Revision Tutorial Flashcards
What are the current visual standards required for a Group 1 driving licence (B)?
The applicant to the Driver and Vehicle Licensing Authority (DVLA) for a UK Group 1 driving licence must answer three questions about his/her vision:
* 1. “Can you read (with or without glasses or corrective lenses) a car number plate whose characters are 79 millimetres high and 57 millimetres wide from 20.5 metres (67 feet) or 20 metres (65 feet) where narrower characters (50mm wide) are displayed?“. This is consistent with a Snellen visual acuity of 6/12 according to the new
DVLA guidelines
2. “Do you need to wear glasses/corrective lenses when driving?“
* 3. “Have you ever had, or do you currently suffer from the following condition:
* - Any conditions affecting BOTH eyes, or the remaining eye if you only have one eye.
(Do not include colour blindness or short or long sight).
* - Any condition affecting your visual field.”
Are the following conditions a bar for getting Group 1 driving licence: diplopia, lack of colour vision, monocularity, glaucoma, high myopia, cataract, diabetic retinopathy and macular degeneration?
- Insuperable diplopia causes unfitness to drive. Diplopia correctable by prisms or patching is not a bar, provided the patient
always uses the prism/patch. - Lack of colour vision is not a bar to driving.
- Monocularity is not a bar to driving so long as adaptation to the
condition is complete and the eyesight standards can be met. - Progressive conditions such as glaucoma, high myopia, cataract,
diabetic retinopathy and macular degeneration require
notification, but a license will still be issued as long as the eyesight
standards are fulfilled. The licence is only issued for 1, 2 or 3 years,
however
What is the importance of the viewing distance for a computer screen user?
The viewing distance is an extremely important factor, particularly for presbyopes. Typically, the working distance to the screen, keyboard and documentation is further away than normal reading or working distance for office work and the prescriptions supplied to the patient should reflect this.
Each computer screen operator user can work in a very different way, so it is important to get the operator to simulate their working conditions at the work-station as closely as possible, so that the relevant working distances to the screen, keyboard and documentation can be assessed. These working distances need not be the same.
One of the major causes of patients requiring a correction solely for use with the computer is for a presbyope who requires a different correction for normal reading work than for the computer screen.
Describe the advantages and disadvantages of plastic lenses (compared to glass lenses) which are used in eye protectors?
Advantages:
* Greater impact resistance, particularly against high velocity particles.
* Scratches on the lens surface do not reduce the impact resistance.
* If the plastic lens is fractured, the fragments are larger and relatively blunt.
* The weight is about 50% of that of a glass lens of equivalent power.
* The plastic lenses can be thinner than glass lenses of equivalent power.
* Plastics withstand molten metal splashes and hot sparks better than glass.
* The plastic lenses have lower thermal conductivity which results in less condensation.
* Greater protection against UV radiation.
Disadvantages:
* Plastic material is soft and easily abraded. Additional abrasion-resistant coating may reduce the impact resistance.
* The refractive index for plastic lenses is in the range 1.49-1.60 which results in higher chromatic aberrations.
Describe the advantages and disadvantages of box- and cup-type goggles?
Goggles: An eye-protector that tightly encloses the orbital area and sits on the face. Goggles are
available in two forms:
* a) Box type - a single moulding covers both eyes and the bridge of the nose.
Advantages:
* full central field of view; wide field of view; one piece lens; good fitting with PVC surround;
good ventilation;worn over specs; grade 1 impact, dust, gas, chemical and molten metal
protection.
Disadvantages:
* no adjustment of nasal fitting; limited ability to tint or change lens; easily scratched; difficult
with multifocals; may impact on spectacles underneath.
* Example - heavy and hazardous industrial process, e.g. chemical factories, metal foundries,
shot blasting.
* b) Cup type - individual eyepieces connected with a flexible bridge of some sort.
Advantages:
* excellent eye enclosure; lenses easily changed; adjustable bridge; nose protection possible.
Disadvantages:
* not possible over spectacles; bridge adjustment may not go small enough; poor ventilation
which causes the lens to mist; uncomfortable; field of view restricted; Examples: grinding
work, small high-velocity particle hazard.
What are the properties of the following ocular: X 1 B 9 N (X denotes the manufacturers’ mark)?
X 1 B 9 N - Safety ocular with mechanical strength function (medium energy impact), optical class 1, non-adherence of molten
metals and resistance to penetration of hot solids function and resistant to fogging.
Example Uvex safety eyeware
What are the health screening principles?
1) The condition being sought should be an important health problem, for the individual and the community.
2) There should be an acceptable and effective form of treatment for patients with recognisable disease
3) The natural history of the condition, including its development from latent to declared disease, should be adequately understood
4) There should be a recognisable latent or early symptomatic stage
5) There should be a suitable screening test or examination for detecting the disease at the latent or early symptomatic stage, and this test should be acceptable to the population
6) The facilities required for diagnosis and treatment of patients revealed by the screening program should be available.
7) There should be an agreed policy on whom to refer and treat as patients
8) Treatment at the presymptomatic, borderline stage of the disease should favourably influence its course and prognosis.
9) The cost of case finding (including the cost of diagnosis and treatment) needs to be economically balanced in relation to possible expenditure on medical care as a whole.
10) Case-finding should be a continuous, not a “once and for all” project
Describe the effects of chemical hazards to the eyes?
The eyes can be at risk from exposure to a wide range of chemicals in vapour, liquid,
powder or solid form. The main problems are:
1) Damage to the external parts of the lids, cornea, conjunctiva and lacrimal apparatus. The most serious of these is corneal scarring, because it permanently affects vision. Chemical damage is caused by acids (battery manufacture) and alkalis (cleaning fluids), bleaches in dye works (chlorine, hydrogen peroxide), and a wide range of organic solvents (turpentine, carbon tetrachloride, acetone). Alkalis can be particularly harmful because they progressively dissolve the material of the cornea, instead of forming some sort of precipitate that slows down the action of the chemical.
2) External irritation may result from dust and gases at relatively low concentrations in the working atmosphere. Since such problems tend to be cumulative they get worse as the day/week goes on. Contact lenses, which tend to accumulate the contaminant, can be a particular problem. The use of eye protectors which are air tight with contact lenses also causes a problem due to the corneal anoxia. Good ventilation of the working area helps to reduce such problems.
3) Chemical poisons may reach the visual pathways indirectly though ingestion or absorption through the skin. This may cause toxic amblyopia, with concomitant visual field and colour vision effects. These problems tend to be permanent and require a prolonged exposure to the hazard.
What should optometrists do when they test a person of driving age who does not meet the current UK Visual Standards for driving?
- If they test a person of driving age who is found to fall
below the driving test standard, to ask if the person
drives, and if so inform them that they do not meet the
requirements. - This should be noted on the record.
- The patient should be warned that failure to report
the defect might jeopardise their motor insurance. - If it becomes clear they will not inform the authority,
advice can be sought from the AOP
What is required of a mechanical vision screener?
1) To show up deficiencies in VA that render distance or
near perception inefficient.
2) To show up an orthoptic disorder large enough to
render vision uncomfortable or difficult at work
3) To provide simple yes/no type answers to the test
4) To provide sufficient information for an ophthalmic
practitioner to assess visual capability for a given type
of job.
5) To be compact, portable, and suitable for operation
by a semi-skilled technician
Describe the effects of the following types of radiation on the eye:
- i) Ultraviolet
Short wavelength ultraviolet radiation (200-315 nm) is absorbed primarily by the cornea and conjunctiva. The effects of exposure to this type of radiation are conjunctivitis and photokeratitis.
These arise from photochemical damage caused by the energy of photons absorbed by superficial cells in these structures. The post exposure latent period varies inversely with the severity of the exposure, and lasts for 6-12 hours typically. The effects of multiple exposures to the radiation over a short period of time tend to be cumulative, so multiple exposures, or protracted exposures, to
relatively low doses of radiation can also cause problems. The commonest cause of photokeratitis is with welding equipment, and consequently the condition is often termed “arc eye” or “welder’s flash”.
* Longer wavelength ultraviolet radiation (315-400 nm), whilst it is partially absorbed by the cornea, penetrates increasingly into the eye as wavelength increases. This UV radiation can cause lenticular opacities. Daylight may be a cause of cataract formation, given that the incidence of cataract is higher in countries with higher sunshine figures. Areas where much of the light is reflected, such as from sand, sea, concrete, or snow, may require ocular protection. At high altitudes there is a higher content of UV radiation in the sunlight, due to less atmospheric filtering of the light. Skiing, then, can present a very real UV hazard unless suitable protection is used.
* In the normal eye very little ultraviolet radiation reaches the retina, but if it does reach the retina it can cause photochemical damage. Thus, it is important for aphakic individuals to have some form of UV protective tint, and pseudophakic individuals now often have implant lenses that have UV inhibitors incorporated into the material.
Describe the effects of the following types of radiation on the eye:
- ii) Infrared
Longer infra-red radiation is blocked by the cornea. The waveband from 750-2500 nm, however, is transmitted with gradually diminishing efficiency and with various absorption bands. There is some capture of energy by all the ocular structures and the means of damage in this case is the secondary heating effect caused by the absorption of the radiation. Such heating in the crystalline lens causes coagulation of the proteins in the lens and heat cataract. In industries such as steel or glass making infrared radiation presents a real hazard to the worker. The use of heat absorbing filters is thus of great importance in their jobs. The sun’s radiation can also
cause infrared radiation damage to the retina. Prolonged viewing of the sun with the naked eye can cause retinal damage, and the sun should never be viewed through focusing or magnifying lenses. The direct viewing of solar eclipses can cause retinal burns by direct thermal action, producing characteristic scars at the fovea.
