Nyctalopia & retinitis pigmentosa

2. Visual pigment in Rods : Rhodopsin
- glycoprotein and chromophore
[Opsin] [retinal]

- Peak absorption at 500 nm wavelength [blue]
- Most sensitive in dark adapted eye .
- Hence blues and greens will appear
brighter at nightfall - Purkinje effect

4. Intracellular disk
Disk
membrane
Connecting
cilium
outer segment
outer segment
Disk membrane
Intracellular
space
Extracellular
space
Visual
pigment
Visual
pigment
Extracellular
space
Plasma
membrane
Intracellular
space
Connecting
cilium
Rods and Cones
ROD CELL CONE CELL
PHOTORECEPTORS IN THE EYE

5. Physiology of night vision :

Rods are elongated cells [120 million in number ] mainly
confined in the periphery of the retina. These are meant for
Dim vision in low light .
 Rods, are extremely light sensitive and their sensitivity is
about 500 times greater than the sensitivity of cones.
Only a small number of photons is required to stimulate a
rod to send a signal to the brain. Also more number of
pigments than cones .

6. The key to the rod’s ability to convert light
to electric impulses is the Visual pigment
Rhodopsin
Through a complex chain of chemical
changes activated by light ,Rhodopsin
begins the events that activates the
phototransduction cascade

7. Dark adaptation :
When a person shifts from bright to dim
environment 2 processes occur
- Pigment regeneration
- Photochemical changes [Phototransduction]
All this happens in a period of 30 minutes.

8. Nyctalopia :
In greek : Nykt – night , alaos – blindness
Condition in which inability to see in relative dim light.
Causes :
1.Vitamin A deficiency
2.Retinitis pigmentosa
3.Uncorrected refractive error - Myopia
4.Media opacification - cataract
5.Following pan retinal photocoagulation
6.Congenital stationary night blindness
7.Hydroxychloroquine & Phenothiazine
8.Advanced glaucoma

9. Medical history to be sought
Operations [intestinal surgeries]
Liver diseases
Use of medicine :Hydroxychloroquine

Phenothiazine
Hearing status( RP, Usher’s Syndrome, Refsum’s)
Mental retardation( BBS,LMS)
Renal disease (BBS)
Heart disease (KSS, Refsum’s)

11. Introduction:

 Progressive Rod/cone dystrophy
 Hereditary, progressive dystrophies of the
photoreceptors and RPE of Retina
 Otherwise known as pigmental retinal dystrophy.

12.  The condition is abiotrophic in nature and is
genetically determined.
Various inheritance patterns [AD,AR, X linked]
In majority of families it occur as recessive
trait., occasionally it shows dominant hereditary
and even sex linked inheritance.

13. Symptoms :
Patient presents with symptoms which become
apparent between ages of 10 and 30 yrs.
 Night vision problems / prolonged dark adaptation
 Slow progressive loss of vision [peripheral]
 Sparing of central vision
 Ring Scotoma
As the disease develops, people with RP may
often bump into chairs and other objects as side
vision worsens and they only see in one direction
- straight ahead.[Tunnel vision]

15. Signs :
Characteristic fundus changes :

Black bone spicule /Corpuscular retinal pigments
[denser in mid periphery retina ]
Attenuated retinal blood vessels
Waxy type of optic disc atrophy
Cystoid macular edema

17. Associated ocular problems
 Myopia
 Subcapsular cataract
 Open angle glaucoma
 Keratoconus
 Posterior vitreous detachment

18. Atypical RP
Retinitis pigmentosa albescens
Sector RP
Unilteral RP
Pericentric RP

19. VARIANTS
Retinitis pigmentosa sine pigmento: with
same symptoms but without visible retinal
pigmentation.
Retinitis puncta albescens: is an allied
condition with same history and symptoms
but here the retina shows hundreds of small
white dots distributed uniformly over the
whole fundus

21. Systemic findings
Bassen Kornzweig syndrome
Refsum’s syndrome
Kearns Sayre syndrome
Bardet – Biedl syndrome
Usher’s syndrome

22. Diagnosis
Refraction
Direct ophthalmoscopy
 Indirect slit lamp biomicroscopy
Visual field evaluation
 Dark adaptametry
 Electroretinography

23. Treatment
Eminently unsatisfactory since, despite many
claims, nothing appears to have a desired
influence upon the course of the disease.
but there is research that indicates that vitamin A
supplementation and lutein may slow the rate
at which the disease progresses.
 Antioxidants , omega-3 fatty acid, DHA.
 Low phytol and low phytanic acid diet
 Systemic carbonic anhydrase inhibitors like
acetazolamide & Intravitreal triamcinolone

24. Neurotrophic factors
Low vision aids, including telescopic and
magnifying lenses, night vision scopes help people
maximize the vision that they have remaining.
Ultraviolet protective sunglasses
Parental and supportive care
Genetic counselling

26. ARMD
Degenerative anomaly of macula –
exaggeration of normal ageing –Visual
threatening disability
This is one of the leading cause of blindness
in the world. More common >65 years and
in whites and females.
TYPES: 1. Dry or ‘atrophic’ type:
2.Wet or ‘exudative’ type:

27. PATHOGENESIS
Impaired metabolism of RPE
Accumulation of metabolic debris in bruch membrane
Thickening and fragmentation of bruch membrane
with damage
Choroidal neovascularization

28. Hereditary factors, age, nutrition, smoking,
hypertension ,high cholestrol and exposure
to sunlight are risk factors.

29. CLINICAL FEATURES
Gradual painless diminution of vision
Metamorphopsia - distorted vision.
Central scotoma & Paracentral scotoma

30. OPHTHALMOSCOPY
Dry type - Hallmark is drusen and loss of
RPE. Drusen are small yellowish deposits
on bruch’s membrane derived from
metabolic products of visual receptors and
RPE deposited as lipid
Exudative type – Hallmark is CNV
elevated area in neuro sensory retina or
pigment epithelium beneath which abnormal
blood vessels, fluids or haemorrhage are
present.

31. DRY ARMD

32. WET ARMD with haemorage

33. MANAGEMENT
Amsler grid ,preferential hyperacuity tests
Provide micronutrients [zinc & Antioxidants]
Avoid UV light
Life style changes
Laser photocoagulation
Photodynamic therapy
Anti –VEGF
Transpupillary thermotherapy

34. MANAGEMENT
Surgical treatment :
Sub macular surgery
Macular translocation

35. THANK YOU