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.     

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.     

Corneal changes following short-term miniscleral contact lens wear

PurposeTo examine the influence of short-term miniscleral contact lens wear on corneal shape, thickness and anterior surface aberrations.MethodsScheimpflug imaging was captured before, immediately following and 3 h after a short period (3 h) of miniscleral contact lens wear for 10 young (mean 27 ± 5 years), healthy participants. Natural diurnal variations were considered by measuring baseline diurnal changes obtained on a separate control day without contact lens wear.ResultsSmall but significant anterior corneal flattening was observed immediately following lens removal (overall mean 0.02 ± 0.03 mm, p < 0.001) which returned to baseline levels 3 h after lens removal. During the 3 h recovery period significant corneal thinning (−13.4 ± 10.5 μm) and posterior surface flattening (0.03 ± 0.02 mm) were also observed (both p < 0.01). The magnitude of posterior corneal flattening during recovery correlated with the amount of corneal thinning (r = 0.69, p = 0.03). Central corneal clearance (maximum tear reservoir depth) was not associated with corneal swelling following lens removal (r = −0.24, p > 0.05). An increase in lower-order corneal astigmatism Z(2,2) was also observed following lens wear (mean −0.144 ± 0.075 μm, p = 0.02).ConclusionsFlattening of the anterior corneal surface was observed immediately following lens wear, while ‘rebound’ thinning and flattening of the posterior surface was evident following the recovery period. Modern miniscleral contact lenses that vault the cornea may slightly influence corneal shape and power but do not induce clinically significant corneal oedema during short-term wear.     

Long-term changes in straylight induced by corneal refractive therapy: A pilot study

PurposeTo assess long-term intraocular straylight changes induced by corneal refractive therapy (CRT) and to determine whether these changes persist after cessation of CRT lens wear.MethodsA single-center, prospective, longitudinal study was performed in 22 subjects (group 1) undergoing overnight corneal refractive therapy for 1 year. Ten right eyes of 10 subjects (group 2) with emmetropia served as controls. In each subject, high contrast visual acuity (HCVA), manifest refraction and intraocular straylight were determined at several time points during treatment and 1 month after discontinuing treatment. Straylight was measured using the van den Berg straylight meter (third generation). EDTRS charts (logMAR units) were used to assess HCVA. For both groups, only data for the right eyes were analyzed.ResultsStraylight (mean ± standard deviation) significantly fell from baseline (0.98 ± 0.13) to values recorded after 1 month (0.88 ± 0.13, p = 0.011), 3 months (0.88 ± 0.13, p = 0.004), 6 months (0.88 ± 0.13, p = 0.000) and 12 months (0.76 ± 0.12, p = 0.003) of treatment. One month after discontinuing CRT lens wear, straylight was still significantly lower than baseline (0.89 ± 0.13, p = 0.003). No correlations were observed between intraocular straylight and HCVA.ConclusionsGood refractive outcomes and reductions in straylight were observed in response to corneal refractive therapy for myopia. The reduction in straylight observed after discontinuing CRT warrents further investigation.     

Evaluation of central corneal thickness after cataract surgery,penetrating keratoplasty and long-term soft contact lens wear

PurposeThe aim of this study was to compare central corneal thickness (CCT) between corneas of normal healthy eyes (cNHE), corneas of eyes that had undergone cataract surgery by clear corneal phacoemulsification with implantation of an intracapsular intraocular lens (cIOL), corneal grafts after penetrating keratoplasty (gPK) and corneas of long-term soft contact lens wearers (cCL).MethodsThe study design was a consecutive cross-sectional trial. CCT was measured using rotating Scheimpflug camera (Pentacam, software version 1.16r04) in 80 cNHE, 79 cIOL, 46 gPK and 78 cCL. Analysis of variance (one-way ANOVA) was performed to compare differences of mean values between these four groups. Pearson's or Spearman's correlation coefficient (r) was determined between CCT value and age, follow up time after penetrating keratoplasty (timePK) or contact lens wearing time (timeCL).ResultsMeans of CCT measurements were comparable between cNHE (mean CCT ± standard deviation, 554 ± 36 μm), cIOL (551 ± 40 μm) and gPK (534 ± 52 μm) as determined by one-way ANOVA. Mean CCT values in cCL (537 ± 37 μm) were statistically significantly lower in comparison to cNHE (p = 0.026, 95% CI = 1.43–31.44). There was no linear correlation between age and CCT values of cNHE and cIOL (p = 0.841, r = −0.031 and p = 0.931, r = 0.011, respectively). No linear relationship was determined between CCT values of cCL and timeCL (p = 0.315, r = −0.125). CCT values of gPK did not correlate with timePK (p = 0.738, r = 0.054).ConclusionsThe data reported here indicate that in the same statistical model among CCT values of cNHE, cIOL and gPK only long-term soft contact lenses (CL) wearer have significantly lower CCT measurements.     

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.     

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.     

Corneal changes following short-term rigid contact lens wear

PurposeThe aim of this cross-over study was to investigate the changes in corneal thickness, anterior and posterior corneal topography, corneal refractive power and ocular wavefront aberrations, following the short term use of rigid contact lenses.MethodFourteen participants wore 4 different types of contact lenses (RGP lenses of 9.5 mm and 10.5 mm diameter, and for comparison a PMMA lens of 9.5 mm diameter and a soft silicone hydrogel lens) on 4 different days for a period of 8 h on each day. Measures were collected before and after contact lens wear and additionally on a baseline day.ResultsAnterior corneal curvature generally showed a flattening with both of the RGP lenses and a steepening with the PMMA lens. A significant negative correlation was found between the change in corneal swelling and central and peripheral posterior corneal curvature (all p ≤ 0.001). RGP contact lenses caused a significant decrease in corneal refractive power (hyperopic shift) of approximately 0.5 D. The PMMA contact lenses caused the greatest corneal swelling in both the central (27.92 ± 15.49 μm, p < 0.001) and peripheral (17.78 ± 12.11 μm, p = 0.001) corneal regions, a significant flattening of the posterior cornea and an increase in ocular aberrations (all p ≤ 0.05).ConclusionThe corneal swelling associated with RGP lenses was relatively minor, but there was slight central corneal flattening and a clinically significant hyperopic change in corneal refractive power after the first day of lens wear. The PMMA contact lenses resulted in significant corneal swelling and reduced optical performance of the cornea.     

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.     

Pain,wound healing and refractive comparison of mechanical and transepithelial debridement in photorefractive keratectomy for myopia: Results of 1 year follow-up

PurposeTo compare the efficacy, safety and postoperative pain of mechanical versus transepithelial photorefractive keratectomy (PRK) techniques.SettingCornea and refractive surgery subspecialty.DesignProspective clinical trial.MethodsThis prospective comparative study included 84 eyes of 42 patients with myopia who received mechanical PRK (m-PRK) in 1 eye and transepithelial PRK (t-PRK) in the contralateral eye. The mean patient age was 28.5 ± 6.3 years (range 20–46 years). Postoperative uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refractions, postoperative epithelial healing time, surgical time, postoperative pain rating and corneal haze were recorded.ResultsAt week 1, statistically the UDVA was significantly better in the t-PRK eyes; however, at 3 months, similar refractive stability was achieved in both groups. The mean spherical equivalent (SE) decreased from −2.44 ± 1.00 D (m-PRK eyes) and −2.88 ± 1.24 D (t-PRK eyes) at baseline to −0.19 ± 0.38 D and −0.30 ± 0.40 D, respectively, after 1 year. Surgical time was 98.6 ± 9.8 s in m-PRK eyes and 58.0 ± 6.4 s in t-PRK eyes. On postoperative days 1 and 3, using the global assessment rating, 81% of mPRK eyes that had pain, reported more pain than that reported for the tPRK eyes. In addition, m-PRK treated eyes demonstrated higher mean pain scores based on the 11-point numerical rating scale and Visual Analogue Scale (VAS). The mean time to complete epithelial healing was 2.19 ± 0.39 days (t-PRK) and 3.76 ± 0.43 days (m-PRK).Conclusiont-PRK for mild-to-moderate myopia was more comfortable than conventional m-PRK; patients had less pain, and faster healing time.     

The influence of soft contact lens wear and two weeks cessation of lens wear on corneal curvature

IntroductionAccurate corneal measurements are crucial in corneal refractive surgery (CRS) to ensure successful outcomes. Soft contact lens (SCL) wear may result in changes to corneal curvature and structure. United States Food and Drug Administration (FDA) pre-operative guidelines recommend that prior to CRS, SCL wearers cease SCL wear for “at least two weeks before examination and treatment” [1]. Corneal curvature changes induced by SCL wear may take longer than two weeks to resolve.PurposeTo examine the effect of SCL wear on corneal curvature before and following two weeks SCL wear cessation. To explore the possible impact of different SCL materials and years of SCL wear.MethodsRetrospective data analysis, between a group of SCL wearers (SCL: n = 45); and a non-contact lens control group (NCL: n = 45). Corneal curvature parameters were measured using the Pentacam (Oculus, Germany), before and following two weeks cessation of SCL wear.ResultsNo significant differences in keratometry or Sagittal radius of curvature between SCL and NCL groups prior to or following SCL cessation. Tangential radius of curvature showed significant inferior steepening for the SCL group prior to SCL cessation (SCL vs. NCL; 7.77 ± 0.30 mm vs. 7.90 ± 0.30 mm; p = 0.04). Following two weeks cessation of SCL wear this appeared to have resolved.ConclusionsTwo weeks cessation of SCL wear appears sufficient for resolution of corneal curvature changes with modern SCL materials and years of SCL wear. However, further studies with longer lens deprivation periods are required to ensure stability for all SCL wearing patients.     

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.     

Which soft contact lens power is better for piggyback fitting in keratoconus?

PurposeTo evaluate the impact of differente soft contact lens power in the anterior corneal curvature and regularity in subjects with keratoconus.MethodsNineteen subjects (30 eyes) with keratoconus were included in the study. Six corneal topographies were taken with Pentacam Eye System over the naked eye and successively with soft lens (Senofilcon A) powers of −3.00, −1.50, 0.00, +1.50 and +3.00 D. Corneal measurements of mean central keratometry (MCK), maximum tangential curvature (TK), maximum front elevation (MFE) and eccentricity (Ecc) at 6 and 8 mm diameters as well as anterior corneal surface high order aberrations (i.e. total RMS, spherical- and coma-like and secondary astigmatism) were evaluated.ResultsNegative- and plano-powered soft lenses flattened (p < 0.05 in all cases), whereas positive-powered lenses did not induce any significant changes (p > 0.05 in all cases) in MCK in comparison to the naked eye. The TK power decreased with negative lenses (p < 0.05 in both cases) and increased with +3.00 D lenses (p = 0.03) in comparison to the naked eye. No statistically significant differences were found in MFE with any soft lens power in comparison to the naked eye (p > 0.05 in all cases). Corneal eccentricity increased at 8 mm diameter for all lens powers (p < 0.05 in all cases). No statistically differences were found in HOA RMS and spherical-like aberration (both p > 0.05). Statistically differences were found in coma-like and secondary astigmatism (both p < 0.05).ConclusionNegative-powered soft contact lenses provide a flatter anterior surface in comparison to positive-powered lenses in subjects with keratoconus and thus they might be more suitable for piggyback contact lens fitting.     

Predicting success with silicone-hydrogel contact lenses in new wearers

Purposeto evaluate changes in tear metrics and ocular signs induced by six months of silicone-hydrogel contact lens wear and the difference in baseline characteristics between those who successfully continued in contact lens wear compared to those that did not.MethodsNon-invasive Keratograph, Tearscope and fluorescein tear break-up times (TBUTs), tear meniscus height, bulbar and limbal hyperaemia, lid-parallel conjunctival folds (LIPCOF), phenol red thread, fluorescein and lissamine-green staining, and lid wiper epitheliopathy were measured on 60 new contact lens wearers fitted with monthly silicone-hydrogels (average age 36 ± 14 years, 40 females). Symptoms were evaluated by the Ocular Surface Disease Index (OSDI). After six months full time contact lens wear the above metrics were re-measured on those patients still in contact lens wear (n = 33). The initial measurements were also compared between the group still wearing lenses after six months and those who had ceased lens wear (n = 27).ResultsThere were significant changes in tear meniscus height (p = 0.031), bulbar hyperaemia (p = 0.011), fluorescein TBUT (p = 0.027), corneal (p = 0.007) and conjunctival (p = 0.009) staining, LIPCOF (p = 0.011) and lid wiper epitheliopathy (p = 0.002) after six months of silicone-hydrogel wear. Successful wearers had a higher non-invasive (17.0 ± 8.2 s vs 12.0 ± 5.6 s; p = 0.001) and fluorescein (10.7 ± 6.4 s vs 7.5 ± 4.7 s; p = 0.001) TBUT than drop-outs, although OSDI (cut-off 4.2) was also a strong predictor of success.ConclusionSilicone-hydrogel lenses induced significant changes in the tear film and ocular surface as well as lid margin staining. Wettability of the ocular surface is the main factor affecting contact lens drop-out.     

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.     

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.     

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.     

Relationship between photon emission and chemopreventive potential of tea

Photon emission from tea (610–670 nm) in the H₂O₂/KHCO₃/MeCHO system and the utility of the photon detection system in tea evaluation were investigated. Photon intensity of tea depended on manufacturing method as follows: green tea (1202 ± SD 173.51 cd/m²) > oolong tea (834 ± SD 237.44 cd/m²) > black tea (222 ± SD 87.65 cd/m²). Photon intensity corresponded with polyphenol content (r²=0.8810) rather than catechin content (r²=0.7759) and showed a high correlation with chemopreventive activities against H₂O₂ (r²=0.7516), O₂⁻ (r²=0.7998) and DPPH radical (r²=0.7516). Photon intensity from green tea leaves at each manufacturing process step gave the same decreasing curve as DPPH radical scavenging activity. Chemiluminescence of tea, which gives information on the polyphenol content and chemopreventive potential, is a useful technique for tea evaluation.     

Trans epithelial corneal collagen crosslinking for progressive keratoconus: 6 months follow up

PurposeTo evaluate keratoconus biomechanical changes after transepithelial corneal collagen cross linking (TE CXL) using riboflavin and ultraviolet A (UVA).SettingSecond University of Naples, Naples, Italy.DesignProspective non comparative case series study.MethodsPatients with progressive keratoconus were examined, before and during a 6 months follow up after TE CXL, with a Pentacam, an Ocular Response Analyzer and an IOLMaster.Best corrected visual acuity (BCVA), refraction, corneal thinnest point (CTP), keratometry readings at the keratoconus apex (K_max), axial eye length (AL), corneal volume (CV) anterior chamber volume (ACV), anterior chamber depth (ACD), corneal hysteresis (CH) and corneal resistance factor (CRF) were evaluated.ResultsThirty-six eyes of 36 patients with progressive keratoconus were analyzed. Six months after treatment there was a significant improvement in BCVA (p < 0.01), no significant changes in refraction (p = 0.57), CTP (p = 0.07), K_max (p = 0.88), AL (p = 0.07), CV (p = 0.38), ACV (p = 0.07), ACD (p = 0.7), CH (p = 0.1) and CRF (p = 0.3).ConclusionsAccording to our results TE CXL stabilizes most of the patients with progressive keratoconus, without affecting in negative way the corneal elasticity.