The role of dry eye disease in cataract and refractive surgery

Abstract

Dry eye disease (DED) can play an important role in ophthalmic procedures with refractive aims such as those involving the cornea (corneal laser surgery) or the crystalline lens (refractive lensectomy or cataract surgery). This thesis describes the application of a series of minimally to non-invasive diagnostic DED tests recommended by the recent Tear Film & Ocular Society Dry Eye WorkShop II (TFOS DEWS II) to help to improve the understanding of the impact of dryeye on the refractive and visual outcomes in the ophthalmic surgery and the impact of ophthalmic surgery on the ocular surface.Intraocular lens surgery, in particular modern cataract and refractive lens-exchange (RLE) surgery, is the focus of the first section of the thesis. In fact, DED is not only present as a post-operative complication but can also be responsible for sub-optimal refractive and visual outcomes since parts of the pre-operative examination pathway can be influenced by a depleted tear film (e.g. biometry and corneal topography). A literature review suggests little evidence ofthe routine use of advanced tear film assessments in patients undergoing intraocular lens surgery and there is little information on which DED findings are most important to avoid suboptimal clinical outcomes. Studies were carried out to explore the most relevant DED tests as recommended by the TFOS DEWS II. The key findings were that pre-operative DED metrics such as reduced tear meniscus height (<0.20 mm) together with increased DED symptoms measured with Ocular Surface Disease Index (OSDI) (score ≥13) were potentially relevant to increase the chance of having less accurate refraction and poorer visual outcomes after lens surgery. Contrarily, Dry Eye Questionnaire 5-items (DEQ-5), that is a useful tool to evaluate ocular comfort, might be not designed to consider visual function that could potentially be affected by DED or cataract and might be not a good sensitive indicator of the refractive and visual outcomes after lens surgery.In modern corneal refractive surgery, despite numerous publications and studies demonstrating the safety and efficacy in correcting refractive errors such as myopia, hyperopia and astigmatism, post-operative DED is still problematic and of the most common complications after surgery. Recently, newer techniques (e.g. small incision lenticule extraction (SMILE)) have been introduced with the aim of providing excellent visual outcomes whilst overcoming some of the limitations of more established procedures including undesirable alterations to corneal nerve structure and function and DED development. The use of in-vivo confocal microscopy was used to compare corneal nerve structure after SMILE with that seen after traditional laser-assisted in situ keratomileusis (LASIK). The results showed FS-LASIK surgery had more impact on the corneal nerve fibre metrics (up to 75% of reduction) compared to SMILE surgery (up to 23%). Additionally, DED symptoms after FS-LASIK observed a significant two to four-fold increase (OSDI and DEQ-5) where also tear volume significantly decreased after surgery (from 0.32 ± 0.13 to 0.22 ± 0.09 mm).In summary, the research studies detailed in this thesis use a series of advanced diagnostic techniques primarily to understand the role of DED in patients undergoing ophthalmic procedures for refractive and visual indications. They also explore which are the most important tests, in terms of identifying the impact of DED in ophthalmic surgery. Better diagnosis and management of DED in patients undergoing ophthalmic surgery will lead to optimal refractive, visual and patient-reported outcomes.