Dolores Ortiz

Corneal biomechanical properties in normal, post-laser in situ keratomileusis, and keratoconic eyes

PURPOSE: To compare the biomechanical properties of normal, post‐laser in situ keratomileusis (LASIK), and keratoconic corneas evaluated by corneal hysteresis and the corneal resistance factor measured with the Reichert Ocular Response Analyzer (ORA). SETTINGS: Instituto Oftalmológico de Alicante, Vissum, Alicante, Spain. METHODS: Two hundred fifty eyes were divided into 3 groups: normal (control group), post‐LASIK, and keratoconus. The corneal biomechanical properties were measured with the ORA, which uses a dynamic bidirectional applanation process. The main outcome measures were intraocular pressure, corneal hysteresis, and the corneal resistance factor. RESULTS: The control group had 165 eyes; the LASIK group, 65 eyes; and the keratoconus group, 21 eyes. In the control group, the mean corneal hysteresis value was 10.8 mm Hg ± 1.5 (SD) and the mean corneal resistance factor, 11.0 ± 1.6 mm Hg. The corneal hysteresis value was lower in older eyes, and the difference between the youngest age group (9 to 14 years) and oldest age group (60 to 80 years) was statistically significant (P = .01, t test). One month after LASIK, corneal hysteresis and the corneal resistance factor decreased significantly, from 10.44 to 9.3 mm Hg and from 10.07 to 8.13 mm Hg, respectively. In the keratoconus group, the mean corneal hysteresis was 7.5 ± 1.2 mm Hg and the mean corneal resistance factor, 6.2 ± 1.9 mm Hg. There were statistically significant differences in both biomechanical parameters between keratoconic eyes and post‐LASIK eyes (P<.001, t test). CONCLUSIONS: The corneal hysteresis and corneal resistance factor values were significantly lower in keratoconic eyes than in post‐LASIK eyes. Future work is needed to determine whether these differences are useful in detecting keratoconus when other diagnostic tests are equivocal.

Ten-year follow-up of photorefractive keratectomy for myopia of more than -6 diopters.

PURPOSE To evaluate the long-term outcomes of excimer laser myopic photorefractive keratectomy (PRK) for myopia higher than -6 diopters (D). DESIGN A long-term (10-year) follow-up retrospective, interventional case series. METHODS The study included 267 eyes of 191 patients with myopia with spherical equivalent (SE) of more than -6 D treated with myopic PRK at the Instituto Oftalmológico de Alicante, Alicante, Spain, using the VISX 20/20 excimer laser (Santa Clara, California, USA). All patients were evaluated three months, one year, two years, five years, and 10 years after surgery. The main outcome measures were refractive predictability and stability, mean corneal keratometry, topographical cylinder, safety, efficacy, stability of visual acuity, and postoperative complications. RESULTS At 10 years, 156 (58%) of 267 eyes were within +/- 1.00 D and 209 (78%) were within +/- 2.00 D. One hundred and twenty-four eyes (46.4%) underwent retreatments because of overcorrection, regression, or both. The mean SE decreased (myopic regression) in eyes that did not undergo retreatment, with a mean magnitude of -1.33 +/- 2.0 D over 10 years (-1.13 +/- 0.20 D per year). One hundred and twenty-one (48.3%) of 267 eyes demonstrated increase in best spectacle-corrected visual acuity, and only eight eyes lost lines of vision because of cataract and posterior segment-related complications. The mean corneal haze score decreased gradually from 0.48 +/- 0.69 at three months to 0.09 +/- 0.33 at 10 years. CONCLUSIONS PRK for myopia of more than -6 D is a safe and effective procedure in the long-term.

Corneal aberrations after microincision cataract surgery

PURPOSE: To study the effect of microincision cataract surgery (MICS) on the optical quality of the cornea, characterized in terms of Seidel aberrations. SETTING: Instituto Oftalmológico de Alicante, Vissum, Alicante, Spain. METHODS: This study comprised 25 eyes of 25 patients with nuclear or corticonuclear cataract of grade 2+ to 4+ (Lens Opacities Classification System III). Microincision cataract surgery was performed using low ultrasound power through a 1.6 to 1.8 mm clear corneal incision placed on the axis of the positive corneal meridian. An Acri.Smart 48S intraocular lens (Acri.Tec) was implanted in all eyes. Seidel aberration root‐mean‐square (RMS) values were obtained with a 6.0 mm aperture using the CSO topographer (Costruzione Strumenti Oftalmici) preoperatively and 1 and 3 months postoperatively. RESULTS: The total RMS after MICS decreased slightly from a mean of 2.15 μm ± 2.51 (SD) preoperatively to 1.96 ± 2.01 μm postoperatively; the decrease was not statistically significant (P = 1.00). The difference between the corneal astigmatism from preoperatively (−0.80 ± 0.76 diopter [D]) to postoperatively (−0.63 ± 0.62 D) was not statistically significant (P = 1.00) nor were the differences in Seidel aberrations, coma, or higher‐order aberrations. CONCLUSION: Microincision cataract surgery did not degrade the optical quality of the cornea or induce a modification in corneal astigmatism, including the axis.

Clinical outcomes and intraocular optical quality of a diffractive multifocal intraocular lens with asymmetrical light distribution.

PURPOSE: To evaluate clinical outcomes and intraocular optical performance of a diffractive multifocal intraocular lens (IOL), Acri.Lisa 366D (Acri.Tec). SETTING: Vissum‐Instituto de Oftalmológico de Alicante, Alicante, Spain. METHODS: The study included 69 eyes (52 patients) with Acri.Lisa 366D IOLs. The intraocular optical quality in vivo was characterized by the difference between postoperative total and corneal optical aberrations. Visual and optical outcomes were evaluated 6 months postoperatively. The main outcomes measures were refractive defect, uncorrected and corrected distance acuities for far and near (40 cm), intraocular aberrations (root mean square [RMS]), modulation transfer function (MTF) values, point‐spread function, and Strehl ratio. RESULTS: The mean spherical equivalent (SE) was +1.22 diopters (D) ± 3.62 (SD) preoperatively and +0.39 ± 0.51 D/D postoperatively; 69.32% of eyes were within ±0.50 and 86.36%, within ±1.00 D. The mean acuities were as follows: uncorrected distance, 0.75 ± 0.20; best corrected distance, 0.94 ± 0.11; best distance‐corrected near, 0.90 ± 0.14. Near corrected acuity was J1 in 91.76% of eyes and J2 in 4.71%. The mean aberration values were total RMS, 1.45 ± 0.73 μm; spherical, 0.25 ± 0.10 μm; coma, 0.37± 0.21 μm. The mean Strehl ratio was 0.26 ± 0.05. The mean 0.5 MTF was 1.60 ± 0.63 cycles per degree (cpd) and the mean cutoff value, 50.25 ± 17.18 cpd. CONCLUSIONS: The Acri.Lisa 366D diffractive multifocal IOL gave good efficacy, predictability, and safety and excellent visual acuity at distance and near. An intraocular optical performance model showed good intraocular aberration, Strehl ratio, and MTF values.

Optical performance of monofocal and multifocal intraocular lenses in the human eye

PURPOSE: To study the optical performance of intraocular lenses (IOLs) in the human eye to ascertain how multifocality affects the optical performance of refractive and diffractive technologies and the relationship to pupil size. SETTING: Vissum‐Instituto de Oftalmológico de Alicante, Alicante, Spain. METHODS: Ten eyes each received the monofocal AcrySof MA60 IOL (Alcon) or 1 of the following multifocal pupil‐dependent IOLs: diffractive AcrySof ReSTOR (Alcon) or refractive ReZoom (Advanced Medical Optics). The intraocular optical quality in vivo with 3.0 mm and 5.0 mm pupils was characterized by comparing the means of the difference between the total and corneal optical aberrations 3 months postoperatively. The main outcomes measures were total, higher‐order, spherical, and coma aberrations (root‐mean‐square values); modulation transfer function values; point‐spread function; and the Strehl ratio. RESULTS: The ReZoom group had higher in vivo intraocular aberrations than the AcrySof ReSTOR and AcrySof MA60 groups (P = .022). The difference in spherical aberration between the AcrySof ReSTOR and ReZoom groups was statistically significant with 5.0 mm pupils (P = .003) and 3.0 mm pupils (P = .001). The AcrySof ReSTOR group had statistically significant lower coma aberration values with a 5.0 mm pupil (P = .012); there were no differences between IOLs with a 3.0 mm pupil (P = .185). CONCLUSIONS: Multifocal refractive IOLs resulted in higher intraocular aberrations. The hybrid refractive–diffractive IOL was the least affected by pupil diameter in terms of intraocular aberrations and showed significantly less increase in optical aberrations when the pupil was enlarged.

Ten years after Photorefractive Keratectomy (PRK) and Laser In Situ Keratomileusis (LASIK) for Moderate to High Myopia (Control-Matched Study)

Objective: To compare the long-term outcomes of photorefractive keratectomy (PRK) and laser in situ keratomilesis (LASIK) for myopia between −6 and −10 D. Methods: A retrospective, control-matched study including 68 eyes, 34 which underwent PRK and 34 LASIK, with myopia between −6 and −10 D, operated using the VISX 20/20 excimer laser, was performed. Optical zones of 5.5 to 6 mm were used. All PRK-treated eyes were matched with LASIK-treated eyes of the same age, spherical equivalent within ±1.25 D, sphere within ±1.5 D and cylinder within ±2.5 D. All patients were evaluated 3 months, 1 year, 2 years, 5 years and 10 years after surgery. The main outcomes measures were refractive predictability and stability, safety, efficacy and re-treatment rate. Results: At 10 years, 20 (71%) and 23 (88%) were within ±1.00 D after PRK and LASIK respectively. The re-treatment rate was 35% and 18% respectively. No eye lost more than two lines of BSCVA in both groups. The efficacy was 0.90 for PRK and 0.95 for LASIK. Conclusions: Both PRK and LASIK were safe for moderate myopia. LASIK demonstrated slightly better efficacy, predictability, and less rate of re-treatment after 10 years. The technical improvements should be taken into account when comparing these results with those obtained more recently.

Grading nuclear cataract opacity by densitometry and objective optical analysis

PURPOSE: To evaluate the optical quality and densitometric characteristics in eyes with early stages of crystalline lens opacification. SETTING: Vissum‐Instituto de Oftalmológico de Alicante, Alicante, Spain. METHODS: The study included 34 eyes of 24 consecutive patients with nuclear opacity (NO) between NO1 and NO3 on the Lens Opacities Classification System III, normal corneas, and no previous ocular surgery. Intraocular aberrations were obtained by subtraction between the total and corneal optical aberrations. Modulation transfer function (MTF) was measured using a double‐pass device. Lens photography and density (optical density units, Scheimpflug photography) were also evaluated. The main outcome measures were (1) spatial frequencies at 0.5 MTF and the cutoff point and (2) intraocular total and lower‐ and higher‐order aberrations (root mean square). RESULTS: There was an increase in lens density with the cataract grade (mean 96.7 ± 26.0 [SD], grade NO1; 125.1 ± 25.9, grade NO2; 167.3 ± 40.6, grade NO3). No statistically significant differences were found in intraocular higher aberrations between groups. Significant negative correlations were found between lens density and the spatial frequency at 0.5 MTF (r = −0.400, P = .026) or the cutoff MTF (r = −0.480, P = .006). CONCLUSIONS: The optical quality of eyes degraded with increasing cataract grade due to morphological changes such as an increase in lens density. Scheimpflug photography and MTF analysis helped objectively characterize early to moderate grades of nuclear cataract.

Ten-year Follow-up of Excimer Laser Surface Ablation for Myopia in Thin Corneas

PURPOSE To evaluate the long-term outcomes of excimer laser surface ablation performed on thin corneas. DESIGN Retrospective study. METHODS We included in the study 75 eyes (49 patients) with a preoperative central corneal thickness (CCT) thinner than 500 mum that had undergone surface ablation to correct their myopia and that had at least 10 years of follow-up. We evaluated the stability of visual acuity (VA) and refraction, the predictability, corneal keratometry, safety, efficacy, and postoperative complications at the examinations 3 months and 1, 2, 5, and 10 years after surgery. RESULTS Preoperative CCT was 481.54 +/- 15.7 microm (range, 438 to 499 microm). Preoperative spherical equivalent was -6.12 +/- 2.67 diopters (D) (range, -2 to -14 D). The best spectacle-corrected VA significantly improved (P < .01) during the follow-up. The uncorrected VA showed significant improvement in all visits when compared with the 3-month postoperative visit. Both the sphere and cylinder showed a slight but significant regression (P < .01) only in the comparison between 3 months and 10 years after the surgery. Ten years after the surgery, 30 eyes (40%) were within 0.50 D and 43 eyes (57.33%) were within 1.00 D of emmetropia. The safety index improved over the 10 year period and was always higher than 0.9. The efficacy index remained stable around 0.8. The topography did not show signs of corneal ectasia and the keratometry showed no increase in corneal power. Thirty eyes (40%) needed enhancement. CONCLUSION Surface ablation seems to be safe and effective to correct myopia in corneas thinner than 500 microm, with stable visual and refractive outcomes in a 10-year follow-up.

Design of short Spanish sentences for measuring reading performance: Radner-Vissum test

PURPOSE: To develop 24 short Spanish optotype sentences for the construction of a test based on the Radner reading test to simultaneously measure near visual acuity and reading speed. SETTING: Department of Refractive Surgery, Vissum‐Instituto de Oftalmológico de Alicante, Alicante, Spain. METHODS: Thirty‐one sentences were constructed in Spanish following the procedure defined by Radner to obtain sentence optotypes with comparable structure and the same lexical and grammatical difficulty. Sentences were statistically selected and standardized in 60 patients divided into 2 groups by educational level. Group A (30 patients) had a university education and Group B (30 patients), a primary school education. The interval of reading time was defined as the overall mean ±1.1 × SD. All sentences with a mean between 3.59 seconds and 4.04 seconds were selected for the reading charts. RESULTS: The mean age was 30.8 years ± 6.2 (SD) in Group A and 37.3 ± 10.7 years in Group B. The mean reading time was 3.8 ± 0.9 seconds in all patients, 3.5 ± 0.6 seconds in Group A, and 4.1 ± 1.0 seconds in Group B. CONCLUSION: The 24 short single Spanish sentences were highly comparable in syntactical structure; number, position, and length of words; lexical difficulty; and reading length.

Optical analysis of PresbyLASIK treatment by a light propagation algorithm

PURPOSE To evaluate the changes in the optical quality of corneas of hyperopic patients operated using central multifocal presbyLASIK treatment through the study of light patterns around the retinal plane. METHODS This study included eight hyperopic eyes that underwent central presbyLASIK surgery with Presby-one software using an H. Eye Tech Technovision excimer laser platform. Mean patient age was 57 years. Mean preoperative spherical equivalent refraction was 1.28 +/- 0.87 diopters (D). Mean distance decimal visual acuity with correction was 1.02 +/- 0.13 and without correction was 0.37 +/- 0.15. The optical quality was characterized by the Strehl ratio, the spot size on the retina, and objective decimal visual acuity calculated based on measured corneal topography using Fresnel propagation algorithm based on a realistic eye model. RESULTS The postoperative spherical equivalent refraction was -0.55 +/- 0.48 D. The distance decimal visual acuity with correction was 0.94 and without correction was 0.70. The pseudoaccommodation range was 1.60 +/- 0.40 D. A good Pearson correlation coefficient was obtained (r2 = 0.86) for the linear fit between the real and calculated decimal visual acuity for the eight eyes. The Strehl ratio value on the retinal plane increased after the surgery by a mean factor of 4.7. CONCLUSIONS With a complete characterization of the eye and a complete propagation algorithm (that takes into account all refractive surfaces in the eye at the same time), it is possible to evaluate the optical quality in eyes of patients who have undergone central presbyLASlK treatment.