Novel tear interferometry

Novel Tear Interferometer Made of Paper for Lipid Layer Evaluation

Hwang HS, Kim EC, Kim MS. Cornea 2014;33:826-831

The authors of this paper developed a very simple (and almost free) tear interferometer. It consists of a standard slit lamp biomicroscope and a piece of photocopy paper measuring 70mm wide by 20mm high with one end rounded and a 5mm hole punched in the rounded end to act as the observation window. The illumination area is located beside the observation window nearer to the rounded end of the ‘interferometer’. To achieve this the examiner needs to uncouple the illumination and viewing systems of the slit lamp. This is done by loosening the knurled knob toward the lower end of the illumination tower and twisting the tower so the light beam is directed to the side of the observation point. Holding the interferometer 10mm from the front of the patient’s eye, position the interferometer window at the centre of the cornea and the illumination beam just beside the window so that the incident and reflected light cross paths. Focus back and forth. The lipid layer interference pattern can be observed on the cornea through the window.

My comment:

Tear interferometry enables noninvasive evaluation of the tear film lipid layer. The current diagnostic instruments for this are expensive and therefore not widely available to clinicians, so this novel and extremely cheap interferometer puts the ability to perform the test into the hands of every clinician. It took me a while to get the hang of this but it’s fantastic once you do. Remember it took time to get proficient with a 90D! I have been able to take reasonable still photos, but like tear breakup time the dynamic changes you observe are more important.

The impact of ethnicity on contact lens wear

Contact Lens Care Solutions: A Pilot Study of Ethnic Differences in Clinical Signs and Symptoms

Lin MC, Yuen J, Graham AD. Eye & Contact Lens 2014; 40: 191-199

There are several anatomical and physiological differences between Asian and white eyes, many of which have the potential to affect contact lens wear. For example, compared to white eyes, Asian eyes tend to have an oblique angle of the palpebral fissure, a smaller vertical palpebral aperture, a flatter cornea, higher lid tension, shorter tear break up time, smaller tear meniscus volume and reduced pre-corneal tear film stability, among other things.

The authors of this study aimed to determine whether Asian and white subjects differ in clinical signs or subjective symptoms in response to the use of different biguanide-preserved contact lens care solutions. Investigators were masked to solution assignment during examinations, whereas subjects were not in order to avoid potential compliance difficulties. 42 subjects (15 Asian and 27 white) wearing lotrafilcon B silicon hydrogel contact lenses used a preservative-free lens care solution bilaterally for two weeks, then used two biguanide-preserved solutions (1: ReNu MPS; 2: AQuify MPS) contralaterally in randomly assigned eyes for four weeks. Fortnightly ocular surface examinations and symptomatology questionnaires were performed.

Results for solution 1 showed that most Asian and white subjects had grade 2 or greater corneal staining after 2 weeks (67% and 59% respectively) and 4 weeks (60% and 67% respectively). Solution 2 showed grade 2 or greater corneal staining in 40% of Asians after 2 weeks and in 13% after 4 weeks, but in only 4% of whites after 2 weeks and 0% after 4 weeks. Whites reported significantly better average comfort (P=0.046) and less dryness (P<0.001) than did Asians. The authors conclude that the ocular response to the use of contact lens care solutions and in subjective symptom reporting differs between Asians and whites, and that racial and ethnic differences should be considered when evaluating and treating contact lens patients in a clinical setting. My comment:

Something for you to all consider when prescribing contact lenses and care systems to your patients. There is no single contact lens-care solution combination that will be best for everybody. The best contact lens and solution system recommendation will vary for all your patients. Ethnicity and its impact on the anatomy and physiology of the eye and how this will affect contact lens success may also be important to consider.

Inflammation and dry eye

The Core Mechanism of Dry Eye Disease is Inflammation

Wei Y and Asbell PA. Eye & Contact Lens 2014; 40:248-256

This article reviews the evidence from recent basic, clinical, and translational research that the core mechanism of dry eye disease (DED) is inflammation. Currently we understand that environmental and/or microbial stresses trigger an innate immune response, leading to the activation and maturation of antigen-presenting cells (APCs). Mature APCs migrate into regional lymph nodes, generating and maintaining dry eye-specific and ocular-specific autoreactive CD4+ T cells and autoantibody secreting B cells, leading to adaptive immunity. Th17 cells travel to the ocular surface through efferent blood vessels, promoting the production of inflammatory mediators, lymphangiogenesis, and pathogenic immunocytic infiltration. This causes further damage to the ocular surface and progression of chronic inflammation.

The authors conclude that developing biomarkers for ocular surface inflammation will provide improved understanding of the mechanisms leading to DED, classification of the severity of DED, and objective metrics for outcome measures of treatment. They state that the chronicity of the disease suggests that dysregulation of immune mechanisms leads to a cycle of continued inflammation, along with alterations in both innate and adaptive immune responses. With inflammation being the core mechanism of DED, developing effective and safe anti-inflammatory treatments is likely to be beneficial to patients with DED.

My comment:

This paper reviews information from hundreds of studies and is worth reading. Research will lead to new diagnostic tests and treatments. In the meantime don’t forget that ‘white eyes’ can be very inflamed. One of the simplest things to do for patients with secretive tear dysfunction is test their response to topical steroids. Those who improve significantly are likely to benefit from low dose steroid therapy, cyclosporine and serum eye drops.

5-FU or MMC for OSSN

Long-term Outcomes after Adjunctive Topical 5-Flurouracil or Mitomycin C for the Treatment of Surgically Excised, Localized Ocular Surface Squamous Neoplasia

Bahrami B, Greenwell T and Muecke J. Clin Exp Ophthalmol 2014; 42:317-322

This long-term follow up of two prospective, non-comparative interventional case series aimed to report recurrence and complication rates of localised ocular surface squamous neoplasia (OSSN) treated with 5-fluorouracil (5-FU) or mitomycin-C (MMC) as an adjunctive treatment to surgical incision. Traditionally, the treatment of localised non-invasive lesions has involved surgical excision with or without intraoperative cryotherapy. The reported rate of recurrence of this approach ranges from 9% to 39%. In this study, of 153 eyes with histologically confirmed localised, non-invasive OSSN, 89 were treated with adjuvant 5-FU and 64 with adjuvant MMC. The main outcome measures were recurrence, complications and compliance. The 5-FU group had one recurrence, and there were no recurrences in the MMC group. 69% of 5-FU patients and 41% of MMC patients experienced side effects of the treatment. 6% of these side effects required intervention for treatment in the 5-FU group compared with 17% in the MMC group. Epiphora as a consequence of punctal stenosis was reported in 11 patients (17%) in the MMC group, and 9 patients (10%) in the 5-FU group, with all cases requiring intervention for their resolution. Lid toxicity, epiphora, superficial keratitis, corneal epithelial defect, and ectropion were all noted as side effects of treatment with 5-FU, whereas allergy, epiphora and ptosis were noted as side effects of treatment with MMC. None of these complications were vision-threatening. The authors concluded that long-term recurrence of localised OSSN is rare when 5-FU or MMC are used as adjunctive treatment to surgical excision. Most of the side effects experienced by patients receiving this treatment are transient and rarely limit compliance.

My comment:

Most ophthalmologists now use MMC to manage OSSN, either alone if the diagnosis is certain, or post excision. Side effects are common. I tell my patients that 100% of them will have some discomfort during the third cycle and they can be quite miserable on the fourth. Puntal plugs should be inserted to reduce the risk of punctal stenosis. 5-FU may be a viable alternative.

Recurrent corneal erosion syndrome

Clinical Presentation and Causes of Recurrent Corneal Erosion Syndrome: Review of 100 Patients

Diez-Feijóo E, Grau AE, Abusleme EI and Durán JA. Cornea. 2014; 33:571-575

This study examined the clinical features and etiology of recurrent corneal erosion syndrome (RCES) in 117 eyes of 100 patients. Study data included demography, etiology, corneal location, and association with meibomian gland dysfunction (MGD). The mean age of patients was 44.5 (range, 14-80) years. Attributed causes of RCES were previous minor trauma (46 eyes, 39.3%), epithelial basement membrane corneal dystrophy (20 eyes, 17.1%), photorefractive keratectomy (PRK) (20 eyes, 17.1%), laser-assisted in situ keratomileusis (LASIK) (9 eyes, 7.7%), and of unknown origin (22 eyes, 18.8%). 68.4% of RCES affected the inferior paracentral cornea, 21.3% affected the upper cornea, and 21.3% had a widespread location. An association with MGD was found in 59% of patients. The authors concluded that RCES has various etiologies, explaining the variety of possible clinical presentations of the disorder.

My comment:

RCES is reasonably common. This paper illustrates the widespread presentations of the condition, which can make diagnosis difficult. Preventing recurrence of episodes can also be difficult. It is interesting that PRK was found to be a cause, because phototherapeutic keratectomy (PTK) is considered to be an effective treatment for RCES. It is also worth noting that there seems to be a very strong association between MGD and RCES, so any lid pathology in a patient suffering from RCES should be treated in order to reduce the risk of recurrence.