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Purpose Air pollution is associated with chronic diseases of later life. Cataract is the most common cause of blindess globally. It is biologically plausible that cataract risk is increased by pollution exposure. Therefore, the relationship between air pollution and incident cataract surgery was examined. Methods This was a prospective, observational study involving 433,727 UK Biobank participants. Ambient air pollution measures included particulates, nitrogen dioxide (NO 2 ) and nitrogen oxides (NO x ). Outdoor air pollution was estimated based on land use regression models. Participants undergoing cataract surgery in either eye were ascertained via data linkage to the National Health Service procedure statistics. Those undergoing cataract surgery within 1 year of baseline assessment and those reporting cataract at baseline were excluded. Cox proportional hazards models were used to examine the associations between air pollutants and incident cataract surgery, adjusting for sociodemographic and lifestyle factors. Results There were 16,307 incident cases of cataract surgery. Higher exposure to PM 2.5 was associated with a 5% increased risk of incident cataract surgery (per interquartile range [IQR] increase). Compared to the lowest quartile, participants with exposures to PM 2.5 , NO 2 , and NO x in the highest quartile were 14%, 11%, and 9% more likely to undergo cataract surgery, respectively. A continuous exposure-response relationship was observed, with the likelihood of undergoing cataract surgery being progressively higher with greater levels of PM 2.5 , NO 2 , and NO x ( P for trend P < 0.001). Conclusions Although the results of our study showed a 5% increased risk of future cataract surgery following an exposure to PM 2.5 , NO 2 , and NO x , the effect estimates were relatively small. Further research is required to determine if the associations identified are causal.

Sir, Delayed radial keratotomy dehiscence following uneventful phacoemulsification cataract surgery A 73-year-old female was referred with cataracts. Bilateral radial keratotomy (RK) had been performed 9 years previously for high myopia; on her left eye this had been supplemented with astigmatic keratotomies. Best-corrected visual acuities were 6/36 right eye and 6/12 left eye. She had bilateral moderate nuclear sclerotic cataracts. Fundoscopy showed healthy discs with a right epiretinal membrane and normal left macular. She chose to have left cataract surgery following detailed discussion with specific mention of complications associated with previous RK.Routine phacoemulsification cataract extraction was performed under subtenons anaesthesia. The clear corneal main incision was located temporally between RK incisions and was secured at the end of the procedure with a single 10/0 Vicryl suture. She was examined before discharge and had a deep anterior chamber and negative Siedel's test. Acetazolamide 250 mg was given for postoperative IOP prophylaxis.Day one review showed a shallow anterior chamber with two Seidel positive temporal RK incisions. She was taken to theatre and one incision closed with a 10/0 nylon suture and a bandage contact lens inserted (Figure 1). Four months postoperatively her visual acuity is 6/6 with refraction À0.25/À2.00 Â 7.5 CommentPrevious RK not only complicates intraocular lens power selection due to unintentional postoperative hyperopia and postoperative hyperopic shift, 1 but can also reduce corneal tensile strength. RK incision dehiscence has been reported during phacoemulsification cataract surgery 2-4 corneal transplantation 5 and following blunt trauma including car airbag inflation. 6 Previous reports suggest considerable variability in corneal strength following RK. [2][3][4][5][6][7][8] We are aware of three published cases of RK incision rupture during phacoemulsification cataract surgery. Budak et al 2 reported RK incision dehiscence in a patient who had RK 11 months before cataract surgery. This occurred during construction of a 3.0 mm incision that intersected one of the radial incisions. Following suturing of the wound, the remainder of the procedure was uneventful. In the other two cases, RK dehiscence occurred during the phacoemulsification stage. 3,4 In all cases there was very good visual rehabilitation.The reason why delayed RK dehiscence occurred in our patient is not known. The astigmatic keratotomy incisions traversing radial cuts will have further weakened the cornea compared with simple RK. As trauma to the eye is unlikely because the clear shield was only removed at the day one examination, we speculate