Evaluation of corneal topography, pachymetry and higher order aberrations for detecting subclinical keratoconus.

PURPOSE: To compare corneal topography, pachymetry and higher order aberrations in keratoconic and normal eyes; to investigate their association in keratoconic eyes; and to determine their diagnostic ability for detecting subclinical keratoconus in a Nepalese population. METHODS: Ninety-six eyes of 48 keratoconus patients and 50 normal eyes of 50 control subjects were included in this study. The eyes of keratoconus patients were classified into four different study groups: subclinical, stage 1, stage 2 and advanced stage keratoconus. In each eye, corneal topography, pachymetry and corneal aberrometry indices were measured using a Sirius corneal tomographer. The study parameters of keratoconic eyes were compared with normal eyes, and the possible association of corneal aberrometry with topography and pachymetry indices was investigated. The area under curve (AUC) of receiver operating characteristic (ROC) curves along with optimal cutoff values with best sensitivity and specificity were also determined for each index to detect subclinical keratoconus. RESULTS: All the indices except average keratometry measurements (Kavg and mmavg ) and spherical aberration (SA) were found to be significantly different in subclinical keratoconus compared to the control group (p < 0.05). In keratoconic eyes, all corneal aberrations were significantly correlated with the topography and pachymetry indices (range of ρ: -0.25 to 0.96; all p < 0.05) except for trefoil and minimum corneal thickness (Thkmin ). All the indices except Kavg , mmavg and SA showed excellent diagnostic ability (AUC > 0.90) in detecting subclinical keratoconus. The cutoff values proposed for the asymmetry index of the corneal back surface (SIb ), Strehl ratio of point spread function (PSF), coma and Baiocchi-Calossi-Versaci index of corneal back surface (BCVb ) each showed excellent sensitivity (100%) and specificity (≥97%). CONCLUSIONS: Corneal higher order aberrations were found to be significantly elevated in subclinical keratoconus compared to healthy controls. SIb , PSF, coma and BCVb were identified as the most powerful Sirius indices for the detection of subclinical keratoconus.

Spectacle non-tolerance in clinical practice - a systematic review with meta-analysis.

PURPOSE: Spectacle non-tolerance or adverse events to spectacle wear are serious concerns for both patients and practitioners. Non-tolerance may contribute to a negative impact on the practitioner's ability and practice. Therefore, a detailed understanding of frequency and causes of spectacle non-tolerance in clinical ophthalmic practice is essential. This review aimed to determine the prevalence and causes of non-tolerance to spectacles prescribed and dispensed in clinical practice. METHOD: The current systematic review included quantitative studies published in the English language that reported spectacle non-tolerance in clinical practice. A comprehensive search was conducted in PubMed, Scopus and the Web of Science database for studies published until 13 July 2020. An adapted version of the Newcastle-Ottawa Scale (NOS) modified for cross-sectional studies was used to assess the quality of each included study. Five investigations with 205,478 study participants were included in the review. The prevalence of spectacle non-tolerance from individual studies was pooled using MetaXL software. The pooled prevalence of spectacle non-tolerance was 2.1% (95% CI: 1.6-2.7) ranging from 1.6% to 3.0%. The papers were also reviewed to identify the potential causes of non-tolerances. Nearly half reported that non-tolerance (47.4%) was due to an error in refraction. Other causes identified were errors related to communication (16.3%), dispensing (13.5%), non-adaptation (9.7%), data entry (8.7%), binocular vision (7.4%) and ocular pathology (6.4%). SUMMARY: This review improves our understanding of spectacle non-tolerance in clinical practice. This is important because non-tolerance may lead to spectacle wear discontinuation, which may deprive patients of optimal vision. Increased non-tolerance in clinical practice may affect a clinician's reputation and incur additional costs associated with reassessments and replacements. Spectacle non-tolerance occurred due to a multitude of factors related to optical dispensing and wearer adaptation. Therefore, there is a need for vigilance while prescribing spectacles. The limited evidence highlights the need for more studies, especially in limited-resource settings, to improve the quality of refractive error services.

Prevalence of refractive errors in Nepalese children and adults: a systematic review with meta-analysis.

CLINICAL RELEVANCE: Country-specific estimates of the prevalence of refractive errors are important to formulate national eye health policies for refractive care services. BACKGROUND: The purpose of this study was to systematically synthesise available literature and estimate the prevalence of refractive errors in the Nepalese population. METHODS: PubMed, Scopus, and Web of Science databases were systematically searched for articles on refractive errors and presbyopia published in English language until 27 September 2022. Population and school-based quantitative, cross-sectional prevalence studies and Rapid Assessment of Avoidable Blindness survey repository data were included. The quality of the included studies was assessed using the Newcastle Ottawa scale adapted for cross-sectional studies. Data extraction was performed with consensus among the reviewers. Meta-analysis of the prevalence was performed using the Random effects model to estimate the pooled proportions. RESULTS: A total of 38 studies with 101 701 participants were included: 18 studies in children (n = 31 596) and 20 in adults (n = 70 105). In children, the estimated pooled prevalence of overall refractive errors was 8.4% (95% CI: 4.8 to 12.9) with myopia, hypermetropia and astigmatism prevalent in 7.1% (95% CI: 3.7 to 11.4), 1.0% (95% CI: 0.7 to 1.3) and 2.2% (95% CI: 0.9 to 3.9), respectively. In adults, the prevalence of refractive errors, uncorrected refractive errors, and uncorrected presbyopia were 11.2% (95% CI: 8.0 to 14.9), 7.3% (95% CI: 5.4 to 9.5) and 78.9% (95% CI: 69.1 to 87.3), respectively. CONCLUSIONS: The pooled prevalence of refractive errors is relatively low while uncorrected refractive errors and presbyopia are high in Nepalese population suggesting a need for better access to refractive care services in the country. The paucity of quality evidence on prevalence of refractive errors, particularly in children, indicates a need for a well-designed population-based study to accurately estimate the current prevalence of refractive errors.

Compliance and hygiene behaviour among soft contact lens wearers in the Maldives.

BACKGROUND: Significant levels of non-compliance and poor hygiene among contact lens wearers have been reported previously from different parts of the world. This survey aimed at identifying the scope of hygiene and non-compliant behaviour of soft contact lens wearers in the Maldives. METHODS: Established soft lens wearers attending two eye clinics in Male' city, were interviewed in office or via telephone. A set of interviewer-administered questions was used to access the subjective response on compliance and hygiene behaviour (hand and lens case hygiene, water exposure, adherence to lens replacement schedule, dozing and overnight wear, awareness of aftercare visits and reuse of disinfecting solution). Participants were also asked to rate themselves as a contact lens user based on their perceived compliance and hygiene practices. RESULTS: Out of 107 participants, 79 (74.8 per cent) were interviewed in the office and the rest via telephone. The majority of lens wearers were female, office workers and students, with a mean age of 20.64 ± 4.4 years. Mean duration of lens wear was 28.04 ± 8.36 months. Most of them were using spherical lenses (86.9 per cent) on a daily wear basis (96.3 per cent). Major reported forms of non-compliance were poor hand hygiene (60.7 per cent), lack of aftercare awareness (39.3 per cent), water exposure (35.5 per cent) and over-use of lenses (24.3 per cent). While females were more likely to overuse their lenses than males (p < 0.005), other socio-demographic factors were not associated with reported non-compliance. Although around 90 per cent of the participants considered themselves average or good contact lens wearers, most exhibited some form of non-compliant and poor hygienic behaviour. CONCLUSION: A significant number of Maldivian contact lens wearers exhibited poor levels of hygiene and compliance with contact lenses and lens care systems. An effective educational reinforcement strategy needs to be developed to modify lens wearers' non-compliance.