Long-term outcomes of intrastromal corneal ring segment implantation for post-LASIK ectasia

PurposeTo report the long-term results of intrastromal corneal ring segments (ICRS) for postoperative LASIK ectasia.MethodIn this retrospective interventional cases series, 8 eyes of 6 patients who underwent femtosecond laser-assisted ICRS implantation for post-LASIK ectasia were enrolled. Main outcome measures were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent refraction, and average keratometry (K_avg) values were assessed.ResultsMean ± SD follow-up was 67 ± 21 months (range, 36–96 months). The mean UDVA, CDVA, spherical equivalent refraction, and K_avg values were significantly improved at all postoperative visits when compared to baseline values. No serious complications were observed during follow-up.ConclusionOur long-term findings showed that ICRS yielded improvements in visual acuity, refractive status, and keratometric values without any progression in cases with post-LASIK corneal ectasia.     

Comparison of visual acuity and higher-order aberrations after femtosecond lenticule extraction and small-incision lenticule extraction

PurposeTo compare postoperative visual acuity and higher-order aberrations (HOAs) after femtosecond lenticule extraction (FLEX) and after small-incision lenticule extraction (SMILE).MethodsMedical records of refractive lenticule extraction patients were retrospectively reviewed. Twenty patients were treated with FLEX. A comparable group of 20 SMILE patients were retrospectively identified. Only one eye of each patient was randomly chosen for the study. Visual acuity, subjective manifest refraction and corneal topography before and 6 months after the surgery were analyzed for both groups. Total HOAs, spherical aberrations, coma and trefoil were calculated from topography data over the 4- and 6-mm-diameter central corneal zone.ResultsThe mean preoperative SE was −4.03 ± 1.61 in the SMILE group and −4.46 ± 1.61 in the FLEX group. One year after surgery, the mean SE was −0.33 ± 0.25 in the SMILE group and −0.31 ± 0.41 in the FLEX group (p = 0.86). In the SMILE group a greater number of eyes were within ±0.50 D of the target refraction (95% versus 75%); however, the difference was not statistically significant (p = 0.18). Furthermore, 80% of FLEX eyes and 95% of SMILE eyes had an uncorrected distance visual acuity of 20/25 or better (p = 0.34). Total HOAs, spherical aberration, coma and trefoil increased postoperatively in both groups. However, there was no statistically significant difference between the groups preoperatively and postoperatively.ConclusionFLEX and SMILE result in comparable refractive results. In addition, corneal aberrations induced by different techniques of lenticule extraction seemed similar to each other.     

Overnight orthokeratology with two brands of reverse-geometry contact lenses

PurposeTo evaluate the refractive and corneal topographical changes of overnight orthokeratology in myopia with two brands of contact lenses.MethodsFourty-four eyes of 22 myopic patients with manifest refraction spherical equivalent (MRSE) of −1.00 to −5.00 D (cylinder ≤ −1.0) were fitted with either DreamLens (Hanita Lenses Investments, Hanita, Israel) (group A) or Rinehart–Reeves (R&R; Danker Laboratories, Sarasota, FL) (group B) reverse-geometry lenses. Each subject eye was evaluated in regards to the uncorrected and corrected distance visual acuities, manifest refraction, slit lamp biomicroscopy, and corneal topography at each follow-up examination.ResultsThe follow-up was 1 year. For groups A and B, the mean uncorrected distance visual acuity was −0.02 ± 0.10 log MAR (20/20) and −0.08 ± 0.12 log MAR (20/20) respectively at year-1 examination. The mean MRSE decreased from −2.70 ± 0.9 D to −0.50 ± 0.08 D in group A and −3.1 ± 1.1 to −0.62 ± 0.18 D in group B at week-1; and remained stable thereafter in each group. For both groups, starting with week-1, the mean anterior best-fit sphere (ABFS) was statistically significantly flatter from baseline. A high correlation was found between the change in apical corneal power (ACP) and MRSE (r₁ = 0.79, r₂ = 0.71), and there was a good correlation between the change in ABFS and MRSE (r₁ = 0.67, r₂ = 0.64) in both groups. No significant ocular adverse events were observed during study.ConclusionsBoth types of contact lenses safely and effectively decreased the myopic refractive error at 1 year follow-up. The refractive effect was mainly induced by the changes in the anterior corneal shape and the ACP.     

Long term results of Epi-LASIK and LASEK for myopia

PurposeTo evaluate the long term clinical and confocal results of mechanical (Epi-LASIK) versus alcohol-assisted laser epithelial keratomileusis (LASEK) for correction of myopia.SettingGazi University Medical School, Department of Ophthalmology, Ankara, Turkey.DesignRetrospective study.MethodsTwenty-two eyes treated with LASEK and twenty eyes treated with Epi-LASIK were evaluated with a mean follow-up duration of 45 months. Mechanical separation of the epithelium was performed with Lasitome epithelial separator, and alcohol-assisted separation with 25 s application of 18% alcohol. Laser ablation was performed with the ESIRIS laser. All patients were examined daily until epithelial closure; at 1, 3, 6, and 12 months; and every year subsequently. Main outcome measures were uncorrected visual acuity (UCVA), manifest refraction, haze, and gray scale value in confocal microscopy, efficacy and safety indexes.ResultsPreoperative myopic spherical equivalent refraction was −4.65 ± 1.74 D in the LASEK and −3.87 ± 1.30 D in the Epi-LASIK-treated eyes (p = 0.36). Of both LASEK and Epi-LASIK-treated eyes, 95% achieved 20/25 or better final UCVA. The grade of haze and mean gray scale value in confocal microscopy were similar in LASEK and Epi-LASIK-treated eyes at all postoperative periods. The efficacy index was 0.94 in LASEK group and 0.96 in Epi-LASIK group (p = 0.44). The safety index was 1.01 in LASEK group and 1.02 in Epi-LASIK group (p = 0.42).ConclusionsBoth LASEK and Epi-LASIK offer safe and effective correction of myopia in the long term.     

Efficacy of two silicone-hydrogel contact lenses for bandage use after photorefractive keratectomy

PurposeTo evaluate the efficacy of two silicone hydrogel (SiH) contact lenses, approved for continuous wear for one week, following photorefractive keratectomy (PRK).MethodsForty seven myopic patients (94 eyes) undergone bilateral PRK were enrolled in this prospective, double-masked, comparative study. One eye of each patient was fitted with a Lotrafilcon B lens (Ciba Vision, Duluth, US; 30-day recommended replacement) whereas the fellow eye was fitted with an Asmofilcon A lens (Menicon, Nagoya, Japan; 14-day recommended replacement). Epithelial defect size was assessed using slit lamp biomicroscopy on the day of surgery and at days 1–4 post-operatively. Uncorrected and best-corrected visual acuity and retinal straylight (C-Quant, Oculus Optigerate, Germany) were evaluated pre-operatively and one month post-operatively.ResultsAverage epithelial defect size for Asmofilcon A and Lotrafilcon B was 25.5 ± 11.0 mm² vs. 27.1 ± 9.9 mm² at day 1 (p = 0.007) and 6.3 ± 7.0 mm² vs. 9.2 ± 9.5 mm² at day 2 (p = 0.012) post-operatively. Re-epithelialization at day 3 was completed in 87.2% of the eyes fitted with Asmofilcon A lenses, compared to 74.5% with Lotrafilcon B lenses (p = 0.012). At the 3rd post-operative day 29.8% of re-epithelialized eyes showed irregular suture with Lotrafilcon B, compared to 12.8% eyes with Asmofilcon A lenses (p < 0.001). Finally, no statistically significant differences were found post-operatively between the two lenses retinal straylight (p = 0.98) and best-corrected visual acuity (p = 0.68).ConclusionsSiH lenses can be used as an effective bandage after PRK due to the limited time requested for achieving complete corneal re-epithelialization. Faster and smoother epithelial healing is provided with Asmofilcon A over Lotrafilcon B lenses.     

The effects of soft contact lens use on cornea and patient's recovery after autograft pterygium surgery

PurposeTo investigate usage of soft contact lens (SCL) on post-operative pain relief and daily, activity due to pterygium surgery.MethodsAutograft pterygium surgery was performed to 63 eyes of 63 patients. After surgery in 30, eyes of 30 patients in group-1, SCL was placed on the cornea. In 33 patients of group-2, antibiotic, pomade was applied and tightly covered with bandage. Follow-up visits were performed on 24th and, 48th h after the surgery. Re-epithelization time and pain scores were compared.ResultsPatients’ 24th h pain score was 2.96 ± 0.76 in group-1, and 4.15 ± 0.75 in group-2. The mean, pain score for 48 h was 1.66 ± 0.66 in group-1, and 2.96 ± 0.68 in group-2. Patients’ pain scores for, both 24th h and 48th h were lower in group-1 (p < 0.01). The mean re-epithelization times in, group 1 and 2 were 48 and 56.7 h, respectively. Corneal re-epithelization is improved in patients, with SCL compared to group 2.ConclusionSCL seems effective on reducing post-operative pain and eye stinging, and may accelerate, corneal re-epithelization and maintaining daily activities.     

The accuracy of Goldmann applanation tonometry over silicone hydrogel contact lenses in patients with glaucoma

PurposeTo investigate the accuracy of measuring intraocular pressure over a silicone hydrogel contact lens using Goldmann applanation tonometry in eyes with glaucoma.MethodsThis was a prospective, randomized study and enrolled 28 patients (28 right eyes) with primary open angle glaucoma. Intraocular pressure was taken with and without a silicone hydrogel contact lens (−0.50 D), in situ (using Goldmann applanation tonometry), in a randomized order of measurements. Statistical analysis was performed using paired t-test and Bland–Altman plot.ResultsThe mean difference (± standard deviation) found between intraocular pressure measurement without (mean 16.7 ± 3.2 mmHg) and with (mean 17.3 ± 3.0 mmHg) contact lens was found to be −0.57 ± 2.3 mmHg (95% confidence interval, −1.5 to 0.3). No significant statistical difference was found between the two groups with paired t-test (p = 0.19). The Bland Altman plot showed some evidence of increasing variability of differences between two measures of intraocular pressure, with increasing intraocular pressure. The 95% limits of agreement of the Bland Altman plot were unacceptably large (−5 mmHg to 3.9 mmHg).ConclusionAgreement between Goldmann applanation tonometry with and without contact lenses seems to be poor in patients with glaucoma, especially for high intraocular pressure.     

Comparison of corneal hysteresis and corneal resistance factor after small incision lenticule extraction and femtosecond laser-assisted LASIK: A prospective fellow eye study

PurposeTo compare corneal hysteresis (CH) and corneal resistance factor (CRF) between eyes treated with small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (femto-LASIK).SettingBeyoğlu Eye Training and Research Hospital.DesignProspective comparative case series.MethodsSixty eyes from 30 patients with bilateral myopia or myopic astigmatism were studied. Inclusion criteria were spherical equivalent of subjective manifest refraction (SE) <10 diopters (D) and a difference ≤0.50 D between the SEs of both eyes. One eye of each patient was treated with SMILE, and the fellow eye underwent femto-LASIK. Randomization was performed using a sealed envelope system. The main outcome measures were CH and CRF measured preoperatively and postoperatively (1 and 6 months).ResultsPreoperative SE was similar in both groups (p = 0.852). CH and CRF values were reduced postoperatively in both groups compared to their corresponding preoperative values (p < 0.001). At the 6-month follow-up visit, the mean CH values in the SMILE and femto-LASIK groups were 8.95 ± 1.47 and 9.02 ± 1.27, respectively (p = 0.852), and the mean CRF values were 7.77 ± 1.37 and 8.07 ± 1.26, respectively (p = 0.380).ConclusionCH and CRF decreased after SMILE. There were no differences between SMILE and femto-LASIK treatments in postoperative CH or CRF values.     

Small optical zones with aspheric profiles in laser refractive surgery for myopia: A surgical outcome and patient satisfaction study

PurposeTo assess the outcomes of small optical zone (OZ) ablations used in conjunction with large transition zones (TZ) and a highly aspheric treatment profile.MethodsInterventional case series of 39 consecutive patients with myopia or myopic astigmatism. Patient data included pre and postoperative refraction and visual acuities, laser treatment settings and pre and postoperative corneal topography as well as questionnaire responses about the use of glasses and the quality of vision postoperatively.ResultsThe mean preoperative spherical equivalent was −4.50 ± 2.11 dioptres (D) and the mean OZ and TZ diameters were 4.5 ± 0.5 mm and 8.1 ± 0.4 mm, respectively. The mean patient age was 40.7 ± 10.4 years. Manifest spherical refraction was within ±0.5 D in 87% of patients (±1.0 D in 99%) and cylindrical refraction within 0.5 D in 79% (≤1.0 D in 95%). The need to wear distance glasses postoperatively was associated with dissatisfaction with the quality of daytime vision (p = 0.05) and unhappiness with night vision was associated with symptoms of halos (p = 0.03) and starbursts (p = 0.02). The proportion of patients reporting symptoms of dysphotopsias included: ghosting 0%; glare 2%; halos 10%; and starbursts 15%. There was a significant difference in the measured mean effective OZ diameter (4.8 ± 0.3 mm) compared to the mean programmed OZ (4.5 ± 0.5 mm, p = 0.00).ConclusionsSmall ablation zones, when used in conjunction with a large diameter TZ, do not lead to a greater incidence of unwanted visual phenomena over that reported by many studies with larger OZs.     

Near complete visual recovery and refractive stability in modern corneal transplantation: Descemet membrane endothelial keratoplasty (DMEK)

ObjectiveTo report the 6 months results of a large prospective study on Descemet membrane endothelial keratoplasty (DMEK) for management of corneal endothelial disorders.MethodsDMEK was performed in 300 consecutive eyes with Fuchs endothelial dystrophy, bullous keratopathy or previous corneal transplant failure. Best spectacle corrected visual acuity (BSCVA), refractive outcome and endothelial cell density (ECD) were evaluated before and at 1, 3, and 6 months after surgery. Intra- and postoperative complications were documented.ResultsAt 6 months, 98% of eyes reached a BCVA of ≥20/40 (≥0.5), 79% ≥20/25 (≥0.8), 46% ≥20/20 (≥1.0), and 14% ≥20/18 (≥1.2) (n = 221). The pre- to 6 months postoperative spherical equivalent (SE) showed a +0.33D (±1.08D) hyperopic shift (P = 0.0000). Refractive stability was shown at 3 months after DMEK, i.e. no significant change in SE (P = 0.0822) or refractive cylinder (P = 0.6182) at 3 versus 6 months follow-up. Donor ECD showed a decrease from 2561 (±198) cells/mm² before, to 1674 (±518) cells/mm² at 6 months after surgery (n = 251) (P = 0.0000). The main complication was (partial) graft detachment occurring in 31 eyes (10%). Secondary ocular hypertension was seen in 13 eyes (6%): 6 induced by air-bubble dislocation posterior to the iris and 4 induced by steroids. Secondary cataract requiring phaco-emulsification developed in 3 out of 63 (5%) phakic eyes.ConclusionsDMEK may provide a refractively neutral near complete, rapid visual rehabilitation with ECDs similar to earlier endothelial keratoplasty techniques. This combined with a relatively low complication rate, would indicate that DMEK is a safe and effective treatment for corneal endothelial disorders.     

Examination of ocular biomechanics with a new Scheimpflug technology after corneal refractive surgery

PurposeTo analyze the early results of a new device measuring ocular biomechanics after corneal refractive surgery.Patients and methodsThirty nine refractive surgery patients were enrolled in the study (age: 32.6 ± 9.9 years). Laser in situ keratomileusis (LASIK) was performed on 52 eyes of 26 patients and photorefractive keratectomy (PRK) was done on 26 eyes of 13 patients. Ten device-specific biomechanical parameters, intraocular pressure (IOP) and pachymetry were measured preoperatively and at day 1, week 1 and month 1 after the surgeries with a new technology based on Scheimpflug imaging (CorVis ST, Oculus).ResultsIn case of LASIK, the day after the procedure, radius values showed significant differences compared to preoperative data. One month after surgery, radius values, velocity of the second applanation and pachymetry showed significant differences compared to preoperative data. In case of PRK, the day after the procedure, significant differences in IOP, maximum amplitude at the apex, A1 time, A2 velocity and highest concavity time were measured. After 1 month of PRK, there were no differences in the parameters compared to preoperative data except pachymetry.ConclusionsWe observed that some specific biomechanical parameters changed measured with CorVis ST after LASIK and PRK, in the early postoperative time. However, most of these parameters remain unchanged after one month of LASIK and PRK compared to preoperative data.     

Intraocular pressure measurement with ocular response analyzer over soft contact lens

PurposeTo compare intraocular pressure (IOP) measured with ocular response analyzer (ORA) with and without soft contact lenses (CL) on eye.MethodsGoldmann correlated intraocular pressure (IOPg) and corneal compensated intraocular pressure (IOPcc) were measured in 56 eyes of 28 subjects without any ocular pathology, using ORA. One eye was fitted with Narafilcon A (1-Day Acuvue True Eye, Johnson & Johnson) and the other eye with Nelfilcon A (Daily AquaComfort Plus, Ciba Vision), each with −3.00D and IOPg and IOPcc were again measured over CL. The variation in the IOP with and without CL was determined.ResultsOut of 28 subjects, 54% (15) were female. Mean age of the subjects was 29.4 ± 9.8 years. Both the IOPg and IOPcc when measured with CL, were found statistically significantly lower than without CL (p < 0.05). In subjects wearing Narafilcon A lens, IOPg and IOPcc were found 0.88 ± 2.04 mmHg and 1.55 ± 2.16 mmHg lower than without CL, respectively. Similarly, with Nelfilcon A lens, IOPg and IOPcc were found to be 1.03 ± 1.93 mmHg and 1.62 ± 3.12 mmHg lower, respectively. IOPcc was highly affected and underestimated by more than 3 mmHg in upto 36% of the subjects.ConclusionMeasurement of IOP over minus (−3.00D) CL with ORA is dependent upon CL properties when measured in normal IOP population. It showed lower IOP over Narafilcon A and Nelfilcon A soft CL in comparison to the pressures measured without lenses. IOPg was found less affected by CL. For the accurate measurement of IOP with ORA, CL should be removed.     

Scleral contact lenses for visual rehabilitation after penetrating keratoplasty: Long term outcomes

PurposeTo evaluate the success rate of highly gas permeable scleral contact lenses (SCL) for visual rehabilitation after penetrating keratoplasty (PK), over a period of up to 9 years.MethodsA total database of 31 consecutive patient fitted with SCL between January 2004 and December 2009 was retrospectively reviewed. Demographic data, etiology prior to lens fitting, visual outcomes, follow up time and complications were analyzed.ResultsAll eyes were fitted due to inadequate spectacle-corrected vision after successful penetrating keratoplasty or failure of other contact lens modalities. Out of 31 patients fitted, 28 (33 eyes) continue to wear SCL for periods between 0.5 and 8.8 years. The mean duration of follow-up after contact lens fitting was 5.2 ± 2.2 years. The mean age of corneal graft was 17.6 ± 11.4 years (range 4.3–42), and the mean interval between PK and initial contact lens fitting was 12.2 ± 10.7 years (range 0.7–36.0). The average steepest keratometry of our cohort was 55.0 ± 7.5 diopter (D) and the refractive astigmatism was 8.0 ± 4.4 D. The mean contact lens corrected visual acuity (BCVAcl) was 0.78 ± 0.25 (range 0.3–1.2). Twenty-three (82%) patients achieved a functional vision of 0.5 or more.During the studied period, ten (30.0%) eyes presented at least one graft rejection episode and two eyes (6%) had an episode of microbial keratitis. Corneal transplants of 20 years or more show a higher rate of refits due to ectasia recurrence.ConclusionsScleral lenses should be considered as lens of choice in eyes with complex corneal geometry, as besides visual rehabilitation, their use may delay or prevent further surgical involvement.     

Assessment of corneal endothelial cell density in patients with keratoconus not using contact lenses

PurposeTo assess the corneal endothelial cell density (ECD) in keratoconus patients with no history of contact lens use.SettingYuzuncu Yil University, School of Medicine and Van Training and Research Hospital, Department of Ophthalmology, Van, Turkey.DesignCross-sectional controlled study.MethodsThe eyes of 65 patients with the diagnosis of keratoconus with no history of contact lens wear and the eyes of 40 healthy controls were prospectively examined using the Heidelberg Retinal Tomography Rostock Cornea Module (HRT3/RCM). The average ECD from the two groups were then compared.ResultsOf the cases with keratoconus, 44 (67.7%) were men and 21 (32.3%) were women. The mean age was 20.9 ± 6.8 (range = 10–41) years. Of the controls, 28 (70%) were men and 12 (30%) were women. The mean age was 23.9 ± 5.8 (range = 14–35) years. Of the 65 eyes with keratoconus, 19 (29.2%) had mild keratoconus, 21 (32.3%) had moderate keratoconus, and 25 (38.5%) had severe keratoconus. The mean ECD was 2731.6 ± 303.2 cells/mm² in cases with keratoconus and 2664.9 ± 319.5 cells/mm² in controls. There was no difference between the densities (unpaired t-test, P = 0.4). No significant relationships were found between the ECD data and central corneal thickness or steepest keratometric.ConclusionsEndothelial cell density was unaltered in keratoconic patients without a history of contact lens use when compared with healthy controls. Change in ECD is independent from the central corneal thickness and the stage of keratoconus.     

Comparison of conventional method of contact lens fitting and software based contact lens fitting with Medmont corneal topographer in eyes with corneal scar

PurposeTo compare conventional method of contact lens fitting with software based contact lens fitting using Medmont corneal topographer in eyes with nebular and macular corneal scars.MethodsFifteen participants who were diagnosed with nebular and macular scars were fitted with rigid gas permeable lenses using conventional method of contact lens fitting. During the lens dispensing visit, participants underwent Medmont corneal topography. Agreement between the two methods of contact lens fitting was studied.ResultsParameters of contact lenses which were concluded using conventional method was compared to that of software based fitting. Mean difference in base curve of contact lens between the two methods was 0.094 mm ± 0.147 mm (95% CI: +0.383 to −0.194). Mean difference in diameter of contact lens between the two methods was 0.16 mm ± 0.172 mm (95% CI: +0.497 to −0.177). Contact lens parameters that were achieved using two different methods of fitting showed good correlation. Correlation coefficients, as comparison of two methods in base curve and diameter were 0.96 (P < 0.05) and 0.94 (P < 0.05), respectively.ConclusionSoftware based contact lens fitting would be useful for contact lens practitioners to predict initial base curve of contact lens in corneal scars.     

Efficacy of spherical aberration correction based on contact lens power

PurposeTo investigate the efficacy of spherical aberration (SA) correction with aspheric contact lenses (aspheric lenses) based on lens power, and compare the results with those of spherical contact lenses (spherical lenses).MethodsOcular higher-order aberrations were measured with a wavefront sensor, in 11 myopic subjects wearing an aspheric lens (Medalist Fresh fit (PUREVISION 2 HD); Bausch + Lomb) or a spherical lens (ACUVUE Oasys; Johnson & Johnson). Six different lens powers (−7.00 diopters (D), −5.00 D, −3.00 D, −1.00 D, +1.00 D, +3.00 D) were used for all subjects. The amount of SA correction from the contact lens at each power was calculated as the difference between SA with the contact lens on-eye and SA of the eye alone.ResultsFor the spherical lenses, SA correction was close to 0.00 μm for the +1.00 D lens, became more positive as the labeled lens power increased and became more negative as the labeled lens power decreased. For the aspheric lenses, SA correction was consistent, from −0.15 to −0.05 μm, for all lens powers except for the −1.00 D lens. SA correction for the spherical and aspheric lenses was significantly different at −7.00 D (p = 0.040), −3.00 D (p = 0.015), −1.00 D (p < 0.001), +1.00 D (p = 0.006), and +3.00 D (p < 0.001) powers.ConclusionAn aspheric lens is capable of correcting SA at different lens powers, and has SA correction in the range of −0.15 to −0.05 μm over a 6 mm aperture.     

Distribution of radii of curvature of anterior and posterior best fit sphere in a normal population: The Tehran Eye Study

PurposeTo determine the distribution and determinants of the radii of curvature of the anterior and posterior best fit spheres (ABFS and PBFS) of the cornea in a sample from the general normal population of Tehran.MethodsA stratified random cluster sampling was used to select samples from the first 4 districts of Tehran proportionate to the population of each stratum. We examined the distribution of the ABFS and PBFS, as measured with the Orbscan II in different groups of age, sex, and refractive error, and determined their relationship with other variables by using both univariate and multiple regression analyses. Valid data was collected from 800 eyes, and analyses were done with data from 399 right eyes only.ResultsMean ABFS and PBFS in the studied sample were 43.31 ± 1.79 D and 52.67 ± 3.04 D, respectively. ABFS increased with age while PBFS showed no significant association; both showed significant inter-sex differences. In the multiple linear regression model, both ABFS and PBFS significantly correlated directly with age and average keratometry, and inversely with corneal diameter; PBFS correlated directly with anterior chamber depth as well. Mean PBFS/ABFS ratio was 1.22 ± 0.05 which significantly decreased with age and was significantly higher in females.ConclusionKnowledge of normal ranges of ABFS and PBFS and their determinants, including age, mean keratometry, and corneal diameter, as well as the choice of measurement device, is necessary for comparing information from different populations and interpreting results.     

Bitoric rigid gas permeable contact lenses in the optical management of penetrating keratoplasty

PurposeThe purpose of this study was to evaluate the complexity and effectiveness of fitting bitoric rigid gas permeable contact lenses (RGPCLs), compared to spherical RGPCLS, when used in the correction of high amounts of post-penetrating keratoplasty astigmatism.MethodsRecords of post-penetrating keratoplasty (PKP) patients being managed with bitoric RGPCLs were compared to controls (post-PKP patients managed with spherical RGPCLs). Factors that were analyzed included the number of diagnostic RGPCLs used to assess the initial fit, the number of RGPCLs ordered to finalize the fit and the number of total doctor visits to finalize the fit.ResultsFourteen eyes of 14 patients satisfied the study criteria. The average amount of total astigmatism in this study group was 10.0 D ± 5.0 compared to the control group which was 3.3 D ± 2.6. The number of diagnostic RGPCLs used for the study group was 1.2 ± 0.4 compared to 1.0 ± 0.0 for the control group. The mean number of contact lenses ordered to complete the fitting for the study group was 1.9 ± 0.7 compared to the control which was 2.1 ± 0.8. The study group presented for an average of 6.3 ± 1.6 visits whereas the control group presented for 4.9 ± 1.1 visits. Contact lens corrected acuity for the study group was 0.101 ± 0.11 (20/25) compared to the control group 0.08 ± 0.12 (20/24).ConclusionsThe complexity of fitting bitoric RGPCLs was found to be similar to fitting spherical RGPCLs on post-PKP eyes and the visual outcomes were not different.     

Optical quality and intraocular scattering assessed with a double-pass system in eyes with contact lens induced corneal swelling

PurposeTo evaluate the impact of contact lens (CL)-induced corneal swelling on the optical quality of the eye by means of the double-pass technique.MethodsMeasurements of 6 healthy subjects were obtained in 5 visits over 1 week, at baseline and after sleeping with 4 different CLs of +0.50 D, +2.00 D, +5.00 D and +8.00 D (Acuvue2), randomly fitted on 4 different days. The control eye wore no CL. Corneal pachymetry and optical quality of the eye (OQAS, Visiometrics) were measured once at baseline and at three interval times in the follow-up visits: immediately after CL removal, and 1 and 2 h after CL removal. Optical quality was evaluated by means of the Strehl ratio and OQAS values at 100%, 20% and 9% contrasts. Intraocular scattering was evaluated with the objective scatter index (OSI).ResultsMean overnight swelling was 5.98 ± 4.29% in CL-eyes versus 0.30 ± 0.78% in control eyes (p < 0.01). Corneal swelling was maximal immediately after CL removal and decreased with time (p < 0.01). A significant worsening in all optical quality parameters and a significant increase of the OSI were found in eyes with corneal swelling (p < 0.05). Two hours after CL removal there were no statistically significant differences (p > 0.05) between CL-eyes and control eyes in any of the measured parameters.ConclusionsCorneal swelling has a significant impact on the optical quality of the eye and on intraocular scattering as assessed with the double-pass technique.     

The effect of tinted soft contact lens wear on functional visual acuity and higher-order aberrations

PurposeTo investigate the differences of functional visual acuity (FVA) and high order aberrations (HOAs) in relation to tinted and clear hydrogel soft contact lens (SCL) wear.MethodsA prospective comparative study was performed in 16 eyes of 16 healthy volunteers. Dynamic visual acuity (using a FVA measurement system) and higher-order aberrations (using a wavefront sensor) were compared in subjects wearing two types of soft contact lenses: 1-day Acuvue^® (Vistakon, Jacksonville, FL) clear and the 1-day Acuvue^® Define^TM (Vistakon, Jacksonville, FL) tinted lens. The blink rates were recorded during FVA testing. The correlation between the difference of HOAs and differences in FVA values was analyzed.ResultsThe mean LogMAR FVA scores with clear and tinted SCLs were 0.07 ± 0.13 and 0.14 ± 0.17 (P < 0.05). The mean blink frequencies with clear and tinted SCL wear were 18.4 ± 8.3 and 25.3 ± 4.7 blinks/min (P < 0.05). Both 3rd-order aberrations and total HOAs showed statistically significant differences between the two types of soft contact lenses for 6 mm pupil measurements (P < 0.05). A significant positive linear correlation was observed between ΔHOAs and ΔLogMAR FVA for 6 mm pupil measurements (R = 0.53, P = 0.04).ConclusionsTinted contact lens wear appears to induce a reduction in optical quality. Functional visual acuity measurement is a useful procedure to study the changes of visual performance and quality in tinted contact lens wear.