Scleral Lens Sensor for Ocular Electrolyte Analysis

Abstract

The quantitative analysis of tear analytes in point‐of‐care settings can enable early diagnosis of ocular diseases. Here, a fluorescent scleral lens sensor is developed to quantitatively measure physiological levels of pH, Na+, K+, Ca2+, Mg2+, and Zn2+ ions. Benzenedicarboxylic acid, a pH probe, displays a sensitivity of 0.12 pH units within pH 7.0–8.0. Crown ether derivatives exhibit selectivity to Na+ and K+ ions within detection ranges of 0–100 and 0–50 mmol L−1, and selectivities of 15.6 and 8.1 mmol L−1, respectively. A 1,2 bis(o‐aminophenoxy)ethane‐N,N,‐N',N'‐tetraacetic‐acid‐based probe allows Ca2+ ion sensing with 0.02–0.05 mmol L−1 sensitivity within 0.50–1.25 mmol L−1 detection range. 5‐Oxazolecarboxylic acid senses Mg2+ ions, exhibiting a sensitivity of 0.10–0.44 mmol L−1 within the range of 0.5–0.8 mmol L−1. The N‐(2‐methoxyphenyl)iminodiacetate Zn2+ ion sensor has a sensitivity of 1 µmol L−1 within the range of 10–20 µmol L−1. The fluorescent sensors are subsequently multiplexed in the concavities of an engraved scleral lens. A handheld ophthalmic readout device comprising light‐emitting diodes (LEDs) and bandpass filters is fabricated to excite as well as read the scleral sensor. A smartphone camera application and an user interface are developed to deliver quantitative measurements with data deconvolution. The ophthalmic system enables the assessment of dry eye severity stages and the differentiation of its subtypes.

Ophthalmic sensing technologies for ocular disease diagnostics

“…44 Various indicators have been studied via contact lens sensors including pH, temperature, electrolytes, and IOP. 46,[49][50][51][52] However, tear fluid analysis has not been comprehensively studied. Tear film comprises of three layers: the lipid layer, aqueous layer, and mucous layer.…”

“…44 Contact lenses developed as smart devices for continuous monitoring in POC settings have received increasing attention recently, because outcome sensors can be powered externally and accompanied with wireless smartphone readouts. 44,[49][50][51] Although contact lenses offer convenience to users, there are disadvantages to their use. 59 One common complaint with contact lens use is a feeling of discomfort.…”

“…As the quantitative analysis of analytes in tear fluid is important for early ocular disease diagnosis in the POC platform, typical fluorescent scleral contact lens sensors were constructed to monitor physiological levels of pH, Na + , K + , Ca 2+ , Mg 2+ , and Zn 2+ ions. 100,151 They provided quantitative data on a smartphone readout. 100,151 One of the advantages of this type of contact lens sensor is its ability to assess the severity stages of dry eye disease and differentiate its subtypes.…”

Prospects for Additive Manufacturing in Contact Lens Devices

“…[ 15,16,98–101 ] Recently, smart CLs are extensively studied to continuously monitor vital signs from ocular conditions (e.g., dry eye, glaucoma) to monitor diseases such as diabetes [ 98,102–107 ] as well as physiological level of pH. [ 102,108 ] Figure shows examples of the smart CLs. Figure 10A shows the prototype of Google's electronic CL that may measure glucose in tears, and correct vision for individuals suffering from presbyopia.…”

Central-to-peripheral corneal edema during wear of embedded-component contact lenses

“…With the advance of micro-technology, the feasibility of fabricating embedded-circuit contact lenses is under active study to improve visual acuity, display augmented reality, or monitor health [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. However, introduction of various embedments within a contact lens introduces potential risk to ocular health as semiconductor-based embedments typically have low permeability to oxygen [7].…”