Aakanksha Pathania, B. Optom

Consultant Optometrist, Sharp Sight Eye Hospital, New Delhi, India

Optometrists are the primary eye health care provider who examines the eyesight of the patient, prescribes spectacles, contact lenses, and diagnose any ocular anomalies. With new development, optometrist plays a very important role in other fields also such as in forensic.

Forensic optometry is one such field which examines and analyses the evidence such as spectacles and other eyewear relating to crime scenes that can assist in the investigation and prosecution of criminals of crime or save an innocent person from suspicion.⁽¹⁾

One of the major changes that occur in the body after death is corneal clouding which starts approximately after 2 hours from death.⁽²⁾ Similarly, after death, blood cells in the body breaks down and releases potassium at a slower and more predictable rate, is also unaffected by temperature in the eye.⁽²⁾ Thus, examining the potassium level in the vitreous humour can also help to calculate an approximate time of death.

Figure 1: Corneal clouding after death
Image courtesy : https://www.researchgate.net/publication/342374577_Postortem_Iris_Decomposition_and_its_Dynamics_in_Morgue_Conditions/figures?lo=1&utm_source=google&utm_medium=organic

Figure 2: Traumatic conjunctival hemorrhages
Image courtesy: : https://eyerounds.org/atlas/photos/burHem.jpg

Conjunctivae and eyelids are examined for pinpoint-sized petechial haemorrhages.⁽²⁾ Increase in the hydrostatic pressure in the capillaries leads to such haemorrhages. These are suggestive of any kind of strangulation and homicide.

Human tears carry a lot of information about individual behavioural changes; it is quite helpful for the personal identification of an individual. A small number of tears could be found in cloths or tissue paper in dry deposited state which helps in DNA profiling for personal identification.⁽³⁾

Optometrists can offer expertise and examine the culprit for drugs and alcohol use. Horizontal gaze nystagmus testing is done to check for excessive use of drug or alcohol consumption. ⁽⁴⁾ The culprit’s lack of smooth and pursuit movement, as well as onset of nystagmus before 45 degrees, are all indication of alcohol or drugs consumption. If nystagmus occurs closer to the nose, the blood alcohol content will be higher.⁽⁴⁾

Figure 3: Horizontal gaze nystagmus Test during investigation
Image courtesy : https://www.ncdd.com/403.shtml

Pupil evaluation also holds important clues during primary investigation. People consuming narcotics will have miotic pupil. Pupils that react slowly with change in intensity of light may be due to psychedelic drugs. Rebound pupil is seen in people consuming cannabis.⁽⁵⁾

Each eyewear such as spectacles and contact lenses has unique properties, and their prescription can provide vital clues in understanding the visual ability of an individual. Eyewear increases the potency of clue in any identification case.⁽⁶⁾ Evidence found on spectacles and contact lenses like tears, and fingerprints can strengthen the evidentiary value.

Additionally, identification of an individual can be done by carefully observing certain unique eye characteristics such as heterochromia which is very rare in a group of population. ⁽⁶⁾ Biometric authentication of iris utilizes pattern and image recognition technologies to distinguish characteristics of a person’s eye.⁽⁶⁾ Its goal is to provide a near-instant, accurate recognition process of a person’s identity based on the digitally scanned image retrieved from each person.⁽⁶⁾ In many countries iris scanning is done for everyone by the government for records which can be used for identification during any investigation.

Figure 4: Iris scanning during investigation
Image courtesy: https://biometric-iris-recognition-for-healthcare

In the eye care field, forensic optometry is not explored properly yet, but it can be very useful by the investigator during any law enforcement case and many mysteries can be solved successfully.

References:

1. Iorliam, A. (2018). Subdivisions of Forensic Science. In Fundamental Computing Forensics for Africa (pp. 17-56). Springer, Cham.
2. Murphy, J. (2004). CS eye: how the eye is used in forensic medicine, and how you can help detect and prevent crimes. Review of Optometry, 141(11), 78-82.
3. Aparna, R. S. I. R., & Iyer, R. S. (2020). Tears and eyewear in forensic investigation—A review. Forensic science international, 306, 110055.
4. Bertolli, E. R., Forkiotis, C. J., Pannone, D. R., & Dawkins, H. (2007). A Behavioral Optometry/Vision Science Perspective on the Horizontal Gaze Nystagmus Exam for DUI Enforcement. Forensic Examiner, 16(1).
5. Bertolli, E. R., Forkiotis, C. J., Pannone, D. R., & Dawkins, H. (2004). Eye detector: an introduction to drug detection skills; By knowing the ocular signs of drug abuse, you may discover that a patient has a substance abuse problem. Review of Optometry, 141(1), 62-71.
6. Bertolli, R., Berg, G. E., & Pannone, R. (2012). VISION SCIENCE IDENTIFICATION OVERVIEW. Forensic Examiner, 22(1).