Original Article
An abbreviated assessment of ocular exposure to ultraviolet radiation Hugh R Taylor, MD* Beatriz Mufioz, M S t Frank S Rosenthal, PhD$ Sheila West, P h D t
Abstract Individual behaviour has a very large effect on determining the exposure of the eye to solar radiation. To be able to examine the relationship between ocular exposure to ambient ultraviolet radiation and ocular disease, a model was developed previously that assessed cumulative ocular exposure from individual information on work and leisure activities. In this paper, we present a simplified version of the model that uses data on exposure during the middle of the day (9 a.m. to 3 p.m. solar time) during the northern 'summer' months (April to September).The ocular exposure determined by the simplified model is highly correlated with the full model ( r = 0.98) and the simplified model predicts 62% of the total ocular exposure. This model should be useful for future epidemiologic studies of sun exposure and eye disease. Key words: Ocular exposure, sunlight, occupation, ultraviolet radiation.
There has been an increasing interest in the possible harmful effects of sunlight on the eye. Although laboratory and animal studies can provide much *Department of Ophchalmology, The University of Melbourne, Parkville, Victoria, Australia. ?Dana Centerfor Preventive Ophthalmology, The Wilmer Clinic, Johns Hopkins University, Baltimore, Maryland USA. $The School of Health Sciences, Purdue University, West Lafa-vette, Indiana, USA.
useful information in this area, epidemiologic studies are also needed. The key to such epidemiologic investigations is the accurate assessment of individual ocular exposure. Unfortunately, the assessment of individual ocular exposure to solar radiation is neither simple nor straightforward. Some studies have used methods that give a rough approximation of individual ocular exposure by assuming that everyone living in a given area has the same exposure. The exposure for that area could then be simply categorised as being either sunny or less sunny,',2 or the number of sunlight hours could be taken as a more precise m e a ~ u r e .Less ~.~ often, measured or calculated ultraviolet-B (UV-B) radiation levels have been Some improvement in the assessment of individual exposure is obtained by classifying subjects as to whether they have had indoor or outdoor occupation~.'-~ The assessment can be further refined by collecting information about multiple types of recreational exposure and the use of protective devices (hats and sunglasses)'o,'' or by constructing simple exposure history matrices using ambient exposure, years at that location, and hours spent outdoors.'2-'4 Other studies have assessed individual UV-B exposure by using dermal elastosis in exposed facial skin as a personal d o ~ i m e t e r . ' ~ - ' ~ In some elegant studies using manikins, Urbach demonstrated how the UV-B exposure of the face and eyes could vary dramatically with minor changes in the immediate envir~nment."~'~ The importance of individual behaviour, especially the use of hats and eyeglasses, has been demonstrated -
Reprint requests: Professor Hugh R Taylor, University of Melbourne, Department of Ophthalmology, The Royal Victorian Eye and Ear Hospital, 32 Gisborne Street, East Melbourne, Victoria 3002, Australia. Assessment of ocular exposure to ultraviolet radiation
219
Table 1. Interview data used to determine personal Ocular UV-6 e x p o ~ u r e ' ~ Use of glasses or sunglasses Years worn Proportion of time used at work Proportion of time used at leisure Occupational exposure Geographic location Specific hours spent outside Number of days worked per week Specific months worked Type of occupation (over land or water) Use of hat Leisure exposure Geographic location Hours in sunlight Use of hat
with a quantitative personal ocular exposure model which combined interview data with the results of field and laboratory s t u d i e ~ . ' ~ -Model *~ computations showed that over the course of a week the cumulative ocular UV-B exposure of an outdoor worker may be as much as 18 times greater than that received by an indoor worker during their leisure activities However, by protecting their eyes by wearing a brimmed hat and glasses, or sunglasses, the outdoor worker could reduce exposure to only twice that of an unprotected indoor worker. This full model takes into account typical ambient radiation level at each hour of the day for each month of the year.z' Ocular exposure is modified by a month-by-month history of outdoor work schedules, work surfaces, leisure activities, and hat and eyeglass use. As most of ambient UV-B is encountered in the middle of the day in summer, we investigated the usefulness of a shortened assessment of exposure that focused on summer activities. In this report, we present this simplified method of assessing personal ocular exposure to UV-B and compare it to the more exhaustive full model.
Methods During an epidemiologic study of the adverse effects of ocular exposure to sunlight, 838 watermen who work on the Chesapeake Bay in Maryland were examined.22.24 A detailed exposure history from the age of 15 years was taken by trained interviewers 220
(Table 1). Mean hourly ambient UV-B for each month of the year was estimated from published data.25 Modifying factors to correct for seasonal variation in the proportion of ambient UV-B that reaches the eye, surface albedo, and hat and spectacle use had been determined by field measurements. '9.21,26.27 These data were combined into a mathematical model to determine the yearly ocular UV-B exposure by summing the monthly fraction of ambient radiation reaching the eye during work and leisure time.19 These monthly fractions were determined from the fraction of daily ambient exposure during work (or leisure) hours, the ambient level of radiation, the use of spectacles, the ocular ambient exposure ratio corrected for hat use and work surface, and the number of days worked. Yearly ocular exposure was expressed as a fraction of the total ambient radiation in terms of Maryland Sun Years. Yearly exposures could be summed to give a cumulative exposure, averaged to give a mean annual exposure, and so forth. The shortened assessment used the same model but restricted the exposure input to the six hours of 9 a.m. to 3 p.m. solar time (10 a.m. to 4 p.m. summer time) for the six northern 'summer' months, April to September. The Pearson correlation coefficient ( r ) was used to measure the correlation between the 'total' exposure (the full model) and the 'summer' exposure (the shortened model). A logistic regression model was used to measure the association of 'summer' exposure and the presence of cortical opacities after controlling by age. This analysis followed the analysis previously described for total exposure.24
Results A strong correlation was seen between summer and total cumulative UV-B exposures (Figure 1). The strength of this correlation did not change with age, being the same for those in each decade from the fourth to the ninth. The summer exposure was, on average, 62.8% ( f 8.5%) that of the total exposure. This proportion was the same for each age group. Looked at another way, the median summer exposure was 62.0% of the total exposure, the interquartile range was 57.8% to 67.8%. The effect of occupation on the ratio between summer and total exposure was examined. Although all subjects held professional waterman licenses, many had worked at a number of other jobs. Subjects were categorised by the job they had Australian and New Zealand Journal of Ophthalmology 1992; 20(3)
+
0
4
3
2
1
Summer Cumulative UV-B Exposure Figure 1 Correlation between summer cumulative ocular UV-B exposure and total cumulative ocular UV-B exposure both expressed in Maryland Sun Years units ( r = 0.98).
+
+
+
+
+
+ + +
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Ratio of Summer to Total Cumulative Exposure Figure 2 Distribution ofsummer cumulative ocular UV-B exposure as a ratio of total cumulative ocular UV-B exposure by age in years. Assessment of ocular exposure to ultraviolet radiation
22 1
held the longest.23Part-time watermen were defined as those who worked on the water for one season and had another job for the rest of that year. There was no difference in the ratio of summer to total exposure between outside workers (66.6% f6.8%), inside workers (68.6% f9.670)) and part-time watermen (64.6% k 10.17'0). However, the ratio was somewhat lower for the full-time watermen (59.0% f5.8%). Finally, to test the validity of the shortened assessment, the relationship between cortical lens opacities and summer cumulative UV-B exposure was tested. Logistic regression analysis showed this relationship to be statistically significant (regression coefficient 0.75 f0.36). This result was not different from that obtained when the total exposure model was used as reported previously (regression coefficient 0.70 k 0.35).25
Discussion Having developed a full mathematical model to ascertain individual ocular exposure to UV-B,*' we now describe a simplification of that model that should be of greater practical use. In the northern hemisphere, 62% of the total ambient UV-B radiation is present in the six hours during the middle of the day (9 a.m. to 3 p.m. solar time) in the six months April to September.21 By shortening the exposure model to only include these hours, one need take an exposure history for only one-quarter of the daytime hours each year instead of for all hours. Our experience suggests that it takes as much time to collect data about exposures at one time of year as another. The shortened assessment not only means that data collection can be simplified, but the data files and construction of the exposure model are also simplified. As expected, the shortened exposure was highly correlated with the total exposure. On average, the shortened exposure was 63% of the total exposure and for half of the subjects lay between 58% and 68%. Although this difference may be important if one intended to assess the absolute ocular exposure, the consistent underestimation of ocular exposure should have little impact in studies that seek to categorise subjects by relative dose. The underestimation of exposure was consistent across age groups and also across occupational groups, with the exception of the full-time watermen. The latter discrepancy is probably due to the unusual working hours followed by most watermen who work on the water from before dawn until the early afternoon.23 Thus, watermen receive a larger 222
proportion of their exposure before solar noon than after solar noon. However, the stability across the other occupational groups, including the part-time watermen, suggests that this method would have general utility. The shortened assessment of ocular exposure focuses attention to the period of time when most UV-B exposure occurs and reduces to one-quarter the amount of time that needs to be covered in creating an exposure history. It should prove usehl for future studies assessing ocular exposure.
Acknowledgements This work was funded in part by NEI Grant # EY004547 and NIH Shared Instrument Grant #S-10-RR04060. References 1. van Heyningen R. The human lens: I. A comparison of cataracts extracted in Oxford (England) and Shikarpur (W. Pakistan). Exp Eye Res 1972;13:136-47. 2. Mao WS, H u TS. An epidemiologic survey of senile cataract in China. Chin Med J 1982;95:813-18. 3. Hiller R, Giacometti L, Yuen K. Sunlight and cataract: an epidemiologic investigation. Am J Epidemiol 1977;105: 450-9. 4. Brilliant LB, Grasset NC, Pokhrel RP, Kolstad A, Lepkowski JM, Brilliant GE, er al. Associations among cataract prevalence, sunlight hours, and altitude in the Himalayas. Am J Epidemiol 1983;118:250-64. 5. Taylor HR. The environment and the lens. Br J Ophthalmol 980;64:303-10. 6. Hiller R, Sperduto RD, Ederer F. Epidemiologic associations with nuclear, cortical, and posterior subcapsular cataracts. Am J Epidemiol 1986;124:916-25. 7. Zigman S, Datiles M, Torczynski E. Sunlight and human cataracts. Invest Ophthalmol Vis Sci 1979;18:462-7. 8. Mohan M, Sperduto RD, Angra SK, Milton RC, Mathur RL, Underwood BA, et al. India-US caseconrrol study of age-related cataracts. Arch Ophthalmol 1989;107:670-6. 9. Hyman LG, Lilienfeld AM, Ferris FL, Fine SL. Senile macular degeneration: a case-control study. Am J Epidemiol 1983;118:213-27. 10. Tucker MA, Shields JA, Hartge P, Augsburger J, Hoover RN, Fraumeni JF. Sunlight exposure as risk factor for intraocular malignant melanoma. N Engl J Med 1985;313:789-92. 1. Leske MC, Chylack LT, Wu SY. The Lens opacities casecontrol study - risk factors for cataract. Arch Ophthalmol 1991; 109~244-5 1. 2. Collman GW, Shore DL, Shy CM, Checkoway H, Luria AS. Sunlight and other risk factors for cataracts: an epidemiologic study. Am J Public Health 1988;78:1459-62. 3. Dolezal JM, Perkins ES, Wallace RB. Sunlight, skin sensitivity, and senile cataract. Am J Epidemiol 1989; 129559-68. 14. Seddon JM, Gragoudas ES, Glynn RJ, Egan KM, Albert DM, Blitzer PH. Host factors, UV radiation, and risk of uveal melanoma - a case control study. Arch Ophthalmol 1990; 108:1274-80. Australian and New Zealand Journal of Ophthalmology 1992;20(3)
15. Cameron LL. Association of senile lens and dermal changes with cumulative ultraviolet exposure. PhD Dissertation. Baltimore, Johns Hopkins University, 1985. 16. Blumenkranz MS, Russell SR, Robey MG, KottBlumenkranz R, Penneys N. Risk factors in age-related maculopathy complicated by choridal neovascularization. Ophthalmology 1986;93:552-8. 17. Urbach F. Geographic pathology ofskin cancer. In: Urbach F, ed. The Biologic Effects of Ultraviolet Radiation (With Emphasis on the Skin). Oxford: Pergamon Press, 1969~635-50. 18. Rosenthal FS, Safran M. Taylor HR. The ocular dose of ultraviolet radiation from sunlight exposure. Photochem Photobiol 1985;42:163-171. 19. Rosenthal FS, Phoon C, Bakalian AE, Taylor HR. The ocular dose of ultraviolet radiation in outdoor workers. Invest Ophthalmol Vis Sci 1988;29:649-56. 20. Rosenthal FS, Bakalian AE, Phoon C, West S, Taylor HR. Senile eye changes: determination of ocular exposure to ultraviolet light. Invest Ophthalmol Vis Sci 1987;28(suppl):397.
21. Rosenthal FS, West SK, Mufioz B, Emmett EA, Strickland PT, Taylor HR. Ocular and facial skin exposure to ultraviolet radiation in sunlight: a personal exposure model with application to a worker population. Health Physics 1991;61:77-86. 22. Taylor HR. Ultraviolet radiation and the eye: an epidemiologic study. Trans Am Ophthalmol SOC1989;87:802-53. 23. Taylor HR. The biological effects of UV-B on the eye. Photochem Photobiol 1989;50:489-92. 24. Taylor HR, West SK, Rosenthal FS, Murioz B, Newland HS, Abbey H, eta/. Effect of ultraviolet radiation on cataract formation. N Engl J Med 1988;319:1429-33. 25. Scotto J, Fears TR, Gori G. Measurements of ultraviolet radiation in the United States and comparisons with skin cancer data. Bethesda, US Department of Health, Education, and Welfare, National Cancer Institute, 1977. 26. Rosenthal FS, Bakalian AE, Taylor HR. The effect of prescription eyewear on ocular exposure to ultraviolet radiation. Am J Public Health 1986;76:1216-20. 27. Rosenthal FS, Bakalian AE, Changqi L, Taylor HR. The effect of sunglasses on ocular exposure to ultraviolet radiation. Am J Pub Health 1988;78:72-4.
Nothing ever remains the same. Perhaps its just as well in many cases. TAYLOR & TREFRY have been the vanguard in improving the quality of ocular prostheses in Australia and we intend to stay the leaders. We offer your patients our 40 years of experience in the manufacture of ocular prostheses with the following services:-
REFORM ACRYLIC
HAPTIC SHELLS
Assessment of ocular exposure to ultraviolet radiation
HOLLOW BODY FULLY MOULDED EYES (PAT)
I
CONFORMERS
I
223
An abbreviated assessment of ocular exposure to ultraviolet radiation Hugh R Taylor, MD* Beatriz Mufioz, M S t Frank S Rosenthal, PhD$ Sheila West, P h D t
Abstract Individual behaviour has a very large effect on determining the exposure of the eye to solar radiation. To be able to examine the relationship between ocular exposure to ambient ultraviolet radiation and ocular disease, a model was developed previously that assessed cumulative ocular exposure from individual information on work and leisure activities. In this paper, we present a simplified version of the model that uses data on exposure during the middle of the day (9 a.m. to 3 p.m. solar time) during the northern 'summer' months (April to September).The ocular exposure determined by the simplified model is highly correlated with the full model ( r = 0.98) and the simplified model predicts 62% of the total ocular exposure. This model should be useful for future epidemiologic studies of sun exposure and eye disease. Key words: Ocular exposure, sunlight, occupation, ultraviolet radiation.
There has been an increasing interest in the possible harmful effects of sunlight on the eye. Although laboratory and animal studies can provide much *Department of Ophchalmology, The University of Melbourne, Parkville, Victoria, Australia. ?Dana Centerfor Preventive Ophthalmology, The Wilmer Clinic, Johns Hopkins University, Baltimore, Maryland USA. $The School of Health Sciences, Purdue University, West Lafa-vette, Indiana, USA.
useful information in this area, epidemiologic studies are also needed. The key to such epidemiologic investigations is the accurate assessment of individual ocular exposure. Unfortunately, the assessment of individual ocular exposure to solar radiation is neither simple nor straightforward. Some studies have used methods that give a rough approximation of individual ocular exposure by assuming that everyone living in a given area has the same exposure. The exposure for that area could then be simply categorised as being either sunny or less sunny,',2 or the number of sunlight hours could be taken as a more precise m e a ~ u r e .Less ~.~ often, measured or calculated ultraviolet-B (UV-B) radiation levels have been Some improvement in the assessment of individual exposure is obtained by classifying subjects as to whether they have had indoor or outdoor occupation~.'-~ The assessment can be further refined by collecting information about multiple types of recreational exposure and the use of protective devices (hats and sunglasses)'o,'' or by constructing simple exposure history matrices using ambient exposure, years at that location, and hours spent outdoors.'2-'4 Other studies have assessed individual UV-B exposure by using dermal elastosis in exposed facial skin as a personal d o ~ i m e t e r . ' ~ - ' ~ In some elegant studies using manikins, Urbach demonstrated how the UV-B exposure of the face and eyes could vary dramatically with minor changes in the immediate envir~nment."~'~ The importance of individual behaviour, especially the use of hats and eyeglasses, has been demonstrated -
Reprint requests: Professor Hugh R Taylor, University of Melbourne, Department of Ophthalmology, The Royal Victorian Eye and Ear Hospital, 32 Gisborne Street, East Melbourne, Victoria 3002, Australia. Assessment of ocular exposure to ultraviolet radiation
219
Table 1. Interview data used to determine personal Ocular UV-6 e x p o ~ u r e ' ~ Use of glasses or sunglasses Years worn Proportion of time used at work Proportion of time used at leisure Occupational exposure Geographic location Specific hours spent outside Number of days worked per week Specific months worked Type of occupation (over land or water) Use of hat Leisure exposure Geographic location Hours in sunlight Use of hat
with a quantitative personal ocular exposure model which combined interview data with the results of field and laboratory s t u d i e ~ . ' ~ -Model *~ computations showed that over the course of a week the cumulative ocular UV-B exposure of an outdoor worker may be as much as 18 times greater than that received by an indoor worker during their leisure activities However, by protecting their eyes by wearing a brimmed hat and glasses, or sunglasses, the outdoor worker could reduce exposure to only twice that of an unprotected indoor worker. This full model takes into account typical ambient radiation level at each hour of the day for each month of the year.z' Ocular exposure is modified by a month-by-month history of outdoor work schedules, work surfaces, leisure activities, and hat and eyeglass use. As most of ambient UV-B is encountered in the middle of the day in summer, we investigated the usefulness of a shortened assessment of exposure that focused on summer activities. In this report, we present this simplified method of assessing personal ocular exposure to UV-B and compare it to the more exhaustive full model.
Methods During an epidemiologic study of the adverse effects of ocular exposure to sunlight, 838 watermen who work on the Chesapeake Bay in Maryland were examined.22.24 A detailed exposure history from the age of 15 years was taken by trained interviewers 220
(Table 1). Mean hourly ambient UV-B for each month of the year was estimated from published data.25 Modifying factors to correct for seasonal variation in the proportion of ambient UV-B that reaches the eye, surface albedo, and hat and spectacle use had been determined by field measurements. '9.21,26.27 These data were combined into a mathematical model to determine the yearly ocular UV-B exposure by summing the monthly fraction of ambient radiation reaching the eye during work and leisure time.19 These monthly fractions were determined from the fraction of daily ambient exposure during work (or leisure) hours, the ambient level of radiation, the use of spectacles, the ocular ambient exposure ratio corrected for hat use and work surface, and the number of days worked. Yearly ocular exposure was expressed as a fraction of the total ambient radiation in terms of Maryland Sun Years. Yearly exposures could be summed to give a cumulative exposure, averaged to give a mean annual exposure, and so forth. The shortened assessment used the same model but restricted the exposure input to the six hours of 9 a.m. to 3 p.m. solar time (10 a.m. to 4 p.m. summer time) for the six northern 'summer' months, April to September. The Pearson correlation coefficient ( r ) was used to measure the correlation between the 'total' exposure (the full model) and the 'summer' exposure (the shortened model). A logistic regression model was used to measure the association of 'summer' exposure and the presence of cortical opacities after controlling by age. This analysis followed the analysis previously described for total exposure.24
Results A strong correlation was seen between summer and total cumulative UV-B exposures (Figure 1). The strength of this correlation did not change with age, being the same for those in each decade from the fourth to the ninth. The summer exposure was, on average, 62.8% ( f 8.5%) that of the total exposure. This proportion was the same for each age group. Looked at another way, the median summer exposure was 62.0% of the total exposure, the interquartile range was 57.8% to 67.8%. The effect of occupation on the ratio between summer and total exposure was examined. Although all subjects held professional waterman licenses, many had worked at a number of other jobs. Subjects were categorised by the job they had Australian and New Zealand Journal of Ophthalmology 1992; 20(3)
+
0
4
3
2
1
Summer Cumulative UV-B Exposure Figure 1 Correlation between summer cumulative ocular UV-B exposure and total cumulative ocular UV-B exposure both expressed in Maryland Sun Years units ( r = 0.98).
+
+
+
+
+
+ + +
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Ratio of Summer to Total Cumulative Exposure Figure 2 Distribution ofsummer cumulative ocular UV-B exposure as a ratio of total cumulative ocular UV-B exposure by age in years. Assessment of ocular exposure to ultraviolet radiation
22 1
held the longest.23Part-time watermen were defined as those who worked on the water for one season and had another job for the rest of that year. There was no difference in the ratio of summer to total exposure between outside workers (66.6% f6.8%), inside workers (68.6% f9.670)) and part-time watermen (64.6% k 10.17'0). However, the ratio was somewhat lower for the full-time watermen (59.0% f5.8%). Finally, to test the validity of the shortened assessment, the relationship between cortical lens opacities and summer cumulative UV-B exposure was tested. Logistic regression analysis showed this relationship to be statistically significant (regression coefficient 0.75 f0.36). This result was not different from that obtained when the total exposure model was used as reported previously (regression coefficient 0.70 k 0.35).25
Discussion Having developed a full mathematical model to ascertain individual ocular exposure to UV-B,*' we now describe a simplification of that model that should be of greater practical use. In the northern hemisphere, 62% of the total ambient UV-B radiation is present in the six hours during the middle of the day (9 a.m. to 3 p.m. solar time) in the six months April to September.21 By shortening the exposure model to only include these hours, one need take an exposure history for only one-quarter of the daytime hours each year instead of for all hours. Our experience suggests that it takes as much time to collect data about exposures at one time of year as another. The shortened assessment not only means that data collection can be simplified, but the data files and construction of the exposure model are also simplified. As expected, the shortened exposure was highly correlated with the total exposure. On average, the shortened exposure was 63% of the total exposure and for half of the subjects lay between 58% and 68%. Although this difference may be important if one intended to assess the absolute ocular exposure, the consistent underestimation of ocular exposure should have little impact in studies that seek to categorise subjects by relative dose. The underestimation of exposure was consistent across age groups and also across occupational groups, with the exception of the full-time watermen. The latter discrepancy is probably due to the unusual working hours followed by most watermen who work on the water from before dawn until the early afternoon.23 Thus, watermen receive a larger 222
proportion of their exposure before solar noon than after solar noon. However, the stability across the other occupational groups, including the part-time watermen, suggests that this method would have general utility. The shortened assessment of ocular exposure focuses attention to the period of time when most UV-B exposure occurs and reduces to one-quarter the amount of time that needs to be covered in creating an exposure history. It should prove usehl for future studies assessing ocular exposure.
Acknowledgements This work was funded in part by NEI Grant # EY004547 and NIH Shared Instrument Grant #S-10-RR04060. References 1. van Heyningen R. The human lens: I. A comparison of cataracts extracted in Oxford (England) and Shikarpur (W. Pakistan). Exp Eye Res 1972;13:136-47. 2. Mao WS, H u TS. An epidemiologic survey of senile cataract in China. Chin Med J 1982;95:813-18. 3. Hiller R, Giacometti L, Yuen K. Sunlight and cataract: an epidemiologic investigation. Am J Epidemiol 1977;105: 450-9. 4. Brilliant LB, Grasset NC, Pokhrel RP, Kolstad A, Lepkowski JM, Brilliant GE, er al. Associations among cataract prevalence, sunlight hours, and altitude in the Himalayas. Am J Epidemiol 1983;118:250-64. 5. Taylor HR. The environment and the lens. Br J Ophthalmol 980;64:303-10. 6. Hiller R, Sperduto RD, Ederer F. Epidemiologic associations with nuclear, cortical, and posterior subcapsular cataracts. Am J Epidemiol 1986;124:916-25. 7. Zigman S, Datiles M, Torczynski E. Sunlight and human cataracts. Invest Ophthalmol Vis Sci 1979;18:462-7. 8. Mohan M, Sperduto RD, Angra SK, Milton RC, Mathur RL, Underwood BA, et al. India-US caseconrrol study of age-related cataracts. Arch Ophthalmol 1989;107:670-6. 9. Hyman LG, Lilienfeld AM, Ferris FL, Fine SL. Senile macular degeneration: a case-control study. Am J Epidemiol 1983;118:213-27. 10. Tucker MA, Shields JA, Hartge P, Augsburger J, Hoover RN, Fraumeni JF. Sunlight exposure as risk factor for intraocular malignant melanoma. N Engl J Med 1985;313:789-92. 1. Leske MC, Chylack LT, Wu SY. The Lens opacities casecontrol study - risk factors for cataract. Arch Ophthalmol 1991; 109~244-5 1. 2. Collman GW, Shore DL, Shy CM, Checkoway H, Luria AS. Sunlight and other risk factors for cataracts: an epidemiologic study. Am J Public Health 1988;78:1459-62. 3. Dolezal JM, Perkins ES, Wallace RB. Sunlight, skin sensitivity, and senile cataract. Am J Epidemiol 1989; 129559-68. 14. Seddon JM, Gragoudas ES, Glynn RJ, Egan KM, Albert DM, Blitzer PH. Host factors, UV radiation, and risk of uveal melanoma - a case control study. Arch Ophthalmol 1990; 108:1274-80. Australian and New Zealand Journal of Ophthalmology 1992;20(3)
15. Cameron LL. Association of senile lens and dermal changes with cumulative ultraviolet exposure. PhD Dissertation. Baltimore, Johns Hopkins University, 1985. 16. Blumenkranz MS, Russell SR, Robey MG, KottBlumenkranz R, Penneys N. Risk factors in age-related maculopathy complicated by choridal neovascularization. Ophthalmology 1986;93:552-8. 17. Urbach F. Geographic pathology ofskin cancer. In: Urbach F, ed. The Biologic Effects of Ultraviolet Radiation (With Emphasis on the Skin). Oxford: Pergamon Press, 1969~635-50. 18. Rosenthal FS, Safran M. Taylor HR. The ocular dose of ultraviolet radiation from sunlight exposure. Photochem Photobiol 1985;42:163-171. 19. Rosenthal FS, Phoon C, Bakalian AE, Taylor HR. The ocular dose of ultraviolet radiation in outdoor workers. Invest Ophthalmol Vis Sci 1988;29:649-56. 20. Rosenthal FS, Bakalian AE, Phoon C, West S, Taylor HR. Senile eye changes: determination of ocular exposure to ultraviolet light. Invest Ophthalmol Vis Sci 1987;28(suppl):397.
21. Rosenthal FS, West SK, Mufioz B, Emmett EA, Strickland PT, Taylor HR. Ocular and facial skin exposure to ultraviolet radiation in sunlight: a personal exposure model with application to a worker population. Health Physics 1991;61:77-86. 22. Taylor HR. Ultraviolet radiation and the eye: an epidemiologic study. Trans Am Ophthalmol SOC1989;87:802-53. 23. Taylor HR. The biological effects of UV-B on the eye. Photochem Photobiol 1989;50:489-92. 24. Taylor HR, West SK, Rosenthal FS, Murioz B, Newland HS, Abbey H, eta/. Effect of ultraviolet radiation on cataract formation. N Engl J Med 1988;319:1429-33. 25. Scotto J, Fears TR, Gori G. Measurements of ultraviolet radiation in the United States and comparisons with skin cancer data. Bethesda, US Department of Health, Education, and Welfare, National Cancer Institute, 1977. 26. Rosenthal FS, Bakalian AE, Taylor HR. The effect of prescription eyewear on ocular exposure to ultraviolet radiation. Am J Public Health 1986;76:1216-20. 27. Rosenthal FS, Bakalian AE, Changqi L, Taylor HR. The effect of sunglasses on ocular exposure to ultraviolet radiation. Am J Pub Health 1988;78:72-4.
Nothing ever remains the same. Perhaps its just as well in many cases. TAYLOR & TREFRY have been the vanguard in improving the quality of ocular prostheses in Australia and we intend to stay the leaders. We offer your patients our 40 years of experience in the manufacture of ocular prostheses with the following services:-
REFORM ACRYLIC
HAPTIC SHELLS
Assessment of ocular exposure to ultraviolet radiation
HOLLOW BODY FULLY MOULDED EYES (PAT)
I
CONFORMERS
I
223
