Ocular and Nonocular Adverse Events during 3 Years of Soft Contact Lens Wear in Children.

SIGNIFICANCE: Children are being fitted at younger ages with soft contact lenses for myopia control. This 3-year investigation of adverse events related to contact lens wear in 7- to 11-year-old participants helps optometrists understand what to expect when fitting children with soft contact lenses. PURPOSE: The purpose of this article is to report the frequency and type of ocular and nonocular adverse events related to soft contact lens wear in children. METHODS: Seven- to 11-year-old children wore soft contact lenses for 3 years. Adverse events were defined by a slit-lamp examination finding of grade 3 or worse; parental report of a clinically meaningful change (determined by the examiner) in eyes, vision, or health; or a clinically meaningful response (determined by examiner) to a symptom checklist. Adverse events were categorized and reported by examiners and finalized by the Executive Committee. The presence or absence of an infiltrate and a list of diagnoses was determined at the conclusion of the study. RESULTS: The 294 participants wore their contact lenses 73.0 ± 26.5 hours per week, and 220 (74.8%) encountered at least 1 adverse event. Of the 432 adverse events, 75.2% were ocular, and 24.8% were nonocular. Contact lens wear was probably or definitely related to 60.6% of the ocular and 2.8% of the nonocular adverse events. None of the ocular adverse events were serious or severe or caused permanent contact lens discontinuation. The corneal infiltrate incidence was 185 cases per 10,000 patient-years of wear (95% confidence interval, 110 to 294). The incidence of moderate ocular adverse events that were definitely or probably related to contact lens wear was 405 cases per 10,000 patient-years of wear (95% confidence interval, 286 to 557). CONCLUSIONS: The adverse events experienced by 7- to 11-year-old myopic children rarely required meaningful treatment and never led to permanent discontinuation of contact lens wear or loss of best-corrected vision.

IOP and Optic Nerve Head Morphology during Scleral Lens Wear.

SIGNIFICANCE: Scleral lenses (SLs) are increasing in scope, and understanding their ocular health impact is imperative. The unique fit of an SL raises concern that the landing zone causes compression of conjunctival tissue that can lead to resistance of aqueous humor outflow and increased intraocular pressure (IOP). PURPOSE: This study aimed to assess changes in optic nerve head morphology as an indirect assessment of IOP and evaluate other IOP assessment methods during SL wear. METHODS: Twenty-six healthy adults wore SL on one randomly selected eye for 6 hours, whereas the fellow eye served as a control. Global minimum rim width (optical coherence tomography) and IOP (Icare, Diaton) were measured at baseline, 2 and 6 hours after SL application, and again after SL removal. Central corneal thickness, anterior chamber depth, and fluid reservoir depth were monitored. RESULTS: Minimum rim width thinning was observed in the test (-8 µm; 95% confidence interval [CI], -11 to -6 µm) and control (-6 µm; 95% CI, -9 to -3 µm) eyes after 6 hours of SL wear (P < .01), although the magnitude of thinning was not significantly greater in the lens-wearing eyes (P = .09). Mean IOP (Icare) significantly increased +2 mmHg (95% CI, +1 to +3 mmHg) in the test eyes (P = .002), with no change in the control eyes. Mean IOP changes with Diaton were +0.3 mmHg (95% CI, -0.9 to +3.2 mmHg) in the test eyes and +0.4 mmHg (95% CI, -0.8 to +1.7 mmHg) in the control eyes. However, Diaton tonometry showed poor within-subject variation and poor correlation with Icare. No clinically significant changes were observed in central corneal thickness or anterior chamber depth. CONCLUSIONS: This study suggests that SLs have a minimal effect on IOP homeostasis in the normal eye during SL wear and an insignificant impact on the optic nerve head morphology in healthy adult eyes.

Effect of High Add Power, Medium Add Power, or Single-Vision Contact Lenses on Myopia Progression in Children: The BLINK Randomized Clinical Trial.

Importance: Slowing myopia progression could decrease the risk of sight-threatening complications. Objective: To determine whether soft multifocal contact lenses slow myopia progression in children, and whether high add power (+2.50 D) slows myopia progression more than medium (+1.50 D) add power lenses. Design, Setting, and Participants: A double-masked randomized clinical trial that took place at 2 optometry schools located in Columbus, Ohio, and Houston, Texas. A total of 294 consecutive eligible children aged 7 to 11 years with -0.75 D to -5.00 D of spherical component myopia and less than 1.00 D astigmatism were enrolled between September 22, 2014, and June 20, 2016. Follow-up was completed June 24, 2019. Interventions: Participants were randomly assigned to wear high add power (n = 98), medium add power (n = 98), or single-vision (n = 98) contact lenses. Main Outcomes and Measures: The primary outcome was the 3-year change in cycloplegic spherical equivalent autorefraction, as measured by the mean of 10 autorefraction readings. There were 11 secondary end points, 4 of which were analyzed for this study, including 3-year eye growth. Results: Among 294 randomized participants, 292 (99%) were included in the analyses (mean [SD] age, 10.3 [1.2] years; 177 [60.2%] were female; mean [SD] spherical equivalent refractive error, -2.39 [1.00] D). Adjusted 3-year myopia progression was -0.60 D for high add power, -0.89 D for medium add power, and -1.05 D for single-vision contact lenses. The difference in progression was 0.46 D (95% CI, 0.29-0.63) for high add power vs single vision, 0.30 D (95% CI, 0.13-0.47) for high add vs medium add power, and 0.16 D (95% CI, -0.01 to 0.33) for medium add power vs single vision. Of the 4 secondary end points, there were no statistically significant differences between the groups for 3 of the end points. Adjusted mean eye growth was 0.42 mm for high add power, 0.58 mm for medium add power, and 0.66 mm for single vision. The difference in eye growth was -0.23 mm (95% CI, -0.30 to -0.17) for high add power vs single vision, -0.16 mm (95% CI, -0.23 to -0.09) for high add vs medium add power, and -0.07 mm (95% CI, -0.14 to -0.01) for medium add power vs single vision. Conclusions and Relevance: Among children with myopia, treatment with high add power multifocal contact lenses significantly reduced the rate of myopia progression over 3 years compared with medium add power multifocal and single-vision contact lenses. However, further research is needed to understand the clinical importance of the observed differences. Trial Registration: ClinicalTrials.gov Identifier: NCT02255474.

Assessing Scleral Contact Lens Satisfaction in a Keratoconus Population.

PURPOSE: To assess perceived comfort and related experiences of adapted keratoconic scleral contact lens (17-18.2 mm) wearers with a history of wearing other contact lens modalities and to compare these subjective clinical effects with previous experiences. METHODS: Twenty-four keratocones were recruited, signed an informed consent approved by the University Internal Review Board, and were asked to complete a survey and a dry eye questionnaire. RESULTS: Previous lens wearing experience included soft, piggy back, and hybrid lenses but predominantly was corneal gas permeable. An overwhelming majority strongly preferred the comfort and vision with the scleral contact lenses. This cohort of keratoconus patients were on average dry eye suspects according to a dry eye questionnaire but contained individuals with either normal or significantly dry eye scores. However, patients stated that they experienced less dryness with their scleral lenses, but slightly more than half of these patients experienced, at least occasionally, midday fogging. CONCLUSIONS: The scleral contact lenses are extremely well accepted by keratoconic patients because of comfort and vision these devices provide. For many patients, they offer further relief from dryness symptoms. However, midday fogging remains a limitation for many wearers.

Clinical evaluation of rigid gas permeable contact lenses and visual outcome after repaired corneal laceration.

OBJECTIVE: To evaluate the clinical value of rigid gas permeable contact lenses (RGPCLs) in patients with traumatic corneal scarring and address implications of primary corneal repair. METHODS: Eighteen subjects with a history of corneal laceration were fit with RGPCLs. Scar locations were divided into two zones; each patient was examined using Pentacam. Entering data included uncorrected visual acuity (UCVA), spectacle-corrected visual acuity (SVA), time between injury and RGPCL fitting, location and size of scar, and amount of corneal astigmatism. Follow-up data included RGPCL visual acuity (RGPCLVA), RGPCL-related complications, and dropout characteristics. Visual acuity values were converted to logMAR for analysis. RESULTS: No serious complications occurred. The average time between suture removal and RGPCL fitting was 5.7±5.5 months. Average corneal astigmatism was -3.44±2.09 diopters. One subject had developed corneal ectasia. RGPCLVA was more than 0.1 in three subjects: one experienced primary corneal repair complications, and two subjects (<10 years) developed amblyopia. In both zones, the difference in RGPCLVA outcome between zone I and zone II was not statistically significant (F=0.060, P=0.809). The difference between SVA in zones I and II was found to be statistically significant (F=6.131, P=0.026), as were the differences between SVA and RGPCLVA (F=8.598, P=0.010). The scar size had no significant influence on RGPCLVA, SVA, or UCVA. Four participants (22.2%) were successfully fit. Dropout characteristics included ocular discomfort, inconvenience, parental apprehension, and low motivation. CONCLUSIONS: Rigid gas permeable contact lens is an ideal method for evaluating visual potential in patients with traumatic corneal astigmatism. Pentacam examinations of those patients with poor RGPCLVA can help an ophthalmologist find and understand existing problems in suture techniques.

Potential pro-inflammatory impact of scleral lens midday fogging on human corneal epithelial cells: An in vitro study.

PURPOSE: Midday fogging (MDF) occurs when particulate material accumulates in the fluid reservoir (FR) beneath scleral lenses (SL), and its impact on epithelial cells is unknown. This study examines the in vitro pro-inflammatory effect of the FR on human corneal epithelial cells in varying degrees of MDF. METHODS: Normal SL neophytes were recruited to wear SL 8 h daily for 4 days. Following 8 h on days 1 and 4, optical coherence tomography (OCT) images were acquired for MDF quantification using ImageJ, and the FR was collected. FR samples from the same eye were later pooled, diluted 2-fold and applied on human telomerase-immortalized corneal epithelial (hTCEpi) cells cultured on Terasaki microwell plates. Tumor necrosis factor (TNF)-α and culture media were used as positive and negative controls, respectively. After a 30-minute treatment, the nuclear factor-kappa B (NF-κB) pathway was measured by NF-κB-p65 immunofluorescence and images were analyzed with ImageJ. Pearson's correlation was conducted to determine the association between median nuclear fluorescence and MDF. RESULTS: Fourteen FR samples with a mean volume of 22 ± 16 µl were tested. Mean MDF severity following 8 h of SL wear was 25 ± 17 units (range 7 - 64). The median nuclear fluorescence (NF-κB-p65 translocation) in cultured hTCEpi cells ranged from 31.43 to 45.16 while the negative and positive controls were 44.71 ± 1.72 and 108.77 ± 68.38, respectively. Although a potential positive trend between MDF and median nuclear fluorescence was observed, Pearson's correlation analysis revealed no significant association (r = +0.48, P = 0.09). CONCLUSIONS: The results suggest that the FR can trigger NF-κB-p65 translocation in hTCEpi cells, which may be associated with MDF severity. This study introduces the use of Terasaki microwell plates for immunofluorescence studies of the FR. The technique is simple, minimizes sample usage, and does not require expensive instrumentation.

Central versus peripheral thickness in the human cornea explained.

PURPOSE: The human cornea is thicker in the periphery than the center and it has been suggested that this must be due to greater numbers of lamellae in the peripheral corneal stroma. The purpose of this study was to use high-resolution ultrastructural imaging to determine if the greater thickness of the peripheral cornea is due to the presence of more lamellae or if there is some other anatomical explanation. METHODS: In this study, full thickness corneas from three human donors were processed for light microscopy (LM) and transmission electron microscopy (TEM). Images were taken in three distinct stromal regions (anterior, middle, and posterior) from the central and peripheral cornea. Stromal thickness was evaluated by LM while TEM was used to evaluate numbers and thicknesses of lamellae, mean collagen fibril diameter, and mean collagen fibril density. RESULTS: Mean stromal thickness was significantly thinner in the central (415 ± 34 µm) compared to the peripheral (536 ± 29 µm) cornea (P = 0.009). Numbers of lamellae were not significantly different between central (246 ± 14) and peripheral (251 ± 14) cornea. Average lamellar thickness was not different across all regions of the cornea, except for the peripheral posterior where the lamellae were approximately 50 % thicker (P < 0.05). Collagen fibril diameters were larger in the peripheral cornea by approximately 30 % when compared to the central cornea, in all regions (P < 0.01). CONCLUSIONS: This study shows that it is an increase peripheral posterior lamellar thickness, rather than an increase in the number of lamellae, that accounts for the increase in corneal stromal thickness in the periphery of the human cornea. While collagen fibril diameters are greater throughout the peripheral stroma, the lamellae in the mid and anterior peripheral stroma are not thicker than centrally.

Anatomical and physiological considerations in scleral lens wear: Intraocular pressure.

Intraocular pressure (IOP) is maintained through complex and interrelated systems which control aqueous production and drainage, and it has been suggested that scleral lens (SL) wear may disrupt these vital homeostatic processes. This review provides an overview of anatomical and physiological processes that control IOP, identifies potential effects of SLs on these regulatory mechanisms, and examines studies that have attempted to quantify the effect of SLs on IOP. Lack of access to the cornea during SL wear makes accurate assessment of IOP challenging; therefore, a range of different assessment techniques and instruments have been employed to quantify IOP during and following SL wear. Some studies have evaluated IOP using standard techniques prior to lens application and following lens removal, or through a large central fenestration. Other studies have utilised instruments that facilitate assessment of IOP on the peripheral cornea or conjunctiva overlying the sclera (e.g. Schiotz, transpalpebral, and pneumatonometry). Two studies have recently evaluated changes in optic nerve structure during SL wear. Conflicting results have been reported on this topic, much of which examines changes in IOP in healthy subjects over limited periods of time. Currently, only a few studies have reported on long-term effects of SL wear on IOP in habitual SL wearers (after lens removal). Future research in this area must not only consider the fact that ocular conditions treated with SLs may potentially alter corneal biomechanical properties which can influence IOP, but also that these properties may be further altered by SL wear. Monitoring other risk factors for glaucoma (permanent alterations in optic nerve physiology, visual field defects) could provide a more comprehensive assessment of potentially increased risk of glaucomatous optic neuropathy due to SL wear. Ongoing clinical assessment of optic nerve structure and function is advisable in patients at risk for glaucoma who require SLs.

Nonpolar Lipids Contribute to Midday Fogging During Scleral Lens Wear.

Purpose: To determine correlations between lipids in the fluid reservoir (FR) and the severity of midday fogging (MDF) in scleral lens (SL) wear. Methods: SL neophytes were recruited to wear custom SL for 4 days, examined after 8 hours on days 1 and 4. Lens vault and MDF were quantified from anterior segment optical coherence tomography (AS-OCT), and the FR was collected and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Relative abundance of lipids was compared to MDF scores using nonparametric correlation testing (Spearman rank). Ocular surface and SL fitting characteristics (lens vault, fitting curves) were likewise compared to MDF. Results: Thirteen participants (26 eyes, 69% female, 28 ± 9 years old) were included in this study. MDF severity after 8 hours of SL wear was 33 ± 29 units on day 1 and 28 ± 24 units on day 4 (r = .94; P < 0.01). Twelve samples were analyzed using LC-MS/MS, and a total of 170 distinct lipid species were detected. The lipid classes with greatest correlation to MDF were the wax esters (r = .73, P = 0.01), cholesteryl esters (r = .59; P = 0.049), and triacylglycerols (r = .64, P = 0.03). Polar lipids were observed abundantly in all samples. None of the measured ocular surface or fitting outcomes were correlated to MDF. Conclusions: Nonpolar lipids were the greatest contributors to MDF among these normal participants. Polar lipids may be due to cellular debris, although they do not appear contributory to MDF.

A comparison of subjective and objective conjunctival hyperaemia grading with AOS® Anterior software.

CLINICAL RELEVANCE: This study evaluates a commercially available conjunctival hyperaemia grading system, providing validation of an important tool for ocular surface research and clinical trials. BACKGROUND: Bulbar conjunctival hyperaemia is a sign of ocular surface inflammation, and proper measurement is essential to clinical care and trials. The aim of this study was to assess the validity and repeatability of an objective grading system in comparison with subjective grading. METHODS: This study was a retrospective, randomised analysis of 300 bulbar conjunctival images that were collected at an academic institution. The images used were de-identified and collected from the Keratograph K5 and Haag-Streit slitlamp. Six investigators graded the images with either a 0.1 or 0.5 unit scaling using a 0-4 Efron grading scale. Three of the investigators also imported the images into the AOS ® Anterior software and graded them objectively. All measurement techniques were assessed for repeatability and comparability to each other. RESULTS: Mean hyperaemia with the objective system (1.1 ± 0.7) was significantly less than the subjective grading (2.0 ± 0.8) (P < 0.001). Both inter- and intra-subject repeatability of the objective system (0.15) was better than the subjective methods (1.70). CONCLUSION: The results showed excellent repeatability of the AOS ® Anterior objective conjunctival hyperaemia grading software, although they were not found to be interchangeable with subjective scores. This system has value in monitoring levels of hyperaemia in contact lens wearers and patients in clinical care and research trials.

Anatomical and physiological considerations in scleral lens wear: Eyelids and tear film.

Scleral lenses can affect a range of anterior segment structures including the eyelids and the tears. The eyelids, consisting of the outer skin layer, the middle tarsal plate, and the posterior palpebral conjunctiva, provide physical protection and house the meibomian glands and cilia which have important and unique functions. Tears consist of a mix of aqueous, mucus, and lipidomic components that serve vital functions of lubricity, protection, and nourishment to the ocular surface. Both the eyelids and the tear film interact directly with scleral lenses on the eye and can affect but also be impacted by scleral lens wear. The purpose of this paper is to review the anatomy and physiology of the eyelids and tear film, discuss the effects and impacts of the scleral lenses on these structures, and identify areas that require further research.

Scleral lens wear: Measuring inflammation in the fluid reservoir.

PURPOSE: To measure inflammatory mediators in the scleral lens fluid reservoir (FR) in healthy eyes and to compare them to basal tear samples after 8-hs (8h) and 4-days (4d) of scleral lens (SL) wear. METHODS: Fifteen normal, habitual soft contact lens wearers were fitted with 14.8- or 15.4-mm SLs (Zenlens, Alden Optical, USA). Basal ocular surface tears and FR samples were collected after 8h and 4d of daily SL wear. Levels of interleukin (IL) -4 and -8, matrix metalloproteinase (MMP)-7, -9, and -10, and tissue inhibitor of MMPs (TIMPs) 1-4 were measured in all samples using Luminex assays. Visual acuity, corneal and conjunctival staining, and comfort assessments were completed at the baseline, 8h and 4d time points. RESULTS: MMP-9 and MMP-10 were greater in FR than basal ocular surface tears. After 8h of SL wear, the median concentration of MMP-9 in the FR and basal tears were 62.7 and 15.2 ng/mL, respectively (p = 0.047). Likewise, MMP-10 was significantly greater in FR compared to basal tears, after 8h (25.8 ng/mL vs 2.8 ng/mL, p < 0.001) and 4d (2.1 ng/mL vs17.2 ng/mL, p = 0.047). IL-4 and IL-8 levels were greater in FR but not significantly at 8h (2.2 vs 3.1 ng/mL; and 0.1 vs 0.4 ng/mL, respectively) or 4d (0.9 vs 3.5 ng/mL; 0.0 vs 0.2 ng/mL). MMP-7 was not affected by SL wear after 8h (46.0 basal vs 54.4 ng/mL FR) or 4d (34.2 vs 87.5 ng/mL). Visual acuity, corneal and conjunctival staining did not change; comfort was reduced in SL compared to soft contact lens wear. CONCLUSIONS: This is the first study to compare the FR with the basal ocular surface tears. MMP-9 and MMP-10 were elevated in the FR after several hours of SL wear, suggesting potential clinical implications of SL wear and deserves further investigation.

Anatomical and physiological considerations in scleral lens wear: Conjunctiva and sclera.

While scleral lenses have been fitted using diagnostic lenses or impression moulding techniques for over a century, recent advances in anterior segment imaging such as optical coherence tomography and corneo-scleral profilometry have significantly improved the current understanding of the anatomy of the anterior eye including the morphometry of the conjunctiva, sclera, and corneo-scleral junction, as well as the ocular surface shape and elevation. These technological advances in ocular imaging along with continual improvements and innovations in scleral lens design and manufacturing have led to a global increase in scleral lens prescribing. This review provides a comprehensive overview of the conjunctiva and sclera in the context of modern scleral lens practice, including anatomical variations in healthy and diseased eyes, the physiological impact of scleral lens wear, potential fitting challenges, and current approaches to lens modifications in order to minimise lens-induced complications and adverse ocular effects. Specific topics requiring further research are also discussed.

A measure of tear inflow in habitual scleral lens wearers with and without midday fogging.

PURPOSE: The purpose of this pilot study was to evaluate tear inflow in a scleral lens system using fluorophotometry, and indirectly assess the exchange of the tear reservoir in habitual scleral lens wearers with the presence or absence of midday fogging (MDF). METHODS: Habitual scleral lens wearers (n=23) and normal scleral lens neophytes (n=10) were recruited. Of the 23 habitual wearers, 11 of them experienced MDF and 12 did not have a diagnosis of MDF. Contact lens-fitting characteristics were evaluated using ocular coherence tomograpy (OCT) and biomicroscopy. High molecular weight fluorescein (FITC) Dextran was instilled into the tear reservoir beneath the scleral lens, and the tear fluid fluorescein concentration was measured using the Fluorotron fluorophotometer. Calculated fluorescein concentrations were plotted over time to measure the fluorescein decay rate of the tear fluid beneath the scleral lens, which was used to calculate the tear exchange rate. RESULTS: There was no significant difference in tear inflow between the MDF group (mean: 0.111%) and the non-MDF group (mean: 0.417%), and there was a high amount of variability seen in the rates (p = 0.26). In addition, there was no significance between the tear reservoir thickness in the MDF (283um) and non-MDF (326um) groups (p = 0.53). CONCLUSIONS: The relationship between the amount of tear exchange during scleral lens wear and the incidence of MDF was not significant. Additional studies are needed to further examine the role of tear exchange in MDF and address the causes of variability to improve measurement techniques with fluorophotometry in the scleral lens system.

Peripheral Refraction and Eye Lengths in Myopic Children in the Bifocal Lenses In Nearsighted Kids (BLINK) Study.

PURPOSE: Provide a detailed assessment of peripheral refractive error and peripheral eye length in myopic children. METHODS: Subjects were 294 children aged 7 to 11 years with -0.75 to -5.00 diopter (D) of myopia by cycloplegic autorefraction. Peripheral refraction and eye length were measured at ±20° and ±30° horizontally and vertically, with peripheral refraction also measured at ±40° horizontally. RESULTS: Relative peripheral refraction became more hyperopic in the horizontal meridian and more myopic in the vertical meridian with increasing field angle. Peripheral eye length became shorter in both meridians with increasing field angle, more so horizontally than vertically with correlations between refraction and eye length ranging from -0.40 to -0.57 (all P < 0.001). Greater foveal myopia was related to more peripheral hyperopia (or less peripheral myopia), shorter peripheral eye lengths, and a consistent average asymmetry between meridians. CONCLUSIONS: Peripheral refractive errors in children do not appear to exert strong local control of peripheral eye length given that their correlation is consistently negative and the degree of meridional asymmetry is similar across the range of refractive errors. The BLINK study will provide longitudinal data to determine whether peripheral myopia and additional peripheral myopic defocus from multifocal contact lenses affect the progression of myopia in children. TRANSLATIONAL RELEVANCE: Local retinal control of ocular growth has been demonstrated numerous times in animal experimental myopia models but has not been explored in detail in human myopia development. These BLINK baseline results suggest that children's native peripheral optical signals may not be a strong stimulus for local growth responses.

Complications and fitting challenges associated with scleral contact lenses: A review.

INTRODUCTION: The modern scleral contact lens (ScCL) has evolved from the very first contact lens fitted 128 years ago. Originally manufactured in glass and oxygen impermeable plastics, these lenses are available today in high Dk gas permeable materials that allow permeation of oxygen, reducing many of the complications that were seen with older generation ScCL. However, as with any new contact lens modality, the modern ScCL brings with it a new set of complications and fitting limitations. METHODS: Pubmed searches under different keywords were conducted. RESULTS: Existing literature provides some reports of infection with the scleral devices, although these are often seen in severely compromised corneas, while hypoxic and inflammatory complications are rarely reported in the literature. Furthermore, the somewhat complex relationship of a scleral lens on the eye can create fitting and removal challenges. Anomalies such as conjunctival prolapse, epithelial bogging, midday fogging, and limbal bearing have been reported, and appear to be unique sequelae to scleral lens wear. CONCLUSION: Although this revolutionary technology broadens the scope in which practitioners can treat patients with irregular ocular surfaces, reports of these complications indicate that there is still a need for continued research to further enhance the clinical outcomes of this promising contact lens modality.

Measurement of the photoreceptor pointing in the living chick eye.

The chick eye is used in the study of ocular growth and emmetropization; however optical aberrations in the lens and cornea limit the ability to visualize fine retinal structure in living eyes. These aberrations can be corrected using adaptive optics (AO) allowing for cellular level imaging in vivo. Here, this capability is extended to measure the angular tuning properties of individual photoreceptors. The left eyes from two White Leghorn chicks (Gallus gallus domesticus) labeled chick A and chick B, were imaged using an AO flood illuminated fundus camera. By translating the entrance pupil position, the same retinal location was illuminated with light of varying angles allowing for the measurement of individual photoreceptor pointing. At 30° nasal from the pecten tip, the pointing direction for both chicks was towards the pupil center with a narrow distribution. These particular chicks were found to have a temporal (T) and inferior (I) bias in the alignment with peak positions of (0.81 T, 0.23 I) and (0.57 T, 0.18 I) mm from the pupil center for chicks A and B respectively. The rho, ρ, values for the major, ρL, and minor, ρs, axes were 0.14 and 0.17mm(-2) for chick A and 0.09 and 0.20mm(-2) for chick B. The small disarray in the alignment of the chick photoreceptors implies that the photoreceptors are aligned to optimize the light entering the eye through the central portion of the pupil aperture. The ability to measure pointing properties of individual photoreceptors will have application in the study of eye growth and various retinal disorders.