Purpose
To evaluate distance and near image quality after hybrid bi-aspheric multifocal central presbyLASIK treatments.
Design
Consecutive case series.
Methods
Sixty-four eyes of 32 patients consecutively treated with central presbyLASIK were assessed. The mean age of the patients was 51 ± 3 years with a mean spherical equivalent refraction of −1.08 ± 2.62 diopters (D) and mean astigmatism of 0.52 ± 0.42 D. Monocular corrected distance visual acuity (CDVA), corrected near visual acuity (CNVA), and distance corrected near visual acuity (DCNVA) of nondominant eyes; binocular uncorrected distance visual acuity (UDVA); uncorrected intermediate visual acuity (UIVA); distance corrected intermediate visual acuity (DCIVA); and uncorrected near visual acuity (UNVA) were assessed pre- and postoperatively. Subjective quality of vision and near vision was assessed using the 10-item Rasch-scaled Quality of Vision and Near Activity Visual Questionnaire, respectively.
Results
At 1 year postoperatively, 93% of patients achieved 20/20 or better binocular UDVA; 90% and 97% of patients had J2 or better UNVA and UIVA, respectively; 7% lost 2 Snellen lines of CDVA; Strehl ratio reduced by ∼−4% ± 14%. Defocus curves revealed a loss of half a Snellen line at best focus, with no change for intermediate vergence (−1.25 D) and a mean gain of 2 lines for near vergence (−3 D).
Conclusions
Presbyopic treatment using a hybrid bi-aspheric micro-monovision ablation profile is safe and efficacious. The postoperative outcomes indicate improvements in binocular vision at far, intermediate, and near distances with improved contrast sensitivity. A 19% retreatment rate should be considered to increase satisfaction levels, besides a 3% reversal rate.
Presbyopia is an age-related condition characterized by the gradual loss of the eye’s ability to focus actively on nearby objects. This condition is mainly attributed to a loss of elasticity of the crystalline lens, accompanied by a change in the ciliary muscle strength and lens curvature. Refractive surgeons have faced challenges in effectively combining the treatment of refractive errors and presbyopia. Surgical presbyopia corrections have seen several developments, from the monovision and multifocal ablation techniques to the modern hybrid methods combining the benefits of several techniques. Corneal inlays and intraocular lenses have also been a popular alternative treatment for presbyopia. Monovision techniques usually involve correcting the dominant eye for distance, as opposed to crossed monovision, where the dominant eye is corrected for near vision.
Charman proposed that the main aim of presbyopia treatments was to extend the binocular depth of focus to yield adequate distance and near vision with good retinal contrast at lower spatial frequencies. Dai first proposed the use of rigorous methodologies to theoretically optimize vision over the entire target range from near to distance. Multifocal ablations are designed to achieve these characteristics. These result in a pseudo-accommodative cornea realized either in the form of a peripheral near zone (concentric ring for near vision) or in the form of a central near zone (central disc for near vision).
PresbyLASIK is one such robust technique based on traditional laser-assisted in situ keratomileusis (LASIK) to correct the visual defect for distance while simultaneously reducing the near spectacle dependency in presbyopic patients. PresbyLASIK has been stated as a promising technology, but lacking the level of maturity of monovision. For achieving maximum patient satisfaction, good near vision should be accompanied with no detrimental effect in the distance vision. A hybrid method combining micro-monovision and multifocal ablation could potentially achieve full range of vision.
In this work, a hybrid bi-aspheric micro-monovision technique is presented and the outcomes are retrospectively analyzed in 64 consecutive eyes (of 32 patients) treated using this method.
Methods
Patients
This cohort study was based on a consecutive case series of patients treated by a single surgeon (M.H.A.L.) with the hybrid bi-aspheric micro-monovision technique to correct presbyopia, at VisionClinics, Utrecht, Netherlands. Proper informed consent was obtained from each patient, for both the treatment and use of their de-identified clinical data for publication. The Independent Review Board Nijmegen (IRBN) evaluated the study and stated that the investigation in this form is not subject to the Medical Research Involving Human Subjects Act (WMO). The outcomes of performing presbyLASIK in 64 consecutive eyes (32 patients) were retrospectively analyzed. The average age of the 32 patients (17 male and 15 female; 17 hyperopic and 15 myopic) was 51 ± 3 years (range 45–55 years). The mean preoperative spherical equivalent was −1.08 ± 2.62 D (−6.75 to 2.00 D), with mean preoperative astigmatism 0.54 ± 0.50 D (0.00–2.10 D) and mean spectacle near addition 1.75 ± 0.36 D (1.00–2.50 D).
To categorize the candidate as presbyopic, the monocular corrected near visual acuity (CNVA) at 40 cm had to be at least 2 logRAD lines better than the distance corrected near visual acuity (DCNVA) at 40 cm in each eye. Inclusion criteria were patients older than 45 years, medically suitable for LASIK, presbyopic, with corrected distance visual acuity (CDVA) no worse than 20/32 in either eye (with at least 20/25 in the best eye), stable refraction (<0.5 D change in mean spherical equivalent) for 1 year prior to the study, discontinued usage of contact lenses for at least 2–4 weeks (depending on contact lens type) prior to the preoperative evaluation, and photopic pupil diameter smaller than 3.0 mm. The pupil diameters were obtained from the topographic measurements. Patients were required to have normal keratometry and topography (visually no suspect or form fruste keratoconus). Patients who suffered from systemic illness, had a calculated corneal bed thickness less than 300 μm after ablation, had preoperative central corneal thickness of less than 470 μm, had previous ocular surgery, or had abnormal corneal topography were excluded from the study. Additional exclusion criteria were clinically relevant lens opacity, a pupil offset of 0.7 mm or more, and any signs of binocular vision anomalies at distance and near.
Preoperative Assessment
A full ophthalmologic examination was performed on all the patients prior to surgery including manifest refraction, cycloplegic refraction, slit-lamp microscopy of the anterior segment, handheld ultrasound pachymetry (Corneo-Gage Plus; Sonogage, Cleveland, Ohio, USA), dilated funduscopy, and Goldmann intraocular pressure measurement. CDVA and uncorrected distance visual acuity (UDVA) were assessed with Early Treatment Diabetic Retinopathy Study (ETDRS) charts. Near and intermediate acuity was assessed unaided and distance corrected (uncorrected near visual acuity [UNVA], DCNVA, uncorrected intermediate visual acuity [UIVA], and distance corrected intermediate visual acuity [DCIVA]), with the Dutch version of the Radner Reading Charts at 40 cm. All the tests were performed binocularly. The selection of the distance and near eye was based on a protocol described by Durrie.
The corrected visual acuity was always assessed with trial frames and not contact lenses. Binocular defocus curves were measured (with both eyes corrected for distance, ie, eliminating the effect of the micro-monovision component) with induced lens blur from +1.5 D to −4.0 D in 0.5 D randomized spherical steps, using distance ETDRS charts with the letters randomized between presentations and magnification effects being accounted for.
Contrast sensitivity with and without glare was measured using the Contrast Glare Tester CGT-1000 (Takagi Seiko Co Ltd, Nagano-Ken, Japan) at 6 target sizes (6.3 degrees, 4.0 degrees, 2.5 degrees, 1.6 degrees, 1.0 degrees, and 0.7 degrees) after correcting the refractive error with spectacles. Log values of the contrast sensitivity scores were used for statistical analysis.
Corneal and ocular aberrometry was performed with the OPD Scan II (Nidek, Gamagori, Japan) over a 6 mm diameter. Root mean square (RMS) higher-order aberrations, Strehl ratio, and corneal asphericity were extracted.
Subjective patient-reported outcomes were assessed using 2 questionnaires: the Quality of Vision Questionnaire and the Near Activity Visual Questionnaire. The Quality of Vision Questionnaire was developed by McAlinden and associates to assess symptoms such as glare, halos, and starbursts with the use of simulation photographs. Symptoms are scored based on their frequency, severity, and bothersomeness. The questionnaire is valid for use with spectacle wearers, contact lens wearers, and those having had laser refractive surgery, intraocular refractive surgery, or eye disease including cataract. The Near Activity Visual Questionnaire was used to assess patient satisfaction with near functional vision. For both questionnaires the raw response scores were converted to a 0–100 Rasch scale, with higher scores indicating worse quality of vision.
The Quality of Vision and Near Activity Visual Questionnaires were administered preoperatively and at 3 months, 6 months, and 1 year postoperatively. Patients were instructed to answer the questionnaires at each follow-up visit to recount their subjective impression in unaided bright and dim lighting conditions.
Surgical Procedure
All the treatments were prepared using the SCHWIND PresbyMAX treatment planning module in aspheric mode (SCHWIND eye-tech-solutions GmbH and Co KG, Kleinostheim, Germany). The devices used in this study bear the standards of European conformity (Conformité Européene or CE marking) but are not approved by the US Food and Drug Administration (FDA). The hybrid surgical technique involved treating the dominant eye (also referred to as the distant eye) more toward distance vision (target refraction −0.1 D) and the nondominant eye (also referred to as the near eye) slightly toward near vision (target refraction −0.9 D) for achieving micro-monovision. Multifocality increases the range of intermediate vision with a different depth of focus between the distant eye (+1.1 D) and the near eye (+2.2 D).
For each treatment, the planning software calculated the size of the optimal transition zone, depending on the preoperative refraction and optical treatment zone. Drops of topical anaesthetic were instilled in the upper and lower fornices. Flaps were made using Intralase iFS 150 KHz femtosecond laser (AMO, Chicago, Illinois, USA) with a 100 μm nominal flap thickness.
Additional drops of topical anesthetics were instilled; the lid margins and periocular region were disinfected using diluted povidone. A sterile drape covering eye lashes and face was used to isolate the surgical field. A lid speculum was inserted to allow maximum exposure of the globe.
Proper alignment of the eye with the laser was achieved with a 1050 Hz infrared eye tracker with simultaneous limbus, pupil, and torsion tracking integrated into the laser system and centered on the corneal vertex. The eye tracker had a typical response time of 1.7 ms with a system total latency time of 2.9 ms. The flap was lifted and the excimer laser ablation was delivered to the stroma. Aspheric non-wavefront-guided treatments were performed. The ablation profile was centered on the corneal vertex determined by the topographer (taking 70% of the pupil offset value), which closely approximates the visual axis. Further, the topographic keratometry readings at 3 mm diameter were used for the compensation of the loss of efficiency when ablating the cornea at non-normal incidences. Patients were requested to look at a pulsing green fixation light throughout the ablation.
The flap was repositioned and the interface was irrigated with balanced salt solution for removing any debris. Patients received topical antibiotic drops 4 times a day for 1 week; corticosteroid drops 4 times a day tapering off in 1 week, and ocular lubricants as needed.
Postoperative Evaluation
Patients were reviewed at 6 weeks, 3 months, 6 months, and 1 year postoperatively. All postoperative follow-up visits included measurement of monocular and binocular UDVA, UNVA, UIVA, manifest refraction, CDVA, DCNVA, DCIVA, and defocus curves. The response to Quality of Vision and Near Activity Visual Questionnaires, topography and aberrometery, and contrast sensitivity were recorded at every follow-up visit except 6 weeks postoperatively.
Statistical Analysis
Data were assessed for normality using the Shapiro-Wilk test. Analysis of variance and t tests were performed on normally distributed data and Friedman tests and post hoc Wilcoxon signed rank tests when the data were not normally distributed.
Distance visual acuity was evaluated in logMAR but converted to equivalent Snellen fractions for reporting comparability. Similarly, near visual acuity was evaluated in logRAD but converted to Jaeger scale for reporting comparability. Manifest refraction was used for preoperative to postoperative comparison. Uncorrected and corrected visual acuity, contrast sensitivity, spherical equivalent refraction, and refractive astigmatism were individually analyzed for myopic and hyperopic patients.
Results
The mean optical treatment zone diameter was 6.58 ± 0.26 mm (6.0–7.0 mm, median 6.5 mm). The total ablation zone ranged from 6.8 mm to 8.9 mm.
Efficacy
The distribution of binocular UDVA, UIVA, and UNVA are presented in Figure 1 . At 1 year follow-up, 93% (13 out of 14) of myopic patients and 94% (15 out of 16) of hyperopic patients achieved 20/20 or better binocular UDVA; 100% (14 out of 14) of myopic patients and 94% (15 out of 16) of hyperopic patients achieved Jaeger level J2 or better UIVA; while 93% (13 out of 14) of myopic patients and 88% (14 out of 16) of hyperopic patients achieved Jaeger level J2 or better UNVA.
Changes in contrast sensitivity scores were assessed with and without the disability glare ( Figure 2 ). At 3 and 6 months follow-up, the contrast sensitivity scores remained similar to the respective preoperative scores in both tests (with and without the disability glare), but improved, respectively, at the 1 year follow up ( P < .005 at all sizes).
Safety
The change in binocular DCIVA and DCNVA is presented in Figure 3 . At 1 year follow-up, 85% (11 out of 13) of myopic patients and 94% (15 out of 16) of hyperopic patients achieved a Jaeger level J2 or better binocular DCIVA, while 57% (8 out of 14) of myopic patients and 63% (10 out of 16) of hyperopic patients achieved a Jaeger level J4 or better binocular DCNVA. A loss of 2 Snellen lines of binocular CDVA ( Figure 4 ) was observed in 7% (1 out of 14) of myopic patients and 6% (1 out of 16) of hyperopic patients at 1 year follow-up.
Accuracy
For myopic and hyperopic patients, a good separation was observed between the dominant and nondominant eye for refractive deviation from target spherical equivalent refraction and astigmatism ( Figure 5 ). In myopic patients, 100% (15 out of 15) of distance eyes were within 0.5 D of emmetropia while 67% (10 out of 15) of near eyes were within 0.6 D of micro-monovision target (−0.9 D); in hyperopic patients, 76% (13 out of 17) of distance eyes were within 0.5 D of emmetropia while 59% (10 out of 17) of near eyes were within 0.6 D of micro-monovision target (−0.9 D). For myopic patients, 100% (15 out of 15) of distance eyes and 73% (11 out of 15) of near eyes were within 0.5 D of astigmatism; in hyperopic patients, 100% (17 out of 17) of distance eyes and 59% (10 out of 17) of near eyes were within 0.5 D of astigmatism. Refractive stability was achieved for both dominant (DE) and non-dominant eye (NE) in myopic and hyperopic patients, from 6 weeks postoperatively ( Figure 6 ). A nearly linear (coefficient of determination r 2 = 0.97, P < .00001) relationship between the laser attempted and achieved spherical equivalent refraction was observed ( Figure 7 ).
Subjective Rating
Quality of Vision scores assessing symptoms based on their frequency, severity, and bothersomeness are presented in Figure 8 . Compared to the corrected preoperative scores, the Quality of Vision score worsened postoperatively ( P = .02), mainly with an increase in patients seeing haloes ( P = .002), blurred vision ( P = .02), and double vision ( P = .01).
Near Activity Visual Questionnaire (NAVQ) scores assessing patient satisfaction with near functional vision and overall satisfaction are presented in Figure 9 . The Near Activity Visual Questionnaire scores improved from little satisfaction to very high satisfaction level ( P < .00001), with an improvement in Rasch scores ( P < .0001). Stability was observed in Near Activity Visual Questionnaire scores from 3 months follow-up time.
Aberrations
Change in corneal asphericity (Q value) at 3 mm diameter, Strehl ratio, RMS of higher-order aberrations (at 6 mm diameter), and corneal and ocular spherical aberrations are presented in Figure 10 . Asphericity was more prolate after surgery, indicating a central myopia (within 3 mm diameter, P < .00001). Compared to the preoperative status, 1 year postoperatively the Strehl ratio reduced by ∼−4% ± 14% ( P = .00007) and the corneal and ocular spherical aberrations (at 6 mm diameter) decreased by −0.38 ± 0.33 μm and −0.28 ± 0.35 μm, respectively ( P < .00001), with an increase in RMS higher-order aberrations (at 6 mm diameter) by 0.15 ± 0.24 μm ( P = .00002). All these metrics indicated good stability from 3 months onward.
