Attitudes and understanding of premium intraocular lenses in cataract surgery: a public health sector patient survey

OBJECTIVES

To investigate patient understanding of, and attitudes to, premium (toric, extended depth of focus/multifocal) intraocular lenses (premIOLs) in public health sector patients undergoing cataract surgery (CS) in the UK.

METHODS

A 12 question survey with Likert scale questions was designed, to assess patient attitudes to post-operative spectacle dependence, refractive target and desirability of spectacle independence whilst considering possible complications of dysphotopsias and need for premIOL exchange/adjustment.

RESULTS

360 surveys were collected. CS had not been performed in 66.5%. Separate spectacles were worn for reading and distance in 28.8%, 19.2% had varifocals, 11.2% bifocals, 22.9% reading glasses only and 1.6% computer glasses only. Contact lenses were not worn in 95.7%. Only 41.6% were drivers. Most patients (85.8%) did not mind wearing glasses after CS, with 78.9% preferring reading glasses, compared with 29.7% preferring distance glasses. Most patients (75.3%) were not familiar with premIOLs, with 58.9% not willing to consider them in the context of a 2% risk of debilitating dysphotopsia and 54.2% rejecting a 5% risk of second surgery.

CONCLUSIONS

There is a lack of awareness of premIOLs in public health sector (NHS) patients in the UK, suggesting limitations in the "fully informed" consent process for CS. Most NHS CS patients are currently willing to wear spectacles after CS, especially reading glasses. There is reluctance in such patients to consider premIOLs on a background of small risks of debilitating dysphotopsias and increased risks of a second operation.

Time and Motion Studies to assess surgical productivity in cataract theatre lists within the National Health Service: Immediate Sequential Bilateral Cataract Surgery versus Delayed Sequential Bilateral Cataract Surgery

BACKGROUND

To compare productivity of National Health Service cataract lists performing unilateral cataract (UC) surgery vs Immediate Sequential Bilateral Cataract Surgery (ISBCS).

METHODS

Five 4-hour lists with ISBCS cases and five with UC were observed using time and motion studies (TMS). Individual tasks and timings of each staff member in theatre was recorded by two observers. All operations were performed by consultant surgeons under local anaesthesia (LA).

RESULTS

Median number of eyes operated per 4-hour list was 8 (range 6-8) in the ISBCS group and 5 (5-7) in the UC group (p = 0.028). Mean total theatre time (defined as time between the entry of the first patient and the exit of the last patient from theatre) was 177.12 (SD 73.62) minutes in the ISBCS group and 139.16 (SD 47.73) minutes in the UC group (p = 0.36). Mean time to complete two consecutive unilateral cataract surgery operations was 48.71 minutes compared to 42.23 minutes for a single ISBCS case (13.30% time saved). Based on our collected TMS data, a possible 5 consecutive ISBCS cases and 1 UC (total 11 cataract surgeries) could be performed during a four-hour theatre session, with a theatre utilisation quotient of 97.20%, contrasting to nine consecutive UC, with a theatre utilisation quotient of 90.40%.

DISCUSSION

Performing consecutive ISBCS cases under LA on routine cataract surgery lists can increase surgical efficiency. TMS are a useful way to investigate surgical productivity and test theoretical models for efficiency improvements.

A new software for automated counting of glistenings in intraocular lenses in vivo

AIM

To assess the performance of a bespoke software for automated counting of intraocular lens (IOL) glistenings in slit-lamp images.

METHODS

IOL glistenings from slit-lamp-derived digital images were counted manually and automatically by the bespoke software. The images of one randomly selected eye from each of 34 participants were used as a training set to determine the threshold setting that gave the best agreement between manual and automatic grading. A second set of 63 images, selected using randomised stratified sampling from 290 images, were used for software validation. The images were obtained using a previously described protocol. Software-derived automated glistenings counts were compared to manual counts produced by three ophthalmologists.

RESULTS

A threshold value of 140 was determined that minimised the total deviation in the number of glistenings for the 34 images in the training set. Using this threshold value, only slight agreement was found between automated software counts and manual expert counts for the validating set of 63 images (κ=0.104, 95%CI, 0.040-0.168). Ten images (15.9%) had glistenings counts that agreed between the software and manual counting. There were 49 images (77.8%) where the software overestimated the number of glistenings.

CONCLUSION

The low levels of agreement show between an initial release of software used to automatically count glistenings in in vivo slit-lamp images and manual counting indicates that this is a non-trivial application. Iterative improvement involving a dialogue between software developers and experienced ophthalmologists is required to optimise agreement. The results suggest that validation of software is necessary for studies involving semi-automatic evaluation of glistenings.

Corneal astigmatic outcomes after femtosecond laser-assisted cataract surgery combined with surface penetrating arcuate keratotomies

AIM

To evaluate corneal astigmatic outcomes of femtosecond laser-assisted arcuate keratotomies (FAKs) combined with femtosecond-laser assisted cataract surgery (FLACS) over 12mo follow-up.

METHODS

Totally 145 patients with bilateral cataracts and no ocular co-morbidities were recruited to a single-centre, single-masked, prospective randomized controlled trial (RCT) comparing two monofocal hydrophobic acrylic intraocular lenses. Eyes with corneal astigmatism (CA) of >0.8 dioptres (D) received unpaired, unopened, surface penetrating FAKs at the time of FLACS. Visual acuity, subjective refraction and Scheimpflug tomography were recorded at 1, 6, and 12mo. Alpins vectoral analyses were performed.

RESULTS

Fifty-one patients (61 eyes), mean age 68.2±9.6y [standard deviation (SD)], received FAKs. Sixty eyes were available for analysis, except at 12mo when 59 attended. There were no complications due to FAKs. Mean pre-operative CA was 1.13±0.20 D. There was a reduction of astigmatism at all post-operative visits (residual CA 1mo: 0.85±0.42 D, P=0.0001; 6mo: 0.86±0.35 D, P=0001; and 12mo: 0.90±0.39, P=0.0001). Alpins indices remained stable over 12mo. Overall, the cohort was under-corrected at all time points. At 12mo, 61% of eyes were within ±15 degrees of pre-operative astigmatic meridian.

CONCLUSION

Unpaired unopened penetrating FAKs combined with on-axis phacoemulsification are safe but minimally effective. CA is largely under-corrected in this cohort using an existing unmodified nomogram. The effect of arcuate keratotomies on CA remained stable over 12mo.

Laser-assisted cataract surgery versus standard ultrasound phacoemulsification cataract surgery

BACKGROUND

Cataract is the leading cause of blindness in the world and, as such, cataract surgery is one of the most commonly performed operations globally. Surgical techniques have changed dramatically over the past half century with associated improvements in outcomes and safety. Femtosecond lasers can be used to perform the key steps in cataract surgery, such as corneal incisions, lens capsulotomy and fragmentation. The potential advantage of femtosecond laser-assisted cataract surgery (FLACS) is greater precision and reproducibility of these steps compared to manual techniques. The disadvantages are the costs associated with FLACS technology.

OBJECTIVES

To compare the effectiveness and safety of FLACS with standard ultrasound phacoemulsification cataract surgery (PCS) by gathering evidence from randomised controlled trials (RCTs).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; which contains the Cochrane Eyes and Vision Trials Register; 2022, Issue 5); Ovid MEDLINE; Ovid Embase; LILACS; the ISRCTN registry; ClinicalTrials.gov; the WHO ICTRP and the US Food and Drug Administration (FDA) website. We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 10 May 2022.

SELECTION CRITERIA

We included RCTs where FLACS was compared to PCS.

DATA COLLECTION AND ANALYSIS

Three review authors independently screened the search results, assessed risk of bias and extracted data using the standard methodological procedures expected by Cochrane. The primary outcome for this review was intraoperative complications in the operated eye, namely anterior capsule, and posterior capsule tears. The secondary outcomes included corrected distance visual acuity (CDVA), quality of vision (as measured by any validated patient-reported outcome measure (PROM)), postoperative cystoid macular oedema complications, endothelial cell loss and cost-effectiveness. We assessed the certainty of the evidence using GRADE.

MAIN RESULTS

We included 42 RCTs conducted in Europe, North America, South America and Asia, which enrolled a total of 7298 eyes of 5831 adult participants. Overall, the studies were at unclear or high risk of bias. In 16 studies the authors reported financial links with the manufacturer of the laser platform evaluated in their studies. Thirteen of the studies were within-person (paired-eye) studies with one eye allocated to one procedure and the other eye allocated to the other procedure. These studies were reported ignoring the paired nature of the data. There was low-certainty evidence of little or no difference in the odds of developing anterior capsular tears when comparing FLACS and PCS (Peto odds ratio (OR) 0.83, 95% confidence interval (CI) 0.40 to 1.72; 5835 eyes, 27 studies) There was one fewer anterior capsule tear per 1000 operations in the FLACS group compared with the PCS group (95% CI 4 fewer to 3 more).  There was low-certainty evidence of lower odds of developing posterior capsular tears with FLACS compared to PCS (Peto OR 0.50, 95% CI 0.25 to 1.00; 5767 eyes, 26 studies). There were four fewer posterior capsule tears per 1000 operations in the FLACS group compared with the PCS group (95% CI 6 fewer to same).  There was moderate-certainty evidence of a very small advantage for the FLACS arm with regard to CDVA at six months or more follow-up, (mean difference (MD) -0.01 logMAR, 95% CI -0.02 to 0.00; 1323 eyes, 7 studies). This difference is equivalent to 1 logMAR letter between groups and is not thought to be clinically important. From the three studies (1205 participants) reporting a variety of PROMs (Cat-PROMS, EQ-5D, EQ-SD-3L, Catquest9-SF and patient survey) up to three months following surgery, there was moderate-certainty evidence of little or no difference in the various parameters between the two treatment arms. There was low-certainty evidence of little or no difference in the odds of developing cystoid macular oedema when comparing FLACS and PCS (Peto OR 0.84, 95% CI 0.56 to 1.28; 4441 eyes, 18 studies). There were three fewer cystoid macular oedema cases per 1000 operations in the FLACS group compared with the PCS group (95% CI 10 fewer to 6 more).  In one study the incremental cost-effectiveness ratio (ICER) (cost difference divided by quality-adjusted life year (QALY) difference) was GBP £167,620 when comparing FLACS to PCS. In another study, the ICER was EUR €10,703 saved per additional patient who had treatment success with PCS compared to FLACS. Duration ranged from three minutes in favour of FLACS to eight minutes in favour of PCS (I2 = 100%, 11 studies) (low-certainty evidence).  There was low-certainty evidence of little or no important difference in endothelial cell loss when comparing FLACS with PCS (MD 12 cells per mm2 in favour of FLACS, 95% CI -40 to 64; 1512 eyes, 10 studies).  AUTHORS' CONCLUSIONS: This review of 42 studies provides evidence that there is probably little or no difference between FLACS and PCS in terms of intraoperative and postoperative complications, postoperative visual acuity and quality of life. Evidence from two studies suggests that FLACS may be the less cost-effective option. Many of the included studies only investigated very specific outcome measures such as effective phacoemulsification time, endothelial cell count change or aqueous flare, rather than those directly related to patient outcomes. Standardised reporting of complications and visual and refractive outcomes for cataract surgery would facilitate future synthesis, and guidance on this has been recently published.

Comment on Fernández-Vigo et al. Objective Classification of Glistening in Implanted Intraocular Lenses Using Optical Coherence Tomography: Proposal for a New Classification and Grading System. J. Clin. Med. 2023, 12, 2351

We read with interest your article describing a new objective method for evaluating glistenings in intraocular lenses (IOLs) in vivo [...].

A multi-ethnic genome-wide association study implicates collagen matrix integrity and cell differentiation pathways in keratoconus

Keratoconus is characterised by reduced rigidity of the cornea with distortion and focal thinning that causes blurred vision, however, the pathogenetic mechanisms are unknown. It can lead to severe visual morbidity in children and young adults and is a common indication for corneal transplantation worldwide. Here we report the first large scale genome-wide association study of keratoconus including 4,669 cases and 116,547 controls. We have identified significant association with 36 genomic loci that, for the first time, implicate both dysregulation of corneal collagen matrix integrity and cell differentiation pathways as primary disease-causing mechanisms. The results also suggest pleiotropy, with some disease mechanisms shared with other corneal diseases, such as Fuchs endothelial corneal dystrophy. The common variants associated with keratoconus explain 12.5% of the genetic variance, which shows potential for the future development of a diagnostic test to detect susceptibility to disease.

Acceptability of immediate sequential bilateral cataract surgery (ISBCS) in a public health care setting before and after COVID-19: a prospective patient questionnaire survey

Objective

To ascertain patient acceptance of immediate sequential bilateral cataract surgery (ISBCS) in the National Health Service (NHS).

Methods

A survey was devised using a 5-point Likert scale for questions related to ISBCS, which patients undertook during their cataract outpatient appointment pre-COVID-19 lockdown and by telephone during the lockdown.

Results

Questionnaires were completed for 267 patients. Most respondents were aged over 71 (51%) and were female individuals (60%). Forty-five per cent agreed/strongly agreed with opting for ISBCS. A positive correlation was identified between opting for ISBCS and convenience to the patient (r=0.76, p<0.01) and family/carer/partner (r=0.71, p<0.01) and wanting to limit numbers of hospital visits (r=0.57, p<0.01). Fifty per cent agreed/strongly agreed that they were worried about the risk of simultaneous bilateral ocular complications, with this correlating with being less likely to opt for ISBCS (r=-0.49, p<0.01) and being scared of ISBCS (r=0.67, p<0.01). During COVID-19 lockdown, patients were less likely to want to minimise the time taken off work (p<0.05) and less intolerant of a prolonged hospital visit (p<0.05). Only 23% of respondents agreed/strongly agreed that they had familiarity with ISBCS.

Conclusions

ISBCS was acceptable to 45% of our sampled population, suggesting limited routine implementation in the NHS is possible. Convenience and reduction in hospital visits appeared to contribute to this acceptance. Half of the patients expressed concern regarding bilateral complications and such concerns need addressing. Some attitudes did appear to change during the COVID-19 lockdown period. The familiarity of the concept of ISBCS is low suggesting the need for patient education.

A randomised, prospective study of 'off-the-shelf' use of toric intraocular lenses for cataract patients with pre-existing corneal astigmatism in the NHS

BACKGROUND/OBJECTIVES

To compare visual and refractive outcomes of monofocal intraocular lenses (IOLs) with limbal relaxing incisions (LRI) with 'off-the-shelf' use of toric IOLs (TIOLs), with a fixed 2-dioptre cylinder (DC) correction, for cataract patients with pre-existing corneal astigmatism in a public-sector setting.

SUBJECTS/METHODS

Seventy-seven patients (77 eyes, first treated eye) with visually significant cataract and pre-operative corneal astigmatism ≥2.00 DC were randomised to receive either 'off-the-shelf' TIOLs, with a fixed 2.00 DC cylinder correction (39 eyes), or monofocal IOLs (38 eyes) with LRIs. The concept of fixing the cylindrical correction was to minimise costs, allow a full TIOL bank to be available and eliminate the need for individual TIOL ordering. Outcome measures were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA) and refraction. Astigmatic changes were evaluated using the Alpins vector method.

RESULTS

Mean UDVA improved from logMAR 0.88 (SD 0.56)[~20/150] pre-operatively to 0.18 (SD 0.19)[~20/30] post-operatively in TIOL group, versus 0.82 (SD 0.55)[~20/130] to 0.27 (SD 0.15)[~20/40] in monofocal/LRI group (P = 0.02; 95% CI: -0.17, -0.01). Mean CDVA improved from logMAR 0.40 (SD 0.26)[~20/50] to 0.01 (SD 0.12)[~20/20] in TIOL group, and 0.41 (SD 0.38)[~20/40] to 0.06 (SD 0.12)[~20/25] in LRI group (P = 0.07; 95% CI: -0.11, 0.01). Average post-operative refractive cylinder in TIOL group was 1.35 DC (SD 0.84 DC) and in LRI group 1.91 DC (SD 1.07 DC) (P = 0.01; 95% CI: -1, -0.12). Mean difference vector magnitude was 1.92 DC (SD 1.08 DC) in LRI group and 1.37 DC (SD 0.84 DC) in TIOL group (P = 0.02; 95% CI: 0.11, 0.99).

CONCLUSIONS

TIOLs with a fixed 2.00 DC correction during cataract surgery may improve UDVA, reduce post-operative cylinder and result in a more reliable astigmatic correction compared with monofocal IOLs with LRIs.

Corneal Surface Ablation Laser Refractive Surgery for the Correction of Myopia: A Network Meta-analysis

PURPOSE

To systematically compare the efficacy, predictability, safety, postoperative haze, pain scores, and epithelial healing time of four corneal surface ablation procedures.

METHODS

PubMed, Embase, Cochrane Library, and the U.S. trial registry were searched up to June 2018. Randomized controlled trials were selected. Efficacy (uncorrected distance visual acuity of 20/20 or better), predictability (refractive spherical equivalent within ±0.50 diopters [D] of the target), and safety (loss of two or more lines of spectacle corrected distance visual acuity) were set as primary outcome measures. Haze, pain scores, and epithelial healing time were set as secondary outcome measures.

RESULTS

Eighteen studies involving 1,423 eyes were included. According to the Grading of Recommendations Assessment, Development, and Evaluation, the quality of outcomes were moderate to high (70.6%). There were no differences in efficacy, predictability, safety, haze, day 1 pain, and epithelial healing time between treatments. Epithelial laser in situ keratomileusis (epi-LASIK) had statistically significantly higher pain scores on day 3 compared to photorefractive keratectomy (PRK) (weighted mean differences [WMD] = 2.2, 95% credible intervals [CrI] = 0.19 to 4.01) and transepithelial PRK (T-PRK) (WMD = 2.7, 95% CrI = 0.51 to 4.84). The surface under the cumulative ranking curve ranking results (best to worst) showed laser epithelial keratomileusis (LASEK) ranked highest for efficacy, predictability, safety, and day 1 pain scores. Epi-LASIK ranked best for grade 1 haze scores. T-PRK ranked best for haze of 0.5 or higher, haze scores day 3 pain scores, and epithelial healing time.

CONCLUSIONS

Surface laser refractive surgeries are comparable in terms of efficacy, predictability, safety, and postoperative haze except for day 3 pain scores, with epi-LASIK being more painful compared to PRK and T-PRK. [J Refract Surg. 2018;34(11):726-735.].

Regression and wound Healing after Excimer Laser Prk: A Histopathological Study on Human Corneas

BACKGROUND

The results of excimer laser PRK are promising as more than 80% of eyes with up to -6.0 diopters of attempted correction have refractive results within 1.0 diopter of emmetropia. However, throughout the dioptric range some unexpected results have been observed with individual patients showing an aggressive wound healing response with excessive myopic regression and severe corneal haze. Unfortunately, only limited data are available about the cellular and extracellular responses in human corneas after PRK and this information is important to establish adequate postoperative pharmaceutical treatment.

METHODS

We made a histopathological and immunohistochemical study on 20 human corneal samples from patients with severe corneal haze and myopic regression. The indirect immunofluorescence method was used for demonstration of collagen types I, III, IV laminin, chondroitin sulphate, dermatan sulphate, and keratin.

RESULTS

All corneal specimens showed a hyperplastic epithelium. Histologically, most samples (16/20) showed mainly a loose lamination of extracellular material which could be identified as collagen type IV. The remaining four samples had newly synthesised collagen type III.

CONCLUSIONS

Our histopathological results indicate that corneal wound healing after excimer laser PRK varies among individuals. In some people epithelial basement proteins, such as collagen type IV, are the main wound healing products, whereas in others mainly collagen type III is found postoperatively, which does not effect the synthesis of collagen type IV. This suggests the need for individually-tailored postoperative pharmaceutical treatment regimens.

A review of keratoconus: Diagnosis, pathophysiology, and genetics

We discuss new approaches to the early detection of keratoconus and recent investigations regarding the nature of its pathophysiology. We review the current evidence for its complex genetics and evaluate the presently identified genes/loci and potential candidate gene/loci. In addition, we highlight current research methodologies that may be used to further elucidate the pathogenesis of keratoconus.

Transepithelial Riboflavin Absorption in an Ex Vivo Rabbit Corneal Model

PURPOSE

To measure depth-specific riboflavin concentrations in corneal stroma using two-photon fluorescence microscopy and compare commercially available transepithelial corneal collagen cross-linking (CXL) protocols.

METHODS

Transepithelial CXL riboflavin preparations--MedioCross TE, Ribocross TE, Paracel plus VibeX Xtra, and iontophoresis with Ricrolin+--were applied to the corneal surface of fresh postmortem rabbit eyes in accordance with manufacturers' recommendations for clinical use. Riboflavin 0.1% (VibeX Rapid) was applied after corneal epithelial debridement as a positive control. After riboflavin application, eyes were snap frozen in liquid nitrogen. Corneal cross sections 35-μm thick were cut on a cryostat, mounted on a slide, and imaged by two-photon fluorescence microscopy. Mean (SD) concentrations were calculated from five globes tested for each protocol.

RESULTS

Peak riboflavin concentration of 0.09% (± 0.01) was observed within the most superficial stroma (stromal depth 0-10 μm) in positive controls (epithelium-off). At the same depth, peak stromal riboflavin concentrations for MedioCross TE, Ricrolin+, Paracel/Xtra, and Ribocross TE were 0.054% (± 0.01), 0.031% (0.003), 0.021% (± 0.001), and 0.015% (± 0.004), respectively. At a depth of 300 μm (within the demarcation zone commonly seen after corneal cross-linking), the stromal concentration in epithelium-off positive controls was 0.075% (± 0.006), while at the same depth MedioCross TE and Ricrolin+ achieved 0.018% (± 0.006) and 0.016% (0.002), respectively. None of the remaining transepithelial protocols achieved concentrations above 0.005% at this same 300-μm depth. Overall, MedioCross TE was the best-performing transepithelial formulation.

CONCLUSIONS

Corneal epithelium is a significant barrier to riboflavin absorption into the stroma. Existing commercial transepithelial CXL protocols achieve relatively low riboflavin concentrations in the anterior corneal stroma when compared to gold standard epithelium-off absorption. Reduced stromal riboflavin concentration may compromise the efficacy of riboflavin/ultraviolet corneal CXL.

Two-photon fluorescence microscopy of corneal riboflavin absorption

PURPOSE

To correct for attenuation in two-photon fluorescence (TPF) measurements of riboflavin absorption in porcine corneas.

METHODS

Two-photon fluorescence imaging of riboflavin was performed using excitation at a wavelength of 890 nm, with fluorescence signal detected between 525 and 650 nm. TPF signal attenuation was demonstrated by imaging from either side of a uniformly soaked corneoscleral button. To overcome this attenuation, a reservoir of dextran-free 0.1% wt/vol riboflavin 5'-monophosphate in saline and hydroxypropyl methylcellulose (HPMC) was placed on top of porcine corneas (globe intact-epithelium removed). TPF imaging was performed through this reservoir with image stacks acquired at 10-μm steps through the cornea repeated at regular intervals for up to 60 minutes. A novel correction method was applied to achieve corneal riboflavin concentration measurements in whole eyes (n = 4).

RESULTS

Significant attenuation of the TPF signal was observed in all eyes, with the signal decreasing approximately linearly with depth in uniformly soaked tissue. Cross-sectional TPF images taken of excised corneal strips confirmed the tissue was uniformly soaked so that the decrease in signal was not due to spatial variations in riboflavin concentration. After correcting for signal attenuation, we observed increased riboflavin concentrations with longer soak duration, with the mean (standard deviation) maximum tissue concentration recorded at 0.094% (± 0.001) wt/vol [1.36 mg/mL]. Uniform riboflavin absorption was achieved after a minimum 50 minutes. Following a standard corneal cross-linking soak of 30 minutes, a mean stromal concentration of 0.086% (± 0.001) wt/vol [1.25 mg/mL] was achieved at a depth of 300 μm.

CONCLUSIONS

The accuracy of TPF measurements of corneal riboflavin absorption can be increased by applying a correction for depth-related signal attenuation.

Transepithelial corneal collagen crosslinking: bilateral study

PURPOSE

To evaluate the efficacy of transepithelial collagen crosslinking (CXL) in patients with bilateral progressive keratoconus.

SETTING

Outpatient ophthalmic clinic.

DESIGN

Cohort study.

METHODS

Patients with a history of bilateral progressive keratoconus were recruited. The worst eye was treated with transepithelial CXL, while the fellow eye was left untreated as a control. Transepithelial CXL was performed by applying an enhanced riboflavin solution (riboflavin 0.1%, dextrane T500 with trometamol [Tris-hydroxymethyl aminomethane] and EDTA [ethylenediaminetetraacetic] sodium salt) on the intact corneal epithelium for 30 minutes before irradiation with ultraviolet A (370 nm at 3 mW/cm(2)) for 30 minutes. Follow-up was 18 months in all eyes.

RESULTS

The study enrolled 20 patients. Transient hyperemia and mild foreign-body sensation occurred in 8 eyes (40%) after treatment; both resolved after 24 hours. In treated eyes, there were statistically significant improvements in uncorrected and corrected visual acuity and topography-derived keratometry, cone apex power, and higher-order aberrations (P<.05). In untreated control eyes, there was a general trend toward worsening of these parameters. No complications were reported.

CONCLUSIONS

Transepithelial CXL treatment appeared to halt keratoconus progression, with a statistically significant improvement in visual and topographic parameters. The treatment was safe and well tolerated. Its noninvasive nature makes it potentially useful in cases in which epithelial debridement is ideally avoided, such as pediatric cases, uncooperative patients, and thin corneas with thicknesses nearing 380 μm.

Effects of ablation diameter on long-term refractive stability and corneal transparency after photorefractive keratectomy

OBJECTIVE

To evaluate the effects of ablation diameter on long-term refractive stability and corneal transparency after photorefractive keratectomy (PRK).

DESIGN

Long-term, prospective, follow-up study.

PARTICIPANTS

One hundred twenty-three eyes treated between 1990 and 1993 at one institution as part of a number of ethical committee-approved clinical studies underwent long-term follow-up at 10 to 12 years after PRK.

INTERVENTION

Photorefractive keratectomy was performed using the Summit Technology UV 200 and OmniMed Excimer lasers with either 4.0-mm (n = 36), 5.0-mm (n = 47), or 6.0-mm (n = 40) optical zones and either -3.0-diopters (D) or -6.0-D myopic spherical corrections, based on the original Munnerlyn algorithms.

MAIN OUTCOME MEASURES

Refractive stability, refractive predictability, best spectacle-corrected visual acuity, and corneal haze.

RESULTS

Refractive outcome at 1 and 10 to 12 years of follow-up was better with 6.0-mm treatments, especially for -6.0-D corrections (P>0.001). The early hyperopic shift was significantly reduced with 6.0-mm zones, with less regression between 1 and 6 months, compared with 5.0- and 4.00-mm PRK, especially for -6.0-D corrections (P<0.001). The postoperative refraction remained stable between 1 and 10 to 12 years in all groups. Objective measurements of haze were less with 6.0-mm compared with 4.0- and 5.0-mm treatments (P<0.001). Night vision problems were significantly less with 6.0-mm PRK (P<0.01). There was no evidence of progressive hyperopic shift, corneal ectasia, or late onset of corneal haze in any of the eyes during the follow-up period.

CONCLUSIONS

Refractive stability was maintained between 1 year and 10 to 12 years after PRK with 4.0-, 5.0-, and 6.0-mm optical zones. A significant linear trend was observed in terms of refractive predictability, early hyperopic shift, regression, corneal transparency, and night haloes with better outcomes in PRK with a larger ablation zone. None of the eyes had sight-threatening complications such as ectasia or late-onset corneal haze during the follow-up.

A long-term study of photorefractive keratectomy; 12-year follow-up

OBJECTIVE

To evaluate long-term refractive stability of excimer laser myopic photorefractive keratectomy (PRK).

DESIGN

A long-term (12 years) prospective follow-up study.

PARTICIPANTS

Sixty-eight patients (56.6%) of the original cohort of 120 who participated in the first United Kingdom excimer laser clinical trial underwent detailed clinical assessment at 12 years after myopic PRK.

INTERVENTION

Myopic PRK was performed using the Summit Technology UV 200 excimer laser with a 4-mm ablation zone. Patients were allocated to 1 of 6 treatment groups based on their preoperative refraction. Each group received one of the following spherical corrections: -2, -3, -4, -5, -6, or -7 diopters (D). Patients in each group received an identical treatment, and therefore, emmetropia was not the primary aim.

MAIN OUTCOME MEASURES

Refractive stability, refractive predictability, best spectacle-corrected visual acuity (BSCVA), and corneal haze.

RESULTS

The postoperative refraction remained stable at 12 years, with no significant change in mean spherical equivalent refraction between 1, 6, and 12 years. Seventy-five percent of patients who underwent a -2-D correction and 65% of patients who received a -3-D correction were within 1 D of intended correction at 12 years. Fifty-seven percent of the -4-D group and 50% of the -5-D group were within 1 D, and this was further reduced to 25% and 22% in the -6-D and -7-D groups, respectively. Four percent had residual corneal haze, and 12% had persistent nighttime halos at 12 years. Dry eyes were encountered in 3% of patients, and none of the eyes developed corneal ectasia in the long term.

CONCLUSIONS

In myopic PRK, refractive stability achieved at 1 year was maintained up to 12 years with no evidence of hyperopic shift, diurnal fluctuation, or late regression in the long term. Corneal haze decreased with time, with complete recovery of BSCVA. Night halos remained a significant problem in a subset of patients due to the small ablation zone size.

Fourier analysis of induced irregular astigmatism

PURPOSE

To analyze corneal topographic data by Fourier analysis to determine differences in irregular astigmatism following spherical hyperopic correction by photorefractive keratectomy (PRK) or laser in situ keratomileusis (LASIK).

SETTING

Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom.

METHODS

Thirty-six eyes of 18 patients with moderate hyperopia had LASIK in 1 eye and PRK in the other eye. The flap was cut on a nasal hinge with a Moria LSK One microkeratome. The laser was a Summit SVS Apex Plus with an optical zone of 6.5 mm and a blending zone of 1.5 mm. Corneal topographic data were acquired with a TMS-1 topographer (Computed Anatomy Inc.) preoperatively and 1, 3, 6, and 12 months postoperatively. The ASCII files containing the dioptric power values were extracted and analyzed with custom-written software to extract the Fourier harmonics.

RESULTS

The irregular astigmatism increased in both groups postoperatively, peaking at 3 months and then decreasing over the next 9 months. There was no statistically significant difference between the 2 groups at any time point (P<.05). The change in the topographically derived equivalent sphere showed undercorrection in both groups at all time points. Regular astigmatism showed a marginal statistically significant increase in the LASIK group at 12 months (P =.049).

CONCLUSION

Irregular astigmatism, equivalent sphere, and regular astigmatism were not significantly different in the PRK and LASIK groups during the follow-up. Based on the corneal topography, the 2 procedures induced an equal amount of irregular astigmatism.

[Sensitivity to glare before and after Nd:YAG capsulotomy. Comparison between small and large capsulotomy]

AIM OF THE STUDY

The aim of this study was to determine whether capsulotomy size influences visual performance.

PATIENTS AND METHODS

Twenty eyes were included in this study and were divided into two groups: 10 eyes had small central capsulotomies without dilating the pupil, and 10 eyes had large capsulotomies through dilated pupils. We measured both, visual acuity and glare due to forward light scatter using a computer system.

RESULTS

Following treatment both groups had equally significant (< 0.001) improvements in visual acuity. However, a significant (p < 0.001) improvement of glare due to forward light scatter was only observed in the eyes with a large size capsulotomy.

CONCLUSIONS

Our study showed that measurements of forward light scatter are more sensitive than visual acuity testing in demonstrating loss of visual performance in patients with media opacities. It is recommended that pupils are dilated prior to Nd:YAG capsulotomy if forward light scatter from capsule remnants and the subsequent glare disability are to be minimised.

Excimer laser superficial keratectomy for proud nebulae in keratoconus

Contact lens intolerance in keratoconus may be due to the formation of a proud nebula at or near the apex of the cone. Excimer laser superficial keratectomy was performed as an outpatients with proud nebulae as treatment patients with proud nebulae as treatment for their contact lens intolerance. The mean period of contact lens wear before the development of intolerance was 13.4 years (range 2 to 27 years). Following the development of intolerance, three patients abandoned contact lens wear in the affected eye while the remainder experienced a reduction in comfortable wearing time (mean = 3.75 hours; range: 0-14 hours). All patients had good potential Snellen visual acuity with a contact lens of 6/9 (nine eyes) and 6/12 (one eye). The proud nebulae were directly ablated with a 193 nm ArF excimer laser using a 1 mm diameter beam. Between 100-150 pulses were sufficient to ablate the raised area. Patients experienced no pain during the procedure and reported minimal discomfort postoperatively. In all cases flattening of the proud nebulae was achieved. Seven patients were able to resume regular contact lens wear (mean wearing time = 10.17 hours; range 8 to 16 hours). In three patients, resumption of contact lens wear was unsuccessful because of cone steepness. All patients achieved postoperative Snellen visual acuity of 6/12 or better with a contact lens. Four patients experienced a loss of one line in Snellen acuity. The mean follow up period was 8.3 months (range 2 to 17 months). Excimer laser superficial keratectomy is a useful technique for the treatment of contact lens intolerance caused by proud nebulae in patients with keratoconus. Penetrating keratoplasty is thus avoided.

Corneal light scattering and visual performance in myopic individuals with spectacles, contact lenses, or excimer laser photorefractive keratectomy

Corneal transparency and visual performance are currently receiving much attention after excimer laser surgery. To date, emphasis has been on comparison of eyes on which laser surgery has been performed to eyes with emmetropia. A more appropriate comparison should be between eyes on which laser surgery has been performed and eyes with other forms of correction for myopia. Forward-scattered light, back-scattered light, and visual acuity were investigated and data were collected from 35 myopic individuals with various types of correction for myopia (spectacles, hard and soft contact lenses, and excimer laser surgery). Forward-scattered light was measured by using a new computerized technique, back-scattered light was measured with a charge coupled device-camera system, and visual acuity was measured with a computerized system at various levels of contrast. Spectacles, hard contact lenses, and excimer laser surgery are all superior to soft contact lenses in terms of light scatter and low-contrast visual acuity and excimer laser photorefractive keratectomy produces comparable results to spectacles one year postoperatively. At low-contrast visual acuity, mean visual acuity was 2.45 minutes of arc for the spectacle wearers, 3.21 minutes of arc for the hard contact-lens wearers, and 5.04 minutes of arc for the soft contact-lens wearers. Excimer laser patients had a mean visual acuity of 9.04 minutes of arc three months postoperatively, and 2.53 minutes of arc after one year. A mean value of 2.4% contrast for forward light scatter was obtained for spectacle wearers compared with a level of 3.84% contrast for hard contact-lens wearers and 16.1% contrast for soft contact-lens wearers. The mean value for excimer laser patients was 20% contrast three months postoperatively and 2.1% contrast one year postoperatively.

Halos--a problem for all myopes? A comparison between spectacles, contact lenses, and photorefractive keratectomy

After photorefractive keratectomy (PRK) using excimer lasers (193 nm) many patients report the presence of halos around light sources at night. However, halos are not unique to PRK patients, as they are a common observation in myopic contact lens wearers. We present an objective measurement of the halos using a computerized technique. The patient fixated on a red cross within a white circle in the center of a video monitor which served as the halo source. The screen surrounding the circle was not illuminated. The operator controlled the movement of the white spot and moved the spot toward the halo source until the subject indicated when the cursor was at the outer parameter of the halo. Measurements were made at 30 degree intervals around the halo source and expressed as square degrees. The study found that spectacles, soft contact lenses, and excimer laser surgery were superior to hard contact lenses in terms of the size of the halo. A mean value of 2.51 square degrees was obtained for spectacles wearers compared with 3.18 square degrees for soft contact lenses, 3.14 square degrees for excimer laser patients with 4-millimeter ablation zone, 2.76 square degrees for excimer laser patients with a 5-millimeter ablation zone, and 89.5 square degrees for hard contact lenses. It appears that this device is very useful for measuring the halo size after excimer laser PRK. We concluded that halos were not a problem for our patients after excimer laser photorefractive keratectomy.