After the age of 40, most people develop presbyopia. A person aged around 37 or 38 years who is mildly (+0.50–0.75 D) hyperopic for distance simply accommodates and does not need to wear glasses.
However, by the time that person turns 40, near work is hindered by bouts of blurring, accommodative asthenopia and headaches. A person who has never worn spectacles before is now faced with needing them for both distance and near vision. This problem gets worse with time as the presbyopia increases and residual accommodation decreases.
A 60-year-old woman, a former Bollywood movie star, presented with recurrent headaches. On examination, she had spectacle prescription of OD +1.00 D for distance, +3.5 D for near, and OS +1.25 D for distance and +3.75 D for near.
After a thorough diagnostics workup, including optical coherence tomography (OCT) (AngioVue Imaging System; Optovue), biometry (IOL Master 700; Carl Zeiss) and slit-lamp examination (BQ 900; Haag-Streit), I identified the problem. The patient did not want to wear spectacles and had actually never worn them, even though she owned a pair.
She claimed not to be an avid reader; however, I noticed that she used her smartphone frequently in the office, and she reported that she used her tablet quite often. After some observation and subsequent conversation, she admitted that she read on her smartphone all day and was a frequent user of social media and networking sites.
I explained that her persistent headache was due to slight hyperopia coupled with presbyopia, and that without correction and an adjustment of her current habits her headaches would not go away.
For this patient, I had to face the fact that she would never wear spectacles and had a high need for excellent near and intermediate vision. After patient counselling it became clear that she would accept a loss of contrast for distance. Additionally, because she did not drive, I had no concerns with night-time halos. Considering these facts, I decided that the best solution for her was a clear lens exchange with implantation of a trifocal IOL.
I counselled the patient about the clear lens exchange technique and procedure, including risks as well as benefits. This included a preoperative data assessment with a full-length OCT image (IOLMaster 700; Carl Zeiss) and a customised surgical plan.
I used the SRK/T formula to calculate the appropriate IOL power and decided to order trifocal IOLs (AT LISA tri 839MP; Carl Zeiss; right eye 22.5 D, left eye 23.0 D).
Because my clinic and operating facility are located at different venues, I perform computer- assisted (Callisto; Carl Zeiss) cataract surgery that allows for data transfer between various places. Before I started to use a computer-guided system, I used to pre-mark the eye of the patient in a sitting position using a digital marker (AXsys; Asisco).
This was fairly accurate, but I considered the following drawbacks when adopting the change:
> I could never be sure that the patient’s head was completely vertical;
> Studies show that if the axis shifts 10 degrees, one-third of the toric IOL’s effect will be lost. If the axis shifts 20 degrees, two-thirds of the toric IOL’s effect is lost;
> Using ink on the eye disturbs the epithelium, and the cornea is less clear the next day;
> If the patient is apprehensive and suddenly moves, the cornea gets an epithe- lial scratch that might take a day or two to heal. During this time, the patient will experience dysphotopsia and a teary, uncomfortable eye. Although this is rare, I have witnessed it occur.
During surgery, I used a precision laser system (Catalys; Precision Lens) to create a precise central capsulorhexis, followed by hacoemulsification with a phacoemulsification and vitrectomy system (Visalis 500; Carl Zeiss). Conveniently, the trifocal IOL selected was a preloaded lens that was injectable through the main 2.2 mm tunnel.
Whenever I have a patient with more than 0.5 D cylinders preoperatively, I choose to implant a toric IOL. This is because, in
a multifocal IOL, any cylinder more than 0.5 D blurs vision and decreases patient satisfaction.
My preferred toric IOL implantation technique is to put the leading haptics in the bag at the time of injection of the preloaded IOL, and then to rotate it to the desired meridian with the trailing haptics out of the bag. With this technique, there is limited if not zero stress on the capsular bag zonular mechanism.
When the toric IOL reaches the desired meridian, I simply deepen the chamber using the bimanual irrigation/aspiration hand piece (Geuder) and gently tap the lens into place. This ensures that the IOL remains on its desired meridian even after I have removed all viscoelastic.
The patient achieved –0.25 D in both eyes. Postoperatively, she was able to do her daily reading on her smartphone and tablet without the need to wear spectacles or to suffer any limitations.
I have been performing bilateral cataract surgery with multifocal IOLs for more than 15 years now, and I have implanted more than 35,000 IOLs. It is important to remember that in cases with multifocal IOLs, the patient’s vision is the best when there is zero residual cylinder and the residual sphere is under 0.25 D. Any more than this, particularly if there is any residual cylinder, will decrease the patient’s satisfaction.