Advances in Cataract Surgery For Improved Outcomes

Cataracts occur when the natural crystalline lens becomes opaque, leading to impairment of vision. It can be caused by a number of different conditions including trauma, but the most common is aging.¹

In 2019, in Australia, Medicare reported over 180,000 cataract surgeries were completed, and that over 1.7 million procedures have been performed in the past 10 years.² Cataract surgery is one of the most commonly performed procedures worldwide and has changed immensely over time. Globally, cataracts are responsible for 65.2 million of the estimated 2.2 billion people who have vision impairment.³

Cataract surgery is one the most commonly performed procedures worldwide and has changed immensely over time

The earliest known method for cataract treatment is ‘couching’. Couching dates back to the 5th century BC⁴ where a needle was used to dislodge the lens out of the visual axis. Couching is still performed in some countries presently,⁵ despite the high risk of losing sight and unfavourable results. A minority of patients will be able to see light and detect movement following the procedure but over 70% are left blind.⁶

A French surgeon, Jacques Daviel, performed the first true extracapsular cataract extraction (ECCE) in 1747. This involved an incision over 10mm, puncturing the lens capsule, followed by extraction of the lens cortex.⁴ Early surgery was more successful than couching but postoperative complications were still common with retained lens fragments, poor wound healing and infection.⁷

In 1961, the development of a cryoprobe by a Polish surgeon, Tadeusz Krwawicz, was used to remove the lens in a procedure called intracapsular cataract extraction (ICCE).⁸ A major shortcoming of the ICCE technique was the removal of the entire lens, leading to an increase in the risk of blinding complications such as retinal detachment, macular oedema and corneal decompensation.⁴

Developments in surgical instrumentation and techniques saw the re-emergence of ECCE in the 1970s and the development of manual small incision cataract surgery (MSICS) where a small (in comparison to the traditional ECCE wound) was created and the lens cortex removed. A study comparing modern day ECCE to MSICS found that MSICS resulted in less complications and better visual outcomes.⁹

Modern day cataract surgery came with the introduction of phacoemulsification developed by American ophthalmologist, Charles Kelmann.¹⁰ By using an ultrasound machine, he was able to emulsify and aspirate the lens through a small incision. The introduction of ophthalmic viscosurgical devices also greatly enhanced the development of cataract surgery.

In 2008, Zoltan Nagy used the femtosecond laser to create the anterior capsulotomy and fragment the lens, reporting a capsulorhexis that was more accurate than a manually created one. He also reported a reduction in phacoemulsification time of 43% and power of 51% in the laser assisted cataract surgery compared to without laser.¹¹ 

There are a number of studies comparing the clinical results of laser assisted cataract surgery to manual cataract surgery, which found minimal difference in visual outcome and clinical results.^12,13 However, the study by H. Roberts et al found that the laser assisted cataract surgeries resulted in a clinically significant reduction in posterior capsular rupture,¹² which may reduce the need for vitrectomy.¹⁴

 ALIGNMENT SYSTEMS

The introduction of the alignment systems, allowing for toric intraocular lens (IOL) alignment without the traditional method of manually marking the eye on a silt lamp or freehand on the conjunctiva, aimed to improve toric lens alignment accuracy.¹⁵ 

Studies report that the markerless alignment systems are as good as slit lamp marking or better, which can reduce the amount of postoperative astigmatism.¹⁶ R Varsits et al, found that the deviation in patients, where toric lenses were aligned using a markerless system, was within 0.52 degrees of the targeted axis.¹⁵ 

Intraoperative aberrometry (IA) allows for intraocular lens calculation once the cataract has been removed. Prior to the introduction of this technology, dense cataracts made it difficult to obtain accurate and reliable axial length measurements to allow for accurate lens planning, increasing the risk of postoperative refractive surprises. A retrospective analysis of over 32,000 eyes found that IA calculations outperformed conventional lens preoperative calculations.¹⁷

MG Woodcock et al, randomised 130 patients to receive intraoperative aberrometry measurements and conventional biometry with toric lens calculations. They found that the percentage of patients with 0.50 dioptres or less of astigmatism in the IA group was higher than those in the conventional group at one month (0.29 vs. 0.36).¹⁸

Surgeons and patients now have access to technology all aimed at improving surgical outcomes and optimising the predicted postoperative vision and refraction.

IOL OPTIONS

Aside from improvements and developments in technology aimed at refining the preoperative and intraoperative process, there has been a lot of development and changes in the field of intraocular lenses (IOLs). There is now a wide array of lens options including monofocal, multifocal and extended depth of focus lenses.

Intraocular lenses were developed when English ophthalmologist Harold Ridley realised that polymethyl methacrylate (PMMA) splinters that entered a pilot’s eye remained relatively inert in the eye. With Rayner, he developed the first intraocular lens that was implanted in 1949.¹⁹ A major pitfall of the PMMA IOLs was their rigidity, which meant that the required surgical wound was still rather large.

In the 1950s, foldable IOLs were developed and in 1978, the first silicone IOL was implanted by Kai Yi Zhou.²⁰ 

Monofocal IOLs 

Monofocal IOLs provide patients with the correction of a single focus. This is most often used to correct their distance vision, resulting in the need of spectacle assistance in the intermediate to near range. Comparison of spheric vs. aspheric lenses found that aspheric lenses gave significantly better visual function.²¹ Prior to their introduction, lenses would introduce positive spherical aberrations into the visual system.

Multifocal Lenses 

Multifocal lenses were designed to provide patients with intermediate and near vision while attempting to minimise disruption to the distance vision. There are two major types of multifocal IOLs, which include diffractive and refractive multifocal lenses.

Diffractive multifocal IOLs are designed with concentric rings, alternately arranged, to refract the light entering to focus on different points, allowing multifocality. The spacing between rings and step heights can vary between manufacturers.

Refractive multifocal IOLs, including bifocal IOLs, have multiple zones of refraction, which project two or more images, or annular zones of alternating images. This relies on pupil size to visualise the appropriate image at the appropriate distance.

Regardless of the design, multifocal lenses are designed to allow patients multifocality, however they can cause haloes, glare and unwanted visual phenomenon. These visual disturbances can decrease over time due to neuro-adaptation.²² 

Despite the visual phenomenon, patients who have multifocal IOLs implanted still report a high level of satisfaction. A prospective randomised trial comparing three different multifocal lenses by Alio JL et al, found that haloes were reported in 40–50% of subjects, yet patient satisfaction was still very high at 88% at one month post operatively and 94% at six months. Over 93% of patients would opt to have the same lens if they could choose again.²³

Patient selection and counselling are key factors in determining if a patient is suitable for multifocal IOLs.

Extended Depth of Focus IOLs 

Extended Depth of Focus lenses (EDOF) have recently increased in popularity. Instead of creating multiple focus points or images, these IOLs aim to elongate a single point of focus and therefore increase the range of focus. The aim of these lenses was often to improve on the lack of intermediate and near vision of monofocal lenses while reducing the risk and amount of unwanted visual phenomenon, which can come with multifocal IOLs, thereby improving quality of vision and satisfaction. EDOF lenses are also available in diffractive and refractive designs. It was found that the diffractive lenses were resistant to chromatic effects but studies to compare whether one type of lens results in less unwanted visual phenomenon or not has yet to be studied.²⁴

BLENDED OPTIONS

With the increase in availability of multifocal lenses catering for different distances, there is also the ability to provide patients with a mild version of monovision by implanting lenses with different reading addition in each eye. Most commonly, this may involve a larger add in the non-dominant eye and a smaller add in the dominant eye. Alternatively, this can also be achieved by targeting myopia in the non-dominant eye and emmetropia in the dominant eye.

D Breyer et al presented a paper comparing two groups of patients where group one had both eyes implanted with a +1.50D add refractive bifocal IOL, and group two had the dominant eye with the +1.50D add and the non dominant eye with the +3.00 add. They found that binocular uncorrected distance vision was 0.04 in group one versus 0.2 in group two.²⁵ 

A study by Sandoval HP et al, randomised patients to have EDOF lenses bilaterally implanted but targeted the non-dominant eye to -0.50; much like a mini monovision rather than emmetropia. The second group was implanted to have their EDOF lenses targeted for emmetropia. It was found that the binocular uncorrected distance vision was comparable in both groups (-0.03 vs. -0.01 P0.33 in the mini monovision group) but the binocular uncorrected near vision was statistically significantly worse in the emmetropia group (0.25 vs. 0.19 P=0.03).²⁶

ADVANCED MONOFOCALS

Another IOL recently released in 2019 is a monofocal lens where the anterior surface has a continuous change in power from periphery to the centre to improve intermediate vision without compromising the distance vision, while keeping photic phenomenon to a minimum. This lens may become an option that sits between a monofocal and an EDOF IOL.

Couching is still performed in some countries presently,⁵ despite the high risk of losing sight and unfavourable results

This new IOL is based on the design of a cornea inlay to improve unaided reading vision for presbyopes in the non-dominant eye. It also uses the pinhole effect. This small aperture IOL, developed from the cornea inlay, was designed to be implanted in the non-dominant eye to improve reading vision with the aim to minimally disrupt distance vision. The IOL has a 3.23mm opaque disc with a 1.36mm central aperture.

M Shajari et al used this IOL in a cohort of 17 patients with corneal irregularities due to keratoconus, penetrating keratoplasty, radial keratectomy and scarring following ocular trauma. They found that uncorrected distance vision improved from 0.37} 0.09 to 0.19}0.06. The cohort also reported improvement in quality of life with less difficulty under reduced optical phenomena conditions.²⁷ 

Accommodating IOLs 

In the quest for a presbyopic solution in cataract surgery, accommodating IOLs were also developed. These IOLs use different strategies to change focus and allow for improved near vision following implantation.

Single focus position changing IOLs relied on anterior axial movement of the IOL during accommodation but its effect can be obstructed by the fibrosis of the capsular bag following cataract removal. It is also compounded by studies that the accommodative amplitude achieved may be due to pseudo accommodative means such as pupil constriction, high order aberrations and lens tilt.^28,29

Dual focus position changing IOLs rely on a combination of the ciliary muscle and miosis to shift components of the IOL to simulate accommodation. Reported results were variable with one randomised prospective study demonstrating minimal difference between a dual focus position changing IOL and a single focus position changing IOL.³⁰

Position changing IOLs report that they can provide up to one dioptre of accommodation, which might not be sufficient for comfortable reading at 40cm.³¹ 

Patient selection and counselling are key factors in determining if a patient is suitable for multifocal IOLs

IOLS IN DEVELOPMENT

A number of shape changing IOLs are also in development, which use pumps and shunts to move fluid around, thereby changing the shape of the IOL, which is implanted into the capsular bag. Movement of the ciliary body then controls this during accommodation. Pilot studies of these lenses report accommodation achieved between 1.2 to 2.7D.³²

Another novel lens in development uses electrical control of the refractive index via a liquid crystal inside the IOL. It is designed to have a monofocal IOL with an aspheric central optic for distance and intermediate vision. A smart diffractive liquid crystal is activated for near vision. Microsensors are used to detect the change in light, which is triggered due to accommodative miosis, causing the liquid crystal to change its focusing power. The IOL is powered by lithium ion power cells, which are charged weekly by an inductive charging element.³² 

A concept that has never left researchers and developers is that of being able to ‘fill’ the capsular bag after lens removal with a polymer that would mimic the natural process of accommodation to change the lens shape. The challenges posed in this research involve finding a technique and material that will not leak or cause capsular opacification, is adjustable to change the volume during and after surgery, and also allows a high quality retinal image to be projected during accommodation but also when not accommodating.

REFRACTIVE PREDICTABILITY

Perhaps also often forgotten is the quest for refractive predictability. Despite the technology currently available that is designed to improve lens measurement, calculation, alignment and lens positioning precision, there is still the hunt for postoperative predictability and accuracy. In 2018, Lundstrom et al, analysed 282,811 cataract extractions and found that the biometry prediction error of }0.50D was 72.7%.³³ 

Adjustable IOLs attempt to improve this by allowing postoperative refraction changes to the lens. One lens has recently become commercially available in the United States and allows for the patient to be refracted about three to four weeks post operatively. The IOL can then be adjusted at the silt lamp using an ultraviolet Light (UV) delivery system. The manufacturer reports that the UV system is pre-programmed to deliver the light in a pattern, which causes polymerisation of diffusible light sensitive macromers in the central 6mm zone. This change in diffusion gradient causes the unpolymerised macromer to be diffused into the irradiated zone, causing a change in shape and refractive power of the IOL. Treatment time is reported to be between 50 and 90 seconds and a single treatment can adjust as much as }2.00D.

Cataract surgery has come a long way since its most primitive state of lens couching as researchers and developers aim to improve all aspects of this surgery, which is often referred to as one of the most successful surgeries on the human body. There are now more options for patients, referrers and surgeons to choose from than there have ever been, but perhaps one factor that we will never be able to perfect is patient selection and expectations – especially for refractive options. This is because sometimes, no matter how seemingly perfect the result appears, perfection is in the eye of the beholder.

Dr Kerrie Meades MBBS(Hons), FRANZCO is a refractive and cataract surgeon, an approved Kamra inlay surgeon and the founder of PersonalEyes. Dr Meades is passionate about refractive surgery including surface treatments, LASIK, phakic IOLs, customised cataract surgery, intracorneal rings, cross linking and presbyopia. She has special interests in cataract and refractive surgery, medical retina including fluorescein angiography and laser. Dr Meades has published many papers in cataract, refractive surgery and general ophthalmology and has presented at events in Australia and overseas. She is a member of RANZCO, ASCRS, AAO, RACS, a founding member of AUSCRS, on the advisory board of ALCON and Secretary of Women in Ophthalmology. 

References 

1. JM, P. Aging and age-related disease of the ocular lens and vitreous body. Invest Ophthalmol Vis Sci, 2013. 54(14): p. orsf54-orsf59. 
2. Medicare Item Report. 2020; Available from: medicarestatistics.humanservices.gov.au/statistics/do.jsp?_ PROGRAM=%2Fstatistics%2Fmbs_item_standard_repor t&DRILL=ag&group=42702%2C+42705&VAR=services &STAT=count&RPT_FMT=by+state&PTYPE=calyear&STA RT_DT=200901&END_DT=201912. 
3. RRA Bourne, S.F., T Braithwaite, MV Cicinelli, A Das, JB Jonas, et al. Magnitude, temporal trends, and projections of the global prevalence of blindness and distance and near vision impairment: a systematic review and meta-analysis. Lancet Glob Health, 2017. 5(9): p. e888-97. 
4. Davis, G. The evolution of cataract surgery. Missouri Medicine, 2016. 113(1): p. 58-62. 
5. Smit Bavariya, A.A., Priya Narang, Amar Agarwal, Ashvin Agarwal. Couching in Africa: tTechnique and management of comorbididties with cataract removal, Glued IOL, and Vitrectomy. Journal of Refractive Surgery 2019. 35(9): p. 611-612. 
6. JF Schemann, B.S., Coulibaly S. Traditional couching is not an effective alternative procedure for cataract surgery in Mali. Ophthalmic Epidemiology, 2000. 7(4): p. 271-283. 
7. Rucker, C.W. Cataract: A historical perspective. Invest Ophthalmol Vis Sci, 1965. 4(4): p. 377-388. 
8. Aravind Haripriya, H.S., RD Thulasiraj, Changing techniques in cataract surgery: how have patients benefited? Community Eye Health Journal, 2017. 30(100): p. 80-81. 
9. Sagar Rajakarnikar, D.B.S., Schit Dhakal, Ram Shrestha, Kamala Thapa, Anu Gurung. Comparative study of extra capsular cataract extraction (ECCE) and small incision cataract surgery (SICS): experience on cataract surgery in tertiary centre of army hospital, Kathmandu. Nepalese Journal of Ophthalmology, 2019. 10(2): p. 162-167. 
10. Kelman, C., Phaco-emulsification and aspiration: a new technique of cataract removal: a preliminary report. Am J Ophthalmol., 1967. 64(1): p. 23-35. 
11. Nagy, Z., Initial clinical evaluation of an intraocular femtosecond laser in cataract surgery. J Refract Surg, 2009. 25(12): p. 1053-1060. 
12. Harry W Roberts, V.K.W., Daniel L Sullivan, Polina Hidzheva, Delia I Detesen, Bissoon S Heemraz, John M Sparrow, David P S O’Brat. A randomized controlled trial comparing femtosecond laser–assisted cataract surgery versus conventional phacoemulsification surgery. Journal of Cataract & Refractive Surgery, 2019. 45(1): p. 11-20. 
13. Carmen Oakley, S.E., Penelope Allen, Brendan Vote. Visual outcomes with femtosecond laser-assisted cataract surgery versus conventional cataract surgery in toric IOL insertion. Clinical Experimental Ophthalmology, 2016. 44(7): p. 570-573. 
14. Michael Lawless, C.H. Femtosecond laser cataract surgery: An experience from Australia. Asia Pac J Ophthalmol, 2012. 1: p. 5-10. 
15. RM Varsits, N.H., B Doller, O Findl. Evaluation of an intraoperative toric intraocular lens alignment system using an image-guided system. Journal of Cataract & Refractive Surgery, 2019. 45(9): p. 1234-1238. 
16. Fenqi Zhou, W.J., Zhuoling Lin, Xiaoyan Li, Haotian Lin, Weirong Chen, Qiwei Wang. Comparative meta-analysis of toric intraocular lens alignment accuracy in cataract patients: image-guided system versus manual marking.Review. Journal of Cataract & Refractive Surgery, 2019. 45(9): p. 1340-1345. 
17. Robert Cionni, R.D., Michael Breen, Cody Hamilton. A large retrospective database analysis comparing outcomes of intraoperative aberrometry with conventional preoperative planning. Journal of Cataract & Refractive Surgery, 2018. 44(10): p. 1230-1235. 
18. MG Woodcock, R.L., RJ Cionni, M Breen, MC Scott. Intraoperative aberrometry versus standard preoperative biometry and a toric IOL calculator for bilateral toric IOL implantation with a femtosecond laser: One-month results. Journal of Cataract & Refractive Surgery, 2016. 42(6): p. 817-825. 
19. Ridley, N.H.L. Further experiences of intraocular acrylic lens surgery. British Journal of Ophthalmology, 1954. 38: p. 156-162. 
20. Zhou, K.Y. 1983. Chinese Medical Journal Silicon Intraocular lenses in 50 cataract cases. 96(175-176). 
21. Jafarinasab Mohammed-Reza, F.S., Baghi Ahmad- Reza, Ziaie Hossein, Mehdi Yaseri. Aspheric versus spherical posterior chamber intraocular lenses. Journal of Ophthalmic and Vision Research 2010. 5(4): p. 217-222. 
22. NY Makhotkina, M.N.M.,T Berendschot et al. Effect of active evaluation on the detection of negative dysphotopsia after sequential cataract surgery: discrepancy between incidences of unsolicited and solicited complaints. Acta Ophthalmol 2018. 96: p. 81-87. 
23. JL Alio, H.K., B Cochener, A Plaza-Puche. Quality of life related variables measured for three multifocal diffractive intraocular lenses: a prospective randomised clinical trial. Clinical Experimental Ophthalmology, 2018. 46(4): p. 380-388. 
24. Y Lee, G.L., HS Son, T Yildrim, R Khoramnia, G Auffarth. Assessment of the image quality of extended depthof- focus intraocular lens models in polychromatic light. Journal of Cataract & Refractive Surgery, 2020. 46(1): p. 108-115. 
25. D Breyer, I.K., R Lucchesi, C Herbers, M Moftha, S Abdassalam. Individualised presbyopia treatment with intraocular lenses based on refractive optical principles. European Society of Cataract and Refractive Surgeons 2019, 2019. 
26. HP Sandoval, S.L., Stephen Slade, Richard Potvin, Eric Donnenfeld, Kerry Solomon, Extended depth-of-focus toric intraocular lens targeted for binocular emmetropia or slight myopia in the nondominant eye: visual and refractive clinical outcomes. Journal of Cataract & Refractive Surgery, 2019. 45(10): p. 1398-1403. 
27. M Shajari, M.M., J Langer, T Kreutzer, A Wolf, T Kohnen, S Priglinger, W Mayer. Safety and efficacy of a small aperture capsular bag fixated intraocular lens in eyes with severe corneal irregularities: small aperture IOL in eyes with corneal irregularities. Journal of Cataract & Refractive Surgery, 2020. Published ahead of Print, POST ACCEPTANCE, 21 January 2020. 
28. FE Harman, S.M., G Kampougeris, Comparing the 1CU accommodative, multifocal, and monofocal intraocular lenses: a randomised trial. Ophthalmology, 2008. 115: p. 993-1001. 
29. P Perez-Merino, J.B., C Dorronsoro. Aberrometry in patients implanted with accommodative intraocular lenses. American Journal of Ophthalmology, 2014. 2014(157). 
30. JL Alio, A.P.-P., R Montalban. Near visual outcomes with single-optic and dual-optic accommodating intraocular lenses. Journal of Cataract & Refractive Surgery, 2012. 38: p. 1568-1575. 
31. JS Pepose, J.B., M Qazi. Benefits and barriers of accommodating intraocular lenses. Current Opinion in Ophthalmology, 2017. 28(1): p. 3-8. 32. JS Pepose, J.B., M Qazi,. Accommodating intraocular lenses. Asia Pac J Ophthalmol, 2017. 6(4): p. 350-357. 
32. M Lundstrom, M.D., Y Henry et al. Risk factors for refractive error after cataract surgery: Analysis of 282 811 cataract extractions reported to the European Registry of Quality Outcomes for cataract and refractive surgery. Journal of Cataract & Refractive Surgery, 2018. 44: p. 447-452.