This prospective study found that the Ocular Surface Disease Index (OSDI) is a poor metric for ocular surface disease in glaucoma because the symptoms seem to be related largely to visual field loss.
Furthermore, the burden of topical IOP-lowering medication was strongly associated with the extent of corneal punctate epithelial erosions but not with tear film abnormality or tear production. These findings suggest that glaucoma medications do indeed damage the ocular surface but may not produce greater discomfort symptoms in patients on an established treatment regimen.
This emphasizes that we are poisoning the ocular surface with glaucoma meds and this can be compounded by the use of preserved perioperative meds.
The study’s authors examined 64 glaucoma subjects with bilateral visual field loss and 59 glaucoma suspects with normal visual fields. Tear film breakup time (TBUT), corneal staining score (0–15), and Schirmer's test results were included as objective metrics, whereas the OSDI questionnaire was administered to assess symptoms.
Seventy-five percent of glaucoma subjects and 41 percent of glaucoma suspects were receiving topical medications. The corneal staining grade was greater in glaucoma subjects than in glaucoma suspects (6.4 vs. 4.1; P < 0.001), but the groups did not differ with regard to TBUT or Schirmer's results (P > 0.20 for both).
Multivariate regression models showed that topical glaucoma therapy burden was associated with a significantly higher total corneal staining grade but not with TBUT or Schirmer's results (P > 0.20 for both). Glaucoma subjects had significantly higher total OSDI scores than glaucoma suspects (16.7 vs. 7.9; P < 0.001), largely due to the higher vision-related subscores in the glaucoma group (11.1 vs. 3.3; P < 0.001). Ocular discomfort–related subscores, however, were similar in both groups (5.7 vs. 4.6; P = 0.30).
In multivariate analyses, each 5-dB decrement in better-eye visual field mean deviation was associated with a 4.7-point increase in total OSDI score (95% CI, 1.9–7.5; P = 0.001) and a 3.7-point increase in the vision-related subscore (95% CI, 1.7–5.6; P < 0.001) but did not predict a higher discomfort-related subscore. Topical glaucoma therapy burden was not associated with higher total OSDI score or vision- or discomfort-related subscore (P > 0.20 for all).
They write that this study confirms the previously reported association between glaucoma eye drops and corneal staining, suggesting that medications, medical preservatives such as BAK, or both, are directly damaging the ocular surface. However, the authors note that these findings differ from studies using other objective methods to assess the ocular surface, such as those that found an association between topical IOP-lowering medication use and tear film measurements. Additionally, they did not observe a difference in ocular discomfort symptoms between glaucoma subjects and glaucoma suspects.
They also note that although the proportion of abnormal total OSDI scores in this study was similar to that of previous studies, the results indicate that this is an inaccurate estimate of the prevalence of ocular surface disease among the glaucoma population. The presence of comorbid disease potentially affecting functionality also was associated with the OSDI total score and the OSDI vision-related subscore, providing further evidence that the patient's overall health condition must be considered when interpreting the OSDI score.
They conclude that clinical tests, such as ocular surface staining scores, are more likely a better method of diagnosing ocular surface disease in patients with glaucoma than OSDI. Ocular surface staining should be performed routinely to minimize epithelial damage, therefore minimizing the risk of failure for future glaucoma interventions as well.