myopia. Hypermetropia where the child has + numbers in glass, is comparatively less in frequency. Suitable glasses correct both these refractive errors.

Vitamin A Deficiency:

Vitamin A Deficiency is demonstrated in school going children. Usually children in the age group of 6-12 years complain of night blindness. In other words those children have inability in seeing objects clearly in dim light. Sometimes small pigmented patches are seen by the side of the cornea. These are called Bitot’s spots. At this stage the child has lot of watering in the eyes.

A substance called visual purple has to be created in the retina to visualize objects clearly in the dim light. Vitamin A is necessary to create this object. When there is deficiency of Vitamin A in the diet, child gets night blindness. Sometimes some skin problems are associated along with eye problems.

Vitamin A deficiency is treated by giving capsules of Vit.A 2500-5000 IU or 750 mg of beta-carotene. In severe cases injections may be needed. Green leafy vegetables, carrots, milk, curd, butter, egg, liver etc., have rich contents of Vitamin A.

Squint Eyes : The two eyes normally should be in a definite visual axis. A manifest deviation of the visual axis of either eye is known as squint or strabismus. Mainly there are two types of squints – Paralytic and Non-paralytic or Concomitant. Concomitant is the one which is mostly seen in children. Concomitant deviations are for the most part, produced by anomalies of the power of convergence and divergence and the co-ordinated use of the two eyes to obtain binocular single vision. In these cases the amount and character of the deviation does not vary when the eyes are turned to the right or left.

The other classification of squint is – Convergent and Divergent. Convergent squint is the one in which one of the eye is turned inside, whereas in divergent squint one of the eye is turned outside.

Each child with squint has to be properly investigated before undertaking treatment. The common methods of treatment are – 1) Correcting the refractive errors by glasses whenever that is found to be the cause of the squint. 2) Deliberate occlusion or patching of the fixing eye so as to improve the vision of the squinting eye. 3) Suggesting special type of ( Orthoptic) exercises to improve the binocular faculties. 4) By surgery to restore parallelism of the visual axis. One or more of these methods or all four may be needed.

Retinoblastoma: It is the cancer or malignant tumor of the eye , usually seen in children below 5 years. It may be seen at birth or later. This disease not only affects the vision, but also life itself if it is not diagnosed and treated properly at an appropriate time. It may be seen in one eye or both.

Usually the child is brought to the eye specialist with the complaint that something white or yellow material is seen in the eye. If one eye is swollen enormously, it is understood that the disease is advanced. Treatment is usually removal of the eyeball as soon as the disease is diagnosed and the cut portion sent for biopsy. After the removal of the eyeball, if there are any signs of the disease,

Radiotherapy is advised. At this stage the other eye is examined and if any traces are found it is also subjected to radiotherapy. In the advanced stage of the disease, it is mandatory to treat with chemotherapy.