Use of the Optomap with lid retraction and its sensitivity and specificity#

Background: Optomap uses the ultra‐wide field scanning laser ophthalmoscopy to provide retinal examination. It permits fundus examination without the use of a mydriatic, which is more comfortable for the patients. This paper determines the sensitivity and specificity of the Optomap for detecting retinal signs under non‐mydriatic conditions. Methods: Fifty‐four eyes identified with retinal/choroidal signs and eight normal eyes were recruited from 31 Hong Kong Chinese subjects. Photo‐documentation of fundal changes was obtained with the Optomap under non‐mydriatic conditions before a dilated fundus examination by a clinician using standard procedures. The eyelid was retracted using a cotton bud when necessary. Dilated fundus examinations were performed by another clinician using binocular indirect ophthalmoscopy and slitlamp biomicroscopy with a fundus lens. The Optomap images were evaluated by four other investigators under masked condition. The International Classification of Disease, Ninth Revision (ICD‐9‐CM) was adopted for recording retinal features. Screening results were compared with those obtained using the dilated fundus examination as the gold standard. Results: The cotton bud method for eyelid retraction showed an improvement in the area of retina that could be visualised. The sensitivity and specificity of the Optomap averaged 76.4 and 71.9 per cent, respectively. Some fundal signs were missed by all observers in the Optomap but not with the biomicroscope. These included white‐without‐pressure, lattice degeneration, paramacular drusen and pigmentary changes at central fundus. Conclusion: Optomap serves as a reliable screening tool for fundus examination especially because it covers a much wider area of the peripheral retina than other digital instruments for fundus photography.     

Relationship between corneal topographical changes and subjective myopic reduction in overnight orthokeratology: a retrospective study

Background: To investigate the relationship between the change in the manifest refractive error (ΔM), the change in apical corneal power (ΔACP) and initial corneal asphericity (Q) in overnight orthokeratology (ortho‐K). Methods: One hundred and twenty‐eight clinical records of children undergoing ortho‐K from a university optometry clinic were reviewed. The refractive and topographical data at baseline and at two‐week visit of 58 patients who fulfilled the inclusion criteria were retrieved and analysed. Results: Significant differences (p < 0.001) between the change in manifest refractive error and changes in the apical corneal power or the maximum change in corneal power (ΔMCP) within the treatment zone were found. Linear regression analysis was used to describe the change in manifest refractive error and the change in apical corneal power, and the change in manifest refractive error and the maximum change in corneal power, with the equations: ΔM = 0.91ΔACP + 0.57 (r = 0.78, p < 0.001) and ΔM = 0.93ΔMCP + 0.01 (r = 0.79, p < 0.001) respectively. On average, the change in apical corneal power underestimated the change in manifest refractive error by 0.34 ± 0.57 D; whereas on average, the maximum change in corneal power overestimated the change in manifest refractive error by 0.23 ± 0.57 D (paired‐t‐tests, p < 0.001). A low but significant correlation between initial corneal asphericity and the change in manifest refractive error (Spearman r = ‐0.33, p = 0.01) was observed. Conclusions: The change in apical corneal power underestimates the change in manifest refractive error in ortho‐K, whereas the maximum change in corneal power overestimates this parameter. Compared with retinoscopy and autorefraction, the change in apical corneal power is still useful for estimation of the change in manifest refractive error. Although the maximum change in corneal power appears to give a closer estimation of the change in manifest refractive error than the change in apical corneal power, there is no advantage in the use of maximum corneal power (manually located) instead of apical corneal power (a default given by the topographer) to estimate the change in manifest refractive error, as there is no significant difference in the estimations by either parameter. Initial corneal asphericity measured by the Medmont E300 corneal topographer has limited usage in predicting the change in manifest refractive error in overnight ortho‐K.     

Does the temperature of an artificial tear affect its comfort?

Background

Refrigerated eye‐drops have been advocated in cases of ocular allergies to provide a soothing effect upon instillation. This notion continues to be promoted by practitioners for artificial tears (AT) in the management of dry eye (DE) with little support in the literature. To further substantiate claims of a soothing effect of cold eye‐drops, the aim of this study was to determine if refrigeration of an AT enhanced the subjective comfort upon instillation.

Methods

Participants with mild to moderate DE participated in an open label contralateral study of two weeks duration. Each participant instilled Systane Ultra (Alcon Laboratories) in the morning (between 6.00–10.00 hours) and in the evening (between 18.00–22.00 hours). Participants were asked to report the subjective comfort immediately after both of these instillations, on a scale from 1 (poor) to 10 (excellent). This was done for ambient (aAT) and refrigerated (rAT) drops. An in vitro study evaluated if there were any changes in eye‐drop pH and osmolarity with refrigeration.

Results

Participants (n = 18, three male, 15 female, age 22–28 years, average 24.4 ± 1.6) reported mean comfort scores (± standard deviation) of 7.8 ± 0.9 and 7.6 ± 1.4, for the aAT and the rAT, respectively. Mean comfort scores (± standard deviation) for morning and evening, were 7.7 ± 1.2 and 7.8 ± 1.1, respectively. A non‐parametric Friedman test of differences among repeated measures was conducted and rendered a chi‐squared value of 3.74, which was not statistically significant (p = 0.29). The pH remained stable at 8.0 and the osmolality did not vary significantly with refrigeration.

Conclusion

There is no advantage, with respect to patient perceived comfort, in refrigerating the Systane Ultra (Alcon Laboratories) AT for mild to moderate DE.     

Customised aberration-controlling corrections for keratoconic patients using contact lenses

Technological advancements in the design of soft and scleral contact lenses have led to the development of customised, aberration-controlling corrections for patients with keratoconus. As the number of contact lens manufacturers producing wavefront-guided corrections continues to expand, clinical interest in this customisable technology is also increasing among both patients and practitioners. This review outlines key issues surrounding the measurement of ocular aberrations for patients with keratoconus, with a particular focus on the possible factors affecting the repeatability of Hartmann-Shack aberrometry measurements. This review also discusses and compares the relative successes of studies investigating the design and fitting of soft and scleral customised contact lenses for patients with keratoconus. A series of key limitations that should be considered before designing customised contact lens corrections is also described. Despite the challenges of producing and fitting customised lenses, improvements in visual performance and comfortable wearing times, as provided by these lenses, could help to reduce the rate of keratoplasty in keratoconic patients, thereby significantly reducing clinical issues related to corneal graft surgery. Furthermore, enhancements in optical correction, provided by customised lenses, could lead to increased independence, particularly among young adult keratoconic patients, therefore leading to improvements in quality of life.