Jorge L. Alió

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.

Laser in situ keratomileusis to correct high myopia

Purpose: To evaluate the effectiveness, predictability, and safety of laser in situ keratomileusis (LASIK) in 143 eyes with myopia from 8.00 to 20.00 diopters (D). Setting: Alicante Institute of Ophthalmology, University of Alicante School of Medicine, Alicante, Spain. Methods: This prospective study comprised 143 eyes (94 patients) that had LASIK with the Chiron Automated Corneal Shaper and the VISX 20/20 excimer laser using a multizone profile and a sutureless hinged corneal flap technique. Results: Uncorrected visual acuity was 20/40 or better in 45.0% of eyes 3 months postoperatively and in 46.4% at 6 months. Best corrected visual acuity (BCVA) improved by 0.07 at 3 and 6 months and was stable after 3 months. Mean spherical equivalent was ‐13.19 diopters (D) ± 2.89 (SD) preoperatively and +0.51 ± 1.63 D at 3 months and +0.18 ± 1.66 D at 6 months postoperatively. At 3 months, spherical equivalent was within 1.00 D of emmetropia in 57.5% of all eyes, 71.0% of eyes with a baseline refraction from ‐8.00 to ‐11.99 D (n = 59), 44.4% with a baseline refraction from ‐12.00 to ‐15.99 D (n = 54), and 53.0% of eyes with a baseline refraction from ‐16.00 to ‐20.00 D (n = 30). The respective 6 month percentages were 60.0, 72.4, 46.0, and 50.0%. The regression of effect was similar in all groups (approximately 0.50 D) between 1 and 3 months, although the high myopia group had further regression. Significant corneal steepening and an increase in corneal thickness occurred between 1 and 3 months. Flap thickness was always less than predicted with both the 130 and 160 &mgr;m plates, and achieved laser ablation was deeper than programmed. The relationships between postoperative refraction and preoperative keratometry and postoperative refraction and the difference in achieved versus programmed ablation were significant. Complications at 6 months included epithelial ingrowth, corneal flap melting, decentered ablation, and irregular astigmatism with loss of BCVA, although none was vision threatening. Conclusion: In this study, LASIK was effective and predictable in the correction of high myopia but was more accurate for myopia up to 12.00 D. Current surgical algorithms must be modified to improve predictability in higher corrections. Longer follow‐up is necessary to evaluate long‐term incidence of vision‐threatening complications.

Corneal Higher Order Aberrations: A Method to Grade Keratoconus

PURPOSE To use the anterior corneal surface higher order aberrations as a tool to detect and grade keratoconus using corneal map analysis videokeratoscopy. METHODS A prospective observational comparative study of 80 eyes was performed. The eyes were divided into two groups. Group A comprised 40 eyes of 20 asymptomatic individuals with no ocular pathology. Mean sphere was -0.03 diopters (D) (range: +0.75 to -0.75 D), mean cylinder was -0.27 D, mean average K was 43.28 D, and mean uncorrected visual acuity (UCVA) was 1.01. Group B comprised 40 eyes of 25 patients with keratoconus. Mean sphere was -3.70 D (range: +2.00 to -10.00 D), mean cylinder was -3.82 D, mean average K was 49.29, and mean best spectacle-corrected visual acuity (BSCVA) was 0.61. RESULTS In group A, mean root-mean-square (RMS) of spherical (Z4 and Z6), coma-like (Z3, Z5, and Z7), and higher order aberrations (Z3-7) were 0.38 microm, 0.35 microm, and 0.52 microm, respectively. In group B, mean RMS of spherical, coma-like, and higher order aberrations were 1.06 microm, 2.90 microm, and 3.14 microm, respectively, for a 6.0-mm simulated pupil diameter. Mean RMS differences between the two groups were 0.68 microm (P < or = .0002), 2.55 microm (P < or = .0001), and 2.61 microm (P < or = .0001) for spherical, coma-like, and total higher order aberrations, respectively. In group B, according to Amsler-Krumeich classification, the mean RMS of coma-like aberration was 1.87 microm in grade I (14 eyes), 2.97 microm in grade II (11 eyes), 3.46 microm in grade III (12 eyes), and 5.20 microm in grade IV (3 eyes). CONCLUSIONS Corneal higher order aberrations, especially coma-like aberrations, are significantly higher in eyes with keratoconus than normal eyes. Coma-like aberrations, with the aid of a corneal aberrometry map, are good indicators for early detection and grading of keratoconus.

Phakic anterior chamber lenses for the correction of myopia: a 7-year cumulative analysis of complications in 263 cases.

OBJECTIVE To perform a prospective, clinical trial to determine the potential cumulative complications of patients implanted with angle-supported phakic intraocular lenses (PIOLs) for the correction of myopia. DESIGN Nonrandomized, prospective, comparative trial. PARTICIPANTS Two hundred sixty-three eyes of 160 consecutive patients were included. INTERVENTION Angle-supported anterior chamber intraocular lenses were implanted into phakic eyes. MAIN OUTCOME MEASURES Night halos and glare were recorded. Central endothelial cell count, postoperative inflammation, applanation tonometry, cataract development, retinal detachment, and pupil ovalization were recorded by the same physician. RESULTS Night halos and glare were reported as significant by 20.2% at 1 year and 10% at year 7 of follow-up. This complication was significantly lower in the larger optical zone PIOL (ZSAL-4) than in the ZB5M/ZB5MF group (P < 0.05). Acute postoperative iritis was observed in 4.56% of cases. High intraocular pressure that required antiglaucoma medications appeared in 7.2% of cases. Central corneal endothelial cell density was significantly decreased at postoperative month 3 (P < 0.0001). The percentages of cell loss were 3.76% at month 3 and 1.83% at year 1, and then the percentages decreased by 1.37% more at year 2, 0.72% at year 3, 0.3% at year 4, 0.6% at year 5, 0.4% at year 6, and 0.56% at year 7. The total cumulative loss of central endothelial cells after 7 years was 8.37%. Pupil ovalization was present in 5.9% of cases, although smaller degrees of this complication were observed in another 10.3%. Retinal detachment appeared in 3% of cases. The PIOL explantation was decided in 11 cases (4.18%) because of cataract development (9 cases) and extreme pupil ovalization associated with severe glare (2 cases). The Kaplan-Meier cumulative survival analysis study showed an expected period free from complication of 86.5% for IOP elevation, 98.75% for endothelial cell count inferior to 1500 cells/mm2, 86.97% for pupil ovalization, 95.43% for retinal detachment, and 89.02% for explantation. CONCLUSIONS Angle-supported PIOL appeared to be well tolerated by the corneal endothelium with a low rate of other complications. Pupil ovalization seemed to be a specific problem for this type of PIOL.

Detection and Identification of Fungal Pathogens by PCR and by ITS2 and 5.8S Ribosomal DNA Typing in Ocular Infections

ABSTRACT The goal of this study was to determine whether sequence analysis of internal transcribed spacer/5.8S ribosomal DNA (rDNA) can be used to detect fungal pathogens in patients with ocular infections (endophthalmitis and keratitis). Internal transcribed spacer 1 (ITS1) and ITS2 and 5.8S rDNA were amplified by PCR and seminested PCR to detect fungal DNA. Fifty strains of 12 fungal species (yeasts and molds) were used to test the selected primers and conditions of the PCR. PCR and seminested PCR of this region were carried out to evaluate the sensitivity and specificity of the method. It proved possible to amplify the ITS2/5.8S region of all the fungal strains by this PCR method. All negative controls (human and bacterial DNA) were PCR negative. The sensitivity of the seminested PCR amplification reaction by DNA dilutions was 1 organism per PCR, and the sensitivity by cell dilutions was fewer than 10 organisms per PCR. Intraocular sampling or corneal scraping was undertaken for all patients with suspected infectious endophthalmitis or keratitis (nonherpetic), respectively, between November 1999 and February 2001. PCRs were subsequently performed with 11 ocular samples. The amplified DNA was sequenced, and aligned against sequences in GenBank at the National Institutes of Health. The results were PCR positive for fungal primers for three corneal scrapings, one aqueous sample, and one vitreous sample; one of them was negative by culture. Molecular fungal identification was successful in all cases. Bacterial detection by PCR was positive for three aqueous samples and one vitreous sample; one of these was negative by culture. Amplification of ITS2/5.8S rDNA and molecular typing shows potential as a rapid technique for identifying fungi in ocular samples.

Distance and near contrast sensitivity function after multifocal intraocular lens implantation.

Purpose: To evaluate contrast sensitivity at distance and near after multifocal intraocular lens (IOL) implantation. Setting: Ophthalmologic Institute of Alicante, University Miguel Hernández, Alicante, Spain. Methods: Contrast sensitivity was measured with the Stereo Optical Functional Acuity Contrast Test at distance and near in 21 patients with a refractive multifocal IOL (Array SA‐40N, AMO). A control group with a monofocal IOL (SI‐40NB, AMO) was also studied to allow comparison of results. Contrast sensitivity was measured 1, 3, 6, 12, and 18 months after IOL implantation. Results: There was a statistically significant greater reduction in contrast sensitivity at distance at all spatial frequencies in the multifocal group than in the monofocal group during the first month. At 3 months, contrast sensitivity at 12 and 18 cycles per deg remained reduced in the multifocal group; contrast sensitivity at the other frequencies did not differ from that in the monofocal group (P > 0.1). At 6, 12, and 18 months, contrast sensitivity at all spatial frequencies was not significantly different between groups (P > 0.1). There was a statistically significant greater reduction in near contrast sensitivity in the multifocal group than in the monofocal group at all spatial frequencies during the first and third month after surgery (P < .01). No statistically significant differences were found between groups after 6 months (P > 0.1). Contrast sensitivity at distance and near in the multifocal group improved over time (P < .01). Conclusions: The Array IOL provided contrast sensitivity at distance comparable to that obtained with the monofocal IOL between 3 and 6 months after implantation. Near contrast sensitivity improved over time but was always lower than at distance and in the monofocal near‐corrected patients, which is acceptable to avoid near visual function degradation.

Intracorneal ring segments for keratoconus correction: Long-term follow-up

PURPOSE: To evaluate long‐term results and stability of intracorneal ring segment (Intacs) implantation for keratoconus correction. SETTING: Vissum, Instituto Oftalmológico de Alicante and University of Miguel Hernandez, Alicante, Spain. METHODS: This retrospective study comprised 13 eyes operated on between April 2000 and December 2001 that had Intacs implantation for keratoconus correction. The outcomes were evaluated at 6, 12, 24, and 36 months in all eyes and at 48 months (6 eyes). RESULTS: Mean best spectacle‐corrected visual acuity (BSCVA) increased from 0.46 (20/50) preoperatively to 0.66 (20/30) postoperatively (P≤.001). Mean decrease of inferior‐superior (I‐S) asymmetry was 2.81 diopters (D) (P≤.02), and the average K‐value was 3.13 D (P≤.001). Mean difference between 6 and 36 months (stability) showed no significant difference regarding BSCVA (P≤.5) and I‐S asymmetry (P≤.6). Although a significant increase was noticed in the average K by 1.67 D (P≤.002), at 36 months it did not reach the initial preoperative values. CONCLUSION: Intacs increased the BSCVA and decreased I‐S asymmetry with stability up to 36 months. In spite of the decrease of the K‐values at 6 months, a further significant increase was detected 36 months after surgery.

Corneal sensitivity after photorefractive keratectomy and laser in situ keratomileusis for low myopia

PURPOSE To evaluate and compare the recovery of postoperative corneal sensitivity after laser in situ keratomileusis and photorefractive keratectomy for the correction of low myopia. METHODS In a prospective study, 17 consecutive eyes (17 patients) underwent laser in situ keratomileusis to correct myopia ranging from -3.25 to -6.75 diopters, and another 18 consecutive eyes (18 patients) underwent photorefractive keratectomy to correct myopia from -3.12 to -7.00 diopters. Corneal sensitivity was tested preoperatively and 1 week and 1, 3, and 6 months postoperatively using the Cochet-Bonnet esthesiometer. Corneal sensitivity was tested at the center of the cornea, and in four additional central points 2 mm from the corneal center (nasal, inferior, temporal, and superior). RESULTS Corneal sensitivity after laser in situ keratomileusis was reduced at the ablated zone during the first 3 months after surgery (Wilcoxon rank sum test, P < .05), and only after 6 months it returned to its preoperative values. However, corneal sensitivity recovered its preoperative values 1 month after photorefractive keratectomy (Wilcoxon rank sum test, P > .05), except for the central corneal point, where 3 months were required. Comparing both groups, corneal sensitivity was more depressed after laser in situ keratomileusis than after photorefractive keratectomy during the first 3 months (Mann-Whitney test, P < .05), except for the nasal central point, although no differences were found between both groups at 6 months (P > .05). CONCLUSIONS In the correction of low myopia, corneal sensitivity at the ablated zone was more depressed after laser in situ keratomileusis than after photorefractive keratectomy during the first 3 months after surgery. Only after 6 months were corneal sensitivity values similar in both groups.

Toric phakic intraocular lens: European multicenter study.

OBJECTIVE To evaluate safety, efficacy, predictability, stability, complications, and patient satisfaction after implantation of Artisan toric phakic intraocular lenses (TPIOLs) for the correction of myopia or hyperopia with astigmatism. DESIGN Prospective, nonrandomized, comparative (self-controlled) multicenter trial. PARTICIPANTS Seventy eyes of 53 patients (mean, 35 years; range, 22-59 years) with preoperative spherical equivalent between +6.50 and -21.25 diopters (D) and cylinder between 1.50 and 7.25 D. METHODS Seventy eyes underwent implantation of a TPIOL with an optical zone of 5.0 mm (Artisan, Ophtec, Groningen, The Netherlands). The dioptric power of the intraocular lens was calculated by considering refraction, keratometry, and anterior chamber depth. The follow-up was 6 months in all cases. Lenses were available in powers ranging from +12.0 D to -23.5 D (spherical equivalent) in 0.5-D increments, with additional cylinder from 1.0 D to 7.0 D, also in 0.5-D increments. MAIN OUTCOME MEASURES The main parameters assessed were best spectacle-corrected visual acuity (BSCVA), uncorrected visual acuity (UCVA), refraction, endothelial cell count (ECC), intraocular pressure, slit-lamp biomicroscopy, indirect ophthalmoscopy, subjective complaints, and patient satisfaction. RESULTS Eyes were divided into group A, myopia (n = 48), with an average preoperative spherical equivalent of -8.90 +/- 4.52 D, and group B, hyperopia (n = 22), with an average preoperative spherical equivalent of +3.25 +/- 1.98 D. No eyes in either group experienced a loss in BSCVA, and 46 eyes gained 1 or more lines of their preoperative BSCVA. In 62 eyes (88.6%), UCVA was 20/40 or better. There was a significant reduction in spherical errors and astigmatism in all cases after surgery. All eyes of both groups were within +/-1.00 D of target refraction, and 51 eyes (72.9%) were within +/-0.50 D of target refraction. There was a 4.5% mean total loss of ECC during the first 6 months. No serious complications were observed. Overall patient satisfaction was very high. CONCLUSIONS Six-month clinical trial results demonstrate that implantation of the Artisan TPIOL safely, predictably, and effectively reduced or eliminated high ametropia and astigmatism with one procedure. The refractive effect was stable at 6 months after surgery.

Contrast sensitivity after laser in situ keratomileusis

Purpose: To evaluate the effect on contrast sensitivity function of laser in situ keratomileusis (LASIK) for the correction of myopia. Setting. Alicante Institute of Ophthalmology, University of Alicante, Spain. Methods: Fourteen eyes of 10 patients had LASIK to correct myopia ranging from 6.00 to 19.50 diopters (D). Mean preoperative myopia was 10.39 D ± 3.69 (SD). Contrast sensitivity was tested preoperatively and 1, 3, and 6 months postoperatively using the CVS‐1000E contrast sensitivity unit (VectorVision). Results: Contrast sensitivity decreased 1 month postoperatively; the decrease was significant only at the low and intermediate spatial frequencies of 3 and 6 cycles per degree (cpd) (P = .034 and .030, respectively). Starting from the first month, there was rapid recovery of contrast sensitivity and at the third month, no statistically significant decrease at all spatial frequencies. Six months after surgery, there was an increase in contrast sensitivity values at 3, 12, and 18 cpd, although the changes were not significant. Conclusion: Although LASIK decreased contrast sensitivity values at low and intermediate spatial frequencies for 1 month after surgery, these values rapidly returned to the preoperative values at 3 months. The improvement at certain frequencies at 6 months suggests that LASIK can improve the quality of vision in eyes with moderate and high myopia.