Keratoconus & Post-refractive Surgery Ectasia
Post-operative corneal ectasia is a potentially serious complication of laser in situ keratomileusis (LASIK). Current
pre-operative screening methods to identify “at risk” individuals are far from flawless.
Data from 36 eyes exhibiting LASIK-induced keratoconus were collected and entered into the Randleman Ectasia Risk
Factor Score System. Twenty-five percent would have been identified as having “low risk” for ectasia and approximately half would have been pre-operatively flagged as “high risk” eyes.
The authors agree that abnormal corneal topography appears to be the most important pre-operative risk factor (followed by residual stromal bed and pre-operative corneal thickness), but found that the average manifest refraction spherical equivalent (and thus the amount of tissue removed) did not correlate with increased risk.
An abnormal topography as a risk factor was found in 69% of cases in this study. Although previous findings indicated a sensitivity and specificity of 91% and 96% respectively, the current study indicated a sensitivity of 56%, with the specificity not analyzed due to statistical methodological concerns. The authors state that the Randleman score system, although valuable, can overlook a significant number of patients at risk for ectasia. It has been hypothesized that inducing collagen crosslinking (CXL) in the keratoconic stroma will increase the biomechanical stability of the cornea and potentially be a viable treatment for progressive keratoconus. However, measuring
these changes in vivo has proved challenging. Researchers from the Department of Biomedical Engineering
at The Ohio State University used a non-invasive immersion ultrasound technique in an attempt to address this
issue. Twenty-eight postmortem porcine eyes were examined before and after treatment with riboflavin and UVA
radiation to induce CXL. Corneal thickness, density and stiffness were measured. Researchers found that the corneal aggregate modulus increased, which is qualitatively consistent with previous ex vivo findings of increased stiffness, showing promise for the immersion ultrasound method in vivo.Vinciguerra P, Carnesasca FI, Albe E, et al. Corneal Collagen Cross-linking for Ectasia after Excimer Laser Refractive Surgery: 1-year Results. J Ref Surg 26(4):
486–497, 2010. The Corneal Collagen Cross-linking (CXL) treatment of ectasias after excimer laser refractive surgery is studied to determine its effect out to 1 year. This study focuses on the utilization of CXL post-excimer laser refractive ectasia as a possible treatment modality. Thirteen eyes from 9 patients were enrolled in the
Cornea Service of the Ophthalmology Department of Instituto Clinico Humanitas in 2007–2008. All eyes had to
have at least 350 μm of corneal thickness, exhibit a change of at least 3D in the past 6 months, and also show a change of K’s of 1.50D in the past 6 months. All patients underwent the CXL procedure and were examined daily until reepithelialization was observed. The subjects were followed at 1, 3, 6, and 12 months post-CXL Follow-up visits consisted of unaided acuities, BCVA and topography/corneal thickness assessments, aberrometric measurements, and endothelial cell counts.At 6 months, visual acuity improvement (BSCVA) was statistically significant (20/35 pre-op and 20/25 post-op). There was no significant change at any follow-up visits for
unaided acuities.Topography results also remained stable from 6–12months. Aberrometry measurements showed mean corneal coma, spherical aberration, and high order astigmatism to decrease by the 1-year mark (although not statistically significant). A statistical decrease of corneal thickness at the 0mm and 2mm topographic markers was found at 3 months (and remained stable until 12 months), which is consistent with typical CXL cases. Also consistent with CXL treatment, the endothelial cell count was reduced (pre-op 2555 +/– 470 cells/mm2, post-op 2120 +/– 517
cells/mm2). This finding was not statistically significant. All mentioned findings remained stable from 6–12 months.
Overall the study suggests that aside from gas permeable lenses or a full penetrating keratoplasty, CXL may be
an alternate treatment for post-excimer laser refractive surgery ectasia.
This comprehensive review details the effect of blueblocking
intraocular lenses (IOLs) on clinical measures, such as visual acuity, contrast sensitivity, color perception
and sleep disturbance, by analyzing 56 peer-reviewed
papers relating to these topics published over the last 47
years. Of independent studies that compared visual performance
between blue-blocking and UV-only-blocking IOLs, 91% concluded that there are no significant differences between the two. Multiple studies have shown a decrease in scotopic sensitivity, although the clinical significance of this decrease has been debated. Contrast sensitivity is greater in blue-blocking lenses, especially in the lower to middle frequency; the paper gives two possible reasons for this increase. The IOLs do not appear to significantly alter color vision performance among subjects.The authors also indicate that blue-blocking IOLs do not interfere with tests that rely on blue light (such as nerve fiber layer photography), or affect an individual’s sleep pattern in a clinically significant way. Although they admit the direct benefits of blue-blocking IOLs on agerelated macular degeneration remain uncertain, the authors support their use based on the potential protective benefits to the retina and lack of significant negative effects.
Dry Eye Disease
This continuing education article discusses topical
treatment options for managing aqueous-deficient dry eye.
The author recommends that tear replacement formulations
have a pH value of 7.4 to reduce discomfort and irritation
upon instillation. An isotonic sodium chloride concentration
of 0.9% is suggested to help maintain normal corneal
thickness (or in the case of severe tear-deficient dry eye, a
hypotonic solution is advisable to assist corneal absorption
and increase delivery of essential nutrients to the stroma).
Three general categories of tear replacement are discussed, which include aqueous artificial tears, ocular lubricants
and viscoelastics. Each category is broken down based on its viscosity, with the viscosity of various agents discussed in great detail, ranging from low viscosity aqueous artificial tears, which provide short-term relief with little to no visual disturbance, to high viscosity ocular lubricants/ointments, which provide increased retention, but often at the expense of blurred vision. Lastly, the author writes about viscoelastic gel polymers which demonstrate a unique property in that they exhibit high viscosity when stationary (in between blinks and at rest); this leads to increased retention and reduced frequency of application, but they become much more fluid during active blinking, facilitating the spreading of tears and the formation of a more stable tear film overall. Dry eye disease (DED) affects nearly 5 million people in the U.S. over the age of 50. Although risk factors have been categorized and targeted, there still is a lack of proper management of these chronic sufferers. Often there is a disconnect between the quality of life (QoL) a patient reports when compared to signs and symptoms. When directly asked, patients often will report a noticeable
impact on activities of daily living (ADL), but won’t offer this information unless prompted. The QoL of a mild
to severe sufferer has been compared to the QoL level of Class III/IV angina sufferers or mild psoriasis patients.
In further aiding patients’ needs, some sort of QoL measurement should always be used as a diagnostic tool.
There are currently two validated DED-specific measures used: the Impact of Dry Eye on Everyday Life (IDEEL)
which is a 57-item questionnaire, and the Ocular Surface Disease Index (OSDI), a 12 question survey. There is also
a vision specific survey (not disease specific) known as the National Eye Institute Visual Functioning Questionnaire
(NEI-VFQ), which is a 25-item questionnaire. The NEI-VFQ has been found to be moderately to strongly
correlated to the OSDI. Four general modes of DED treatment are outlined by the authors and include; tear supplementation, tear retention strategies, tear stimulants and anti-inflammatory agents. Treatments for DED have been well documented, but few of these treatments have gone head to head in comparison or have elicited the use of a QoL tool. In order to better assess what is best for the patient and what treatments are effective, these tools should be considered critical for each step of the treatment process for DED. Studies have shown that topical azithromycin is potentially effective in the treatment of meibomian gland dysfunction (MGD) and lid margin diseases. The goal of this study was to evaluate the clinical signs and symptoms of MGD with azithromycin usage, and to spectroscopically analyze alteration in lipid secretion from the meibomian glands before and after azithromycin therapy. Subjects were symptomatic MGD sufferers who had unresponsive results from lid massage/hot compresses
and were not allowed to be using any systemic/topical antibiotics or anti-inflammatory medications. The severity
was quantified by symptoms (via questionnaire) and signs (via biomicroscopic exam).Twenty-two subjects were asked to use 1% topical azithromycin ophthalmic solution for 1 month: 1 drop twice daily for 2 days, then once daily for the duration of the month. Lid expression and collection was performed with cotton tipped applicators before treatment, at 2 weeks, 4weeks, and 1 month after discontinuing therapy. Roughly 1mg of meibum lipid was collected per subject and was analyzed using Fourier transform infrared spectroscopy. All symptoms (via questionnaire) and signs (via biomicroscopic exam) improved at the end of the 4-week trial. Spectrograph analysis also showed improved quality of meibum lipid to a more “normal” status. The study verifies that topically applied azithromycin may improve and control management of MGD and other lid diseases.
Contact Lens Effects and Cost
Eleven males and nine females participated in a study
that looked at the corneal epithelium features between 10
soft contact lens wearers (CL) and 10 non-contact lens
wearers via scanning electron microscopy. All subjects underwent standard photorefractive keratectomy (PRK) at the Eye Department of the University of Federico II of Naples, and lens wearers had discontinued wear for at least 2 weeks. One corneal epithelial sample was obtained from each eye prior to surgery and was subsequently analyzed. Researchers found no difference between the two groups
in terms of the number of microvilli; however, the mean percentage of epithelial mucous was substantially decreased
in the CL group (10.9% vs. 40.4%). Interestingly, even with this decrease in surface mucous, the CL group had no CLrelated complaints prior to PRK, and rated their lens comfort level as 4 +/– 0.47 (out of 5). The authors concluded that surface mucin reduction does not seem to relate to CL intolerance; however, they hypothesized that the reduced
amount of epithelial mucous in soft CL wearers could be a predisposing factor for microbial keratitis. This article examined a breakdown of cost-per-wear of soft lenses to help determine the most suitable and costeffective
modality. The study took place in Australia and incorporated three wearing modalities: daily wear, 2-
week disposable and monthly wear. It went on further to break down the cost analysis for spherical, toric, and
multifocal lenses. The model used takes into account the annual cost (professional fees, contact lenses and solution
per year) divided by the number of times a lens is worn per year. The breakdown of spherical lenses was as follows: the cost-per-wear modality of 2-week lenses versus monthly was nearly identical (a slight decrease noted with increasing wear). The cost-per-wear was lower for daily lenses versus 2-week or monthly lenses when worn 1–4 times/week. The break-even point was 5 days. When lenses were worn 6–7 times/week, the 2-week/1-month modalities of lenses had a lower cost-per-wear ratio.Toric lenses showed a similar pattern (although upwardly
displaced due to higher cost of toric lenses), with a break-even point between 3–4 days between dailies and 2-
week/1-month modality. Mulitifocals tended to vary slightly (and overall cost was increased) with the break-even point of dailies versus 2-week lenses at 3–4 days and dailies versus 1 month at 4–5 days.These values were based on similarity of lens material, and compliant use of lenses and solution. Other factors definitely may play a role in lens selection, such as material, solution compatibilities, and available lens parameters.
This investigation was a matched case-control study that
evaluated 17,556 cases in the United Kingdom to examine
whether oral hypertensive or cholesterol-lowering medications
(statins) affected the risk of developing glaucoma. The
investigators used an anonymized database to mine for data
related to those systemic medications and the risk of glaucoma.
A statistical analysis indicated that glaucoma patients
were 20% less likely to have been treated with oral β1-selective medications than the control group. Authors allude
to the potential of increased glaucoma cases as the prescribing trends for managing systemic hypertension are drifting away from the use of β-blockers. Unexpectedly, patients taking the diuretic thiazide showed a higher prevalence of glaucoma than the control group, and study results indicate that statins had no protective effect on
the risk for glaucoma development, which is contrary to recent speculation. The authors do state that prior studies
have shown a higher risk of glaucoma in patients using diuretic medications. Previous studies have shown that community practices regarding treatment of infectious keratitis do not necessarily follow traditional therapeutic recommendations. This study sought to assess the opinions of current practicing corneal specialists and general ophthalmologists regarding corneal ulcer management. Six-hundred twenty-nine questionnaires from ophthalmologists in California, Florida, Illinois and Missouri were evaluated.The majority of responders (88.8% of general OMDs and 76% of cornea OMDs) tend to initiate antibiotic treatment with newer commercially-available fluoroquinolones; however, the percentage of ophthalmologists using fortified antibiotics was higher within the cornea specialist group. Most had access to cultures (Gram stain), yet 58% (27%) of comprehensive ophthalmologists and 25% (6%) of cornea specialists declined to use these means of identification on initial presentation. The majority of all OMDs surveyed, were apt to forgo Gram staining and culturing in favor of empiric monotherapy with 4th generation fluoroquinolones.The authors were very careful to note that these management trends cannot be generalized to the ophthalmic community as a whole, due to the small sample size of the study, nor are they recommending a preferred therapeutic approach. This is a retrospective study performed at the Department
of Ophthalmology of North Shore-Long Island Jewish Health System to review the efficacy of 0.01% preservative-
free dexamethasone in 0.9% sodium chloride solution in the treatment of chronic ocular surface disease (COSD). COSD patients have multifactorial signs/symptoms of dry eye that often include refractory fluctuation and poor response to other treatments, particularly with preservatives. The preservative in many cases exacerbates
the COSD. Thirty-one patients (62 eyes), aged from 22–90 years, received 1 drop of the solution 3–4 times per day and tapered over 1 month to a maintenance dose of 1 drop every 2–3 days. Patients were told to enter a wash out period 1 month prior to beginning the treatment (i.e., no other topical dry eye treatments allowed). The results were based on subjective response, with significant/complete resolution of symptoms (50–100% improvement), mild resolution (25–50% improvement), or no improvement. Follow-up ranged from 4–60 weeks, with a mean of 11.5 weeks. The results showed 20 of the 31 patients to have significant/complete resolution, 7 patients had mild resolution and 4 patients had no improvement. There were no reported intraocular pressure changes, pressure spikes, or lens changes in the group. Overall the study showed an improvement in 87% of participants and no side effects.Future studies are needed for review of safety and effectiveness of this treatment, but the initial results seem
promising. The News: Dexamethasone and ocular surface disease…Its Implication: Judicious use of low doses of
dexamethasone demonstrates improvement.