Tear Layer Lipid Thickness in Pterygium Patient Before and After Surgery
Condition: Dry Eye
MeSH terms: Pterygium
Study type: Observational

Summary: 
      The investigators study aims to capture the objective effects of pterygium surgery on tear
      layer lipid thickness and the tear layer.

      Previous objective studies of the tear film has been limited to corneal staining grading,
      tear break up time and Schirmer's test which have been shown to poor to moderate
      repeatability. The effect of pterygiums on tear layer lipid thickness (LLT) has not
      previously been explored. With the LipiView Ocular Surface Interferometer, the investigators
      have the ability to assess the optical coherence interference pattern produced by light
      reflected off the tear film in a safe and non-invasive manner. Software analysis of the image
      then measures the tear LLT which can be used to objectively quantify the diagnosis of
      lipid-deficient dry eye.
    

Detailed description: 
      Pterygium is a condition characterized by abnormal conjunctival growth on the cornea and is
      particularly prevalent in tropical climates. In severe circumstances, it may lead to visual
      loss by obscuration of the visual axis and inducing corneal astigmatism (1). It is often also
      associated with dry eye symptoms and studies have previously shown some correlation with
      shortened tear break up time (TBUT)(2) but not Schirmer's Test (3).

      Schirmer's Test, corneal staining and TBUT are often used to investigate symptoms of dry eyes
      but the diagnosis and assessment is often difficult due to the poor repeatability of the
      tests(4). Treatments for dry eyes often rely on patient's subjective symptomatic improvements
      as a measure of outcome although no literature has been published of subjective symptoms for
      pterygium patients. The effects of pterygium surgery and tear lipid layer thickness has also
      not been studied.

      The LipiView Ocular Surface Interferometer is a HSA-approved imaging device that allows
      clinicians evaluate the characteristics and thickness of the tear lipid layer thickness (LLT)
      in a safe and non-invasive manner. The device utilizes white light from a LED source that is
      directed at the tear film over the inferior corneal region. Reflected light is captured by a
      high resolution camera and the optical inference pattern is evaluated by software to
      determine the LLT (5). It also was found to correlate with other dry eye diagnostic tests,
      such as tear film break-up time (TBUT), Schirmer's test and corneal staining(6,7). LLT is
      also reported to better correlate with symptoms than other objective dry eye tests(5).

      LipiView was also capable of detecting a significant change in longitudinal lipid thickness
      in 10 patients one month after blepharoplasty. A similar result may be obtained from the
      investigators patients post pterygium surgery.

      This current study aims to investigate the effects of pterygium surgery on tear lipid layer
      thickness with LipiView. The results will be compared with the effects of pterygium surgery
      on TBUT, and corneal staining. The subjective improvement in dry eye symptoms post pterygium
      surgery will also be studied.

      Clinical importance This study can provide further data to support pterygium surgery as a
      role in dry eyes management in an objective and reproducible manner. New data on pterygium
      and tear lipid layer thickness as well as subjective dry eye symptoms will also be explored.

      Study Objectives and Purpose The Assesssment of Dry Eye Symptoms, Tear Layer and Tear Layer
      Lipid Thickness Pre and 1month Post Pterygium Surgery using a LipiView Ocular Surface
      Interferometer (LipiView)

      Study design:

      Prospective study

      Rationale:

      Methods:

      Participants and target sample size Target sample size: 80 40 patients who will be undergoing
      pterygium surgery will be recruited for this study. Another 40 patients will be recruited
      from the general ophthalmology (ECS) clinic. These patients are cleared to have no lid
      disturbances in terms of function or anatomy, and will serve as the "control" group.

      Permission will be sought from the junior ophthalmologists and the supervising
      ophthalmologist (in the event of a training list) or from the senior ophthalmologist if he is
      performing the surgery himself. These patients would have been diagnosed with pterygium and
      opted for surgical excision and conjunctival autograft. Pre operatively they will complete a
      simple questionnaire to evaluate any dry eye symptoms. Participants will be examined under
      the slit lamp for fluorescein dye corneal staining and fluorescein dye tear break up time.
      The patients will then undergo a LipiView Ocular Surface Interferometer Measurement of Tear
      lipid layer thickness.

      Visit schedules Two/Three visits is required for paticipants who are undergoing pterygium
      surgery.

      Only one visit is required for normal controls who are recruited from general ophthalmology
      (ECS) clinic.

      Duration of study:

      10 months.

      Procedures:

        1. Assessment of Dry Eye Symptoms (SANDE) Participants will be asked to score and fill up a
           dry eye questionnaire that assesses the symptomatic severity and frequency of dry eyes
           symptoms.

           • SANDE Questionnaire Consists of 3 questions on frequency and severity. VAS will be
           applied to evaluate dry eye symptoms as described by Schaumberg et al. (Schaumberg,
           Gulati et al. 2007). The scores will be recorded separately for frequency and severity
           of dry eye symptoms. Patients will be asked to mark "X" on a 100mm line that corresponds
           to the degree of the symptom. A global score will be calculated by multiplying the
           frequency score by the severity score and taking the square root of the result (to
           transform back to the original scale).

           Basic biodata such as age, race, gender will also be recorded.

        2. LipiView Ocular Surface Interferometer Measurement of Tear lipid Layer Thickness

           Prior measuring the tear lipid layer thickness, participants are advised not to:

           i. instill any eye ointment for at least 24 hours, or ii. instill eye drops or wear
           contact lenses for 4 hours, or iii. swim in a chlorinated pool, rub their eyes or put on
           eye cosmetics on the day of the measurement.

           During the measurement of each eye, the participants place their chins on a chin rest
           and look at a single white light source for 30 seconds. During this period, participants
           are encouraged to blink freely at a comfortable rate which the assessor measures the
           LLT.

           Similar steps would be taken for the other eye as a control eye.

           Assessment of fluorescein tear break up time and corneal staining will be conducted only
           after LipiView LLT measurement.

        3. Fluorescein Dye Tear Break-up Time (TBUT) Fluorescein dye is introduced onto the lower
           eyelid by a wetted fluorescein strip. The tear film will then be observed with blue
           light using a slit lamp to the point where it breaks. The time from the previous blink
           to the breaking of the tear film will be recorded to the nearest second.

        4. Fluorescein Dye Corneal Staining After fluorescein dye is introduced, the cornea will be
           examined for green stains indicating epithelial erosion, a sign of damage due to
           dryness. The number of green stains and their location on the cornea (superior, central,
           inferior, temporal, nasal fields) will be recorded.

        5. Patient will undergo pterygium excision and conjunctival autograft on the prearranged
           surgery date.

        6. Steps 1-4 will be repeated 1 month post operatively.

      Outcomes:

      Primary outcome:

      An increase in tear lipid layer thickness 1 month post pterygium surgery in the operated eye.

      Statistics:

      There will be no interim analysis. Analysis will be performed after all the subjects have
      completed the required visits or have withdrawn from the study.

      Data will be analysed for sample mean of pre and post-operative questionnaire score, tear
      break up time, corneal staining and tear lipid layer thickness in both the operated and
      un-operated eye. The confidence intervals of the pre and post-operative in both the operated
      and un-operated will be calculated with T-test analysis.

      Expected outcomes:

      There should be decreased dry eye symptoms in the operated pterygium eye with a improvement
      in tear break up time, decreased corneal staining and increase tear lipid layer thickness
      when compared to pre operative.

      Potential problems No potential problems are expected for this study.

      Inclusion Criteria

      1. Normal controls or patients with pterygium who have consented for pterygium surgery and
      are willing to participate in this study

      Exclusion Criteria

        1. Active ocular surface conditions such as infections.

        2. Any other specified reason as determined by clinical investigator.
    

Observational model: Case-Control
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Healthy normal volunteers and Pterygium patients undergoing surgery to remove Pterygium
      
Keywords: Tear Lipid Thickness; Pterygium surgery