Mussa Adil Butt MBBS BSc (Hons)¹

¹The Princess Alexandra Hospital, Harlow, United Kingdom

Introduction

A cataract is the opacification of the lens in the eye. Blindness secondary to cataracts is the leading cause of reversible blindness worldwide. However, this is more prevalent in the developing world due to a lack of access to surgery. In the developed world, surgery to remove a cataract, known as phacoemulsification, is the commonest surgical procedure that is carried out. The UK has an ageing population and therefore the prevalence of age-related cataracts will likely increase. Therefore for ophthalmology trainees in the UK, they must have a baseline knowledge of this condition(1).

Aetiology

The aetiology of age-related cataract formation is thought to be multifactorial. The human lens continues to grow, with the addition of new fibre layers, throughout adult life. Dysregulation of the regular structure of the fibres and accumulation of yellow-brown pigment reduces the transparency and optical clarity of the lens. There are also key extrinsic factors that have been associated with cataract formation including diabetes, smoking and the use of systemic corticosteroids. Cataracts can vary as to which part of the lens is affected and are named accordingly. The three general subtypes of cataract are: cortical, nuclear and subcapsular(2).

Management

The treatment for cataracts is surgery that involves the removal of the cataract and replacement with an artificial intraocular lens. The decision to perform surgery is not dependent on the presence of a cataract alone. As cataract surgery is elective, the indication for surgery is usually a significant reduction in a patient’s vision which affects their quality of life. This is evaluated alongside the risks associated with surgery and the patient’s general health(3).

Cataract surgery can be classified into two types intracapsular and extracapsular. Intracapsular surgery involves the removal of the lens within its intact capsule. This technique is no longer used in the developed world (apart from rare circumstances) as the visual outcomes are worse and the rate of post-operative complications are greater. This method is commonly used in the developed world as there is little reliance on a reliable electricity supply and requires minimal training(2).

Extracapsular surgery involves the removal of the lens from within its capsule. Phacoemulsification is the most modern extracapsular removal method. It involves the use of ultrasound machinery to break down and emulsify the lens into pieces that can be aspirated. This is done through a small incision, approximately 3mm in length. This has two main advantages; there is less alteration to the shape of the cornea and performing the surgery in a closed environment results in less fluctuation of intraocular pressure. Small incision cataract surgery is common in the developing world. An incision of approximately 6mm is made through which the nucleus of the cataract is removed. This incision does not require sutures and therefore it facilitates high volume surgery(2).

Modern outcomes for cataract surgery are a result of reduced intraoperative and postoperative complications alongside significant visual improvements. 85-90% will have 6/12 best-corrected vision following surgery. During small incision surgery, there is a risk of prolapse of the vitreous body into the anterior segments. Furthermore, rupture of the posterior capsule occurs in 2-4% of operations. Specific risks associated with phacoemulsification are related to direct damage to surrounding structures with the probe. Endophthalmitis, intraocular inflammation associated with infection, is the most severe postoperative complication and may result in visual loss. It is treated with intravitreal antibiotics and careful monitoring but may require surgery if the response is not adequate. Posterior capsular opacification is the most common late postoperative complication from cataract surgery. It is commonly treated by laser capsulotomy to create a hole in the poster capsule to allow the passage of light and improve visual outcomes(2).

Femtosecond laser-assisted cataract surgery is a new method used to perform corneal and anterior capsule incisions. It is also used to soften the cataract and therefore results in less phacoemulsification energy and time. It has been shown improved visual outcomes and low complication rates(4).

Conclusion

To conclude, cataract formation is a reversible cause of blindness. As a result of an ageing population, cataract surgery is the commonest surgery performed in the UK. Opthalmology trainees will be required to develop the skills to perform this procedure during their training. Age-related cataracts will affect the majority of those over the age of 65 and therefore newer technologies to help improve safety and visual outcomes for this procedure are required.

References

1. Lam D, Rao SK, Ratra V, Liu Y, Mitchell P, King J, et al. Cataract. Nat Rev Dis Prim 2015 11 [Internet]. 2015 Jun 11 [cited 2021 Dec 2];1(1):1–15. Available from: https://www.nature.com/articles/nrdp201514

2. Allen D, Vasavada A. Cataract and surgery for cataract. BMJ [Internet]. 2006 Jul 13 [cited 2021 Dec 2];333(7559):128–32. Available from: https://www.bmj.com/content/333/7559/128

3. Asbell PA, Dualan I, Mindel J, Brocks D, Ahmad M, Epstein S. Age-related cataract. Lancet [Internet]. 2005 Feb 12 [cited 2021 Dec 2];365(9459):599–609. Available from: http://linkinghub.elsevier.com/retrieve/pii/S0140673605179112

4. Nagy ZZ, McAlinden C. Femtosecond laser cataract surgery. Eye Vis 2015 21 [Internet]. 2015 Jun 30 [cited 2021 Dec 2];2(1):1–8. Available from: https://eandv.biomedcentral.com/articles/10.1186/s40662-015-0021-7