• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Snow Blindness

Extracts from this document...

Introduction

Snow Blindness Photokeratitis- `welder's flash' or `snow blindness'. The greatest retinal exposure to blue light UV occurs outside standing/walking in a field of snow without eye protection= exposure to levels exceeding occupational exposure limits. Failure to wear ski goggles can result in several effects upon the eye, sometimes loosely referred to as `snow-blindness'. Unusually intense reflection of light and UVR from the snow. * Fresh snow reflects 85% of the UVR compared to only * 1 or 2% from grass. * Goggles with side-shields, or a closely fitting wrap-around design, the specification of 99% or 100% UV blocking. * UV light can enter the eye from the sides and also by reflecting off the edges of the sunglasses. Therefore, side shields and overhead protection are critical and can be provided with wrap-around sunglasses or goggles. * Polarising sunglasses protect against excessive glare. Prevention of UV exposure Protection: * broad-brimmed hat or visor can help shield the eyes from both visible and invisible light * The eyelids, the same as the skin elsewhere on the body, should be protected by use of a sunscreen. * UV-absorbing spectacles. Large frames and wraparound designs offer the greatest protection to both the eyes and the eyelids. UV-absorbing contact lenses are available from a number of lens manufacturers and are preferred to non-UVabsorbing materials in individuals who spend a lot of time outdoors. ...read more.

Middle

Ophthalmic oncologists use high frequency ultrasound to diagnose and follow iris tumors for evidence of growth. Characteristics which suggest that an iris tumor is cancerous include seeing blood vessels within the tumor, evidence that the pupil is deformed, and the development of a cataract beneath the tumor. Tapioca-colored iris tumor has pulled the iris pigment epithelium out onto the surface of the iris stroma. The most important finding is documented growth. Since iris melanomas are commonly small, and rarely (1-5%) spread to other parts of the body, these tumors are usually watched for evidence of growth before treatment is considered. Treatment: Most pigmented iris tumors do not grow. They are photographed and monitored with periodic observation. When an iris melanoma is documented to grow, we know that it can damage the eye (usually cause glaucoma). Then, treatment (despite its risks) becomes more reasonable. Small melanomas: Most small iris melanomas can be surgically removed. Medium-sized melanomas: Large iris resections are possible, but plaque radiotherapy may be considered for these tumors. A cataract is likely to develop, but since the radiation plaque is far from the central retina, vision limiting radiation retinopathy is unlikely. Large-sized melanomas: These cases can be difficult to treat with eye-sparing therapies. Many of these tumors cause untreatable glaucoma and may require removal of the eye. Squamous cell carcinoma A cancer that develops from squamous cells found in the skin that covers the outside and lines the inside of the body * Second most common malignant eyelid neoplasm in the United States, after basal cell carcinoma. ...read more.

Conclusion

along the surface and an atrophied inner portion, creating a "pearly," indurated outer margin with an excavated center; and 3. Less frequently, the sclerosing or morpheaform basal cell carcinoma form, which has a firm, pale, waxy yellow plaque with indistinct borders. There is no single known cause for all forms. There is a distinct association with increasing age and exposure to UV radiation. Caucasians have a much greater chance of developing basal cell carcinoma than other races. Progression of this tumor is, in most cases, exceedingly slow. Left untreated the lesion may in time invade deeper structures. Fortunately, metastasis is rare, and complete recovery is possible with proper therapy. Basal cell carcinoma can be treated with * surgical excision, * radiation therapy or * chemotherapy. The preferred course for most cases is surgery, with broad margins to ensure complete removal. Local radiation therapy and/or systemic chemotherapy can manage basal cell carcinoma when surgery is intolerable or refused by the patient. Both of these modalities carry significant side effects, however, and neither is as effective as surgical intervention. * Basal cell carcinoma is rarely life-threatening because of its non-metastatic, slow-growing nature. However, this tumor does possess the capacity, over time, to cause significant local destruction, and must always be treated appropriately. * Early biopsy is often the key to diagnosis. Biopsy all suspicious lid lesions which demonstrate irregular growth, changes in color or appearance, or purulent or bloody discharge to rule out cancer. You should refer confirmed malignancies promptly to an oculoplastics specialist or, if possible, an ocular oncologist. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Molecules & Cells section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Molecules & Cells essays

  1. All flesh is grass.

    The reaction for nitrogen fixation is catalysed by nitrogenase, an enzyme containing iron and molybdenum.

  2. Follicular development

    In response to the FSH and LH surge at ovulation, these follicles continue their growth and differentiation. Growth of the ovarian follicle occurs at different rates and is divided into 3 stages: preantral growth, tonic growth, and exponential growth. The preantral growth phase involves the differentiation of the primordial follicles into primary follicles, which then form the preantral follicles.

  1. How would the power input to a solar cell change if it was not ...

    The full list of apparatus and details of each are as follows; * Voltmeter - I will decide which setting to put the voltmeter on when I start my preliminary tests, as to ensure that it is the setting that can display the whole number with the most decimal places, to ensure accuracy.

  2. My presentation on the material wood.

    One of the major botanical distinctions between softwoods and hardwoods lies in the structure of their wood. In softwoods, the cells that serve to transport water also provide the mechanical support for the stem. In hardwoods, some division of labour has evolved, with some cells specializing in water transport, and others in providing mechanical support.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work