eyes.nhs.scot

• 1.1 Basal Cell Carcinoma, Periocular
• 1.2 Blepharitis, Anterior and Posterior
• 1.3 Chalazion (Meibomian Cyst)
• 1.4 Dermatochalasis
• 1.5 Ectropion
• 1.6 Entropion
• 1.7 Facial Palsy (Bell's Palsy)
• 1.8 Hordeolum (Stye)
• 1.9 Horner’s Syndrome (Oculosympathetic Palsy)
• 1.10 Molluscum Contagiosum
• 1.11 Ocular Rosacea
• 1.12 Penetrating Injury, Eyelid
• 1.13 Phthiriasis (Pediculosis Ciliaris/Crabs)
• 1.14 Ptosis, Involutional
• 1.15 Third Nerve Palsy, Ptosis
• 1.16 Trichiasis

1.13 Phthiriasis (Pediculosis Ciliaris/Crabs)

Date of last review:

22/6/2026

Date of next review:

22/6/2028

Date of publication:

17/8/2026

Differential diagnosis ⁽¹⁾

• Blepharitis (anterior)  

  • nits may be confused with lash debris  

  • Demodex mites are much smaller than crab lice (0.1–0.4mm long) and are not usually seen outside the lash follicle  

• Allergic or infective conjunctivitis  

• Eczema affecting lid skin  

Possible management by Optometrist

Advice ⁽¹⁾

• Sensitive counselling is essential, as this condition is usually sexually transmitted  

• Be alert to safeguarding concerns, particularly in children  

• Advise good personal hygiene (e.g. handwashing after contact with pubic region)  

• Ask about symptoms of pubic infestation  

• Sexual partners or close family members should have an eye examination and treated if required  

• Bed linen, towels, and clothing should be washed at ≥60 °C for at least 5 minutes  

Treatment

• Manual removal of lice, nits, and casts at the slit lamp using fine forceps ⁽¹⁾  

  • Lice adhere firmly to lashes; removal may be challenging  

• Repeat removal may be required every few days ⁽¹⁾  

• Arrange follow-up to confirm eradication ⁽¹⁾  

• Unmedicated paraffin-based eye ointment ⁽¹⁾  (e.g. Hylo-night, Xailin night)⁽⁷⁾. Refer to local formularies for suitable options ⁽⁶⁾   

  • Applied to lid margins twice daily for at least 2 weeks ⁽¹⁾  

  • Acts by suffocating lice and preventing nits from hatching  

• If available Permethrin 1% lotion applied carefully to lashes for 10 minutes with eyes closed, then rinsed ⁽¹⁾, otherwise refer to local formularies for suitable alternatives ⁽⁷⁾

  • Must only be performed by experienced practitioners  

  • Extreme care required to avoid corneal contact  

  • Residual product should be gently removed from lid margins after treatment  (e.g. with a dry cotton bud)  

N.B. Insecticides are potentially toxic to the ocular surface and should not be used unsupervised ⁽¹⁾  

In cases of known sensitivities, please consult local formularies for alternative options ⁽⁷⁾.  

Typical dosage/duration

(Blue text = IP, black text = non-IP)

• Not applicable for this condition ⁽⁷⁾  

Further management options  

• Treatment may be provided within available locally enhanced schemes, or by community IP optometrists/OMPs, as appropriate ⁽⁷⁾  

• Refer via GP ⁽¹⁾ for :  

  • Management of non-ocular infestation  

  • Contact tracing  

  • Screening for other sexually transmitted infections  

• Discuss referral to local sexual health services where appropriate ⁽¹⁾  

• Follow local safeguarding procedures where abuse or neglect is suspected ⁽¹⁾  

  • National child protection guidance - Child protection - gov.scot⁽⁷⁾ 

Possible management in secondary care or local/community pathways where available  

• See Further management options ⁽⁷⁾  

• Normally no referral required ⁽¹⁾  

College of Optometrists Clinical Management Guideline⁽¹⁾   

Phthiriasis palpebrarum (pediculosis ciliaris) - College of Optometrists * 

*With special thanks to The College of Optometrists for providing the evidence framework for diagnosis and management from the Clinical Management Guidelines (CMGs) for this condition. All references to the College/CMGs are included where appropriate and form the basis of the Community Eyecare Guidelines.  

Guidance is informed by the following sources   

1. College of Optometrists Clinical Management Guidelines Clinical Management Guidelines - College of Optometrists   

2. Advisory alignment with the College of Optometrists Formulary Optometrists' Formulary - College of Optometrists   

3. Advisory alignment with the BNF BNF (British National Formulary) | NICE  

4. Advisory alignment with the Summary Product Characteristics taken from the EMC Home - electronic medicines compendium (emc)  

5. Advisory alignment with Scottish Health Board formularies (where a clear majority is present) *  

6. Advisory alignment with expert consensus (CEGG), informed by sources 2-5 above  

7. Advisory alignment with expert consensus (CEGG)   

8. “Annex C of the Statement” https://www.eyes.nhs.scot/for-professionals/legislation/   

* Scottish formularies should be available within the Prescribing section of your Health Board pages on the eyes.nhs.scot website. If unavailable, contact your local Health Board for further information; Health Boards landing page   

If you have a query relating to this page, please email NSS.ComEyecareGuidelineGroup@nhs.scot