Eye Bank: Tissue Storage and some MCQs

Know About Tissue Storage Media in Eye Banking

After tissues (cornea or sclera) is retrieved from the dead body, eye bank can store them in four different preserving media as mentioned below.

    1.    Very Long Term: slcera can be preserved for over 1-2 years in 70% ethanol (ethyl alcohol solution) or glycerine. Cryopreservation: tissue can be indefinitely preserved in a liquid nitrogen tank at -160 degrees. In one of variations of this method frozen ocular tissues are stored in the presence of cryoprotectants like methyl-sulphoxide.

     2.    Long Term: In the temperature of +28 to + 37 degree Celsius, cornea and sclera can be stored in Organ Culture Medium for up to 1 month. This method is very good in that we can see the physiological response of donor cornea in the culture flask before we graft it to patients. Hence, this greatly reduces the primary graft failure because if the cornea does not demonstrate adequate physiological response, then we can discard the tissue or explain the patient about the prognosis prior to the surgery..

     3.    Medium Term: This offers around 1-2 weeks of preservation time at 2-8 degrees of temperature. Also called as cold-storage system or Hypothermia Method.
     A) Cornisol: manufactured and marketed by Aurolab, Madurai, contains mucopolysaccarides as nutrient and steptromicin and gentamicin as antibiotic. Maximum time for tissue preservation in Cornisol is 14 days.  
   B) Optisol-GS: Manufactured and marketed by Chiron Ophthalmics, California, contains 2.5% Chondroitin Sulphate and 1% dextran. The recommended safe period for tissue storage in Optisol-Gs is 7-10 days. 
   C) New one is Life4C by Numedis Inc, Minnesota, which has similar performances with Optisol-GS, even though Life4C contains added  glutathione and human insulin.

     4.    Short-term: Few days of tissue storage (1-4 days)

       A) McCarey and Kaufmann (M-K) medium at 4 degrees for up to 4 days. It contains TC-199 culture medium with 5% dextran and no Chondriotin Sulphate. Chondroitin Sulphate and Dextran are used as anti-stromal swelling agents (hyperosmotics).

    B) Moist chamber: when the whole eyeball is enucleated, then the technician stores the eyeball in a tray with moist chamber with the half of eyeball immersed in sterile normal saline. In moist chamber, tissue can be kept not more than 2 days at room temperature. Typically, moist chamber storage medium is used as a transport medium from the time of tissue retrieval to tissue processing.

  In whatever media is cornea stored, it should be kept at room temperature for one day prior to the day of transplant.  
         

  See below to go briefly through the common multiple choice questions for Nepal.

Eye Bank Questions:

1. The first surgeon who performed the penetrating keratoplasty in Nepal is

a)        Dr. Dev Narayan Shah

b)       Dr. Madan Prasad Upadhyaya

c)        Dr. ND Joshi

d)       Dr. PC karmacharya

2. Nepal Eye bank was established in

a)        1981

b)       1994

c)        1999

d)       2001

3. Endothelial decompensation occurs if endothelial cell density is below

a)        2000/mm sq

b)       1000 mm sq

c)        500 /mm sq

d)       250/ mm sq

4. coefficient of variation in specular microscopy measures which of the following endothelial attributes:

a)        Polymegathism

b)       Blebs

c)        Pleomorphism

d)       Guttata

5. Hospital Cornea Retrieval Program from Nepal Eye Bank was started in

a)        2008

b)       2011

c)        2013

d)       2015

6. Enormous corneal sensitivity is due to the thousands of nerves entering into the cornea. The number of nociceptors approximate to

a)        5500 /mm sq

b)       7000 /mm sq

c)        10,000 /mm sq

d)       15, 000/ mmsq

7. Which one is not a contraindication for donor tissue

a)        Hepatitis B and C

b)       HIV

c)        Lung Cancer

d)       Syphilis

8. One of the following seems the most feasible age criteria to be a cornea donor (death at:)

a)        Birth-100 years

b)       2 years - 80 years

c)        5 years - 70 years

d)       10 years - 50 years

9. Prior to tissue retrieval the technician should wash the anterior ocular surface by sterile phosphate buffered saline followed by 3 minutes rinsing of povidone iodine solution whose percentage should be

a)        2%

b)       5%

c)        10%

d)       12%

10. The tissue would not be worth for optical transplantation if the endothelial count is below

a)        2000 / sq mm

b)       1500 sq mm

c)        1000 sq mm

d)       2500 sq mm

11. McCarey-Kaufman medium is a storage media where we can store the corneal tissue for upto

a)        3-4 days

b)       7-8 days

c)        14-15 days

d)       29-30 days

12. Optisol cornea storage media is enriched with

a)        Mucopolysaccharides and gentamicin

b)       Chondroitin sulfate and dextran

c)        Glucose and benzalkonium chloride

d)       Sucrose and streptomicin

13. Hypothermic storage modality of donated tissue the chamber temperature is maintained at

a)        Below 0 degree Celsius

b)       2 to 8 degree Celsius

c)        1 to 15 degree Celsius

d)        -10 degree Celsius

14. DSAEK, a type of corneal lamellar graft, stands for

a)        Descement Stripping Automated Epithelial Keratoplasty

b)       Descement Stripping Automated Endothelial Keratoplasty

c)        Directly Stimulated Alloplastic Endothelial Keratoplasty

d)       Direct Stromal Automated Epi Keratoplasty

15. If a cornea retrieved from a crematorium disqualifies for optical transplant in that the polymegathism is 80% of total endothelial. We can do all of the following to this tissue except

a)        use for tectonic graft

b)       use for therapeutic purpose

c)        use for research and training

d)       discard it in a safe place

16.  When the whole eye ball is enucleated, we can also preserve the severed sclera in 90% ethanol after processing. The preservation period  during which it is accepted for surgical procedures

a)        15 days

b)       30 days

c)        6 months

d)       2 years

17. The poor candidate for eye donation

a)        Old age

b)       Bilateral cataract surgery

c)        Suspected social behavior

d)       All

18. The first human corneal graft was done in 1886 by

a)        Edward Konrad

b)       Von Hippel

c)        Ludwig Rehn

d)       Ebers Papyrus

19. Event of graft rejection can occur in the recipient in

a)        6 months

b)       1 years

c)        2 years

d)       Throughout life

20. Which disease warrants an excellent prognosis in penetrating keratoplasty?

a)        Keratocounus

b)       Inactive herpetic scars

c)        Keratoglobus

d)       Severe dry eyes

21. Hospital Cornea Retrieval Program (HCRP) in Nepal was started in:
 a) 2013
 b) 1991
 c) 1994
 d) 1999

NB: Absolute contraindication of donor tissue for corneal transplant has a pneumonics called REDHATSs. ( If donor has any of the following known conditions, his/her eyes are not suitable for transplant)
R = Rabies
E = Encephalitis
D = Death from unknown cause
H =Hepatitis B & C
A = AIDS
T = Tuberculosis (miliary)
S = Syphilis
S = Septicemia


Answers:

1c 2b 3c 4c 5c 6b 7c 8b (Nepal Eye Bank[NEB] follows: 2 years- 75 years) 9b

10a (NEB follows <1800) 11a 12b 13b 14b 15d 16d 17d 18b 19d 20a 21a