Assessment of Low Vision Patients

Definitions & Goals - Seeing the Challenge

• Low Vision (as per NPCB, India):
  • Visual Acuity (VA): >3/60 up to 6/18 (better eye, best correction).
  • Visual Field (VF): <40° to >10° around central fixation.
• Blindness (as per NPCB, India):
  • VA: ≤3/60 (better eye, best correction).
  • VF: ≤10° around central fixation.
• Goals of LVA & Rehabilitation:
  • Maximize use of residual vision.
  • Enhance functional ability, independence.
  • Improve Quality of Life (QoL).

⭐ For NEET PG, remember NPCB (India) criteria: Blindness includes VA ≤3/60 or VF ≤10°.

Patient History - Uncovering Needs

• Goal: Uncover patient's specific needs, functional limitations, and clear rehabilitation goals.
• Key Areas (📌 Mnemonic: FOCUS):
  • Functional Impact: ADL/IADL difficulties (e.g., reading, mobility, self-care), work, hobbies.
  • Ocular Details: Diagnosis, onset, duration, progression of vision loss; key symptoms (blur, scotoma, glare); LVAs used & effectiveness.
  • Chief Complaint & Goals: Patient's primary concerns; specific, desired activities post-rehab.
  • Understanding & Expectations: Patient's knowledge of their condition; psychosocial impact; realistic rehab goals.
  • Systemic Health & Social Context: Relevant co-morbidities (DM, HTN); medications; social support, living situation, occupation.

⭐ Eliciting patient-specific, realistic goals is crucial for tailoring rehabilitation and ensuring patient motivation and satisfaction.

Visual Function Tests I - Quantifying Sight

• Visual Acuity (VA): Measures detail. Distances: 6m (Snellen), 4m (ETDRS).
  • LogMAR: For low vision. $LogMAR = Log_{10}(MAR)$. 1.0 = 6/60.

⭐ LogMAR Advantage: ETDRS charts: superior accuracy in low vision via uniform letters, consistent spacing, log progression; crucial for monitoring.

• Beyond Charts: Counting Fingers (CF), Hand Movements (HM), Light Perception (LP).

Visual Function Tests II - Beyond Acuity

• Visual Field Assessment:
  • Confrontation Test: Gross peripheral field screening.
  • Amsler Grid: Central 10-20° (macula); detects scotomas, metamorphopsia.
  • Perimetry (Humphrey, Goldmann): Detailed mapping for glaucoma, neuro-lesions, and monitoring progression.
• Contrast Sensitivity:
  • Pelli-Robson, Mars charts: Quantifies ability to discern subtle shade differences.
  • Reduced in cataract, glaucoma, diabetic retinopathy; impacts daily tasks like night driving, reading, recognizing faces.
• Color Vision:
  • Ishihara Plates: Rapid screening for congenital red-green deficiencies.
  • Farnsworth D-15: Arranges colored caps; classifies defect type/severity (e.g., protan, deutan, tritan).
• Glare Testing & Disability Glare:
  • Brightness Acuity Tester (BAT): Measures acuity reduction under glare conditions (e.g., posterior subcapsular cataracts).
• Dark Adaptation:
  • Evaluates rod function; prolonged in retinitis pigmentosa, Vitamin A deficiency, or other photoreceptor dystrophies.

⭐ The Amsler grid is a simple, effective tool for patients to self-monitor central visual field changes at home, crucial for early detection or monitoring progression of macular diseases like Age-related Macular Degeneration (AMD).

High-Yield Points - ⚡ Biggest Takeaways

• Low Vision: BCVA <6/18 to >3/60 or visual field <20° (better eye).
• Assessment: History, VA (distance/near), contrast, fields, refraction, functional vision.
• Distance VA: LogMAR charts (ETDRS, Bailey-Lovie) preferred over Snellen.
• Near Vision: Assessed with MNREAD charts for acuity and reading speed.
• Functional Vision: Evaluated using questionnaires (VFQ-25) and observation of ADLs.
• Contrast Sensitivity: Tested with Pelli-Robson or Mars charts; vital for mobility.
• Goal Setting: Patient-centered goals are paramount for successful rehabilitation.