PURPOSE: To determine the radiation tolerance of the lens of the eye and the incidence of radiation-induced lens changes in patients treated by fractionated supervoltage radiation therapy for orbital tumors. METHODS: Forty patients treated for orbital lymphoma and pseudotumour with tumour doses of 20-40 Gy were studied. The lens was partly shielded using lead cylinders in most cases. The dose to the germinative zone of the lens was estimated by measurements in a tissue equivalent phantom using both film densitometry and thermoluminescent dosimetry. Ophthalmological examination was performed at 6 monthly intervals after treatment. RESULTS: The lead shield was found to reduce the dose to the germinative zone of the lens to between 36-50% of the tumor dose for Cobalt beam therapy, and to between 11-18% for 5 MeV x-rays. Consequently, the len doses were in the range 4.5-30 Gy in 10-20 fractions. Lens opacities first appeared from between 3 and 9 years after irradiation. Impairment of visual acuity ensued in 74% of the patients who developed lens opacities. The incidence of lens changes was strongly dose-related. None was seen after doses of 5 Gy or lower, whereas doses of 16.5 Gy or higher were all followed by lens opacities which impaired visual acuity. The largest number of patients received a maximum lens dose of 15 Gy; in this group the actuarial incidence of lens opacities at 8 years was 57% with visual impairment in 38%. CONCLUSION: The adult lens can tolerate a total dose of 5 Gy during a fractionated course of supervoltage radiation therapy without showing any changes. Doses of 16.5 Gy or higher will almost invariably lead to visual impairment. The dose which causes a 50% probability of visual impairment is approximately 15 Gy.
PURPOSE: To determine the radiation tolerance of the lens of the eye and the incidence of radiation-induced lens changes in patients treated by fractionated supervoltage radiation therapy for orbital tumors. METHODS: Forty patients treated for orbital lymphoma and pseudotumour with tumour doses of 20-40 Gy were studied. The lens was partly shielded using lead cylinders in most cases. The dose to the germinative zone of the lens was estimated by measurements in a tissue equivalent phantom using both film densitometry and thermoluminescent dosimetry. Ophthalmological examination was performed at 6 monthly intervals after treatment. RESULTS: The lead shield was found to reduce the dose to the germinative zone of the lens to between 36-50% of the tumor dose for Cobalt beam therapy, and to between 11-18% for 5 MeV x-rays. Consequently, the len doses were in the range 4.5-30 Gy in 10-20 fractions. Lens opacities first appeared from between 3 and 9 years after irradiation. Impairment of visual acuity ensued in 74% of the patients who developed lens opacities. The incidence of lens changes was strongly dose-related. None was seen after doses of 5 Gy or lower, whereas doses of 16.5 Gy or higher were all followed by lens opacities which impaired visual acuity. The largest number of patients received a maximum lens dose of 15 Gy; in this group the actuarial incidence of lens opacities at 8 years was 57% with visual impairment in 38%. CONCLUSION: The adult lens can tolerate a total dose of 5 Gy during a fractionated course of supervoltage radiation therapy without showing any changes. Doses of 16.5 Gy or higher will almost invariably lead to visual impairment. The dose which causes a 50% probability of visual impairment is approximately 15 Gy.
Authors: J Ivanidze; R A Charalel; I Shuryak; D Brenner; A Pandya; O N Kallas; K Kesavabhotla; A Z Segal; M S Simon; P C Sanelli Journal: AJNR Am J Neuroradiol Date: 2017-01-12 Impact factor: 3.825
Authors: M Cohnen; H-J Wittsack; S Assadi; K Muskalla; A Ringelstein; L W Poll; A Saleh; U Mödder Journal: AJNR Am J Neuroradiol Date: 2006-09 Impact factor: 3.825
Authors: U Lachmund; D Ammann-Rauch; A Forrer; M Grob; C Petralli; L Remonda; T Roeren; K Wilhelm Journal: Ophthalmologe Date: 2005-04 Impact factor: 1.059
Authors: U Lachmund; D Ammann; A Forrer; C Petralli; L Remonda; T Roeren; F Vonmoos; K Wilhelm Journal: Ophthalmologe Date: 2005-04 Impact factor: 1.059
Authors: Steven M Nguyen; Julian Sison; Marjorie Jones; Jesse L Berry; Jonathan W Kim; A Linn Murphree; Vanessa Salinas; Arthur J Olch; Eric L Chang; Kenneth K Wong Journal: Int J Radiat Oncol Biol Phys Date: 2018-12-08 Impact factor: 7.038