1
Volume 69 January 1976
63
Joint Meeting No. 1
Section of Ophthalmology President E C Zorab FRCS
with Section of Occupational Medicine President Peter G Swann OBE MD
Meeting 13 February 1975
Occupational Eye Problems I Eye Injuries Mr A Stanworth (Department ofOphthalmology, Hallamshire Hospital, Sheffield 10)
Late Complications of Ocular Injury Late complications fall into three groups: direct results of the ocular injury, secondary involvement of other tissues, and late sequelae not easily predictable. Direct Results of the Injury These include late glaucoma associated with obvious damage and distortion of the anterior segment, retinal detachment and disorganization of the globe from severe perforating injuries. The potential for such complications is usually obvious from the severity of the original injury, but the exception is the late development of cataract from apparently minor trauma. All ophthalmologists are aware that a tiny foreign body may perforate the globe and damage the lens, often with a small hole in the iris, leading to the slow development of cataract; by the time the patient notices loss of vision he may have entirely forgotten the accident.
Secondary Involvement of Other Tissues Lid injuries, particularly bums, can lead to tiichiasis, entropion, ectropion and irregular lid margins which result in secondary corneal damage. Orbital injuries: Blow-out fractures of the floor of the orbit involve the extraocular muscles and give diplopia. This may be missed in the early stages, being masked by lid swelling. Most such injuries require surgical repair, though some may be left alone; occasional ones give unexpected late deterioration in the double vision as the repair processes proceed, requiring surgery. Untreated blow-out fractures can result in con-
spicuous downwards displacement of the globe and enophthalmos, but useful binocular single vision may be preserved. A patient with apparently good recovery of binocular vision, after a deep penetrating injury of the'orbit through the lower lid, developed gross fibrosis around the superior rectus muscle two years later, the eye being hidden under the upper lid. Release of the superior rectus muscle gave an excellent cosmetic result with a useful area of binocular single vision in the primary position. Late Complications, not Easily Predictable Sympathetic ophthalmia must be mentioned; though rare, its existence colours our approach to the management of severe injuries. Immunological investigations might eventually make it more easily diagnosable and predictable. Siderosis, the late toxic manifestation of a retained foreign body, is of importance mainly because of retinal damage. Like cataract, siderosis may be the first sign of an unsuspected foreign body. The early signs of retinal degeneration may be detected by electroretinography or by electro-oculography, which is sometimes more sensitive (Kelsey 1968). Removal of the foreign body even at a late stage may be worth-while, though some continuing deterioration is to be expected from the iron already absorbed. Choroidal rupture, usually concentric with the disc and involving the retina over it, may produce obvious immediate visual loss, but even those ruptures which just miss the macula may give late macular oedema six months to five years after the accident, probably from neovascularization (Smith et al. 1974). Fluorescein angiography might help to detect those likely to progress, and light coagulation might then be indicated. Retinal detachment, as already mentioned, may be a fairly obvious late complication of severe
Proc. roy. Soc. Med. Volume 69 January 1976
2
trauma leading to vitreous hemorrhage, adhesions, and bands which may need intravitreous surgery; but it may follow much more subtle changes. Concussion of the eyeball of the type that produces hmmorrhage into the anterior chamber (traumatic hyphtema) may be accompanied by commotio retinxe with dialysis of its anterior insertion, round holes at the macula or elsewhere, vitreoretinal adhesions producing whitish areas or areas which become white when the sclera is indented ('white with pressure') and vitreous condensation and bands. The situation can be assessed one month after the hyphaema has absorbed (Sellors & Mooney 1973) though the risk continues long after this. Prophylactic light coagulation or cryotherapy is occasionally indicated. Glaucoma can also be a late complication of traumatic hyphoema. Examination of the angle of the anterior chamber shows recession of the angle. Unless the patient is predisposed to glaucoma for some other reason glaucoma probably occurs only if the recession affects more than 180 degrees, and usually more than 270 degrees (Kaufman & Tolpin 1974). The recession can be assessed one month after the accident, but the glaucoma may take some years to develop. Provocative tests for glaucoma might be helpful in prognosis. Defects of accommodation and convergence usually follow head injuries, but occasionally a defect of accommodation may be an unexpected persisting complication of concussion injury when the eye has otherwise apparently fully recovered. A conjunctival implantation cyst may arise at a late stage.
Laser light obeys the laws of optics but differs from that produced by conventional sources in some important aspects. The light is monochromatic, and the absence of chromatic aberration permits focusing to produce spot sizes as smaU as one wavelength. The light is coherent, each wavefront being precisely in phase with its neighbours. The beams of light produced by lasers are usually of small diameter, intense and highly collimated, the energy density within the beam only decreasing slowly with increasing distance. The wavelengths at which lasers emit now stretch from the near ultraviolet to the far infrared and the wavelengths of the most common industrial lasers are: argon (488 nm), helium neon (632.8 nm), ruby (694.3 nm), gallium arsenide (900 nm), neodymium (1060 nm) and carbon dioxide in the far infrared (10.6 tm). Lasers may be subdivided into two groups according to the duration of their output: pulsed and continuous wave (CW). Pulsed lasers may be of two types, normal pulse or Q-switched. Normal pulse lasers deliver their energy in a few milliseconds whereas Q-switched pulses may only last nano (10-9) or pico (10-12) seconds. CW systems normally emit a continuous beam but it is possible for some CW lasers to deliver a train of rapid pulses instead. This is called mode locking; it may be difficult to detect and represents a special hazard (Smart et al. 1970). Each of the special features of laser light has found an industrial application. The ability to focus the intense beams into small spot sizes can produce temperatures of several thousand degrees centigrade. This thermal property is used in the drilling, welding and cutting of a variety of materials including those previously considered to be refractory. Collimation is used by surveyors and engineers to produce a reference beam in tunnel construction, pipe laying or dredger control. The coherent properties are of value in three dimensional photography (holography) precision engineering, communications and data
64
Acknowledgment: I am grateful to Mr Ian Strachan for allowing me to mention some of his patients. REFERENCES
Kaufman J H & Tolpin D W (1974) American Journal ofOphthalmology 78, 648 Kelsey J H (1968) In: Advances in Electrophysiology and Pathology of the Visual System. Ed. E Schmoger. Georg Thieme, Leipzig; pp 19-28 Sellors P J H & Mooney D (1973) British Journal of Ophthalmology 57, 600 Smith R E, KeDey J S & Harbin T S 1974) American Journal of Ophthalmology 77, 650
processing..
The eye is adapted to refract light in the wavelength band 400-1400 nm and bring it to a focus at the retina. At both ends of this band in the near ultraviolet and far infrared all biological tissues are opaque and energy is absorbed in skin, conjunctiva and cornea. With the diversity of wavelengths at which lasers emit, all ocular structures Dr D H Brennan (RAFInstitute of are potentially at risk. Aviation Medicine, Farnborough, Hampshire) The laser properties of beam intensity and collimation which are so valuable to industry Ocular Complications of Industrial Lasers Lasers and their applications have developed constitute the ocular hazard. The small beam rapidly following the introduction of the first divergence ensures that energy densities are ruby laser in 1959. There is now a significant maintained over large distances, and that all or a possibility of accidental ocular damage from the large proportion of the beam is able to enter the eye through the pupil. The focusing mechanism intense beams of industrial lasers.
Volume 69 January 1976
63
Joint Meeting No. 1
Section of Ophthalmology President E C Zorab FRCS
with Section of Occupational Medicine President Peter G Swann OBE MD
Meeting 13 February 1975
Occupational Eye Problems I Eye Injuries Mr A Stanworth (Department ofOphthalmology, Hallamshire Hospital, Sheffield 10)
Late Complications of Ocular Injury Late complications fall into three groups: direct results of the ocular injury, secondary involvement of other tissues, and late sequelae not easily predictable. Direct Results of the Injury These include late glaucoma associated with obvious damage and distortion of the anterior segment, retinal detachment and disorganization of the globe from severe perforating injuries. The potential for such complications is usually obvious from the severity of the original injury, but the exception is the late development of cataract from apparently minor trauma. All ophthalmologists are aware that a tiny foreign body may perforate the globe and damage the lens, often with a small hole in the iris, leading to the slow development of cataract; by the time the patient notices loss of vision he may have entirely forgotten the accident.
Secondary Involvement of Other Tissues Lid injuries, particularly bums, can lead to tiichiasis, entropion, ectropion and irregular lid margins which result in secondary corneal damage. Orbital injuries: Blow-out fractures of the floor of the orbit involve the extraocular muscles and give diplopia. This may be missed in the early stages, being masked by lid swelling. Most such injuries require surgical repair, though some may be left alone; occasional ones give unexpected late deterioration in the double vision as the repair processes proceed, requiring surgery. Untreated blow-out fractures can result in con-
spicuous downwards displacement of the globe and enophthalmos, but useful binocular single vision may be preserved. A patient with apparently good recovery of binocular vision, after a deep penetrating injury of the'orbit through the lower lid, developed gross fibrosis around the superior rectus muscle two years later, the eye being hidden under the upper lid. Release of the superior rectus muscle gave an excellent cosmetic result with a useful area of binocular single vision in the primary position. Late Complications, not Easily Predictable Sympathetic ophthalmia must be mentioned; though rare, its existence colours our approach to the management of severe injuries. Immunological investigations might eventually make it more easily diagnosable and predictable. Siderosis, the late toxic manifestation of a retained foreign body, is of importance mainly because of retinal damage. Like cataract, siderosis may be the first sign of an unsuspected foreign body. The early signs of retinal degeneration may be detected by electroretinography or by electro-oculography, which is sometimes more sensitive (Kelsey 1968). Removal of the foreign body even at a late stage may be worth-while, though some continuing deterioration is to be expected from the iron already absorbed. Choroidal rupture, usually concentric with the disc and involving the retina over it, may produce obvious immediate visual loss, but even those ruptures which just miss the macula may give late macular oedema six months to five years after the accident, probably from neovascularization (Smith et al. 1974). Fluorescein angiography might help to detect those likely to progress, and light coagulation might then be indicated. Retinal detachment, as already mentioned, may be a fairly obvious late complication of severe
Proc. roy. Soc. Med. Volume 69 January 1976
2
trauma leading to vitreous hemorrhage, adhesions, and bands which may need intravitreous surgery; but it may follow much more subtle changes. Concussion of the eyeball of the type that produces hmmorrhage into the anterior chamber (traumatic hyphtema) may be accompanied by commotio retinxe with dialysis of its anterior insertion, round holes at the macula or elsewhere, vitreoretinal adhesions producing whitish areas or areas which become white when the sclera is indented ('white with pressure') and vitreous condensation and bands. The situation can be assessed one month after the hyphaema has absorbed (Sellors & Mooney 1973) though the risk continues long after this. Prophylactic light coagulation or cryotherapy is occasionally indicated. Glaucoma can also be a late complication of traumatic hyphoema. Examination of the angle of the anterior chamber shows recession of the angle. Unless the patient is predisposed to glaucoma for some other reason glaucoma probably occurs only if the recession affects more than 180 degrees, and usually more than 270 degrees (Kaufman & Tolpin 1974). The recession can be assessed one month after the accident, but the glaucoma may take some years to develop. Provocative tests for glaucoma might be helpful in prognosis. Defects of accommodation and convergence usually follow head injuries, but occasionally a defect of accommodation may be an unexpected persisting complication of concussion injury when the eye has otherwise apparently fully recovered. A conjunctival implantation cyst may arise at a late stage.
Laser light obeys the laws of optics but differs from that produced by conventional sources in some important aspects. The light is monochromatic, and the absence of chromatic aberration permits focusing to produce spot sizes as smaU as one wavelength. The light is coherent, each wavefront being precisely in phase with its neighbours. The beams of light produced by lasers are usually of small diameter, intense and highly collimated, the energy density within the beam only decreasing slowly with increasing distance. The wavelengths at which lasers emit now stretch from the near ultraviolet to the far infrared and the wavelengths of the most common industrial lasers are: argon (488 nm), helium neon (632.8 nm), ruby (694.3 nm), gallium arsenide (900 nm), neodymium (1060 nm) and carbon dioxide in the far infrared (10.6 tm). Lasers may be subdivided into two groups according to the duration of their output: pulsed and continuous wave (CW). Pulsed lasers may be of two types, normal pulse or Q-switched. Normal pulse lasers deliver their energy in a few milliseconds whereas Q-switched pulses may only last nano (10-9) or pico (10-12) seconds. CW systems normally emit a continuous beam but it is possible for some CW lasers to deliver a train of rapid pulses instead. This is called mode locking; it may be difficult to detect and represents a special hazard (Smart et al. 1970). Each of the special features of laser light has found an industrial application. The ability to focus the intense beams into small spot sizes can produce temperatures of several thousand degrees centigrade. This thermal property is used in the drilling, welding and cutting of a variety of materials including those previously considered to be refractory. Collimation is used by surveyors and engineers to produce a reference beam in tunnel construction, pipe laying or dredger control. The coherent properties are of value in three dimensional photography (holography) precision engineering, communications and data
64
Acknowledgment: I am grateful to Mr Ian Strachan for allowing me to mention some of his patients. REFERENCES
Kaufman J H & Tolpin D W (1974) American Journal ofOphthalmology 78, 648 Kelsey J H (1968) In: Advances in Electrophysiology and Pathology of the Visual System. Ed. E Schmoger. Georg Thieme, Leipzig; pp 19-28 Sellors P J H & Mooney D (1973) British Journal of Ophthalmology 57, 600 Smith R E, KeDey J S & Harbin T S 1974) American Journal of Ophthalmology 77, 650
processing..
The eye is adapted to refract light in the wavelength band 400-1400 nm and bring it to a focus at the retina. At both ends of this band in the near ultraviolet and far infrared all biological tissues are opaque and energy is absorbed in skin, conjunctiva and cornea. With the diversity of wavelengths at which lasers emit, all ocular structures Dr D H Brennan (RAFInstitute of are potentially at risk. Aviation Medicine, Farnborough, Hampshire) The laser properties of beam intensity and collimation which are so valuable to industry Ocular Complications of Industrial Lasers Lasers and their applications have developed constitute the ocular hazard. The small beam rapidly following the introduction of the first divergence ensures that energy densities are ruby laser in 1959. There is now a significant maintained over large distances, and that all or a possibility of accidental ocular damage from the large proportion of the beam is able to enter the eye through the pupil. The focusing mechanism intense beams of industrial lasers.
