Eyeworld

EW CORNEA 41 But clinical judgment is still necessary to assess which subtype and overall severity O ne major obstacle for those who treat people with dry eye has been a lack of correlation be- tween patient-reported symptoms and traditional clinical signs such as Schirmer's test, tear break-up times (TBUT), or conjuncti- val/corneal staining. Further compli- cating matters, the underlying mechanisms of the disease "are be- yond the scope of clinical observa- tion, with androgen deficiency, hyperosmolarity, inflammation, lipid composition, and tear film in- stability playing definitive roles in the initiation and/or progression of the disease," according to a recent paper. 1 As such, it is completely within the realm of possibility that someone with a low Schirmer's test score might have a stable tear film, said Ben Sullivan, Ph.D., chief sci- ence officer and co-founder, TearLab, San Diego, Calif. "We've known for a long time that dry eye signs and symptoms don't correlate except in cases of advanced disease," said Kelly K. Nichols, O.D., M.P.H., Ph.D., associ- ate professor of optometry, The Ohio State University College of Optome- try, Columbus. "It's easy to clarify the symptoms when there's a chief complaint. It's much more difficult with an asymptomatic patient." Tear film osmolarity is "believed to be a global indicator of the dis- ease," Dr. Sullivan said. "Knowing the osmolarity is useful, and tests to measure it should be used as an ad- junct to others already in a physi- cian's armamentarium." Study details A recent study on tear film osmolar- ity 1 found it to be the "single best marker of disease severity across nor- mal, mild/moderate and severe cate- gories" of dry eye. In this study, 299 patients (ranging in age from 18 years old to 82 years old; 218 were fe- male) were analyzed from a general patient population from 10 clinical sites in the U.S. and Europe. The tear film osmolarity test, Schirmer's test without anesthesia, TBUT, corneal staining, meibomian dysfunction as- sessment, and conjunctival staining were performed bilaterally. A symp- tom questionnaire (Ocular Surface Disease Index) was also recorded for each patient. Distributions of clinical signs and symptoms against a contin- uous, composite severity index were evaluated. Osmolarity was measured using a lab-on-a-chip to simultaneously collect and analyze the electrical im- pedance of a 50-nanoliter tear sam- ple from the inferior lateral meniscus (TearLab Osmolarity Sys- tem). For this study, dry eye classifi- cation was based on a series of thresholds, without weighing the severity of each sign. "Normal" subjects had disease severities from 0.1 to 0.203; mild-to- moderate subjects had disease severities from 0.204 to 0.664. Interestingly, Dr. Sullivan said, even those patients deemed "normal" had at least some evidence of dry eye in at least one clinical measure. "No one registered a 0," he said. "Likewise, even the most severe pa- tients were not at the upper limits of each of the measures either." Tear osmolarity "was the only sign that exhibited meaningful cor- relation" across the three severity markers, Dr. Sullivan said. "Tear os- molarity should not replace other tests, it should augment them," he said. Still not there Although tear osmolarity shows great promise in determining who has dry eye, "it's not going to tell the diagnostician what kind of dry eye the person has or if it's meibo- mian gland dysfunction or lid mar- gin disease," Dr. Sullivan said. Dr. Nichols expects clinicians to embrace the technology, as "it's an objective test and it's easy to per- form. Once there's reimbursement by Michelle Dalton EyeWorld Contributing Editor Tear film osmolarity "single best" dry eye marker that cataract surgery can sometimes make the condition worse." EW Editors' note: The doctors mentioned have no financial interests related to their comments. Contact information Koch: douglaskoch@mac.com Lee: lee0003@aol.com Cataract continued from page 40 continued on page 42 October 2011 Image and caption in production The TearLab osmolarity instruction guide for physicians Source: TearLab TEARLAB ™ COLLECTION GUIDE 1"5*&/513&1"3"5*0/ A *'$0--&$5*0/*4%*''*$6-5 ' $0--&$5*0/5&$)/*26& $ % E 4".1-&$0--&$5*0/ B '03.03&*/'03."5*0/1-&"4&$0/5"$55FBS-BC$PSQ4BO%JFHP$"64"JOGP!UFBSMBCDPNXXXUFBSMBCDPN ¥5FBS-BC$PSQ 3&7% 0OFPSNPSFPGUIFGPMMPXJOHQBUFOUTNBZBQQMZ 641BUJFOUT '%" L $MFBSFE L /"4%"25&"3 5495-# A 3 " 1 & 3 1 5 / & * 5 " 1 F Z F F I U N P S G Z B X B 0 / P % 5 / " 5 3 0 1 . * t D F I U T E S B X P U E S B X Q V E B F I I U J X U O F J U B Q U B F 4 r / E 0 * 5 " 3 J M F I U H O J W P N E J M F Z F F I U M M V Q 5 0 " H O J M J F D T F Z F E O B L D B C E B ó J E O P J U D F M M P D F L B N F I U L B F S C M M J X O X P E Z Z $ & - - 0 $ & - 1 . " 4 T F Z F S J F I U O F Q P P U F D B M Q P U O J O F 1 F W P . r U M V D ó E O B F L B M S B F U F H / U 0 * 5 $ O F J U B Q L T B O F I U $ % $ & 5 / 0 * 5 $ & - - 0 $ E J M F Z F S F O O J F I U H O P M B M F I U E O B E J M F Z F S F X P M D P U O J F N P D P U Q J U F I U O J X P M M B O F 1 F I U S F X P - r & 6 2 * / ) $ # O J H S B N E F S V U T J P N G P F O J F I U I U J X U D B U O P D G P N P U U P C F I U H O ' E S B D U T F U F I U I U U B E F U D F M M P D T J E J V M ' r & T S B F U U D F M M P D O P Z M U I H J M O X P E T T F S 1 r X F I U H O J I D V P U E J P W " r F I U G P S F O S P D F I U S B F O E O P Z F C Q J U F I U F W P . r G P Q J U N P U U P C F I P U E J M F Z F F I U F Z F F I U G P F U J I X % $ F Z F F T F I T B M F Z F F I U ' * F / 0 * 5 $ & - - 0 $ ' * S F I X F T B D F S B S F I U O * r E S S F U V P F I U H O P M B O F 1 F I U I T V S C Z M U I H J - r Q U P O P E Z M F U B J E F N N J I H V P O F U P O T J F S F I U G * r L O J M C P U U O F J U B Q X P M M " r H O J U D F M M P D O F I X V Q E J P W B P U F S V T F L B . r 5 U - 6 $ * ' ' * % 4 O T J U T V K F S F I U F ' E J M F I U G P I U S P GP E O B L D B C L D F Q U D F M M P D P U S B F U Z M M B N S P O L E J M F I U O X P E H O J M M V 5 / L E F S B F M $ " % ' 1 / 0 * 5 " . 3 0 ' / * & 3 0 . 3 0 ' # - 5 9 4 5 3 " & 5 2 " % 4 " / T U O F J U B 1 4 6 B Q H O J X P M M F I U G P F S P N S P F O 0 % O B 4 Q S P $ C B - S B F 5 5 $ " 5 / 0 $ & 4 " & - 1 Z M Q Q B Z B N T U O F U B % 7 & 3 B - S B F 5 ¥ U ! O J " 4 6 " $ P H F J % % N S P S S F F H O B 3 X P M F # B V T F I U O P S B F U I H V P O F C Q S P $ C N P D C B M S B F U X X X N P D B M S B F U U M V T F S Z B N F Z F F I U G P F D B GB S V 40-45 Cornea_EW October 2011-dl2_Layout 1 9/29/11 3:43 PM Page 41

• Cover