3.2.4.2. Implantation of intraocular lenses for correction of presbyopia in cataract surgery after keratorefractive surgery
3.2.4.2. Implantation of intraocular lenses for correction of presbyopia in cataract surgery after keratorefractive surgery
1 - Hospital da Luz , Lisboa, Portugal
2 - Facultad de Medicina de Lisboa, Portugal
Cataract surgery with multifocal intraocular lens implantation (MIOL) in patients with keratorefractive surgery for correction of prior ametropia is a reality that simultaneously represents a challenge for the surgeon1,2. Millions of patients worldwide have undergone ametropia correction with LASER Excimer, a technology that has existed for more than 25 years so there is an emerging population of patients with prior keratorefractive surgery who presently have presbyopia and even cataract. They are generally well-informed and highly motivated patients, who wish to preserve the independence from glasses by requiring refractive solutions for their cataract surgery. The main challenges faced by this particular group of patients in cataract refractive surgery are, on one hand, the difficulty in calculating the power of the intraocular lens (IOL) and, on the other, the reduction of the contrast sensitivity and the quality of vision resulting from the multifocality of the cornea submitted to keratorefractive treatment.
In this particular group of patients, the selection of suitable biometric formulas for the calculation of IOL potency is the main tool to avoid refractive surprises1. Corneal asphericity following myopic LASIK is directly related to the refractive surprise observed in cases where the SRK/T formula is used to calculate the power of IOL3. However, there are currently biometric formulas that allow the calculation of IOL potency with great accuracy. Multifocal lenses (MIOLs) cause per se known changes in the quality of vision and this divides ophthalmologists' opinions on the choice of IOL to be implanted. However, there is increasing evidence that multifocal IOLs are a valid option in these patients4. Some studies have shown that the implantation of refractive-diffractive hybrid IOLs in eyes with previous myopic or hyperopic LASIK provides good refractive results5-10. More recently, the extended depth of focus IOLs (EDOF) have demonstrated good refractive results and simultaneously present a lower incidence of dysphotopic phenomena than refractive and diffractive multifocal lenses and a greater tolerance to residual refractive errors and may be a valid tool for this group of patients11-13.
Preoperative assessment for all cataract patients or lens refractive surgery with lens implantation for presbyopia correction (PC IOL) should be carefully and exhaustively evaluated. Patients with active ocular or systemic disease, corneal disease including cornea guttate, chronic or recurrent uveitis, glaucoma, diabetic retinopathy, age-related macular degeneration, and retinal disease of any type should be excluded.
The preoperative study of the patient applying for PC IOL implantation should therefore include the following elements:
In patients with prior keratorefractive surgery, topography and biometry should receive special attention.
In patients with previous LASIK, the topography (Placido, Scheimpflug or a combination of both) is extremely important as it can be the only evidence of previously performed keratorefractive surgery when there is no clinical history with specific information of the procedure performed 15 or more years ago.
Placido topography allows in the first place the evaluation of the ocular surface. It is important to obtain consistent results in the different topographic exams performed. Otherwise it will be necessary to first treat ocular surface problems, before obtaining reliable serial topographic examinations, on the basis of which it is possible to decide whether or not to implant a PC IOL.
Through topography it is possible to evaluate the type of LASER treatment performed – myopic LASER (central flattening), or hyperopic LASER (peripheral flattening) –, the size and center of the optical zone and the transition zone. The most recent treatments have larger optical zones and smoother transition zones, being more permissive with the implantation of PC IOLs by inducing a lower amount of high order aberrations (HOA). It is thus fundamental the topographic and aberrometric study of regular and irregular corneal astigmatism, coma, spherical aberration and HOA.
Treatments should be excluded for ametropias >-6.00 D and >+1.50 D, keratometric readings <37 D and optical zones smaller than 6mm since these eyes present higher HOA as well as >0.5 mm decentrations as they induce vertical coma and consequent reduction of contrast sensitivity14. For any patient who is a candidate for cataract surgery, with or without prior LASIK, considering the possibility of placing a PC IOP, the following preoperative topographic and aberrometric inclusion criteria should be respected15,16:
The spherical aberration of the normal human cornea (z400) in the central 6 mm zone has an average value of +0.27 µm. After the myopic LASIK treatment, the spherical corneal aberration is more positive and after the hyperopic LASIK treatment the spherical corneal aberration is negative. The different manufacturers make available to the surgeon PC IOLs with different asphericities in order to compensate for the spherical aberration of the cornea of the operating eye and thus improve contrast sensitivity17. There are no positive spherical aberration PC IOLs yet, so it is recommended to implant neutral spherical aberration IOLs in patients with previous hyperopic treatments.
The exact calculation of IOL potency after keratorefractive surgery as well as the accuracy of postoperative residual refraction is still a challenge. This difficulty is related to two factors: the error in determining the total dioptric power of the cornea secondary to the change in the relation of the anterior curvature to the posterior curvature of the cornea after myopic LASIK, as well as the error of the estimate of the effective position of the IOL with the formulas that use keratometric values after LASIK. Thus, the change in corneal asphericity after myopic LASIK correlates with the refractive surprise found with the SRK/T formula3. But the solution to the calculation problem is rapidly evolving nowadays with readily available online platforms as well as post-LASIK specific formulas inserted into the software of the current optical biometers through which the calculation of IOL power is quite accurate and reproducible. The most recent formulas no longer require keratometric information prior to LASIK surgery, which greatly facilitates the surgeon's task since in many occasions there is no information from the previously performed surgery. Thus, the ASCRS calculator post refractive surgery of the cornea with the formulas of Shammas, Barret True K and Haigis L are some examples that offer excellent results18.
The OCT Swept source biometrics and the calculation of IOL power by ray tracing are developing technologies with great potential to further improve the accuracy of results. Intraoperative aberrometry is of great interest since it allows to perform the smallest IOL power corrections based on the aphakic refraction19-21.
Likewise, an accurate, flawless surgical technique, including performing a centered 5 mm continuous circular capsulorrhexis with placement of the intraocular lens perfectly centered on capsulorrhexis, is also important in the final refractive result. According to the most recent ASCRS epidemiological study, 94.2% of patients undergoing cataract had refractive results of <1 D and 67.3% presented results of <0.5 D.
Currently available PC IOL options are numerous and varied in material, design and optical principles, allowing meeting each patient's visual needs in a personalized manner respecting surgeons' preferences22. From accommodative lenses, older models of bifocal MIOLs with two near and far vision foci with different near additions, to the newer models of trifocal MIOLs in which a third intermediate vision focus is added, so important for the professional activity of many patients, up to the latest EDOF IOL models, some of them feature diffraction rings on their optics, while others already have optic zones with soft transition foci for distant and intermediate vision, and even stenopic optic zones.
Several types of PC IOLs have been implanted in patients with previous myopic and hyperopic LASIK with satisfactory results5-10,21-23. The Hospital da Luz group has conducted several studies in cataract patients and previous myopic LASIK with EDOF IOL implantation because these IOLs are considered to cause less reduction of contrast sensitivity and are more tolerant to residual refractive errors than MIOLs11-13 and so they may offer better results in this group of patients in whom contrast sensitivity is reduced at baseline.
Next, the summaries of two works performed by the group will be presented. In the first one, the objective was to compare the results obtained in patients with cataract and previous myopic LASIK with monofocal IOL versus the Symfony EDOF IOL implantation, both from Johnson & Johnson Vision. In the second study the objective was to evaluate the results obtained with the Johnson & Johnson Vision Symfony EDOF IOL implant in cataract patients versus cataract patients and previous myopic LASIK.
Comparative study of the clinical results obtained in cataract surgery after previous myopic LASIK with monofocal IOL versus EDOF IOL.
Purpose:
To compare the clinical results obtained after cataract surgery in previously operated patients with myopic LASIK with monofocal versus EDOF IOL, a prospective comparative study was carried out at Hospital da Luz, Lisbon, Portugal.
Methods:
Eighty-eight eyes were studied from 44 previously operated myopic LASIK patients who underwent sequential bilateral cataract surgery with Tecni ZCB00 monofocal IOL (22 patients; monofocal group) or Tecnis Symfony EDOF IOL (22 patients; EDOF group), both Johnson & Johnson Vision lenses. Visual acuity, refraction, blurring curve, contrast sensitivity, photic phenomena, glasses independence and patient satisfaction four months after surgery were evaluated.
Results:
No statistically significant differences were observed in most of the studied parameters, all with p=0.027. The uncorrected intermediate binocular visual acuity (BUIVA) and binocular uncorrected near visual acuity (BUNVA) were significantly better (p<0.01) in the EDOF group. The blurring curve showed greater differences with increase of the negative blur (p<0.01). There were no statistically significant differences in contrast sensitivity in the studied frequencies (p>0.05). The majority of patients in both groups did not spontaneously report dysphotopsies. A slight glare was present in 22.7% of the patients in the EDOF group and in 9.1% of the patients in the monofocal group as well as the presence of halos in 13.6% of both groups. The independence of glasses at the intermediate and near distances was superior in the EDOF group.
Conclusions:
The Symfony EDOF IOL is a valid option for cataract surgery in patients with prior myopic LASIK because it offers levels of quality of vision comparable to those of monofocal lenses and is more effective in intermediate and near vision than monofocal lenses.
Comparative study of the clinical results obtained with Symfony EDOF IOL in patients previously operated with myopic LASIK versus a control group.
Purpose:
To compare the clinical results obtained after cataract surgery with Johnson & Johnson Vision Symfony EDOF IOL implant in cataract patients versus preoperatively operated myopic LASIK cataract patients, a prospective comparative study was conducted at Hospital da Luz, Lisbon, Portugal.
Methods:
We studied 30 eyes from 15 cataract patients previously operated myopic LASIK who underwent sequential bilateral cataract surgery with the Symfony EDOF IOL implant (LASIK group) and compared them with the results obtained in 30 eyes of 15 cataract patients without previous keratorefractive surgery also operated by the same surgeon with Symfony EDOF IOL implant (control group). Visual acuity, refraction, blurring curve, contrast sensitivity, photic phenomena, independence of glasses and patient satisfaction three months after surgery were evaluated.
Results:
No statistically significant differences were observed in most of the studied parameters, such as distant, intermediate and near, corrected and uncorrected, binocular visual acuity (all with p=0.027). The defocus curve showed a blur tolerance of up to -2.00 D with a VA ≥0.05 logMAR in both groups. The light distortion index was 35% in the LASIK group and 30% in the control group. There were no statistically significant differences in photopic and scotopic contrast sensitivity with glare in the studied frequencies (p>0.05). Most patients in both groups did not spontaneously report the presence of dysphotopsies. All patients were satisfied with the surgical treatment performed with a statistically significant difference in favor of the LASIK group in the QoV Score questionnaire (p<0.01). The independence of glasses at distant and intermediate distances as well as the need for occasional close correction occurred similarly in both groups.
Conclusions:
The Symfony EDOF IOL is a valid option for cataract surgery in patients with prior myopic LASIK because it offers levels of quality of vision comparable to those offered to cataract patients without previous corneal refractive surgery.