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.     

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.     

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.     

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.     

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.     

The relationship between measurement method and corneal structure on apparent intraocular pressure in glaucoma and ocular hypertension

PurposeTo analyse the relationship between measured intraocular pressure (IOP) and central corneal thickness (CCT), corneal hysteresis (CH) and corneal resistance factor (CRF) in ocular hypertension (OHT), primary open-angle (POAG) and normal tension glaucoma (NTG) eyes using multiple tonometry devices.MethodsRight eyes of patients diagnosed with OHT (n = 47), normal tension glaucoma (n = 17) and POAG (n = 50) were assessed. IOP was measured in random order with four devices: Goldmann applanation tonometry (GAT); Pascal^® dynamic contour tonometer (DCT); Reichert^® ocular response analyser (ORA); and Tono-Pen^® XL. CCT was then measured using a hand-held ultrasonic pachymeter. CH and CRF were derived from the air pressure to corneal reflectance relationship of the ORA data.ResultsCompared to the GAT, the Tonopen and ORA Goldmann equivalent (IOPg) and corneal compensated (IOPcc) measured higher IOP readings (F = 19.351, p < 0.001), particularly in NTG (F = 12.604, p < 0.001). DCT was closest to Goldmann IOP and had the lowest variance. CCT was significantly different (F = 8.305, p < 0.001) between the 3 conditions as was CH (F = 6.854, p = 0.002) and CRF (F = 19.653, p < 0.001). IOPcc measures were not affected by CCT. The DCT was generally not affected by corneal biomechanical factors.ConclusionThis study suggests that as the true pressure of the eye cannot be determined non-invasively, measurements from any tonometer should be interpreted with care, particularly when alterations in the corneal tissue are suspected.     

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.     

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.     

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.     

Comparison of subjective grading and objective assessment in meibography

AimTo analyse repeatability of subjective grading and objective assessment in non-contact infra-red meibography.MethodsMeibography photographs of 24 subjects (female 14; mean age = 46; range = 19–69 years, upper-lid images = 12, lower-lid images = 12) were classified in two sessions by three experienced observers (OI, OII, OIII). Relative area or portion affected by meibomian glands (MG) loss was classified applying three different grading scales in randomized order: a four-grade scale (4S) (degree 0 = no partial glands; 1 = <25% partial glands; 3 = 25–75% partial glands; 3 = >75% partial glands), a pictorial five-grade scale (5S) (degree 0 = no meibomian gland loss (MGL); 1 = <25% MGL; 3 = 26–50% MGL; 3 = 51–75%; 4 = >75% MGL) and objectively by a 100-grade scale (DA) applying ImageJ software.ResultsObserved MG loss ranged from 0% to 69%. Intra-observer agreement of the 5S (OI: κ = 0.80, p < 0.001; OII: κ = 0.40, p = 0.009; OIII κ = 0.81, p < 0.001) was better than of the 4S (OI: κ = 0.79, p < 0.001; OII: κ = 0.15, p = 0.342; OIII κ = 0.50, p = 0.0071). Intra-observer agreement of OI and OIII (±0.88 (95% confidence interval), ±1.305) was better than of OII (±2.21) in 4S and 5S (±0.99, ±2.00 and ±0.91; OI, OII and OIII, respectively) while it was relatively similar in DA (±18, ±17 and ±17). Inter-observer agreement was better in DA (OI–OII: ±13, OI–OII: ±19, OII–OIII: ±26) than in 4S (OI–OII: ±1.76; OI–OIII: ±1.29 and OII–OIII: ±1.31) or 5S (OI–OII: ±1.49; OI–OIII: ±0.91 and OII–OIII: ±1.20).ConclusionIntra-observer and inter-observer agreement was better in computerized grading followed by the subjective five-grade scale and four-grade scale.     

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.     

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.     

Conjunctival UV autofluorescence – Prevalence and risk factors

PurposeAutofluorescence of ultraviolet (UV) light has been shown to occur in localised areas of the bulbar conjunctiva, which map to active cellular changes due to UV and environmental exposure. This study examined the presence of conjunctival UV autofluorescence in eye care practitioners (ECPs) across Europe and the Middle East and its associated risk factors.MethodImages were captured of 307 ECPs right eyes in the Czech Republic, Germany, Greece, Kuwait, Netherlands, Sweden, Switzerland, United Arab Emirates and the United Kingdom using a Nikon D100 camera and dual flash units through UV filters. UV autofluorescence was outlined using ImageJ software and the nasal and temporal area quantified. Subjects were required to complete a questionnaire on their demographics and lifestyle including general exposure to UV and refractive correction.ResultsAverage age of the subjects was 38.5 ± 12.2 years (range 19–68) and 39.7% were male. Sixty-two percent of eyes had some conjunctival damage as indicated by UV autofluorescence. The average area of damage was higher (p = 0.005) nasally (2.95 ± 4.52 mm²) than temporally (2.19 ± 4.17 mm²). The area of UV damage was not related to age (r = 0.03, p = 0.674), gender (p = 0.194), self-reported sun exposure lifestyle (p > 0.05), geographical location (p = 0174), sunglasses use (p > 0.05) or UV-blocking contact lens use (p > 0.05), although it was higher in those wearing contact lenses with minimal UV-blocking and no spectacles (p = 0.015). The area of UV damage was also less nasally in those who wore contact lenses and spectacles compared to those with no refractive correction use (p = 0.011 nasal; p = 0.958 temporal).ConclusionUV conjunctival damage is common even in Europe, Kuwait and UAE, and among ECPs. The area of damage appears to be linked with the use of refractive correction, with greater damage nasally than temporally which may be explained by the peripheral light focusing effect.     

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.     

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.     

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.     

Changes in tear film,corneal topography,and refractive status in premenopausal women during menstrual cycle

PurposeTo investigate the changes in a questionnaire based subjective symptomatology, tear film break-up time, tear volume, corneal topography, and refractive status in premenopausal women during menstrual cycle.MethodsSeventeen premenopausal females and 15 healthy males were enrolled in this prospective study. After routine ophthalmologic examination, an ocular surface disease index questionnaire was administered, tear film break-up time (TBUT), and Schirmer I tests were performed. Keratometry readings and refractive status were also obtained. All examinations were repeated at day 21, day 12 and day 2.ResultsOSDI score in day 21 was significantly lower than that in day 12 (p = 0.004) and day 2 (p = 0.01) in the female patients; however, no significant change was found in the male subjects (p > 0.05). No statistically significant difference was found in TBUT and Schirmer I tests, keratometry, and refraction results in both of the female and male subjects at all of the test points (p > 0.05). There was a significant correlation between OSDI score and TBUT (p = 0.02, p = 0.03, respectively), and Schirmer I test at day 12 (p = 0.004, p = 0.008, respectively). A significant negative correlation was found between oestrogen level and horizontal keratometry values at day 21 (r = −0.5, p = 0.03; r = −0.4, p = 0.04, respectively) for the right and left eyes in the female subjects.ConclusionOur study confirms that fluctuations in the blood levels of oestrogen produce alterations in ocular surface equilibrium during the menstrual cycle and consequently affect the subjective dry eye symptoms in female patients. However, no ocular surface parameter changes were observed.     

Corneal biomechanical properties: Precision and influence on tonometry

PurposeTo assess the precision and reproducibility of the corneal biomechanical parameters, and their relationships with the intraocular pressure (IOP) measured with the Goldmann tonometer and a noncontact tonometer.MethodsReadings for biomechanical properties and for IOP measured with the Goldmann and noncontact tonometers, were taken on one randomly selected eye of 106 normal subjects, on each one of two measurement sessions. Measurements with the ocular response analyzer (ORA) and the noncontact tonometer were randomized, followed by the measurement of central corneal thickness and with the Goldmann tonometer.ResultsRepeatability coefficients for CCT, corneal hysteresis (CH) and corneal resistance factor (CRF) in Session 1 were ±0.01 μm, ±3.05 mmHg and ±2.62 mmHg, respectively. The mean CCT, CH, CRF, Goldmann and noncontact tonometry did not vary significantly between sessions. Reproducibility coefficients for CCT, CH and CRF were ±0.02 μm, ±2.19 mmHg and ±1.97 mmHg, respectively. Univariate regression analysis showed that CCT, CH and CRF significantly (P < 0.0001) correlated with the IOP measured with the Goldmann and noncontact tonometers (and with the differences between tonometers) in Session 1. There were no significant correlations with the differences between tonometers in Session 2. Multivariate analysis revealed a minimal effect of CCT on Goldmann measurements but a significant effect on those of the noncontact tonometer.ConclusionsMeasurement of the biomechanical properties of the cornea, using the ORA, are repeatable and reproducible, affect Goldmann tonometry less than noncontact tonometry, and have a minimal influence on the difference in measured intraocular pressure between tonometers.     

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.