Eyeblink Frequency and Type in Relation to 3- and 9-O’Clock Staining and Gas Permeable Contact Lens Variables

CLEAR - Effect of contact lens materials and designs on the anatomy and physiology of the eye

This paper outlines changes to the ocular surface caused by contact lenses and their degree of clinical significance. Substantial research and development to improve oxygen permeability of rigid and soft contact lenses has meant that in many countries the issues caused by hypoxia to the ocular surface have largely been negated. The ability of contact lenses to change the axial growth characteristics of the globe is being utilised to help reduce the myopia pandemic and several studies and meta-analyses have shown that wearing orthokeratology lenses or soft multifocal contact lenses can reduce axial length growth (and hence myopia). However, effects on blinking, ptosis, the function of Meibomian glands, fluorescein and lissamine green staining of the conjunctiva and cornea, production of lid-parallel conjunctival folds and lid wiper epitheliopathy have received less research attention. Contact lens wear produces a subclinical inflammatory response manifested by increases in the number of dendritiform cells in the conjunctiva, cornea and limbus. Papillary conjunctivitis is also a complication of all types of contact lenses. Changes to wear schedule (daily disposable from overnight wear) or lens materials (hydrogel from SiHy) can reduce papillary conjunctivitis, but the effect of such changes on dendritic cell migration needs further study. These changes may be associated with decreased comfort but confirmatory studies are needed. Contact lenses can affect the sensitivity of the ocular surface to mechanical stimulation, but whether these changes affect comfort requires further investigation. In conclusion, there have been changes to lens materials, design and wear schedules over the past 20+ years that have improved their safety and seen the development of lenses that can reduce the myopia development. However, several changes to the ocular surface still occur and warrant further research effort in order to optimise the lens wearing experience.

Tear film evaluation and management in soft contact lens wear: a systematic approach

The human tear film is a highly ordered structure consisting of a thin layer of lipid on the surface and a thicker aqueous-mucin phase, which increases in mucin concentration toward the corneal epithelial cell layer. The health of the tear film and ocular surface influences the likelihood of being able to achieve successful contact lens wear. Contact lens discomfort and dryness are the most frequent reasons why contact lens wearers experience reduced wearing times, which can eventually lead to contact lens discontinuation. Comprehensive clinical assessment of tear film integrity and ocular surface health is therefore essential prior to commencing contact lens wear, to enable the ocular surface environment to be optimised to support lens wear. These parameters should also be evaluated over the course of contact lens wear, in order to identify any aspects requiring clinical management and ensure maintenance of optimal lens-wearing conditions. This review summarises current knowledge relating to the effects of soft contact lens wear on the tear film and ocular surface. It also provides a systematic approach to evaluating tear film and ocular surface integrity, in order to guide the clinical management of tear film anomalies with respect to contact lens wear.

Evaluation of signs and symptoms in 3- and 9-o'clock staining

PURPOSE

This study evaluates the relationship between bulbar hyperemia, conjunctival staining, lens comfort and 3- and 9-o'clock corneal staining in rigid gas permeable (GP) contact lens wear.

METHODS

The study involved 55 GP contact lens wearers (with and without 3- and 9-o'clock staining) and 26 non-lens wearers. Corneal staining was graded based on a specially designed image grading scale developed at the University of Maastricht. The Efron grading scale was used to grade bulbar hyperemia and conjunctival staining. Ocular comfort and lens comfort were analyzed using a visual analogue scale (VAS) and a questionnaire to differentiate symptomatic from asymptomatic subjects.

RESULTS

Bulbar hyperemia showed a significant but low correlation with corneal staining, and eyes with conjunctival staining showed more corneal staining than eyes without conjunctival staining. No correlation was found between staining in the nasal and temporal regions of the cornea in subjects with substantial 3- and 9-o'clock staining. No correlation was found between VAS comfort scores and corneal staining. In those subjects with substantial 3- and 9-o'clock staining, symptomatic subjects showed more corneal staining than asymptomatic subjects.

CONCLUSIONS

Practitioners are advised to evaluate both the nasal and temporal regions of the cornea when assessing 3- and 9-o'clock staining, and they should be hesitant to rely on the amount of bulbar hyperemia for the prediction of the severity of 3- and 9-o'clock staining. Assessment of conjunctival staining could potentially be a useful tool in clinical practice to identify patients at risk of developing 3- and 9-o'clock staining. The lack of correlation between corneal staining and lens comfort stresses the need for regular contact lens check-ups in GP lens wearers. It appears that the simple registration of the presence or absence of ocular symptoms is a better predictor of 3- and 9-o'clock staining than using VAS comfort scores.