Assessing professional competence in optometry - a review of the development and validity of the written component of the competency in optometry examination (COE).

BACKGROUND: Credentialing assessment for overseas-educated optometrists seeking registration in Australia and New Zealand is administered by the Optometry Council of Australia and New Zealand. The aim was to review the validation and outcomes of the written components of this exam to demonstrate credentialing meets entry-level competency standards. METHODS: The Competency in Optometry Examination consists of two written and two clinical parts. Part 1 of the written exam comprises multiple choice questions (MCQ) covering basic and clinical science, while Part 2 has 18 short answer questions (SAQ) examining diagnosis and management. Candidates must pass both written components to progress to the clinical exam. Validity was evaluated using Kane's framework for scoring (marking criteria, item analysis), generalization (blueprint), extrapolation (standard setting), and implications (outcome, including pass rates). A competency-based blueprint, the Optometry Australia Entry-level Competency Standards for Optometry 2014, guided question selection with the number of items weighted towards key competencies. A standard setting exercise, last conducted in 2017, was used to determine the minimum standard for both written exams. Item response theory (Rasch) was used to analyse exams, produce reliability metrics, apply consistent standards to the results, calibrate difficulty across exams, and score candidates. RESULTS: Data is reported on 12 administrations of the written examination since 2014. Of the 193 candidates who sat the exam over the study period, 133 (68.9%) passed and moved on to the practical component. Ninety-one (47.2%) passed both the MCQ and SAQ exams on their first attempt. The MCQ exam has displayed consistently high reliability (reliability index range 0.71 to 0.93, average 0.88) across all 12 administrations. Prior to September 2017 the SAQ had a set cutscore of 50%, and the difficulty of the exam was variable. Since the introduction of Rasch analysis to calibrate difficulty across exams, the reliability and power of the SAQ exam has been consistently high (separation index range 0.82 to 0.93, average 0.86). CONCLUSIONS: The findings from collective evidence support the validity of the written components (MCQ and SAQ) of the credentialing of the competency of overseas-educated optometrists in Australia and New Zealand.

The effect of long-term wear of soft lenses of low and high oxygen transmissibility on the corneal epithelium.

PURPOSE: To measure the effects of long-term wear of soft lenses of low and high oxygen transmissibility (Dk) on basal epithelial appearance and epithelial thickness. METHODS: Sixty-three subjects were enrolled in a cross-sectional study. Seventeen high Dk lens wearers and 24 low Dk lens wearers who had worn lenses on an extended wear basis for more than 3 years (range: 3-22) were compared to a group of 22 age-matched subjects who had never worn contact lenses. Cell regularity and the intensity of light backscattered by the basal epithelium were assessed using confocal microscopy. Epithelial thickness was measured at the centre and at four peripheral locations using modified optical pachometry. RESULTS: Epithelial basal cells appeared less regular in low Dk lens wearers than high Dk wearers or controls (Mann-Whitney U-test, P=0.001). The intensity of backscattered light did not differ across groups (Kruskal-Wallis test, P=0.37). Low Dk wearers had the thinnest epithelium (46 (10) microm), followed by high Dk wearers (54 (14) microm) and controls (58 (9) microm; ANOVA, P

In vivo confocal microscopy of the human cornea.

AIMS: To describe the optics of in vivo confocal microscopy, its advantages over previous methods, and to summarise the literature that arose from its use for the observation of the human cornea. A critical review of the clinical usefulness of this new technology for the corneal examination is undertaken. METHODS: Confocal microscopes obtain increased resolution by limiting the illumination and observation systems to a single point. Rapid scanning is used to reconstruct a full field of view and allows for "real time" viewing. RESULTS: Coronal sections of the in situ epithelium, Bowman's membrane, stroma, and endothelium can be visualised at a resolution of 1-2 micro m. A backscattered light intensity curve allows objective measurements of sublayer thickness and corneal haze to be taken. In vivo confocal microscopy is therefore particularly useful in the areas of infective keratitis, corneal dystrophies, refractive surgery, and contact lens wear, where it aids in differential diagnosis and detection of subtle short and long term changes. Real time endothelial cell assessment can also be performed. CONCLUSION: Because of their ability to visualise living tissue at cellular levels, confocal microscopes have proved useful additions to the current clinical tools.

Epithelial split associated with wear of a silicone hydrogel contact lens.

PURPOSE: To describe the appearance and management of a superior epithelial arcuate lesion (SEAL) observed in association with the wear of a silicone hydrogel lens. METHODS: We present a case of a 30-year-old male who presented with a SEAL after 4 months of wear of a silicone hydrogel lens on a 30-day extended wear schedule. Bacteriological examination of the lenses and ocular adnexa was conducted at the time of the event. The clinical presentation and management are presented and compared to a review of cases associated with hydrogel lenses. RESULTS: The patient presented with symptoms of mild irritation. A linear splitwas noted in the superior peripheral cornea of the affected eye and was associated with limbal injection, stromal infiltrates, and fluorescein staining. Normal ocular biota was recovered from the lenses and eyelids of both eyes. Visual acuity remained unchanged and the lesion resolved following prophylactic treatment and discontinuation of lens wear for 8 days. CONCLUSIONS: The diagnosis and management of this SEAL case in a silicone hydrogel lens wearer mirrored that of previous events associated with hydrogel lenses. The possible etiologies of SEAL in this case are discussed and include mechanical irritation and dehydration of the lens surface.

Microcysts: clinical significance and differential diagnosis.

BACKGROUND: Microcysts are the most-distinctive and easily detectable indicator of contact lens-induced hypoxia. They should not be confused with cyst-like inclusions that occur in conditions such as Meesmann's dystrophy, bullous keratopathy, and Cogan's microcystic dystrophy, or with mucin balls, vacuoles, microcystic edema, and infiltrates. METHODS: Data from published literature and recent data from The Cornea and Contact Lens Research Unit (CCLRU) clinical trials involving low Dk and prototype high Dk soft contact lenses (SCLs) were examined. RESULTS: Extended wear with low Dk SCLs induces significant numbers of microcysts, whereas extended wear with high Dk SCLs does not. Subjects who transfer from low Dk to high Dk lenses have an initial increase in the number of microcysts after seven days that declines to normal levels over 1 to 3 months. Microcysts can be differentiated from other ocular conditions as they show reversed illumination, are 10- to 50-microm irregularly shaped dots, and are often associated with lens-induced hypoxia. CONCLUSIONS: Microcysts are easily observed and differentiated from other conditions in clinical practice. On average, fewer than ten microcysts per eye occur in nonhypoxic lens wear and, on average, more than 20 microcysts per eye are an indication of chronic hypoxia. The increase in microcyst numbers after transfer from low to high Dk lens wear is transitory and does not necessitate a period of no lens wear.

Superior epithelial arcuate lesions with soft contact lens wear.

BACKGROUND: Superior epithelial arcuate lesions (SEALs) are an infrequent and often asymptomatic complication of conventional soft contact lens wear. The characteristic arcuate pattern of the full-thickness corneal epithelial lesion usually occurs in the area covered by the upper eyelid, within 2 to 3 mm of the superior limbus in the 10- and 2-o'clock region. METHODS: Literature on SEALs and recent clinical records from clinical trials using two types of prototype high Dk soft contact lenses were reviewed to gain greater insights into the etiology of SEALs. RESULTS AND CONCLUSIONS: The reported low incidence of SEALs is partly because SEALs are not usually symptomatic. The etiology of SEALs is multifactorial. Our current hypothesis is that SEALs are produced by mechanical chaffing at the peripheral cornea. This chaffing occurs as a result of inward pressure of the upper lid, in an area where the peripheral corneal topography and lens design, rigidity, and surface characteristics combine to create excessive "frictional" pressure and abrasive shear force on the epithelial surface. Patient characteristics such as gender, age, and specific corneal and lid topographies also appear to influence the occurrence of SEALs. Prototype silicone hydrogel lenses are made from higher modulus materials with surfaces that seem to differ subtly in wettability in some patients. The prevalence of SEALs may well increase with the first generations of these lenses.

Microcyst response to high Dk/t silicone hydrogel contact lenses.

PURPOSE: To investigate the microcyst response to extended wear (EW) with high oxygen transmissible (Dk/t) silicone hydrogel lenses. METHODS: Microcysts were monitored for 12 months in subjects wearing low Dk/t hydrogel lenses on a 6-night EW schedule or high Dk/t hydrogel lenses on a 30-night EW schedule. Subjects wearing low Dk/t lenses transferred to the high Dk/t EW lenses and schedule after 12 months and were monitored for a further 6 months. RESULTS: The mean number of microcysts did not deviate from baseline in the high Dk/t group. Microcysts in the low Dk/t group increased over 12 months, and more microcysts were observed in low Dk/t lens wearers compared with high Dk/t lens wearers after 3 months. Microcysts increased in 50% of subjects 1 week after transfer to high Dk/t lenses and returned to baseline levels seen with high Dk/t lens wear within 3 months. CONCLUSIONS: EW with high Dk/t silicone hydrogel lenses did not cause an increase in microcyst numbers. It is not necessary to discontinue lens wear with patients who transfer from low to high Dk/t lenses because the increase in microcysts is transitory. This result has implications for practitioners when fitting and assessing the success of high Dk/t hydrogel lenses.

Effect of lens wear on corneal stroma: preliminary findings.

PURPOSE: The aim of the study was to measure the effects of long-term extended wear of hydrogel lenses. METHODS: Nine subjects wearing disposable hydrogel lenses and age- and sex-matched non-lens-wearing control subjects were enrolled. Using confocal microscopy, stromal keratocyte cell densities were measured. RESULTS: Anterior stromal keratocyte density was reduced in the lens-wearing group (544+/-206 cells/mm2) compared to the non-lens-wearing group (804+/-145 cells/mm2) (P < 0.01). Posterior stromal keratocyte density was lower in the lens-wearing group (514+/-111 cells/mm2) than in the control group (628+/-101 cells/mm2) (P < 0.05). CONCLUSIONS: These preliminary findings indicate that extended wear of hydrogel lenses reduces stromal keratocyte density. The mechanisms for this alteration may include hypoxic, cytokine-mediated or mechanical effects.