Vrinda Avenashi, Bachelor of Optometry
Fellow Optometrist, Dr. Shroff’s Charity Eye Hospital, Delhi, India
A common and rapidly evolving procedure is the cataract surgery, which engages removal of crystalline lens and replacing it with an intraocular lens, which may be monofocal or multifocal. With the increase in attribute toward lifestyle, nowadays patients have immense expectations about quality of vision after cataract surgery in monofocal. Also, every patient desire about spectacles independency after cataract surgery. Initially, monofocal intraocular lens were the good choice of patients but the advancing level of technology has created the multifocal intraocular lens to enhance outcomes of cataract surgery, improving near vision by dividing light at different focusing zone by which physiology of vision changes because of the dispersion of light happen when enter eyes. (1)
Figure 1: Multifocal Intraocular Lens Basic Principle.
The multifocal intraocular lens uses three separate but complementary optical principles (fig 1) namely refraction, diffraction and apodization, to achieve desiring near intermediate and far visual acuity (fig 2).
Figure 2: Diffractive Multifocal Intraocular Lens Zones.
It is not necessarily possible that every intraocular lens is suitable for every kind of person because the reason may include due to the complexity of the lifestyle choices and personality dynamics or the inherent anatomy and physiology of the eye. The need of multifocal intraocular lens demands the points to be kept in concern like who are suitable, what they are in occupation. Two major key indications to recommend multifocal intraocular lens include the patients work and leisure related activities and amount of time spend on each with priority level of both. Selecting the type of multifocal intraocular lens based on the two above key factor is also the salient feature of multifocal intraocular lens implantation. Also, multifocal intraocular lens best works in the patients with less than three quarters of diopters of cylinders. Another climax of implanting a multifocal intraocular lens is that patient must be having good macular function to achieve normal reading speed with currently available intraocular lens. So, one must undergo certain procedures in a well manner like the proper clinical evaluation, which includes measurement of uncorrected and corrected visual acuity, corneal topography, measurement of intraocular pressure and a dilated fundus examination with ocular coherence tomography. Some cases have revealed that besides the edge of multifocal intraocular lens, it has snag as well.(2)
Patients with irregular astigmatism may not have affirmative consequences of multifocal intraocular lens implantation. Also, refractive patients are more prone to notice the side effects of multifocal intraocular lens correction. The impediment in the performance of multifocal intraocular lens after successful implantation includes uncorrected refractive error, glare, halos, negative Dysphotopsia, decrease contrast sensitivity, blurred vision due to ametropia, dry eye syndrome, posterior capsular opacification and photic phenomena due to intraocular lens decentration. In an unpublished observational study done in a tertiary eye hospital in the northern India it was seen that on the patients with successful multifocal intraocular lens implantation in which they were asked few sets of questions which includes comfortability factor while doing near daily task, comfortability factor while performing daily distance task, how easily individual is able to finish any task in dim illumination like driving or else, how is the performance while doing intermediate distance task, is the lens is fulfilling the occupational need with the overall rating for the performance of multifocal intraocular lens. The result of the study shows 82% of the people achieved excellent distance vision with no residual addition power and 64% were found with no addition power with no residual addition.
- Braga-Mele R, Chang D, Dewey S, Foster G, Henderson BA, Hill W, Hoffman R, Little B, Mamalis N, Oetting T, Serafano D. Multifocal intraocular lenses: relative indications and contraindications for implantation. Journal of Cataract & Refractive Surgery. 2014 Feb 1;40(2):313-22.
- Negishi K, Hayashi K, Kamiya K, Sato M, Bissen-Miyajima H. Nationwide Prospective Cohort Study on Cataract Surgery with Multifocal Intraocular Lens Implantation in Japan. American Journal of Ophthalmology. 2019 Dec 1; 208:133-44.