Lipid layer thickness and tear meniscus height measurements for the differential diagnosis of evaporative dry eye subtypes

AIM： To explore a new diagnostic index for differentiating the evaporative dry eye（EDE） subtypes by analysis of their respective clinical characteristics. METHODS： A cross-sectional study of 139 patients（139 eyes） with EDE who were enrolled and classified as obstructive meibomian gland dysfunction（MGD）（n=81） and non-obstructive MGD（n=58） EDE. All patients completed a Standard Patient Evaluation of Eye Dryness（SPEED） questionnaire and were evaluated for average lipid layer thickness（LLT）, tear meniscus height measurements（TMH）, tear break-up time（TBUT）, ocular surface staining score, Schirmer I test（SIT）, lid margin abnormalities, and meibomian gland function and morphology. RESULTS： Age, average LLT, TMH, scores of lid margin abnormalities, meibum quality, meibomian gland loss（MGL）（all P≤0.001）, and TBUT（P=0.03） were all significantly different between obstructive MGD EDE patients and nonobstructive MGD EDE patients. Average LLT in obstructive MGD EDE was correlated with meibomian expressibility（r=-0.541, P≤0.001）, lid margin abnormalities were marginally not significant（r=0.197, P=0.077）, and TMH was correlated with MGL（total MGL： r=0.552, P≤0.001; upper MGL： r=0.438, P≤0.001; lower MGL： r=0.407, P≤0.001）. Average LLT in non-obstructive MGD EDE, was correlated with meibomian expressibility and Oxford staining（r=-0.396, P=0.002; r=-0.461, P≤0.001）. The efficiency of combining average LLT and TMH was optimal, with a sensitivity of 80.2% and a specificity of 74.1%. Obstructive MGD EDE patients had an average LLT≥69 nm and TMH≥0.25 mm, while non-obstructive MGD EDE patients had an average LLT〈69 nm and TMH〈0.25 mm.CONCLUSION： Obstructive MGD EDE and nonobstructive MGD EDE have significantly different clinical characteristics. Combining average LLT and TMH measurements enhanced their reliability for differentiating these two subtypes and provided guidance for offering more precise treatments for EDE subtypes.

Low concentration of sodium hyaluronate temporarily elevates the tear film lipid layer thickness in dry eye patients with lipid deficiency

AIM： To investigate the effects of different concentrations of artificial tears on lipid layer thickness （LLT） and blink rate （BR） in dry eye patients. METHODS： This study included 106 eyes of 58 patients with dry eye. The lipid deficiency type was defined as the LLT baseline 〈75 nm. The LLT and BR were measured at baseline and 1, 5 and 15min after the instillation of 0.1% or 0.3% sodium hyaluronate （SH） eye drops by using the LipiView ocular surface interferometer. RESULTS： In the lipid deficiency group, the LLT increased from baseline at 1rain post instillation. The LLT after the instillation of 0.1% SH was significantly higher than that after the instillation of 0.3% SH （P〈0.001）. The LLT returned to baseline at 15min post instillation of 0.1% SH and at 5min post instillation of 0.3% SH. In the non-lipid deficiency group, the LLT decreased from baseline at lmin and returned to baseline at 5rain for both treatments. The BRs were not significantly different at different time points for both treatments. CONCLUSION： SH eye drops induce a short-term increase in LLT of patients with lipid deficiency. A low concentration of artificial tears have a stronger effect than a high concentration of artificial tears on the increase in LLT. in comparison, SH eye drops induce a transient and slight decrease in LLT of patients without lipid deficiency. A low concentration of artificial tears might be better for patients with lipid deficiency.